Chinook Salmon Population Still Strongby Idaho Power
Consumer Connections, March 2013
The five highest redd counts of the past 21 years have been recorded in 2008-2012.
Since 1991, Idaho Power has been counting the nests, or "redds," of fall Chinook salmon that return to spawn in the Snake River and its tributaries below Hells Canyon Dam. Spawning female salmon use their tails to clear gravel before laying their eggs on the river bottom. These areas are visible as light-colored patches and provide an important piece of information to researchers studying trends in the salmon population.
Poor visibility made the 2012 survey particularly challenging, but biologists say the overall health of the Snake River's fall Chinook population remains strong.
"This year's numbers were not what we expected, especially given the fairly strong return of adults," Idaho Power Senior Biologist Phil Groves said. "Summer fires reduced ground cover leading to increased erosion. This, combined with non-stop rain through the fall, caused most of the tributaries to run turbid during our survey season. As a result, the main stem Snake River also ran turbid, reducing our ability to see the redds."
Some aerial surveys were limited by weather that hampered helicopter flights in the narrow canyon.
The fall survey is done in conjunction with several cooperating agencies, including the U.S. Fish & Wildlife Service and the Nez Perce Tribe. It includes the 100-mile stretch of the Snake River below Hells Canyon Dam, as well as the Clearwater, Grand Ronde, Imnaha and Salmon rivers. Biologists survey the area via helicopter and from riverbanks. They also use a remote-controlled aerial vehicle equipped with a camera.
Idaho Power's Fall Chinook Program is part of our commitment to stewardship of the river which provides about half the electricity used by our customers.
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