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 (δ13C and δ15N) and stomach content analyses, from specimens captured during eight scientific trawl surveys carried out 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 on fish and crustaceans. Among fishes, the most important were the notothenioid Patagonotothen ramsayi and the Argentine hake Merluccius hubbsi. The most important crustaceans consumed were the lobster krill Munida gregaria, isopods (Cirolana spp., Serolidae), stomatopods (Pterygosquilla armata) and gammarid amphipods. Ontogenetic diet shifts were detected with the TL, with an increase consumption of fish and a decrease consumption of crustaceans. Moreover, there were changes in the diet associated with depth and region. The isotopic structure of the food chain showed the classic enrichment with trophic level increase. While the stomach contents analysis in a subregion indicated that crustaceans were the predominant prey, followed by cephalopods and fish, Bayesian mixing models showed differential assimilation to pink cusk-eel muscle, with fish as the main assimilated prey and a relatively minimal inputs of crustaceans and cephalopods. Clear distinctions between the pelagic and benthic baselines were detected, with pink cusk-eel participating in both benthic and pelagic pathways. The pink cusk-eel occupied the role of top predator in the Southwestern Atlantic ecosystem (trophic level ∼4) and the δ15N did not exhibit changes with respect to an analyzed specimen of the year 1962.