Alimentación de Squalus acanthias y predación sobre Merluccius hubbsi en el Mar Argentino entre 34°47'-47°S.

Abstract

The spiny dogfish, Squalus acanthias is an euribatic, euritermic and cosmopolitan specie. In the Argentine Sea it consumes diversity of preys, characteristic of a generalist and oportunist feeder, butits principal food items are ctenophores, fishes and cephalopods.Diet overlap between sexes was found between 34°-37°S and 101-150 m,where males principally feed on fishes, squid and polichaetes,sharing only ctenophores and hake consumption with the females. Near 62 cm TL there is a shift in the diet, due to an increment of argentine hake Merluccius hubbsi and squid Illex argentinus predation and a diminution in ctenophores Pleurobrachia pileus eating. Feeding shows an increment from north to south, its mode on 42°-43°S.Argentine hake is an important prey between 34°-35°S and 100-150 m deep and southern to 42°S, less than 80 m deep. No feeding differences were found during daylight hours for Squalus acanthias is a continuous feeder. This species nearly overlaps it is distribution area with the one of argentine hake. Thereby, interespecific overlapand sharks predation pressure is almost permanent on juvenile andadult Merluccius hubbsi and it is higher southern to 44°S.Predation on 5-34 cm LT argentine hake occurs at 32-88 cm LT predator length, but the highest predation pressure is focalized on those smaller than 25 cm. There is a partial diet overlap between Squalus acanthias and Merluccius hubbsi. This fact does not implie competence, for each species does not overlap principal food items.