Seasonal dynamics in the trophic ecology and condition of a marine, benthic mesopredator, the southern stingray, Hypanus americanus

Abstract

Mesopredators contribute to food web stability and as such, understanding their trophic ecology can help to predict potential consequences of ongoing ecosystem modification. Here, multi-tissue carbon and nitrogen stable isotope analysis ({delta}13C and {delta}15N) and biochemical blood parameters ({beta}-hydroxybutyrate, glucose, lactate, and osmolality) were used to assess sex, size, spatial and seasonal differences in trophic ecology and condition of southern stingrays, Hypanus americanus, in Bimini, The Bahamas. Stingrays exhibited a dietary preference for molluscs and annelids, with an ontogenetic shift towards lower {delta}13C with increasing body size indicating a shift towards more mangrove associated prey. Nitrogen isotope values showed minimal seasonal changes, but higher {delta}15N values in males indicated foraging at a higher trophic level than females. Blood {beta}-hydroxybutyrate concentrations and osmolality revealed a similar energetic state and condition between sex, size, location and season. Our results advance our understanding of the seasonal trophic ecology of a benthic, marine mesopredator and identify the southern stingray as an important trophic link in seagrass and mangrove habitats in Bimini.