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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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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.
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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. |
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