Lake Pend Oreille walleye live mostly in the rivers and the northern portions of the lake although they regularly move, sometimes great distances, according to recent research by Idaho Fish And Game.
Results from a summer tracking study confirm that some walleye in Lake Pend Oreille and its rivers migrate many miles, while others tend to occupy a smaller area. Most of the fish can be found from the Pend Oreille River near Laclede to the Clark Fork River southeast of Clark Fork, and around Denton Slough, but tagged fish also move seasonally, according to the study.
Fish and Game monitored one walleye that was tagged in autumn 2017 below the Dover railroad bridge before migrating five months later to the Clark Fork River and then returning in July to the Pend Oreille River.
Other monitored walleye moved from the Clark Fork River to Denton Slough, where they stayed. A few fish moved south from the mouth of the Clark Fork River delta to Talache.
“Our summer tracking suggests that the Clark Fork River and delta, Denton Slough, the bridges around and below Sandpoint, and the deeper holes in the Pend Oreille River are areas most used by walleye during the summer,” fishery biologist Matthew Corsi said.
The fast growth rates of walleye in the system have produced some big fish, converting into walleye anglers a lot of fishermen who didn’t previously consider chasing the glassy-eyed predator.
“There are some trophy size walleye out there, and that’s appealing,” regional fishery manager Andy Dux said. “They are a fun fish. We get it.”
The department however sees the invasive species, which is a staple game fish in the Midwest where it is indigenous — it is Minnesota’s state fish — as a threat to the fragile, kokanee-based Lake Pend Oreille fishery that the department and many North Idaho volunteers helped bring back from the brink less than a decade ago.
“Walleye have the potential to undermine that,” Dux said.
The latest study is a facet in a research series that hopes to determine how much of the burgeoning walleye population is a result of spawning in the system, and what percentage comprises fish swimming into the system from Montana’s Noxon reservoir, where they were illegally introduced in the early 1990s, according to Fish and Game.
Located upstream of Lake Pend Oreille, Noxon Reservoir’s upper reaches near Thompson Falls dam are walleye spawning grounds.
“Fry naturally drift downstream after hatching, which is likely how they got into Lake Pend Oreille,” Corsi said.
Walleye began showing up at low densities in Lake Pend Oreille in the mid-2000s and since then populations — and fish size — have rapidly increased, according to Fish and Game.
Dux said his department’s research is meant to initially monitor walleye in the lake, find their hangouts and determine if the fish needs to be suppressed to maintain the viability of the lake’s kokanee, kamloops fishery.
“At this stage we’re just trying to understand as much as we can about walleye in the system,” he said.