Diet Reconstruction and Resource Partitioning of a Caribbean Marine Mesopredator Using Stable Isotope Bayesian Modelling

Abstract

The trophic ecology of epibenthic mesopredators is not well understood in terms of prey partitioning with sympatric elasmobranchs or their effects on prey communities, yet the importance of omnivores in community trophic dynamics is being increasingly realised. This study used stable isotope analysis of 15N and 13C to model diet composition of wild southern stingrays Dasyatis americana and compare trophic niche space to nurse sharks Ginglymostoma cirratum and Caribbean reef sharks Carcharhinus perezi on Glovers Reef Atoll, Belize. Bayesian stable isotope mixing models were used to investigate prey choice as well as viable Diet-Tissue Discrimination Factors for use with stingrays. Stingray δ15N values showed the greatest variation and a positive relationship with size, with an isotopic niche width approximately twice that of sympatric species. Shark species exhibited comparatively restricted δ15N values and greater δ13C variation, with very little overlap of stingray niche space. Mixing models suggest bivalves and annelids are proportionally more important prey in the stingray diet than crustaceans and teleosts at Glovers Reef, in contrast to all but one published diet study using stomach contents from other locations. Incorporating gut contents information from the literature, we suggest diet-tissue discrimination factors values of Δ15N ≊ 2.7‰ and Δ13C ≊ 0.9‰ for stingrays in the absence of validation experiments. The wide trophic niche and lower trophic level exhibited by stingrays compared to sympatric sharks supports their putative role as important base stabilisers in benthic systems, with the potential to absorb trophic perturbations through numerous opportunistic prey interactions.

Linking foraging behavior and diet in a diving seabird

“…) and marine mammals (Eder & Lewis ; Tilley et al . ). In general, individuals presented intermediate nitrogen isotopic signatures in blood plasma, presumably linked to feeding on benthic fish ( Raneya brasiliensis and Riberoclinus eigenmanni ).…”

Dietary composition and prey selectivity of juvenile porcupine raysUrogymnus asperrimus

“…Most dietary studies of myliobatoids have occurred along continental coastlines because of their ease of access (Ebert & Cowley, ; Ajemian & Powers, ; O'Shea et al ., ; Bornatowski et al ., ; Costa et al ., ), while dietary studies at remote atolls are comparatively few (Tilley et al . ).…”

“…Myliobatoids, however, are also known to occur in oceanic atolls, which are insular areas of high productivity surrounded by open ocean that is characterized by low productivity (Rayner & Drew, 1984). Most dietary studies of myliobatoids have occurred along continental coastlines because of their ease of access (Ebert & Cowley, 2003;O'Shea et al, 2013;Bornatowski et al, 2014;Costa et al, 2015), while dietary studies at remote atolls are comparatively few (Tilley et al 2013).…”

Combined gut-content and stable isotope trophic analysis of the pelagic stingray Pteroplaytrygon violacea (Bonaparte, 1832) diet from the western North Atlantic Ocean

“…The majority of elasmobranch species values taken from the literature appeared to have relied upon prey that utilized a similar carbon source (inshore vs offshore) but were one to two trophic levels more enriched than the pelagic stingrays themselves (Estrada et al., ; Rau et al., ). Three nearshore elasmobranch species were incorporated into Figure to give reference that the pelagic stingrays were likely utilizing an offshore carbon source (Tilley, López‐Angarita, & Turner, ). The teleost species with a similar carbon value, and potential source, to the pelagic stingrays were all more enriched trophically and could not have contributed significantly to their diets.…”