Steller sea lion diet in the Eastern Kamchatka

Abstract

We studied the diet of Steller sea lion (Eumetopias jubatus) on the eastern coast of Kamchatka based on the remains of undigested food parts found in feces at terrestrial sites near Cape Kozlova (rookery) and Cape Kekurny (haulout) in the summer. A total of 276 fecal samples were analyzed from 2004 to 2008. Forty eight food items of 17 fish families and one family of cephalopod mollusks were identified. Steller sea lion diet was diverse yet dominated by only several species. The pollock Gadus chalcogrammus, Atka mackerel Pleurogrammus monopterygius, Pacific sand lance Ammodytes hexapterus and Hemilepidotus sp. were dominant by frequency of occurrence in decreasing order at both sites. Differences were found in the Steller sea lion diet in the studied sites. Prey diversity at Kekurny Cape within scat samples ranged from one to twelve objects within the median of four prey item per a sample. The median of prey diversity at Kozlov Cape within scat samples was two food objects within a range of one to nine prey types per sample. Of the 37 scats (24,5 %) collected at Kozlov Cape that contained a single prey item, 75,7% contained Atka mackerel. Among scats collected at Kekurny Cape that contained a single prey species (n=10, 8,0 %), 50,0 % contained Atka mackerel and 40,0 % pollock. In contrast to the high diet diversity at Kekurny Cape haulout, breeding Steller sea lions at Kozlova Cape rookery fed on a narrow set of prey items. Interannual changes in the diet structure at each site were not statistically significant.