SIZE SELECTION OF ATLANTIC RANGIA CLAMS, RANGIA-CUNEATA, BY BLUE CRABS, CALLINECTES-SAPIDUS

Male blue crabs Callinectes sapidus Rathbun were allowed to forage on six size classes of the Atlantic rangia clam, Rangia cuneata (Sowerby) , in laboratory aquaria under conditions of restricted or unrestricted prey size availability. Prey profitability (energy gained divided by handling time) decreased as prey size increased. Crabs preferred small er clams (1-2 cm long, then 2-3 cm long), as predicted by an energy ma ximization model. Under conditions of restricted prey sizes (nonreplac ement experiments), when the smaller clams were no longer available, c rabs tended to choose progressively larger clams. Crabs did not exhibi t selective feeding behavior among clams larger than 3 cm long. For th e range of crab sizes tested (71-167 nm carapace width), there was no correlation between crab carapace width and the mean clam size that wa s eaten.