Meeting Abstract

P1.52  Sunday, Jan. 4  Prey selection by two species of sharks GERRY, S.P*; SCOTT, A.J.; Arcadia University; University of Rhode Island gerrys@arcadia.edu

The degree of plasticity or degree of specialization of an organism can often determine its distribution within a community. More specifically, the morphology or behavior of a predator can influence resource acquisition. Foraging in the presence or absence of a competitor was investigated by quantifying prey selection in a trophic generalist, spiny dogfish, and a trophic specialist, smooth-hounds, when offered five types of prey. The diet of spiny dogfish consists of small fishes, squid, ctenophores and bivalves. Therefore, dogfish are expected to be nonselective predators and will show no preference for any one prey item. Smooth-hounds have morphological specializations for crushing and primarily feed on crustaceans, thus, they are predicted to select crabs over non-crustacean prey types. Prey selection was quantified according to a selection index that ranks each prey item by the order in which it was consumed. The percentage of consumed prey, missed strikes at a prey and ignored prey were calculated as a proxy for predator efficiency. In the absence of competition, both species showed a preference for herring, squid and shrimp and no preference for crabs. Smooth-hounds frequently selected crabs, but chose not to consume them. Smooth-hounds did not show a feeding specialization according to published diet studies, yet by showing a preference for some prey types, they can be characterized as a selective predator. In the presence of a competitor, spiny dogfish selected four of the five prey items equally, as predicted for a generalist nonselective predator. Similarly, smooth-hounds showed no preference for any one prey type. It is possible that the presence of a competitor influenced both species to select any available prey in order to gain maximum fitness.