Fish ladders in action

December 23, 2016 0 Comment(s) Animal Ladders, Fish Ladders,
Over in America the fish spawning season is underway, which means that the numerous fish ladders that sit along many of the great American waterways are seeing lots of action.  The Nimbus fish ladder, on the American River in California is especially busy at this time of year, as Chinook salmon return to their spawning grounds.  There are eight hatcheries in the area, all of which make use of the fish ladder to catch salmon and harvest eggs; approximately 24 million of them over the season, to breed young salmon for release in the spring of 2017.  It is open to the public and has plenty of educational resources, so everyone can enjoy the spectacle of the returning fish jumping upstream through the ladder and learn about the conservation efforts of the hatcheries.  Viewing windows allow visitors to see the spawning in progress.Also in California is the brand new fish ladder, at Forestville on the Russian River.  Built to the tune of $12 million, the concrete structure is helping maintain and protect the salmon and steelhead populations as they try to access historic spawning grounds in Sonoma County.  The project was completed in August; in good time for the expected October start of the salmon run, and to date there have been 531 fish counted through the fish ladder.  This is a great start, as just two years ago only 67 had been counted at the same stage of the season.  There is hope that the target of 3,000 will be reached this year, and locals can make use of the viewing window to get a close up look at the fish swimming through the ladder, the majority of which was funded by local residents.In Ashaway, Rhode Island, herring are starting to return to their spawning grounds on the Pawcatuck River.  The Potter Hill fish ladder has been in place for 40 years, and in that time has been subjected to changing weather and floods, which has shifted a lot of sediment and debris downstream.  This sediment has settled into a berm, which in turn has changed the water flow at the entrance to the fish ladder creating a counter eddy that confuses the fish.  Instead of swimming up the fish ladder, the herring become disorientated by the water flow and end up going back downstream instead of up the ladder.  The U.S. Fish and Wildlife and The Nature Conservancy projects worked together with landowners and the owner of the Potter Hill ladder to undertake a dredging task that removed the sediment and restored the channel to its natural state, thereby recreating the outflow from the fish ladder that attracts returning herring into the channel and upstream to the spawning grounds.  They can now return with ease, conserving their energy for spawning and raising the young in preparation for the trip back down the river and out to sea in the spring.The Alouette Dam in Canada is at the head of the queue for a fish ladder to enable sockeye salmon and trout to return to Alouette Lake from the river.  The dam was built in 1928 and provides hydroelectric power to British Columbia, in conjunction with other dams and solar farms.  The sockeye population has declined considerably over the years, with only seven fish returning last year.  These were manually relocated to the lake above the dam, but better provisions need to be put in place, especially if B.C. Hydro, the operator of the dam, wishes to renew their water license in 2018.  It is hoped that the fish ladder project will be started in the next year or so and will help the conservation effort for sockeye salmon in Canada.  We will bring you updates as they happen.

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