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

Food habits of the South American sea lion (Otaria flavescens) off Patagoni a were studied by means of stomach content analysis. The samples were colle cted 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 fishery. Forty-one prey species (in cluding fishes, cephalopods, crustaceans, gastropods, polychetes, sponges, and tunicates) were identified; most important were Argentine hake (Merlucc ius hubbsi), red octopus (Enteroctopus megalocyathus), Argentine shortfin s quid (Illex argentinus), "raneya" (Raneya brasiliensis), Patagonian squid ( Loligo gahi), and Argentine anchovy (Engraulis anchoita). Differences in di et were found between sexes but not between geographical area of sampling, period of sampling, or source of samples. Females fed mostly on benthic spe cies, whereas males fed mostly on demersal-pelagic species. The difference in diet between sexes was associated with different feeding grounds or diff erent home ranges and could be produced by different constraints in the fee ding behavior of each sex. These different constraints and restrictions cou ld lead females to feed in more coastal and shallower waters than those wat ers where males feed. Some of the important prey were commercial species (A rgentine hake, Argentine short-fin squid, Patagonian squid) consumed at bot h commercial and noncommercial sizes by sea lions. The presence of gastroli ths was independent of the presence of stomach parasites; however, gastroli th weight was positively correlated with individual sea lion's length, indi cating 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 resour ces according to their environmental availability.