Prey contribution to the diet of pink cusk-eel Genypterus blacodes (Forster, 1801) revealed by stomach content and stable isotopic analyses in the southwestern Atlantic

Abstract

This paper studied the diet of the pink cusk-eel Genypterus blacodes, using a combination of stable isotope (δ13Cand δ15N) and stomach content analyses, from specimens captured during eight scientific trawl surveys carriedout from 37◦S to 53.3◦S, and from 65 to 390 m depth. A total of 1615 specimens were analyzed, from which 795(49.22 %) that ranged from 15 to 114 cm in total length (TL), contained prey. The pink cusk-eel fed mainly onfish and crustaceans. Among fishes, the most important were the notothenioid Patagonotothen ramsayi and theArgentine hake Merluccius hubbsi. The most important crustaceans consumed were the lobster krill Munida gregaria,isopods (Cirolana spp., Serolidae), stomatopods (Pterygosquilla armata) and gammarid amphipods. Ontogeneticdiet shifts were detected with the TL, with an increase consumption of fish and a decrease consumption ofcrustaceans. Moreover, there were changes in the diet associated with depth and region. The isotopic structure ofthe food chain showed the classic enrichment with trophic level increase. While the stomach contents analysis ina subregion indicated that crustaceans were the predominant prey, followed by cephalopods and fish, Bayesianmixing models showed differential assimilation to pink cusk-eel muscle, with fish as the main assimilated preyand a relatively minimal inputs of crustaceans and cephalopods. Clear distinctions between the pelagic andbenthic baselines were detected, with pink cusk-eel participating in both benthic and pelagic pathways. The pinkcusk-eel occupied the role of top predator in the Southwestern Atlantic ecosystem (trophic level ~4) and the δ15Ndid not exhibit changes with respect to an analyzed specimen of the year 1962.