Food habits of Dipturus chilensis (Pisces: Rajidae) off Patagonia, Argentina

The food habits of the beaked skate were studied utilising 274 individuals obtained from the incidental catches of the Argentine hake (Merluccius hubbsi) fishery. The most important prey were the Argentine hake, the southern cod (Patagonotothen ramsayi), the Argentine shortfin squid (Illex argentinus). the isopod (Serolis schythei). the "raneya" (Raneya brasiliensis. Pisces: Ophidiidae), and the Argentine anchovy (Engraulis anchoita). A total of 45 prey species was identified, No differences in the diet between sexes, but significant differences among size classes and between immature and mature individuals were found, Two size-related dietary shifts previously reported in this species. at around 35 cm and 85 cm total length were confirmed and related to changes in habitat utilisation. The first shift entails a major change from benthic prey (mostly crustaceans) to demersal-benthic prey (mostly fishes) and the second change from demersal-benthic to demersal-pelagic prey (increased consumption of Argentine hake and decreased consumption of southern cod). The second shift coincides with sexual maturation and may reflect a behavioural response to maturation. (C) 2001 International Council for the Exploration of the Sea.