Birds, fish, and marine mammal predation are a major cause of mortality for ESA-listed juvenile and adult fish in the Columbia River Basin.
Populations of Caspian terns and double-crested cormorants have increased over the past two decades in the Columbia River estuary and in the mid-Columbia region. Northern pikeminnow and bass also prey on juvenile salmon and steelhead.
California sea lions and stellar sea lions consume substantial numbers of adult spring Chinook salmon, sturgeon and winter steelhead below Bonneville Dam.
Federal and state agencies are cooperating to reduce predation. Programs to redistribute Caspian terns, deter and block sea lions from fish ladders, and reduce the northern pikeminnow population through sport angling have been successful in decreasing the loss of adult and juvenile salmon to predation.
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