Pinnipeds

Pinnipeds in the Columbia River include Pacific harbor seals, California sea lions, Steller sea lions and occasionally northern fur seals or elephant seals. During the spring and summer months, the population of seals and sea lions in the Columbia River Estuary and surrounding marine area may reach 5000 animals.  All of these species are protected by the Marine Mammal Protection Act. Migrating salmon normally comprise 10-30% of the diet of harbor seals and other pinnipeds.  However, fishery managers trying to increase the number of salmon that migrate upriver to spawn in the Columbia River basin have been working to reduce the percent of salmon eaten by seals.  The predation issue is highlighted by springtime sea lion congregations at Bonneville Dam, where observed consumption of adult steelhead, spring Chinook salmon, Pacific lamprey, and white sturgeon has rapidly increased over the last 5-6 years.  Managers have tried ‘hazing’ the sea lions with rubber bullets and using loud explosions and acoustic deterrents to drive them away from Bonneville Dam; they have also installed Sea Lion Exclusion Devices (SLEDS) to prevent sea lions from entering the dam fish ladders. FERL researchers have tested the effects of these pinniped management strategies on salmon:

·         Conducted a retrospective analysis of pinnipeds and their effects on anadromous salmonids migration success and survival at Bonneville Dam, 2005-2007;  

·         Tested the effects of sea bombs, popper shells, and firecrackers  on salmon in the areas of ‘hazing’;

·         Tested the effects of SLEDS on salmon entering the fish ladders of Bonneville Dam.

·         Evaluated stock-specific Chinook salmon predation estimates using run timing information and daily predation data.

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A sea lion in the Columbia River Estuary enjoys salmon for lunch.  Large numbers of protected seals and sea lions in the estuary are affecting migratory salmon as far upriver as Bonneville Dam. (Mpg: S. Lee)