Comparing total body lipid content of young-of-the-year Steller sea lions among regions of contrasting population trends

Steller sea lion (Eumetopias jubatus) young-of-the-year (YOY) are nutritionally dependent upon their dam through the majority of their first year. Several indices of body condition were measured in YOY 1.5-9 mo of age captured in Southeast Alaska (n = 122), the Gulf of Alaska (n = 182), and the Aleutian Islands (n = 38) to test the hypothesis that nutritional stress impacted the ability of adult female Steller sea lions to adequately nourish their late gestation YOY in the central Aleutian Islands in the early 2000s. Body mass (kg) and percent total body lipid content (% TBL) increased with age in all three regions of Alaska that were sampled (P < 0.05). Young-of-the-year 7-9 mo of age were leaner in Southeast Alaska (27.6% +/- 1.0%) and Gulf of Alaska (29.5% +/- 0.8%) than in the Aleutian Islands (35.7% +/- 1.2%, P < 0.001). Condition indices calculated from morphometric measures did not strongly predict the %TBL measured by isotope dilution. The trend for Aleutian Island YOY to have larger body mass and larger body fat reserves are counter to what would be expected if dams were unable to adequately provision their late lactation YOY due to inadequate food availability in the central Aleutian Islands.