Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 516
Title: Winter observations of southern resident killer whales (Orcinus orca) near the Columbia River plume during the 2005 spring Chinook salmon (Oncorhynchus tshawytscha) spawning migration
Author: J. E. Zamon, T. J. Guy, K. Balcomb, D. Ellifrit
Publication Year: 2007
Journal: Northwestern Naturalist
Volume: 88
Pages: 193-198
Keywords: Southern resident killer whale, Chinook salmon, Columbia River, Orcinus orca, Oncorhynchus tshawytscha, plume front

IIn the northeastern Pacific Ocean the North American population of southern resident Killer Whales (Orcinus orca, hereafter ‘‘SRKW’’) was listed as ‘‘Endangered’’ by the United States government effective 16 February 2006. There is significant scientific interest in filling data gaps regarding SRKW habitat use and ecology from November to April because few data are available about the winter distribution and feeding behavior of SRKW. From May to October, these whales occur primarily in US and Canadian waters of Juan de Fuca Strait, the Canadian Gulf Islands, the US San Juan Islands, and Georgia Strait, where their diet appears to be dominated by adult Chinook Salmon (Oncorhynchus tshawytscha). After October, the southern residents expand their range to include Puget Sound as well as the outer coast of Vancouver Island, Washington, Oregon, and California. Between 1975 and 2004, there have been only 17 confirmed sightings of SRKW between November to April, and 12 of those winter sightings were from the outer coast. To our knowledge, this is the first published report that describes SRKW behavior at the mouth of the Columbia River and also positively identifies individual SRKW associated with that behavior. We report confirmed sightings of at least 13 photo-identified SRKW individuals from L-pod, the largest of the 3 pods in the southern resident population.

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