Diet of endangered Steller sea lions (Eumetopias jubatus) in the Aleutian Islands: new insights from DNA detections and bioenergetic reconstructions

Canadian Journal of Zoology, e-First Articles. The endangered western stock of Steller sea lion (Eumetopias jubatus (Schreber, 1776)) still declines in the western Aleutian Islands and accurate diet information is vital to test leading hypotheses. We undertook the first bioenergetic diet reconstruction using both molecular and hard part prey identifications from>600 scats collected in March –April 2008 and 2012. Atka mackerel (Pleurogrammus monopterygius (Pallas, 1810)) remained a primary prey (17%–27% by energy), but large (mean 60 cm) Pacific cod (Gadus macrocephalus Tilesius, 1810) also emerged as important prey (20%–24%) in a more diverse diet than previously reported, with C ottidae and smooth lumpsucker (Aptocyclus ventricosus (Pallas, 1769)) also contributing ∼10%. DNA detections highlighted a potentially important and previously underestimated prey, giant Pacific octopus (Enteroctopus dofleini (Wülker, 1910) (diet contribution 2%–15%, dependent on prey size assu mptions). Although 504 unique DNA identifications resulted in significant increases for cephalopods, Pacific cod, and smooth lumpsucker, hard part alone species rankings were similar to composite ones and bioenergetic species rankings similar to occurrence-based ones. Retention or regurgitation of l arge cephalopod beaks, the removal of large cod heads, and skeletal fragility of lumpsuckers may explain these differences. DNA identifications provide valuable comparative and complementary prey occu...
Source: Canadian Journal of Zoology - Category: Zoology Authors: Source Type: research