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Central Washington's Sockeye Return Allows Lake Wenatchee Fishery; Fish Pass Seven Mainstem Dams
Posted on Friday, August 13, 2010 (PST)

This year's sockeye salmon "good news" extends to central Washington's Lake Wenatchee where sport fishers are taking aim at returning spawners for the third year in a row, which is an unprecedented streak.

 

Washington Department of Fish and Wildlife officials say production of salmonids in the Lake Wenatchee basin has declined in recent years. Despite population spurts in 2000, 2001 and 2008-2010, escapement goals (23,000 adult spawners to the lake) have been achieved only 12 times since 1978.

 

Fisheries are only allowed when the return exceeds that escapement goal. Recreational fisheries for sockeye occurred in Lake Wenatchee during the 1980s and early 1990s, and most recently during the 2001, 2004, 2008 and 2009 seasons.

 

"It's unusual" to have fisheries three years in a row," WDFW district biologist Art Viola said of the recent run of high sockeye returns to the Wenatchee and elsewhere. "Something went right."

 

The 2010 preseason forecast was for a return of 125,200 sockeye to the mouth of the Columbia River. That forecast included an estimated 14,300 to the Wenatchee subbasin (11 percent of the Columbia River basin run) and 110,300 (88 percent) to the Okanogan River watershed. The Snake River sockeye return for 2010 was forecasted at 600 fish. Daily and cumulative counts of sockeye at the Columbia River dams are available at www.nwp.usace.army.mil/op/fishdata/home.asp.

 

But by midweek week a total of 32,312 sockeye had been counted passing over Tumwater Canyon Dam on their way toward Lake Wenatchee, which is about 20 miles upstream. The fish climb over seven Columbia mainstem hydro projects and swim nearly 470 river miles before turning off into the Wenatchee River for the 53-mile homestretch to the lake.

 

This year's daily counts at Tumwater peaked July 19-23 with tallied that ranged from 2,271 to 3,339 (July 22) and have slowly tailed off since. Recent days' counts have been in the low 100s.

 

The sockeye returns have been on a three-year high. A record (at the time) return of 214,475 appeared at the mouth of the Columbia in 2008 and was followed by the return of 179,000 adults in 2009. The count so far this year at Bonneville Dam, the first hydro project the fish pass, was 386,497. Those counts are dwindling as well. Only two sockeye passed Bonneville Wednesday.

 

Based on harvest estimates of prior years, it is expected that a fishery in Lake Wenatchee would harvest about 16 percent of the Wenatchee River run. Therefore, a return of about 27,000 sockeye in the Wenatchee component is required before a sport fishery can be opened.

 

This year's Lake Wenatchee sockeye salmon fishery was opened Aug. 1-3, then reopened Aug. 7 "until further notice. The daily limit is two sockeye 12 inches in length or greater. Selective gear rules and a night closure are in effect. Bull trout, steelhead and chinook salmon must be released unharmed without removing the fish from the water."

 

Viola said the fishery was initially opened for only three days for a couple of reasons. A total of 27,000 sockeye had been counted passing over Tumwater Canyon Dam's fish ladder in the days leading up to the opener, meaning about 4,000 were available for harvest. At times in the past anglers have been able to harvest 1,000 or more fish per day.

 

"We knew we had enough fish for three days," Viola said. The three-day shutdown was imposed so that fishery managers could see how many more fish climbed over the dam and to accommodate an Aug. 6 statewide, unpaid "lay-off" day. WDFW personnel would not have been available that day to monitor the Lake Wenatchee fishery. The statewide, temporary layoffs are mandated by a law adopted by the 2010 Washington Legislature to help balance the state budget in the face of a revenue shortfall.

 

Viola believes that the lake is not producing as many sockeye smolts as it might. Most of the fish that emerge from the lake and head to the Pacific Ocean to mature are naturally produced, though about 200,000 hatchery smolts get their final rearing in net pens in the lake. The hatchery releases account for only about 2.5 percent of the sockeye spawners that return to the lake, according to the WDFW's Mike Tonseth.

 

Lake Wenatchee, which is deep and cold, is by nature "ultraoligotrophic, nitrogen limited and ranks in the lower range of trophic productivity for sockeye lakes," according WDFW study proposal submitted for funding in 2006 through the Northwest Power and Conservation Council's Columbia River Basin Fish and Wildlife Program. Oligotrophic means it has a deficiency in plant nutrients on which fish and other organisms feed. The lake is filled by the Little Wenatchee and White rivers, which are both glacier fed. The sockeye spawn in the rivers and the young fish rear to smolt stage in the lake.

 

"We really would like to do something for Lake Wenatchee" to improve its productivity, Viola said. But much mystery remains about what might be limiting production -- of spring chinook as well as sockeye -- in the lake. Little is known about the impact of predators such as bull trout and northern pikeminnow on the young salmon. All of the above mentioned fish are native to the lake. Bull trout and the spring chinook are protected under the Endangered Species Act; the sockeye and pikeminnow are not.

 

Likewise knowledge of the lake's potential carrying capacity is limited.

 

"We would like to see if there's something we can do" to improve the lot salmon and bull trout in the lake, Viola said. Improving sockeye smolt production could lead to more predictable fishing opportunities.

 

He said that the agency would again pursue funding for an evaluation of the lake's limiting factors and potential. The 2006 proposal was deemed fundable in part by the Independent Scientific Review Panel, which judges submittals for scientific merit. But the WDFW project did not make it into the final NPCC program budget.

 

The research proposal was intended to evaluate zooplankton biomass and production to establish the potential forage base and carrying capacity for juvenile sockeye, chinook salmon and bull trout and to quantify predation on resident and anadromous salmonids through diet analysis and bioenergetics modeling; and estimating predator abundance using mark-recapture and mobile hydroacoustic techniques. The purpose is to inform a lake management plan intended to maximize the number of smolts leaving the lake or available for recreational angling.

 

Potential solutions are predator removal and nutrient enhancement (fertilization).

 

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