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2011 Salmon Forecast: Summer Chinook May Be Record Breaker, Upriver Spring Chinook Near Average
Posted on Friday, December 10, 2010 (PST)

Fisheries officials predict that the 2011 return of summer chinook salmon to the mouth of the Columbia River will be the largest on a record dating back to 1980. And the upriver spring chinook forecast is for a return very close to the recent five-year average.


The Technical Advisory Team completed its preseason forecasts Thursday for the upriver spring chinook run and for two of its components – the Upper Columbia spring chinook and Snake River spring/summer chinook stocks. TAC also completed forecasts for Upper Columbia summer chinook and sockeye salmon returns. TAC is made up of federal, state and tribal officials.


TAC predicts that a total of 91,000 summer chinook will return to the mouth of the Columbia next year. The 2010 return was adult 72,346 fish. The record return was 89,543 in 2002.


Summer chinook are bound for spawning grounds and hatcheries upstream of Priest Rapids Dam. Historically, these fish spawned in the Columbia, Wenatchee, Okanogan, and Similkameen rivers, but access to more than 500 miles of the upper Columbia River (excluding tributaries) was blocked by the construction of Grand Coulee Dam in 1941, according to the 2010 Spring Staff Report prepared by the Oregon and Washington departments of fish and wildlife. The building of Chief Joseph Dam further reduced available mainstem habitat.


Summer chinook redds are now found in the Columbia, Wenatchee, Okanogan, Methow, Similkameen, Chelan and Entiat rivers.


The upper Columbia summer chinook run size remained at low levels throughout the 1980s and 1990s, with average returns of 19,400 and 15,300 fish, respectively. Hatchery supplementation programs and improved natural habitat have played a significant role in the increased abundance trends observed since 1999. The Upper Columbia summer chinook stock is now considered healthy and is not protected under the Endangered Species Act, in contrast to the wild portions of 13 other Columbia Basin salmon and steelhead stocks.


The forecast is for a return of 198,400 upriver spring chinook, fish headed for tributary spawning grounds and hatcheries in the Snake River basin and the mid- and upper Columbia. That about matches the 2005-2009 average of 203,100, but falls well short of 2010’s total of 315,345. Last year’s return was the third largest dating back to at least 1980.


The return includes a larger-than-normal number of 5-year-olds, 40,000 fish as compared to 158,400 4-year olds. Last year the ratio was 307,348 4-year-olds to l7,855 5-year-olds. The anticipated high 5-year-old count is due to the fact that an all-time record number of 3-year-old jacks returned in 2008. They are the broodmates of this year’s 5-year-old fish.


“We’re expecting quite a few 5-year-olds,” said TAC Chair Kathryn Kostow of ODFW.


The 2011 forecast is for a return of 22,400 Upper Columbia spring chinook, including 2,000 wild fish. The return last year was 38,083, including 3,147 wild fish. The Upper Columbia spring chinook are a component of the upriver run that includes populations that originate upstream of the mid-Columbia’s Priest Rapids Dam in central Washington. The wild fish are ESA-listed.


The new forecast pegs the Snake River spring/summer chinook adult return to be 91,000 in 2011. That total includes an estimated wild return of 24,700. The Snake River spring/summer run originates upstream of Lower Granite Dam on the lower Snake River in southeast Washington. Again, the wild fish are protected.


The forecast sockeye return for 2011 is 161,900, which would be less than half last year’s 387,858 total. Most of the sockeye (159,800 forecast) will be bound for the Wenatchee and Okanagan river basins in central Idaho and southern British Columbia. TAC predicts that the Snake River sockeye return will total 2,100, just shy of 2010’s modern-day record total of 2,596.


During the 1990s the number of sockeye returning to the Snake River basin averaged 12 fish per year, according to the staff report. During 2000-2007, Snake River sockeye returns improved over the 1990s but the run remained severely depressed with average annual returns of less than 100 fish.


The 2008 sockeye return to the Snake River of 984 was the highest since at least 1980, and was surpassed in 2009, perhaps signaling the beginning of an upward trend for Snake River sockeye. The total return of sockeye in 2008 was the largest since 1959.


The 2009 Columbia River return of 1,400 Snake River sockeye was the highest observed since at least 1980, far exceeding the recent 10-year average (81 fish), and was over ten times the average annual return observed since 1980.


TAC has in recent years been working to improve the accuracy of its forecasts. This year the panel looked at multiple statistical models for the upriver spring chinook forecasts, including more than 40 models just to predict the age 4 fish abundance.


The models included linear and logarithmic sibling regressions, multiple regressions, cohort ratios (ratio of younger/older age classes), and historic relationships among return groups.  Variables that were considered in these models include jack counts at Bonneville, Lower Granite and Rock Island dams, an index of jacks returning to areas upstream of Bonneville Dam, different years of historic sibling relationships, and environmental variables including spill at Columbia River dams and the ocean Pacific Decadal Oscillation index.


Models were selected based on statistical indices of model fits and historic forecasting success from hind-casting analyses. Subsets of models were selected for each forecasted group and the final forecasts were ensemble means of these subsets.


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