Columbia Basin Bulletin
LEWISTON, Idaho — For the last 27 years, the Nez Perce Tribe, Idaho Power, U.S. Fish and Wildlife Service and Washington Department of Fish and Wildlife biologists have been conducting fall chinook salmon redd surveys in the lower Snake River and most major tributaries above Lower Granite Dam in southeast Washington.
A redd is a spawning nest that is built by salmon and steelhead in the gravel of streams or the shoreline of lakes.
Lower Granite is the last dam on the Snake River with a fish ladder.
Sea-run fish migration stops at Hells Canyon Dam, about 95 miles upstream from Hells Gate State Park located four miles south of Lewiston.
The 2014 survey estimated a total of 6,715 Snake River fall chinook salmon redds (river bottom nests) in the Snake River basin – the highest total recorded since intensive surveys began in 1988.
The 2014 estimate was 324 redds more than the previous high estimate of 6,391 in 2013, according to survey summary report.
There were an estimated 2,800 redds in Snake River reaches upstream of Lower Granite. Fall chinook passing over Lower Granite can spawn in the mainstem or veer off into tributaries in Wash., Oregon and Idaho.
Lower Granite is the eighth and final hydro project the fish must pass on their way up the Columbia and Snake rivers. Farther up the Snake, their journey is halted at Idaho Power’s Hells Canyon Dam, an impassable facility about 140 river miles upstream of Lower Granite.
The 2014 estimates include 3,118 redds in the Clearwater River, a tributary that joins the Snake near the head of Lower Granite’s reservoir at the Idaho-Washington border. The Clearwater flows out of central Idaho and joins the Snake at Lewiston.
The lowest redd count for the Clearwater River sub basin since intensive surveys began was 4 redds in both 1990 and 1991, while the highest count was 3,118 redds in 2014.
The Nez Perce Tribe has led that hatchery effort with its “supplementation” program, which acclimates juvenile hatchery fish before their release near their historic spawning grounds in the Clearwater basin and lower Snake River. Those fish come back to those areas to begin a cycle of natural reproduction.
That tribal program began in 1996, and returns ever since have been increasing.
The overall count of adult fall chinook passing over Lower Granite in 2013 was also at an all-time high, since the dam was completed in 1975, at 56,565. That was nearly 15,000 higher than the previous high, 41,815 in 2010.
The high Snake River totals largely mirror overall fall chinook returns to the Columbia over the past two years. In 2013 was a modern-day record (likely dating back to at least 1938). The total fall chinook return that year to the mouth of the Columbia was an estimated 1,268,400 adult fish, which was 227 percent of the 2003-2012 average.