Biologists in Idaho Power’s environmental program this fall observed more than a 40 percent increase in the number of Snake River chinook salmon nests, or redds, compared with the previous year.
Likewise, fall chinook returns to the Clearwater River drainage spiked from 1,198 in 2009 to a record 1,924 this year, according to redd counts conducted by the Nez Perce Tribe. The Clearwater counts have been conducted since 1988.
The tribe also counted 263 redds in the Grande Ronde River (the previous high was 197 in 2001) and 132 in northeast Oregon’s Imnaha River (previous high 72 in 2002). The Grande Ronde, which flows from Oregon and across the southeast corner of Washington, both flow into the lower Snake.
The count of 2,944 redds between Hells Canyon Dam and Asotin, Wash., in the lower Snake is the largest number since annual surveys began in 1991, when only 42 redds were counted.
“It’s great to see such a strong increase in the numbers of fall chinook salmon returning to the Snake River,” said Jim Chandler, Idaho Power fisheries program supervisor. “These numbers reflect our commitment to protecting the environment for this species of fish by providing stable flows and habitat during the spawning and incubation period.”
As part of Idaho Power’s program, from Oct. 11 through Dec. 12 the company manages Hells Canyon Project outflows at approximately 8,500 cubic feet per second. The action is intended to help protect fall chinook salmon that spawn and incubate downstream, while continuing to produce power for Idaho Power customers in southern Idaho and eastern Oregon.
From late October through early December, biologists with Idaho Power and the U.S. Fish and Wildlife Service conducted four aerial surveys downstream from Hells Canyon Dam. More than 1,890 redds were observed in shallow-water habitat during helicopter overflights. An additional 59 redds were observed during ground verification, and 994 redds were observed in deep-water habitats using remote underwater video.
Of the 2010 total, approximately 40 percent of chinook redds were observed in the Snake River downstream of the confluence with the Salmon River, while 60 percent were upstream of the Salmon River.
Idaho Power biologists say that many factors in addition to the stable-flow program are contributing to increases in salmon redds. Among those factors are hatchery supplementation programs, good out-migration conditions for young fish heading to the ocean and favorable ocean conditions, they say.
Following the stable-flow program, outflows into the Snake River resume fluctuating daily in response to the need for power from the hydroelectric project. The company continues to maintain a minimum flow of approximately 8,500 cfs to protect incubating chinook embryos until incubation is complete around mid-May.
More information about the fall chinook salmon spawning flow program is available at www.idahopower.com/ourenvironment