IFG keeps eye on kokanee, walleye

PONDERAY — Kokanee abundance in Lake Pend Oreille remains high, although they are not the hardiest landlocked salmon roaming the depths of the lake lately.

“There’s a lot of great fishing opportunity on the lake right now. But because the kokanee population has been abundant, the kokanee have been very small kokanee. Fishing hasn’t been all that great the last couple of years,” Matt Corsi, a principal fisheries research biologist, told a capacity crowd at the Idaho Department of Fish & Game’s State of the Lake presentation at the Ponderay Event Center on Thursday.

Corsi said the lake is flush with age 1 fish, although there were fewer age 2 fish in 2018 than there was in 2017. The picture gets less rosy when it comes to age 3-5 fish, which make up the fishery and go on to spawn.

“We’ve been seeing some declines in this adult kokanee abundance in the last three years here,” Corsi said. “It is certainly a signal that the kokanee population is changing right now and it’s something we’re keeping our eyes on.”

The record abundance of age 1 fish may be what’s keeping kokanee growth rates low, according to Fish & Game.

“When we’ve got a lot of cows out in that pasture we’re seeing some lower growth rates,” Corsi said.

Kokanee egg take, meanwhile, is down for the second consecutive year. Some 9 million eggs were collected in 2016 compared to 6 million eggs in 2018. Approximately 4.5 million kokanee fry are expected to be released this spring. However, natural production of kokanee is increasing, raising questions whether the hatchery program should dialed back, Corsi said.

What’s emerging as a threat for kokanee are walleye, the population of which roughly doubles every three years.

“They’re not so rare anymore,” said Andy Dux, Fish & Game’s Panhandle region fisheries manager.

Of particular concern is the diet of walleye. A diet analysis of conducted in 2016 showed a third of the walleye had identifiable remnants of kokanee and it’s suspected kokanee made up portions of the stomach contents which couldn’t be conclusively identified.

As a result, the state is rolling out an experimental angler incentive program on the Pend Oreille. Fifty fish have been microscopically tagged and anglers who catch one of can win $1,000. There will also be 10 $100 drawings each month for anglers who submit harvested walleye which aren’t tagged.

The lake trout suppression program to ease the strain on kokanee also remains effective, having reduced the lake’s population by 70 percent since the program’s introduction in 2006. Most of that effort has involved netting, although Dux said angler harvest is proving crucial because they are catching intermediate size class fish missed by netting operations.

The lake’s trophy rainbow trout population is also ascendant.

“The good news is that the size structure of these fish has been steadily been going up,” Dux said.

One fourth of the rainbows caught in 2018 were 25 inches or longer and rainbows caught now are bigger than the fish caught in 2014. Fisheries biologists have done modeling which links kokanee abundance to the size of rainbow trout.

“Every time there’s an additional 3 million kokanee in the population, it means one additional inch of rainbow trout growth per year,” Dux said.

Keith Kinnaird can be reached by email at kkinnaird@bonnercountydailybee.com and follow him on Twitter @KeithDailyBee.