Evaluating the Sensitivity and Use of Mild Electronic Barriers with Marine Mammals
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. |
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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. |


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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. In early 2014, Dr. Zeligs aided in the assessment of the oil platform for a deterrence barrier. A barrier was installed and proved successful in deterring sea lions during a construction phase where the activities on the platform might have posed a risk to the sea lions. Further deployments of electronic barriers on oil rigs are now being considered. |