平戸島志々伎湾の底生動物群集―II

ヨコエビ類と堆積型による生息場所分析

抄録

Gammarid fauna of many station samples taken from Shijiki Bay were classified into association types based on the cluster analysis of species compositions, and the sediment types were also classified by the similarity analysis of granulometric compositions. A close correlation was found between the distribution of ten gammarid associations and that of four major sediment types in the whole area. In the inner part of the bay where the grain size composition of the habitat units shifted gradual, shift of faunal composition of gammarids in those areas was also gradual. Most of gammarid species have no significant correlations with organic matter content, nitrogen content and shell matter content of the sediment except for four species. The Ampeliscid -dominated community (community II including association types II₁ to II₉) occurred in the central part of the bay, especially, the most dominant species Byblis japonieus occurred on the various sediment types ranging from very fine to coarse sand, accompanying with characteristic subdominant species in different associations. Distinct segregation of sediment type utilization was observed among the species belonging to the same genus such as Ampelisca and Corophium. Distribution patterns of the gammarid associations in the bay are explained by mosaic patterns of sediment types, high correlation between gammarid distributions and sediment types, and by interspecific habitat segregation of some important species.