A new $51 million wall constructed in the Columbia River below The Dalles Dam significantly boosted survival of juvenile salmon and steelhead migrating downstream past the dam this year, according to research presented recently at a major gathering of fish scientists in Portland.
Studies showed that 96 percent of yearling Chinook salmon passed the dam safely this year, up by 4 percent over similar tests in 2004 and 2005. The studies also found that 94 percent of sub-yearling Chinook passed downstream safely, up by 7 percent. Also, 95 percent of steelhead survived past the dam, although past steelhead survival is not available for comparison. The data was presented at the U.S. Army Corps of Engineers’ Anadromous Fish Evaluation Program Annual Review conference in Portland.
Survival targets established by the National Marine Fisheries Service’s 2008 biological opinion on the operation of the Federal Columbia River Power System for salmon and steelhead listed under the Endangered Species Act are 96 percent for both yearling Chinook salmon and steelhead smolts, and 93 percent for sub-yearling Chinook salmon.
Fish biologists with the Corps’ Portland District, which operates The Dalles Dam, credit the construction of the wall between spillway bays eight and nine for much of the increase in survival. The wall is 10 feet wide and 850 feet long and helps guide young fish passing through the dam’s spillways into the safest part of the river, away from predators.
About 80 percent of juvenile fish pass over The Dalles Dam’s spillway. The new wall directs the flow of water from the spillway to the deepest part of the river’s channel, moving young fish away from low flow and shallow areas where they are at risk of predation from other fish and birds. Northwest power consumers will repay the costs of the wall over the coming years.