Abstract / Introduction / Summary:
The surveys were conducted at the lower reaches of four rivers; Ohse R., Kametoku R., Shimoda R. and Minato R., in Tokunoshima Island to clarify the fresh- water crustacean decapod fauna in May and September 2020. A total of 2079 shrimps and crabs, divided into 20 species, 13 genus and seven families, was collected in the surveys. Among them seven species, i.e. Macro- brachium formosense, Caridina serratirostris, C. ty- pus, Ptychognathus ishii, P. barbatus, Eriocheir ja- ponicus and Deiratonotus japonicus, account for over 80 % of total number of individuals in each river. The species compositions of four rivers, however, were dif- ferent in each other. The differentiation was discussed considering the river environments.