W hen the Oregon Department of Fish & Wildlife (ODFW) modeled “Extinction Risk” of winter steelhead in the Willamette River in 2017, it was a whopping 90%. Following the removal of just 33 California sea lions preying on steelhead at Willamette Falls, ODFW estimates that the year-end extinction risk will fall to between 10-15%.
Before the permitted removal began, about 25% of the steelhead population was consumed by sea lions. Predation on winter steelhead dropped to 9% this year. Just 512 winter steelhead spawned above Willamette Falls in 2017, rising to 3,118 in 2018.
Executive Director of Northwest Steelheaders Chris Hager is encouraged by the success of the permit. “Considering the incredible results of this place-based, individually-targeted program, we are confident that a similar approach in the Columbia River Basin will be effective in increasing winter steelhead runs,” Hager said. “This solution minimizes the number of sea lions euthanized while maximizing the steelhead population. It’s a win-win.”
The 33 sea lions legally taken by officials compose only 0.01% of the California sea lion population, totaling 296,000. The NOAA Fisheries permit authorization of November 2018 allows for the euthanization of up to 93 sea lions per year on the lower Willamette River, a number that officials are not likely to take.
According to ODFW Policy Advisor Shaun Clements, new sea lions tend not to take the place of those removed. Pinniped experts at ODFW found that the individual sea lions preying on steelhead in the Willamette River traveled 128 miles from the ocean to reach the falls each year and hypothesized that the journey was a learned behavior. Officials removed 99% of the habitual visitors in early 2019 and no sea lions have returned to the falls since August, suggesting the hypothesis was correct.