How can the feeding habits of the sand tiger shark influence the success of conservation programs?

Abstract

The feeding habits of the sand tiger shark Carcharias taurus, one of the most threatened sharks of the world, are poorly known. Sand tiger sharks are critically endangered in the South-west Atlantic. Since 2007, the law requires that all individuals caught in recreational fisheries off Argentina must be released. Using data from a north Patagonian recreational fishery (n = 164 stomachs with contents), we analyzed the diet of sand tiger sharks in relation with size, sex, maturity stage and season; assessed prey consumption patterns and hooking location; and estimated diet overlap with fishery landings. Sand tiger sharks consumed mainly teleosts (55.4% of the total prey number, N) and elasmobranchs (41.84% N), and ate more benthic elasmobranchs (batoids and angel sharks) as they become larger. Sharks swallowed prey mostly in one piece (93.7%) and were hooked mainly in internal organs (87.4%, n = 175), causing occlusion and perforation of the esophagus and stomach, and lacerations to the pericardium, heart and liver. Sand tiger sharks fed on the most heavily landed species, overlapping almost completely (>90%) with fishery landings. Conservation plans should take into account that releasing hooked sharks could be insufficient to minimize fishing mortality and that competition for food with fisheries is likely to occur. © Journal compilation © 2009 The Zoological Society of London.