Trophic ecology of sympatric juvenile stingrays within a nursery area

Nursery areas are crucial for many elasmobranch species, providing advantages such as increased access to prey and reduced predation risk. This study investigated the trophic interactions of two juvenile stingray species within a coastal communal nursery using stable isotope analysis. Muscle, plasma and red blood cells samples were taken from the mangrove whipray Urogymnus granulatus and the cowtail stingray Pastinachus ater, and δ15N, δ13C and δ34S measured. Urogymnus granulatus had higher mean δ13C, δ15N and δ34S than P. ater. General linear models showed no significant trends between δ13C, δ15N or δ34S and body size or sex. Low isotopic niche overlap, combined with previous data on movement patterns, provided evidence of niche partitioning between stingrays that likely reflect differences in feeding grounds and prey selection. Despite the differences in feeding grounds and prey selection, previous studies showed that U. granulatus and P. ater share sand and reef flat areas for most of the day (20 h). δ13C and δ34S values suggested that mangrove-derived carbon had little importance to stingrays' diets in the study area. Results presented in this study bring new insights to the feeding ecology of two sympatric stingray species and their trophic interactions within a communal nursery area.