Are hakes truly opportunistic feeders? A case of prey selection by the Argentine hake Merluccius hubbsi off southwestern Atlantic

BELLEGGIA, MAURO; ALVES, NADIA MARINA; LEYTON, MELISA MARIANA; ÁLVAREZ-COLOMBO, GUSTAVO; TEMPERONI, BRENDA; GIBERTO, DIEGO; BREMEC, CLAUDIA

FISHERIES RESEARCH

ELSEVIER SCIENCE BV

Año: 2019 vol. 214 p. 166 - 174

0165-7836

Prey selection and feeding strategy of the Argentine hake Merluccius hubbsi were investigated by analyzing thediet and prey availability in the main nursery area of the Patagonian stock (42.4°?46.4 °S, 70?102m depth).Stomach contents from fish captured using a bottom trawl net, and zooplankton samples collected with a Bongonet, were analyzed. Acoustic data were examined to identify pelagic aggregations and quantify relative preyabundance. The Argentine hake M. hubbsi fed mainly on crustaceans (92.7%IRI), followed by fish (7.1%IRI) andcephalopods (0.2%IRI). Among crustaceans, the diet was dominated by euphausiids (Euphausia spp.), the lobsterkrill Munida gregaria, and the hyperiid amphipod Themisto gaudichaudii. The most consumed fish was other hakeby cannibalism. Prey availability was also numerically dominated by the euphausiids (Euphausia spp.), followedby the hyperiid amphipod T. gaudichaudii and the lobster krill M. gregaria. Ontogenetic dietary changes weredetected: consumption of euphausiids and amphipods decreased with predator´s total length, and the consumptionof the lobster krill M. gregaria was higher in adult specimens. The Argentine hake M. hubbsi showedpositive prey selection for lobster krill M. gregaria. The consumption of Euphausiids decreased with the increasingacoustic abundance of the lobster krill M. gregaria. The cannibalism was denso-independent. TheArgentine hake appeared to be opportunistic when the proportion of prey eaten to the proportion present in theenvironment was compared, but deeper analyses confirmed that zooplankter with increased abundances andhigher energy density was the preferred prey.