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

Abstract

Food habits of the South American sea lion (Otaria flavescens) off Patagonia were studied by means of stomach content analysis. The samples were collected during 1982–1987 and 1990–1998 in northern and central Patagonia. The samples (n=59) came from individuals found dead on beaches and from animals recovered in incidental catches of the fi shery. Forty-one prey species (including fishes, cephalopods, crustaceans, gastropods, polychetes, sponges, and tunicates) were identified; most important were Argentine hake (Merluccius hubbsi), red octopus (Enteroctopus megalocyathus), Argentine shortfi n squid (Illex argentinus), “raneya” (Raneya brasiliensis), Patagonian squid (Loligo gahi), and Argentine anchovy (Engraulis anchoita). Differences in diet were found between sexes but not between geographical area of sampling, period of sampling, or source of samples. Females fed mostly on ben-thic species, whereas males fed mostly on demersal-pelagic species. The difference in diet between sexes was associated with different feeding grounds or different home ranges and could be produced by different constraints in the feeding behavior of each sex. These different constraints and restrictions could lead females to feed in more coastal and shallower waters than those waters where males feed. Some of the important prey were commercial species (Argentine hake, Argentine shortfin squid, Patagonian squid) consumed at both commercial and noncommercial sizes by sea lions. The presence of gastroliths was independent of the presence of stomach parasites; however, gastrolith weight was positively correlated with individual sea lion’s length, indicating that gastroliths could be involved in buoyancy control. In summary, these stomach content analyses indicate that South American sea lions feed primarily on demersal and benthic species and, in general terms, use resources according to their environmental availability.