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

Abstract

Summary The understanding of trophic relationships is vital for correctly modeling ecosystems and ecosystem effects of fisheries removals. The pelagic stingray is found in epipelagic sub‐tropical and tropical waters worldwide and is a common bycatch in pelagic longline fisheries. Between August 2008 and November 2011, 156 specimens (81 males; 75 females) were collected during pelagic longline fishing operations in the US South Atlantic Bight and Gulf of Mexico. Stomach content analyses found that the major prey items were cephalopod molluscs (59.18%), followed by actinopterygiian fishes (37.75%), and decapod crustaceans (35.71%). These concentrations of prey items found in the stomachs coincide with previous studies done in the Pacific Ocean. In contrast to previous studies that found high percentages of empty stomachs (63%), the current percentage of empty stomachs was much lower (25.6%), likely due to shorter times between collection and inspection. Stable isotope analysis (δ13C and δ15N) was performed on white muscle in order to correlate the trophic position with gut‐content analysis. The δ13C values ranged from ‐18.81‰ to ‐16.70‰, while the δ15N ranged from 6.11‰ to 11.88‰. Modeling of stable isotope data suggest that while squid are occasionally an important part of the pelagic stingray diet, prey usually consist of shrimp and other pelagic crustaceans. Pelagic stingrays fed within two trophic levels, but their prey appeared to feed on different carbon sources than those found in other pelagic elasmobranchs. A deeper understanding of the pelagic stingray diet sources can help fisheries management as it begins to transition into ecosystem‐based management.

An annotated checklist of the chondrichthyan fishes inhabiting the northern Gulf of Mexico Part 1: Batoidea

“…Remarks. This is a relatively common, and in some cases significant, bycatch species in commercial pelagic trawl (Bonanomi et al 2018) and longline (Pacheco et al 2011, Dapp et al 2013, Ferrari and Kotas 2013, Gilman et al 2018) fisheries, including within the northern GOM (Weidner et al 2017, Orbesen et al 2017 (Cuvier, 1816) Distribution. This species is reportedly distributed throughout the northern GOM in shallow water, although it appears more prevalent in the eastern GOM.…”

Preliminary assessment of the trophic structure of demersal fish community in the Sea of Oman

“…In this context, stable isotopes of carbon ( 13 C/ 12 C, or δ 13 C) and nitrogen ( 15 N/ 14 N, or δ 15 N) are the most often measured in food web studies (Hobson, 1999;Post, 2002). The combination of stomach content with δ 13 C and δ 15 N analyses is now recognized as a pertinent methodology in order to quantify fish diet and address its spatial and temporal variability in a given ecosystem (Hamidan et al, 2016;Keller et al, 2016;Malek et al, 2016;Olson et al, 2016;Weidner et al, 2017). In addition to carbon and nitrogen isotopic ratios, sulfur isotopes are also useful to trace the origin of the prey consumed by consumers in aquatic ecosystems (Peterson, 1999;Post, 2002;Fry and Chumchal, 2011).…”