[MARMAM] Paper: New insights into the diets of harbor seals (Phoca vitulina) in the Salish Sea revealed by analysis of fatty acid signatures

Bromaghin, Jeffrey jbromaghin at usgs.gov
Wed Jan 2 09:54:29 PST 2013


Bromaghin, J. F., M. M. Lance, E. W. Elliot, S. J. Jeffries, A.
Acevedo-Gutiérrez, and J. M. Kennish. 2013. New insights into the diets of
harbor seals in the Salish Sea revealed by quantitative fatty acid
signature analysis. *Fishery Bulletin* 111:13-26.
doi:10.7755/FB.111.1.2

Abstract
Harbor seals (Phoca vitulina) are an abundant predator along the west coast
of North America, and there is considerable interest in their diet
composition, especially in regard to predation on valued fish stocks.
Available information on harbor seal diets, primarily derived from scat
analysis, suggests that adult salmon (Oncorhynchus spp.), Pacific Herring
(Clupea pallasii), and gadids predominate. Because diet assessments based
on scat analysis may be biased, we investigated diet composition
through quantitative analysis of fatty acid signatures. Blubber samples
from 49 harbor seals captured in western North America from
haul-outs within the area of the San Juan Islands and southern Strait of
Georgia in the Salish Sea were analyzed for fatty acid composition, along
with 269 fish and squid specimens representing 27 potential prey
classes. Diet estimates varied spatially,  demographically, and among
individual harbor seals. Findings confirmed the prevalence of previously
identified prey species in harbor seal diets, but other species also
contributed significantly. In particular, Black (Sebastes melanops) and
Yellowtail (S. flavidus) Rockfish were estimated to compose up to 50% of
some individual seal diets. Specialization and high predation rates on
Black and Yellowtail Rockfish by a subset of harbor seals may play a role
in the population dynamics of these regional rockfish stocks that is
greater than previously realized.

-----------------------------------------------
Jeffrey F. Bromaghin, PhD
Research Statistician
USGS Alaska Science Center
4210 University Drive
Anchorage, AK 99508
907-786-7086
jbromaghin at usgs.gov<https://mail.google.com/mail/?view=cm&fs=1&tf=1&to=jbromaghin@usgs.gov>
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