LEVERAGING AQUARIUM SAND TIGER SHARKS (CARCHARIAS TAURUS) TO DEVELOP CHEMICAL TRACER TOOLS FOR DIET STUDIES IN THE WILD

Abstract

Understanding the diet and ecosystem roles of large coastal sharks is critical for species ecology and ecosystem dynamics. However, traditional studies use lethal or invasive sampling to study diet in large elasmobranchs, which is not realistic for a prohibited and protected species. This study uses a non-lethal chemical tracer (stable isotope analysis, SIA) to study the diet, ecology, and energy use of Sand Tiger Sharks (Carcharias taurus) in the Northwest Atlantic subpopulation. The use of SIA in the wild hinges upon accurate estimates for key chemical dynamics; trophic discrimination factors (TDF) and turnover. We first utilize Sand Tiger Sharks in collaboration with Ripley’s Aquarium of Myrtle Beach to conduct a semi-controlled aquarium study to estimate these chemical dynamics in blood. We estimate the TDF and turnover rates of δ13C, δ15N, and δ34S in plasma and red blood cells of adult Sand Tiger Sharks. We then apply these values for TDF and turnover to wild Sand Tiger Sharks sampled in Delaware Bay between 2019–2024. By pairing plasma and red blood cell SIA data with DNA metabarcoding from cloacal swabs, we find that Sand Tiger Sharks most likely rely heavily on coastal ray species, small elasmobranchs, and lipid-rich filter feeders during the summer in Delaware Bay. Using muscle SIA, we find that the Mid-Atlantic region contributes more than 60% to long-term energy use of Sand Tiger Sharks, pointing to this area being important foraging habitat for this species.