Quantifying Sea Lion Predation on Steelhead, Salmon, Lamprey and Sturgeon below Willamette Falls, Oregon

Extensive actions have been undertaken to increase the survival of federally listed salmonids and other native fish species in the Columbia River Basin (e.g., through changes to harvest, hatcheries, hydropower, and habitat).  Despite these efforts many fish stocks in the basin continue to decline or remain at risk. Increasing numbers of seals and sea lions in the river represent a growing threat to such stocks.  While sea lion predation on listed salmonids at Bonneville Dam on the Columbia River is a well-known problem, a similar issue exists below Willamette Falls on the Willamette River, a tributary of the Columbia River.  We present the results from two years (2014, 2015) of sea lion monitoring work below Willamette Falls aimed at quantifying predation on ESA-listed upper Willamette River winter steelhead (Oncorhynchus mykiss) and spring Chinook salmon (O. tschawytscha), as well as on summer steelhead and hatchery spring Chinook, Pacific lamprey (Entosphenus tridentatus), and white sturgeon (Acipenser transmontanus).  This monitoring data is essential to understanding the magnitude of the predation problem and for deciding whether future management action should be taken.