Beaver Deceiver — Beaver Dams Along the Skagit River (closed caption)


spawning salmon are an icon for the pacific
northwest While City Light dams on the Skagit river
don’t block fish passage they have reduced existing downstream
spawning areas because of flood control and power generation city light has been a lot of time and
money restoring that lost spawning habitat by preserving existing natural areas and by constructing new ones the power line spawning channel is a
combination of both Built on land used for the electric
utilities transmission lines to bring power from the generation project to
seattle the man-made aquadic channels joins
an existing natural slew and provides fish an off river area to lay eggs the cost was nearly three hundred
thousand dollars Off channel habitat is formed through flooding of rivers because we have our project in
the headwaters would no longer have the magnitude of the frequency of floods
that we once did for the river is not capable of building this type of habitat
which is essential for coho and chum production since two thousand four this spawning channel has attracted thousands of salmon the restoration not only attracted salmon
but another damn builder the beaver The quality of habitat within these channels is ideal for beaver.
jason hall is a research fish
biologist with the federal marine fisheries division in the law he’s been working with city like
biologist Dave Pflug at the power lines channel site it turns out that the gently flowing
water and restored vegetation was perfect for the aquatic rodent known for their big
wood-knawing front teeth flat tales their construction of dams
I think they build dams for several reasons one would be too provide habitat at a secure location from predators and also the increased uh… servicer area of water produces more area for their food source to grow
They really like willow cottonwood a lot of aquatic vegetation that grows in and then around the riparian area the beaver dams block fish and city like built this morning channel
for fish not beaver so why not just rip out the dams well you’ve probably heard the phrase
busy as a beaver They can completely rebuilt or build new dams overnight they’ve built very sturdy dams which required uh… sometimes up to eight hours to remove one dam. so the federal fish biologist and city
light decided to experiment with the device the tricks the beaver into thinking for they have successfully damed small channel it’s this box called a beaver deceiver turns out beaver dam building behavior is
triggered in part by the sound of flowing water this large box allows the flow to
continue but reduces the sound in addition it does constrict water flow
enough to allow a pond to form in this experiment the beaver have
gratefully incorporated the box into the their dam structure however the deceiver is really a fish ladder
and culvert which provides this large pipe for the
adult fish to swim from the river into the spawning channel in the spring the small fry are able to
bypass the beaver dam by way of a fish ladder constructed inside the box the beaver have their protection and
increase food source and the fish have a passageway to and from the spawning channel turns out the beaver actually helped
make this spawning channel more productive they’ve been really heavily reinforce the
dam and that helps us uh… puts more water through the fish ladder which increases fish passage
we have problems with flow before due to seepage and the beaver have
here have effectively uh… channeled all the
water through the fish ladder if this experiment is deemed a success by
the biologists it could be a big benefits or other
agencies trying to restore natural habitat another local agency tackled the beaver
problem by building a permanent structure that cost about one hundred thousand
dollars the beaver deceiver cost about five hundred dollars peter clarke reporting for seattle city
light

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