本研究の目的は，チャド湖南西部に近年出現した鮮魚取引における漁師－商人関係の実態を，従来の加工魚取引との比較から解明することである。チャド湖は西アフリカ半乾燥帯において重要な魚の供給地であり，古くより加工魚が近隣の国々へと流通した。しかし1970年初期に発生した干ばつによる魚類相の変化や，運搬・保冷技術の向上などを契機に，鮮魚取引が盛んになった。加工魚取引における漁師－商人関係には，互酬的関係や排他的な取引を特徴とするパトロン・クライアント関係が確認されるが，鮮魚取引にはそのような関係はみられない。鮮魚取引の形態は，市場の需要と連動した取引価格のもと，漁獲物と現金との即時交換によるものである。鮮魚を扱う漁師は，移動や漁具に費用をかけず，商品価値は低いながらも安定した漁獲量が望める魚を対象とした出稼ぎ漁を行う。鮮魚を扱う漁師は，不確実性の高い漁業環境において，確実性の高い漁法を採用することでリスクを低減させる生計戦略かつ現金獲得戦略をとっていた。鮮魚取引の活性化は，不安定な気候条件にあるチャド周湖辺地域に生きる漁師の生計を助けるものであるが，同時に，漁獲圧が上昇することで資源の枯渇を招くおそれもある。チャド湖における水産資源の持続的な利用と適切な管理は，今後の重要な課題である。

Since 1995, we have been researching the "Wild Yam Question, " that is, whether or not human beings could live without agricultural products in tropical rainforests. We conducted surveys of the distribution and reserves of yam and yam-like plants and observational surveys of 3 controlled foraging trips, during which the cooperators of the Baka hunter-gatherers could use no agricultural products, in the Ndongo area and showed the possibility human beings be able to live without agricultural products and the high reliability of yam tubers to a foraging life in the tropical rainforest of southeastern Cameroon. But there still remain some issues to be examined. Our 2 controlled foraging trips were done in a forest area which local people rarely visited and was likely to be rich in wild food resources, and the third trip was done in a forest area which they often entered to set snares and was likely to be poor in wild food resources. How does the foraging life style differ between these 2 types of forest? Furthermore, in the previous 2 controlled foraging trips the Baka cooperators used wire-snares, but did not use them on the latest trip as such durable and labor-saving wire-snares would not have been available to Stone Age hunter-gatherers. What difference does the presence or absence of wire-snares make to the foraging life style in tropical rainforests? Based on this survey of a controlled foraging trip in a communal forest which local people communally managed and exploited, we demonstrated that (1) supplying a comparable amount of food to that in remote forests rich in wild food resources, yam tubers remained a staple food for forest foragers even in a communal forest, (2) the present Baka could obtain few game animals without the use of wire snares in the communal forest, (3) game animals, like yam tubers, are a critical food for the foraging lifestyle in southeastern Cameroon forests as their scarcity has a notable impact not only on the hunter-gatherers nutritional intake but also on their emotional state.