CHELAL CHARACTERISTICS AND FORAGING BEHAVIOR OF THE BLUE-CRAB CALLINECTES-SAPIDUS RATHBUN

This paper describes the morphological and mechanical characteristics of the chelae of Callinectes sapidus, together with the predation tech niques, handling times and prey size selection of this voracious preda tor when presented with marsh mussels, Geukensia demissa, or fiddler c rabs, Uca pugilator, in laboratory aquaria. Callinectes sapidus is het erochelous but differences in claw size and mechanical advantage betwe en male and female crabs are statistically indistinguishable. Handling times for mussels and fiddler crabs increased steeply with prey size. Fiddler crabs are intrinsically more profitable than mussels, but the relative costs of capturing mobile prey, or excavating mussels, in na tural populations is unknown. Previous laboratory experiments investig ating the key stimuli used by C. sapidus when selecting prey are revie wed, and their results are compared with behaviour predicted by optima l foraging theory. It is concluded that crabs respond to the strongest stimuli received from the prey. Items were rejected after a given per sistence time if the attack proved unsuccessful. Persistence time, how ever, was adjusted through experience to expectations of local prey qu ality and availability. The integrated result of this key-stimulus mec hanism will be a close match to diets predicted by other behavioural m odels, including that based on optimal foraging theory. (C) 1997 Acade mic Press Limited.