Benefits of higher lake level in question

SANDPOINT — The ground around the proposition that holding Lake Pend Oreille at a higher elevation during winter benefits kokanee is starting to look a little shaky.

“It’s not as solid as we thought it was,” said Chip Corsi, the Idaho Department of Fish & Game’s Panhandle region manager.

The department has for years recommended a higher winter pool of 2,055 feet above sea level when spawning kokanee numbers are robust. The higher pool maximizes the amount of shoreline spawning habitat.

A higher winter pool also eases recreational access to the lake.

Questions about the higher lake level’s impact on kokanee emerged when Fish & Game asked the University of Idaho to scrutinize a long-term survival data set after seeing some confusing results.

Corsi said the error bounds in some population estimates were wide enough to undermine confidence in the figures. There are also “off-the-charts” survival data of kokanee during winters where the lake is drawn down to the lower elevation of 2,051 feet above sea level.

The department was used to seeing egg-to-fry survival rates of 10-12 percent

“Then more recently we had estimates that were spitting out numbers that were three or four times that,” said Corsi.

Muddying matters further is the fact that biologists are seeing kokanee spawning deeper in the lake. It’s also unclear what impact severe winter storms are having on spawning grounds when the lake is held at a higher elevation.

“The picture has gotten a lot fuzzier,” Corsi said.

The Pend Oreille Basin Commission, which advises the state on water quantity and quality issues, is meeting on Friday, Oct. 5 to discuss the issue. The meeting starts at 10 a.m. at the Panhandle Health District’s conference room at 322 Marion St.

 Fish & Game is slated to give a presentation on the new research.

The research is not expected to influence this winter’s lake level or the next winter because they are foregone conclusions. The state agreed to a higher pool during the 2012-13 winter and a lower pool during the 2013-14 winter.

Those elevations were set in an agreement with the Bonneville Power Administration as part of the agency’s flexible winter power operations plan on Lake Pend Oreille.

Corsi said the new research does not mean population estimates are wrong or that a higher winter lake level benefits kokanee survival, but it does call into question the veracity of that argument.

“It just means that we need to do some more work to understand whether in fact it’s right or whether it really isn’t a factor,” he said.