Food Composition as a Factor Influencing Distribution, Growth, and Survival of the Japanese Endemic Crayfish Cambaroides japonicus (Crustacea: Decapoda)

Habitat characteristics of the endemic Japanese crayfish, Cambaroides japonicus, were investigated with reference to riparian vegetation and macro-invertebrates. During April and October, 2002, 31 brooks and seven lakes were surveyed throughout the Shiribeshi Province of Hokkaido, Japan. Crayfish habitats were characterized by broadleaf (deciduous) trees dominated by Acer mono, in areas that were also the typical habitat of amphipods (Gammaridea). Crayfish did not occur in brooks covered by the coniferous tree Larix kaempferi. Such habitats were inhabited by haplotaxid oligochaetes, but not amphipods. In a laboratory experiment using the four potential diets, deciduous leaves (A. mono), conifer needles (L. kaempferi), dried amphipods (Gammaridea), and deciduous leaves of A. mono together with dried amphipods, juvenile crayfish grew and survived until Stage VI when offered amphipods only and deciduous leaves together with amphipods. In contrast, crayfish did not survive beyond Stage III when reared with only deciduous leaves or conifer needles. It is possible that the rich crude protein (over 34% in content) and fat (over 9%) in amphipods serve as important energy sources for the growth and survival of juvenile crayfish.