The Oregon Department of Fish and Wildlife says the Willamette River is having its best wild winter steelhead return in three years, thanks in part to the lethal removal of California sea lions.
So far this year, more than 2,700 steelhead have passed Willamette Falls, and the season isn't over yet. The agency projects that about 3,200 winter steelhead will make it over the falls by the end of May, when their spawning migration typically ends. That's nearly double last year's return of 1,829 fish and almost four times as many as the record low return of 822 fish in 2017. State officials determined that wild steelhead had a 90 percent chance of going extinct without intervention.
California sea lions--which congregate at the base of the falls to pick off steelhead through late winter and Chinook through the spring--were consuming an estimated 25 percent of the steelhead return and 9 percent of the Chinook, Oregon biologists found.
Last November, the National Marine Fisheries Service gave Oregon authorization to trap and kill California sea lions at the falls, and since mid-December, the agency has euthanized 13 of the wandering males. Authorization came after efforts to relocate or scare them away were unsuccessful.
Many of the euthanized sea lions had been coming to the falls for years, and some had been hanging around since last August. By March 13--after 11 sea lions were trapped and killed--there were no sea lions on the lower river for six days, Oregon Department of Fish and Wildlife said in a news release. The timing corresponded with a warm spell, and hundreds of steelhead made their way through the lower river and over the falls without encountering a sea lion.
But the battle to protect Willamette River steelhead, and now spring Chinook, is far from over.
"We typically see an increase in sea lion abundance at the Falls in April as additional animals move in to feed on the more abundant spring Chinook," Shaun Clements, ODFW's senior policy analyst, said in the release.
Biologists say it will take at least two or three years to fully manage sea lion predation at Willamette Falls, but without these males returning home with reports of a successful hunt, officials believe the problem should taper off.