Cambaroides japonicus a freshwater crayfish endemic to Japan that occurs in northern Tohoku and Hokkaido. Its populations are known to be decreasing in site, but there have been few studies ...describing its lifehistory, especially in southern Hokkaido. In the present study, life history characters of C. japonicus in southern Hokkaido are described and compared among local populations. Contrasting differences were found in body size of males, females and youngsat sites named A, B, and Ca-Cd. Males were larger at sites Ca, Cb, and Cd than at sites A and B, and females were larger at sites Ca and Cb than at sites A, but juveniles were smaller at sites Ca, Cb, Cd than at sites A and B. Clutch size was smaller at site B than at site C, and egg size was larger at site B than at sites A and C. The spawning season and length of breeding period both appeared to differ among research sites. This study demonstrates that the life history of C. japonicus differs among populations. The local populations are known to vary genetically, so the phenotypic variations in life history characters may be caused by genetic differences.
