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NW Fishletter #251, September 4, 2008

[1] Fall Chinook Count Climbing Fast

Cool weather and a hard rain likely played a large role in this year's early return of fall chinook to the Columbia River.

Harvest managers had hoped to keep the popular Buoy 10 fishery in the lower river open through the Labor Day weekend, but anglers had caught their 6,500-fish quota by Aug. 25 and the area was shut down for chinook, though it remained open for hatchery coho and hatchery steelhead a few days longer. High catch rates for coho made them shut it down Aug. 31, after more than 10,000 coho were hooked.

"We really haven't seen catch rates like these at Buoy 10 since the late 1980s," said Washington Department of Fish and Wildlife's Cindy LeFleur, in an Aug. 25 press release.

She noted some chinook caught in recent weeks weighed nearly 50 pounds. "We have to make sure we leave enough harvestable chinook for sport fisheries further upriver," she said.

Upriver to Bonneville Dam remained closed to chinook fishing until Sept. 1, then was opened for two weeks.

"Data from coded-wire tags indicates the concentration of upriver bright chinook in the catch is much higher than expected," LeFleur said. "That's significant, because a portion of that stock is made up of federally protected chinook bound for the Snake River, and we need to minimize interception of those fish."

On Aug. 24 nearly 15,000 chinook scrambled past Bonneville Dam. After a few days with counts dropping by two-thirds, chinook began charging past the dam once again--more than 13,000 a day. And yesterday, turned out to be the best day so far this year, when 15,301 were counted.

Nearly 148,000 had passed the dam by Sept. 3. Managers expect about 377,000 to reach the river mouth this year. The University of Washington's Inseason Forecaster on the website at Columbia Basin Research has boosted its estimate from 254,000 preseason (to Bonneville) to nearly 400,000, and says the run is about 38 percent completed.

The harvest managers cut the commercial gillnetters' last fishing period in August, because their catch had exceeded guidelines. Netters landed more than 14,000 chinook during the month. They will be allowed more fishing time in mid-September.

Tribal gillnetters in Zone 6 (above Bonneville Dam) are expected to catch about 32,000 chinook in their platform and gillnet fisheries by Sept. 6, including about 11,600 upriver brights. Managers said that would equate to a 7.1-percent harvest rate "which provides ample room for additional fishing opportunity even if the run size is less than the preseason forecast."

In a Sept. 3 TAC [technical advisory committee] update, the tribal catch was expected to reach 86,400 by Sept. 12, and included 36,000 upriver brights. TAC said that equated to a 21.8 percent harvest rate.

The tribes are allowed up to a 23-percent harvest rate on the upriver bright run size (to the river mouth), as part of the constraints on harvest of ESA-listed fall chinook heading for the Snake River.

The tribal take of B-run index steelhead through Sept. 6 was estimated at 1,490 fish, which is less than a 4-percent harvest rate, while the limit imposed by the latest harvest agreement caps the rate at 15 percent at these abundance levels. The TAC update pegged a 3,700-fish catch by Sept. 12.

But just how accurate are these preseason run estimates used to peg initial harvest rates for the inriver harvesters and sports fishermen?

The technical advisory committee to the U.S. v. Oregon process that analyzes fish returns and makes the harvest calls, released its annual report July 18, including its accounting of last year's wild fall chinook run that made it to Lower Granite Dam on the lower Snake.

The report said 2,016 adult wild fall chinook made it past the dam, from an initial estimate of run size to the river mouth of 7,600 fish. They estimated the Zone 6 harvest rate at 22 percent, based on landings--which means that more than 3,800 wild fall chinook (66 percent) didn't make it through the hydro system.

The 34 percent that did make it from Bonneville Dam to Lower Granite, according to the TAC report, is called the "conversion rate."

But according to data in the latest hydro BiOp, the Bonneville-to-Lower Granite conversion rate for fall chinook in 2007 was around 75 percent, based on the PIT-tag analysis of returning adults.

Debbie Milks of WDFW told NW Fishletter the 2007 wild fall chinook return was more like 3,033 fish, jacks included. But she said that jacks (age 2) only accounted for 11 percent of the run, while 45 percent were age 3s, 27.5 percent were age 4s, and 16 percent age 5s.

Simple math shows the WDFW estimate is 2,697 fish, or about 33 percent higher than the TAC estimate, and once again, beyond the level of the interim recovery goal for the Snake fall chinook.

CRITFC's Stuart Ellis said the TAC number is still "somewhat preliminary," and could be subject to change if all parties agree. He said the committee has been trying harder to come up with timely run estimates for the Snake fish, and the process is getting better.

In previous years, it took TAC several years to get a final count, after sorting out harvest rates and dam count data of hatchery and wild fall chinook at Lower Granite, which is complicated by fish sporting different marking schemes used to identify their origins. -Bill Rudolph

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