Chelal Characteristics and Foraging Behaviour of the Blue CrabCallinectes sapidusRathbun

This paper describes the morphological and mechanical characteristics of the chelae ofCallinectes sapidus, together with the predation techniques, handling times and prey size selection of this voracious predator when presented with marsh mussels,Geukensia demissa, or fiddler crabs,Uca pugilator, in laboratory aquaria.Callinectes sapidusis heterochelous but differences in claw size and mechanical advantage between 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 natural populations is unknown. Previous laboratory experiments investigating the key stimuli used byC. sapiduswhen selecting prey are reviewed, and their results are compared with behaviour predicted by optimal foraging theory. It is concluded that crabs respond to the strongest stimuli received from the prey. Items were rejected after a given persistence time if the attack proved unsuccessful. Persistence time, however, was adjusted through experience to expectations of local prey quality and availability. The integrated result of this key-stimulus mechanism will be a close match to diets predicted by other behavioural models, including that based on optimal foraging theory.