Stable isotopes and vertebrae microchemistry reveal crucial habitats for three heavily fished coastal stingrays in the Western Atlantic Ocean

Abstract

Demand for ray consumption has been increasing considerably along coastal areas of the Western Atlantic Ocean, especially Northeast Brazil. Species previously caught as bycatch are now targeted by fisheries but the available information on these species remains scarce. In the present study, we provide the first application of stable isotopes from muscle tissue (δ¹³C and δ¹⁵N) and vertebrae microchemistry (²⁴Mg, ⁴³Ca, ⁵⁵Mn, ⁸⁶Sr, ¹³⁸Ba) data to analyze the habitat use of batoids. We employ these techniques on three sympatric demersal stingray species across different life stages. Our approach revealed entry and exit movements in estuarine areas by Hypanus guttatus, a strong specificity for coastal reef habitats for Hypanus marianae, and the use of deeper waters by adults of Hypanus berthalutzae. We also found significant between-sex differences in habitat use for H. berthalutzae, especially for elements associated with hypoxic zones (⁵⁵Mn) and salinity variations (⁸⁶Sr and ¹³⁸Ba), suggesting that males move to deeper areas farther from the coast during ontogeny. Both data sources employed were considered good descriptors for the various environments these species are found in. Our results suggest that mangroves and coral reefs are the most important areas for H. guttatus and H. marianae, respectively, while H. berthalutzae seems to use the entire continental shelf throughout its life cycle. We further discuss how these results may translate into each species distribution range and fishing pressure.