Sea lion with a sturgeon at Bonneville Dam. Washington Department of Fish and Wildlife Photo.
The Council this month approved a request from the Washington Department of Fish and Wildlife for the Bonneville Power Administration to fund the construction of a floating platform big enough to handle Steller sea lions, which can weigh more than a ton, that may be captured after preying on salmon, steelhead, and sturgeon in the tailrace of Bonneville Dam. With the Council’s approval, and if Bonneville agrees, the platform could be built and operational by this fall.
Under the Endangered Salmon Predation Prevention Act, signed into law by President Donald Trump in December 2018, the Washington, Oregon, and Idaho fish and wildlife departments, and the Columbia River Inter-Tribal Fish Commission, are given expanded authority to remove a limited number of the most aggressive sea lions that have been observed killing fish in the Columbia River and its tributaries downstream of McNary Dam. Before the law was enacted last month, only California sea lions could be removed, and only at Bonneville Dam. With federal authorization, Oregon’s fish and wildlife department already has removed several sea lions from the Willamette River below Willamette Falls, where they have decimated wild Willamette Winter Steelhead, a threatened species.
Every year since 2002, the U.S. Army Corps of Engineers has observed sea lions, both Californias and Stellers, killing salmon, steelhead, sturgeon, and lamprey in the area immediately downstream of Bonneville Dam. Some have taken up near-permanent residence, and this includes at Willamette Falls. In a letter to the Council requesting money for the dock, which would come from cost savings in other projects that implement the Council’s Columbia River Basin Fish and Wildlife Program, Kessina Lee, Southwest Washington Director for the Washington Department of Fish and Wildlife, wrote that predation by Steller sea lions is increasing. “In 2017 Steller sea lions consumed more salmon/steelhead than California sea lions did for the first time,” she wrote.
The new law slightly increased the numbers of problem sea lions that could be removed, added the area below Willamette Falls and other lower Columbia tributaries where sea lions might be present, and did not preclude the removal of Steller sea lions. The Stellers used to prey primarily on sturgeon below Bonneville Dam, but in recent years about 100 have taken up permanent residence at the dam and have increased their kill of salmon and steelhead. Today Stellers are responsible for three-quarters of the total predation on salmon, steelhead, and sturgeon at the dam, Lee told the Council.
A sea lion trap at Bonneville Dam tips under the weight of a Steller sea lion. Washington Department of Fish and Wildlife photo.
Lee said that the floating platform the agencies now use for capturing California sea lions, which can handle animals up to about 700 pounds, might handle small Stellers, but full-grown adults can be 11 feet long and weigh over a ton, and the dock is not built for that much weight. The cost of the new platform is estimated to be about $50,000.
The effort to reduce predation by sea lions is a collaboration of the Idaho, Oregon, and Washington fish and wildlife departments and the Columbia River Inter-Tribal Fish Commission, a point Washington Council Member Guy Norman, chair of the Council’s Fish and Wildlife Committee, noted.
“There has been so much effort on this problem over the last 10 years, by the Council the states, tribes – really, the entire region,” Norman said. “This is the next step; the impact these marine mammals are having on our fish is well-established.”
The chart below shows the numbers of Steller sea lions at Bonneville Dam in 2018 and through the first week of January 2019, compared to the recent 10-year average.