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Despite 2007's High Jack Count, 2008 Spring Chinook Return Numbers Downgraded Again

by Staff
Columbia Basin Bulletin, May 30, 2008

Probably the most unpredictable, and the most savored, of Columbia River basin salmon stocks -- upriver spring chinook – have mystified again, passing upstream later than the historic average for the fourth year in a row and in far fewer numbers so far than had been forecast.

The number of fish passing over U.S. Army Corps of Engineers fish ladders at Bonneville Dam defies to some degree a forecasting bedrock. Last year 16,860 "jacks" were counted at Bonneville, the second largest tally since 1976 and third largest on a record going back to 1960, according to data posted online by the Fish Passage Center.

The return of the 3-year-old fish is a key variable used in estimation of future returns. This year the Technical Advisory Committee predicted in preseason that 269,300 adult upriver spring chinook would return, which would have been the third largest dating back to 1960. The run was expected to be dominated by 4-year-olds, the broodmates or "cohorts" of 2007's large jack class.

But TAC, made up of federal, state and tribal fisheries officials, has through the season gradually toned down expectations, based on lagging dam counts. The forecast was dropped to 180,000 two weeks ago, upped to 190,000 last week after counts rose for a time, then back to 180,000 this week.

The largest return on record, 437,000 adult upriver spring chinook in 2001, followed the highest jack count on record, 21,259 in 2000. The 2002 return was strong as well, 331,000 adults that included 5-year-olds that hatched with the jacks that returned in 2000.

Next year's adult return will include 5-year-old broodmates of that strong 2007 jack return and the 4-year-old mates of what is already the third highest jack count on record, surpassing last year's total. The jack count through Wednesday is 16,853 with a few hundred still passing each day. Chinook passing Bonneville are counted as spring chinook through June 15.

"There was one day that it was the highest (count) that I've seen in at least eight years," the Washington Department of Fish and Wildlife's Robin Ehlke, who also chairs TAC. The daily jack counts peaked May 14-15 at 2,035 and 2,009 and have since slowly declined to a few hundred a day.

The cohort relationships on which adult forecasts have traditionally been based are usually near the mark for other stocks, such as fall chinook. The upriver spring chinook forecasts, however, have had their ups and downs.

In 23 years of forecasting charted in the WDFW's and Oregon Department of Fish and Wildlife's 2008 Joint Staff Report, preseason forecasts have come within 25 percent 10 times. In five of those years the actual return was somewhat larger than predicted and in five years it was somewhat lower. In four of those years the forecasts were within 10 percent.

After a 2005 preseason forecast missed badly -- the actual return was only 42 percent of what was forecast -- TAC asked the NOAA Fisheries Service's Northwest Fisheries Science Center to review the forecast methodology, which was judged to be sound, Ehlke said.

"Ocean conditions probably play a pretty big part" in determining just how many salmon survive and return to spawn, Ehlke said. Little is known about the upriver spring chinook's migrational pattern – where they go, and when, after they exit the freshwater system.

Since most mortality is believed to occur early in their saltwater sojourn, strong jack counts would seem to be evidence that that brood had encountered a nourishing environment. That only makes this year's return more puzzling, she said.

The ever-changing ocean conditions that greet juvenile salmon are not, at least for now, factored into the forecasts.

"It's just a matter of refining and coming up with a method that incorporates both," Ehlke said.

The adult upriver spring count through Wednesday totaled 121,825. The highest daily counts this year were 6,340 and 9,686 on May 3-4. The procession then slowed before climbing again to 5,596 and 5,349 on May 14-15 before swooning to as low as 529 one day last week. The run then showed a mini-rally with counts averaging about 1,500 the first three days this week.

The Bonneville counts would higher but for the harvest of salmon downriver by humans and sea lions.

The Columbia River from Bonneville to the mouth was closed to spring chinook retention by anglers April 20. It is estimated the recreational catch in the lower river totaled 20,040 chinook with the vast majority being upriver fish.

Three mainstem commercial fishing periods (all tangle net) were conducted in the area from the Hayden Island powerlines at Portland upstream to Beacon Rock between April 1 and April 15. There were 5,938 chinook, again nearly all upriver stocks.

Corps researchers have observed at least 4,000 spawning salmon being taken in the area immediately below Bonneville by predatory sea lions. Little data is available to document sea lion impacts on the spring run in the Columbia in the reaches from the dam 146 miles to the sea.

State officials estimate that the non-tribal mainstem harvests have exacted a 2.07 percent impact on the upriver spring chinook run based on the latest forecast. That exceeds a 1.9 percent cap imposed as a means of limiting the harvest of stocks within the run that are protected under the Endangered Species Act. A run size of 196,000 fish or larger is needed to put non- Indian impacts at or below the 1.9 percent limit.

Staff, Associated Press
Despite 2007's High Jack Count, 2008 Spring Chinook Return Numbers Downgraded Again
Columbia Basin Bulletin, May 30, 2008

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