Feeding ecology of Atlantic bigeye Priacanthus arenatus (Perciformes: Priacanthidae) from an upwelling ecosystem in the southwestern Atlantic

The Atlantic bigeye Priacanthus arenatus is among the main target species by small-scale fisheries in the southwestern Atlantic. Due to its importance to small-scale fisheries, information regarding its trophic ecology is essential for the development of sustainable management plans. Using combined stomach content (SCA) and stable isotope analysis (SIA), the current study examined Atlantic bigeye feeding ecology, including evidence for ontogenetic and intra-annual (i.e. seasonal) diet variation. The diet of Atlantic bigeye was comprised of 16 prey species but was dominated by pelagic crustaceans (53.3% in number) and pelagic fish (19.7%), and benthic crustaceans (11.0%). SCA identified diet variation among seasons (higher dissimilarity in Spring vs. Autumn), which is most likely related to the occurrence of intense coastal upwellings. Significant positive relationships between fish size and δ¹⁵N and δ¹³C values indicated an ontogenetic diet and potential habitat shift; broad isotopic niche area in small individuals (size class I: 115–169 mm) narrowed with increasing body size with the highest niche overlap occurring between size class II (170 to 243 mm) and class III (244 to 308 mm). Overall, the combined SCA and SIA approach determined that the Atlantic bigeye’s diet is closely connected to the pelagic food web. These data provide an improved understanding of ontogenetic and seasonal variation in Atlantic bigeye predator-prey interactions in the southwestern Atlantic.