Diet of dusky dolphins, Lagenorhynchus obscurus, in waters of Patagonia, Argentina

KOEN-ALONSO MARIANO; CRESPO ENRIQUE ALBERTO; GARCÍA NÉSTOR ANÍBAL; PEDRAZA SUSANA NOEMI; COSCARELLA, MARIANO ALBERTO

FISHERY BULLETIN

NATL MARINE FISHERIES SERVICE SCIENTIFIC PUBL OFFICE

Lugar: SEATLE; Año: 1998 vol. 96 p. 366 - 374

0090-0656

The dusky dolphin, Lagenorhynchus obscurus, is probably the best known species of the genus Lagenorhynchus in the Southern Hemisphere. It is common in temperate waters of New Zealand, South Africa, Peru, northern Chile, and Argentina (Crespo, 1991; Van Waerebeek, 1992; Crespo et al., in press). Incidental catches have been recorded in coastal and offshore fisheries of A:rgentina (Corcuera et al., 1994; Crespo et al., 1994a, 1994b; Dans et al., in press), whereas directed captures have occurred offPeru (Read et al., 1988; Van Waerebeek and Reyes, 1990; Reyes, 1992). The biology of dusky dolphins has been studied in Argentina since the 1970's (Würsig and Würsig, 1980; Würsig and Bastida, 1986; Dans et al., 1993). A detailed behavioral study was carried out at Península Valdés (Würsig and Würsig, 1980), and preliminary information about the reproductive biology of females was obtained by Dans et al (1993, 1997). Feeding habits have been briefly described for dusky dolphins from New Zealand (Gaskin, 1972), Patagonia (Dans et al., 1993; Crespo et al., 1994c), and Antarctic and subAntarctic waters (Goodall and Galeazzi, 1985). In Patagonia, the behavior of dusky dolphins feeding on Argentine anchovy, Engraulis anchoita, schools has been described by Würsig and Würsig (1980). A more recent and detailed study of their feeding habits by stomach content analysis was carried out in coastal waters of central Peru (McKinnon, 1994). The Peruvian sample consisted of animals caught mostly in gill nets (McKinnon, 1994). Peruvian anchoveta, Engraulis ringens, was the most important prey species for Peruvian dusky dolphins, accounting for 92.5% in number and 83.8% in weight of the total sample, and97.8% frequency of occurrence (McKinnon, 1994). Differences in diet between lactating and onlactating mature females were not found, and the anchoveta was almost the exclusive prey species inboth sexes (McKinnon, 1994). The objective of the present study is to describe the diet of the dusky dolphin in Patagonia in terms of both species composition and prey size. Seasonal and annual composition were not investigated because the sample size was small when subdivided along these lines