Kokanee no longer pack enough influence to keep the U.S. Corps of Engineers from fluctuating water levels at Lake Pend Oreille during winter.
Since 1996, the lake level behind Albeni Falls Dam has generally – not always – been kept above elevation 2,055 feet to avoid dewatering the eggs kokanee deposit in shoreline gravels until the fish hatch and can swim away.
But despite years of research, the Idaho Fish and Game Department has not been able to positively show that maintaining higher winter levels results in better production from wild kokanee eggs, said Jim Fredericks, department regional fisheries manager.
That means the lake levels are likely to fluctuate between elevations of 2,055 and the minimum level of 2,051 feet this winter depending on weather and power demands.
“It’s not an over-and-done-with issue,” Fredericks said. “We still have research looking at kokanee survival from a different angle to try to come up with more precise numbers on the impacts (of dewatering shoreline kokanee spawning beds).
“Also, there are indications that some wild kokanee spawn deeper than we’ve estimated, but we don’t have a handle on how much.”
The Idaho Conservation League has filed a court challenge to the Bonneville Power Administration’s flexible winter level operation plan. The action suit isn’t based on the impacts to kokanee, but rather the role hydropower operations have in erosion.
About 15 acres of the Clark Fork Delta are lost to erosion each year because of artificial lake level fluctuations, ICL says in a media release announcing the court action.
The Clark Fork Delta at the northeast end of Lake Pend Oreille is important to fisheries and other wildlife, especially waterfowl, Fredericks said.
Idaho Fish and Game officials signed an agreement to hold off on challenging the impacts of fluctuating lake levels in return for funding to mitigate damage Albeni Falls Dam operation has on the delta and its array of islands.
“Even since 1996, there have been instances when the lake was drawn down during winter,” Fredericks said. “Lakeshore owners have seen the 2,051 level in recent years, and so have the kokanee.”
Meanwhile, netting operations and a bounty on invasive and predatory lake trout helped revive kokanee from a near crash.
Anglers this year enjoyed the first kokanee fishing season on the lake since the fishery was closed in 1999.
“We had a good take of kokanee eggs at Granite Creek for the hatchery last year and this year should be another good one,” Fredericks said.
But in a normal year, “the vast majority of the lake’s kokanee production comes from wild kokanee that spawn in the shoreline gravels,” he said.
September surveys indicate the lake’s kokanee population is about 20 percent higher this year for all age classes of kokanee. Overall kokanee abundance this year is the highest since the ’90s, said Andy Dux, lead research biologist for the Lake Pend Oreille project.
Through October 2013, the netting program has removed more than 8,100 lake trout from Pend Oreille. The Angler Incentive Program has accounted for an additional 3,147 lake trout removed this year. Since 2006, the two programs have removed more than 162,000 lake trout.