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

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

FISHERY BULLETIN

NMFS Scientific Publications Office (SPO)

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

0090-0656

Feeding habits of dusky dolphins of Patagonia were studied analyzing their stomach contents. The sample was obtained mostly from incidental catches made by the shrimp trawling fishery operating in the area. Dolphin catches were located between 42ºS and 46º30´S from 1989 to 1994. Twenty five stomach contents were analyzed and eight prey species were identified. The fish prey species were the southern anchovy Engraulis anchoita, the hake Merluccius hubbsi, the "pampanito" Stromateus brasiliensis and the southern cod Nothotenia sp. The cephalopod prey species identified were the shortfin squid Illex argentinus, the patagonian squid Loligo gahi, the sepiolid Semirossia tenera and the octopus Octopus tehuelchus. The most important prey was the southern anchovy. It comprised the 41% of the total regression-estimated ingested biomass and the 39% of the total number of preys. The prey species following in order of importance were both squid species. Most of preys had sizes below 20cm of length and corresponded to immature individuals. However, southern anchovy was eaten on pre-adults and adults sizes and hake was consumed by dolphins on immature and mature sizes. The relative importance of anchovies in the diet of dusky dolphins of Patagonia was lower than its importance in the Peruvian population. Most of the preys were pelagic species or pelagic early stages of benthic or demersal species.