The effect of cheliped loss on blue crab Callinectes sapidus Rathbun foraging rate on soft-shell clams Mya arenaria L.

Abstract

Loss of single chelipeds was common (4–17%) in populations of blue crab Callinectes sapidus Rathbun surveyed in Chesapeake Bay and along the southeastern Atlantic coast and Gulf of Mexico. In contrast, blue crabs missing both chelipeds were relatively rare (0–5%). Laboratory experiments were conducted to determine the effects of cheliped autotomy on blue crab foraging rate on soft-shell clams Mya arenaria L. In replicated aquarium experiments, clams (44–72 mm shell length) were allowed 48 h to burrow in sandy substratum before an intact male crab or one missing one or both chelipeds was introduced. After 48 h, clams were checked for evidence of siphon injury or mortality. Foraging rate (clams consumed/48 h) of crabs missing a single crusher cheliped did not differ significantly from that of intact crabs. Blue crabs compensated for the loss of a crusher by using the cutter cheliped and opposite first walking leg to forage. In contrast, crabs missing both chelipeds experienced a greater feeding handicap; their consumption of clams was significantly lower than that of intact crabs. The low incidence of individuals missing both chelipeds suggests that such injury does little to diminish blue crab predation on M. arenaria populations.