[4] 2007 Snake Fall Chinook Run Makes Big Gain

Harvest managers weren't making much of a fuss over their recently released estimate of last year's Snake fall chinook run, about 7,600 fish. It was included in a table in their July 22 fact sheet that announced their estimates of this year's expected returns, about 6,400 ESA-listed wild fall chinook, about 140 percent of the 10-year average.

But the 2007 return of 7,600 fish would make it by far the highest since the fish were listed for protection under the ESA.

WDFW's Robin Ehlke told NW Fishletter that the number was not a typo, and was expected to change little, if at all, with further analysis. That means last year's return was about three times higher than the ESU's interim recovery goal of 2,500 fish.

USFWS researcher Billy Conner said biologists are still trying to estimate how much of a boost the supplementation effort has had on the returns, when hatchery fish are allowed to spawn in the wild. It's obviously had some benefit. The 2007 wild return is nearly a hundred times better than the 1990 return, when only 78 wild fall chinook passed Lower Granite Dam.

But it's been hard to count returning fish at Lower Granite Dam, and identify whether they are wild or of hatchery origin. Over the years, many hatchery fish from the Nez Perce facility on the Clearwater River have not been marked. Once hatchery fish have successfully spawned in the wild, there has been no way to tell them apart from the original wild component. But biologists are working on a way to read the fishes' DNA to do just that.

However, since supplementation efforts began, many more fall chinook redds have been found in four major areas, Conner said, in the mainstem Snake below the Salmon River, in the mainstem above the Salmon, in the lower reaches of the Grande Ronde, and in the Clearwater.

Most biologists attribute the big boost in the wild run to the success of the supplementation effort focused at Lyons Ferry Hatchery in the lower Snake. Young fish are raised there and then trucked above Lower Granite to acclimation ponds. Fall chinook from the Nez Perce Hatchery have added to the numbers as well, since they have been allowed to spawn in the Clearwater, where no fall chinook run previously existed, a situation likely due to the extremely cold water compared to traditional spawning grounds in the lower Snake. -B. R.

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