One marine protected area is not enough: The trophic ecology of the broadnose sevengill shark (Notorynchus cepedianus) in the Southwest Atlantic

Abstract

AbstractThe broadnose sevengill shark (Notorynchus cepedianus) has been categorized as Vulnerable by the IUCN and shows a declining population trend in the Southwest Atlantic. Bycatch and poaching are the major threats in the region.Although some ecological requirements have been described, there are still several information gaps regarding its ecology. Important aspects of its trophic ecology, like main prey items or key feeding grounds, remain uncertain and are essential to design effective conservation strategies.We applied stable isotope and stomach content analyses to describe the trophic ecology of sevengill shark within a marine protected area of Peninsula Valdés in Patagonia, Argentina.The stomach content analysis determined the southern elephant seal,Mirounga leonina, as the most frequently regurgitated prey item (70%F) during abundance peaks of both species in Península Valdes. The stable isotope analysis indicated that the overall contribution of the elephant seal to the diet of the sevengill shark was around 30% and that this percentage varied with the size of individuals.Present results strengthen the current understanding of the trophic ecology of the sevengill shark. This study confirmed the use of the marine protected area as an essential foraging ground and identified its main prey items. Also, it reinforced the critical need to expand conservation tools beyond this particular coastal protection.