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Date Permissions Signed


Date of Award

Summer 2022

Document Type

Masters Thesis

Department or Program Affiliation


Degree Name

Master of Science (MS)



First Advisor

Acevedo-Gutiérrez, Alejandro, 1964-

Second Advisor

Schwarz, Dietmar, 1974-

Third Advisor

Akmajian, Adrianne M. (Adrianne Monet)


Understanding generalist predator impact on prey populations requires an understanding of predator diet composition, foraging ecology and specialization, all of which may vary over spatial and temporal scales. Steller sea lions (Eumetopias jubatus) are large, sexually dimorphic, generalist predators that may have different roles in the ecosystem based on sex. However, the variation between individuals within a population, or intrapopulation feeding diversity of Steller sea lions has not been examined. In this study, I describe the diet of Steller sea lions along the northern coast of Washington between December 2020-August 2021 using DNA metabarcoding, hard parts analysis, and qPCR sex determination to examine diet composition and factors influencing intrapopulation feeding diversity. I found that the diet composition of Steller sea lions along the northwest Washington coast from December 2020-August 2021 was mainly comprised of American shad (Alosa sapidissima), Pacific herring (Clupea pallasii), big skate (Raja binoculata), walleye pollock (Gadus chalcogrammus) and starry flounder (Platichthys stellatus). I found that intrapopulation feeding diversity, a proxy for individual specialization, is not influenced by season and sex. Further, individuals that exhibited generalist foraging techniques correlated with pelagic prey items such as American shad, Pacific herring, and Pacific salmon (Oncorhynchus spp.), which suggest that Steller sea lions in this region generally exhibit pelagic foraging techniques resulting in consumption of species of conservation concern.




foraging ecology, diet studies, fisheries, conservation biology


Western Washington University

OCLC Number


Subject – LCSH

Steller's sea lion--Food--Northwest, Pacific; Pelagic fishes--Predators of--Ecology--Northwest, Pacific

Geographic Coverage

Northwest, Pacific




masters theses




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