Salmonid passive integrated transponder tags and coded wire tags found in the forestomach of a harbor porpoise (Phocoena phocoena) in southwestern Washington

Abstract

Department of Biology Portland State University P.O. Box 751 Portland, Oregon 97207 Abstract—A dead adult harbor porpoise (Phocoena phocoena) was found on the Long Beach Peninsula in Washington on 22 August 2012. The harbor porpoise was skeletonized, with the forestomach being the only organ that remained. The forestomach contained 5 passive integrated transponder (PIT) tags and 91 coded wire tags (CWTs). The PIT tags were from juvenile Chinook salmon (Oncorhynchus tshawytscha) from 3 hatcheries in the Columbia River Basin. Of the 91 CWTs, 88 tags were identified as having come from juvenile Chinook salmon from Columbia River Basin hatcheries and 3 tags came from unidentified fish from hatcheries in Oregon. The 88 CWTs represent a number of hatcheries along the Columbia and Snake Rivers in Idaho, Washington, and Oregon. The tagged juveniles were released in the spring and summer of 2012. This report is the first one of Chinook salmon PIT tags and CWTs being recovered from a harbor porpoise in the Pacific Northwest, and it is one of few records of harbor porpoises eating salmon. The presence of these tags and the number of tags in the forestomach of a harbor porpoise indicate that juvenile Chinook salmon might be a more important component of the diet of harbor porpoises in the Pacific Northwest than previously thought.