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Sea Lion Predation Rate Estimation and Non-lethal Hazing

To implement a tracking and hazing effort on sea lions at Bonneville Dam in an effort to reduce their predation on salmonids and other fish. This predation has increased dramatically since 2001. With more sea lions below Bonneville Dam, the number of adult salmonids caught has also increased over the same time period. The loss of returning adult fish to sea lions predation results in fewer fish surviving to spawn, thus reducing spawning potential and recruitment. Additionally, we are devising methods to estimate sea lion abundance in the lower Columbia River.

Sea lions on the shore near Bonneville Dam

Sea lions on the bank near Bonneville Dam

Project Goal

To implement a tracking and hazing effort on sea lions at Bonneville Dam in an effort to reduce their predation on salmonids and other fish. This predation has increased dramatically since 2001. With more sea lions below Bonneville Dam, the number of adult salmonids caught has also increased over the same time period. The loss of returning adult fish to sea lions predation results in fewer fish surviving to spawn, thus reducing spawning potential and recruitment. Additionally, we are devising methods to estimate sea lion abundance in the lower Columbia River.

Impacts

Better accounting of sea lion predation in the lower river and decreased sea lion predation near Bonneville Dam.

Sea Lion Hazing near Bonneville Dam

Sea lion hazing efforts below Bonneville Dam.

Background

We are collaborating with the states of Oregon and Washington on this project. The states were granted authority to lethally remove problem California sea lions at Bonneville Dam by NOAA Fisheries through section 120 of the Marine Mammal Protection Act. We are conducting boat-based non-lethal hazing from about March through May to drive animals away from the dam. Additionally animals must be subjected to non-lethal hazing as a condition to adding them to the removal list. Our second project component is tracking movements of California sea lions using acoustic telemetry. These data provide insight into feeding habitats and distribution both near Bonneville and throughout the lower Columbia River. Our third project component is to develop a methodology to enumerate sea lions throughout the lower river. Currently we are testing a mobile video-based system to recording sighting within a specific area. These records could then be used to estimate sea lion abundance. CRITFC along with representatives from each member tribe participate in the Pinniped Fisheries Interaction Task Force.

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