Prevalence of Marine-Mammal Tooth and Claw Abrasions on Adult Anadromous Salmonids Returning to the Snake River

Abstract

During 1990, a relatively high percentage of adult anadromous salmonids returning to the Snake River had marine-mammal tooth and claw abrasions. From 1990 through 1993, annual incidence of these injuries ranged between 14.0 and 19.2% for spring–summer chinook salmon Oncorhynchus tshawytscha and between 5.4 and 14.2% for steelhead O. mykiss. Open wounds were observed on about one-third of the fish with abrasions. Although these results suggest that predation by pinnipeds may be an important mortality factor for Snake River spring–summer chinook salmon, further research is needed to accurately define the magnitude of the predation.