Updated on 2024/07/14

写真a

 
AKAMATSU, Tomonari
 
Affiliation
Research Council (Research Organization), Research Organization for Nano & Life Innovation
Job title
Senior Researcher(Professor)
Degree
Dr. ( 1996.03 Nihon University )
Mail Address
メールアドレス
Profile

Professor at the Research Organization for Nano & Life Innovation, Waseda University. Ph.D. (Agriculture). Specializes in underwater bioacoustics. Completed master's program of Physics at Tohoku University Graduate School of Science, Ph.D. (Agriculture, Nihon University). Since 1989-2019, he has been a researcher at the Fisheries Research and Education Agency (formerly, Fisheries Research Agency). He was a visiting researcher at the National Institute of Polar Research, and the University of Kentucky's Department of Biological Sciences. He served as a Director of Ocean Policy Research Division and a Senior Researcher at the Sasakawa Peace Foundation during 2020-2024. Specializes in bioacoustics, marine acoustics, and marine mammal studies. Member of the International Organization for Standardization TC43 Technical Committee, member of specialist grounp of cetaceans and sirenians of IUCN, and Environmental Impact Review Advisory Committee member.

Education Background

  • 1987.04
    -
    1989.03

    Tohoku University   Graduate School of Science  

  • 1983.04
    -
    1987.03

    Tohoku University   Faculty of Science   Department of Physics  

  • 1980.04
    -
    1983.03

    静岡県立韮山高校  

Committee Memberships

  • 2021
    -
    Now

    文部科学省「海洋生物ビッグデータ活用技術高度化」事業  外部評価委員会 委員(主査)

  • 2015
    -
    Now

    環境影響審査助言委員

  • 2013
    -
    Now

    IUCN(国際自然保護連合)海牛類専門家委員

  • 2011
    -
    Now

    ISO(国際標準化機構)技術委員会43音響分野委員

  • 2008
    -
    Now

    IUCN(国際自然保護連合)鯨類専門家委員

  • 2022
    -
    2023

    東京海洋大学海洋AIコンソーシアム  運営協議会委員

  • 2022
    -
    2023

    内閣府受託事業「我が国が戦略的に推し進めるべき安全・安心の確保に係る重要技術等の検討業務」  委員

  • 2020
    -
    2022

    国立研究開発法人 水産研究・教育機構  客員研究員

  • 2020
    -
    2021

    日本学術振興会  書面審査委員

  • 2017
    -
     

    科学研究費補助金合議審査委員 基盤C・若手

  • 2016
    -
     

    NEDO洋上風力発電等技術研究開発委員会委員

  • 2015
    -
     

    環境省 洋上風力発電所等に係る環境影響評価の基本的な考え方に関する検討会委員

  • 2014
    -
     

    環境省 平成26年度潮流発電技術実用化推進事業委員会委員

  • 2014
    -
     

    NEDO 海洋洋エネルギー技術研究開発/ 次世代海洋エネルギー発電技術研究開発/ 着定式潮流発電委員会委員

  • 2014
    -
     

    環境省 環境アセスメント調査早期実施実証事業ステアリング委員会

  • 2013
    -
     

    海洋音響学会企画運営委員会委員

  • 2013
    -
     

    科学研究費補助金書面審査委員 基盤・若手

  • 2013
    -
     

    農林水産省が新たに行う競争的資金事業の書類審査専門委員

  • 2013
    -
     

    環境省 個別事業助言委員

  • 2013
    -
     

    浮体式洋上風力発電機設置実証事業 海鳥及び海生生物等の保全検討委員

  • 2013
    -
     

    経済産業省洋上風力発電等技術研究開発委員

  • 2012
    -
     

    文部科学省科学技術政策研究所科学技術動向研究センター専門調査員

  • 2012
    -
     

    環境省風力発電等環境アセスメント基礎情報整備モデル事業検討会委員

  • 2012
    -
     

    環境省風力発電等環境アセスメント先行実施モデル事業検討会委員

  • 2010
    -
     

    海洋研究開発機構海洋工学センター評価助言委員

  • 2010
    -
     

    洋上ウィンドファーム事業性評価手法検討委員

  • 2009
    -
     

    第5回生物ソナー国際シンポジウム組織委員

  • 2006
    -
     

    日米音響学会ジョイントミーティング組織委員

  •  
     
     

    海洋音響学会(理事・企画運営委員)

  •  
     
     

    海産哺乳類学会(Nominations and Elections Committee)

  •  
     
     

    米音響学会 (Technical committee of Animal Bioacoustics)

▼display all

Professional Memberships

  •  
     
     

    米国音響学会

  •  
     
     

    日本動物行動学会

  •  
     
     

    日本水産学会

  •  
     
     

    日本音響学会

  •  
     
     

    海洋音響学会

  •  
     
     

    SMM(海産哺乳類学会)

  •  
     
     

    Acoustical Society of America

  •  
     
     

    Society for Marine Mammalogy

▼display all

Research Areas

  • Aquatic bioproduction science / Ecology and environment

Research Interests

  • ocean policy

  • underwater noise

  • Environmental impact assessment

  • offshore windfarm

  • fish audiology

  • ultrasonic

  • underwater bioacoustics

  • echolocation

  • biosonar

▼display all

Awards

  • 海洋音響学会論文賞

    2015  

  • 日本水産学会進歩賞

    2015  

  • JAMSTEC中西賞

    2009  

  • 日本水産学会論文賞

    2008.03   日本水産学会  

  • 海洋音響学会論文賞

    2001  

 

Papers

  • Increased Yangtze finless porpoise presence in urban Wuhan waters of the Yangtze River during fishing closures

    Zhi Tao Wang, Peng Xiang Duan, Tomonari Akamatsu, Ke Xiong Wang, Ding Wang

    Ecology and Evolution   14 ( 4 )  2024.04

     View Summary

    Wuhan, a highly urbanized and rapidly growing region within China's Yangtze Economic Zone, has historically been identified as a gap area for the critically endangered Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis) based on daytime visual surveys. However, there has been a noticeable increase in porpoise sightings since 2020. This study employed passive acoustic monitoring to investigate porpoise distribution in Wuhan between 2020 and 2022. Generalized linear models were used to explore the relationship between shipping, hydrological patterns, light intensity, and porpoise biosonar activity. Over 603 days of effective monitoring, the daily positive rate for porpoise biosonar detection reached 43%, with feeding-related buzz signals accounting for 55% of all porpoise biosonar signals. However, the proportion of minutes during which porpoise presence was detected was 0.18%, suggesting that while porpoises may frequent the area, their visits were brief and mainly focused on feeding. A significant temporal trend emerged, showing higher porpoise biosonar detection during winter (especially in February) and 2022. Additionally, periods without boat traffic correlated with increased porpoise activity. Hydrological conditions and light levels exhibited significant negative correlations with porpoise activity. Specifically, porpoise sonar detections were notably higher during the night, twilight, and new moon phases. It is highly conceivable that both fishing bans and COVID-19 pandemic-related lockdowns contributed to the heightened presence of porpoises in Wuhan. The rapid development of municipal transportation and shipping in Wuhan and resulting underwater noise pollution have emerged as a significant threat to the local porpoise population. Accordingly, it is imperative for regulatory bodies to effectively address this environmental stressor and formulate targeted protection measures to ensure the conservation of the finless porpoise.

    DOI

    Scopus

    1
    Citation
    (Scopus)
  • Fine-scale spatial variability of marine acoustic environment corresponds with habitat utilization of Indo-Pacific humpback dolphins in Hong Kong waters

    Yuen Wa Ho, Tzu Hao Lin, Tomonari Akamatsu, Leszek Karczmarski

    Ecological Indicators   158  2024.01

     View Summary

    Acoustic properties of the underwater environment are important in maintaining biological processes of various marine organisms. However, with the increasing level of underwater noise in the global ocean, there is a growing need to better understand how marine animals use soundscape cues in their habitat selection. Indo-Pacific humpback dolphins (Sousa chinensis) inhabiting the Pearl River Estuary, southeast China, live in one of world's most developed and noisiest coastal environment and are subjected to many sources of anthropogenic noise. To investigate whether spatial variability of underwater soundscape corresponds with their habitat utilization, we collected daytime underwater recordings in western Hong Kong waters from mid-2016 to mid-2018, and quantified the spatial pattern of marine acoustic environment and its differing characteristics in a fine spatial scale. We developed a framework of soundscape information retrieval to investigate spectral features that may facilitate identification of dolphins’ core habitats. Our findings reveal that a spectral feature, which peaks at 2 kHz, is a reliable predictor of humpback dolphin core habitat. Further modelling of spatial and seasonal variations of underwater soundscape demonstrates that the relative strength of this spectral feature is positively correlated with the sighting rates of humpback dolphins throughout the year. Although the source of the 2 kHz feature remains unknown, it is likely associated with humpback dolphins’ prey. We suggest that underwater acoustic environment represents an important component in evaluating the quality and suitability of coastal habitats for the daily needs of this threatened dolphin species. Local and regional conservation authorities should include habitat-specific baseline soundscape data when developing conservation management strategies.

    DOI

    Scopus

    3
    Citation
    (Scopus)
  • Author Correction: Tidal effects on periodical variations in the occurrence of singing humpback whales in coastal waters of Chichijima Island, Ogasawara, Japan (Scientific Reports, (2022), 12, 1, (19702), 10.1038/s41598-022-24162-0)

    Koki Tsujii, Tomonari Akamatsu, Ryosuke Okamoto, Kyoichi Mori, Yoko Mitani

    Scientific Reports   13 ( 1 )  2023.12

     View Summary

    The original version of this Article contained an error in the Results section, under the subheading ‘Tidal effect on the occurrence of singing whales’, where a citation to Figure 5, instead of a citation to Figure 6, was incorrectly inserted . As a result, “Our model predicted that there was a positive effect on the number of singers during the period from low to high tide, and the effect reached a maximum around 4 h after low tide (Fig. 5).” now reads: “Our model predicted that there was a positive effect on the number of singers during the period from low to high tide, and the effect reached a maximum around 4 h after low tide (Fig. 6).” The original Article has been corrected.

    DOI PubMed

    Scopus

  • Spatiotemporal variations in the acoustic presence of dugongs and vessel traffic around Talibong Island, Thailand: Inputs for local coastal management from passive acoustical aspects

    Kotaro Tanaka, Kotaro Ichikawa, Tomonari Akamatsu, Kongkiat Kittiwattanawong, Nobuaki Arai, Hiromichi Mitamura

    Ocean and Coastal Management   245  2023.11

     View Summary

    Examining the spatiotemporal habitat use by marine megafauna and human activities at a fine scale is important to achieve harmonised management of coastal areas. Passive acoustic monitoring (PAM) can provide this information by observing animal vocalisations and the sounds generated by motorised vessels. Dugongs (Dugong dugon), which are endangered herbivorous mammals inhabiting coastal seas, communicate through social calls. Although their spatiotemporal acoustic presence on a fine scale could assist in prioritizing local marine spatial planning, such knowledge is limited. To address this gap, we examined the spatiotemporal pattern of the acoustic presence of dugongs and its correlation with environmental and anthropological factors; additionally, the overlap of these areas with vessel traffic was illustrated. Underwater recorders were deployed at 11 locations around Talibong Island, Thailand, for one month in both rainy and dry seasons. Based on the recorded sound stream, dugong calls and vessel sounds were automatically detected using custom-made software, and false detections were removed by manual examinations. In 2019 and 2020, 1933 h and 2719 h of recordings, respectively, revealed that while dugongs had a clear spatial preference for vocal communication at some locations, their temporal patterns varied among locations. Further, their acoustic presence was significantly correlated with environmental and anthropological factors at some locations, while these factors varied among other locations. However, the distribution of vessel traffic was spatially and temporally stable. These results suggested that (1) spatial management of vocalisation areas can effectively conserve dugongs by protecting their social behaviour and (2) temporal planning may reduce the potential disturbance risk to dugongs. Moreover, to achieve harmonised marine spatial planning in coastal areas, the PAM approach for social calls can be effectively employed to provide a unique layer of habitat use for vocalising species and vessel traffic on a fine scale.

    DOI

    Scopus

    2
    Citation
    (Scopus)
  • Visualizing the annual transition of ocean policy in Japan using text mining

    Mengyao Zhu, Kotaro Tanaka, Tomonari Akamatsu

    Marine Policy   155  2023.09

     View Summary

    Research on evidence-based marine policymaking is still immature, especially regarding the utilization of text data. This study visualized the transition of ocean policy in Japan using text mining technique applied to the text data of three annual reports: the Fishery white paper from 2007 to 2020, Environmental white paper from 2008 to 2020, and Ocean white paper from 2004 to 2020. The results of the analysis were compared with the expert interviews on each subject. Based on latent Dirichlet allocation (LDA) topic model analysis, significant differences in topics were observed among these white papers, while they all clearly responded to the Great East Japan Earthquake occurred in 2011 with their unique topics. Major transitions in topics occurred several times over the years for all white papers. For the Fishery white paper and Environmental white paper issued by the government agencies, notable transitions occurred in 2011, 2013, 2017 and 2012, 2018, respectively, which were mainly caused by the revisions of relevant laws; while for the Ocean white paper issued by non-government organization, transitions occurred in 2009 and 2016, which were closely related to the development of worldwide ocean initiatives. The expert interviews revealed that the experts’ views on the topics and the transitions of policy focuses were generally consistent with the unsupervised analysis results. Automated visualization of policy transition in each organization accelerates the extraction of their directions and roles in policymaking which will help provide scientific evidence for identifying future opportunities for inter-organizational collaboration.

    DOI

    Scopus

    5
    Citation
    (Scopus)
  • Anthropogenic activity, hydrological regime, and light level jointly influence temporal patterns in biosonar activity of the Yangtze finless porpoise at the junction of the Yangtze River and Poyang Lake, China

    Peng Xiang Duan, Zhi Tao Wang, Tomonari Akamatsu, Nick Tregenza, Guang Yu Li, Ke Xiong Wang, Ding Wang

    Zoological Research   44 ( 5 ) 919 - 931  2023.09

     View Summary

    Under increasing anthropogenic pressure, species with a previously contiguous distribution across their ranges have been reduced to small fragmented populations. The critically endangered Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis), once commonly observed in the Yangtze River-Poyang Lake junction, is now rarely seen in the river-lake corridor. In this study, static passive acoustic monitoring techniques were used to detect the biosonar activities of the Yangtze finless porpoise in this unique corridor. Generalized linear models were used to examine the correlation between these activities and anthropogenic impacts from the COVID-19 pandemic lockdown and boat navigation, as well as environmental variables, including hydrological conditions and light levels. Over approximately three consecutive years of monitoring (2020 2022), porpoise biosonar was detected during 93% of logged days, indicating the key role of the corridor for finless porpoise conservation. In addition, porpoise clicks were recorded in 3.80% of minutes, while feeding correlated buzzes were detected in 1.23% of minutes, suggesting the potential existence of localized, small-scale migration. Furthermore, both anthropogenic and environmental variables were significantly correlated with the diel, lunar, monthly, seasonal, and annual variations in porpoise biosonar activities. During the pandemic lockdown period, porpoise sonar detection showed a significant increase. Furthermore, a significant negative correlation was identified between the detection of porpoise click trains and buzzes and boat traffic intensity. In addition to water level and flux, daylight and moonlight exhibited significant correlations with porpoise biosonar activities, with markedly higher detections at night and quarter moon periods. Ensuring the spatiotemporal reduction of anthropogenic activities, implementing vessel speed restrictions (e.g., during porpoise migration and feeding), and maintaining local natural hydrological regimes are critical factors for sustaining porpoise population viability.

    DOI PubMed

    Scopus

    3
    Citation
    (Scopus)
  • Statistical analysis of measured underwater radiated noise from merchant ships using ship operational and design parameters

    Masahiro Sakai, Reo Haga, Toshio Tsuchiya, Tomonari Akamatsu, Naoya Umeda

    The Journal of the Acoustical Society of America   154 ( 2 ) 1095 - 1105  2023.08

     View Summary

    Ships unintentionally radiate underwater noise mainly due to propeller cavitation under usual operations. In 2022, the International Maritime Organization started a review of the nonmandatory guidelines for the reduction of underwater radiated noise (URN) from ships. The characteristics of URN from ships have been studied for a long time, and quantitative variations in URN levels with ship size and speed have been reported. From the viewpoint of ship design, it is more reasonable that the effect of ship speed and draft is considered as the ratio to design speed and maximum draft, respectively. Therefore, in this study, underwater sound measurements were conducted in deep water (>300 m in depth) under a sea lane, and regression analysis was applied to the source levels of the URN from many merchant ships using ship length, ship speed ratio to design speed, and draft ratio to maximum draft. In this analysis, the source level is simplified based on the characteristics of URN due to propeller cavitation. This allows one coefficient to represent the approximate shape of the spectrum of URN level. Further, variations in the URN level for each ship type are discussed based on the results and comparisons with previous studies.

    DOI PubMed

    Scopus

    1
    Citation
    (Scopus)
  • Using Soundscapes to Assess Changes in Coral Reef Social-Ecological Systems

    Tzu Hao Lin, Frederic Sinniger, Saki Harii, Tomonari Akamatsu

    Oceanography   36 ( 1 ) 20 - 27  2023.03

    DOI

    Scopus

    2
    Citation
    (Scopus)
  • Sound properties produced by white-edged rockfish (Sebastes taczanowskii) in relation to body and swim bladder size

    Naoto Matsubara, Seiji Katakura, Ryuzo Takahashi, Tomonari Akamatsu, Hiroki Yasuma

    JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA   153 ( 3 ) 1703 - 1709  2023.03

     View Summary

    The sound properties produced by the white-edged rockfish (Sebastes taczanowskii Steindachner, 1880) were compared with the body size. We conducted a tank experiment to compare the sound properties with body length, which ranged from 12.4 to 19.8 cm. Sound production was composed of pulses with a duration of 0.010-0.022 s and a peak frequency of 400-1000 Hz. Peak frequency decreased with fish and swim bladder size and pulse duration. The relationship between sound properties and body size may be useful for estimating the body length of the target species by using passive acoustic monitoring.

    DOI PubMed

    Scopus

    2
    Citation
    (Scopus)
  • Marine invertebrates and noise

    Marta Solé, Kenzo Kaifu, T. Aran Mooney, Sophie L. Nedelec, Frédéric Olivier, Andrew N. Radford, Mirella Vazzana, Matthew A. Wale, Jayson M. Semmens, Stephen D. Simpson, Giuseppa Buscaino, Anthony Hawkins, Natacha Aguilar de Soto, Tomoari Akamatsu, Laurent Chauvaud, Ryan D. Day, Quinn Fitzgibbon, Robert D. McCauley, Michel André

    Frontiers in Marine Science   10  2023

     View Summary

    Within the set of risk factors that compromise the conservation of marine biodiversity, one of the least understood concerns is the noise produced by human operations at sea and from land. Many aspects of how noise and other forms of energy may impact the natural balance of the oceans are still unstudied. Substantial attention has been devoted in the last decades to determine the sensitivity to noise of marine mammals—especially cetaceans and pinnipeds—and fish because they are known to possess hearing organs. Recent studies have revealed that a wide diversity of invertebrates are also sensitive to sounds, especially via sensory organs whose original function is to allow maintaining equilibrium in the water column and to sense gravity. Marine invertebrates not only represent the largest proportion of marine biomass and are indicators of ocean health but many species also have important socio-economic values. This review presents the current scientific knowledge on invertebrate bioacoustics (sound production, reception, sensitivity), as well as on how marine invertebrates are affected by anthropogenic noises. It also critically revisits the literature to identify gaps that will frame future research investigating the tolerance to noise of marine ecosystems.

    DOI

    Scopus

    29
    Citation
    (Scopus)
  • Development of edge computing underwater sound recorder to monitor deep sea soundscape

    Masaya Katagiri, Shinsuke Kawagucci, Hiromi Kayama Watanabe, Kotaro Tanaka, Tomonari Akamatsu

    2023 IEEE International Symposium on Underwater Technology, UT 2023    2023

     View Summary

    Sound propagates at a greater range than light in marine environments. Anthropogenic sound and noise pollution caused by deep sea mining and offshore wind farms are increasing, which may affect the marine ecosystem. However, sound datasets in oceanic environments are quite limited. In this paper, we summarize the requirements of a deep sea soundscape monitoring device by reviewing currently available instruments, and we propose a cost-effective and noise reductive recording system to the monitor marine soundscape to identify temporal variations in the soundscape at various scales. The development of this system is ongoing, and we summarize the results of two trial deployments in a huge aquarium tank and off the pier of a marine station. The results demonstrate that the noise generated and the battery consumption of the proposed system are comparable to conventional systems. However, the proposed system is highly versatile due to the scalability of the IDE of the system's software. Our work to develop a cost-effective, noise-reductant and long-term recording system will contribute to the acquisition of soundscape data in marine environments, which is expected to enable the identification of baseline sound properties in various marine environments and reconstruct temporal and spatial variations of marine biodiversity and ecosystem dynamics.

    DOI

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  • Underwater sound observation using the Edokko Mark i as a platform of acoustic environment assessment for marine mineral resource development

    Yosuke Onishi, Hajime Naganuma, Yuya Yamamoto, Masayuki Nagao, Naoki Saito, Atsushi Suzuki, Kyohei Takami, Mitsuru Shimazu, Tomonari Akamatsu

    2023 IEEE International Symposium on Underwater Technology, UT 2023    2023

     View Summary

    group have developed an underwater sound recording device capable of observing underwater sound for approximately one year at a depth of 6,000 meters. We installed this device on the underwater explorer "Edokko Mark I (Type 365),"and obtained intermittent recording for about one year at the research station LE4, located about 160 km offshore south of Minami-Torishima Island, Japan, where marine mineral resources exist. In this study, we report on the newly developed underwater sound recording device and the results of the soundscape analysis.

    DOI

    Scopus

    1
    Citation
    (Scopus)
  • Tidal effects on periodical variations in the occurrence of singing humpback whales in coastal waters of Chichijima Island, Ogasawara, Japan

    Koki Tsujii, Tomonari Akamatsu, Ryosuke Okamoto, Kyoichi Mori, Yoko Mitani

    Scientific Reports   12 ( 1 )  2022.11

     View Summary

    Abstract

    Marine organisms inhabiting coastal waters are known to be driven by periodic cycles such as diel, tidal, and seasonal changes. Humpback whales (Megaptera novaeangliae) breed in shallow and warm coastal waters, with males singing complex songs during the breeding season. To investigate periodic variations in humpback whale singing activities, we conducted fixed passive acoustic monitoring in the Ogasawara (Bonin) Islands, Japan, from winter to spring during 2016–2018. The singing activity and individual number of singers were observed throughout the day and night using a very long baseline passive acoustic array. The occurrence of singers peaked before sunrise and in the evening and was reduced during the daytime. The frequency of song reception depended on the tidal phase. A generalised additive model demonstrated that the occurrence of singers increased during the flood tide and decreased during the ebb tide in the waters west of Chichijima Island. These results suggest that the singing behaviour of humpback whales in breeding areas is affected by the diel and tidal cycles. Male humpback whales may change their behaviour or singing location depending on the strength and direction of the tidal current, considering that the selection of a stable location is beneficial for singing whales.

    DOI PubMed

    Scopus

    1
    Citation
    (Scopus)
  • Vocalization of Bryde's whales (Balaenoptera edeni) in the Beibu Gulf, China

    Zhi Tao Wang, Peng Xiang Duan, Mo Chen, Zhi Gang Mei, Xiao Dong Sun, Zhi Wen Nong, Mei Han Liu, Tomonari Akamatsu, Ke Xiong Wang, Ding Wang

    Marine Mammal Science   38 ( 3 ) 1118 - 1139  2022.07

     View Summary

    The presence of Bryde's whales (Balaenoptera edeni) in the Beibu Gulf, China has been reported since 2016. In the current study, in situ Bryde's whale vocalizations were recorded. Bouts of frequency modulated repetitive and diversified calls were recorded. Repetitive calls were recorded when 1–3 whales were present within 2 km of the boat and were probably emitted by a single whale and functioned as contact calls. Repetitive calls were divided into biphonation downswept tonals and downswept tonals. Diversified calls were recorded when 4–7 whales were present within 2 km of the boat and were probably associated with acoustic exchanges between or among conspecifics. Diversified calls occasionally contained inflection points, frequency jumps, and break point features. The frequency band of Bryde's whale vocalizations overlapped highly with background noise. Most vocalizations in the current study were different than those previously reported for this species. Therefore, the findings of this study provide more information on the known acoustic repertoire of Bryde's whales and provide a basis for noninvasive monitoring of Bryde's whale with passive acoustic methods and for developing mitigation and conservation protocols to ensure their future viability.

    DOI

    Scopus

    9
    Citation
    (Scopus)
  • Spatial distribution maps of real-time ocean observation platforms and sensors in Japanese waters

    Kotaro Tanaka, Mengyao Zhu, Kohei Miyaji, Tadayuki Kurokawa, Tomonari Akamatsu

    Marine Policy   141  2022.07

     View Summary

    Ocean observations are required to provide timely evidence of facts about the ocean in order to evaluate the sustainable management of biodiversity, climate change, fisheries, mineral resources, tourism, and any other anthropogenic activities that support blue economy policymaking. In Japan, this is particularly crucial given that it is an islandic country stretching from north to south, thereby having a diverse coastal environment. Although tremendous efforts towards ocean observations have been made, coordination among sectors is not always sufficient, which prevented availing the comprehensive capacity of ocean observation. In this study, the existing observation platforms and installed sensors, particularly fixed platforms that enable real-time data transmission, were reviewed, and the spatial distribution of them was investigated. It was confirmed that a large number of observation networks cover Japanese waters; however, many of those platforms were used for single purpose, and the spatial coverage was still considerably limited for some sensors, such as salinity, dissolved oxygen, and chlorophyll a. It must be noted that this study intentionally limited the data sources of platforms/sensors to the disclosed data on public reports and/or websites, in order to raise a discussion about information disclosure of observation efforts, conducted by numerous stakeholders. Based on this information, we recommend extending the capacity of ocean observation by utilizing existing platforms rather than constructing new platforms, in order to enhance cost-effectiveness.

    DOI

    Scopus

    2
    Citation
    (Scopus)
  • エゾメバル(Sebastes taczanowskii)の嗚音の音響特性—Properties of Fish Sound by White-edged Rockfish (Sebastes taczanowskii)

    松原 直人, 齋藤 伶, 赤松 友成, 高橋 竜三, 安間 洋樹

    海洋音響学会誌 = The journal of the Marine Acoustics Society of Japan   49 ( 3 ) 96 - 102  2022.07

  • Auditory evoked potential in stranded melon-headed whales (Peponocephala electra): With severe hearing loss and possibly caused by anthropogenic noise pollution

    Zhi Tao Wang, Alexander Ya Supin, Tomonari Akamatsu, Peng Xiang Duan, Yi Ning Yang, Ke Xiong Wang, Ding Wang

    Ecotoxicology and Environmental Safety   228  2021.12

     View Summary

    Highly concentrated live mass stranding events of dolphins and whales happened in the eastern coast of China between June and October 2021. The current study adopted the non-invasive auditory evoked-potential technique to investigate the hearing threshold of a stranded melon headed whale (Peponocephala electra) at a frequency range of between 9.5 and 181 kHz. It was found that, at the frequency range of from 10 to 100 kHz, hearing thresholds for the animal were between 20 and 65 dB higher than those of its phylogenetically closest species (Pygmy killer whale). The severe hearing loss in the melon headed whale was probably caused by transient intense anthropogenic sonar or chronic shipping noise exposures. The hearing loss could have been the cause for the observed temporal and spatial clustered stranding events. Therefore, there is need for noise mitigation strategies to reduce noise exposure levels for marine mammals in the coastal areas of China.

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  • Riverside underwater noise pollution threaten porpoises and fish along the middle and lower reaches of the Yangtze River, China

    Zhi Tao Wang, Peng Xiang Duan, Tomonari Akamatsu, Yu Wei Chen, Xue An, Jing Yuan, Pei Yu Lei, Jiao Li, Lu Zhou, Ming Chao Liu, Yi Ning Yang, Fei Fan, Ke Xiong Wang, Ding Wang

    Ecotoxicology and Environmental Safety   226  2021.12

     View Summary

    The Yangtze River exhibits a high biodiversity and plays an important role in global biodiversity conservation. As the world's busiest inland river in regard to shipping, little attention has been paid to underwater noise pollution. In 2017, the underwater noise level in 25 riverside locations along the middle and lower reaches of the Yangtze River mainly at night time were investigated by using passive acoustic monitoring method. Approximately 88% and 40% of the sampled sites exhibit noise levels exceeding the underwater acoustic thresholds of causing responsiveness and temporary threshold shift, respectively, in cetacean. Noise pollution may impose a high impact on fish with physostomous swim bladders and Weberian ossicles, such as silver carp, bighead carp, goldfish and common carp, whereas it may affect fish with physoclistous swim bladders and without Weberian ossicles, such as lake sturgeon and paddlefish, to a lesser extent. Noise levels reductions of approximately 10 and 20 dB were observed in the middle and lower reaches, respectively, of the Yangtze River over the 2012 level. The green development mode of the ongoing construction of green shipping in the Yangtze River Economic Belt, including the development of green shipping lanes, ports, ships and transportation organizations, may account for the alleviated underwater noise pollution. Follow-up noise mitigation endeavors, such as the extension of ship speed restrictions and the study and implementation of the optimal navigation speed in ecologically important areas, are required to further reduce the noise level in the Yangtze River to protect local porpoises and fish.

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    17
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  • Annual variation of oceanographic conditions changed migration timing of bowhead whales Balaena mysticetus in the southern Chukchi Sea

    Koki Tsujii, Mayuko Otsuki, Tomonari Akamatsu, Kazuo Amakasu, Minoru Kitamura, Takashi Kikuchi, Amane Fujiwara, Hokuto Shirakawa, Kazushi Miyashita, Yoko Mitani

    POLAR BIOLOGY   44 ( 12 ) 2289 - 2298  2021.12

     View Summary

    The Chukchi Sea environment changes considerably in physical and biological conditions, driven by the expanding volume of warm Pacific summer water. These environmental changes can affect the migration timing of baleen whales in the southern Chukchi Sea. However, few studies have been conducted in this area to determine the migration timing of bowhead whales (Balaena mysticetus), the only baleen whale species endemic to the Arctic region. In this study, we conducted a fixed passive acoustic monitoring of bowhead whales in the southern Chukchi Sea from July 2012 to October 2015 and compared the occurrence patterns of vocalizations to physical and biological environmental factors. Bowhead whale calls were detected in fall/winter and spring during the ice-freezing and retreating periods, respectively. The fall migration timing of bowhead whales through the southern Chukchi Sea was delayed in the years when the timing of sea ice formation was late, and it formed increasingly later in the years 2013, 2014, and 2012, in that sequence. Moreover, the sea surface temperature decreased before freeze-up, which affected the timing of fall migration of bowhead whales. There was no clear relationship between the occurrence of bowhead whale calls and the abundance of prey, especially in spring, suggesting that most bowhead whales use the southern Chukchi Sea as a corridor during their spring northward migrations. However, the occurrence of bowhead whales and high abundance of zooplankton in October-November present the possibility that bowhead whales expand their feeding area in the southern Chukchi Sea.

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    8
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  • Baseline soundscapes of deep‐sea habitats reveal heterogeneity among ecosystems and sensitivity to anthropogenic impacts

    Chong Chen, Tzu‐Hao Lin, Hiromi Kayama Watanabe, Tomonari Akamatsu, Shinsuke Kawagucci

    Limnology and Oceanography   66 ( 10 ) 3714 - 3727  2021.10

     View Summary

    Underwater soundscapes, though invisible, are crucial in shaping the biodiversity of marine ecosystems by acting as habitat-specific settlement cues for larvae. The deep sea has received little attention in soundscape research, but it is being targeted for mineral extraction to feed the ever-growing needs of our society. Anthropogenic impacts on soundscapes influence the resilience of key shallow-water habitats, and the same likely applies to the deep. Japan is a forerunner in deep-sea mining, but virtually no deep soundscape baselines exist for Japanese waters. Here, we report baseline soundscapes from four deep-sea locations in Japan, including the Suiyo Seamount hydrothermal vent, the abyssal plain around the Minamitorishima Island home to manganese nodule fields and muds rich in rare-earth elements, twilight depths off Sanriku, as well as a typical bathyal system in Suruga Bay. Long-duration audio recordings were visualized and factorized by an unsupervised machine learning model, revealing differing characteristics among the habitats. Two locations near the coast are highly influenced by shipping noise. The Suiyo vent is characterized by low-frequency sounds from venting, and the abyssal Minamitorishima is quiet with a flat spectral shape. Noise from observation platforms is likely sufficient to alter soundscape characteristics, especially in offshore locations, suggesting offshore mining-targeted areas are susceptible to impacts from anthropogenic noise. We argue that the monitoring of soundscapes is an indispensable component for assessing potential mining impacts on deep-sea ecosystems. Our results establish reference points for future soundscape monitoring and assessment in Japanese waters as well as similar ecosystems globally.

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    9
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  • Seasonal and diel changes in cetacean vocalizations monitored by passive acoustic methods in Nemuro Strait adjacent to the Shiretoko World Natural Heritage Site

    Mayuko Otsuki, Tomonari Akamatsu, Takahiro Nobetsu, Yoko Mitani

    MARINE MAMMAL SCIENCE   37 ( 4 ) 1330 - 1340  2021.10

     View Summary

    UNESCO World Natural Heritage sites are established to ensure the long-term conservation of natural areas. Nemuro Strait in northern Japan is adjacent to the Shiretoko World Natural Heritage Site, and attracts various trophic levels of marine species, including marine mammals. Although the coexistence of humans and marine mammals is an important issue in this area, the temporal habitat use of cetaceans in this area is unknown. Here, we document seasonal and diel changes in cetacean vocalizations collected using passive acoustic recording devices during November 2012-March 2014. Killer whale calls occurred in spring and summer, and sperm whale clicks were detected in summer. Pacific white-sided dolphin calls were recorded in summer and late fall. No cetaceans were recorded during the sea ice period in February and March. The dolphin calls and unknown click trains were significantly more frequent at night. In contrast, marginal diel changes in killer whale calls were detected. Our results suggest that the majority of cetaceans utilize Nemuro Strait at night during the ice-free period, and we provide new insights into the habitat use and diversity of marine mammals in the Strait.

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  • Coastal development threatens Datan area supporting greatest fish diversity at Taoyuan Algal Reef, northwestern Taiwan

    Joseph Heard, Wei Chen Tung, Yu De Pei, Tzu Hao Lin, Chien Hsiang Lin, Tomonari Akamatsu, Colin K.C. Wen

    Aquatic Conservation: Marine and Freshwater Ecosystems   31 ( 3 ) 590 - 604  2021.03

     View Summary

    Taoyuan Algal Reef is a biodiverse coralline algal reef in north-west Taiwan, that is currently threatened by coastal development and industrial waste runoff. As the reef lies in an exposed area that is frequently disturbed by monsoons, it is difficult to survey using traditional methods. Knowledge of the reef is therefore limited, and has until recently, long been regarded as a barren environment. However, recent studies have revealed that the reef is inhabited by a diverse array of organisms, particularly at Datan, where a natural gas receiving terminal is planned for construction. Due to challenging environmental conditions, otolith assemblage and soundscape analyses were used to supplement traditional sampling methods including clove oil, netting, and pole-and-line fishing in order to assess the diversity of the fish community at Taoyuan Algal Reef. Several fish species that had not been recorded by previous surveys were observed. Fish diversity and the average size of commercially targeted species were greatest at Datan G2. Predatory reef fishes such as groupers (Serranidae) and snappers (Lutjanidae), as well as several small endangered scalloped hammerhead sharks Sphyrna lewini were recorded at G2, where otolith assemblage analysis also indicated increased predatory activity. However, fewer individuals and species were recorded from tidal pools across all sites compared to previous surveys, suggesting a loss of biodiversity. If construction work resumes at Datan, it will be likely to have adverse consequences for the reef itself, the species that inhabit it, and by extension, the local fishermen that rely upon it. Halting additional coastal development, reducing industrial and domestic pollution, as well as improving the management of traditional fisheries is recommended to protect this unique reef ecosystem from further degradation.

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    10
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  • Sensing ecosystem dynamics via audio source separation: A case study of marine soundscapes off northeastern Taiwan

    Tzu Hao Lin, Tomonari Akamatsu, Yu Tsao

    PLoS Computational Biology   17 ( 2 )  2021.02

     View Summary

    Remote acquisition of information on ecosystem dynamics is essential for conservation management, especially for the deep ocean. Soundscape offers unique opportunities to study the behavior of soniferous marine animals and their interactions with various noise-generating activities at a fine temporal resolution. However, the retrieval of soundscape information remains challenging owing to limitations in audio analysis techniques that are effective in the face of highly variable interfering sources. This study investigated the application of a seafloor acoustic observatory as a long-term platform for observing marine ecosystem dynamics through audio source separation. A source separation model based on the assumption of source-specific periodicity was used to factorize time-frequency representations of long-duration underwater recordings. With minimal supervision, the model learned to discriminate source-specific spectral features and prove to be effective in the separation of sounds made by cetaceans, soniferous fish, and abiotic sources from the deep-water soundscapes off northeastern Taiwan. Results revealed phenological differences among the sound sources and identified diurnal and seasonal interactions between cetaceans and soniferous fish. The application of clustering to source separation results generated a database featuring the diversity of soundscapes and revealed a compositional shift in clusters of cetacean vocalizations and fish choruses during diurnal and seasonal cycles. The source separation model enables the transformation of single-channel audio into multiple channels encoding the dynamics of biophony, geophony, and anthropophony, which are essential for characterizing the community of soniferous animals, quality of acoustic habitat, and their interactions. Our results demonstrated the application of source separation could facilitate acoustic diversity assessment, which is a crucial task in soundscape-based ecosystem monitoring. Future implementation of soundscape information retrieval in long-term marine observation networks will lead to the use of soundscapes as a new tool for conservation management in an increasingly noisy ocean.

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  • Foraging activity of harbour porpoises around a bottom-gillnet in a coastal fishing ground, under the risk of bycatch

    Maeda Saki, Sakurai Kenji, Akamatsu Tomonari, Matsuda Ayaka, Yamamura Orio, Kobayashi Mari, Matsuishi Takashi Fritz

    PLOS ONE   16 ( 2 ) e0246838  2021.02  [Refereed]  [International journal]

     View Summary

    Bycatch of harbour porpoises (Phocoena phocoena) by gillnets is a recognised threat to populations. To develop effective mitigation measures, understanding the mechanics of bycatch is essential. Previous studies in experimental conditions suggested foraging activity is an important factor influencing porpoises' reaction to gillnets. We acoustically observed the behaviour of wild harbour porpoises around a bottom-gillnet set-up in a commercial fishing ground, especially foraging activity. Passive acoustic event recorders (A-tags) were fixed to the ends of the gillnet, and recorded for 1 392 hours. Although harbour porpoises frequently and repeatedly appeared around the net each day, incidental bycatch occurred only three times during the observations. The stomach contents of two individuals contained mainly Ammodytes sp., which were observable around the bottom-gillnet but not targeted by the fishery. A total of 276 foraging incidents were acoustically detected, and 78.2% of the foraging activity was in the bottom layer (deeper than 25 m). Porpoises appeared around the net with more frequency on the day of a bycatch incident than on the days without bycatch. These results suggest that the harbour porpoises appeared around the bottom-gillnet to forage on fish distributed in the fishing ground, but not captured by this bottom-gillnet. Thus, porpoises face the risk of becoming entangled when foraging near a gillnet, with the probability of bycatch simply increasing with the length of time spent near the net. Bycatch mitigation measures are discussed.

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  • Exploring coral reef biodiversity via underwater soundscapes

    Tzu-Hao Lin, Tomonari Akamatsu, Frederic Sinniger, Saki Harii

    Biological Conservation Volume   253   108901  2021.01  [Refereed]

     View Summary

    Information on biodiversity is essential to evaluate the ecological status of coral reefs. Sounds produced by reef-associated organisms have been used as a biodiversity indicator. However, the interference from abiotic sounds and the lack of a comprehensive audio library have impeded effective evaluation. This study investigated the application of underwater soundscapes as a remote-sensing method to detect biological and anthropogenic activities. Using techniques including the visualization of long-duration recordings, source separation, and clustering, soundscapes were separated into sounds of anthropogenic and biological sources. Our results revealed the dynamics of biological sounds among coral reefs off Sesoko Island, Okinawa, Japan. Biological sounds were much more prominent in shallow-water reefs than in upper-mesophotic reefs, but their spectral features and compositions differed. The shallow-water reefs were dominated by broadband sounds of crustaceans and low-frequency transient fish calls, whereas the upper-mesophotic reefs were characterized by a diverse array of fish choruses and transient sounds. We also discovered that shipping noise heavily interfered with the soundscapes from the upper-mesophotic reefs and represented an invisible threat to life in the low-light habitat. The applied techniques of soundscape information retrieval revealed the distinct ecological status of coral reefs and the behavior change of sound-producing organisms in high temporal resolution. Implementation of soundscape monitoring can generate ecological information on habitat quality, reef biodiversity, human activities, and their interactions. Global collaboration on underwater soundscapes will establish a data-informed platform and help stakeholders assess the resilience of coral reefs to environmental and anthropogenic stressors.

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    21
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  • Automatic detection of dolphin whistles and clicks based on entropy approach

    Shashidhar Siddagangaiah, Chi Fang Chen, Wei Chun Hu, Tomonari Akamatsu, Megan McElligott, Marc O. Lammers, Nadia Pieretti

    Ecological Indicators   117  2020.10

     View Summary

    Long-term monitoring of cetacean vocalizations allows for the exploration of their occurrence, seasonality and abundance. However, accurate automatic detection of vocalizations from vast acoustic datasets containing diverse sound sources remains a challenge. In this study, we propose the permutation entropy (H) and the sample entropy (SE) as metrics for the unattended detection of whistles and clicks. We tested the detection performance of whistles and clicks in various scenarios commonly occurring in marine habitats, including dense snapping shrimps, vessel engine noise and overlapping whistles and clicks. The use of the entropy metrics resulted in detection accuracy of over 95%. In particular, H outcomes correctly detected whistles even if associated with snapping shrimps or engine noise, while SE was a reliable indicator for clicks and robust to vessel noise. These algorithms do not require prior training in vocalization and are computationally fast. The advancement of metrics such as those presented here, will enable non-invasive and cost-effective assessment of cetacean population dynamics and health and may inform future conservation management.

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    16
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  • Passive acoustic monitoring of the distribution patterns of Irrawaddy dolphins (Orcaella brevirostris) in the middle reaches of the Ayeyarwady River, Myanmar

    Zhi Tao Wang, Peng Xiang Duan, Tomonari Akamatsu, Ke Xiong Wang, Ding Wang

    Marine Mammal Science   36 ( 4 ) 1241 - 1253  2020.10

     View Summary

    The Irrawaddy dolphins (Orcaella brevirostris) are an endangered species. Thus, up-to-date information on the distribution pattern of dolphins is critical for its proper management and conservation. Using a towed passive acoustic monitoring device, the distribution pattern of the Irrawaddy dolphins in the middle reaches of the Ayeyarwady River, Myanmar, was investigated during a vessel-based survey between Mingun and Katha. This region was successively divided into segments 1–4 from upstream to downstream. Sixteen echolocation encounters, with a series of click trains separated by <8 min and 26 dolphin acoustic trajectories were recorded. The mean dolphin detection rate (animals/kilometer) across the four segments progressively increased from upstream to downstream. High relative abundance was observed in segment 4 (46%) and segment 1 (23%) which was consistent with findings from historical boat-based visual surveys. The averaged interclick intervals of each click train in segment 2 and 4 was significantly shorter than that in segment 3, indicating that the dolphins in these segments frequently use shorter-ranged biosonar. More frequent and consistent surveys with a systematic sampling track design that incorporates other factors and covering the whole distribution range along the Ayeyarwady River and at varied water levels are needed in the future.

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  • Underwater noise pollution in China's Yangtze River critically endangers Yangtze finless porpoises (Neophocaena asiaeorientalis asiaeorientalis).

    Zhi-Tao Wang, Tomonari Akamatsu, Peng-Xiang Duan, Lu Zhou, Jing Yuan, Jiao Li, Pei-Yu Lei, Yu-Wei Chen, Yi-Ning Yang, Ke-Xiong Wang, Ding Wang

    Environmental pollution (Barking, Essex : 1987)   262   114310 - 114310  2020.07  [International journal]

     View Summary

    Underwater sound plays an important role in some critical life functions of many aquatic animals. Underwater noise pollution has received relatively more attention in ocean systems. However, little attention has been paid to freshwater systems, such as the Yangtze River which is the habitat of critically endangered Yangtze finless porpoises (Neophocaena asiaeorientalis asiaeorientalis). In 2012, the underwater noise levels in 25 sites along the middle and lower sections of the Yangtze River were measured. The root mean square sound pressure level (SPL) and unweighted sound exposure level (SEL) at each site ranged between 105 ± 2.4 (median ± quartile deviation) and 150 ± 5.5 dB. Obvious spatial and temporal variations in the SPL were detected among the 25 sites. The SPL and SEL in the middle section of the Yangtze River were smaller (approximately 15 dB) and fluctuated more compared to those in the lower section. The power spectrum in the mainstem was site specific. However, all the spectra levels were higher than the audiogram of Yangtze finless porpoises. Majority of the sites had an averaged cumulative unweighted SEL (72%) and cumulative weighted SEL (68%) that surpassed the underwater acoustic thresholds for onset of hearing temporal threshold shifts for finless porpoise. Porpoise bio-sonars were detected in 89% of sonar monitoring sites indicating that noise pollution in the Yangtze River greatly threatened porpoise survival. In 8% of the sites, the averaged cumulative weighted SEL exceeded that of underwater acoustic thresholds causing non-recoverable permanent threshold shifts of finless porpoises auditory system whereas it was less than 1 dB below the underwater acoustic thresholds in other 8% of the sites. These sites urgently needed noise mitigation and management strategies. These results will facilitate the evaluation of the impacts of anthropogenic noise pollution on local finless porpoises and give further guidelines on its effective conservation.

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  • Evoked-potential audiogram variability in a group of wild Yangtze finless porpoises (Neophocaena asiaeorientalis asiaeorientalis).

    Zhi-Tao Wang, Jiao Li, Peng-Xiang Duan, Zhi-Gang Mei, Fu-Qiang Niu, Tomonari Akamatsu, Pei-Yu Lei, Lu Zhou, Jing Yuan, Yu-Wei Chen, Alexander Ya Supin, Ding Wang, Ke-Xiong Wang

    Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology   206 ( 4 ) 527 - 541  2020.07  [International journal]

     View Summary

    Hearing is considered the primary sensory modality of cetaceans and enables their vital life functions. Information on the hearing sensitivity variability within a species obtained in a biologically relevant wild context is fundamental to evaluating potential noise impact and population-relevant management. Here, non-invasive auditory evoked-potential methods were adopted to describe the audiograms (11.2-152 kHz) of a group of four wild Yangtze finless porpoises (Neophocaena asiaeorientalis asiaeorientalis) during a capture-and-release health assessment project in Poyang Lake, China. All audiograms presented a U shape, generally similar to those of other delphinids and phocoenids. The lowest auditory threshold (51-55 dB re 1 µPa) was identified at a test frequency of 76 kHz, which was higher than that observed in aquarium porpoises (54 kHz). The good hearing range (within 20 dB of the best hearing sensitivity) was from approximately 20 to 145 kHz, and the low- and high-frequency hearing cut-offs (threshold > 120 dB re l μPa) were 5.6 and 170 kHz, respectively. Compared with aquarium porpoises, wild porpoises have significantly better hearing sensitivity at 32 and 76 kHz and worse sensitivity at 54, 108 and 140 kHz. The audiograms of this group can provide a basis for better understanding the potential impact of anthropogenic noise.

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    15
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  • Using Soundscapes to Assess Deep-Sea Benthic Ecosystems.

    Tzu-Hao Lin, Chong Chen, Hiromi Kayama Watanabe, Shinsuke Kawagucci, Hiroyuki Yamamoto, Tomonari Akamatsu

    Trends in ecology & evolution   34 ( 12 ) 1066 - 1069  2019.12  [International journal]

     View Summary

    Targets of deep-sea mining commonly coincide with biodiversity hotspots, such as hydrothermal vents. The resilience of these ecosystems relies on larval dispersal, which may be directed by habitat-specific soundscapes. We urge for a global effort to implement soundscape as a conservation tool to assess anthropogenic disruption to deep-sea benthic ecosystems.

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  • Soundscape of an Indo-Pacific humpback dolphin (Sousa chinensis) hotspot before windfarm construction in the Pearl River Estuary, China: Do dolphin engage in noise avoidance and passive eavesdropping behavior?

    Zhi-Tao Wang, Tomonari Akamatsu, Douglas P Nowacek, Jing Yuan, Lu Zhou, Pei-Yu Lei, Jiao Li, Peng-Xiang Duan, Ke-Xiong Wang, Ding Wang

    Marine pollution bulletin   140   509 - 522  2019.03  [International journal]

     View Summary

    Soundscapes are vital to acoustically specialized animals. Using passive acoustic monitoring data, the temporal and spectral variations in the soundscape of a Chinese white dolphin hotspot were analyzed. By cluster analysis, the 1/3 octave band power spectrum can be grouped into three bands with median overall contribution rates of 35.24, 14.14 and 30.61%. Significant diel and tidal soundscape variations were observed with a generalized linear model. Temporal patterns and frequency ranges of middle frequency band sound matched well with those of fish vocalization, indicating that fish might serve as a signal source. Dolphin sounds were mainly detected in periods involving low levels of ambient sound and without fish vocalization, which could reflect noise avoidance and passive eavesdropping behaviors engaged in by the predator. Pre-construction data can be used to assess the effects of offshore windfarms on acoustic environments and aquatic animals by comparing them with the soundscape of postconstruction and/or postmitigation.

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    22
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  • Leave or stay? Video-logger revealed foraging efficiency of humpback whales under temporal change in prey density.

    Yu Akiyama, Tomonari Akamatsu, Marianne H Rasmussen, Maria R Iversen, Takashi Iwata, Yusuke Goto, Kagari Aoki, Katsufumi Sato

    PloS one   14 ( 2 ) e0211138  2019  [International journal]

     View Summary

    Central place foraging theory (CPF) has been used to predict the optimal patch residence time for air-breathing marine predators in response to patch quality. Humpback whales (Megaptera novaeangliae) forage on densely aggregated prey, which may induce drastic change in prey density in a single feeding event. Thus, the decision whether to leave or stay after each feeding event in a single dive in response to this drastic change, should have a significant effect on prey exploitation efficiency. However, whether humpback whales show adaptive behavior in response to the diminishing prey density in a single dive has been technically difficult to test. Here, we studied the foraging behavior of humpback whales in response to change in prey density in a single dive and calculated the efficiency of each foraging dive using a model based on CPF approach. Using animal-borne accelerometers and video loggers attached to whales, foraging behavior and change in relative prey density in front of the whales were successfully quantified. Results showed diminishing rate of energy intake in consecutive feeding events, and humpback whales efficiently fed by bringing the rate of energy intake close to maximum in a single dive cycle. This video-based method also enabled us to detect the presence of other animals around the tagged whales, showing an interesting trend in behavioral changes where feeding duration was shorter when other animals were present. Our results have introduced a new potential to quantitatively investigate the effect of other animals on free-ranging top predators in the context of optimal foraging theory.

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    10
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  • Coral reef soundscape to measure the species distribution and biodiversity

    Tomonari Akamatsu, Tzu Hao Lin, Yu Tsao, Frederic Sinniger, Saki Harii

    2018 OCEANS - MTS/IEEE Kobe Techno-Oceans, OCEANS - Kobe 2018    2018.12

     View Summary

    Coral reefs represent the most biologically diverse marine ecosystem, however, they are vulnerable to environmental changes and impacts. Therefore, information on the variability of environment and biodiversity is essential for the conservation management of coral reefs. In this study, a soundscape analysis based on range-wide and long-term underwater recording were conducted. Maps of damselfishes and snapping sounds could be obtained by supervised feature extraction of species specific sounds. Using unsupervised classifier, Shannon index of soundscape diversity was shown to be high in deep waters. Mesophotic coral reefs in deep water have been considered as potential refuges for symbiotic corals when coral bleaching happens in shallow reefs due to high sea surface temperature. Results seemed to be consistent with this hypothesis.

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    6
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  • Automatic detection of fish sounds based on multi-stage classification including logistic regression via adaptive feature weighting

    Ryosuke Harakawa, Takahiro Ogawa, Miki Haseyama, Tomonari Akamatsu

    The Journal of the Acoustical Society of America   144 ( 5 ) 2709 - 2718  2018.11

     View Summary

    This paper presents a method for automatic detection of fish sounds in an underwater environment. There exist two difficulties: (i) features and classifiers that provide good detection results differ depending on the underwater environment and (ii) there are cases where a large amount of training data that is necessary for supervised machine learning cannot be prepared. A method presented in this paper (the proposed hybrid method) overcomes these difficulties as follows. First, novel logistic regression (NLR) is derived via adaptive feature weighting by focusing on the accuracy of classification results by multiple classifiers, support vector machine (SVM), and k-nearest neighbors (k-NN). Although there are cases where SVM or k-NN cannot work well due to divergence of useful features, NLR can produce complementary results. Second, the proposed hybrid method performs multi-stage classification with consideration of the accuracy of SVM, k-NN, and NLR. The multi-stage acquisition of reliable results works adaptively according to the underwater environment to reduce performance degradation due to diversity of useful classifiers even if abundant training data cannot be prepared. Experiments on underwater recordings including sounds of Sciaenidae such as silver croakers (Pennahia argentata) and blue drums (Nibea mitsukurii) show the effectiveness of the proposed hybrid method.

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    13
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  • Change in singing behavior of humpback whales caused by shipping noise

    Tsujii Koki, Akamatsu Tomonari, Okamoto Ryosuke, Mori Kyoichi, Mitani Yoko, Umeda Naoya

    PLOS ONE   13 ( 10 ) e0204112  2018.10  [Refereed]  [International journal]

     View Summary

    Reactions of singing behavior of individual humpback whales (Megaptera novaeangliae) to a specific shipping noise were examined. Two autonomous recorders separated by 3.0 km were used for the acoustic monitoring of each individual song sequence. A passenger-cargo liner was operated once per day, and other large ship noise was excluded given the remote location of the Ogasawara Islands, 1000 km south of Tokyo. In total, locations of between 26 and 27 singers were measured acoustically using time arrival difference at both stereo recorders on the ship presence and absence days, respectively. Source level of the ship (157 dB rms re 1μPa) was measured separately in deep water. Fewer whales sang nearby, within 500 m, of the shipping lane. Humpback whales reduced sound production after the ship passed, when the minimum distance to the whale from the ship trajectory was 1200 m. In the Ogasawara water, humpback whales seemed to stop singing temporarily rather than modifying sound characteristics of their song such as through frequency shifting or source level elevation. This could be a cost effective adaptation because the propagation loss at 500 m from the sound source is as high as 54 dB. The focal ship was 500 m away within several minutes. Responses may differ where ship traffic is heavy, because avoiding an approaching ship may be difficult when many sound sources exist.

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  • Automatic detection and localization of croaker’s fish calls using beamforming

    Ikuo Matsuo, Kazuki Yamato, Ryuzo Takahashi, Tomohito Imaizumi, Tomonari Akamatsu

    The Journal of the Acoustical Society of America   144 ( 3 ) 1692 - 1692  2018.09

    DOI

  • Presence and behavior of harbor porpoises (Phocoena phocoena) around set nets revealed using passive acoustic monitoring

    Higashisaka H, Matsuishi T, Akamatsu T

    Fisheries Research   204   269 - 274  2018.08  [Refereed]

     View Summary

    Harbor porpoises (Phocoena phocoena) are often captured as bycatch in set net fisheries, which may have a large impact on their population and reduces the efficiency of fishing operations. Therefore, this study aimed to use passive acoustic monitoring using “A-tag” stereo acoustic data loggers to observe the presence and movement of harbor porpoises in two large set nets off Usujiri, Hakodate, Hokkaido, Japan, from April to May 2013–2015. Bycatch of harbor porpoises in the set nets was surveyed from onboard the set net fishing boat. Harbor porpoises were observed in the final trap of the set net on 10 separate days; however, bycatch was confirmed only once. These results indicate that the number of harbor porpoises captured as bycatch represents only a fraction of the number that are present in the set net, demonstrating their ability to escape from the net.

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  • Preliminary report of the diving bahavior "fluke up/down dive" of humpback whales in response to ship noise off Ogasawara (Bonin) Islands, Japan

    Kyoichi Mori, Rina Yamada, Yukino Hirai, Ryosuke Okamoto, Koki Tsuji, Tomonari Akamatsu, Yoko Mitani, Toshio Tsuchiya, Naoya Umeda

    Abstract Book of the 2nd Oceanoise Asia     23  2018.06

  • Reactions of singing humpback whales to shipping noise in the Ogasawra Islands

    Koki Tsuji, Tomonari Akamatsu, Ryosuke Okamoto, Kyoichi Mori, Yoko Mitani, Naoya Umeda

    Abstract Book of the 2nd Oceanoise Asia     22  2018.06

  • Comparison of passive acoustic soniferous fish monitoring with supervised and unsupervised approaches

    Tzu Hao Lin, Yu Tsao, Tomonari Akamatsu

    Journal of the Acoustical Society of America   143 ( 4 ) EL278 - EL284  2018.04

     View Summary

    Passive acoustics has been used to investigate behavior and relative abundances of soniferous fish. However, because of noise interferences, it remains challenging to accurately analyze acoustic activities of soniferous fish. This study proposes a multi-method approach, which combines rule-based detector, periodicity-coded non-negative matrix factorization, and Gaussian mixture models. Although the three methods performed well when used to detect croaker choruses in quiet conditions, inconsistent results are observed in noisy conditions. A consistency matrix can provide insights regarding the bias of acoustic monitoring results. The results suggest that the proposed approach can reasonably improve passive acoustic monitoring of soniferous fish.

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  • Diel changes in ribbon seal Histriophoca fasciata vocalizations during sea ice presence in the Nemuro Strait, Sea of Okhotsk

    Mayuko Otsuki, Tomonari Akamatsu, Takahiro Nobetsu, Daisuke Mizuguchi, Yoko Mitani

    Polar Biology   41 ( 3 ) 451 - 456  2018.03  [Refereed]

     View Summary

    Ice-breeding seals use vocal communication mainly during breeding season. The vocal function of aquatic mating, ice-associated ribbon seals (Histriophoca fasciata) has been unknown since they produce sounds in both breeding and non-breeding seasons. We examined the timing of their vocal presence in relation to environmental factors to infer the function of their calls in the Nemuro Strait, northern Japan, since this area is the possible southern limit of their breeding range. Vocalizations of ribbon seals were irregularly sampled from November 2012 to March 2014 in the Nemuro Strait and were compared with sea ice presence, time of day, and tidal currents. Ribbon seal downsweeps were detected in February 2013 and March 2014 only when sea ice was present along the Shiretoko Peninsula in the strait, with more detections in March leading up to the spring breeding season. Downsweep detections decreased in the middle of the day, indicating that ribbon seals were likely to be hauled out during this time. Vocalizing at night and early morning would probably reflect the increased opportunity for attracting females underwater. Our study suggests that the seal vocalizations in concurrence with sea ice presence in the Nemuro Strait could function as underwater communication for breeding.

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    5
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  • Properties of Fish Sound by Fox Jacopever Sebastes vulpes, and Their Change with Agonistic Behavior

    MATSUBARA Naoto, MATSUDA Yuta, AKAMATSU Tomonari, TAKAHASHI Ryuzo, MUNEHARA Hiroyuki, YASUMA Hiroki

    J. Marine Acoust. Soc. Jpn.   45 ( 2 ) 37 - 46  2018

     View Summary

    &lt;p&gt;We observed the sound production and properties of fox jacopever (&lt;i&gt;Sebastes vulpes&lt;/i&gt;) in a water tank experiment to obtain basic information for the Passive Acoustic Monitoring (PAM). Six pairs of experiments including mature and immature fishes were conducted, and sound properties with and without agonistic behavior were compared. Fox jacopever produced low frequency pulses under 2,000 Hz. Pulse number ranged between 1–77, pulse duration was 0.005–0.220 s, pulse period was 0.001–0.989 s, and peak frequency was 258–490 Hz. These properties were changed by the presence or absence of agonistic behavior. Higher peak frequency over 400 Hz was observed only when a pair included an immature fish. Our results showed the potential use of fish sounds for estimating size and status of territorial behavior in this species by PAM.&lt;/p&gt;

    DOI CiNii

  • Tread-water feeding of Bryde's whales

    Takashi Iwata, Tomonari Akamatsu, Surasak Thongsukdee, Phaothep Cherdsukjai, Kanjana Adulyanukosol, Katsufumi Sato

    CURRENT BIOLOGY   27 ( 21 ) R1154 - R1155  2017.11  [Refereed]

     View Summary

    Many previous studies have shown that rorqual whales (Balaenopteridae), including the blue whale (Balaenoptera musculus), fin whale (B. physalus), sei whale (B. borealis), Bryde's whale (B. edeni), minke whale (B. acutorostrata), and humpback whale (Megaptera novaeangliae), employ a strategy called lunge feeding to capture a large amount of krill and/or fish for nourishment [1]. Lunge feeding entails a high energetic cost due to the drag created by an open mouth at high speeds [1,2]. In the upper Gulf of Thailand, Bryde's whales, which feed on small fish species [3], predominantly anchovies, demonstrated a range of feeding behaviors such as oblique, vertical, and lateral lunging. Moreover, they displayed a novel head-lifting feeding behavior characterized by holding the vertical posture for several seconds with an open mouth at the water surface. This study describes the head-lifting feeding by Bryde's whales, which is distinct from the typical lunge feeding of rorqual whales. Whales showing this behavior were observed on 58 occasions, involving 31 whales and including eight adult–calf pairs. Whales caught their prey using a series of coordinated movements: (i) lifting the head above the water with a closed mouth, (ii) opening the mouth until the lower jaw contacted the sea surface, which created a current of water flowing into the mouth, (iii) holding their position for several seconds, (iv) waiting for the prey to enter the mouth, and (v) closing the mouth and engulfing the prey underwater (Figure 1A–F, Movie S1 in Supplemental Information published with this article online). When a whale kept its upper jaw above the sea surface, many anchovies in the targeted shoal appeared to lose orientation and flowed passively into the mouth of the whale by the current created by the lower mandible breaking the surface of the water. We measured the duration of feeding events when the whales had a wide-open mouth mostly above the sea surface. The mean and maximum feeding durations were 14.5 ± 5.4 (SD; n = 58 events) and 32 s, respectively. Deployment of animal-borne data loggers yielded approximately 44 minutes of recordings from a single whale. The acceleration data showed that stroke rates, including tail beat and whole-body movements during feeding, were faster (approximately 0.7 s cycle) than during a cruising swim (approximately 3 s cycle) (Figure 1G). The swimming speed was lower than that in the stall speed (0.2 m s−1) of the device during the feeding phase, suggesting that thrust force was used to hold the head up and to stabilize body posture (Figure 1G). Stable positioning using the fluke and flipper was confirmed by video data for both the downward and upward direction of the whale (Figure S1). According to the visual and behavioral data, we named the head-lifting feeding as ‘tread-water feeding’. Generally, all species of baleen whale, including rorqual whales, show active chasing and feeding, i.e., skimming, suction, and engulfing with lunging [1]. Tread-water feeding is considered passive feeding as compared with other feeding behaviors because the whales do not swim forward in pursuit of prey during the period from mouth opening to closing, and although they need thrust force to stabilize their posture, the head does not actively move. To the best of our knowledge, this discovery of tread-water feeding in Bryde's whales represents the first report of passive feeding in baleen whales, which indicates their flexible capacity to modify their foraging strategy in relation to variable environments. Iwata et al. report ‘tread-water’ feeding in Bryde's whales, a form of passive feeding in baleen whales.

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  • Silent porpoise: potential sleeping behaviour identified in wild harbour porpoises

    Andrew J. Wright, Tomonari Akamatsu, Kim N. Mouritsen, Signe Sveegaard, Rune Dietz, Jonas Teilmann

    ANIMAL BEHAVIOUR   133   211 - 222  2017.11  [Refereed]

     View Summary

    All animals sleep and it is essential for maintaining optimal brain function. However, cetaceans engage in the unusual practice of unihemispherical sleep, where only half of their brain sleeps at a time, due to their constant need for movement and breathing. Most studies of sleep in cetaceans have occurred in captivity. However, tagging devices have now developed to the point where the data collected from wild animals can be assessed against published criteria for defining sleep behaviourally. Seven acoustic and behavioural data loggers were deployed on harbour porpoises, Phocoena phocoena, in Danish waters between May 2010 and August 2011 and stayed on the animals between 53 and 72 h, recording 1884 to 2755 valid dives per animal. Parabolic dives with significantly reduced bioacoustic activity and a stereotyped behavioural pattern were identified as potential sleeping periods. The recordings for nearly half of the parabolic dives were found to contain no vocalization (echolocation clicks), significantly more than other dive types. Of the remaining parabolic dives, the click rate was, when normalized to their individual means, also significantly lower than detected in other dive types. Additionally, parabolic dives were shallow compared to all other dive types, and found to have a stereotypic low-energy profile. They were also found to contain fewer rolls and incorporate a lower vertical descent rate than most other dive types. If the data are representative, harbour porpoises spend a small, but meaningful amount of their diving time engaged in parabolic dives and thus potentially sleeping. All animals have a fundamental need for undisturbed sleep. These quiet periods thus need to be considered in studies of anthropogenic effects, but also those employing passive acoustic monitoring techniques, as well as in efforts to reduce incidental bycatch in fisheries, given the associated periods of reduced environmental awareness. (C) 2017 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.

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  • Automatic Detection Method of Croaker's Fish Call Using Beamforming

    Kazuki Yamato, Ikuo Matsuo, Ryuzo Takahashi, Tomohito Imaizumi, Tomonari Akamatsu

    海洋音響学会誌   44 ( 4 ) 193‐202 - 202  2017.10  [Refereed]

    DOI CiNii J-GLOBAL

  • Diversity of fish sound types in the Pearl River Estuary, China

    Zhi-Tao Wang, Douglas P. Nowacek, Tomonari Akamatsu, Ke-Xiong Wang, Jian-Chang Liu, Guo-Qin Duan, Han-Jiang Cao, Ding Wang

    PEERJ   5 ( 10 )  2017.10  [Refereed]

     View Summary

    Background. Repetitive species-specific sound enables the identification of the presence and behavior of soniferous species by acoustic means. Passive acoustic monitoring has been widely applied to monitor the spatial and temporal occurrence and behavior of calling species.
    Methods. Underwater biological sounds in the Pearl River Estuary China, were collected using passive acoustic monitoring with special attention paid to fish,sounds. A total of 1,408 suspected fish calls comprising 18,942 pulses were qualitatively analyzed using a customized acoustic analysis routine.
    Results. We identified a diversity of 66 types of fish sounds. In addition to single pulse, the sounds tended to have a pulse train structure. The pulses were characterized by an approximate 8 ms duration, with a peak frequency from 500 to 2,600 Hz and a majority of the energy below 4,000 Hz. The median inter-pulsepeak interval (IPPI) of most call types was 9 or 10 ms. Most call types with median IPPIs of 9 ms and 10 ms were observed at times that were exclusive from each other, suggesting that they might be produced by different species. According to the literature, the two section signal types of 1 + 1 and 1 + Nic, might belong to big-snout croaker (Johnius macrorhyuus), and 1 + N-19 might be produced by Belanger's croaker (J. belarigerii).
    Discussion. Categorization of the baseline ambient biological sound is an important first step in mapping the spatial and temporal patterns of soniferous fishes. The next step is the identification of the species producing each sound. The distribution pattern of soniferous fishes will be helpful for the protection and management of local fishery resources and in marine environmental impact assessment. Since the local vulnerable Indo-Pacific humpback dolphin (Sousa chineusis) mainly preys on soniferous fishes, the fine-scale distribution pattern of soniferous fishes can aid in the conservation of this species. Additionally, prey and predator relationships can be observed when a database of species-identified sounds is completed.

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  • Estimation of Direction of Arrival of Fish Calls in a Chorus Using Stereo Hydrophones

    Masanori Ito, Ikuo Matsuo, Tomohito Imaizumi, Tomonari Akamatsu

    MARINE TECHNOLOGY SOCIETY JOURNAL   51 ( 4 ) 68 - 75  2017.07  [Refereed]

     View Summary

    Some fish species produce sounds consisting of periodic pulses that are associated with distinct behaviors (e.g., courtship). Thus, the ability to estimate the direction of arrival from recorded sounds could provide insight into fish ecology and behavior. A stereo recording system was used to monitor underwater fish call sounds. The recorded signals were subjected to automatic processing to detect sounds that had the characteristics of fish calls. The direction of arrival for each detected sound was then estimated using the arrival time difference between the two hydrophones. Simulations confirmed that the recording system could accurately estimate the direction of arrival of fish call sounds. Furthermore, a blind source separation method was used to separate detected sounds originating from multiple individuals or groups of fish. Using this method, the direction of arrival for calls from multiple sources was estimated. The method described in this paper was successfully applied to monitor and isolate sounds from white croaker (Pennahia argentata) in the ocean.

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  • Evaluation of availability on passive acoustic devices on underwater platforms

    Ryuzo Takahashi, Tomonari Akamatsu, Daisuke Hasegawa, Takeshi Okunishi, Yuya Nishida, Tamaki Ura, Hiroshi Takahashi, Masami Katsuragawa

    Techno-Ocean 2016: Return to the Oceans     317 - 320  2017.03

     View Summary

    The noise evaluation of the platform is necessary to use passive acoustic monitoring. In this study, we measured background noise of underwater platforms such as AUVs and deep sea landers. AUV that has thrusters was higher background noise level, when control own position and speed. However, background noise level was deduced, when stopped thrusters. The background noise of AUV of the type of control buoyance of own and of the deep sea lander was low. The background noise of AUVs on low frequency range was higher than high frequency range. A biological sound was observed using AUV. Even if AUV was to depth of the water 900m, the sound of the creature was measured. Therefore, the biological sound could be observed using AUVs or the deep sea lander, and the possibility that the biological sound could be observed automatically and extensively was indicated.

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    1
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  • Acoustic presence of finless porpoises around the Kansai International airport

    Kiyomi Nakamura, Yuji Hirakawa, Naoki Kamezaki, Takashi Nakata, Yusuke Ono, Masaki Hatano, Tomonari Akamatsu

    Techno-Ocean 2016: Return to the Oceans     342 - 345  2017.03

     View Summary

    Presence of finless porpoises around Kansai International airport was monitored by a passive acoustic monitoring system. The airport is an artificial land in the ocean and was suggested to create new habitat of marine organisms. Here we showed frequent nocturnal presence of finless porpoises at the south west of the airport where quite limited visual observation data available previously. During 4 months period from December to April in 2016, biosonar sounds of finless porpoises were detected nearly every day. Accumulated number of click trains in one hour time bin were 100 or larger in the nighttime. In contrast, approximately 50 click trains were recorded in the daytime. Ocean engineering newly created an island, Kansai International airport. This structure might create new habitat even for top predators in this water.

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    1
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  • Real time detection and localization system for underwater acoustic signal with cable observatories in the west Pacific Ocean

    Shuhei Nishida, Ryoichi Iwase, Katsuyoshi Kawaguchi, Ikuo Matsuo, Tomonari Akamatsu

    Techno-Ocean 2016: Return to the Oceans     544 - 547  2017.03

     View Summary

    A previous research reported that the cable system off Kushiro-Tokachi was detected low frequency calls of fin whales. In this research, as an application using cable observatories about 'development of remote species identification technologies for marine organisms', we developed a real-time processing system for underwater acoustic signal with cable observatory. This paper reports the results of automatically detection and localization from continues observation using hydrophones and seismometers of the cable observatory. The applied system in cable observatories visualizes the number and position of fin whales.

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    2
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  • Ocean acoustic observing platforms for marine creatures around Japan

    Tomonari Akamatsu, Ryuzo Takahasi, Tomohito Imaizumi, Katsuyoshi Kawaguchi, Ryoichi Iwase, Shuhei Nishida

    Techno-Ocean 2016: Return to the Oceans     425 - 428  2017.03

     View Summary

    Many animals in the ocean produce sounds for mating choice, territorial defending, group cohesion and echolocation. Sound travels much longer distance in the water comparing with light that makes the acoustic waves efficient for long distance communication and sensing. The species or family specific sounds can be used to identify not only the presence of animals but also counting the number and density of target species. In these years, various types of underwater recorders are available. However, for the successful acoustic monitoring in the ocean, safe platforms to deploy the recorders are essential. In this paper, advantages and drawbacks of fixed and mobile platforms for passive acoustic monitoring are summarized referring practical application examples in Japanese waters.

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    1
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  • Long-term effectiveness of pingers on a small population of finless porpoises in Japan

    Masao Amano, Miku Kusumoto, Misaki Abe, Tomonari Akamatsu

    Endangered Species Research   32 ( 1 ) 35 - 40  2017

     View Summary

    Finless porpoises Neophocaena spp. are under pressure from various anthropogenic impacts due to their coastal habitat. Net fishery bycatch is considered a major risk for the populations around Japan, and mitigation measures are required. We carried out a long-term study to assess the efficiency of acoustic pingers in reducing the encounter rates of narrow-ridged finless porpoises with fishing nets. We used a passive ultrasonic event recorder (A-tag) to obtain acoustic encounter rates of echolocating finless porpoises and compared results for the presence and absence of pinger transmissions in Omura Bay, Japan, over two 8-mo periods (2011 and 2012). Encounter rates were significantly lower during periods when pingers were in operation, but the effect of pingers decreased with time. By the eighth month of the study in each study year, the number of encounters during the ensonified period was greater than that during periods without pingers, suggesting habituation. When pingers were reactivated at the study site after 4 mo of silence, the encounters with the active pingers returned to the lower level observed at the beginning of the experiment. These results reveal that the pingers effectively induce avoidance in porpoises, but that this effectiveness only lasts for a few months, which is likely due to habituation which could be mitigated by alternating periods of several months of silence between periods of active pinger use.

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    15
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  • Fin whale calls observed with submarine cabled observatories off Kushiro-Tokachi during ten years

    Shuhei Nishida, Ryoichi Iwase, Katsuyoshi Kawaguchi, Ikuo Matsuo, Tomonari Akamatsu

    OCEANS 2016 MTS/IEEE Monterey, OCE 2016    2016.11

     View Summary

    In this research, the automatically analyzation method which detect acoustic events such as fin whale calls and its locations is embedded in cable observatory system. This system has detection method about fin whale calls using spectrogram correlation, and the localization of fin whale calls using two hydrophones and a three-axis seismometer. This observation at off Kushiro-Tokachi has been continuously performed for more than 10 years. The detection and tracking analysis for fin whale calls are carried out about the archive data in parallel with the real-time data. The results of the past 10 years including the latest information is reported.

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  • Acoustic property of sound production by fat greenling (Hexagrammos otakii) in spawning season

    Naoto Matsubara, Hiroyuki Munehara, Ryuzo Takahashi, Tomonari Akamatsu, Kazuki Yamato, Ikuo Matsuo, Nobuo Kimura, Kazuyoshi Maekawa, Hiroki Yasuma

    The Journal of the Acoustical Society of America   140 ( 4 ) 3065 - 3065  2016.10

    DOI

  • The migration of fin whales into the southern Chukchi Sea as monitored with passive acoustics

    Koki Tsujii, Mayuko Otsuki, Tomonari Akamatsu, Ikuo Matsuo, Kazuo Amakasu, Minoru Kitamura, Takashi Kikuchi, Kazushi Miyashita, Yoko Mitani

    ICES Journal of Marine Science   73 ( 8 ) 2085 - 2092  2016.09

     View Summary

    <title>Abstract</title>
    Fin whales (Balaenoptera physalus) undergo seasonal migration in the Arctic Sea. Because their migration and distribution is likely affected by changes in global climate, we aimed to examine the migration timing of fin whales, and the relationship with prey availability within the oceanographic environment of the Arctic Sea, using passive and active acoustic monitoring methods. Automatic Underwater Sound Monitoring Systems were deployed in the southern Chukchi Sea from July 2012 to 2014 to determine the acoustic presence of fin whales. Furthermore, water temperature and salinity were recorded by a fixed data logger. An Acoustic Zooplankton Fish Profiler was additionally deployed to estimate prey abundance through backscattering strength. Sea ice concentrations were obtained by remote sensing data. Fin whale calls were automatically detected using a custom-made software, and the per cent of half-hours containing calls were counted. Fin whale calls were detected from 4 August to 20 October 2012 (78 d) and 25 July to 1 November 2013 (100 d). The extended period of acoustic presence of fin whales during 2013 when compared with 2012 is likely related to a longer ice-free period during 2013. Furthermore, generalized linear model analyses showed that half-hour periods containing calls increased with a rise in water temperature and zooplankton abundance during the initial call presence period, while they decreased with a decrease in water temperature and salinity during the end of the call presence period. Our results suggest that the rise in water temperature and zooplankton abundance affect the timing of migration of fin whales in a way that is consistent with the expansion of their suitable habitats and the extension of their presence in the Arctic Sea.

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    19
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  • The study of automatic detection of croaker sounds

    Yuko Miyajima-Taga, Tomonari Akamatsu, Ikuo Matsuo, Maki Takahashi, Hirokazu Matsuzaki, Keiji Niijima

    The journal of the Marine Acoustics Society of Japan   43 ( 3 ) 116 - 125  2016.07  [Refereed]

    DOI CiNii

  • Auditory sensitivity in aquatic animals

    Klaus Lucke, Arthur N. Popper, Anthony D. Hawkins, Tomonari Akamatsu, Michel Andre, Brian K. Branstetter, Marc Lammers, Craig A. Radford, Amanda L. Stansbury, T. Aran Mooney

    JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA   139 ( 6 ) 3097 - 3101  2016.06  [Refereed]

     View Summary

    A critical concern with respect to marine animal acoustics is the issue of hearing "sensitivity," as it is widely used as a criterion for the onset of noise-induced effects. Important aspects of research on sensitivity to sound by marine animals include: uncertainties regarding how well these species detect and respond to different sounds; the masking effects of man-made sounds on the detection of biologically important sounds; the question how internal state, motivation, context, and previous experience affect their behavioral responses; and the long-term and cumulative effects of sound exposure. If we are to better understand the sensitivity of marine animals to sound we must concentrate research on these questions. In order to assess population level and ecological community impacts new approaches can possibly be adopted from other disciplines and applied to marine fauna. (C) 2016 Acoustical Society of America.

    DOI PubMed

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    8
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  • Apparent source level of free-ranging humpback dolphin, Sousa chinensis, in the South China Sea

    Satoko Kimura, Tomonari Akamatsu, Liang Fang, Zhitao Wang, Kexiong Wang, Ding Wang, Ken Yoda

    JOURNAL OF THE MARINE BIOLOGICAL ASSOCIATION OF THE UNITED KINGDOM   96 ( 4 ) 845 - 851  2016.06  [Refereed]

     View Summary

    The acoustic performance and behaviour of free-ranging cetaceans requires investigation under natural conditions to understand how wild animals use sound. This is also useful to develop quantitative evaluation techniques for passive acoustic monitoring. There have been limited studies on the acoustics of the Indo-Pacific humpback dolphin; nevertheless, this species is of particular concern because of the anthropogenic activity in the coastal habitats. In the present study, we used a four-hydrophone array to estimate the apparent source levels (ASLs) of biosonar sequences (click trains), of this species in San-Niang Bay, China. As the dolphins approached the array, 173 click trains were found to meet the criteria of on-axis sounds produced within 60 m of the equipment. In total, 121 unclipped click trains were used for the ASL estimation. The qualified click trains contained 36.3 +/- 32.5 clicks, lasting for 1.5 +/- 1.5 s, with average inter-click intervals (ICIs) of 51.2 +/- 38.3 ms. Average ICIs showed a bimodal distribution, with a cut-off at 20 ms. Short-range click trains, with short ICIs of,20 ms on average, were characterized by smaller ASLs, relatively stable ICIs and a shorter click train duration. The mean back-calculated ASL for humpback dolphins with an approximately maximum body size of 2.5 m was 181.7 +/- 7.0 dB re 1 mu Pa at a distance of 1.6-57.2 m. This value was comparable to that recorded for other dolphins of similar body size, although the ASL estimates obtained in this study might be conservative.

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    16
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  • Local habitat use by botos (Amazon river dolphins, Inia geoffrensis) using passive acoustic methods

    Yukiko Yamamoto, Tomonari Akamatsu, Vera M.F. da Silva, Shiro Kohshima

    Marine Mammal Science   32 ( 1 ) 220 - 240  2016.01

     View Summary

    We monitored the underwater behavior of botos (Inia geoffrensis) using stereo acoustic data loggers to observe their local habitat use and its diel changes at the Mamirauá Sustainable Development Reserve, Brazil. A-tags were set at five sites in three different habitat types: Lake (low current), Channel (middle current), and Junction (junction of two channels). The presence index during nighttime was significantly greater than during daytime in the Lake and Junction. Underwater movement was estimated from the changing pattern (trajectory) of the relative angle of the sound source from A-tags. A staying-type trajectory was dominant in the Lake, although the prevalence of moving-type trajectory increased at night. More than 80% of detected trajectories were the staying type in the Junction, while moving-type trajectories dominated in the Channel. The frequency of click trains was greatest in the Lake, followed by the Junction and Channels. The average interpulse interval, which reflects the mean target distance of echolocation, was shortest in the Lake, followed by the Junction and Channel. These results suggest that the botos used the Lake as their primary habitat for active behaviors like foraging, especially at night, and the Junction as their primary habitat for relatively inactive behaviors at night.

    DOI

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    7
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  • キツネメバル(Sebastes vulpes)の行動に伴う 鳴音の特性

    松原 直人, 松田 裕太, 高橋 竜三, 赤松 友成, 宗原 弘幸, 木村 暢夫, 前川 和義, 安間 洋樹

    日本水産工学会 学術講演会 学術講演論文集   2016   133 - 134  2016

    DOI CiNii

  • Acoustic species identification of small cetaceans

    Kameyama Saho, Akamatsu Tomonari, Arai Nobuaki

    Journal of Advanced Marine Science and Technology Society   22 ( 1 ) 57 - 61  2016

     View Summary

    Passive acoustic monitoring (PAM) has been widely used as the standard method to observe small cetaceans. Recent drastic improvement of monitoring device makes PAM more convenient, cost-effective monitoring method. Also, improvement of analysis methods of acoustic data enables us to estimate habitat range, density, behavior of animals using PAM. However, most previous studies focus on one species and select the data that the observed species were confirmed visually. In order to extend the application of PAM to the field that several species appear simultaneously, species identification method is essential. Especially, PAM plays a key role of environmental assessment on marine development such as offshore wind farm in recent years. In that case, it is important to observe each species which appear in the construction area separately for effective conservation. This paper reviewed the recently developed species identification methods. Basically, many identification methods focused on one of two types of animal call, whistles used for communications or biosonar signals used for echolocation. We introduce the advantage and disadvantage of the method using whistles or biosonar signals, and discuss the current issues and future works we need to resolve them.

    DOI CiNii

  • Migration monitoring of fin whales in the southern Chukchi Sea with acoustic methods during 2012–2015

    Koki Tsujii, Mayuko Otsuki, Tomonari Akamatsu, Ikuo Matsuo, Minoru Kitamura, Takashi Kikuchi, Kazuo Amakasu, Kazushi Miyashita, Yoko Mitani

    2016 Techno-Ocean (Techno-Ocean)     49 - 53  2016

     View Summary

    Environmental changes are considered to affect the migration and distribution of baleen whales in the Arctic region. We examined the seasonal acoustic presence of fin whales (Balaenoptera physalus) and the relationships between acoustics and oceanographic environments in the southern Chukchi Sea from July 2012 to October 2015. Fin whale calls were detected from 4 August to 20 October 2012, from 25 July to 1 November 2013, from 26 July to 14 November 2014, and 7 June 2015, only in the ice-free (sea ice concentration = 0%) periods. In addition, from the recordings in 2012 and 2013, fin whale calls were present in the periods of high prey abundance, and there were significant positive correlations among their call presence, prey abundance, water temperature and salinity. Furthermore, the result that the calls were detected in 7 June 2015 suggests that fin whales arrive much earlier at the southern Chukchi Sea than previously reported. Our study provide valuable information to assess the impact on marine ecosystem in the Arctic region by environmental changes.

    DOI

  • Contribution to the Understanding of Particle Motion Perception in Marine Invertebrates

    Michel Andre, Kenzo Kaifu, Marta Sole, Mike van der Schaar, Tomonari Akamatsu, Andreu Balastegui, Antonio M. Sanchez, Joan V. Castell

    EFFECTS OF NOISE ON AQUATIC LIFE II   875   47 - 55  2016  [Refereed]

     View Summary

    Marine invertebrates potentially represent a group of species whose ecology may be influenced by artificial noise. Exposure to anthropogenic sound sources could have a direct consequence on the functionality and sensitivity of their sensory organs, the statocysts, which are responsible for their equilibrium and movements in the water column. The availability of novel laser Doppler vibrometer techniques has recently opened the possibility of measuring whole body ( distance, velocity, and acceleration) vibration as a direct stimulus eliciting statocyst response, offering the scientific community a new level of understanding of the marine invertebrate hearing mechanism.

    DOI PubMed

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  • Visualization of fish movement and size estimation of the fish by using broadband split-beam echo sounder

    Tomohito Imaizumi, Koki Abe, Ryuzo Takahashi, Ikuo Matsuo, Tomonari Akamatsu

    TECHNO-OCEAN 2016: RETURN TO THE OCEANS     552 - 555  2016  [Refereed]

     View Summary

    It is important information to measure fish movement, swimming direction, and target strength of the fish for species identification by using active acoustics. Broadband quantitative echo sounders have been developed in the world. Broadband system can measure single echo traces from individual fish with high range resolution. Single echo traces with high range resolution give us much more information of fish movements than by using conventional narrow band quantitative echo sounders. This paper presents the results of our in situ measurements.

    DOI

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    1
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  • Review of Low-Level Bioacoustic Behavior in Wild Cetaceans: Conservation Implications of Possible Sleeping Behavior

    Andrew J. Wright, Tomonari Akamatsu, Kim Norgaard Mouritsen, Signe Sveegaard, Rune Dietz, Jonas Teilmann

    EFFECTS OF NOISE ON AQUATIC LIFE II   875   1251 - 1258  2016  [Refereed]

     View Summary

    Shallow, low-activity, low-biosonar parabolic-shaped dives were observed in biologging data from tagged harbor porpoises in Danish waters and identified as potential sleeping behavior. This behavioral state merits consideration in assessing the context for noise exposure and passive acoustic monitoring studies. Similar dives have also been reported for other cetacean species. The existence of low-level bioacoustic dives that may represent that sleeping has implications for the mitigation of not only noise exposure but also of bycatch as well as legal repercussions given the protected status of sleeping, as a part of resting, under many legislative regimes.

    DOI PubMed

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  • Passive Acoustic Monitoring the Diel, Lunar, Seasonal and Tidal Patterns in the Biosonar Activity of the Indo-Pacific Humpback Dolphins (Sousa chinensis) in the Pearl River Estuary, China

    Zhi-Tao Wang, Paul E. Nachtigall, Tomonari Akamatsu, Ke-Xiong Wang, Yu-Ping Wu, Jian-Chang Liu, Guo-Qin Duan, Han-Jiang Cao, Ding Wang

    PLOS ONE   10 ( 11 )  2015.11  [Refereed]

     View Summary

    A growing demand for sustainable energy has led to an increase in construction of offshore windfarms. Guishan windmill farm will be constructed in the Pearl River Estuary, China, which sustains the world's largest known population of Indo-Pacific humpback dolphins (Sousa chinensis). Dolphin conservation is an urgent issue in this region. By using passive acoustic monitoring, a baseline distribution of data on this species in the Pearl River Estuary during pre-construction period had been collected. Dolphin biosonar detection and its diel, lunar, seasonal and tidal patterns were examined using a Generalized Linear Model. Significant higher echolocation detections at night than during the day, in winter-spring than in summer-autumn, at high tide than at flood tide were recognized. Significant higher echolocation detections during the new moon were recognized at night time. The diel, lunar and seasonal patterns for the echolocation encounter duration also significantly varied. These patterns could be due to the spatial-temporal variability of dolphin prey and illumination conditions. The baseline information will be useful for driving further effective action on the conservation of this species and in facilitating later assessments of the effects of the offshore windfarm on the dolphins by comparing the baseline to post construction and post mitigation efforts.

    DOI PubMed

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    50
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  • Seasonal Distribution of Indo-Pacific Humpback Dolphins at an Estuarine Habitat: Influences of Upstream Rainfall

    Tzu Hao Lin, Tomonari Akamatsu, Lien Siang Chou

    Estuaries and Coasts   38 ( 4 ) 1376 - 1384  2015.10

     View Summary

    River estuaries are dynamic regions that are influenced by the interactions between freshwater and seawater as well as seasonal variations in river runoffs. Studies focusing on the distribution of Indo-Pacific humpback dolphins (Sousa chinensis) have indicated their general tendency toward estuarine habitats. The seasonal activities of humpback dolphins are likely to synchronize with environmental fluctuations. This study investigated the effects of seasonal changes in river runoffs on the distribution gradient of humpback dolphins by deploying acoustic data loggers along the Xin Huwei River estuary, Western Taiwan, between July 2009 and September 2012. Seasonal shifts were observed in the areas with high detected duration of humpback dolphins, which mainly stayed near the river mouth during the dry seasons but moved seaward during rainy seasons and following heavy rainfall. In addition, the gradient of ambient ultrasonic pulses, dominated by snapping shrimp sounds, exhibited regional differences following heavy rainfall. The outward movements of the humpback dolphins and the snapping shrimp sounds in the estuary indicated a temporary trophic-system shift in response to local environmental changes resulting from high volumes of river runoffs. In the future, the seasonal variation in the distribution of humpback dolphins must be considered during the conservation management of this critically endangered population.

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    30
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  • Acoustic characteristics of biosonar sounds of free-ranging botos (Inia geoffrensis) and tucuxis (Sotalia fluviatilis) in the Negro River, Amazon, Brazil

    Yukiko Yamamoto, Tomonari Akamatsu, Vera M.F. Da Silva, Yayoi Yoshida, Shiro Kohshima

    Journal of the Acoustical Society of America   138 ( 2 ) 687 - 693  2015.08

     View Summary

    Odontoceti emit broadband high-frequency clicks on echolocation for orientation or prey detection. In the Amazon Basin, two odontoceti species, boto (Amazon River dolphin, Inia geoffrensis) and tucuxi (Sotalia fluviatilis), live sympatrically. The acoustic characteristics of the echolocation clicks of free-ranging botos and tucuxis were measured with a hydrophone array consisting of a full-band and an acoustic event recorder (A-tag). The clicks of the two species were short-duration broadband signals. The apparent source level was 201 dB 1 μPa peak-to-peak at 1 m in the botos and 181 dB 1 μPa peak-to-peak at 1 m in the tucuxis, and the centroid frequency was 82.3 kHz in the botos and 93.1 kHz in the tucuxis. The high apparent source level and low centroid frequency are possibly due to the difference in body size or sound production organs, especially the nasal structure, the sound source of clicks in odontoceti.

    DOI PubMed

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    5
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  • Target strength spectra of tracked individual fish in schools

    Masanori Ito, Ikuo Matsuo, Tomohito Imaizumi, Tomonari Akamatsu, Yong Wang, Yasushi Nishimori

    FISHERIES SCIENCE   81 ( 4 ) 621 - 633  2015.07  [Refereed]

     View Summary

    Broadband sonar echoes received from individual fish in schools contain information that might be useful for species discrimination. The echo characteristics are closely related to the incident angle of the sound to fish body, corresponding to the apparent tilt angle of a fish from a viewpoint of a transducer. Therefore, it is necessary to isolate individual fish echoes and estimate the incident angles. In this study, a broadband split-beam echo sounder system was used to extract features from free-swimming fish schools. Echoes from individual fish in dense schools were measured and their position was estimated using the system with a downward-oriented acoustic beam. Individual fish were tracked in schools of Japanese jack mackerel Trachurus japonicus, chub mackerel Scomber japonicus, and red sea bream Pagrus major with the system. The target strength (TS) spectra of echoes ranging from 80 to 120 kHz were calculated and sorted on the basis of the incident angle, which was estimated by the tracking result. Using this approach, TS spectra were obtained from entire schools of free-swimming fish, and the obtained TS spectra were found to be dependent on fish species and the incident angles of the individual fish involved.

    DOI

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    7
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  • Issues and an optimal application of acoustic survey for freshwater cetaceans

    Arnab Das, Tomonari Akamatsu

    2015 IEEE Underwater Technology, UT 2015    2015.05

     View Summary

    Freshwater cetaceans are among the data deficient and now recognized as the most threatened group of marine mammals. Large scale studies are required to be done on an urgent basis to ensure reasonable chance of survival for these species. A detailed analysis of the freshwater habitats globally, indicate tropical shallow environment (important for the survival of the freshwater cetaceans). Visual surveys being employed for abundance estimates have significant limitations and acoustic surveys have recently been identified as effective alternative and could complement the visual surveys for conservation efforts. However, two major issues can be prominent such as shallow water sound propagation and noise pollutions. It is well known that shallow waters result in multiple interaction of the acoustic signal with the surface and the bottom prior to being received at the hydrophone receiver. The tropical waters further cause random surface and bottom behaviour resulting in substantial site specific underwater channel fluctuations being coupled to the desired marine mammal signal. Thus, the acoustic survey efforts in the tropical shallow habitats are highly sensitive to the local conditions and demand efforts to mitigate the underwater channel fluctuations while pursuing analysis efforts on the received signal. Increasing population in these regions has resulted in unregulated waterborne activities linked to economic growth. Such activities have caused significant increase in the ambient noise in these habitats. The effectiveness of acoustic sensors is further limited by the high ambient noise in the habitat and could also impact survival chances of these critically endangered species. This work attempts to put in perspective the challenges of acoustic surveys in tropical shallow habitats and provide a way ahead for effective passive acoustic monitoring of the freshwater cetaceans globally.

    DOI

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  • Development of behavioral control and visualization of fisheries species using acoustic technique

    Tomonari Akamatsu

    NIPPON SUISAN GAKKAISHI   81 ( 3 ) 389 - 392  2015.05  [Refereed]

    DOI

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    1
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  • Yangtze finless porpoises along the main channel of Poyang Lake, China: Implications for conservation

    Dong Lijun, Wang Ding, Wang Kexiong, li Songhai, Mei Zhigang, Wang Shiyong, Akamatsu Tomonari, Kimura Satoko

    MARINE MAMMAL SCIENCE   31 ( 2 ) 612 - 628  2015.04  [Refereed]

     View Summary

    Poyang Lake is the largest freshwater lake in China and flows into the Yangtze River. It is a traditional habitat for the endangered Yangtze finless porpoise, which has not been well investigated. To reveal the distribution of the porpoise in Poyang Lake, 12 passive acoustic surveys were conducted along 123 km of the main channel of the lake during different seasons (spring transition season, wet season, autumn transition season, and dry season) from 2008 to 2012. We counted the number of phonating porpoises encountered and calculated the detection rate (encountered individuals detected per kilometer). The median porpoise detection rates ranged from 0 to 0.65 individuals per kilometer during the different surveys. The highest median detection rate of 0.50 was detected in the autumn transition season. The seasonal shrinking of the lake during the dry season may cause a concentration of porpoises in the narrow channels and a high incidence of collisions with cargo ships and fishing boats. Conservation actions should be focused on the main channel of the lake during the dry and transition seasons. In addition, the expansion of the existing reserve to include areas with high porpoise detection rates is necessary.

    DOI

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    31
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  • Passive acoustic monitoring of Japanese spiny lobster stridulating sounds

    Mumi Kikuchi, Tomonari Akamatsu, Tomohiro Takase

    FISHERIES SCIENCE   81 ( 2 ) 229 - 234  2015.03  [Refereed]

     View Summary

    The Japanese spiny lobster Panulirus japonicus is an important marine resource in Japan. In order to manage its stock, an effective methodology for population assessments is needed. In this study, we focused on the stridulating sounds produced by spiny lobsters. The stridulating sounds are widely accepted to function as an anti-predator signaling, for potential use in monitoring lobster stocks remotely. An underwater sound recorder was attached on gill nets or lobster pots around Izu Oshima and Niijima islands, within the Izu archipelago, Tokyo, Japan, where lobster fishing is common. Stridulating sounds were manually extracted from each data file. The frequency of stridulating sounds tended to increase on nights with a large tidal change. There was a positive correlation between the frequency of stridulating sounds and the number of lobsters caught in the net or lobster pot. Even in trials where no lobsters were caught, several stridulating sounds could be detected and increased at night. In this study, we describe the sound characteristics of the stridulation, and the trend of nocturnal call productions of this species. This study is the first step towards passive acoustic resource monitoring of Japanese spiny lobsters, which were quite difficult to estimate the density of remotely.

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    8
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  • Frequent and prolonged nocturnal occupation of port areas by Yangtze finless porpoises (Neophocaena asiaeorientalis): Forced choice for feeding?

    Zhitao Wang, Tomonari Akamatsu, Zhigang Mei, Lijun Dong, Tomohito Imaizumi, Kexiong Wang, Ding Wang

    INTEGRATIVE ZOOLOGY   10 ( 1 ) 122 - 132  2015.01  [Refereed]

     View Summary

    During the Yangtze Freshwater Dolphin Expedition 2012, Yangtze finless porpoises (Neophocaena asiaeorientalis) were acoustically monitored in 9 port areas at night. During 6566 min of nocturnal monitoring, porpoise sonar was detected for 488 min (7.43% of the total time). Of all 81 encounters, the longest echolocation span obtained was 102.9 min, suggesting frequent and prolonged porpoise occupation of the port areas. A combined total of 2091 click trains were recorded, with 129 (6.2%) containing minimum inter-click intervals (ICIs) below 10 ms (termed a buzz). Buzzes with a decrease in ICIs and search and approach phases that resembled feeding echolocation signals accounted for 44.2% (N = 52) of all buzzes. Buzzes with an increase in ICIs, suggesting a mirrored prey capture phase, accounted for 20.2% (N = 26) and could reflect attempts to locate escaped prey because they were followed by approach-phase feeding buzzes. Anecdotal evidence of porpoises fleeing the proximity of vessels was observed. The recordings indicating clusters of porpoises feeding near the port areas suggest a forced choice for feeding due to the relatively higher prey availability in the port areas compared to other areas in the Yangtze River that are probably overfished.

    DOI PubMed

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    48
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  • Feasibility study of underwater passive acoustic observations of killer whales using A-tag

    Masakazu Arima, Hirofumi Tonai, Tomonari Akamatsu, Hiroya Minakuchi

    World Automation Congress Proceedings     291 - 296  2014.10

     View Summary

    It is very important to recognise marine biodiversity and to maintain sound ocean ecosystems for long-term and continuous utilisation of the ecosystems services. To ensure this end, ocean environment and ecosystem should be monitored over the long term and a wide range of ocean areas. The purpose of this research is a feasibility study of underwater acoustic observations of marine mammals using a passive acoustic data logger, A-tag. Final goal of this research is to realise the long-term and wide-range monitoring of ocean ecosystems using autonomous underwater gliders, and to evaluate the soundness of ocean ecosystems and environments. This paper deals with underwater acoustic observations of killer whales (Orcinus orca) and analyses of their vocalisation. Underwater passive acoustic observations were conducted at the Prince William Sound, Alaska, USA in the summer of 2013. Direction of vocalisation source was analysed from the time arrival difference between two hydrophones of A-tag. It was demonstrated that the result of acoustic observations of killer whales' vocalisations agreed well with their actual behaviours by visual observations.

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  • Sound variation and function in captive Commerson's dolphins (Cephalorhynchus commersonii).

    Yayoi M Yoshida, Tadamichi Morisaka, Mai Sakai, Mari Iwasaki, Ikuo Wakabayashi, Atsushi Seko, Masahiko Kasamatsu, Tomonari Akamatsu, Shiro Kohshima

    Behavioural processes   108   11 - 9  2014.10  [Refereed]  [International journal]

     View Summary

    Commerson's dolphin (Cephalorhynchus commersonii), one of the smallest dolphin species, has been reported to produce only narrow-band high-frequency (NBHF) clicks and no whistles. To clarify their sound repertoire and examine the function of each type, we analysed the sounds and behaviour of captive Commerson's dolphins in Toba Aquarium, Japan. All recorded sounds were NBHF clicks with peak frequency >110kHz. The recorded click-trains were categorised into four types based on the changing pattern of their Inter-click intervals (ICI): Decreasing type, with continuously decreasing ICI during the last part of the train; Increasing type, with continuously increasing ICI during the last part; Fluctuating type, with fluctuating ICI; and Burst-pulse type, with very short and constant ICI. The frequency of the Decreasing type increased when approaching an object newly introduced to the tank, suggesting that the sound is used for echolocation on approach. The Burst-pulse type suddenly increased in front of the object and was often oriented towards it, suggesting that it was used for echolocation in close proximity to the object. In contrast, the Increasing type was rarely recorded during approach, but increased when a dolphin approached another dolphin. The Increasing and Burst-pulse types also increased when dolphins began social behaviours. These results suggest that some NBHF clicks have functions other than echolocation, such as communication.

    DOI PubMed J-GLOBAL

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    15
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  • Long-term passive acoustic monitoring revealed seasonal and diel patterns of cetacean presence in the Istanbul Strait

    Ayhan Dede, Ayaka Amaha Öztürk, Tomonari Akamatsu, Arda M. Tonay, Bayram Öztürk

    Journal of the Marine Biological Association of the United Kingdom   94 ( 6 ) 1195 - 1202  2014.09

     View Summary

    The Istanbul Strait (Bosphorus) is a part of the Turkish Straits System, connecting the Aegean Sea and the Black Sea. There are three cetacean species in the Strait, namely the harbour porpoise (Phocoena phocoena), the common dolphin (Delphinus delphis), and the bottlenose dolphin (Tursiops truncatus). To monitor the presence of the cetaceans, a fixed stereo passive acoustic monitoring system (A-tag) was deployed in the middle of the Strait from July 2009 to September 2010. In total 26,814 click trains were detected. Presence, direction and inter-click intervals of phonating cetaceans were measured. Most click trains were detected during the night time. Diel presence pattern was prominent in March and April. In spring, the cetaceans were concentrated in one specific direction from the fixed monitoring system. In contrast, they were found in all directions for the rest of the year. Short range sonar (inter-click intervals (ICIs) less than 50 ms) was commonly detected in spring. During the rest of the year ICIs could reach up to 150 ms. All these findings suggest that they were feeding or socializing in spring and mostly travelling in the other seasons. It is well known that pelagic fish such as sprat and bluefish start their migration from the Aegean Sea to the Black Sea in spring. This study suggests that the cetaceans use the middle part of the Strait for feeding on the pelagic fish in spring when the fish migration has just started. © 2013 Marine Biological Association of the United Kingdom .

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    20
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  • Detection of manatee feeding events by animal-borne underwater sound recorders

    Mumi Kikuchi, Tomonari Akamatsu, Daniel Gonzalez-Socoloske, Diogo A. De Souza, Leon D. Olivera-Gomez, Vera M.F. Da Silva

    Journal of the Marine Biological Association of the United Kingdom   94 ( 6 ) 1139 - 1146  2014.09

     View Summary

    Studies of the feeding behaviour of aquatic species in their natural environment are difficult, since direct observations are rarely possible. In this study, a newly developed animal-borne underwater sound recorder (AUSOMS-mini) was applied to captive Amazonian (Trichechus inunguis) and Antillean (Trichechus manatus manatus) manatees in order to directly record their feeding sounds. Different species of aquatic plants were offered to the manatees separately. Feeding sounds were automatically extracted using a custom program developed with MATLAB. Compared to ground truth data, the program correctly detected 65-79% of the feeding events, with a 7.3% or lower false alarm rate, which suggests that this methodology is a useful recorder of manatee feeding events. All manatees foraged during both the daytime and night-time. However, manatees tended to be less active and masticated slower during the night than during the day. The manatee mastication cycle duration depended on plant species and individual. This animal-borne acoustic monitoring system could greatly increase our knowledge of manatee feeding ecology by providing the exact time, duration and number of feeding events, and potentially the plant species being fed on. © 2013 Marine Biological Association of the United Kingdom .

    DOI

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    7
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  • Acoustically invisible feeding blue whales in Northern Icelandic waters

    Tomonari Akamatsu, Marianne Helene Rasmussen, Maria Iversen

    Journal of the Acoustical Society of America   136 ( 2 ) 939 - 944  2014.08

     View Summary

    Fixed passive acoustic monitoring can be used for long-term recording of vocalizing cetaceans. Both presence monitoring and animal density estimation requires the call rates and sound source levels of vocalizations produced by single animals. In this study, blue whale calls were recorded using acoustic bio-logging systems in Skjálfandi Bay off Húsavík, Northeast Iceland, in June 2012. An accelerometer was attached to individual whales to monitor diving behavior. During 21 h recording two individuals, 8 h 45 min and 13 h 2 min, respectively, 105 and 104 lunge feeding events and four calls were recorded. All recorded calls were down-sweep calls ranging from 105 to 48 Hz. The sound duration was 1-2 s. The source level was estimated to be between 158 and 169 dB re 1μPa rms, assuming spherical sound propagation from the possible sound source location to the tag. The observed sound production rates and source levels of individual blue whales during feeding were extremely small compared with those observed previously in breeding grounds. The feeding whales were nearly acoustically invisible. The function of calls during feeding remains unknown. © 2014 Acoustical Society of America.

    DOI PubMed

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    8
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  • Acoustic discrimination between harbor porpoises and delphinids by using a simple two-band comparison

    Saho Kameyama, Tomonari Akamatsu, Ayhan Dede, Ayaka Amaha Öztürk, Nobuaki Arai

    Journal of the Acoustical Society of America   136 ( 2 ) 922 - 929  2014.08

     View Summary

    A simple discrimination method between Delphinidae and Phocoenidae based on the comparison of the intensity ratios of two band frequencies (130 and 70 kHz) is proposed. Biosonar signals were recorded at the Istanbul Strait (Bosphorus) in Turkey. Simultaneously, the presence of the species was confirmed by visual observation. Two types of thresholds of two-band intensity ratios, fixed and dynamic threshold, were tested for identification. The correct detection and false alarm rates for porpoises were 0.55 and 0.06 by using the fixed threshold and 0.74 and 0.08 by using the dynamic threshold, respectively. When the dynamic threshold was employed, the appropriate threshold changed depending on the mix ratio of recorded sounds from both Delphinidae and Phocoenidae. Even under biased mix ratios from 26% to 82%, the dynamic threshold worked with >0.80 correct detection and <0.20 false alarm rates, whereas the fixed threshold did not. The proposed method is simple but quantitative, which can be applicable for any broadband recording system, including a single hydrophone with two frequency band detectors. © 2014 Acoustical Society of America.

    DOI

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    5
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  • Acoustic capture-recapture method for towed acoustic surveys of echolocating porpoises

    Satoko Kimura, Tomonari Akamatsu, Lijun Dong, Kexiong Wang, Ding Wang, Yasutoki Shibata, Nobuaki Arai

    JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA   135 ( 6 ) 3364 - 3370  2014.06  [Refereed]

     View Summary

    Passive acoustic monitoring for cetaceans mainly employ fixed-location methods or point transect samplings; an acoustic survey from a moving platform to conduct line transects is less common. In this study, acoustic capture-recapture by combining a double-observer method with line transect sampling was performed to observe Yangtze finless porpoises. Two acoustic devices were towed with the distance between them varying 0.5 to 89.5 m. The conditional probabilities that both devices would detect the porpoises within the same time window were calculated. In a 1-s time window, it became smaller as the distance between the devices increased, approaching zero when the distance between them was more than 50 m. It was considered that the devices with less than 50m distance detected the same signals from the same animals, which means the identical detection. When the distance between them is too great, the recapture rate is reduced and the incidence of false matching may increase. Thus, a separation distance of around 50m between two devices in acoustic capture-recapture of Yangtze finless porpoises was recommended. Note that the performance of the double detections can change depending on the particular device used and on animal behaviors such as vocalizing interval, ship avoidance. (C) 2014 Acoustical Society of America.

    DOI PubMed

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    6
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  • To see or not to see: Investigating detectability of ganges river dolphins using a combined visual-acoustic survey

    Nadia I. Richman, James M. Gibbons, Samuel T. Turvey, Tomonari Akamatsu, Benazir Ahmed, Emile Mahabub, Brian D. Smith, Julia P.G. Jones

    PLoS ONE   9 ( 5 )  2014.05

     View Summary

    Detection of animals during visual surveys is rarely perfect or constant, and failure to account for imperfect detectability affects the accuracy of abundance estimates. Freshwater cetaceans are among the most threatened group of mammals, and visual surveys are a commonly employed method for estimating population size despite concerns over imperfect and unquantified detectability. We used a combined visual-acoustic survey to estimate detectability of Ganges River dolphins (Platanista gangetica gangetica) in four waterways of southern Bangladesh. The combined visual-acoustic survey resulted in consistently higher detectability than a single observer-team visual survey, thereby improving power to detect trends. Visual detectability was particularly low for dolphins close to meanders where these habitat features temporarily block the view of the preceding river surface. This systematic bias in detectability during visual-only surveys may lead researchers to underestimate the importance of heavily meandering river reaches. Although the benefits of acoustic surveys are increasingly recognised for marine cetaceans, they have not been widely used for monitoring abundance of freshwater cetaceans due to perceived costs and technical skill requirements. We show that acoustic surveys are in fact a relatively cost-effective approach for surveying freshwater cetaceans, once it is acknowledged that methods that do not account for imperfect detectability are of limited value for monitoring. © 2014 Richman et al.

    DOI PubMed

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    28
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  • The Diel Rhythms of Biosonar Behavior in the Yangtze Finless Porpoise (Neophocaena asiaeorientalis asiaeorientalis) in the Port of the Yangtze River: The Correlation between Prey Availability and Boat Traffic

    Zhitao Wang, Tomonari Akamatsu, Kexiong Wang, Ding Wang

    PLOS ONE   9 ( 5 )  2014.05  [Refereed]

     View Summary

    Information on the habitat use of the critically endangered Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis) is critical for its conservation. The diel biosonar behavior of the porpoise in the port areas of the Yangtze River was examined along with simultaneous observations of fish density and boat traffic. Biosonar pulses from the porpoises were detected for 1233 min (5.77%) over a 21,380 min duration of effective observations. In total, 190 (5.63%) buzzes (an indication of prey capture attempts) were recorded among the 3372 identified click trains. Of the 168 echolocation encounters (bouts of click trains less than eight min apart), 150 (89.3%) involved single animals, indicating that solitary porpoises were frequently present and feeding in the port areas. Significant diel patterns were evident involving the biosonar behavior of the porpoises (including click trains and buzzes), fish density and boat traffic. The frequencies of the click trains and buzzes were significantly lower during the day than in the evening and at night, which suggests that porpoises in this region are primarily engaged in crepuscular and nocturnal foraging. The lack of a significant diel pattern in the echolocation encounters indicates the importance of the port in porpoise conservation. A forced feeding schedule may be associated with the lack of a significant correlation between porpoise acoustics and boat traffic. Overall, prey availability appears to be the primary factor that attracts porpoises. Additionally, porpoises tend to migrate or remain downstream in the morning and migrate or remain upstream in the evening, most likely to follow their prey. The findings of this study can be used to improve the conservation of the Yangtze finless porpoise.

    DOI PubMed

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    46
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  • An Evaluation of the Performance of a hydrophone on sea floor

    Shuhei Nishida, Katsuyoshi Kawaguchi, Tomohito Imaizumi, Tomonari Akamatsu

    OCEANS 2014 - TAIPEI    2014  [Refereed]

     View Summary

    DONET (Dense Ocean-floor Network system for Earthquakes and Tsunamis) is a submarine cabled real-time observation network for earthquakes and tsunamis monitoring around the Nankai trough, southwestern Japan. The scheduled twenty observatories have operated since August 2011. Various sensors such as a broadband seismometer, a pressure gauge, a hydrophone, etc. are equipped with each observatory, because DONET has expected to obtain the data to understand the Nankai trough mega thrust earthquake seismogenic zones. Therefore, in order to supply data stably, it's important to have a method of an investigation of the performance of each sensor in DONET.
    In this research, we will evaluate the performance of a hydrophone of DONET. The reference hydrophone was installed several meters from an observatory of DONET. Here, it assumes that both hydrophones will record the acoustic data according to same sound source. And, we will evaluate the performance of a hydrophone by the comparison between reference hydrophone and DONET's one in actual field, and will report the result of the evaluations.

    DOI

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  • Distribution patterns of Yangtze finless porpoises in the Yangtze River: Implications for reserve management

    X. Zhao, D. Wang, S. T. Turvey, B. Taylor, T. Akamatsu

    Animal Conservation   16 ( 5 ) 509 - 518  2013.10

     View Summary

    The Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis) is a highly threatened cetacean endemic to the middle and lower reaches of the Yangtze River that has suffered a dramatic decline in recent decades. We characterize and quantify recent distribution patterns of porpoises in the Yangtze River in order to facilitate strategic management of existing in situ cetacean reserves and maximize effective utilization of limited conservation resources. We calculated porpoise relative abundance (encounter rate) using a 1-km moving average along the Yangtze main stem based on a combined visual and acoustic survey conducted in 2006. We then evaluated conservation priority areas based on encounter rates along the river. High-porpoise density areas (>0.20porpoiseskm-1) cover approximately one-third (33.9%, 599km) of the survey area and contain approximately two-thirds of the porpoise population, making them priority areas for porpoise conservation. In contrast, low-porpoise density areas (≤0.05porpoiseskm-1) cover 28.8% (509km) of the survey area but contain only 4.5% of the porpoise population, and may already be of little value for porpoise conservation. Five high-priority porpoise conservation sites and five sections that now contain few or no surviving porpoises are identified. Proposed spatial modifications to existing reserves and associated conservation recommendations are made for five existing protected areas along the Yangtze main stem, and we emphasize that some additional river sections should urgently be designated as new protected areas given their high porpoise density. Our approach for identifying conservation priorities may provide lessons for reserve design and management in other protected area networks. © 2013 The Zoological Society of London.

    DOI

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    42
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  • Diel changes in the movement patterns of Ganges River dolphins monitored using stationed stereo acoustic data loggers

    Yukiko Sasaki-Yamamoto, Tomonari Akamatsu, Tamaki Ura, Harumi Sugimatsu, Junichi Kojima, Rajendar Bahl, Sandeep Behera, Shiro Kohshima

    MARINE MAMMAL SCIENCE   29 ( 4 ) 589 - 605  2013.10  [Refereed]

     View Summary

    We monitored the underwater movements of Ganges River dolphins using stationed stereo acoustic data loggers. We estimated these movements using changes in the relative angle of the sound source direction (trajectory). Of the total acoustic recordings (66h), 26.2% contained trajectories of dolphins, and 78.6% of these trajectories involved single animals, suggesting that dolphins tended to swim alone and were localized near the monitoring station. The observed trajectories were categorized as follows: staying type characterized by small changes in the sound source direction, moving type A (moving in the same direction), and moving type B (moving up and down the stream during recording). The average interpulse intervals of sounds in moving types A and B were significantly shorter than that of the staying type, suggesting that dolphins produce the former types of trajectories to echolocate across shorter distances during movement. The frequency of occurrence of moving type A increased during the night, whereas that of type B increased in the late afternoon and that of the staying type increased during the daytime. These results indicate that dolphins moving at night tended to use short-range echolocation, whereas during the day, they remained in relatively small areas and used long-range sonar.

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  • An automatic detection algorithm for extracting the representative frequency of cetacean tonal sounds

    Tzu-Hao Lin, Lien-Siang Chou, Tomonari Akamatsu, Hsiang-Chih Chan, Chi-Fang Chen

    JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA   134 ( 3 ) 2477 - 2485  2013.09  [Refereed]

     View Summary

    Most studies on tonal sounds extract contour parameters from fundamental frequencies. The presence of harmonics and the frequency distribution of multiple tonal sounds have not been well researched. To investigate the occurrence and frequency modulation of cetacean tonal sounds, the procedure of detecting the instantaneous frequency bandwidth of tonal spectral peaks was integrated within the local-max detector to extract adopted frequencies. The adopted frequencies, considered the representative frequencies of tonal sounds, are used to find the presence of harmonics and overlapping tonal sounds. The utility and detection performance are demonstrated on acoustic recordings of five species from two databases. The recordings of humpback dolphins showed a 75% detection rate with a 5% false detection rate, and recordings from the MobySound archive showed an 85% detection rate with a 5% false detection rate. These detections were achieved in signal-to-noise ratios of -12 to 21 dB. The parameters that measured the distribution of adopted frequency, as well as the prominence of harmonics and overlaps, indicate that the modulation of tonal sounds varied among different species and behaviors. This algorithm can be applied to studies on cetacean communication signals and long-term passive acoustic monitoring. (C) 2013 Acoustical Society of America.

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  • A multimodal detection model of dolphins to estimate abundance validated by field experiments

    Akamatsu Tomonari, Ura Tamaki, Sugimatsu Harumi, Bahl Rajendar, Behera Sandeep, Panda Sudarsan, Khan Muntaz, Kar S. K, Kar C. S, Kimura Satoko, Sasaki-Yamamoto Yukiko

    JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA   134 ( 3 ) 2418 - 2426  2013.09  [Refereed]

     View Summary

    Abundance estimation of marine mammals requires matching of detection of an animal or a group of animal by two independent means. A multimodal detection model using visual and acoustic cues (surfacing and phonation) that enables abundance estimation of dolphins is proposed. The method does not require a specific time window to match the cues of both means for applying mark-recapture method. The proposed model was evaluated using data obtained in field observations of Ganges River dolphins and Irrawaddy dolphins, as examples of dispersed and condensed distributions of animals, respectively. The acoustic detection probability was approximately 80%, 20% higher than that of visual detection for both species, regardless of the distribution of the animals in present study sites. The abundance estimates of Ganges River dolphins and Irrawaddy dolphins fairly agreed with the numbers reported in previous monitoring studies. The single animal detection probability was smaller than that of larger cluster size, as predicted by the model and confirmed by field data. However, dense groups of Irrawaddy dolphins showed difference in cluster sizes observed by visual and acoustic methods. Lower detection probability of single clusters of this species seemed to be caused by the clumped distribution of this species. © 2013 Acoustical Society of America.

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  • Tidal influences on the habitat use of Indo-Pacific humpback dolphins in an estuary

    Tzu Hao Lin, Tomonari Akamatsu, Lien Siang Chou

    Marine Biology   160 ( 6 ) 1353 - 1363  2013.06

     View Summary

    This paper offers the first study of diurnal variations in the use of an estuarine habitat by Indo-Pacific humpback dolphins. Passive acoustic data loggers were deployed in the Xin Huwei River Estuary, Western Taiwan, from July 2009 to December 2010, to collect biosonar clicks. Acoustic encounter rates of humpback dolphins on the riverside of the estuary changed significantly over the four tidal phases, instead of the two diurnal phases based on the recordings from 268 days. Among the tidal phases, the encounter rates were lowest during ebb tides. Additionally, circling movements associated with the hunt for epipelagic fish significantly changed in temporal and spatial presence over the four tidal phases, matching the overall pattern of encounter rate changes in the focal estuary. Our findings suggest that the occurrence pattern and habitat utilization of humpback dolphins are likely to be influenced by the tidal-driven activity of their epipelagic prey. © 2013 Springer-Verlag Berlin Heidelberg.

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  • Variation in the production rate of biosonar signals in freshwater porpoises

    Kimura Satoko, Akamatsu Tomonari, Wang Ding, Li Songhai, Wang Kexiong, Yoda Ken

    JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA   133 ( 5 ) 3128 - 3134  2013.05  [Refereed]

     View Summary

    The biosonar (click train) production rate of ten Yangtze finless porpoises and their behavior were examined using animal-borne data loggers. The sound production rate varied from 0 to 290 click trains per 10-min time interval. Large individual differences were observed, regardless of body size. Taken together, however, sound production did not differ significantly between daytime and nighttime. Over the 172.5 h of analyzed recordings, an average of 99.0% of the click trains were produced within intervals of less than 60 s, indicating that during a 1-min interval, the number of click trains produced by each porpoise was typically greater than one. Most of the porpoises exhibited differences in average swimming speed and depth between day and night. Swimming speed reductions and usage of short-range sonar, which relates to prey-capture attempts, were observed more often during nighttime. However, biosonar appears to be affected not only by porpoise foraging, but also by their sensory environment, i.e., the turbid Yangtze River system. These features will be useful for passive acoustic detection of the porpoises. Calculations of porpoise density or abundance should be conducted carefully because large individual differences in the sound production rate will lead to large estimation error. (C) 2013 Acoustical Society of America.

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  • Biosonar, diving and movements of two tagged white-beaked dolphin in Icelandic waters

    M. H. Rasmussen, T. Akamatsu, J. Teilmann, G. Vikiugsson, L. A. Miller

    DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY   88-89   97 - 105  2013.04  [Refereed]

     View Summary

    For the first time bio-logging tags were attached to free-ranging white-beaked dolphins, Lagenorhynchus albirostris. A satellite tag was attached to one animal while an acoustic A-tag, a time-depth recorder and a VHF transmitter complex was attached to a second dolphin with a suction cup. The satellite tag transmitted for 201 day, during which time the dolphin stayed in the coastal waters of western Iceland. The acoustic tag complex was on the second animal for 13 h and 40 min and provided the first insight into the echolocation behaviour of a free-ranging white-beaked dolphin. The tag registered 162 dives. The dolphin dove to a maximum depth of 45 m, which is about the depth of the bay in which the dolphin was swimming. Two basic types of dives were identified; U-shaped and V-shaped dives. The dolphin used more time in U-shaped dives, more clicks and sonar signals with shorter click intervals compared to those it used in V-shaped dives. The dolphin was in acoustic contact with other dolphins about five hours after it was released and stayed with these for the rest of the tagging time. Possible foraging attempts were found based on the reduction of click intervals from about 100 ms to 2-3 ms, which suggests a prey capture attempt. We found 19 punitive prey capture attempts and of these 53% occurred at the maximum dive depth. This suggests that more than half of the possible prey capture events occurred at or near the sea bed. (C) 2012 Elsevier Ltd. All rights reserved.

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  • Biosonar, dive, and foraging activity of satellite tracked harbor porpoises (Phocoena phocoena)

    Meike Linnenschmidt, Jonas Teilmann, Tomonari Akamatsu, Rune Dietz, Lee A. Miller

    MARINE MAMMAL SCIENCE   29 ( 2 ) E77 - E97  2013.04  [Refereed]

     View Summary

    This study presents bioacoustic recordings in combination with movements and diving behavior of three free-ranging harbor porpoises (a female and two males) in Danish waters. Each porpoise was equipped with an acoustic data logger (A-tag), a time-depth-recorder, a VHF radio transmitter, and a satellite transmitter. The units were programmed to release after 24 or 72h. Possible foraging occurred mostly near the surface or at the bottom of a dive. The porpoises showed individual diversity in biosonar activity (&lt;100 to &gt;50,000 clicks per hour) and in dive frequency (6179 dives per hour). We confirm that wild harbor porpoises use more intense clicks than captive animals. A positive tendency between number of dives and clicks per hour was found for a subadult male, which stayed near shore. It showed a distinct day-night cycle with low echolocation rates during the day, but five times higher rates and higher dive activity at night. A female traveling in open waters showed no diel rhythm, but its sonar activity was three times higher compared to the males'. Considerable individual differences in dive and echolocation activity could have been influenced by biological and physical factors, but also show behavioral adaptability necessary for survival in a complex coastal environment.

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  • Observation of in situ tuna behavior around the fisheries aggregating devises (FADs) by using passive and active acoustic methods

    T. Imaizumi, T. Akamatsu, T. Oshima, K. Yokota, H. Iga, I. Fusejima, Y. Wang, M. Ito, I. Matsuo, Y. Takao, S. Hasegawa

    2013 IEEE International Underwater Technology Symposium, UT 2013    2013

     View Summary

    The by-catch of bigeye tuna (Thunnus obesus) has been serious problem for commercial fisheries of skip jack tuna (Katsuwonus pelamis) due to the strong constrain of quarter for each species. Selective catch of skip jack tuna with avoiding by-catch of bigeye tuna is required for sustainable and effective fisheries. Light stimuli were applied in attempts to remove unnecessary tuna species and let them escape through the mesh or underneath of a round net. The movements of fish were observed with coded pingers (passive method) and a broadband quantitative split-beam echo sounder (active method). Newly introduced micro coded pinger (Fusion Inc., Tokyo) for this observation resulted in longer survival or / and retention of tagged fish comparing with previous survey periods. Three hydrophone array systems were deployed on each survey ships (Shoyo-maru, Nippon-maru, and Nippon-maru's boat). The pinger transmitted 31 bits M-sequence signal every 1 second. Movements of multiple tagged fish were able to be observed at the same time. Not only depth change of each fish, but also three dimensional locations could be calculated. In the mean time, schools of fish were observed by the broadband echo sounder near the FADs. The 3D tracks of fishes which were estimated by active way with high distance resolution showed the fish swam deeper at sun rising that was consistent with passive monitoring result. Consequently large data sets of the movement of in situ bigeye tuna and skipjack tuna around FADs were obtained. © 2013 IEEE.

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  • Counting animals using vocalizations; A case study in dolphins

    T. Akamatsu, T. Ura, H. Sugimatsu, R. Bahl, S. Behera, S. Panda, M. Khan, S. K. Kar, C. S. Kar, S. Kimura, Y. Sasaki-Yamamoto

    2013 IEEE International Underwater Technology Symposium, UT 2013    2013

     View Summary

    Abundance estimation of marine mammals requires matching of detection of an animal or a group of animals by two independent means. A multimodal detection model using visual and acoustic cues (surfacing and phonation) that enables abundance estimation of dolphins is proposed. The method does not require a specific time window to match the cues of both means for applying mark-recapture method. The proposed model was evaluated using data obtained in field observations of Ganges River dolphins and Irrawaddy dolphins, as examples of dispersed and condensed distributions of animals, respectively. The acoustic detection probability was approximately 80 %, 20 % higher than that of visual detection for both species, regardless of the distribution of the animals in the present study sites. The abundance estimates of Ganges River dolphins and Irrawaddy dolphins fairly agreed with the numbers reported in previous monitoring studies. The single animal detection probability was smaller than that of larger cluster size, as predicted by the model and confirmed by field data. However, dense groups of Irrawaddy dolphins showed difference in cluster sizes observed by visual and acoustic methods. Lower detection probability of single clusters of this species seemed to be caused by the clumped distribution of this species. © 2013 IEEE.

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    3
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  • An evaluation about the performance of a hydrophone on seafloor

    S. Nishida, K. Kawaguchi, T. Imaizumi, T. Akamatsu

    2013 IEEE International Underwater Technology Symposium, UT 2013    2013

     View Summary

    DONET (Dense Ocean-floor Network system for Earthquakes and Tsunamis) is a submarine cabled real-time observation network for earthquakes and tsunamis monitoring around the Nankai trough, southwestern Japan. The scheduled twenty observatories have operated since August 2011. Various sensors such as a broadband seismometer, a pressure gauge, a hydrophone, etc. are equipped with each observatory, because DONET has expected to obtain the data to understand the Nankai trough mega thrust earthquake seismogenic zones. Therefore, in order to supply data stably, it's important to have a method of an investigation of the performance of each sensor in DONET. In this research, we will evaluate the performance of a hydrophone of DONET. The reference hydrophone was installed several meters from an observatory of DONET. Here, it assumes that both hydrophones will record the acoustic data according to same sound source. And, we will evaluate the performance of a hydrophone by the comparison between reference hydrophone and DONET's one in actual field, and will report the result of the evaluations. © 2013 IEEE.

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  • Classification of fish schools based on acoustic features associated with tilt angle

    M. Ito, I. Matsuo, T. Imaizumi, T. Akamatsu, Y. Wang, Y. Nishimori

    2013 IEEE International Underwater Technology Symposium, UT 2013    2013

     View Summary

    It is required to monitor fish species and amount in order to save marine resources. In the current study, broadband split-beam echo sounder was used to survey fish resources. The echo sounder was useful to track individual fish in schools because individual fish echoes in the schools could be separately measured and three dimensional positions of the echoes could be accurately estimated. It is well known that the acoustic features of fish echoes are closely related to the body length and the apparent tilt angle of a fish. The tilt angle could be estimated by individual tracking. Echoes from fish schools were measured for several hours in the ocean. Echo signals were gathered into one block within a certain depth and a period of time and analyzed to track individual fish in the schools. Target strength was calculated from the individual fish echo and associated with the tilt angle, which was estimated by the individual tracking result. The feature in each block was statistically calculated by averaging target strengths based on the tilt angles. The blocks of the signals were classified by K-means method with the features and divided into some clusters. As a result of the clustering, fish schools in the blocks could be classified. The distribution of the clusters was dependent on both time and depth. © 2013 IEEE.

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  • Algorithm for automatic acoustic detection of ship and marine mammals

    Akiko Sakurada, Tomonari Akamatsu, Naoya Umeda

    IFAC Proceedings Volumes (IFAC-PapersOnline)   9 ( PART 1 ) 352 - 355  2013

     View Summary

    Responding to the increasing number, size, and speed of commercial ships, the underwater noise is also increasing which could result in a possible adverse impact on marine lives. For clarifying this possible concern, a method for measurement of ship noise and marine lives is required, especially for marine mammals which are sensitive for the frequency range of ship noise. In order to enable to observe marine mammal's behavior and the ship noise simultaneously, this study developed an algorithm to detect ship noise, added to a conventional dolphin detection algorithm. The ship noise is obtained by eliminating some nature sounds and the dolphin's sonar sound. Both dolphin's sounds and ship noises can be separated efficiently so that the noise can be identified using sample data. Further improvement of monitoring system and algorithm are future tasks. © IFAC.

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  • Clustering of acoustic fish features tracked by broadband split-beam echo sounder

    Masanori Ito, Ikuo Matsuo, Tomohito Imaizumi, Tomonari Akamatsu, Yong Wang, Yasushi Nishimori

    Proceedings of Meetings on Acoustics   19  2013  [Refereed]

     View Summary

    Monitoring fish species and amount with acoustical instruments is a challenging problem to survey fish resources in the ocean. Broadband split-beam echo sounder was useful to observe individual fish behavior in schools. Echoes from fish schools were measured from an anchored vessel for several hours. Echo signals were gathered into one block within a certain depth and a period of time and analyzed to track individual fish in the schools. Target strength was calculated from the individual fish echo and associated with tilt angle which could be estimated by using the tracking result. Feature in each block was statistically calculated by averaging target strengths according to the tilt angles. The blocks of the signals were clustered by K-means method with the features and divided into some clusters. The distribution of the clusters in time and depth was investigated. It appeared that the distributions of the clusters were dependent on both time and depth. Clustering of the features would be effective to monitor diversity of fish in the ocean. © 2013 Acoustical Society of America.

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  • First human-caused extinction of a cetacean species?

    Samuel T. Turvey, Robert L. Pitman, Barbara L. Taylor, Jay Barlow, Tomonari Akamatsu, Leigh A. Barrett, Xiujiang Zhao, Randall R. Reeves, Brent S. Stewart, Kexiong Wang, Zhuo Wei, Xianfeng Zhang, L. T. Pusser, Michael Richlen, John R. Brandon, Ding Wang

    Biology Letters   3 ( 5 ) 537 - 540  2012.10  [Refereed]

     View Summary

    The Yangtze River dolphin or baiji (Lipotes vexillifer), an obligate freshwater odontocete known only from the middle-lower Yangtze River system and neighbouring Qiantang River in eastern China, has long been recognized as one of the world's rarest and most threatened mammal species. The status of the baiji has not been investigated since the late 1990s, when the surviving population was estimated to be as low as 13 individuals. An intensive six-week multivessel visual and acoustic survey carried out in November-December 2006, covering the entire historical range of the baiji in the main Yangtze channel, failed to find any evidence that the species survives. We are forced to conclude that the baiji is now likely to be extinct, probably due to unsustainable by-catch in local fisheries. This represents the first global extinction of a large vertebrate for over 50 years, only the fourth disappearance of an entire mammal family since AD 1500, and the first cetacean species to be driven to extinction by human activity. Immediate and extreme measures may be necessary to prevent the extinction of other endangered cetaceans, including the sympatric Yangtze finless porpoise (Neophocaena phocaenoides asiaeorientalis). © 2007 The Royal Society.

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  • Seasonal changes in the local distribution of Yangtze finless porpoises related to fish presence

    Kimura Satoko, Akamatsu Tomonari, Li Songhai, Dong Lijun, Wang Kexiong, Wang Ding, Arai Nobuaki

    MARINE MAMMAL SCIENCE   28 ( 2 ) 308 - 324  2012.04  [Refereed]

     View Summary

    The Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis) is an endangered freshwater porpoise subspecies unique to the Yangtze River basin. Seasonal variations in local distribution of the animal, as well as fish presence, sand dredging, ship navigation, and bridges were examined as potential factors affecting the occurrence of the animals. Passive acoustic surveys were performed regularly from May 2007 to August 2010, near the conjunction of the Yangtze River and Poyang Lake. The distribution of the porpoises was seasonally site-specific. In May and August, the animals were detected more often at river junctions than in the lake, but vice versa from November to February. The rate of the porpoise detection was significantly higher in areas of fish presence than in areas of absence. The number of porpoises detected did not differ significantly between the sand dredging operation and the prohibition period (in 2008), although the number of vessels obviously declined in 2008. Ship traffic and bridges also did not appear to affect the presence of porpoises. These results showed the relative importance of the various environmental factors, which is important for conservation of not only Yangtze finless porpoise but also endangered isolated cetaceans. © 2011 by the Society for Marine Mammalogy.

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  • Clumped distribution of vocalising dugongs (Dugong dugon) monitored by passive acoustic and visual observations in Thai waters

    Kotaro Ichikawa, Tomonari Akamatsu, Tomio Shinke, Nobuaki Arai, Kanjana Adulyanukosol

    Australian Acoustical Society Conference 2012, Acoustics 2012: Acoustics, Development, and the Environment     529 - 532  2012

     View Summary

    Distribution pattern of dugongs is a key component for space-based managements. Vocal interaction of dugongs may result in a distinctive distribution pattern. This study described the distribution patterns of vocalising dugongs, solitary and cow-calf pairs of dugongs. Total of 31 hours and 24 minutes of aerial surveys over southern Thai waters were conducted to observe distribution of the dugongs in 2006, 2008 and 2010. We also conducted towed acoustic surveys to observe the distribution of vocalising dugongs. Total of 473 adult dugongs and 122 calves and 223 vocalizations were found. The distribution of vocalising dugongs was clumped with the range of about 1 km 2. Groups with cow-calf pairs (9 animals on average) were also clumped. Their distribution range was about 3 km2 and did not overlap that of vocalising dugongs. Average number of individuals in groups without cow-calf pairs was about 1, indicating that the most of the group members were solitary. They distributed widely throughout the focal area with the distribution range of about 41 km2.

  • Cepstral analysis for discrimination of fish species by using the dolphin-like sonar sounds

    I. Matsuo, M. Ito, T. Imaizumi, T. Akamatsu, Y. Wang, Y. Nishimori

    11th European Conference on Underwater Acoustics 2012, ECUA 2012   34 1 ( PART 3 ) 496 - 500  2012

     View Summary

    The broadband target strength (TS) pattern could be estimated from echoes of the tethered fish by using the broadband signal. This TS pattern was computed by Fourier transform from outputs of cross-correlation function between the emitted signal and echoes from each fish at each tilt angle. Since echoes from fish included multiple reflections, the TS spectra included the interferences among them, as shown in Fig. 4. The degrees of these interferences could be computed by the average of enveloped cepstral patterns at the time, which is larger than 25 microseconds, corresponding to 18 mm along the range axis. As shown in Fig. 5 (b), these degrees were different with four species at the negative tilt angles while these were almost same with them at the positive tilt angles. As shown in Fig.5 (a), it was clarified that averaged TS was changed dependent on fish species and tilt angles.

  • Zigzag transect survey by towed passive acoustic method for finless porpoise in the Yangtze River.

    Kimura Satoko, Akamatsu Tomonari, Li Songhai, Dong Shouyue, Wang Kexiong, Wang Ding, Arai Nobuaki

    Proceedings of the 7th International Symposium on SEASTAR2000 and Asian Bio-logging Science.     37 - 41  2012  [Refereed]

  • Do Porpoises Choose Their Associates? A New Method for Analyzing Social Relationships among Cetaceans

    Mai Sakai, Ding Wang, Kexiong Wang, Songhai Li, Tomonari Akamatsu

    PLOS ONE   6 ( 12 ) e28836  2011.12  [Refereed]

     View Summary

    Background: Observing and monitoring the underwater social interactions of cetaceans is challenging. Therefore, previous cetacean studies have monitored these interactions by surface observations. However, because cetaceans spend most of their time underwater, it is important that their underwater behavior is also continuously monitored to better understand their social relationships and social structure. The finless porpoise is small and has no dorsal fin. It is difficult to observe this species in the wild, and little is known of its sociality.
    Methodology/Principal Findings: The swim depths of 6 free-ranging finless porpoises were simultaneously recorded using a time-synchronized bio-logging system. Synchronous diving was used as an index of association. Two pairs, # 27 (an immature female estimated to be 3.5 years old) and # 32 (an adult male), # 28 (a juvenile male estimated to be 2 years old) and # 29 (an adult male), tended to participate in long periods of synchronized diving more frequently than 13 other possible pairs, indicating that the 4 porpoises chose their social partners. The adult males (# 32, # 29) tended to follow the immature female (# 27) and juvenile male (# 28), respectively. However, during synchronized diving, the role of an initiator often changed within the pair, and their body movements appeared to be non-agonistic, e. g., rubbing of bodies against one another instead of that on one-side, as observed with chasing and escaping behaviors.
    Conclusions/Significance: The present study employed a time-synchronized bio-logging method to observe the social relationships of free-ranging aquatic animals based on swimming depth. The results suggest that certain individuals form associations even if they are not a mother and calf pair. Long synchronized dives occurred when particular members were reunited, and this suggests that the synchronized dives were not a by-product of opportunistic aggregation.

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  • Passive acoustic survey of Yangtze finless porpoises using a cargo ship as a moving platform

    Lijun Dong, Ding Wang, Kexiong Wang, Songhai Li, Shouyue Dong, Xiujiang Zhao, Tomonari Akamatsu, Satoko Kimura

    JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA   130 ( 4 ) 2285 - 2292  2011.10  [Refereed]

     View Summary

    In order to periodically investigate the population and distribution of the Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis) in its main distribution range in the Yangtze River, a passive acoustic system deployed on a cargo ship as a moving platform, rather than a dedicated research ship, was developed. A stereo acoustic event data-logger (A-tag) was installed on the cargo ship to passively detect phonating animals. In three surveys carried out in the Yangtze River from Wuhan to Shanghai, an average of 6059 clicks in each survey and 284 porpoises in total were acoustically detected along an 1100-km stretch. The animals were detected frequently in most of the survey range except two "gap sections" with 40 and 60 km lengths, respectively, where no animals were detected in all three surveys. Detected group sizes of the animals in each 120-s time window were not significantly different among the surveys, but the distribution pattern was different and suggested seasonal migration. The cargo ship based passive acoustic survey was effective in detecting phonating animals and can potentially monitor the distribution and population trend over time. Compared to surveys that used dedicated research ships, the present method is more cost effective. (C) 2011 Acoustical Society of America. [DOI: 10.1121/1.3625257]

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  • An international quiet ocean experiment

    Ian L. Boyd, George Frisk, Ed Urban, Peter Tyack, Jesse Ausubel, Sophie Seeyave, Doug Cato, Brandon Southal, Michael Weise, Rex Andrew, Tomonari Akamatsu, René Deke Ling, Christine Erbe, David Farmer, Roger Gentry, Tom Gross, Anthony Hawkins, Fenghua Li, Kathy Metcalf, James H. Miller, David Moretti, Cristian Rodrigo, Tomio Shinke

    Oceanography   24 ( 2 ) 174 - 181  2011.06

     View Summary

    The effect of noise on marine life is one of the big unknowns of current marine science. Considerable evidence exists that the human contribution to ocean noise has increased during the past few decades: human noise has become the dominant component of marine noise in some regions, and noise is directly correlated with the increasing industrialization of the ocean. Sound is an important factor in the lives of many marine organisms, and theory and increasing observations suggest that human noise could be approaching levels at which negative effects on marine life may be occurring. Certain species already show symptoms of the effects of sound. Although some of these effects are acute and rare, chronic sublethal effects may be more prevalent, but are difficult to measure. We need to identify the thresholds of such effects for different species and be in a position to predict how increasing anthropogenic sound will add to the effects. To achieve such predictive capabilities, the Scientific Committee on Oceanic Research (SCOR) and the Partnership for Observation of the Global Oceans (POGO) are developing an International Quiet Ocean Experiment (IQOE), with the objective of coordinating the international research community to both quantify the ocean sound scape and examine the functional relationship between sound and the viability of key marine organisms. SCOR and POGO will convene an open science meeting to gather community input on the important research, observations, and modeling activities that should be included in IQOE. © 2011 by The Oceanography Society. All rights reserved.

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  • Callback response of dugongs to conspecific chirp playbacks

    Kotaro Ichikawa, Tomonari Akamatsu, Tomio Shinke, Kanjana Adulyanukosol, Nobuaki Arai

    JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA   129 ( 6 ) 3623 - 3629  2011.06  [Refereed]

     View Summary

    Dugongs (Dugong dugon) produce bird-like calls such as chirps and trills. The vocal responses of dugongs to playbacks of several acoustic stimuli were investigated. Animals were exposed to four different playback stimuli: a recorded chirp from a wild dugong, a synthesized down-sweep sound, a synthesized constant-frequency sound, and silence. Wild dugongs vocalized more frequently after playback of broadcast chirps than that after constant-frequency sounds or silence. The down-sweep sound also elicited more vocal responses than did silence. No significant difference was found between the broadcast chirps and the down-sweep sound. The ratio of wild dugong chirps to all calls and the dominant frequencies of the wild dugong calls were significantly higher during playbacks of broadcast chirps, down-sweep sounds, and constant-frequency sounds than during those of silence. The source level and duration of dugong chirps increased significantly as signaling distance increased. No significant correlation was found between signaling distance and the source level of trills. These results show that dugongs vocalize to playbacks of frequency-modulated signals and suggest that the source level of dugong chirps may be manipulated to compensate for transmission loss between the source and receiver. This study provides the first behavioral observations revealing the function of dugong chirps. (C) 2011 Acoustical Society of America. [DOI: 10.1121/1.3586791]

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  • Echolocation signals of Heaviside's dolphins (Cephalorhynchus heavisidii)

    Tadamichi Morisaka, Leszek Karczmarski, Tomonari Akamatsu, Mai Sakai, Steve Dawson, Meredith Thornton

    Journal of the Acoustical Society of America   129 ( 1 ) 449 - 457  2011.01  [Refereed]  [International journal]

     View Summary

    Field recordings of echolocation signals produced by Heaviside's dolphins (Cephalorhynchus heavisidii) were made off the coast of South Africa using a hydrophone array system. The system consisted of three hydrophones and an A-tag (miniature stereo acoustic data-logger). The mean centroid frequency was 125 kHz, with a -3 dB bandwidth of 15 kHz and -10 dB duration of 74 s. The mean back-calculated apparent source level was 173 dB re 1 Pa p.-p.. These characteristics are very similar to those found in other Cephalorhynchus species, and such narrow-band high-frequency echolocation clicks appear to be a defining characteristic of the Cephalorhynchus genus. Click bursts with very short inter-click intervals (up to 2 ms) were also recorded, which produced the cry sound reported in other Cephalorhynchus species. Since inter-click intervals correlated positively to click duration and negatively to bandwidth, Heaviside's dolphins may adjust their click duration and bandwidth based on detection range. The bimodal distribution of the peak frequency and stable bimodal peaks in spectra of individual click suggest a slight asymmetry in the click production mechanism. © 2011 Acoustical Society of America.

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  • Preliminary evaluation of underwater sound detection by the cephalopod statocyst using a forced oscillation model

    Kenzo Kaifu, Tomonari Akamatsu, Susumu Segawa

    Acoustical Science and Technology   32 ( 6 ) 255 - 260  2011  [Refereed]

     View Summary

    To understand the mechanism of the peripheral auditory system of the cephalopod statocyst, the frequency dependence of particle motion sensitivity in cephalopods was estimated using a physical model of the sensory system, which was assumed to be forced oscillation. Reported perception thresholds of Sepia officinalis, Octopus vulgaris, and O. ocellatus fit the model well at low frequencies, whereas at frequencies above 150 Hz, the empirically measured threshold increased more steeply than the predicted increment. These results indicate that the frequency response of the perception threshold of cephalopods to particle motion can be primarily understood using the forced oscillation model, while unknown factor(s) play a role in the higher frequency range. Cephalopods are thought to be sensitive to low-frequency particle motion rather than high-frequency motion. The evolutionary function of cephalopod acoustical perception is not clear
    however, the data suggest that they recognize the low-frequency particle motion that may be generated by prey, predators, and conspecifics. © 2011 The Acoustical Society of Japan.

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    7
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  • A stereo acoustic event recorder for monitoring abundance and movements of dolphins and porpoises

    Tomonari Akamatsu, Satoko Kimura, Songhai Li, Lijun Dong, Kexiong Wang, Ding Wang

    2011 IEEE Symposium on Underwater Technology, UT'11 and Workshop on Scientific Use of Submarine Cables and Related Technologies, SSC'11    2011  [Refereed]

     View Summary

    A multi-platform ultrasonic event recorder for towing and stationed monitoring of cetaceans was developed. A stereo acoustic event recorder (A-tag) was originally developed to observe biosonar behavior by tagging on dolphins and porpoises in the wild. In recent years, A-tag has been applied for the acoustic transect to count the number of dolphins and porpoises, and for the long term stationed observation. © 2011 IEEE.

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    3
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  • Density estimation of Yangtze finless porpoises using passive acoustic sensors and automated click train detection

    Kimura Satoko, Akamatsu Tomonari, Li Songhai, Dong Shouyue, Dong Lijun, Wang Kexiong, Wang Ding, Arai Nobuaki

    JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA   128 ( 3 ) 1435 - 1445  2010.09  [Refereed]

     View Summary

    A method is presented to estimate the density of finless porpoises using stationed passive acoustic monitoring. The number of click trains detected by stereo acoustic data loggers (A-tag) was converted to an estimate of the density of porpoises. First, an automated off-line filter was developed to detect a click train among noise, and the detection and false-alarm rates were calculated. Second, a density estimation model was proposed. The cue-production rate was measured by biologging experiments. The probability of detecting a cue and the area size were calculated from the source level, beam patterns, and a sound-propagation model. The effect of group size on the cue-detection rate was examined. Third, the proposed model was applied to estimate the density of finless porpoises at four locations from the Yangtze River to the inside of Poyang Lake. The estimated mean density of porpoises in a day decreased from the main stream to the lake. Long-term monitoring during 466 days from June 2007 to May 2009 showed variation in the density 0-4.79. However, the density was fewer than 1 porpoise/ km2 during 94% of the period. These results suggest a potential gap and seasonal migration of the population in the bottleneck of Poyang Lake. © 2010 Acoustical Society of America.

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  • Widespread passive acoustic detection of Yangtze finless porpoise using miniature stereo acoustic data-loggers: A review

    Li Songhai, Akamatsu Tomonari, Dong Lijun, Wang Kexiong, Wang Ding, Kimura Satoko

    JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA   128 ( 3 ) 1476 - 1482  2010.09  [Refereed]

     View Summary

    Data on distribution, abundance, ecology, and behavior are essential for conservation and management of endangered animals in the wild. Yangtze finless porpoise (Neophocaena phocaenoides asiaeorientalis) is an endangered small odontocete species, living exclusively in the Yangtze River and its connecting Poyang and Dongting Lakes. Frequent production of high-frequency bio-sonar signals allows the animal to be detectable using passive acoustic methods. Recently, a stereo acoustic event data-logger (A-tag) has been used extensively to detect the animal by using both fixed and mobile platforms. The passive acoustic monitoring methods were not only successful in detecting the presence of animals, but also in counting, localizing, and tracking phonating individuals. Underwater behavior observed acoustically helped to assess possible effects of vessels on the animals during acoustic surveys. © 2010 Acoustical Society of America.

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  • Seasonal and diurnal presence of finless porpoises at the corridor to the ocean from a semi‐closed bay habitat.

    Tomonari Akamatsu, Kiyomi Nakamura, Ryo Kawabe, Seishiro Furukawa, Hiromi Murata, Akihiro Kawakubo, Masayuki Komaba

    The Journal of the Acoustical Society of America   127 ( 3 ) 1825 - 1825  2010.03

    DOI

  • Seasonal and diurnal presence of finless porpoises at a corridor to the ocean from their habitat

    Tomonari Akamatsu, Kiyomi Nakamura, Ryo Kawabe, Seishiro Furukawa, Hiromi Murata, Akihiro Kawakubo, Masayuki Komaba

    Marine Biology   157 ( 8 ) 1879 - 1887  2010

     View Summary

    A number of local populations of finless porpoises (Neophocaena phocaenoides) are widely distributed throughout the warm coastal waters of Asia. The Omura Bay population, consisting of approximately 300 individuals, is the smallest of five populations inhabiting Japanese waters. It is a relatively new population that established after the global warming that took place approximately 9000 years ago. To observe whether these porpoises appear in the major corridor to the ocean from Omura Bay, we used acoustic monitoring to record occurrences of finless porpoises from November 2007 to May 2009. A stereo acoustic event recorder recorded the intensity and the sound source direction of biosonar signals, providing independent traces of sound sources corresponding to each detected animal. A total of 226 individuals were detected over the 1.5-year monitoring period, of which 76% occurred at night and 73% occurred during March and April. We compared the presence of porpoises to the Japanese anchovy catch in Omura Bay and the Hario Strait over the same period. Results suggested that possible reductions in anchovy resources in the bay could attract porpoises to the outside of their normal habitat. In total, 70% of the porpoise recordings took place when the tidal current was moving out of Omura Bay. Porpoises might follow the prey that are transported out of the bay due to the strong outbound current. The finless porpoises confined to the bay might extend their swimming area if prey is available. © Springer-Verlag 2010.

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  • Detection of yangtze finless porpoises in the poyang lake mouth area via passive acoustic data-loggers

    Songhai Li, Shouyue Dong, Satoko Kimura, Tomonari Akamatsu, Kexiong Wang, Ding Wang

    Biology, Evolution and Conservation of River Dolphins within South America and Asia     341 - 356  2010

     View Summary

    This chapter presents preliminary results on the distribution pattern of Yangtze finless porpoises (Neophocaena phocaenoides asiaeorientalis) in the Poyang Lake mouth area by using passive acoustic data-loggers at four different stations. Porpoise sounds were detected at all stations but their abundance decreased as the distance from the Yantze River increased. Porpoises were detected swimming both upstream to the Poyang Lake and downstream to the Yangtze River as well as between railway and highway bridges at the end of the lake. They were detected 13.9% of the total time monitored, and detected less frequently between 05:00 and 10:00 and between 15:00 and 18:00 during heavier shipping traffic. Also, there were relatively vacant periods between July 12 and July 28, 2007, and between August 5 and August 22, 2007, when virtually no porpoises were detected while there was a reversal of water current or increased water turbulence in the mouth area. These results suggest that movement and genetic communication between porpoise groups in the Yangtze River section and Poyang Lake might still remain, and therefore, the groups should be considered collectively, as a uniform unit for conservation. Bridge construction, shipping traffic, and current (turbulence and direction), might have affected the presence or movement pattern of porpoises in the study area and should be included in future conservation plans. © 2010 by Nova Science Publishers, Inc. All rights reserved.

  • Scanning sonar of rolling porpoises during prey capture dives

    T. Akamatsu, D. Wang, K. Wang, S. Li, S. Dong

    JOURNAL OF EXPERIMENTAL BIOLOGY   213 ( 1 ) 146 - 152  2010.01  [Refereed]

     View Summary

    Dolphins and porpoises have excellent biosonar ability, which they use for navigation, ranging and foraging. However, the role of biosonar in free-ranging small cetaceans has not been fully investigated. The biosonar behaviour and body movements of 15 free-ranging finless porpoises (Neophocaena phocaenoides) were observed using electronic tags attached to the animals. The porpoises often rotated their bodies more than 60 deg., on average, around the body axis in a dive bout. This behaviour occupied 31% of the dive duration during 186. h of effective observation time. Rolling dives were associated with extensive searching effort, and 23% of the rolling dive time was phonated, almost twice the phonation ratio of upright dives. Porpoises used short inter-click interval sonar 4.3 times more frequently during rolling dives than during upright dives. Sudden speed drops, which indicated that an individual turned around, occurred 4.5 times more frequently during rolling dives than during upright dives. Together, these data suggest that the porpoises searched extensively for targets and rolled their bodies to enlarge the search area by changing the narrow beam axis of the biosonar. Once a possible target was detected, porpoises frequently produced short-range sonar sounds. Continuous searching for prey and frequent capture trials appeared to occur during rolling dives of finless porpoises. In contrast, head movements ranging +/- 2 cm, which can also change the beam axis, were regularly observed during both dives. Head movements might assist in instant assessment of the arbitrary direction by changing the beam axis rather than prey searching and pursuit.

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  • A trial of tracking of echolocating finless porpoise by two stationary passive acoustic monitoring systems.

    Kimura Satoko, Akamatsu Tomonari, Li Songhai, Dong Shouyue, Wang Kexiong, Wang Ding, Arai Nobuaki

    Proceedings of the 5th International Symposium on SEASTAR2000 and Asian Bio-logging Science.     73 - 76  2010  [Refereed]

  • Detection probability of vocalizing dugongs during playback of conspecific calls

    Kotaro Ichikawa, Tomonari Akamatsu, Tomio Shinke, Kotoe Sasamori, Yukio Miyauchi, Yuki Abe, Kanjana Adulyanukosol, Nobuaki Arai

    JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA   126 ( 4 ) 1954 - 1959  2009.10  [Refereed]

     View Summary

    Dugongs (Dugong dugon) were monitored using simultaneous passive acoustic methods and visual observations in Thai waters during January 2008. Chirp and trill calls were detected by a towed stereo hydrophone array system. Two teams of experienced observers conducted standard visual observations on the same boat. Comparisons of detection probabilities of acoustic and visual monitoring between two independent observers were calculated. Acoustic and visual detection probabilities were 15.1% and 15.7%, respectively, employing a 300 s matching time interval. When conspecific chirp calls were broadcast from an underwater speaker deployed on the side of the observation boat, the detection probability of acoustic monitoring rose to 19.2%. The visual detection probability was 12.5%. Vocal hot spots characterized by frequent acoustic detection of calls were suggested by dispersion analysis, while dugongs were visually observed constantly throughout the focal area (p&lt;0.001). Passive acoustic monitoring assisted the survey since detection performance similar to that of experienced visual observers was shown. Playback of conspecific chirps appeared to increase the detection probability, which could be beneficial for future field surveys using passive acoustics in order to ensure the attendance of dugongs in the focal area. (C) 2009 Acoustical Society of America. [DOI: 10.1121/1.3203805]

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  • Analysis of the temporal structure of fish echoes using the dolphin broadband sonar signal

    Ikuo Matsuo, Tomohito Imaizumi, Tomonari Akamatsu, Masahiko Furusawa, Yasushi Nishimori

    JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA   126 ( 1 ) 444 - 450  2009.07  [Refereed]

     View Summary

    Behavioral experiments indicate that dolphins detect and discriminate prey targets through echolocating broadband sonar signals. The fish echo contains components from multiple reflections, including those from the swim bladder and other organs, and can be used for the identification of fish species and the estimation of fish abundance. In this paper, temporal structures were extracted from fish echoes using the cross-correlation function and the lowpass filter. First, the echo was measured from an anesthetized fish in a water tank. The number, reflector intensity, and echo duration were shown to be dependent on the species, individual, and orientation of the fish. In particular, the echo duration provided useful information on the fish body height and for species identification. Second, the echo was measured from the live fish suspended by nylon monofilament lines in the open sea. It was shown that this duration could be estimated regardless of whether or not the fish were moving.

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  • Localization and tracking of phonating finless porpoises using towed stereo acoustic data-loggers

    Songhai Li, Tomonari Akamatsu, Ding Wang, Kexiong Wang

    JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA   126 ( 1 ) 468 - 475  2009.07  [Refereed]

     View Summary

    Cetaceans produce sound signals frequently. Usually, acoustic localization of cetaceans was made by cable hydrophone arrays and multichannel recording systems. In this study, a simple and relatively inexpensive towed acoustic system consisting of two miniature stereo acoustic data-loggers is described for localization and tracking of finless porpoises in a mobile survey. Among 204 porpoises detected acoustically, 34 individuals (similar to 17%) were localized, and 4 of the 34 localized individuals were tracked. The accuracy of the localization is considered to be fairly high, as the upper bounds of relative distance errors were less than 41% within 173 m. With the location information, source levels of finless porpoise clicks were estimated to range from 180 to 209 dB re 1 mu Pa pp at 1 m with an average of 197 dB (N=34), which is over 20 dB higher than that estimated previously from animals in enclosed waters. For the four tracked porpoises, two-dimensional swimming trajectories relative to the moving survey boat, absolute swimming speed, and absolute heading direction are deduced by assuming the animal movements are straight and at constant speed in the segment between two consecutive locations.

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  • Influence of autojigger's winding velocity on lure holding behavior of neon flying squid Ommastrephes bartrami(Short Paper)

    KUROSAKA KOHEI, YAMASHITA HIDEYUKI, OCHI YOUSUKE, OGAWA MICHIO, AKAMATSU TOMONARI, INADA HIROSHI, WATANABE TOSHIHIRO, KOHEI KUROSAKA, HIDEYUKI YAMASHITA, YOUSUKE OCHI, MICHIO OGAWA, TOMONARI AKAMATSU, HIROSHI INADA, TOSHIHIRO WATANABE, Marine Fisheries Research and Development Center Fisheries Research Agency, Marine Fisheries Research and Development Center Fisheries Research Agency, Marine Fisheries Research and Development Center Fisheries Research Agency, Marine Fisheries Research and Development Center Fisheries Research Agency, National Research Institute of Fisheries Engineering Fisheries Research Agency, Department of Marine Bioscience Faculty of Marine Science Tokyo University of Marine Science and Technology

    NSUGAF   75 ( 1 ) 83 - 85  2009.01

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  • Measuring the target strength spectra of fish using dolphin-like short broadband sonar signals

    Imaizumi, T., Furusawa, M., Akamatsu, T., Nishimori, Y.

    Journal of the Acoustical Society of America   124 ( 6 )  2009

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    18
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  • Biosonar and auditory system of the Yangtze finless porpoise

    Songhai Li, Ding Wang, Kexiong Wang, Tomonari Akamatsu, Alexander Ya Supin, Vladimir V. Popov

    Endangered Species: New Research     1 - 13  2009

     View Summary

    The Yangtze finless porpoise (Neophocaena phocaenoides asiaeorientalis) is the only freshwater subspecies of finless porpoise (Neophocaena phocaenoides), living only in the middle and lower reaches of the Yangtze River. It has been declared to be endangered under the Red Data List criteria (C2b), by the International Union for the Conservation of Nature and Natural Resources (IUCN) in 2004. As well as other odontocetes, Yangtze finless porpoise possesses of sophisticated echolocation systems. Recent researches demonstrated excellent capabilities of high-frequency sound production and reception in this species. The animal produces one sonar click train per 5 s in average with inter-click interval changing typically between 10-70 ms. The click signals hold the characteristics of "typical" high-frequency, narrow-band, and short-time duration phocoenid echolocation sounds. The means of peak frequency of clicks are about 125 kHz, and the means of time duration are shorter than 70 μs. Careful scanning and acoustical auto focusing behavior in porpoises was also observed in free-ranging conditions by using biologging techniques. Hearing capability research by using evoked potential technique indicated that the range of greatest hearing sensitivity of Yangtze finless porpoise covered frequencies from 45 to 139 kHz, and the lowest thresholds of less than 50 dB re: 1 μPa were found at a frequency of 54 kHz. Frequent biosonar production by this subspecies allowed effective passive acoustical survey. These several years, density and distribution of Yangtze finless porpoises are being surveyed acoustically along its habitat. © 2009 by Nova Science Publishers, Inc. All rights reserved.

  • Bilateral bioacoustics research of Chinese freshwater dolphins

    Tomonari Akamatsu, Ding Wang, Kexiong Wang

    Acoustical Science and Technology   30 ( 1 ) 13 - 17  2009  [Refereed]

     View Summary

    China has various ecologically important sites that provide wonderful research opportunities. The biosonar behavior of Yangtze finless porpoises (Neophocaena phocaenoides asiaeorientalis) in the semi-natural reserve, Hubei, China has been extensively studied for the past five years by the Japan Fisheries Research Agency and Institute of Hydrobiology, Chinese Academy of Sciences. Careful scanning and acoustical autofocusing behavior in porpoises was firstly observed in free-ranging conditions. The biosonar model obtained in this study allowed us to recently develop a broadband high-resolution sonar system called the Dolphin Sonar Simulator. Frequent biosonar production by finless porpoises also allowed an effective passive acoustical survey to be conducted of the animal along the entire habitat of this species in 2006. Bilateral collaboration with cutting-edge acoustical technologies was proven to be highly productive for basic behavioral science, engineering applications, and the conservation of endangered species. © 2009 The Acoustical Society of Japan.

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  • Small-scale towing survey combined acoustical and visual observation for finless porpoise in the Yangtze River.

    Kimura Satoko, Akamatsu Tomonari, Wang Ding, Wang Kexiong, Li Songhai, Dong Shouyue, Arai Nobuaki

    Proceedings of the 4th International Symposium on SEASTAR2000 and Asian Bio-logging Science.     63 - 65  2009  [Refereed]

  • Comparison of stationary acoustic monitoring and visual observation of finless porpoises

    Kimura Satoko, Akamatsu Tomonari, Wang Kexiong, Wang Ding, Li Songhai, Dong Shouyue, Arai Nobuaki

    JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA   125 ( 1 ) 547 - 553  2009.01  [Refereed]

     View Summary

    The detection performance regarding stationary acoustic monitoring of Yangtze finless porpoises Neophocaena phocaenoides asiaeorientalis was compared to visual observations. Three stereo acoustic data loggers (A-tag) were placed at different locations near the confluence of Poyang Lake and the Yangtze River, China. The presence and number of porpoises were determined acoustically and visually during each 1-min time bin. On average, porpoises were acoustically detected 81.7±9.7% of the entire effective observation time, while the presence of animals was confirmed visually 12.7±11.0% of the entire time. Acoustic monitoring indicated areas of high and low porpoise densities that were consistent with visual observations. The direction of porpoise movement was monitored using stereo beams, which agreed with visual observations at all monitoring locations. Acoustic and visual methods could determine group sizes up to five and ten individuals, respectively. While the acoustic monitoring method had the advantage of high detection probability, it tended to underestimate group size due to the limited resolution of sound source bearing angles. The stationary acoustic monitoring method proved to be a practical and useful alternative to visual observations, especially in areas of low porpoise density for long-term monitoring. © 2009 Acoustical Society of America.

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  • Abundance and conservation status of the Yangtze finless porpoise in the Yangtze River, China

    Zhao X, Barlow J, Taylor BL, Pitman RL, Wang K, Wei Z, Stewart BS, Turvey ST, Akamatsu T, Reeves RR, Wang D

    Biological conservation.    2008.12

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  • Evidence of nighttime movement of finless porpoises through Kanmon Strait monitored using a stationary acoustic recording device

    Tomonari Akamatsu, Izumi Nakazawa, Takashi Tsuchiyama, Naoko Kimura

    FISHERIES SCIENCE   74 ( 5 ) 970 - 975  2008.10

     View Summary

    From March 2005 to March 2006, the presence of the finless porpoise Neophocaena phocaenoides in the Kanmon Strait, Japan was monitored using a stationary acoustic event recording device. A stereo acoustic event recorder (A-tag) recorded biosonar signals as well as sound source directions, which can be used to count the number of echolocating porpoises within a distance of 126 m. During 75 days of effective observation, 37 porpoises were detected acoustically. On average, one individual was detected every two days. Most of the finless porpoises appeared at night, and no porpoises were observed from 12:00 to 18:00 hours. Shipping traffic observed using the same acoustic system showed trends opposite to that of finless porpoise during the daytime. The tidal current did not affect the presence of the animals (up to 5.2 knots). However, porpoises were suggested to swim along the current direction. Finless porpoises appeared to be isolated and used relatively long-range sonar during the observations, suggesting that the porpoises passed through the Kanmon Strait rather than searched for prey.

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  • Underwater sound detection by cephalopod statocyst

    Kenzo Kaifu, Tomonari Akamatsu, Susumu Segawa

    FISHERIES SCIENCE   74 ( 4 ) 781 - 786  2008.08

     View Summary

    The cephalopod receptor of particle motion was identified. In a previous study, it was suggested that statocysts served this function, but there was no direct supporting evidence, and epidermal hair cells had not been conclusively ruled out. Experiments on Octopus ocellatus were conducted using respiratory activity as an indicator of sound perception. Intact animals clearly responded to 141-Hz particle motion at particle accelerations below 1.3 x 10(-3) m/s(2), and the mean perception threshold at this frequency was approximately 6.0 x 10(-4) m/s(2). Specimens in which the statoliths had been surgically removed did not show any response for accelerations up to 3.9 x 10(-3) m/s(2) at 141 Hz, which was approximately 16 dB greater than the mean perception threshold at this frequency. Specimens that had undergone a control operation in which the statoliths remained intact showed positive responses at 2.8 x 10(-3) m/s(2) for the same frequency stimulus. This indicates that the statocyst, which is morphologically similar to the inner ear system in fish, is responsible for the observed responses to particle motion in O. ocellatus. This is the first direct evidence that cephalopods detect kinetic sound components using statocysts.

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  • Simultaneous production of low- and high-frequency sounds by neonatal finless porpoises

    Songhai Li, Kexiong Wang, Ding Wang, Shouyue Dong, Tomonari Akamatsu

    JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA   124 ( 2 ) 716 - 718  2008.08

     View Summary

    Phocoenids are generally considered to be nonwhistling species that produce only high-frequency pulsed sounds. Here our results show that neonatal finless porpoises (Neophocaena phocaenoides) frequently produce clear low-frequency (2-3 kHz) pulsed signals, without distinct high-frequency energy, just after birth and can produce both low- (2-3 kHz) and high-frequency (&gt;100 kHz) pulsed signals simultaneously until about 20 days postnatal. The results indicate that low-frequency signals of neonatal finless porpoises are not an early form of high-frequency signals and suggest that low- and high-frequency signals may be produced by different sound production mechanisms. (C) 2008 Acoustical Society of America.

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  • Estimation of the detection probability for Yangtze finless porpoises (Neophocaena phocaenoides asiaeorientalis) with a passive acoustic method

    T. Akamatsu, D. Wang, K. Wang, S. Li, S. Dong, X. Zhao, J. Barlow, B. S. Stewart, M. Richlen

    JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA   123 ( 6 ) 4403 - 4411  2008.06

     View Summary

    Yangtze finless porpoises were surveyed by using simultaneous visual and acoustical methods from 6 November to 13 December 2006. Two research vessels towed stereo acoustic data loggers, which were used to store the intensity and sound source direction of the high frequency sonar signals produced by finless porpoises at detection ranges up to 300 m on each side of the vessel. Simple stereo beam forming allowed the separation of distinct biosonar sound source, which enabled us to count the number of vocalizing porpoises. Acoustically, 204 porpoises were detected from one vessel and 199 from the other vessel in the same section of the Yangtze River. Visually, 163 and 162 porpoises were detected from two vessels within 300 m of the vessel track. The calculated detection probability using acoustic method was approximately twice that for visual detection for each vessel. The difference in detection probabilities between the two methods was caused by the large number of single individuals that were missed by visual observers. However, the sizes of large groups were underestimated by using the acoustic methods. Acoustic and visual observations complemented each other in the accurate detection of porpoises. The use of simple, relatively inexpensive acoustic monitoring systems should enhance population surveys of free-ranging, echolocating odontocetes. (C) 2008 Acoustical Society of America.

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  • Shipboard measurements of the hearing of the white-beaked dolphin Lagenorhynchus albirostris

    P. E. Nachtigall, T. A. Mooney, K. A. Taylor, L. A. Miller, M. H. Rasmussen, T. Akamatsu, J. Teilmann, M. Linnenschmidt, G. A. Vikingsson

    JOURNAL OF EXPERIMENTAL BIOLOGY   211 ( 4 ) 642 - 647  2008.02

     View Summary

    This is the first report of an underwater audiogram from a dolphin in a capture-and-release scenario. Two bow-riding white-beaked dolphins Lagenorhynchus albirostris (a female and a male) were captured using the hoop-net technique in Faxafloi Bay, Iceland. The dolphins were transferred to a stretcher and hoisted into a plastic research tank on board a small fishing vessel. Two underwater transducers were used to cover the frequency range from 16 to 215 kHz. Two human EEG electrodes mounted in suction cups, one placed near the blow hole and the other on the dorsal fin, picked up bioelectrical responses to acoustic stimuli. Responses to about 1000 sinusoidal amplitude modulated stimuli for each amplitude/frequency combination were averaged and analyzed using a fast Fourier transform to obtain an evoked auditory response. Threshold was defined as the zero crossing of the response using linear regression. Two threshold frequencies at 50 kHz and 64 kHz were obtained from the female. An audiogram ranging from 16 to 181 kHz was obtained from an adult male and showed the typical. &apos;U&apos; shaped curve for odontocetes. The thresholds for both white-beaks were comparable and demonstrated the most sensitive high frequency hearing of any known dolphin and were as sensitive as the harbor porpoise.

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  • Indirect evidence of boat avoidance behavior of yangtze finless porpoises

    Songhai Li, Tomonari Akamatsu, Ding Wang, Kexiong Wang, Shouyue Dong, Xiujiang Zhao, Zhuo Wei, Xianfeng Zhang, Barbara Taylor, Leigh A. Barrett, Samuel T. Turvey, Randall R. Reeves, Brent S. Stewart, Michael Richlen, John R. Brandon

    Bioacoustics   17 ( 1-3 ) 174 - 176  2008

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  • The ontogeny of echolocation in a Yangtze finless porpoise (Neophocaena phocaenoides asiaeorientalis)

    Songhai Li, Ding Wang, Kexiong Wang, Jianqiang Xiaob, Tomonari Akamatsu

    JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA   122 ( 2 ) 715 - 718  2007.08

     View Summary

    Acoustic and concurrent behavioral data from one neonatal male Yangtze finless porpoise (Neophocaena phocaenoides asiaeorientalis) in captivity were presented. The calf click train was first recorded at 22 days postnatal, and the frequency of hydrophone-exploration behavior with head scanning motions in conjunction with emissions of click trains by the calf increased gradually with age. The echolocation clicks in the first recorded click train were indistinguishable from those of adults. Calf echolocation trains were found to decrease in maximum click-repetition rate, duration, and number of clicks per train with age while the. minimum click-repetition rate remained more consistent. (c) 2007 Acoustical Society of America.

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  • Echolocation click sounds from wild inshore finless porpoise (Neophocaena phocaenoides sunameri) with comparisons to the sonar of riverine N. p. asiaeorientalis

    Songhai Li, Ding Wang, Kexiong Wang, Tornonari Akamatsu, Zhiqiang Ma, Jiabo Han

    JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA   121 ( 6 ) 3938 - 3946  2007.06

     View Summary

    Acoustic signals from wild Neophocaena phocaenoides sunameri were recorded in the waters off Liao-dong-wan Bay located in Bohai Sea, China. Signal analysis shows that N. p. sunameri produced "typical" phocoenid clicks. The peak frequencies f(p), of clicks ranged from. 113 to 131 kHz with an average of 121 +/- 3.78 kHz (n=71). The 3 dB bandwidths Delta f ranged from 10.9 to 25.0 kHz with an average of 17.5 +/- 3.30 kHz. The signal durations At ranged from 56 to 109 mu s with an average 80 +/- 11.49 mu s. The number of cycles N, ranged from 7 to 13 with an average of 9 +/- 1.48. With increasing peak frequency there was a faint tendency of decrease in bandwidth, which implies a nonconstant value of f(p)/Delta f. On occasion there were some click trains with faint click energy presenting below 70 kHz, however, it was possibly introduced by interference effect from multiple pulses structures. The acoustic parameters of the clicks were compared between the investigated population and a riverine population of finless porpoise. (c) 2007 Acoustical Society of America.

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  • Stroke frequency, but not swimming speed, is related to body size in free-ranging seabirds, pinnipeds and cetaceans.

    Katsufumi Sato, Yutaka Watanuki, Akinori Takahashi, Patrick J O Miller, Hideji Tanaka, Ryo Kawabe, Paul J Ponganis, Yves Handrich, Tomonari Akamatsu, Yuuki Watanabe, Yoko o Mitani, Daniel P Costa, Charles-André Bost, Kagari Aoki, Masao Amano, Phil Trathan, Ari Shapiro, Yasuhiko Naito

    Proceedings. Biological sciences   274 ( 1609 ) 471 - 7  2007.02  [International journal]

     View Summary

    It is obvious, at least qualitatively, that small animals move their locomotory apparatus faster than large animals: small insects move their wings invisibly fast, while large birds flap their wings slowly. However, quantitative observations have been difficult to obtain from free-ranging swimming animals. We surveyed the swimming behaviour of animals ranging from 0.5 kg seabirds to 30 000 kg sperm whales using animal-borne accelerometers. Dominant stroke cycle frequencies of swimming specialist seabirds and marine mammals were proportional to mass(-0.29) (R(2)= 0.99, n = 17 groups), while propulsive swimming speeds of 1-2 m s(-1) were independent of body size. This scaling relationship, obtained from breath-hold divers expected to swim optimally to conserve oxygen, does not agree with recent theoretical predictions for optimal swimming. Seabirds that use their wings for both swimming and flying stroked at a lower frequency than other swimming specialists of the same size, suggesting a morphological trade-off with wing size and stroke frequency representing a compromise. In contrast, foot-propelled diving birds such as shags had similar stroke frequencies as other swimming specialists. These results suggest that muscle characteristics may constrain swimming during cruising travel, with convergence among diving specialists in the proportions and contraction rates of propulsive muscles.

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  • Quantitative surveys of fish assemblage at a high-rise artificial fish reef by stationary underwater cameras

    Hideyuki Takahashi, Akihiko Matsuda, Tomonari Akamatsu, Norimasa Takagi

    International Symposium on Underwater Technology, UT 2007 - International Workshop on Scientific Use of Submarine Cables and Related Technologies 2007     463 - 466  2007

     View Summary

    Stationary underwater cameras were deployed to evaluate spatial and temporal distribution of fish assemblage inhabiting a high-rise artificial reef. The camera named FISCHOM has a stereo camera or a monaural camera on board and it can operate periodically by an arbitrary interval. We can acquire the information about fish fauna and fish size distribution and their time series of reef fish assemblages by the assessment using the FISCHOMs. Two surveys were conducted in the early summer and fall of 2005 at a high-rise artificial fish reef in the Sea of Japan. In both surveys, five FISCHOMs were fixed dispersedly on the reef and operated in an hour interval As a result, we could evaluate the spatial and temporal distribution of the fish assemblage and their seasonal variations around the reef about 20 days. In total, 48 thousands of fish were counted in both surveys. Pearl-spot chromis Chromis notata notata, jack mackerel Trachwusjaponkus, and rockfish Sebastes spp. were mainly observed. We confirmed these major species had stable diurnal cycles; they were observed in daytime and rarely observed in midnight The differences of the spatial distributions of the major species were found by comparing the results of each FISCHOMs. The folk lengths of the major species were estimated by stereo measurements. © 2007 IEEE.

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  • Comparison of echolocation behaviour between coastal and riverine porpoises

    Tomonari Akamatsu, Jonas Teilmann, Lee A. Miller, Jacob Tougaard, Rune Dietz, Ding Wang, Kexiong Wang, Ursula Siebert, Yasuhiko Naito

    2007 SYMPOSIUM ON UNDERWATER TECHNOLOGY AND WORKSHOP ON SCIENTIFIC USE OF SUBMARINE CABLES AND RELATED TECHNOLOGIES, VOLS 1 AND 2     563 - +  2007  [Refereed]

     View Summary

    Echolocation behaviour of a harbor porpoise and six finless porpoises was recorded in open-water systems using acoustic data loggers (A-tag). In total 1359 click trains were recorded during 4.6 h for the harbor porpoise and 46,240 click trains were recorded during 82.3 h for the finless porpoises. The harbor and finless porpoises produced sonar click trains every 12.3 and 6.4 s on average, respectively. During the inter-click-train interval, the porpoises were silent or produced clicks below 148 dB re. 1 mPa, the detection threshold of the tag. Ninety percent of the inter-click-train intervals were 20 s or less in both species. This means that porpoises frequently produce intense click trains. Click-train intervals lasting over 50 s constituted 1% of the total intervals in finless porpoises and 4% in the harbor porpoise. Both species swam without intense clicks for less than 10m in most cases, but occasionally remained silent or used undetected low-intensity clicks for more than 1 min. During these periods, the porpoises would be susceptible to entanglement in fishing nets.

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    3
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  • Measurements of target strength spectra of metal spheres and live fish by using broad band sonar signals of dolphin

    Tomohito Imaizumi, Masahiko Furusawa, Tomonari Akamatsu, Yasushi Nishimori

    2007 SYMPOSIUM ON UNDERWATER TECHNOLOGY AND WORKSHOP ON SCIENTIFIC USE OF SUBMARINE CABLES AND RELATED TECHNOLOGIES, VOLS 1 AND 2     589 - +  2007  [Refereed]

     View Summary

    This paper describes a method and results of measurements of the target strength (TS) spectra of metal spheres and live fish using sonar signals of dolphins with a broadband system. First, we measured the broadband form function of a tungsten carbide and a copper sphere in a water tank and confirmed good agreements with the theoretical values. Second, we measured the TS spectra of three species of anaesthetized fish in a water tank. Although the spectra showed nearly similar tendencies of past measurements, they varied considerably among the species, the individuals, and the tilt angles. Third, we measured the TS spectra of tethered live fish suspended from a ship at the sea. In this case we removed the directivity of transducers by the tungsten carbide sphere suspended near the fish. The sonar signals of dolphin are effective to measure TS spectra of fish.

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  • Analysis of the echo for identifying the temporal structure of the fish by using the broadband sonar signal of dolphin

    I. Matsuo, Tomohito Imaimmi, Masahiko Furusawa, Tomonari Akamatsu, Yasushi Nishimori, Shinji Ogawa

    2007 SYMPOSIUM ON UNDERWATER TECHNOLOGY AND WORKSHOP ON SCIENTIFIC USE OF SUBMARINE CABLES AND RELATED TECHNOLOGIES, VOLS 1 AND 2     583 - +  2007  [Refereed]

     View Summary

    Dolphins can recognize prey by using the broadband sonar signals. The echo from the fish contains components resulting from multiple reflections, for example, the swimbladder and body surface of the fish. It is necessary for identification of fish species to estimate the positions and amplitudes of these reflections. In this paper, we analyzed the echo from the fish by using the sonar signal of the bottlenose dolphin. Firstly, we analyzed echoes which were measured from the anaesthetized fish in a water tank. It was verified that the numbers and delays of reflections are varied with both the species and the tilt angle. Secondary, we analyzed the echo which was measured from the live fish suspended by nylon monofilament line in the open sea. It was verified that the delays and amplitudes of reflections are varied with the orientation and movement of the fish.

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  • Monitoring local migration of Yangtze finless porpoises by acoustic gate

    The Journal of the Marine Acoustics Society of Japan   34 ( 4 ) 260 - 265  2007

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  • Sonar gain control in echolocating finless porpoises (Neophocaena phocaenoides) in an open water (L)

    Songhai Li, Ding Wang, Kexiong Wang, Tomonari Akamatsu

    JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA   120 ( 4 ) 1803 - 1806  2006.10  [Refereed]

     View Summary

    Source levels of echolocating free-ranging Yangtze finless porpoise (Neophocaena phocaenoides asiaeorientalis) were calculated using a range estimated by measuring the time delays of the signals via the surface and bottom reflection paths to the hydrophone, relative to the direct signal. Peak-to-peak source levels for finless porpoise were from 163.7 to 185.6 dB re:1 mu Pa. The source levels are highly range dependent and varied approximately as a function of the one-way transmission loss for signals traveling from the animals to the hydrophone. (c) 2006 Acoustical Society of America.

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  • Estimated detection distance of a baiji's (Chinese river dolphin, Lipotes vexillifer) whistles using a passive acoustic survey method

    Kexiong Wang, Ding Wang, Tomonari Akamatsu, Kaoru Fujita, Rika Shiraki

    JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA   120 ( 3 ) 1361 - 1365  2006.09  [Refereed]

     View Summary

    Source levels and phonation intervals of whistles produced by a free-ranging baiji (Chinese river dolphin) were measured in the seminatural reserve of Shishou in Hubei, China. A total of 43 whistles were recorded over 12 recording sessions. The mean dominant frequency (the frequency at the highest energy) was 5.7 kHz (s.d.=0.67). The calculated source level was 143.2 dB rms re 1 mu Pa (s.d.=5.8). Most phonation intervals were shorter than 460 s, and the average interval was 205 s (s.d. = 254). Theoretical detection range of baiji's whistle was 6600 m at the present study site, but it could reduce a couple of hundred meters in practical noisy situation in the Yangtze River. Sporadic phonation (205 s interval on average) with relatively faint signal of baiji was considered, to be difficult to be detected by a towing hydrophone system. Stationed monitoring or slow speed towing of hydrophones along the river current is recommended. (c) 2006 Acoustical Society of America.

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    18
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  • Feeding behavior of wild dugongs monitored by a passive acoustical method

    Chika Tsutsumi, Kotaro Ichikawa, Nobuaki Arai, Tomonari Akamatsu, Tomio Shinke, Takeshi Hara, Kanjana Adulyanukosol

    JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA   120 ( 3 ) 1356 - 1360  2006.09  [Refereed]

     View Summary

    Little is known about feeding behavior of wild dugongs (Dugong dugon) because direct measurements of feeding events in the water were. scarcely feasible. In this study, the authors achieved the first successful feeding sound monitoring in a seagrass area using a full-band underwater recording system (called automatic underwater sound monitoring system for dugong: AUSOMS-D). In total, 175 feeding sounds were identified in N5 h of recording. Feeding sounds were only detected at night, implying diurnal differences in the feeding behavior of the studied dugong population. Differences in periodicity of feeding sounds suggested that two or more individuals were in the acoustically observable area. Furthermore, a feeding position monitored by two AUSOMS-Ds was used to calculate source levels of dugong feeding sounds. Assuming spherical propagation, source levels were measured between 70.6 and 79.0 dB rms re 1 mu Pa/ root Hz. (c) 2006 Acoustical Society of America.

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    18
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  • Dugong (Dugong dugon) vocalization patterns recorded by automatic underwater sound monitoring systems

    K Ichikawa, C Tsutsumi, N Arai, T Akamatsu, T Shinke, T Hara, K Adulyanukosol

    JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA   119 ( 6 ) 3726 - 3733  2006.06  [Refereed]

     View Summary

    To quantitatively examine the diurnal, or tidal, effects on dugong behavior, we employed passive acoustic observation techniques to monitor the animals. Automatic underwater sound monitoring systems for dugongs (AUSOMS-D) were deployed on the sea floor at depths of about 5 in south of Talibong Island, Thailand. The AUSOMS-D recorded underwater sound in stereo at a sampling frequency of 44.1 kHz for more than 116 consecutive hours. Dugong calls were automatically detected by newly developed software with a detection rate of 36.1% and a false alarm rate of 2.9%. In total, 3453 calls were detected during the 164 h of recording. The autocorrelation of the call rate indicated an attendance cycle of about 24 or 25 h, and the most frequent vocalizations were observed from 0300 to 0500 h. The calculated bearings of the sound sources, i.e., dugongs, were used as an indicator to track the relative numbers of dugongs during the monitoring periods. (c) 2006 Acoustical Society of America.

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    36
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  • FISCHOMステレオカメラの立体計測精度の評価

    高橋 秀行, 松田 秋彦, 赤松 友成

    水産工学研究所技報   ( 28 ) 85 - 91  2006.03

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  • Acoustic survey of irrawaddy dolphin populations in Chilika lagoon: First test of a compact high-resolution device

    R. Bahl, T. Ura, H. Sugimatsu, T. Inoue, T. Sakamaki, J. Kojima, T. Akamatsu, H. Takahashi, S. K. Behera, A. K. Pattnaik, Muntaz Khan, S. K. Kar

    OCEANS 2006 - Asia Pacific    2006

     View Summary

    Irrawaddy dolphins (Orcaella brevirostris) being on top of the food chain are considered as a flagship species of Chilika. These cetaceans produce characteristic echolocation pulses that make them acoustically visible, night or day. Acoustic-based survey methods are found to be indispensable for surveying porpoises and dolphins in coastal precincts. This paper reports the first such collaborative attempt in Chilika by applying acoustic survey technology based on the design of an innovative compact and portable acoustic survey device designed for observation of groups of small cetaceans. The acoustic sensor system is housed in a ©bird-cage© structure containing 3 hydrophones forming a main linear array, together with two more hydrophones forming a small 3-element triangle array with the central hydrophone, in a plane perpendicular to the linear array axis. It weighs 25kg and is 3.6m long, 30cm in diameter, and can be deployed either vertically or horizontally with buoys and a weight. A high-speed multichannel data acquisition system records the dolphin click sounds from all hydrophones. Signal processing algorithms have been developed for automatic detection and discrimination of echolocation clicks from other underwater sounds, localization of sound sources, and tracking individual animals. The device has previously been tested in vertical mode in a quasi-natural environment with a group of bottlenose dolphins that has confirmed its capability to precisely track several vocalizing animals. The depth of the Chilika lagoon in the dolphin habitat can be as shallow as 1.5m. Thus, the array has to be deployed in horizontal mode, which enables it to provide very good lateral resolution in the broadside direction. This paper reports the first results of using this array in shallow water conditions. Movements of several Irrawaddy dolphins have been observed very clearly. ©2006 IEEE.

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  • Stability of call sequence in dugongs' vocalization

    Naoko Okumura, Kotaro Ichikawa, Tomonari Akamatsu, Nobuaki Arai, Tomio Shinke, Takeshi Hara, Kanjana Adulyanukosol

    OCEANS 2006 - Asia Pacific    2006

     View Summary

    Dugongs (Dugong dugon) produce different types of vocalization such as chirp, trill, and barks. Previous reports showed that dugongs have two kinds of phonemes: long duration calls (trill) and short duration calls (chirp-squeaks hereinafter called chirp). Especially, the chirp and trill calls were widely reported in different populations. However, characteristics of call patterns in dugongs have never been reported. Moreover, the function of these calls was not revealed. The objective of this study is to classify the vocalization patterns of dugong calls and discuss the stability call sequences within and across local populations of dugongs. We recorded the underwater sound at the off Talibong Island, Trang, Thailand in 2004 and 2005 for 120 hours by an automatic underwater sound recording system (AUSOMS-D, System Intech, Tokyo). The AUSOMS-D is the water resistant stand-alone recording system and developed for passive acoustical monitoring targeting human audible range. The AUSOMS-D consisted of a pair of hydrophones located 2 m apart for calculating the bearings of the sound sources. The electric circuits and batteries were housed in a pressure-resistant case, and the hydrophones were connected to a stereo preamplifier. The sound signals were fed into a 1-kHz high pass filter to eliminate low frequency background noise. Digitized signals were recorded on an 80 GB removable hard disk drive by uncompressed format with a time stamp. The power supply system with batteries and DC/DC converter were also housed inside the case. The sampling frequency of the A/D converter was 44.1 kHz and the dynamic range was 74-120 dB (re 1 μPa) with a 16-bit resolution. Each hydrophone had flat frequency responses within 2 dB between 1 and 10 kHz. For the comparison purpose, we made recording of a captive dugong in Toba Aquarium, Japan, which was introduced from Philippine water. We analyzed the underwater sound data set that was obtained in both animals in different environment and populations. Short duration calls with less than 300 milliseconds were defined as chirp and trill was defined as a call lasting over 300 milliseconds. The end of a call sequence was defined at the silence over 3 seconds. Total of 1174 audible calls were detected from total of 12 hours data set (from 3:50 to 6:50 01-04 March 2004). Chirp were observed more than trill calls (567 chirps and 67 trills). Chirp-tochirp transitions were most frequency observed (81.68%), whereas trill-to-trill transitions were the least (4.27%). Transitions between the two types of calls were also observed (6.98%, 7.07%). Trill appeared in the middle and the end of a call sequence. The position of the trill did not differ between wild individual in Thailand and a captive individual from off Philippine that are considered to be separated populations. The stability of the sequence of each type of calls in a call sequence is investigated. Unlike song of birds or baleen whales, the call sequence pattern of dugong suggests small difference across the populations. The call sequence analysis as well as the behavioral context observation will provide the key to interpret function of dugong calls. ©2006 IEEE.

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  • Acoustic monitoring of echolocating porpoises

    Tomonari Akamatsu, Ding Wang, Kexiong Wang, Songhai Li

    OCEANS 2006 - ASIA PACIFIC, VOLS 1 AND 2     43 - +  2006  [Refereed]

     View Summary

    Underwater ultrasonic sound of finless porpoises Neophocaena phocaenoides were monitored concurrent with visual observations in the Yangtze River, China. In a total of 774 km cruise, 588 finless porpoises were sighted by visual observation and 44,864 ultrasonic pulses were recorded. The acoustic monitoring system could detect presence of the finless porpoises 82% of the time. False alarm in the system occurred with a frequency of 0.9%. The high frequency acoustical observation is suggested as an effective method for field surveys of small cetaceans, which produce high frequency sonar signals.

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  • Origin of the double- and multi-pulse structure of echolocation signals in Yangtze finless porpoise (Neophocaena phocaenoides asiaeorientialis)

    Songhai Li, Kexiong Wang, Ding Wang, Tomonari Akamatsu

    Journal of the Acoustical Society of America   118 ( 6 ) 3934 - 3940  2005.12  [Refereed]

     View Summary

    The signals of dolphins and porpoises often exhibit a multi-pulse structure. Here, echolocation signal recordings were' made from four geometrically distinct positions of seven Yangtze finless porpoises temporarily housed in a relatively small, enclosed area. Some clicks demonstrated double-pulse, and others multi-pulse, structure. The interpulse intervals between the first and second pulse of the double- and multi-pulse clicks were significantly different among data from the four different positions (p&lt
    0.01, one-way ANOVA). These results indicate that the interpulse interval and structure of the double- and multi-pulse echolocation signals depend on the hydrophone geometry of the animal, and that the double- and multi-pulse structure of echolocation signals in Yangtze finless porpoise is not caused by the phonating porpoise itself, but by the multipath propagation of the signal. Time delays in the 180° phase-shifted surface reflection pulse and the nonphase-shifted bottom reflection pulse of the multi-pulse structures, relative to the direct signal, can be used to calculate the distance to a phonating animal. © 2005 Acoustical Society of America.

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  • Method for underwater measurement of the auditory brainstem response of fish

    Tomohiro Suga, Tomonari Akamatsu, Ryo Kawabe, Tomonori Hiraishi, Katsutarou Yamamoto

    Fisheries Science   71 ( 5 ) 1115 - 1119  2005.10  [Refereed]  [International journal]

     View Summary

    The auditory brainstem response (ABR) of fishes is commonly measured by bringing the heads of the fishes out of the water in a small tank. However, this method is inapplicable to experiments for large fishes that are economically important in large spaces such as the sea or in a large tank. This paper describes a method of recording, the ABR for fishes in water, without exposing the fish heads to air, by using a waterproof, insulated electrode. To evaluate the effectiveness of this method, the goldfish Carassius auratus was investigated, and the ABR waveform and auditory thresholds measured in water were compared with those measured on the surface. Both ABR waveforms and auditory thresholds showed similar trends between the two methods. The underwater ABR method is useful to measure the auditory thresholds of larger fish in natural or on-site environments such as the sea, net enclosures and large aquaria in which precise positioning of the fish is not possible. However, more improvement is needed to apply this method to large fishes.

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  • A passive acoustic monitoring method applied to observation and group size estimation of finless porpoises

    Kexiong Wang, Ding Wang, Tomonari Akamatsu, Songhai Li, Jianqiang Xiao

    Journal of the Acoustical Society of America   118 ( 2 ) 1180 - 1185  2005.08  [Refereed]

     View Summary

    The present study aimed at determining the detection capabilities of an acoustic observation system to recognize porpoises under local riverine conditions and compare the results with sighting observations. Arrays of three to five acoustic data loggers were stationed across the main channel of the Tian-e-zhou Oxbow of China's Yangtze River at intervals of 100-150 m to record sonar signals of free-ranging finless porpoises (Neophocaena phocaenoides). Acoustic observations, concurrent with visual observations, were conducted at two occasions on 20-22 October 2003 and 17-19 October 2004. During a total of 42 h of observation, 316 finless porpoises were sighted and 7041 sonar signals were recorded by loggers. The acoustic data loggers recorded ultrasonic signals of porpoises clearly, and detected the presence of porpoises with a correct detection level of 77.6% and a false alarm level of 5.8% within an effective distance of 150 m. Results indicated that the stationed passive acoustic observation method was effective in detecting the presence of porpoises and showed potential in estimating the group size. A positive linear correlation between the number of recorded signals and the group size of sighted porpoises was indicated, although it is faced with some uncertainty and requires further investigation. © 2005 Acoustical Society of America.

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  • Effects of ambient noise on the whistles of Indo-Pacific bottlenose dolphin populations

    Tadamichi Morisaka, Masanori Shinohara, Fumio Nakahara, Tomonari Akamatsu

    Journal of Mammalogy   86 ( 3 ) 541 - 546  2005.06  [Refereed]

     View Summary

    Communication among animals should use signals that are most efficient in their particular habitat. Here, we report data from 3 populations of Indo-Pacific bottlenose dolphins (Tursiops aduncus) in Japan that produce whistles transmitted efficiently through environmental ambient noise. We compared the characteristics of the ambient noise in the dolphins' habitats and the whistles produced. In habitats with less ambient noise, dolphins produced whistles at varying frequencies with greater modulations; when ambient noise was greater, dolphins produced whistles of lower frequencies with fewer frequency modulations. Examination of our results suggests that communication signals are adaptive and are selected to avoid the masking of signals and the attenuation of higher-frequency signals. Thus, ambient noise may drive the variation in whistles of Indo-Pacific bottlenose dolphin populations. © 2005 American Society of Mammalogists.

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  • Geographic variations in the whistles among three Indo-Pacific bottlenose dolphin Tursiops aduncus populations in Japan

    Tadamichi Morisaka, Masanori Shinohara, Fumio Nakahara, Tomonari Akamatsu

    Fisheries Science   71 ( 3 ) 568 - 576  2005.06  [Refereed]

     View Summary

    Whistles of Indo-Pacific bottlenose dolphins from three populations in Japan were collected and analyzed quantitatively. Geographic variations in the whistles among populations were found. Significant differences in the whistles among years within each population were also found, but those differences could not explain whole differences among populations because some parameters of the whistles had more differences among populations than among years within each population. As changes with time in the whistles within each population might cause the geographic variations among populations, researchers should take the yearly change within populations into consideration when they study the geographic variation in the whistle of dolphins.

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  • Echolocation signals of the free-ranging Yangtze finless porpoise (Neophocaena phocaenoides asiaeorientialis)

    Songhai Li, Kexiong Wang, Ding Wang, Tomonari Akamatsu

    Journal of the Acoustical Society of America   117 ( 5 ) 3288 - 3296  2005.05  [Refereed]

     View Summary

    This paper describes the high-frequency echolocation signals from free-ranging Yangtze finless porpoise in the Tian-e-zhou Baiji National Natural Reserve in Hubei Province, China. Signal analysis showed that the Yangtze finless porpoise clicks are typical high-frequency narrow-band (relative width of the frequency spectrum Q = 6.6 ± 1.56, N = 548) ultrasonic pulses. The peak frequencies of the typical clicks range from 87 to 145 kHz with an average of 125 ± 6.92 kHz. The durations range from 30 to 122 μs with an average of 68 ± 14.12 μs. The characteristics of the signals are similar to those of other members of the Phocoenidae as well as the distantly related delphinids, Cephalorhynchus spp. Comparison of these signals to those of the baiji (Lipotes vexillifer), who occupies habitat similar to that of the Yangtze finless porpoise, showed that the peak frequencies of clicks produced by the Yangtze finless porpoise are remarkably higher than those produced by the baiji. Difference in peak frequency between the two species is probably linked to the different size of preferred prey fish. Clear double-pulse and multi-pulse reverberation structures of clicks are noticed, and there is no indication of any low-frequency (&lt
    70 kHz) components during the recording period. © 2005 Acoustical Society of America.

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  • Off-axis sonar beam pattern of free-ranging finless porpoises measured by a stereo pulse event data logger

    T Akamatsu, D Wang, KX Wang

    JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA   117 ( 5 ) 3325 - 3330  2005.05  [Refereed]

     View Summary

    The off-axis sonar beam patterns of eight free-ranging finless porpoises were measured using attached data logger systems. The transmitted sound pressure level at each beam angle was calculated from the animal's body angle, the water surface echo level, and the swimming depth. The beam pattern of the off-axis signals between 45 and 115 (where 0 corresponds to the on-axis direction) was nearly constant. The sound pressure level of the off-axis signals reached 162 dB re 1 mPa peak-to-peak. The surface echo level received at the animal was over 140 dB, much higher than the auditory threshold level of small odontocetes. Finless porpoises are estimated to be able to receive the surface echoes of off-axis signals even at 50-m depth. Shallow water systems (less than 50-m depth) are the dominant habitat of both oceanic and freshwater populations of this species. Surface echoes may provide porpoises not only with diving depth information but also with information about surface direction and location of obstacles (including prey items) outside the on-axis sector of the sonar beam. 2005 Acoustical Society of America.

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  • Biosonar behaviour of free-ranging porpoises

    Tomonari Akamatsu, Ding Wang, Kexiong Wang, Yasuhiko Naito

    Proceedings of the Royal Society B: Biological Sciences   272 ( 1565 ) 797 - 801  2005.04  [Refereed]

     View Summary

    Detecting objects in their paths is a fundamental perceptional function of moving organisms. Potential risks and rewards, such as prey, predators, conspecifics or non-biological obstacles, must be detected so that an animal can modify its behaviour accordingly. However, to date few studies have considered how animals in the wild focus their attention. Dolphins and porpoises are known to actively use sonar or echolocation. A newly developed miniature data logger attached to a porpoise allows for individual recording of acoustical search efforts and inspection distance based on echolocation. In this study, we analysed the biosonar behaviour of eight free-ranging unless porpoises (Neophocaena phocaenoides) and demonstrated that these animals inspect the area ahead of them before swimming silently into it. The porpoises inspected distances up to 77 m, whereas their swimming distance without using sonar was less than 20 m. The inspection distance was long enough to ensure a wide safety margin before facing real risks or rewards. Once a potential prey item was detected, porpoises adjusted their inspection distance from the remote target throughout their approach. © 2005 The Royal Society.

    DOI PubMed

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  • Audiogram measurement based on the auditory brainstem response for juvenile Japanese sand lance Ammodytes personatus

    Tomohiro Suga, Tomonari Akamatsu, Kouichi Sawada, Hiroaki Hashimoto, Ryo Kawabe, Tomonori Hiraishi, Katsutaro Yamamoto

    Fisheries Science   71 ( 2 ) 287 - 292  2005.04  [Refereed]  [International journal]

     View Summary

    In this study, the auditory thresholds for juvenile Japanese sand lance Ammodytes personatus were measured based on its auditory brainstem response (ABR). The amplitude of the ABR waveforms to a sound stimulus were larger than that of the electric background noise caused by general brainwaves and myogenic signals after the averaging procedure. Japanese sand lance responded to low frequency sounds between 128 Hz and 512 Hz with a sound pressure level of 115-125 dB. As the test frequency decreased, so did the auditory threshold level, and the level was about 116 dB at 128 Hz and 181 Hz. These results indicate that Japanese sand lance can detect low frequency sound but are less sensitive than other fish species. These high thresholds are probably caused by the lack of a swim bladder.

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  • Measurements of auditory sensitivity in common carp Cyprinus carpio by the auditory brainstem response technique and cardiac conditioning method

    KOJIMA TAKAHITO, ITO HIROSUKE, KOMADA TOMOYUKI, TANIUCHI TORU, AKAMATSU TOMONARI

    Fisheries Science   71 ( 1 ) 95 - 100  2005.02

     View Summary

    Recently, the non-invasive auditory brainstem response (ABR) technique has been applied to the determination of hearing sensitivity in fish. The technique has some advantages over, and methodological differences from, the classical techniques. The auditory thresholds of common carp were measured by the ABR technique. The classical method was applied to measure cardiac response by electrocardiogram (ECG) after conditioning with electric shock. The most sensitive frequency obtained by ABR was 505 Hz, and by ECG, 1000 Hz. The shapes of the audiogram obtained by ABR and ECG were similar, though threshold levels in both audiograms differed from each other. Furthermore, audiograms obtained by using behavioral techniques were compared with those taken by the ABR and ECG techniques to assess the validity of the ABR technique for testing fish hearing sensitivity. The measured threshold levels increased in the order of behavioral, ABR, and ECG techniques, in the range below 1000 Hz.

    DOI CiNii

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  • New stereo acoustic data logger for free-ranging dolphins and porpoises

    Tomonari Akamatsu, Akihiko Matsuda, Shiro Suzuki, Ding Wang, Kexiong Wang, Michihiko Suzuki, Hiroyuki Muramoto, Naoki Sugiyama, Katsunori Oota

    Marine Technology Society Journal   39 ( 2 ) 3 - 9  2005

     View Summary

    To observe the bio-sonar behavior of dolphins and porpoises, a miniature stereo acoustic data logger was developed to record the echolocation clicks of small cetaceans. The 'A-tag' device is small enough to be attached to a dolphin or porpoise. A-tag can record the sonar pulse intensity, precise inter-click-intervals, and time difference between sounds ; arriving at two different hydrophones. The A-tag works for up to 60 hours continuously and allows observation of the sonar target range of free-ranging odontocetes. The time of arrival at the two hydrophones on the tag allows vocalizations from nearby individuals to be identified. A less invasive tagging technique using a suction cup was also developed. A mean attachment time of 15 hours was obtained on free-ranging finless porpoises in a freshwater system in China. The A-tag proved to be a useful tool for investigating the underwater echolocation behavior of odontocetes.

    DOI

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    54
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  • Quantitative Survey of Fish Schools near Artificial Reefs by the Optical-acoustic System (FISCHOM)

    TAKAHASHI Hideyuki, MATSUDA Akihiko, TAKAGI Norimasa, AKAMATSU Tomonari

    Journal of Fisheries Engineering   41 ( 3 ) 261 - 265  2005

     View Summary

    For quantitative assessments of the effect of artificial reefs to accumulate fish school. we developed a low cost fish school monitoring system (FISCHOM). which enables visual and acoustical observation of fish resources for more than several days. In this paper, we report the profile of prototype FISCHOM and the outcome of trial survey. FISHCOM is consisted of two sensors (a stereo camera with two strobe lights and an echo sounder), a programmable timer, a battery, and a pressure resistant housing with a visually and acoustically transparent window for the sensors. All components except for the housing were selected from inexpensive articles on the market. A digital camera captured two visual images apart 50 cm away each other, which was combined together by a stereo photogrammetric mirror. The stereo images enable us to measure the three-dimensional information of fish school (e.g. fish length tilt angle, distribution). Two sensors acquire a set of data every optional interval (from several seconds to hours) controlled by the programmable timer. A trial survey was carried out at a high-rise artificial reef located off Atsumi, Yamagata prefecture on May 2003. FISCHOM succeeded a 5 days monitoring with an hour interval of data acquisition. We obtained a time series data of individual number of fish, fish length and distance from FISHCOM by the stereo camera, and fish school distribution by the echo sounder. We have demonstrated that the FISCHOM is appropriate to obtain quantitative and continuous data of fish school than other observation methods, which commonly used for the artificial reef assessment, such as observation by SCUBA diver, angling sampling and fish echo sounder operated on a boat.

    DOI CiNii

  • Monitoring dugong feeding behavior in a tidal flat by visual and acoustic observation

    堤 千華, 市川光太郎, 赤松友成, 荒井修亮, 新家富雄, 原 武史

    海洋理工学会誌,Vol.11 No.1.,77-80    2005  [Refereed]

  • Estimation of dive behavior and Bio-sonar characteristics of free-ranging Baiji(Lipotes vexillifer) based on acoustic data

    URA Tamaki, BAHL Rajendar, YANO Masato, AKAMATSU Tomonari, WANG Ding, WANG Kexiong

    Monthly journal of the Institute of Industrial Science, University of Tokyo   56 ( 6 ) 467 - 470  2004.11

    DOI CiNii

  • Marine mammal echolocation provides a model of forthcoming bio-oriented sonar

    Tomonari Akamatsu, Ding Wang, Kexiong Wang, Yasuhiko Naito

    Ocean '04 - MTS/IEEE Techno-Ocean '04: Bridges across the Oceans - Conference Proceedings   4   2321 - 2322  2004

     View Summary

    Cetacean's sonar is an appropriate model of underwater acoustical sensing technology. Sonar behavior of three free-ranging finless porpoises in an oxbow of the Yangtze River was observed by micro data logger systems attached on the animals. Newly developed acoustic data logger could record porpoise's sonar pulse events 1000 times every second with the amplitude information. Close correlation between sonar effort and behavioral context could be observed. Frequent use of sonar with various inter-pulse intervals was recorded during quick body movements characterized by spiky change of heaving acceleration. The inter-pulse intervals were precisely controlled to adjust the distance to a remote target, which was similar to the terminal phase in bat's sonar behavior. © 2004 IEEE.

  • Spotlined sardine Sardinops melanostictus listens to 1-kHz sound by using its gas bladder

    T Akamatsu, A Nanami, HY Yan

    FISHERIES SCIENCE   69 ( 2 ) 348 - 354  2003.04  [Refereed]

     View Summary

    The auditory characteristics of pelagic fish have received less attention compared to those of benthic or freshwater fish species, even though underwater sounds are considered to affect their behavior. Audiograms of five spotlined sardines were obtained using the auditory brainstem response technique in which the evoked potential on the skin covering the head of the fish was measured. The auditory brainstem response is a non-invasive electrophysiological method that enables the auditory threshold level of fragile species, such as spotlined sardines, to be measured. The gas bladder of the spotlined sardine has been considered as possibly contributing to an enhancement in their hearing. In the test, the sound absorption profile of sardines was also measured. The frequency at the lowest auditory threshold level (i.e. the most sensitive frequency) and absorption were found at 1024 Hz and 1040 Hz, respectively. The spotlined sardine was found to be sensitive to sounds at relatively higher frequency ranges compared to other seawater fishes and the gas bladder is seen to play a significant role in detecting sound.

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  • Single-hydrophone method for reconstructing dynamic behavior of endangered Chinese river Dolphin

    Rajendar Bahl, Masato Yano, Tamaki Ura, Tomonari Akamatsu, Ding Wang, Kexiong Wang

    Oceans Conference Record (IEEE)   1   473 - 477  2003

     View Summary

    Chinese River Dolphin (Lipotes vexillifer), usually called 'baiji', is one of the most endangered mammals in the world. The preservation of these mammals directly ensures the health of the ecosystem. However, not much behavioral information on baiji is available so far, that could effectively assist in undertaking their preservation. This research is an attempt to reveal baiji's hitherto unknown underwater dynamic behavior. For this work we have analyzed and extracted motion parameters from clicks of a free-swimming baiji recorded in 1996 at a single hydrophone. The absence of detailed bottom information made it difficult to localize baiji using the multiple reflections and forced us to rely completely on surface reflections only. From measurements of time delay between the direct path and the surface echo, not only large-scale behavior but also fine-scale behavior has been revealed, such as: periods of diving and surfacing, circling behavior underwater and a characteristic nodding motion. These studies have contributed towards a broad understanding of baiji's foraging exercises from the standpoint of formulating an acoustical survey for the search for this endangered marine mammal.

    DOI

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  • Empirical refinements applicable to the recording of fish sounds in small tanks

    T Akamatsu, T Okumura, N Novarini, HY Yan

    JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA   112 ( 6 ) 3073 - 3082  2002.12

     View Summary

    Many underwater bioacoustical recording experiments (e.g., fish sound production during courtship or agonistic encounters) are usually conducted in a controlled laboratory environment of small-sized tanks. The effects of reverberation, resonance, and tank size on the characteristics of sound recorded inside small tanks have never been fully addressed, although these factors are known to influence the recordings. In this work, 5-cycle tone bursts of 1-kHz sound were used as a test signal to investigate the sound recorded in a 170-1 rectangular glass tank at various depths and distances from a transducer. The dominant frequency, sound-pressure level, and power spectrum recorded in small tanks were significantly distorted compared to the original tone bursts. Due to resonance, the dominant frequency varied with water depth, and power spectrum level of the projected frequency decreased exponentially with increased distance between the hydrophone and the sound source; however, the resonant component was nearly uniform throughout the tank. Based on the empirical findings and theoretical calculation, a working protocol is presented that minimizes distortion in fish sound recordings in small tanks. To validate this approach, sounds produced by the croaking gourami (Trichopsis vittata) during staged agonistic encounters were recorded according to the proposed protocol in an 1800-1 circular tank and in a 37-1 rectangular tank to compare differences in acoustic characteristics associated with tank size and recording position. The findings underscore pitfalls associated with recording fish sounds in small tanks. Herein, an empirical solution to correct these distortions is provided. (C) 2002 Acoustical Society of America.

    DOI

  • Analyses of small tank acoustics: Empirical and theoretical approaches

    Tsuyoshi Okumura, Tomonari Akamatsu, Hong Y. Yan

    Bioacoustics   12 ( 2-3 ) 330 - 332  2002.01

    DOI

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    27
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  • Acoustic signals and aggressive conflicts in the skunk loach botia morleti: Integrating sensory and behavioural approaches

    Timothy C. Sparkes, Callie Prater, Tomonari Akamatsu, Hong Y. Yan

    Bioacoustics   12 ( 2-3 ) 257 - 259  2002.01

    DOI

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    4
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  • Diving behaviour of freshwater finless porpoises (Neophocaena phocaenoides) in an oxbow of the Yangtze River, China

    Tomonari Akamatsu, Ding Wang, Kexiong Wang, Zhuo Wei, Qingzhong Zhao, Yasuhiko Naito

    ICES Journal of Marine Science   59 ( 2 ) 438 - 443  2002  [Refereed]

     View Summary

    Dive-depth and swim-speed of a juvenile and an adult free-ranging, Yangtze finless porpoises (Neophocaena phocaenoides) were observed using velocity-time-depth recorders in an oxbow of the Yangtze River. In total, 8222 individual dives were recorded over 59 hours. Two dive types, deep-dive (≥2.7 m) and shallow-dive, were recognized. Horizontal travel distances of two finless porpoises in a day were 94.4 km and 90.3 km, which were longer than those of oceanic relative species (harbor porpoises, Phocoena phocoena). Although the shallow water limited the maximum dive-depth, dive-duration, and bottom-time of finless porpoises were similar to the harbor porpoises. A sudden drop of swim-speed below 0.25 m s-1 was frequently observed nearby the maximum dive-depth. This seemed to indicate "turning around" behaviour, possibly during prey pursuit. © 2002 Published by Elsevier Science Ltd on behalf of International Council for the Exploration of the Sea.

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  • A passive acoustical survey method of finless porpoises

    Tomonari Akamatsu, Ding Wang, Kexiong Wang, Zhuo Wei, Yasuhiko Naito

    FISHERIES SCIENCE   68   294 - 297  2002  [Refereed]

     View Summary

    The finless porpoises (Neophocaena phocaenoides) have narrow band and high frequency sonar signals, which are distinctive from background noises. Underwater sound monitoring with hydrophones placed along the sides of a research vessel, concurrent with visual observations was conducted in the Yangtze River from Wuhan to Poyang Lake in China. In a total of 774 km cruise, 588 finless porpoises were sighted by visual observation and 44,864 ultrasonic pulses were recorded by the acoustical observation system. The acoustic monitoring system could detect presence of the finless porpoises 88% of the time, 300 m away from the hydrophone. False alarm in the system occurred with a frequency of 0.9%. Such a high detection performance of the present system was due to a large sound pressure level of sonar signals and frequent sound production. Over 160 dB off-axis sound pressure level and sonar signal production at every 3 to 4 s were observed by an acoustic and a behavioral data logger. The high frequency acoustical observation is suggested as an effective method for field surveys of small cetaceans, which produce sonar signals.

    DOI

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    2
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  • The sonar performance of dolphins

    AKAMATSU Tomonari

    Transactions of Visualization Society of Japan   21   139 - 140  2001.07

     View Summary

    Dolphins have highly developed sonar abilities and have been studied extensively in captivity. The use of sonar by dolphins and porpoises in the wild is thought to be related to the underwater navigation and searching behavior. Here we report a new and simple method to archive continuous click events individually. Echolocation click events and swimming speed of finless porpoises (Neophocaena phocaenoides) were recorded with data loggers attached on the animals. The echolocation range converted from sonar pulse intervals in open waters ranged up to 130 m. Echolocation of free-ranging dolphins appears to adapt to various distance in navigation or ranging. Silent swim distance, calculated by the swim speed multiplied by the duration of the non-echolocating periods, was smaller than the echolocation range. Finless porpoises are believed to examine their frontal area acoustically using echolocation. In other words, the observed finless porpoises swam without echolocation only in an already inspected area.

    DOI CiNii

  • Comparison between visual and passive acoustic detection of finless porpoises in the Yangtze river, China

    T Akamatsu, D Wang, KX Wang, Z Wei

    JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA   109 ( 4 ) 1723 - 1727  2001.04

     View Summary

    Recently, sonar signals and other sounds produced by cetaceans have been used for acoustic detection of individuals and groups in the wild. However, the detection probability ascertained by concomitant visual survey has not been demonstrated extensively. The finless porpoises (Neophocaena phocaenoides) have narrow band and high-frequency sonar signals, which are distinctive from background noises. Underwater sound monitoring with hydrophones (B&K8103) placed along the sides of a research vessel, concurrent with visual observations was conducted in the Yangtze River from Wuhan to Poyang Lake in 1998 in China. The peak to peak detection threshold was set at 133 dB re 1 mu Pa. With this threshold level, porpoises could be detected reliably within 300 m of the hydrophone. In a total of 774-km cruise, 588 finless porpoises were sighted by visual observation and 44 864 ultrasonic pulses were recorded by the acoustical observation system. The acoustic monitoring system could detect the presence of the finless porpoises 82% of the time. A false alarm in the system occurred with a frequency of 0.9%. The high-frequency acoustical observation is suggested as an effective method for field surveys of small cetaceans, which produce high-frequency sonar signals. (C) 2001 Acoustical Society of America.

    DOI PubMed

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  • A method for individual identification of echolocation signals in free-ranging finless porpoises carrying data loggers

    T Akamatsu, D Wang, KX Wang, Y Naito

    JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA   108 ( 3 ) 1353 - 1356  2000.09

     View Summary

    Echolocation click events of a free-ranging juvenile and an adult finless porpoise (Neophocaena phocaenoides) were recorded with an acoustic data logger. Additionally, dive depth and swim speed of the juvenile were recorded with a behavior data logger. Echoes of echolocation signals from the water surface were clearly detected in shallow dives approximately less than 2 m. The delay time between a surface echo and a direct signal corresponded with the two-way transmission time for the animal's depth, indicating that the signals originated from the animal wearing the data loggers. The finless porpoises produced echolocation signals frequently and were thought to be able to detect their depth by listening to echoes from the water surface. (C) 2000 Acoustical Society of America. [S0001-4966(00)01609-X].

    DOI PubMed

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  • Echolocation range of captive and free-ranging baiji (Lipotes vexillifer), finless porpoise (Neophocaena phocaenoides), and bottlenose dolphin (Tursiops truncatus)

    T Akamatsu, D Wang, K Nakamura, K Wang

    JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA   104 ( 4 ) 2511 - 2516  1998.10

     View Summary

    The interclick intervals of captive dolphins are known to be longer than the two-way transit time between the dolphin and a target. In the present study, the interclick intervals of free-ranging baiji, finless porpoises, and bottlenose dolphins in the wild and in captivity were compared. The click intervals in open waters ranged up to 100-200 ms, whereas the click intervals in captivity were in the order of 4-28 ms. Echolocation of free-ranging dolphins appears to adapt to various distance in navigation or ranging, sometimes up to 140 m. Additionally, the difference of waveform characteristics of clicks between species was recognized in the frequency of maximum energy and the click duration. (C) 1998 Acoustical Society of America. [S0001-4966(98)06609-0].

    DOI

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  • Acoustical observation of dolphins

    AKAMATSU Tomonari

    Seibutsu Butsuri   38 ( 4 ) 147 - 150  1998.07

     View Summary

    Dolphins have bio-sonar ability called echoiocation. Clicks, echolocation signals, provide various biological information, such as, species, target range and acoustical survey effort of dolphins. Acoustical measurement is anewly developed method to observe underwater behavior of vocalizing animals.

    DOI CiNii

  • Gillnet Passive Acoustic Deterrents:Investigating Inter-Reflector Spacings with a Harbor Porpoise Phocoena phocoena

    NAKAMURA Koji, AKAMATSU Tomonari, GOODSON A.David, KAGOSHIMA Kenji, SHIMAZAKI Kenji

    Fisheries Science   64 ( 4 ) 648 - 649  1998

    DOI CiNii

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    3
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  • Startle Response Level of Japanese Anchovy Engraulis japonicus to Underwater Pure Tone Signals

    Tomonari Akamatsu, Yoshiki Matsushita, Yoshimi Hatakeyama, Yoshihiro Inoue

    Fisheries Science   62 ( 4 ) 648 - 649  1996.08

    DOI

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    5
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  • Effects of underwater sounds on escape behavior of Steller sea lions

    T Akamatsu, K Nakamura, H Nitto, M Watabe

    FISHERIES SCIENCE   62 ( 4 ) 503 - 510  1996.08

     View Summary

    The reactions of 10 captive Steller sea lions Eumetopias jubatus, including one adult male, four adult females and five juvenile animals to underwater sounds, with and without the presence of a baited fishing net, were observed. Two narrow spectrum sounds, an 8 kHz pure tone and a 1 kHz to 4 kHz frequency sweep, three broad spectrum sounds, two mechanically generated impulse sounds, and the recorded vocalization of a killer whale were used. The reactions of Steller sea lions were divided into three categories. Category O: Both adult and juvenile Steller sea lions landed on a side of their pool during a one-minute period timed from the start of the sound projection. Category a: More than two juvenile Steller sea lions landed. Category X:A single juvenile Steller sea lion or no animals landed.
    Impulsive sounds transmitted at high source level (210 dB re 1 mu Pa at 1 m) or pure tone sounds (165 dB source level) were found to repel adult Steller sea lions. Broad band spectrum sounds did not repel adult and juvenile Steller sea lions after successive sound projections.
    The male Steller sea lion was only deterred from eating the fish entangled in the net by the high source level impulsive sound.
    The acoustic characteristics required to repel Steller sea lions are thought to be narrow spectrum within the sensitive range of a Steller sea lion&apos;s audible frequency and above 165 dB sound pressure level. However, Steller sea lions appear to acclimatize to repeated sound projections, and a sound pressure level below 165 dB does not appear to be enough to repel Steller sea lions from a fishing net.

  • エコ-ロケ-ション信号検出テレメトリ-システムの開発とネズミイルカでの測定実験

    赤松 友成

    水産工学研究所研究報告   ( 15 ) p145 - 156  1994.03

    CiNii

  • A review of studies on attempts to reduce the entanglement of the Dall's porpoise, Phocoenoides dalli, in the Japanese salmon gillnet fishery

    Y. Hatakeyama, K. Ishii, T. Akamatsu, H. Soeda, T. Shimamura, T. Kojima

    Gillnets and cetaceans     549 - 563  1994

     View Summary

    Dall's porpoises emit short high frequency pulses ranging from 135-149kHz, with a pulse width of 50-60μs and a source level of 165-175dB re 1μPa. When chased toward a gillnet in open sea, they have been observed to change their swimming direction to avoid it by either swimming along it or diving underneath it. Estimated target strengths of a float, leadline, lead and netting were -25, -33, -39, and -55dB, respectively. Approximate estimates of Dall's porpoise's detection ranges for the leadline and netting were 30 and 8m, respectively. Sound generators (SG-1 to 4) in the frequency range 20-150kHz were developed on the basis of the frequency components of clicks and observed responses to sounds. Air-tube threads to increase the net target strength were also used. Catch decrease rates (DRs) of the sound generators (with the exception of SG-4) were 3-16% and the DR in the case of the gillnet with three air-tube threads in the centre portion was 8-20%. As for SG-4, entanglement was concentrated in the portion of the net where SG-4 was not attached and the sound wave was weak. -from Authors

  • ECHOLOCATION RATES OF TWO HARBOR PORPOISES (PHOCOENA PHOCOENA)

    Tomonari Akamatsu, Yoshimi Hatakeyama, Takahito Kojima, Hideo Soeda

    Marine Mammal Science   10 ( 4 ) 401 - 411  1994

     View Summary

    The rate of occurrence of click trains of two harbor porpoises (Phocoena phocoena) were counted during 14 nights. We developed an echolocation signal detection system that was harnessed to a porpoise and activated a light when the animal emitted an echolocation signal. This device, referred to as a click‐light, detects echolocation signals above 150 dB re 1 μPa in the 28–180 kHz range. Echolocation rates, i.e., occurrences of click trains, changed frequently, ranging from 0 to 25 per minute. Echolocation rates were affected by feeding, individual difference, and enclosure type such as the net enclosure and the pool. The porpoise echolocation rates seemed to show acclimation. Copyright © 1994, Wiley Blackwell. All rights reserved

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  • EFFECTS OF PULSE SOUNDS ON ESCAPE BEHAVIOR OF FALSE KILLER WHALES

    T AKAMATSU, Y HATAKEYAMA, N TAKATSU

    NIPPON SUISAN GAKKAISHI   59 ( 8 ) 1297 - 1303  1993.08

     View Summary

    We observed the behavior of two false killer whales Pseudorca crassidens in response to a variety of underwater pulsed sounds. The whales were kept in a net enclosure. We employed 15 different kinds of sounds and carried out 68 experiments. The behavior of the false killer whales after the sounds were transmitted was divided into three categories: &apos;&apos;effective&apos;&apos;, &apos;&apos;somewhat effective&apos;&apos;, and &apos;&apos;not effective&apos;&apos;. Effective behavior indicates that the false killer whales swam directly away from the source of the sound soon after transmission. At the beginning of the experiments, the sound pressure level of the effective category was above about 170dBrel mu Pa. This level rose as the number of experiments increased. A single pulse did not affect the behavior of the false killer whales. Pulse-interval and pulse-duration modulated sounds seemed to be more difficult to acclimate to than stable pulse sounds. To repel false killer whales, unexperienced sounds are thought to be more effective than experienced sounds.

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  • 流し網と魚の超音波反射

    畠山 良己, 赤松 友成

    水産工学研究所技報. 漁業生産   ( 5 ) 15 - 24  1991.03

    CiNii

  • Experiments on the recognizable part of the gill net and the process of entanglement of bottlenose dolphin Tursiops truncatus.

    Akamatsu Tomonari, Hatakeyama Yoshimi, Ishii Ken, Soeda Hideo, Shimamura Tetsuya, Kojima Takahito

    NSUGAF   57 ( 4 ) 591 - 597  1991

     View Summary

    Recently, the dolphin's and porpoise's entanglement in gill net becomes an issue. The situation requires that the effective counter-measure should be done.<br> We reserched the dolphin's entanglement condition and their ability of recognizing the gill net.<br> We used bottlenose dolphin Tursiops truncatus. The net enclosure in Taiji port in Wakayama prefecture was the experiment field. We observed the dolphin's behavior related to barriers such as a gill net, float, rope, and netting only (without float line and ground line). The dolphin got entangled only in the condition that it swan at night and the barrier is netting only. At daytime, bottlenose dolphin might mainly use the sense of sight. At night it might use echolocation.<br> We concluded that at daytime dolphin can recognize the net only, at night it can recognize the existence of the net, but can scarcely recognize the detail of the net's figure by echoloca-tion. On the other hand, at night the dolphin can recognize sufficiently the float by echo-location.

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Books and Other Publications

  • イルカはなぜ鳴くのか

    文一総合出版  1996

Research Projects

  • Monitoring of coral reef ecosystem by underwater biological sounds

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (A)

    Project Year :

    2017.04
    -
    2020.03
     

    AKAMATSU TOMONARI

     View Summary

    Many types of sounds can be heard in the water. Composition of various sources changes diurnally or seasonally. This research visualized underwater soundscape using unsupervised machine learning. Based on the recordings of multiple years, soundscape in coral reefs showed daily and seasonal changes. In addition, diversity indexes of sound types in deep water was higher than that in shallow water. The result supports the refugia hypothesis that suggest mesophotic coral reef ecosystem could have less effect by ocean warming.

  • Development of new calibration method for low frequency underwater sounds

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research

    Project Year :

    2016.04
    -
    2020.03
     

    AKAMATSU TOMONARI

     View Summary

    A new calibration method for underwater low frequency sound was proposed that has not been possible without large floating pen and funding before. This calibration method conducted in calm lake provided accurate sensitivity value within 1 dB comparing with that measured at underwater calibration facility. We compared non-calibrated hydrophones produced in US, New Zealand, and Japan, and found sound receiving characteristics for each.

  • Research on the conflict between Harbour Porpoise and Fisheries

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)

    Project Year :

    2014.04
    -
    2017.03
     

    MATSUISHI Takashi, MATSUDA Ayaka, KURODA Mika, MATSUI Natsuki, MAEDA Saki, SAKURAI Kenji

     View Summary

    Harbour porpoise is strongly affected by human activities because its habitats is near shore. Wide range of researches are conducted in Europe and North America but little in Japan. Recently, stranding network and acoustic observation devices has developed in Japan, which enable to conduct new approach to the research of harbour porpoise. In the current study, specimens are collected from stranded and by caught harbour porpoise to analyse the diet and the conflict between fisheries. Also by using acoustic devices, observations are conducted around fishing gears to clarify the behaviour around the gears. From these result, conflicts between harbour porpoise and fisheries are described which will help to find a sound coexistence between cetacean and human.

  • 海洋生物の遠隔的種判別技術の開発

    独立行政法人科学技術振興機構  戦略的創造研究推進事業

    Project Year :

    2011
    -
    2016
     

  • Effect of Ship Noise on Marine Mammals

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Exploratory Research

    Project Year :

    2013.04
    -
    2015.03
     

    UMEDA Naoya, AKAMATSU Tomonari, MASUYAMA Yutaka, SAKURADA Akiko, KUNIEDA Yoshiaki, UYAMA Hisashi, MORI Kyouichi, TANIGUCHI Kazuyoshi, IKEGAMI Tadashige, SUGAWARA Shigeru, MITSUI Hiroshi

     View Summary

    We investigated effects of ship noise on marine mammals by using a fully-rigged sailing ship off Japanese Isles and by using a sailing yacht and powered ship near Notojima with towed underwater acoustic sensors. In the former survey, frequency to meet marine mammals was not so high that we failed to obtain significant data. On the other hand, in the latter survey, we frequently measured responses of groups of Indo-Pacific bottlenose dolphin to two types of ship. The results demonstrates that no significant difference in their responses between the sailing ship and the motor ship at low speed.

  • Research of feeding ecology of baleen whales using acoustic biologging technique

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)

    Project Year :

    2012.04
    -
    2015.03
     

    AKAMATSU TOMONARI

     View Summary

    For the sustainable use of fisheries resources, feeding pressure of baleen whales is not negligible. However amount of feeding and species of prey could be observed in stomach contents by capturing of these species. Present study revealed that the feeding events of blue whales and humpback whales could be observed directly using acoustic biologging technique. In addition, three dimensional reconstruction of underwater feeding behavior was conducted. Analysis of the vocalizations logged on the animals provided phonating rate and source levels, which is published in an international scientific journal.

  • “フィールドミュージアム”構想によるアマゾンの生物多様性保全

    JST/JICA  地球規模課題対応国際科学技術協力(SATREPS)

    Project Year :

    2014
    -
    2015
     

  • Estimating detection probability and population changes for conservation of finless porpoises

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)

    Project Year :

    2009
    -
    2011
     

    SHIRAKIHARA Kunio, AKAMATSU Tomonari, KITAKADO Toshihide, AMANO Masao, SHIRAKIHARA Miki

     View Summary

    The finless porpoise, a kind of toothed whales, is exposed to human activities. The existence of this species is threatened. Abundance, which is essential information for conservation, has been estimated using sighting surveys. Because the detection probability on the track line, g(0), is hard to be grasped, abundance estimates have been given under an assumption of g(0)=1. We developed a method to estimate g(0) using a combination of acoustic surveys and sighting surveys. We carried out an aerial sighting survey in Ohmura Bay, Nagasaki Prefecture, Japan, in 2010. A population decrease was not detected over these 10 years.

  • イルカ型対象判別ソナーの開発

    新技術・新分野創出のための基礎研究推進事業

    Project Year :

    2007
    -
    2011
     

     View Summary

    イルカ型広帯域ソナーを模倣した対象判別機能をもつソナーの開発

  • Development of algorithm to analyze time series acceleration data

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (A)

    Project Year :

    2007
    -
    2010
     

    SATO Ku, SHIMATANI KenーIchiro, YODA Ken, WATANABE ShinーIchi, TAKAHASHI Akinori, SAKAMOTO Kentaro, AKAMATSU Tomonari

     View Summary

    We have developed a new procedure to categorize behavior from body acceleration, together with the release of a user-friendly computer application "Ethographer". This method was applied for several data obtained from many animals and comparative studies were also conducted.

  • Acoustic survey of baiji in their historic habitat of the Yangtze River

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)

    Project Year :

    2007
    -
    2010
     

    AKAMATSU Tomonari

     View Summary

    Distribution of endangered freshwater cetaceans was revealed by cutting-edge underwater acoustic technology. Macro scale distribution of cetaceans in the entire Yangtze River and micro scale distribution in a high density area were provided. Historic habitat of baiji and Yangtze finless porpoises were surveyed from Yichang, nearby three gorges dam, to Shanghai, using towing type underwater microphone. Results suggested extinction of baiji and quick reduction of finless porpoises. Log-term stationary acoustic observation had been conducted at the hot spot, high density waters, in the middle of the Yangtze River. Using the outcomes, a model to convert acoustic detection rate to real density of existing number of animals was proposed. Extensive towing acoustic survey was conducted in the same section and provided detail map of distribution of porpoises. In the last year, periodical automatic surveys using a cargo ship as a platform of the acoustic device were conducted from Wuhan to Shanghai, 1100km stretch of the middle and lower reached of the Yanzgter River. This method is cost effective and useful for range-wide monitoring of small odontocetes, which has been applied worldwide in these days.

  • 音響データロガーによるジュゴンモニタリングネットワークの構築

    日本学術振興会  科学研究費助成事業 萌芽研究

    Project Year :

    2004
    -
    2006
     

    荒井 修亮, 守屋 和幸, 赤松 友成, 畔上 修一

     View Summary

    ジュゴンは草食性の海生ほ乳類(海牛類)で熱帯から亜熱帯の沿岸域に生息する。我が国の沖縄本島周辺はジュゴン生息の北限と言われており、同海域に生息するジュゴンは生物学上非常に重要な希少種である。このため、生息頭数の確認(環境省)、漁業による混獲の回避と餌場である海草群落の保護・培養(水産庁)等、国を挙げての対策が講じられている。しかし、既に沖縄海域では10頭未満の生息頭数と言われており、講じる対策の生物学的根拠の調査すら危ぶまれている現状である。
    我々はこうした緊急を要する事態に対して、ジュゴンの生態を直接観察可能なタイ国沿岸にフィールドを求めた。そして、特に漁業による事故死を未然に防止するためのジュゴンモニタリングシステムを、ジュゴンの鳴音を長期間記録する音響データロガーシステムによって構築することを目的とする。
    平成18年度には次の項目について研究を実施した。
    2006年11月にタイ国トラン県リボン島周辺海域において、AUSOMS-Dによるジュゴン鳴音の連続観測並びに海草藻場における摂餌痕(ジュゴン・トレール)の調査と摂餌音の連続録音を行った。合わせて、目視によるジュゴン観測を実施した。AUSOMS-Dの録音データ解析から、ジュゴン鳴音並びに摂餌音のモニタリングが可能であることが分かった。

  • Development of monitoring system using marine animals as oceanographic data collectors

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (A)

    Project Year :

    2003
    -
    2006
     

    SATO Katsufumi, ARAI Nobuaki, AKAMATSU Tomonari, WATANUKI Yutaka, SAKAMOTO Wataru, TAKAHASHI Akinori

     View Summary

    Bio-logging science, the use of small, data-logging electronic devices on animals, provides the capacity for researchers to examine oceanographic environment that define critical habitat of aquatic animals. The aim of this project is to develop new technique to monitor animal behavior in relation to their surrounding environments. Field studies were conducted at various places from tropical region to Antarctica. Target species were many aquatic animals such as fishes, reptile, seabirds and marine mammals.
    For example, we examined the diving behavior of thick-billed murres (Uria lomvia) at St. George Island, southeastern Bering Sea, in relation to sea surface temperature and thermocline depth using ventrally attached depth-temperature recorders. Murres dove deeper in the mixed water mass, than in the stratified water, where most dives were to just below the thermocline depth. It suggests that the thermocline is important in shaping dive profiles of seabirds, possibly through its effect on the vertical distribution of both zooplankton and fish prey.
    In other case, animal-borne cameras deployed on Weddell seals revealed that the underside of an Antarctic ice shelf was covered by aggregated invertebrate communities, most likely cnidarians and isopods. This observation indicates that, similar to the sea floor, ice shelves serve as an important habitat for a remarkable amount of marine invertebrate fauna in Antarctica, and seals are effective for collecting oceanographic environment in severe condition.
    In conclusion, marine animals are favorable platforms for oceanographic sampling and bio-logging science is highly available to investigate aquatic animal behavior and physiology in relation to their surrounding environments.

  • イルカ型ソナーをモデルとした次世代魚群探知技術の研究

    新技術・新分野創出のための基礎研究推進事業

    Project Year :

    2002
    -
    2006
     

     View Summary

    イルカのソナー行動に学んだ新しい水中探査技術の研究

  • Development of AUV for Whale following

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (A)

    Project Year :

    2002
    -
    2004
     

    NOSE Yoshiaki, URA Tamaki, ASADA Akira, YANAGISAWA Masao, KOJIMA Junichi, AKAMATSU Tomonari

     View Summary

    There are few studies on the behavior of whales in underwater. Conventional whale observation from ships gives us only the knowledge of their behavior on ocean surface. Recently new methods using satellite system and suction-cup-TDR tag system have been developed. Satellite system is effective for tracking whales on surface, but this system can not collect any data of whales in underwater. On the other hand, suction-cup TDR tag is effective for collecting data of whales not only on surface but in underwater, however it must be physically attached to a whale by researcher. The other problem is that tag is sometimes lost after it was apart from a whale. Consequently whale's behavior in underwater remains still uncertain to us, thus establishment of a new method which can be utilized for observing whale's behavior on surface and in underwater is expected.
    In this research, we proposed new whales observation system using AUV(Autonomous Underwater Vehicle) as an underwater platform. The results of several sea trials show that the realized system works effectively.
    Most whales have particular sounds called vocalizations or clicks. Male humpback whales sing songs composed by complicated phrases. Sperm whales are known that they emit loud impulsive broadband sounds called clicks during their diving to a deep water. We analyzed their acoustic data using signal processing techniques and develop new compact acoustic system based on passive sonar for implementing to AUV. Using this system, AUV can get direction and depth information of each whales in underwater to classify and follow them in sub-real time.
    For the purpose of observing sperm whale's diving behavior, we did sea trials in 2002 and 2003 off Ogasawara Islands and improved the system. In September 2004, we finally could deploy AUV and collect some data with this system. The result of data analysis indicates this system is suitable for sperm whale following using AUV.
    For the purpose of observing humpback whales behavior, we collected sound data and established new sound model. The result of data sampling test indicates this model is appropriate to be used for classification of humpback whales. Next, we rebuild this model to more compact device to implement to AUV and track humpback whales using AUV.
    Based on this research, a river dolphin observation project using acoustic system has been started.
    For future works, we would like to propose carrying out sustainable whale observations using this system off Ogasawara Islands and off Okinawa Islands.

  • 水産有用魚種の超音波聴覚と反応行動に関する研究

    日本学術振興会  科学研究費助成事業 若手研究(B)

    Project Year :

    2002
    -
    2003
     

    赤松 友成

     View Summary

    超音波聴覚を有する魚類が近年発見され,水産資源探査用の超音波が,魚群を威嚇し,資源量の過小推定を引き起こす可能性が指摘されていた。そこで,我が国沿岸に生息する水産有用魚種の超音波聴覚を音刺激に対する魚類頭頂部への誘発電位(聴性脳幹反応)を利用して計測し,音響資源計測における魚類行動への潜在的な影響を調べた。
    超音波領域における聴覚の確認実験を行うため,低周波音の再生に適した現有の聴性脳幹反応計測システムに,超音波対応の小型のトランスデューサーを加え,水中で超音波の再生ができるよう改造した。また,大型魚での実験を容易にするため,電極を魚類頭部に接着し絶縁して,水中においても聴性脳幹反応の記録ができる技術を開発した。さらに,超音波領域まで良好な増幅特性を有するパワーアンプと,超音波再生用のトランスデューサーを組み合わせて,超音波暴露実験が可能なシステムを構築した。
    このシステムを用いて,マイワシ,カタクチイワシ,イカナゴ,マコガレイで超音波聴覚を計測した。いずれの種類も,低周波音に感度があったが,超音波は感受しなかった。このため,超音波聴覚はニシン科魚類のなかでも限定的な種に存在する可能性が示唆された。
    なお,マコガレイを除く上記の魚種においては,これまで聴覚感度そのものが未計測であったため,新しい知見を得た。すなわち,マイワシは海産魚のなかでは比較的高い1kHzで感度が良く,音波を鰾で感受していた。イカナゴは,数百Hzの低周波領域を聴くことができるが,聴覚感度は低いことが明らかになった。この研究の副産物として,水中における聴性脳幹反応の計測手法が確立された。この手法を応用すれば,稚魚から大型魚までの様々な魚の聴覚感度を,船上の水槽や生け簀などの現場環境で計測できると期待される。

  • Development of monitoring systems for studying ecology and behavior of bottlenose dolphins-taking aerial pictures of schools using a captive balloon system and recording underwater vocalizations using a sonobuoy system-

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B).

    Project Year :

    1998
    -
    2000
     

    SHIRAKIHARA Kunio, HURUSAWA Masahiko, ISHIMATSU Takakazu, KASUYA Toshio, AKAMATSU Tomonari

     View Summary

    Indo-Pacific bottlenose dolphins are found thoughout a year in the coastal waters of Amakusa, Kyushu, Japan. To study ecology and behavior of the dolphins, monitoring systems have been developed ; a captive balloon system for taking aerial pictures of schools and a sonobuoy system for recording underwater vocalizations from schools.
    The balloon system consists of a captive balloon(2.5 m in diameter)filled with the helium gas, a video sub-system(2.1 kg)suspended from the balloon and a control sub-system on a boat. The following information was obtained from images of a schoo1 ; aerial behavior of the school members, temporal changes in number of surfacing individuals, configuration of the school and spatial distribution of individuals. Mother-calf pairs were distinguishable from others when a small portion of the school was taken using a telephoto lens. Seasonal changes in ratios of mothercalf pairs to all the individuals suggest the main parturition season of spring to autumn. This system is applicable to outer cetaceans.
    Tother with surveys using the two systems, direct recordings of vocalizations by a hydrophon from a boat, theodolite tracking from land, behavior observations, and photographic surveys for individual identification were attempted. Vocalization recordings show that the dolphins searched sometimes a few meters ahead or 200 m ahead. Theodolite tracking surveys clarify a regular movement pattrn along the shore in the daytime. Behavior observations suggest that the dolphins take a rest in a limited areas during the heat of the day. Individual identification surveys give estimetes of population size of almost 200 individuals and mortality rate of 3.4% per year.

  • Bio-SONAR,it's application to the engineering.

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)

    Project Year :

    1997
    -
    1998
     

    WATANABE Yoshiaki, FUKUSHIMA M., MATSUMURA S., RIQUIMAROUX H, AKAMATSU T., NAKAMURA T.

     View Summary

    One of the special aim of this project is to realize the cooperative observations among the engineers and zoologists to investigate the echo location behavior perforned by bats or dolphins. Because, in general, the engineers haven't the chance to observe the natural features of these animals, on the other hand, the zoologists also haven't the tools to approach to the echo location mechanism. Project investigators are organized by engineers, zoologists and physiologists, and they are divided into two groops, one is for bats and the other is for dolphins. Usual discussions are perforned using the inter-net, so that the frequent and quick responses are realized over all investigators of this project. To discuss the obtained results of each investigators in directly, whole meeting were held five times. The creative discussion were perfornrd in the cooperative observations of echo location signals of bats and dolphins. The cooperative observations were also held two times.
    Obtained results show that the bio-SONAR has many advantages compare with the artificial SONAR in the features of small size in dimension, signal processing ability and flexibility. Especially, processing way of echo signal in brain gives us important suggestion, that is, in the bio-SONAR, the combination of time and frequency domain analyses just like the sonagram is skillfully used to recognize the circumstance information in their telangiectasia and brain center in instantaneously, For the engineering application, it is expected that the algorithm of signal processing in human auditory sense can applicable to study the echo location mechanism.

▼display all

Misc

  • Effect of Noise on Aquatic Animals

      44 ( 2 ) 83 - 85  2017.04

    CiNii

  • The effect of underwater ship noise on humpback whales in the waters of Ogasawara (Bonin) Islands, Japan

    Kyoichi Mori, Ryosuke Okamato, Koki Tsujii, Tomonari Akamatsu, Naoya Umeda, Yoko Mitani, Rina Yamada, Takahiro Kijima

    The JSFS 85th Anniversary-Commemorative International Symposium “Fisheries Science for Future Generations” Abstract     03002 - 03002  2017  [Refereed]

  • Reactions of singing behavior of humpback whales to ship noise off ogasawara island, Tokyo

    Tomonari Akamatsu, Ryosuke Okamoto, Kyoichi Mori, Yoko Mitani, Kouki Tsujii, Toshio Tsuchiya, Takahiro Kijima, Naoya Umeda

    OCEANOISE2017     71 - 71  2017  [Refereed]

  • Survey and analysis methods for conservation and management of marine mammals(4)Acoustics

      38 ( 5 ) 570 - 577  2016.10

    Article, review, commentary, editorial, etc. (trade magazine, newspaper, online media)  

    CiNii

  • バイオロギングによる水圏生物の行動情報の取得1 フィールドミュージアムにむけたアマゾン川の魚類のテレメトリーモニタリング

    丸尾優子, 三田村啓理, 荒井修亮, 赤松友成, 山本友紀子, Jose Alves-Gomes

    平成28年度日本水産学会春季大会    2016.03

    Research paper, summary (national, other academic conference)  

  • 小型鯨類の行動情報の取得2 福島県沖合における小型鯨類種別来遊状況

    亀山紗穂, 赤松友成, 荒井修亮

    平成28年度日本水産学会春季大会    2016.03

    Research paper, summary (national, other academic conference)  

  • 小型鯨類の行動情報の取得1 三河湾湾口部における2013年10月のスナメリ来遊状況

    和田杏映, 木村里子, 依田憲, 赤松友成, 荒井修亮

    平成28年度日本水産学会春季大会    2016.03

    Research paper, summary (national, other academic conference)  

  • Diversity of Marine Mammal Vocalizations off Rausu, Shiretoko, Northern Japan

    Mayuko Otsuki, Tomonari Akamatsu, Takahiro Nobetsu, Yoko Mitani

    TECHNO-OCEAN 2016: RETURN TO THE OCEANS     45 - 48  2016

     View Summary

    A number of marine mammal species travel off Rausu, Shiretoko as feeding and breeding habitats, providing resources for tourism. However, seasonal sea ice and severe weather conditions have restricted visual observations of marine mammals off Rausu except for daytime observations between spring and fall. To compensate for this lack of information, fixed passive acoustic recording devices were deployed to monitor the presence of marine mammals during November 2012-March 2014. Pacific white-sided dolphin (Lagenorhynchus obliquidens) burst pulsed calls in July, November, and December; ribbon seal (Histriophoca fasciata) downsweeps in February and March; killer whale (Orcinus orca) pulsed calls from April to August; and sperm whale (Physeter macrocephalus) clicks in July and August were detected. Cetacean species were possibly involved in foraging since their pulsed calls or clicks were often detected during foraging. In contrast, ribbon seals were possibly involved in breeding behaviours as seal vocalizations are likely related to breeding activities. This passive acoustic monitoring will provide new insights into the ecology of diverse marine mammals off Rausu.

    DOI

  • An attempt to estimate ship noise effect on humpback whales in Japa

    Tomonari Akamatsu, Ryosuke Okamoto, Kyoichi Mori, Yoko Mitani, Kouki Tsujii, Toshio Tsuchiya, Takahiro Kijima, Naoya Umeda

    The Journal of the Acoustical Society of America   140   3021  2016  [Refereed]

    Research paper, summary (international conference)  

  • 三河湾湾口におけるスナメリの定点音響観測

    和田杏映, 木村里子, 依田憲, 赤松友成, 荒井修亮

    海洋理工学会平成27年度秋季大会    2015.10

    Research paper, summary (national, other academic conference)  

  • A newly developing assessment method using vocalizations of dolphins

    Akamatsu Tomonari

    The Journal of the Acoustical Society of Japan   71 ( 8 ) 404 - 408  2015.08

    CiNii

  • 洋上風力発電施設建設予定海域におけるイルカの来遊状況

    亀山紗穂, 赤松友成, 荒井修亮

    海洋理工学会平成27年度春季大会    2015.05

    Research paper, summary (national, other academic conference)  

  • 設置型水中録音装置を用いたチャクチ海南部におけるナガスクジラ(Balaenoptera physalus)の鳴音モニタリング

    辻井浩希, 大槻真友子, 赤松友成, 赤松友成, 松尾行雄, 松尾行雄, 甘糟和男, 喜多村稔, 菊地隆, 宮下和士, 三谷曜子

    日本水産学会大会講演要旨集   2015  2015

    J-GLOBAL

  • 洋上風力発電が海洋生態系に及ぼす影響の評価手法:小型鯨類の音響調査について

    木村里子, 赤松友成, 村元宏行

    海洋理工学会誌   21 ( 2 ) 31 - 35  2015

    Article, review, commentary, editorial, etc. (scientific journal)  

    DOI

  • Detection and communication of whales by low frequency underwater sounds

    Akamatsu Tomonari

    The Journal of the Acoustical Society of Japan   70 ( 11 ) 615 - 620  2014.11

    CiNii

  • 知床羅臼沖における海棲哺乳類の受動式音響モニタリング

    大槻真友子, 赤松友成, 安部幸樹, 野別貴博, 桜井泰憲, 三谷曜子, 宮下和士

    日本水産学会大会講演要旨集   2014  2014

    J-GLOBAL

  • Passive Acoustic Monitoring of Marine Organisms

      40 ( 3 ) 211 - 216  2013.07

    CiNii

  • Noise Control for Whales

    AKAMATSU Tomonari

      37 ( 1 ) 10 - 12  2013.02

    CiNii

  • 音で調べる海の中 (特集 生物が記録する科学 : バイオロギングサイエンス)

    森阪 匡通, 赤松 友成

    Milsil : 自然と科学の情報誌   5 ( 1 ) 11 - 13  2012.01

    CiNii

  • How to Count Aquatic Animals by Listening to their Vocalizations?

    AKAMATSU Tomonari

      60 ( 7 ) 376 - 383  2011.07

    CiNii

  • The depth of water effects the feeding ground selection by dugongs in dry season

    AMAMOTO Nanako, ICHIKAWA Kotaro, ARAI Nobuaki, AKAMATSU Tomonari, SHINKE Tomio, ADULYANUKOSOL Kanjana

      15 ( 2 ) 149 - 157  2010.04

    CiNii

  • Fish Detection System by Using the Broadband Ultrasound

    MATSUO Ikuo, AKAMATSU Tomonari, NISHIMORI Yasushi

      49 ( 1 ) 51 - 55  2010.01

    CiNii

  • Passive acoustic observations of the Dugongs in Thailand

    ICHIKAWA Kotaro, ARAI Nobuaki, AKAMATSU Tomonari, SHINKE Tomio, ADULYANUKOSOL Kanjana

    Journal of Advanced Marine Science and Technology Society   15 ( 1 ) 63 - 66  2009.11

    CiNii

  • 漁船をプラットフォームとした海洋資源の自動観測網構想

    赤松 友成

    海洋水産エンジニアリング   9 ( 88 ) 83 - 87  2009.11

    CiNii

  • 見えないスナメリを勘定するための音響調査

    赤松友成

    勇魚   48 ( 48 ) 13 - 16  2008.06

    CiNii

  • 受動的音響手法によるヨウスコウスナメリの発見確率推定\日本音響学会聴覚研究会資料

    赤松友成, Wang D, Wang K, Li S, Dong S, Zhao X, Barlow J, Stewart B.S, Richlen M

    日本音響学会聴覚研究会資料   38 ( 3 ) 233 - 241  2008.05

  • 熱帯性海草藻場の再生に関する検討-ジュゴンと漁業の共生を目指して-

    内田詮三, 諸喜田茂充, 荒井修亮, 当真武, 林原毅, 赤松友成, 松田秋彦, 海老沢明彦

    水産庁 独立行政法人水産総合研究センター    2008.03

  • Cetacean bioacoustics with emphasis on recording and monitoring

    Tomonari Akamatsu

    Handbook of Signal Processing in Acoustics Springer, New York   2   1897 - 1907  2008

  • Recent advances in Bio-logging science and technology in Asia: Japan-China Bio-logging Science Symposium (JC-BLOSS)

    Kexiong Wang, Tomonari Akamatsu, Ding Wang

    Environmental Science and Pollution Research   15 ( 3 ) 173 - 175  2008

    DOI PubMed

  • 魚を判別できるイルカ型ソナーをつくる

    赤松友成

    物理科学雑誌パリティ200803   23 ( 03 ) 60 - 64  2008

  • イルカやクジラの声を録ろう

    赤松友成

    DIVING WORLD   200802 ( 390 ) 60 - 63  2008

  • 魚の鳴き声を聴いて資源を測る

    赤松友成

    農林水産技術研究ジャーナル   31 ( 1 ) 41 - 43  2008

  • 魚を判別できるイルカ型ソナーをつくる

    赤松友成

    物理科学雑誌パリティ200803   23 ( 03 ) 60 - 64  2008

    CiNii

  • イルカやクジラの声を録ろう

    赤松友成

    DIVING WORLD   200802 ( 390 ) 60 - 63  2008

  • 魚の鳴き声を聴いて資源を測る

    赤松友成

    農林水産技術研究ジャーナル   31 ( 1 ) 41 - 43  2008

    CiNii

  • Underwater acoustical sensing behavior of porpoises

    Tomonari Akamatsu, Ding Wang, Kexiong Wang, Yasuhiko Naito

    BIO-MECHANISMS OF SWIMMING AND FLYING: FLUID DYNAMICS, BIOMIMETIC ROBOTS, AND SPORTS SCIENCE     117 - +  2008

     View Summary

    Detecting objects in their paths is a fundamental perceptional function of moving organisms. Potential risks and rewards, such as prey, predators, conspecifics or non-biological obstacles, must be detected so that an animal can modify its behavior accordingly. However, to date few studies have considered how animals in the wild focus their attention. Dolphins and porpoises are known to actively use sonar or echolocation. A newly developed miniature data logger attached to a porpoise allows for individual recording of acoustical search efforts and inspection distance based on echolocation. In this study, we analyzed the biosonar behavior of eight free-ranging finless porpoises and demonstrated that these animals inspect the area ahead of them before swimming silently into it as depicted in the figure. Before to get out of the inspected area, the porpoise use sonar. The porpoises inspected distances up to 77 m, whereas their swimming distance without using sonar was less than 20 m. The inspection distance was long enough to ensure a wide safety margin before facing real risks or rewards. Once a potential prey item was detected, porpoises adjusted their inspection distance from the remote target throughout their approach. Application of biosonar for biomimetic sonar is discussed.

    DOI

  • 「ホイッスル」「クリックス」「ザトウクジラの歌」写真掲載

    赤松友成

    (株)浜島書店刊「国語の学習1年」     26  2007

  • 日本の水中生物音響学の黎明期

    赤松友成

    海洋音響学会誌 J.Marine Acoust.Soc.Jpn   34 ( 4 )  2007

  • イルカのハイパ-センサ

    赤松友成

    バイオメカニズム学会誌   31 ( 3 ) 134 - 137  2007

     View Summary

    イルカは哺乳類としての制約条件のもと,超音波の送受信で周辺を認知できるソナー能力を進化させてきた.イルカの有するソナーは高い空間分解能と高度な対象判別能力を持っている.これまでの魚群探知機がモノクロテレビであったとしたら,イルカ型ソナーはハイビジョンテレビと言えるだろう.イルカのような広帯域ソナーを漁業資源探査に応用すべく,私たちの研究チームではイルカソナーシミュレータを構築し,実証機開発に向けた準備が進んでいる.

    DOI CiNii

  • Underwater Acoustical Sensing Behavior of Porpoises\Bio-mechanisms of Swimming and Flying

    Tomonari Akamatsu, Ding Wang, Kexiong Wang, Yasuhiko Naito

    Bio-mechanisms of Swimming and Flying    2007

     View Summary

    Springer 2007

  • Comparison of echolocation behaviour between coastal and riverine porpoises

    Tomonari Akamatsu, Jonas Teilmann, Lee A. Miller, Jakob Tougaard, Rune Dietz, Ding Wang, Kexiong Wang, Ursula Siebert, Yasuhiko Naito

    DEEP-SEA RESEARCH PART II-TOPICAL STUDIES IN OCEANOGRAPHY   54 ( 3-4 ) 290 - 297  2007

     View Summary

    Echolocation behaviour of a harbor porpoise and six finless porpoises was recorded in open-water systems using acoustic data loggers (A-tag). In total 1359 click trains were recorded during 4.6 h for the harbor porpoise and 46,240 click trains were recorded during 82.3 h for the finless porpoises. The harbor and finless porpoises produced sonar click trains every 12.3 and 6.4 s on average, respectively. During the inter-click-train interval, the porpoises were silent or produced clicks below 148 dB re. 1 mu Pa, the detection threshold of the tag. Ninety percent of the inter-click-train intervals were 20 s or less in both species. This means that porpoises frequently produce intense click trains. Click-train intervals lasting over 50 s constituted 1% of the total intervals in finless porpoises and 4% in the harbor porpoise. Both species swam without intense clicks for less than 10 in in most cases, but occasionally remained silent or used undetected low-intensity clicks for more than 1 min. During these periods, the porpoises would be susceptible to entanglement in fishing nets. (c) 2007 Elsevier Ltd. All rights reserved.

    DOI

  • 「ホイッスル」「クリックス」「ザトウクジラの歌」写真掲載

    赤松友成

    (株)浜島書店刊「国語の学習1年」     26  2007

  • 日本の水中生物音響学の黎明期

    赤松友成

    海洋音響学会誌 J.Marine Acoust.Soc.Jpn   34 ( 4 ) 247 - 251  2007

    CiNii

  • イルカのハイパ-センサ

    赤松友成

    バイオメカニズム学会誌   31 ( 3 ) 134 - 137  2007

    DOI

  • Forthcoming fish echo sounder : a model of dolphin mimetic sonar

    AKAMATSU Tomonari

      29 ( 11 ) 20 - 24  2006.11

    CiNii

  • ハクジラのソーナー音を用いた散乱振幅の周波数特性の測定

    今泉 智人, 古澤 昌彦, 赤松 友成

    海洋音響学会誌   33 ( 3 ) 143 - 150  2006.07

    CiNii

  • New Stereo Acoustic Data Logger for Free-ranging Dolphins and Porpoises

    AKAMATSU Tomonari, MATSUDA Akihiko, SUZUKI Shiro, WANG Ding, WANG Kexiong, SUZUKI Michihiko, MURAMOTO Hiroyuki, SUGIYAMA Naoki, OOTA Katsunori

    Journal of Advanced Marine Science and Technology Society   11 ( 2 ) 65 - 71  2006.04

    CiNii

  • スナメリのソナー行動

    赤松 友成, 王 丁, 王 克雄

    海洋音響学会誌   33 ( 2 ) 106 - 112  2006.04

    CiNii

  • Monitoring the feeding behavior of dugongs in the seagrass bed of a tidal flat

    TSUTSUMI Chika, ICHIKAWA Kotaro, AKAMATSU Tomonari, ARAI Nobuaki, SHINKE Tomio, HARA Takeshi, ADULYANUKOSOL Kanjana

    Journal of Advanced Marine Science and Technology Society   11 ( 1 ) 77 - 80  2005.10

    CiNii

  • Locating Positions of Dugongs Using Their Calls

    ICHIKAWA Kotaro, SHINKE Tomio, ITO Mayuko, ARAI Nobuaki, AKAMATSU Tomonari, HOSOYA Seiichi, HARA Takeshi, ADULYANUKOSOL Kanjana

    Journal of Advanced Marine Science and Technology Society   9 ( 2 ) 221 - 226  2004.06

    CiNii

  • 2003年度第1回シンポジウム発表要旨 イルカの音響行動の観察システム--音響データロガーの開発

    赤松 友成, 王 丁, 王 克雄

    海洋音響学会誌   31 ( 2 ) 111 - 113  2004.04

    CiNii

  • Environmental ambient noise influence on the acoustic signals of the Indo-Pacific bottlenose dolphins

    Morisaka Tadamichi, Shinohara Masanori, Nakahara Fumio, Akamatsu Tomonari

    Abstracts of the Annual Meeting of the Ecological Society of Japan   51 ( 0 ) 657 - 657  2004

    DOI CiNii

  • A Monitoring System for the Aggregated Fish Group by an Acoustic-Visual Combined Method

    TOMONARI AKAMATSU, HIDEYUKI TAKAHASHI, AKIHIKO MATSUDA, National Research Institute of Fisheries Engineering Fisheries Research Agency, National Research Institute of Fisheries Engineering Fisheries Research Agency, National Research Institute of Fisheries Engineering Fisheries Research Agency

      68 ( 5 ) 747 - 748  2002.09

    CiNii

  • 講座 海洋計測(1)クジラとイルカを声で見る

    赤松 友成

    海洋音響学会誌   29 ( 2 ) 61 - 66  2002.04

    CiNii

  • A note on measuring fish sounds and hearing ability in small tanks

    OKUMURA T., AKAMATSU T, YAN Hong Y., NOVARINI Nicola

      2002 ( 1 ) 489 - 490  2002.03

    CiNii

  • The measurement of hearing sensitivity of Sardinops melanostictus using ABR technique

    NANAMI A., AKAMATSU T., YAN Hong Y.

      2002 ( 1 ) 487 - 488  2002.03

    CiNii

  • Echolocation range of dolphins

    AKAMATSU T., WANG Ding, WANG Kexiong, WEI Zhuo, NAITO Y.

      2002 ( 1 ) 485 - 486  2002.03

    CiNii

  • イルカの聴覚 (平成12年度第1回〔海洋音響学会〕シンポジウム発表要旨)

    赤松 友成

    海洋音響学会誌   28 ( 2 ) 91 - 94  2001.04

    CiNii

  • 水中生物の音響行動学

    赤松 友成

    日本音響学会誌   52 ( 11 ) 921 - 921  1996.11

    CiNii

  • Echolocation of dolphins and their vocalization strategy.

    AKAMATSU Tomonari

    The Journal of the Acoustical Society of Japan   52 ( 7 ) 523 - 528  1996.07

    CiNii

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