[1] 80,000 Jacks Can't Be Wrong, Or Can They?

The upriver spring chinook run in the Columbia River is officially over, but thousands of fish bound for the Snake River are still passing Bonneville Dam, along with more jacks than seen in living memory. In fact, about half of this year's 170,000-fish spring run has turned out to be jacks.

And those precocious males that swim home a year early have rolled in at a pace that has astonished both scientists and fish managers--more than 80,000 of them this year have been counted at Bonneville Dam--that's more than three times the modern record when more than 24,000 were counted in 2000, an early signal to the more than 400,000-fish run in the spring of 2001.

Does that mean more than a million spring chinook will show up next year?

Nobody is actually saying so, but a few optimists are speculating that actually could happen. Most managers and scientists are guardedly optimistic that next year will likely be something of a bonanza, but when pressed, they find it almost impossible to quantify, especially after this year's prediction was so far off, based on their old, somewhat workable methodology built mostly on last year's high jack count.

It's been a real roller coaster of a data base as well. Back in 1998, the spring jack count up at Lower Granite Dam, where most of the upriver run was headed, was made up of a measly 435 young fish. A year later, it jumped to 4,000, and by 2000, 14,000 jacks were counted there.

One thing seems clear, harvest managers' old jack/2-ocean adult ratio doesn't hold up year after year, and may need some tweaking in the future to take into account the quick, huge changes in ocean conditions that have occurred since the new century began, changes that can shift back just as fast.

On June 3, some researchers from Seattle's NMFS Science Center met with members of the Columbia Basin's Technical Advisory Committee, the group of state, federal and tribal harvest managers created by the US v. Oregon process that make Columbia River fish predictions and set harvest goals that are governed largely by ESA constraints.

One of those attendees, NMFS ocean researcher Ed Casillas, said the huge jack count was even more than his group had predicted from near-ocean trawl surveys in June 2008. They counted more fish than they had ever seen in their years of surveying, and estimated that it could mean a spring chinook jack return this year of 40,000 to 50,000.

Well it turns out that NMFS' estimate of this year's jack return was about 30,000 shy of the 80,000-jack count, and the TAC's old jack/adult methodology led the state and tribal folks to come up with a preseason estimate of nearly 300,000 adults, when only about 170,000 actually showed up.

Most managers admit they are dealing with a lot of uncertainty. Casillas told NW Fishletter changes in ocean conditions, and associated predation, along with the "propensity for young males to jack" may be a factor that is skewing the latest numbers.

Back in 1999, when NMFS' ocean surveys began, they found plenty of small chinook, the highest number until last year, and the relationship developed since then between those catches are following year jack counts has been quite tight. The actual 2000 jack return of 24,000 fish fit the NMFS graph almost perfectly. However, so does the 48,000-jack prediction for this year.

(Courtesy NMFS)

"But ocean conditions were far better in 2008," Casillas said, which may hold the key to the jack count puzzle.

Scientists have been measuring chemicals in smolts to see what might be happening that may be producing more jacks in years with much better conditions for growth. By measuring the insulin-like growth factor and testosterone levels of the young fish, they may be on track to answering why so many more jacks are showing up.

Casillas said in most years, a lot of the young males with a propensity to jack may just not grow enough to reach the stage that triggers their maturity and send them home after only one year in the ocean. But in years of extra-cool ocean waters, high productivity from nutrient upwellings may boost their innate tendency to mature early, and could help account for the huge increase in their numbers.

There had been some speculation that changes in hatchery feed a couple of years ago, might have played a role in the high jacking rate, but Casillas said there is some evidence that jack rates of wild fish have increased as well.

Casillas also noted their May trawl survey showed up 20 percent more juvenile salmon than last year. But it's the June numbers that really count, he added. They were heading to sea in a few days. This might portend even more jacks next year.

The NMFS researchers have pointed out why 2008 seemed so special in nearby ocean waters.

Not only was it the most negative winter PDO [Pacific Decadal Oscillation] since 2000 and most negative summer PDO since 1955, but it was the most negative index of El Niño activity since 1999 (This indicates La Niña, or cold equatorial ocean conditions in the eastern Pacific).

Scientists also found the coldest winter sea surface temperatures of the past 12 years, and both early and strong coastal upwelling, with average upwelling strength during April-May (when juvenile salmon first enter the ocean) the 4th highest of 11 years.

Deep-water temperatures in the continental shelf were the coldest of the past 12 years, while the biological spring transition was the earliest of the past 13 years. Researchers found the highest northern copepod biomass levels of the past 13 years, the types that young salmonids thrive on, because of their high nutrient levels.

On a negative note, they did find that sea surface temperatures were warm from 22 July until 27 August, possibly a negative sign for juvenile coho, and only a moderate number of juvenile coho were caught in their September survey (6th highest of 11 years). More than a million coho are expected to return to the Columbia this year. -Bill Rudolph

The following links were mentioned in this story:

http://www.nwcouncil.org/news/2009/03/2.pdf

Subscriptions and Feedback
Subscribe to the Fishletter notification e-mail list.
Send e-mail comments to the editor.

THE ARCHIVE :: Previous NW Fishletter issues and supporting documents.

NW Fishletter is produced by Energy NewsData.
Publisher: Cyrus Noë, Editor: Bill Rudolph
Phone: (206) 285-4848 Fax: (206) 281-8035