A surging walleye population in Lake Pend Oreille has biologists, and some anglers, worried.

“Walleye pose a predation threat to the kokanee that we have been working so hard to sustain,” said Andy Dux, Idaho Fish and Game’s regional fisheries manager in Coeur d’Alene.

IDFG is so concerned about the illegally introduced predatory fish that they started a three-week gillnetting program. The trial run, which is in its second week, will determine the feasibility and effectiveness of a wider suppression effort.

That has angered some anglers who love catching the fish and believe the fishery should be left alone.

“From my experience the lake is at its prime for all species,” said Than Widner in an email. “The gillnetting is not only killing walleye, it is killing bass, perch, crappie, pike, rainbow, and lake trout.”

Widner, who has fished at Lake Pend Oreille for 20 years said he doesn’t favor one species over the other. But he does think IDFG is acting prematurely.

“I am opposed to this because there is not a problem,” he said. “They are making this adjustment on a assumption that there will be a problem.”

Many anglers love walleye because of how they taste.

“There is not a better tasting fish,” said Doug Schroeder, the president of the Spokane Walleye Club. “As far as the food fish go they’re outstanding.”

Although Schroeder emphasized that he’s not familiar enough with the Pend Oreille fishery to speak specifically about what he thinks should happen, he said generally he’d like to see stronger regional walleye fisheries.

Dux recognized the issue is a sensitive one. But he emphasized that no final decisions have been made.

“A lot of folks have jumped to the conclusion that we’ve started a walleye suppression program like we did with lake trout,” he said.

That’s not true, he said. But what is true is that the lake’s walleye population has only grown over the years. And, recent surveys indicate the fish are eating more and more kokanee.

“It appear that the walleye population is roughly doubling every three years,” Dux said.

That’s bad news for the lake’s kokanee population.

A group of outside walleye experts agreed. After reviewing data on the fishery the experts warned IDFG that they had a brewing problem.

“The group of experts unanimously agreed that we should be very concerned about the threat the walleye pose to the Lake Pend Oreille fishery,” Dux said.

Lake Pend Oreille’s kokanee population is just now rebounding after being decimated by lake trout. For that reason Dux said biologists are taking any threat to the population seriously.

Since 2006 the Idaho Department of Fish and Game has suppressed lake trout populations in the lake which has allowed the kokanee fishery to rebound after reaching historically low levels.

“That’s why we’re ramping up our monitoring efforts and our research efforts,” Dux said of walleye. “What we’ve learned so far is that walleyes are in fact eating kokanee.”

Gillnet surveys in 2011 and 2014 confirmed that walleyes were quickly expanding their presence. Walleye abundance nearly doubled in three years in waters from the Clark Fork delta, across Lake Pend Oreille, and down the Pend Oreille River.

In 2017, IDFG caught 199 walleyes per net. That’s compared to 105 in 2014 and 57 in 2011.

Over the past dozen years walleyes made their way down the Clark Fork River and infiltrated Lake Pend Oreille. The fish are prized by many anglers.

“Within the last five or six years we’ve really seen walleye increase in abundance,” Dux said.

Kokanee are the backbone of the Pend Oreille fishery. Because the fish are the preferred meal for many predatory fish any large change in their population can have a widespread impact.

“As kokanee go so does the Pend Oreille fishery,” Dux said.

In addition to finding more walleye, Dux said they’re finding healthier and older walleye.

“All these things point to a population that is becoming more firmly established and increasing in abundance,” he said.

There is no bag limit for walleye and IDFG does not allow catch-and-release tournaments, only harvest tournaments.

James Mullen is a charter boat captain and a board member on the Lake Pend Oreille Idaho club. He worries that if walleye eat too many kokanee, the rainbow fishery will collapse, just as it did with lake trout.

The club’s annual derby, which started Saturday, will feature a walleye division. Anglers who catch, and kill, the largest walleyes will win cash. Mullen said IDFG requested the division be added.

“You can go anywhere to catch a walleye,” he said. “Lake Pend Oreille is a trophy rainbow fishery as far as we’re concerned.”

After the three-week suppression trial period ends Dux said the agency will consider its next steps. If the walleye population continues to grow and eat kokanee, he said wider suppression efforts are possible.

“Basically all the signals are that we need to be proactive and learn as much as we can in a hurry,” he said. “If we’re going to have an opportunity to keep things in check the best opportunity to do that is in the early stages.”