Influence of Sediment Type on Antipredator Response of the Softshell Clam,Mya arenaria

Abstract

Mya arenaria (Softshell Clam) inhabit a wide range of intertidal and subtidal sediment types in the western North Atlantic. They avoid predation by burrowing deeply in the sediment. We investigated the effect of sediment type on the antipredator responses of Softshell Clams to Carcinus maenas (Green Crab) as well as the relative costs and benefits of living in different sediment types. Clam burrowing depth, growth, and Green Crab predation rate were observed in experimental plots of mud, sand, and gravel. Clams exposed to crabs burrowed deeper than did control clams in all sediment types, but clams burrowed deepest in finer sediment types. Clams in coarser sediments also had thicker shells and suffered lower rates of predation than did those in mud. These results suggest distinctive costs and benefits associated with inhabiting different sediment types. For Softshell Clams, coarse sediments are most costly metabolically, but have lower predation risk compared to finer sediments.