Food habits of the South american sea lion, Otaria flavescens, off Patagonia, Argentina

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

FISHERY BULLETIN

NATL MARINE FISHERIES SERVICE SCIENTIFIC PUBL OFFICE

Lugar: SEATLE; Año: 2000 vol. 98 p. 250 - 263

0090-0656

Food habits of the South American sea lion (Otaria fl avescens)off Patagonia were studied by means of stomach content analysis. The sampleswere collected during 1982?1987 and 1990?1998 in northern and centralPatagonia. The samples (n=59) came from individuals found dead on beachesand from animals recovered in incidental catches of the fi shery. Forty-one preyspecies (including fi shes, cephalopods, crustaceans, gastropods, polychetes,sponges, and tunicates) were identified; most important were Argentinehake (Merluccius hubbsi), red octopus (Enteroctopus megalocyathus), Argentineshortfi n squid (Illex argentinus),?raneya? (Raneya brasiliensis), Patagoniansquid (Loligo gahi), and Argentine anchovy (Engraulis anchoita). Differencesin diet were found between sexes but not between geographical area of sampling, period of sampling, or source of samples. Females fed mostly on benthicspecies, whereas males fed mostly on demersal-pelagic species. The differencein diet between sexes was associated with different feeding groundsor different home ranges and could be produced by different constraintsin the feeding behavior of each sex. These different constraints and restrictionscould lead females to feed in more coastal and shallower waters than thosewaters where males feed. Some of the important prey were commercial species(Argentine hake, Argentine shortfin squid, Patagonian squid) consumedat both commercial and noncommercial sizes by sea lions. The presenceof gastroliths was independent of the presence of stomach parasites; however,gastrolith weight was positively correlated with individual sea lion?slength, indicating that gastroliths could be involved in buoyancy control. In summary, these stomach content analyses indicate that South American sea lionsfeed primarily on demersal and benthic species and, in general terms, useresources according to their environmental availability.