Sea Lion Predation Impacts on Salmon and Steelhead in the Lower Columbia River, a Growing Problem

Marine mammal predation on Columbia River salmonids is a new and growing impact to salmonids. In 2015 over 8,200 salmonids were predated by sea lions within ¼ mile of Bonneville Dam. Additional sea lion predation occurs beyond the monitoring program. We implemented a project to estimate abundance of sea lions in the lower Columbia River, estimate salmon predation outside the Bonneville Dam observation area, and conduct non-lethal hazing of sea lions in the Bonneville Dam tailrace. Ten weekly tandem boat surveys resulted in sea lion abundance estimates ranging from 49 to 2,008 sea lions located between Bonneville Dam and Astoria, OR (RM 15), which is a six-fold increase over last year. In an effort to eventually estimate sea lion specific predation, we attached accelerometer tags to 6 different sea lions to assess predation signals.  This technique is showing great promise to remotely quantify the number of salmon consumed each year by sea lions. CRITFC hazed sea lions for a total of 31 days from 3/06/2015 to 5/13/2015 in the tailrace of Bonneville Dam.  Hazing resulted in 361 hazing events on 476 and 222 California sea lions (Zalophus californianus) and Steller sea lions (Eumetopias jubatus), respectively.