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 Argentinehake Merluccius hubbsi wereinvestigated by analyzing the diet and prey availability in the main nurseryarea of the Patagonian stock (42.4°-46.4°S, 70-102m depth). Stomach contents fromfish captured using a bottom trawl net, and zooplankton samples collected witha Bongo net, were examined. Acoustic data were analyzed to identify pelagicaggregations and quantify relative prey abundance. The Argentine hake M. hubbsi fed mainly on crustaceans(92.7 %IRI), followed by fish (7.1 %IRI) and cephalopods (0.2 %IRI). Amongcrustaceans, the diet was dominated by euphausiids (Euphausia spp.), the lobster krill Munida gregaria, and the hyperiid amphipod Themisto gaudichaudii. The most consumed fish was other hake bycannibalism. Prey availability was also numerically dominated by the euphausiids(Euphausia spp.), followed by thehyperiid amphipod T. gaudichaudii andthe lobster krill M. gregaria. Ontogeneticdietary changes were detected: consumptionof euphausiids and amphipods decreasedwith predator´s total length, and the consumption of the lobster krill M. gregaria was higher in adultspecimens. The Argentine hake M. hubbsishowed positive prey selection for lobster krill M. gregaria. Theconsumption of Euphausiids decreased with the increasing acoustic abundance ofthe lobster krill M. gregaria. Thecannibalism was denso-independent. The Argentine hake appeared to be opportunistic when the proportion ofprey eaten to the proportion present in the environment was compared, but deeperanalyses confirmed that zooplankter with increased abundances and higher energydensity was the preferred prey.