Crab Response to Prey Density Can Result in Density-Dependent Mortality of Clams

Abstract

Field experiments involving recovery of marked clams showed that even adult native littleneck clams (Protothaca staminea) could suffer high mortality to cancrid crabs. The mortality rate increased with clam density, suggesting that these crabs preferentially forage in areas of higher prey density. Acoustic telemetry showed that at least one of the crabs, Cancer productus, is sufficiently mobile to search large areas while foraging. This is important for understanding the effects that these large, mobile predators have on the distribution and the abundance of their prey and may explain the high incidence of crab predation seen in mariculture operations where the density of clams is artificially raised.