Water velocity in artificial habitats of the Japanese crayfish Cambaroides japonicus

The appropriate water velocity in artificial burrows for the Japanese crayfish species Cambaroides japonicus was studied. An experimental system of two artificial burrows (burrows A and B) of the same size was set in a large tank. The velocity of burrow A was 0 cm/s and that of burrow B was varied and set at 0 cm/s, 5 cm/s, 10 cm/s, 20 cm/s and 30 cm/s. The selection of these two burrows by C. japonicus was observed. No animals selected burrow B significantly more than burrow A above 10 cm/s. At 20 cm/s, some crayfishes were swept away and could not return to burrows because of the high water velocity. At 30 cm/s, most animals were swept away. We conclude that the appropriate water velocity for the suitability of artificial burrows and the immediate foraging area adjacent to the burrows should be as low as 5 cm/s.