State wildlife officials have begun killing California sea lions at Willamette Falls in an effort to save an imperiled run of salmon that’s in danger of extinction.

As of Thursday morning, four sea lions had been removed from the falls and euthanized at a second location, according to officials with the Oregon Department of Fish and Wildlife. The removals were authorized under a federal permit because sea lions are protected under the Marine Mammal Protection Act.

Sea lions have been removed from below Bonneville Dam previously under a similar permit.

For more than a decade, growing numbers of sea lions have been swimming more than 100 miles upstream from the mouth of the Columbia River to Bonneville Dam and Willamette Falls, where migrating salmon tend to congregate.

The result was a smorgasbord for the sea lions and a precarious situation for the fish, which have been declining in numbers for a variety of factors including the dams themselves and changes to salmon habitat.

Wildlife managers have tried a number of alternatives. Exclusion gates have been installed at the entrances to fish ladders at the falls. Sea lions have been hazed with firecracker shells fired from shotguns and underwater explosives. The animals have also been trapped and relocated, driven hundreds of miles and released into the ocean, only to return to the falls within days.

None of those efforts have proved effective at stemming the sea lions' predatory predilection for salmon.

“This is very specific behavior,” said Sheanna Steingass, marine mammal program lead for the state.

And the behavior was being learned, passed on from one sea lion to the next.

The permit allows for the removal of up to 93 California sea lions, Steingass said, but only if the animals have been observed for two or more days near the falls or have been seen actively preying on salmon. Steingass doesn’t expect that many animals to be killed, though. By May, when sea lions usually return to the open ocean, she said the agency was likely to kill no more than 40 or 50 sea lions.

The permitted kills are separate from legislation that was passed last year that would allow for the lethal removal of sea lions from the Columbia and Willamette rivers. Though that legislation passed, it still needs to go through a the full federal permitting process, including obtaining recommendations from a task force of experts and going through a period during which stakeholders can offer input.

The bill met some opposition from conservation groups as it moved through Congress, but was passed and signed into law in late 2017.

Travis Williams, executive director of Willamette Riverkeeper, still has issues with the practice of killing sea lions to save fish.

“It’s unfortunate that after decades of impacts from dams, habitat modifications and hatcheries, that it’s come down to euthanizing sea lions to save the relatively few steelhead we have left,” he said.

The theory behind the lethal removals, those animals that are removed won’t be able to pass on their predatory behavior on to other sea lions. Steingass said the hope was that, with the removal of the sea lions this year, far fewer animals would make the journey next year.

To kill the sea lions, wildlife biologists use the same traps that were unsuccessfully used in their relocation efforts. The animals are taken to a location offsite, anesthetized and euthanized using a combination of chemicals.

“As a pinniped biologist, it’s better for the salmon,” Steingass said, “but it’s better for the pinnipeds too because we won’t have hundreds of other animals learning this behavior.”

-- Kale Williams

kwilliams@oregonian.com

503-294-4048

@sfkale

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