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Early Run Forecasts Predict Record Return Of Naturally Produced Snake River Fall Chinook
Posted on Friday, February 25, 2011 (PST)

Run-size forecasts completed this week include an expected return this year to the mouth of the Columbia of 17,500 Snake River “wild” fall chinook salmon, a stock that is protected under the Endangered Species Act.

 

Such a return would break the record, 15,400, set last year. The low return on a record dating back to 1986 was just 772 wild fish in 1998. The wild Snake River chinook return to the mouth of the Columbia was only 4,086 in 2009.

 

“The simple message is we’re expecting a whole lot of fish,” said Columbia River Inter-Tribal Fish Commission fishery biologist Stuart Ellis. He serves on the U.S. v Oregon Technical Advisory Team, which produces the forecasts in large part based on relationship between age groups of fish.

 

Among the variables judged was the fact that there was “a very huge number of age 3 fish” in the overall 2010 return, Ellis said. Of the 9,583 naturally produced fish (also a record) estimated to have passed over the lower Snake River’s Lower Granite Dam, 6,900 were age 3 with most of the balance being 4-year-olds. Lower Granite is the eighth and final dam the fish pass on their way up the Columbia/Snake River on their spawning journey. That should translate to a relatively big 4-year-old return this year.Ellis stressed that the estimates are preliminary.

 

“Usually it would be closer to 50-50,” though 3-year-olds typically hold somewhat of a majority, Ellis said. Last year’s 3-year-olds were the broodmates of 2-year-old jacks that returned in 2009 in record numbers. The total jack count, including hatchery and wild fish, in 2009 was 41,288. That translated to a huge overall return, dominated by 3s, of 41,815 adult fish in 2010.

 

The next highest jack count on a record dating back to 1975 is 12,895 in 2010. That pales in comparison to 2009 but still bodes well for 2011’s 3-year-old class, which are the broodmates of last year’s big jack return.

 

The overall numbers are on an upward trajectory, with peaks and valleys. From 1999 through 2010 the adult fall chinook counts at Lower Granite ranged from 3,384 to that 41,815 total (second highest count was 16,628 in 2008). From 1975 through 1998 the range was 337 to 1,909.

 

The wild fish estimates have been up (14,303 adults in 2001, which was a banner year for many fish stocks) and down (2,475 in 1999) during the 1999-2010 period but have been generally higher than the 1986-1998 period. Numbers rose slowly during the first half of the current decade, then dropped a bit before taking a big jump last year.

 

The increase in naturally born spawners is being boosted to some degree by hatchery supplementation, the practice of acclimatizing hatchery produced juveniles at streamside near spawning grounds before their release. They then head to the ocean and, if they make it back to freshwater to spawn, home in on the area of the river where they released.

 

“A fair number of these fish came out of the gravel, but their parents were of hatchery origin,” Ellis said. Some may be two or more generations removed from the hatchery. The fall chinook acclimation project led by the Nez Perce Tribe began in 1996. The program involves bringing hatchery produced juvenile fish to three "acclimation" sites – two on the lower Snake and one on the Clearwater River -- for their final rearing before release. The sites are located near major natural spawning areas.

 

“It’s interesting because it’s looking like the supplementation is beginning to do what we wanted it to do,” Ellis said, which is increasing the abundance of both marked harvestable fish and wild spawners.

 

“It’s a package deal. We’re doing a lot of things at once,” Ellis said of more conservative fisheries, improved hatchery operations, habitat restoration efforts upstream and down and more fish friendly hydro operations. Ocean conditions play a role in causing the typical ups and downs in the size of returns from year to year. But the general trend seems to be upward.

 

“Hopefully this will become a regular event,” Ellis said. He cautioned that the forecast is just that, a forecast, and produced without anything to compare it to given the unprecedented jack numbers two years ago and adult numbers last year.

 

But, Ellis said, “I think are easily going to see a run as big or bigger than last year.”

 

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