At the Bonnerville Dam, on the Colombia River between Oregon and Washington, smart sea lions are creating a conservation nightmare as they eat up threatened Chinook salmon and steelhead.
Hundreds of California sea lions and increasingly the much larger Steller sea lions prey on the fish, returning to spawn in the same place they were born, at congested fish ladders by the dam. Conservationists estimate that up to a fifth of the returning salmon are being lost. They fear a repeat of the decimation of steelhead at Ballard Locks in Seattle in 1994; that run is now extinct.
California sea lions have learned to swim up to 145 miles upriver to the fish ladders. They have recently been joined by Steller sea lions, who take five times as many fish.
Trying to stop them are a small group of officers from the Columbia River Inter-Tribal Fish Commission (CRITFC). They use non-lethal hazing methods, but in March the National Oceanic and Atmospheric Administration National Marine Fisheries Service granted lethal rights to remove 92 California sea lions deemed “problematic.” After a legal case by the Humane Society, that number was dropped to 30.
Under the Marine Mammal Protection Act, California sea lion numbers have tripled, but the similarly protected salmon are in trouble.
CRITFC senior fish scientist Doug Hatch says that the removal program is necessary and that the increasing numbers of Steller sea lions point to a looming catastrophe. He says:
Salmon not only supply protein to people and animals such as bears and eggs. They also transport marine derived nutrients to the inland forests and aquatic ecosystem.
We just want to give the salmon to have to pass through a gauntlet of sea lions a chance to get to the eight fish ladder entrances at Bonneville Dam.
Picture by ZaNia