MEPS 338:269-280 (2007)  -  doi:10.3354/meps338269

Blubber fatty acid profiles reveal regional, seasonal, age-class and sex differences in the diet of young Steller sea lions in Alaska

Carrie A. Beck1,2,*, Lorrie D. Rea1, Sara J. Iverson3, John M. Kennish2, Kenneth W. Pitcher1, Brian S. Fadely4

1Alaska Department of Fish & Game, Division of Wildlife Conservation/Marine Mammals, 525 W. 67th Avenue, Anchorage, Alaska 99518, USA
2University of Alaska Anchorage, Department of Chemistry, 3211 Providence Drive, Anchorage, Alaska 99508, USA
3Dalhousie University, Department of Biology, Halifax, Nova Scotia B3H 4J1, Canada
4National Marine Mammal Laboratory, NOAA Fisheries, Alaska Fisheries Science Center, 7600 Sand Point Way NE, Seattle, Washington 98115, USA

ABSTRACT: Blubber fatty acid (FA) profiles of young Steller sea lions Eumetopias jubatus (<24 mo old; n = 477) were investigated to determine whether regional, seasonal, age-class and sex differences occur in the diets of these demographic groups. Blubber FA profiles of spring (March to May) pups differed significantly by region, probably reflecting regional differences in the diet of adult females, who provide their pups with milk. While there were statistically significant seasonal and age-class differences in both Prince William Sound (PWS) and SE Alaska (SEA), differences in FA profiles between sexes were only evident in the blubber of yearlings from PWS. Within SEA, blubber FA profiles of summer pups differed significantly from all other seasonal/age-class groups in that region. This is consistent with movements of female–pup pairs from rookeries to haul-outs and hence differences in female foraging. In SEA, seasonal differences in blubber FA composition were evident and similar between yearlings and pups. In contrast, there was a gradual change in the FA profile of pup blubber from summer to spring in PWS, which did not follow the same seasonal pattern of yearling profiles. These differences in FA profiles suggest either differences in the timing of weaning between the 2 areas or shifts in the diets of lactating females, or both.


KEY WORDS: Fatty acids · Dietary intake · Eumetopias jubatus · Independent foraging


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