MEPS 384:287-302 (2009)  -  doi:10.3354/meps08000

Sources of variation in diets of harp and hooded seals estimated from quantitative fatty acid signature analysis (QFASA)

Strahan Tucker1,5,*, W. Don Bowen2, Sara J. Iverson1, Wade Blanchard3, Garry B. Stenson4

1Department of Biology, Dalhousie University, 355 Oxford Street, Halifax, Nova Scotia B3H 4J1, Canada
2Population Ecology Division, Bedford Institute of Oceanography, Department of Fisheries and Oceans, 1 Challenger Drive, Dartmouth, Nova Scotia B2Y 4A2, Canada
3Department of Mathematics and Statistics, Dalhousie University, 355 Oxford Street, Halifax, Nova Scotia B3H 4J1, Canada
4Northwest Atlantic Fisheries Centre, Department of Fisheries and Oceans, PO Box 5667, St John’s, Newfoundland A1C 5X1, Canada
5Present address: Pacific Biological Station, Department of Fisheries and Oceans, 3190 Hammond Bay Road, Nanaimo, British Columbia V9T 6N7, Canada

ABSTRACT: Inter-specific competition for prey is thought to influence the structure of ecological communities and species niche breadth. Harp seals Pagophilus groenlandicus and hooded seals Cystophora cristata are geographically overlapping and highly migratory predators in the North Atlantic ocean. Hooded seals are known to dive deeper and longer than harp seals and are more closely associated with the continental shelf edge and deep ocean. Quantitative fatty acid (FA) signature analysis (QFASA) was recently developed to estimate the species composition of diets by statistically comparing FA signatures of predator adipose tissue with that of potential prey. Using QFASA, we estimated diets for harp (adults, n = 294; juveniles, n = 232) and hooded (adults, n = 115; juveniles, n = 38) seals from the pre- and post-breeding periods between 1994 and 2004. We found evidence of inter- and intra-specific variation in diets, diet quality and breadth, reflecting different foraging tactics. Harp seal diets were comprised predominantly of amphipods, Arctic cod, capelin, herring, sand lance and redfish. Hooded seal diets were composed primarily of amphipods, Atlantic argentine, capelin, euphausiids and redfish. Relative to the other species, harp seals consumed twice the proportion of amphipods, while hooded seals consumed 3 times the proportion of redfish; percentages of capelin were similar. QFASA provided new evidence of the importance of amphipods in the diets of both species and of the pronounced differences in the proportions of pelagic forage fish between demographic groups.


KEY WORDS: Harp seal · Pagophilus groenlandicus · Hooded seal · Cystophora cristata · Diet segregation · Quantitative fatty acid signature analysis · QFASA


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Cite this article as: Tucker S, Bowen WD, Iverson SJ, Blanchard W, Stenson GB (2009) Sources of variation in diets of harp and hooded seals estimated from quantitative fatty acid signature analysis (QFASA). Mar Ecol Prog Ser 384:287-302

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