2016 Volume 19 Issue 1 Pages 1-11
The Japanese mitten crab Eriocheir japonica is an edible species commonly inhabiting rivers throughout the Japanese Archipelago. The present study investigated daytime shelter preference of the crab by a field experiment. The riverine experiment was done in an enclosure that was screened with an agricultural plastic netting. The enclosure was composed of sixteen 1-m2 sections, each section with one of the eight different riverbed substrate types (loose boulders with interstices, embedded boulders, loose cobbles with interstices, embedded cobbles, pebbles, sand, leaf litter, or woody debris; each with two replicates). Sixty-nine adult crabs were released into the enclosure and their hiding substrate types during the daytime were observed on a daily basis starting on the following day for 12 consecutive days. Of the total of 334 observations, 61.0% of the crabs were found in loose boulders with interstices, followed by woody debris (21.2%) and loose cobbles with interstices (12.8%). Significant positive rank correlations were observed between the carapace width of the crabs and the dimensions of the interstices used by these individuals (width: τ=0.232, height: τ=0.155, depth: τ=0.091), indicating that the preferred shelter size by E. japonica changes according to the body size.
