Combining acoustic telemetry with biochemical tracers reveals habitat use by a demersal mesopredator, Hypanus sabinus

Knowledge of mesopredator habitat use and trophic ecology is crucial for identifying essential habitat and understanding community and food web dynamics. Defining functional roles of resting elasmobranchs is especially important, as they can influence benthic community dynamics by residing in an area for a considerable amount of time. This study combines acoustic telemetry, bulk stable isotope analysis (δ¹³C and δ¹⁵N), and carbon isotope analysis of essential amino acids (δ¹³C_EAA) to investigate the habitat use and trophic ecology of Atlantic stingrays Hypanus sabinus within a subtropical estuary. Diel period, tide height (m), moon illumination, and water temperature (°C) significantly influenced hourly presence of stingrays. Stingray presence increased in water temperatures ranging from 15 to 25°C, and they were more likely to be absent when temperatures were <10 and >30°C. Bulk δ¹³C and δ¹⁵N values from stingray tissues exhibited spatial gradients throughout the estuary, likely due to isotopic variability in baseline resource channels (e.g. macroalgae) and dietary differences between individual stingrays. Linear discriminant analysis of δ¹³C_EAA values indicated trophic assimilation of macroalgal essential amino acids, demonstrating that the observed spatial gradient in bulk δ¹³C values may be driven by differential ¹³C fractionation in macroalgae across space due to environmental conditions, or potentially different species of macroalgae occurring throughout the estuary. These findings provide key insight into the relationship between habitat use and trophic ecology of stingrays, revealing potential responses of vulnerable elasmobranch consumers to future physical and biogeochemical changes within estuarine environments.