Hard prey specialists or opportunistic generalists? An examination of the diet of the cownose ray, Rhinoptera bonasus

摘要: Atlantic cownose rays (Rhinoptera bonasus) are benthic, suction feeders whose foraging activities have been implicated in severe damage to commercial shellfish industries. With jaws highly modified for durophagy, it has assumed that R. bonasus crushing specialists feed primarily upon hard molluscan prey. Stomach contents from caught within Florida’s Charlotte Harbor estuary between July 2003 and 2004 were analysed using the index of relative importance (IRI) determine most important prey types. Prey items identified 38 families fell into nine distinctive groups. The three dominant groups crustaceans (%IRI = 55.31), polychaetes 25.20) bivalves 12.58). Shoalmates had more similar diets than non-shoalmates, suggesting group feeding. Most small or softer-bodied consumed relatively intact, indicating lack processing capture through All larger, harder-bodied showed evidence (fractured broken shells). Although characterised as a specialist, these results suggest may behave an opportunistic generalist, modifying feeding behaviour consume readily available