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Spring Chinook Return ‘Appears To Be Significantly Later Than Normal’; Water Record-Breaking Cold
Posted on Friday, April 29, 2011 (PST)

The jury is still out regarding the strength of the 2011 upriver spring chinook salmon return to the Columbia River basin despite a sudden flexing of muscle this week.


Daily counts at Bonneville Dam’s fish ladders had been lagging, climbing over 200 for the first time on April 20, and then ramping to 539 by this past Sunday. Monday’s count was 1,019 and then the tallies ballooned to 4,787 on Tuesday and 4,690 on Wednesday.


The Technical Advisory Team met Monday to review the run status, noting that the cumulative adult spring chinook passage at Bonneville through Sunday was 3,826 fish. TAC is made up of representatives of federal, state and tribal fish management entities. The panel meets periodically throughout the year to review available data and develop and update run-size forecasts for salmon and steelhead stocks returning to the Columbia-Snake system to spawn.


“This is the second lowest cumulative count to date in our dataset (1980-2010) -- 2006 was the lowest cumulative count at 734 fish,” according to a statement produced following the meeting. Even with the spurt, the count through Wednesday -- 14,322 – remains the second lowest in recent memory. This year’s total through April 27 is slightly lower than 2009’s total of 15,477 through that date but much higher the 2,241 count through April 27, 2006.


“The spring Chinook run timing at Bonneville appears to be significantly later than normal,” the TAC statement says. “The run may be weaker than anticipated, or very late, or a combination of both.


“If the spring Chinook passage over Bonneville Dam turns out to be more normal timed, then the total abundance will be considerably less than the forecast.” In four of the five previous seasons the upriver spring chinook season has been later timed than the historic average with half of the run having passed the dam, on average, on May 8. The 50-percent passage date previously had been in late April.


Bonneville is located at river mile 146. The upriver spring chinook are stocks headed for hatcheries and tributary spawning grounds above Bonneville in Idaho, Washington and Oregon.


Based on the recent five-year average run timing, passage at Bonneville would have been 14 percent complete by Sunday, April 24. The preseason forecast was for a return of 198,400 adult upriver spring chinook to the Columbia River mouth. TAC estimates that, if that forecast is on target, about 180,000 fish of those fish would pass Bonneville by June 15. 


TAC noted the fact that it has been an unusual year. Environmental factors that could be influencing the run timing include water temperature, flow and turbidity.


The water temperature is the coldest to date in the database (1980). The water temperature on April 24 was 47 F compared to the recent five-year average of 51 F. And turbidity has been high with only was 2 feet of visibility as compared to the five-year average of 3.8 feet. Flow for April 22-24 averaged 281,000 cubic feet per second in the lower river as compared to the recent average of 245 kcfs. 


But, “TAC does not currently have a predictive method to use environmental conditions to determine run timing,” the statement says. It said that the panel did not yet have enough data make an updated upriver spring chinook forecast. TAC will be meeting every Monday through the season to review dam counts, harvest numbers and other data and will likely update the run forecast in early May.


A slow start doesn’t necessarily doom the run. In 2006 the final run-size forecast was 132,583 adults to the mouth of the Columbia and in 2009 the final count was 169,296. In 2007, which was another late timed run, the count through April 27 was 23,516 and the final river mouth run size was only 86,247, which was slightly higher than the preseason forecast of 78,500.


The home stretch for the 2006 and 2009 late-timed runs took opposite turns. The 2009 return ended up to be only 57 percent of the preseason forecast while the actual 2006 return was 150 percent of the preseason forecast.


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