Salmon consumption by Kodiak brown bears (Ursus arctos middendorffi) with ecosystem management implications

Authors: Van Daele, M.B.1; Robbins, C.T.2; Semmens, B.X.3; Ward, E.J.3; Van Daele, L.J.4; Leacock, W.B.5

Source: Canadian Journal of Zoology, Volume 91, Number 3, 01 2013 , pp. 164-174(11)

Publisher: NRC Research Press

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Abstract:

The ecological role of large predators in North America continues to spark heated public debate. Although brown bears (Ursus arctos L., 1758) and the salmon (genus Oncorhynchus Suckley, 1861) they feed on have declined in many areas, the Kodiak archipelago is famous for large brown bears and abundant salmon. Salmon have generally been managed for maximum sustained yield in a fisheries sense, but those levels may be well below what is necessary for maximum ecosystem productivity. Consequently, we used stable isotopes and mercury accumulated in hair to estimate intake of salmon by Kodiak brown bears (Ursus arctos middendorffi Merriam, 1896). Salmon intake increased from subadult males (592 ± 325 kg·bear−1·year−1) to adult males (2788 ± 1929 kg·bear−1·year−1) and from subadult females (566 ± 360 kg·bear−1·year−1) to adult females (1364 ± 1261 kg·bear−1·year−1). Intake within each group increased 62% ± 23% as salmon escapement increased from ∼1 500 to ∼14 000 kg·bear−1·year−1. The estimated population of 2300 subadult and adult bears consumed 3.77 ± 0.16 million kg of salmon annually, a mass equal to ∼6% of the combined escapement and commercial harvest (57.6 million kg). Although bears consume a small portion of the total mass of adult salmon, perpetuation of dense populations of large bears requires ecosystem-based management of the meat resources and environments that produce such bears.

Keywords: Kodiak brown bear; Ursus arctos; assimilated diet; isotopes stables; mercure; mercury; nourriture assimilée; ours kodiak; salmon; saumon; stable isotopes

Document Type: Research Article

DOI: http://dx.doi.org/10.1139/cjz-2012-0221

Affiliations: 1: School of Biological Sciences, Washington State University, Pullman, WA 99164-4236, USA. 2: School of the Environment and School of Biological Sciences, Washington State University, Pullman, WA 99164-4236, USA. 3: National Marine Fisheries Service, Northwest Fisheries Science Center, 2725 Montlake Boulevard East, Seattle, WA 98112, USA. 4: Alaska Department of Fish and Game, 211 Mission Road, Kodiak, AK 99615, USA. 5: Kodiak National Wildlife Refuge, 1390 Buskin River Road, Kodiak, AK 99615, USA.

Publication date: January 1, 2013

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