Donations Link
Contact Us Link

Testing Electronic Barriers as a Deterrence Method with California sea lions: Overall, it is currently estimated that sea lions consume over 4% of the salmon at Bonneville Dam in the Columbia River on an annual basis. Seals were estimated to have consumed 1,161 salmonids in the Alsea River, Oregon in 2002, with an inferred consumption of 21% of the returning coho salmon (O. kisutch) in upriver locations.

Adult male California sea lions were responsible for 98.4% of the observed depredations of hooked salmon in 1997 to 1999 commercial and recreational fisheries in Monterey Bay, with an economic impact to commercial fisheries of about $500,000. Various harassment techniques have been employed by government agencies in efforts to deter fish predation by marine mammals in the Pacific Northwest. Such programs have been time consuming and expensive to implement. Although salmon runs have declined for various reasons over time, predation by marine mammals may affect the ability of fishery managers to recover listed salmon and steelhead runs. These difficult conservation issues have led NOAA to approve site-specific management authorities to allow lethal pinniped removals where necessary. New and alternative technologies must be researched to help reduce the pressure to use lethal methods of deterrence and supplement lethal deterrence methods.


Underwater electronic barriers are non-lethal detterent devices that show great promise in excluding marine mammals from established fish predation areas, and in blocking the upstream movements of pinnipeds that follow Pacific salmon runs in search of prey. Electric barriers have been safely used for decades to restrict the movements of animals and fish, and to control invasive species.

   In 2007, SLEWTHS developed a collaboration with the leading electronic barrier company in the country, Smith-Root Inc. to evaluate the use of electronic barriers to deter California sea lions with and without food present. In May 2008, SLEWTHS conducted the first laboratory trials of the underwater electronic barrier, which indicated real success with this deterrence method. In the coming years, field trials will continue to help modify and develop this new technology. SLEWTHS is proud to be involved with helping to solve such an important conservation issue for both pinnipeds and endangered fishes.
Updated November 2008