Why do decapod crustaceans prefer small-sized molluscan prey?

A survey of studies examining crab and lobster predation on hard-shelled molluscs indicated that most predators prefer small-sized prey when offered a range of sizes.I suggest that this pattern of preference for small-sized prey can be explained by considering the mechanical cost of predation.If predation costs are assumed to be non-renewable, then the probability of exhausting them can be included as an additional parameter in the classical diet breadth model.The importance of predation costs in determining prey size selection can be extended to other predators that use mechanical means to attack their prey.