Novel insights into the diet of southern stingrays and Caribbean whiptail rays

Caribbean whiptail and southern stingrays are large-bodied mesopredators, occupying shallow, nearshore ecosystems of The Bahamas, yet virtually nothing is known of their diet or potential resource competition. We used stomach content analysis via gastric lavage and stable isotope analysis to investigate the diet of 94 Caribbean whiptail rays Styracura schmardae and 112 southern stingrays Hypanus americanus across 3 locations in the central Bahamas. Gastric lavage was used to identify prey consumed and compared to stable isotope analysis of δ 15 N, δ 13 C and δ 34 S of barb, muscle, blood and skin, representing different temporal integration periods. Both species appeared to consume a majority of crustaceans and annelids, although δ 13 C values suggested that Caribbean whiptail rays have larger isotopic niche space across isotopes sampled (potentially broader diet) than southern stingrays, ranging from 5.82-3.43‰ 2 , and a greater variance in δ 13 C. This suggests Caribbean whiptail rays potentially feed on prey from either a wider geographic range or from different habitats. Caribbean whiptail and southern stingrays are known to spatio-temporally overlap, and their isotopic niche overlapped by 35.6%. This study represents the first integrated diet estimate for southern stingrays obtained using multiple techniques, and the first ever diet assessment in Caribbean whiptail rays. These data are critical for conservation of coastal ray species and management of coastal and nearshore environments throughout the region.