Federal, state and tribal officials on Wednesday approved, though with qualifications, a plan to draw down north Idaho’s Lake Pend Oreille to a minimum control elevation of 2,051 this winter and, potentially, hold the reservoir at 2,055 during the winter of 2012-2013 to provide more spawning gravel for wild kokanee.
Control of the reservoir each winter is a tug of war between many needs – power demand, flood control, and the desire to manage the reservoir for the benefit of a severely depleted kokanee. The reservoir also provides storage to increase flows for chum salmon redds submerged far downstream in the lower Columbia River. The chum are listed as threatened under the Endangered Species Act.
The Pend Oreille River, which is held back by Albeni Falls Dam to buoy Lake Pend Oreille, eventually runs into the Columbia. The U.S. Army Corps of Engineers owns and operate the dam.
A “system operation request” regarding the plan was submitted to the Technical Management Team by the Idaho Department of Fish and Game and the U.S. Fish and Wildlife Service. TMT’s members mull federal hydro system operational changes suggested to benefit, particularly, ESA listed fish.
The IDFG has been trying, via predator control and reservoir management, to resurrect a kokanee population that up until the mid-1960s often provided annual harvests of more than 1 million fish. But because of a variety of factors, the number of kokanee in the lake plummeted. The harvest of kokanee has not been allowed since 2000 because of low numbers.
The USFWS also would like to see a surge in kokanee. 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 USFWS is charged with guiding recovery of bull trout.
The state of Idaho’s Russ Kiefer stressed Wednesday that TMT approval of the two-year plan would not tie its hands.
“Conditions could warrant a need to change the planned operation,” Kiefer said. Reviews of biological data are needed to assure that an anticipated rise in the adult female spawner population is really in the offing. With a higher reservoir elevation, the wild kokanee that spawn around the lake’s edges have access to more gravely habitat. The minimum control elevation were created to assure once eggs are laid in those gravel redds they will stay covered.
Environmental conditions, such as the available water supply in the Columbia-Snake system, could also affect decisions regarding the reservoir elevation next year.
“Data indicates that this kokanee population is recovering as we had hoped. Things look very positive out there,” Kiefer said.
The plan for a low year followed by a high year is designed “to set us up for next year when we think we can get a bigger biological benefit,” Kiefer said.
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. During the early part of this century a blossoming predator population, big lake trout in particular, nearly pushed the kokanee population over the edge.
In 2006 the state launched a predator control effort that has seemed to bring benefits. The spawning population last year was about 59,000, which was up from 40,000 females in 2009, which was an improvement over the 22,000-fish total in 2008, which was greater than record low of 5,000 in 2007.
The IDFG is predicting that about 86,000 females will spawn this year.
“And we expect to continue that upward trajectory,” said the IDFG’s Andy Dux. He said IDFG biologists believe the population will take even bigger jumps two and three years from now.
“An MCE of 2,055 in winter 2012-2013 providing the best spawning condition for this anticipated larger spawning population should contribute to achieving recovery goals sooner and help rebuild the weak coho cohort produced with the record low abundance of 2007,” the SOR submitted by the IDFG and USFWS says. The agencies say that tiny year class, which hatched out in early 2008, has indeed fared well because of helpful management actions.
The SOR stresses that the kokanee population still has a long ways to go before reaching desired levels. Dux said there is about 300,000 adult kokanee in the lake now, including wild males and females and fish produced by a hatchery program.
The IDFG has set goals of reaching sustainable population levels that would allow a kokanee harvest averaging 300,000 fish annually with catch rates of 1.5 fish per hour; a bull trout harvest fishery that allows a catch of at least 200 fish annually and a rainbow fishery with catch rate of 30 hours per fish and a harvest averaging 3,000 fish that are greater than 24 inches in length and of which 3 percent are over 30 pounds.
Those Gerrard rainbows have been a part of the problem, though not as big a part as the lake trout.
“Rainbow fishing is getting better. There’s more kokanee to eat,” Dux said. The rainbows and kokanee seemed to strike a good balance before the explosion in the lake trout. The IDFG would like to eventually revive the kokanee population and maintain what has long been a trophy rainbow fishery.
Dux told TMT members that it is not kokanee numbers alone that is driving the desire for the higher reservation level during the winter of 2012-2013. A University of Idaho graduate study is planned to develop a better understanding of the role lake level management play in kokanee egg-to-fry survival. A major component of this study involves incubating eggs in a variety of substrate types and lake depths, including elevations between 2,051 and 2055.
The study is intended to help guide Lake Pend Oreille management decisions in the future.
The lake’s minimum winter lake level for 2011-2012 will indeed be at 2,051 feet above mean sea level, according to the U.S. Army Corps of Engineers, Seattle District, Water Management Section.
The lake was at 2,060.7 feet as of midnight Sept. 26, and the Corps is continuing to draft with a goal of 2,056 feet by Oct. 15 and 2,052.5 feet by Oct. 31. The lake is expected to reach the 2,051 foot level during the first week of November.
Inflows are typically at their lowest levels in September and early October, but later fall rains and other considerations may require some outflow adjustments to reach the 2,051 foot lake level. The Corps expects to hold the lake at 2,051.0 – 2,051.5 feet through the end of kokanee spawning or Dec. 31, whichever comes first.
Lake Pend Oreille’s winter level is managed in cooperation with the USFWS, National Marine Fisheries Service and IDFG.
The Corps said a final determination on the IDFG-USFWS request to set the 2012-2013 winter lake level at 2,055 feet will not be made until next year.
The Corps operates Albeni Falls Dam as a multiple-purpose project, providing flood risk management, power generation, fish and wildlife conservation, navigation and recreation.
Information about Albeni Falls Dam and Lake Pend Oreille is available at: http://bit.ly/n0a0wx