Spatio-temporal and ontogenetic changes in the diet of the Argentine hakeMerluccius hubbsi

Abstract

The diet and the trophic level of the Argentine hakeMerluccius hubbsiwas investigated in the south-west Atlantic Ocean. Stomachs from 3405 specimens, ranging from 10 to 94 cm total length, collected on three research cruises carried out during winter 2011 and summer 2012, were examined at the laboratory. Dietary shifts related to sex, maturity stage, size, age, season, region and hour were examined using generalized linear models. The Argentine hakeM. hubbsifed mainly on zooplankton crustaceans (Themisto gaudichaudii, Euphausia lucensandMunidaspp.), followed by fish and cephalopods. During summer, cephalopods (mainlyIllex argentinus) were the main prey ofM. hubbsi, indicating spatio-temporal changes in the diet. This work also revealed ontogenetic dietary changes associated with size, from zooplankton crustaceans during early life stages (E. lucens, T. gaudichaudiiandMunidaspp.) to fish and cephalopods. The trophic level ofM. hubbsiranged from 3.43 to 4.51 according to season and region. Cannibalism increased with predator length and contributed a maximum of 8.14% to the diet ofM. hubbsiduring winter on the inner Patagonian continental shelf.