Frequency of Pinniped-Caused Scars and Wounds on Adult Spring–Summer Chinook and Sockeye Salmon Returning to the Columbia River
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At Bonneville Dam (Columbia River, 235 km from the mouth), the percentage of anadromous adult Pacific salmon Oncorhynchus spp. with abrasions (scars or wounds) caused by pinnipeds has increased from 2.8% in 1991 to 25.9% in 1996 for sockeye salmon O. nerka and from 10.5% in 1991 to as much as 31.8% in 1994 for spring–summer chinook salmon O. tshawytscha. Although there was a large increase in the percentage of salmonids with pinniped-caused abrasions between 1991 and 1996, fewer than 3% of the fish were judged to have abrasions sufficiently severe to adversely affect their survival to spawning. Larger, earlier-migrating chinook salmon were more likely to have abrasions than smaller, later-migrating fish. Similar trends were not found for sockeye salmon. Although these results suggest that pinniped predation may be an increasingly serious problem for Columbia basin salmonids, a lack of data that relates abrasions to pinniped-caused mortality makes it impossible to accurately estimate the magnitude of pinniped-caused mortality.
Fryer, J.K. 1998. Frequency of pinniped-caused scars and wounds on adult spring–summer Chinook and Sockeye Salmon returning to the Columbia River. North American Journal of Fisheries Management 18(1):46-51. Online at https://doi.org/10.1577/1548-8675(1998)018<0046:FOPCSA>2.0.CO;2.
Mar 1st, 1998