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Lake Pend Oreille Operations Set In Continued Effort To Revive Kokanee, Aid Bull Trout
Posted on Friday, October 22, 2010 (PST)

North Idaho’s Lake Pend Oreille will be drawn down by Nov. 15 and held at 2,055 feet elevation, which is just a foot below its maximum wintertime flood control elevation, in order to provide access to as much spawning gravel as possible for what is believed to be a reviving population of kokanee.


The system operational request from the Idaho Department of Fish and Game and the U.S. Fish and Wildlife Service moved forward following a discussion at a special Oct. 15 of the Technical Management Team. The USFWS, the state of Idaho and the U.S. Army Corps of Engineers supported the recommendation. The Corps operates Albeni Falls Dam, which controls Lake Pend Oreille’s elevation.


The TMT’s federal, state and tribal membership mulls day to day operations of Federal Columbia River Power System operations that have the potential to improve the survival of fish such as Columbia and Snake river salmon and steelhead stocks that are listed under the Endangered Species Act. The Lake Pend Oreille kokanee are not listed or native to the region but have long been considered an important food source for bull trout, which do have ESA protection.


The IDFG would also like to see a flagging kokanee population in the lake restored to levels that would support fisheries. Up until the mid-1960s annual harvests of more than 1 million kokanee were common. But because of a variety of factors, the number of kokanee in the lake has plummeted. The harvest of kokanee has not been allowed since 2000 because of low numbers.


The state of Montana, NOAA Fisheries Service, Bureau of Reclamation and Bonneville Power Administration representatives at the TMT meeting did not object to the SOR.


But both NOAA Fisheries and BPA officials expressed concerns about what will be an early drawdown of the lake, which was at 2.057.71 feet, as measured at the Hope gauge, at 8 a.m. Oct. 15. The lake is one of the few stores of water that can be called on later in the fall and winter for other uses, such as for the generation of electricity during higher demand periods and to maintain flows that cover chum salmon eggs far down stream below the lower Columbia River’s Bonneville Dam.


Chum, which are ESA listed, are expected to begin spawning in late October or early November. Once chum redds are established, operations aim to keep those egg nests covered through the winter. That often requires drawing water from reservoirs upstream. The lake fills the Pend Oreille River, which empties into the upper Columbia.


Freeing nearly two feet of water from the large lake now means less water will be available later, depending on the weather of course, for downstream uses. Other than Canadian reservoirs, the only downstream storage is Lake Roosevelt behind Grand Coulee Dam on the mid-Columbia in central Washington. Lake Roosevelt is within a foot and a half of full pool.


BPA’s Tony Norris cautioned that losing water now could have the ripple effect of forcing more water withdrawals from Grand Coulee in winter to maintain chum flows and threaten operators ability to hit the April 10 upper flood control rule curve target for that reservoir. Hitting that upper rule curve means there is as much water in storage as possible to help augment flows in spring for salmon and steelhead migrants.


Given the fact there were no objections to the operation, the Corps’ Steve Barton said Lake Pend Oreille would be drawn down to 2055 feet by Nov. 15 and that level be maintained within a half-foot range through the end of kokanee spawning or Dec. 31, which ever comes first.


The adult kokanee in Lake Pend Oreille are at low levels. Research indicates that three decades of annual deep drawdowns during the winter months from the 1970s well into the 1990s were the primary factors contributing to the large declines in kokanee abundance, the SOR says. The drawdowns limited the access to spawning areas. Operations were implemented beginning in the late 1990s to better accommodate kokanee spawning. But by than another kokanee nemesis had became a larger factor.


“That’s right about the time we had the lake trout population take off,” said Andy Dux, IDFG fishery research biologist.


The beleaguered landlocked salmon population then became victim of the huge lake trout whose population in the lake peaked early in the new millennium. They and trophy size Gerrard rainbow trout teamed up to nearly wipe out the 1-2-year old kokanee classes and thus prevent them from growing into spawning age.


Since 2000 predation has been considered the primary factor limiting the kokanee population, surpassing spawning habitat limitations.


The state in 2006 triggered a two-pronged attack on the lake trout and a one-pronged attack on the Gerrard rainbows. Beginning in May of that year a $15 bounty was offered for lake trout of any size and any rainbow 13 inches or larger. And commercial fishers were hired to focus on the lake trout.


State officials feel the predator removal effort is paying rewards. Through May of this year 101,000 lake trout had been removed from the lake since 2006, half by anglers and half by commercial netting. Anglers initially led the charge but more recently the netting is producing the largest share of the catch. The fish are harder to catch, and the commercial fishers have been able to zero in on lake trout spawning areas and places where younger lake trout are now known to congregate, Dux said.


“There are fewer lake trout out there,” Dux said. Additionally rewards have been collected for more than 26,500 big rainbows.


The effort seems to be helping. A spawning population of 40,000 females was expected last year, which was an improvement over the 22,000-fish total in 2008 and the record low of 5,000 in 2007. This year, an estimated 59,000 female kokanee are expected to spawn this fall.


“We’re taking some encouragement,” Dux said of the recent trend. The expected spawning class is still small but is an improvement.


“We’ve still got a long ways to go,” he said.


The lake has during the past two winters been drawn down to 2,051, which is at the low end of the range developed as part of the kokanee restoration strategy. If the only management consideration was the resident fish, the lake would be drawn down to the minimum once every four years. That limits the spawning area for kokanee but allows wave action to clean sediment from gravels that are favored nesting sites.


As a result of 2,051-foot lake levels in 2008 and 2009 there is higher quality spawning habitat for kokanee this year, said Russ Kiefer, who represents Idaho at TMT meetings.


“Thus, proving the greatest opportunity for high egg-to-fry survival this year is important for taking advantage of both improved spawner abundance and survival rates that should allow a higher proportion of fry to reach maturity,” the SOR says.


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