Sea lions have roamed the Pacific coast for centuries, but were not seen entering the Columbia River in significant numbers until the 1980s. Steller sea lions, the larger of two species native to Northwest waters, are now present at the mouth of the Columbia River year-round, but California sea lions spend their annual breeding season at rookeries off the coast of southern California and Mexico. In fall, thousands of adult males and juveniles return north to forage for food along the west coast of North America. In recent years, surveys conducted by the Washington Department of Fish and Wildlife (WDFW) and Oregon Department of Fish and Wildlife (ODFW) estimated there were up to 2,000 – 3,000 California sea lions and 1,000 Steller sea lions in the lower Columbia River near Astoria.
Since the early 1980s, California sea lions have been moving in increasing numbers farther and farther up the Columbia River – first to the Astoria area, then to the Cowlitz River and on to Bonneville Dam, 145 miles from the river mouth. In recent years, California sea lions have been reported above Bonneville Dam, with occasional sightings in Drano Lake and McNary Pool.
Like California sea lions, Steller sea lions have been observed feeding below Bonneville Dam in recent years. Until 2008, their primary prey was white sturgeon, consuming 1,800 of them in the tailrace below the dam within view of observers from the U.S. Army Corps of Engineers. However, by 2016, Stellers also accounted for about one-third of the 8,969 salmon and steelhead taken by sea lions below the dam.
21st of March, 2017