On Saturday, May 7, 2022, two anglers targeting perch and bass in the Boulder Creek Arm of Lake Cascade caught an illegally stocked, 20-inch, nearly 3-pound mature male walleye. One of those two anglers was off-duty Regional Fisheries Biologist Mike Thomas, who positively identified the fish as a walleye. This is the second report of walleye in Lake Cascade in the past four years – with the first report back in 2018, when an angler reported catching a 19-inch Walleye near Crown Point.

Under Idaho code, it is illegal to possess, transport or release live fish or their eggs in Idaho without the permission of the director of Idaho Fish and Game. Fish and Game has never stocked walleye into the lake or any of its tributaries because their presence is incompatible with not only the world-class perch fishery in Lake Cascade, but also other fisheries downstream as far as Brownlee, Oxbow, and Hells Canyon reservoirs.

“We know that the only way walleye could have gotten into Lake Cascade is through one or more individuals illegally transplanting them there,” Regional Fisheries Manager Jordan Messner said.

Idaho has just a few walleye fisheries that were established by Fish and Game, all of which are in isolated reservoirs. Salmon Falls Creek Reservoir in south central Idaho is one example; no outlets from the reservoir exist that might allow walleye to escape to other waters. It is because of their potential threat to existing fisheries that walleye have not been more widely stocked in other Idaho waters.

What does this mean for the Lake Cascade fishery?

The short answer is that Fish and Game does not know what this means for the Lake Cascade fishery yet but will be investing resources to answer that question by first determining how abundant walleye are in the lake.

“Two reports over a four-year span means Walleye could very well be established in the lake, but the fact that we haven’t encountered them during extensive fish population surveys or angler surveys means they are likely not very abundant yet,” Thomas said. “Our fisheries program will be shifting gears over the coming weeks to try to determine the extent of their occurrence in the lake, and we’ll develop a game-plan for moving forward.”

The illegal introduction of walleye into Lake Cascade is particularly disheartening for fisheries managers. Idaho Fish and Game spent years rebuilding Cascade as a world-class perch fishery, which has become known as a destination for catching giant perch in recent years. Idaho Fish and Game is currently working with the University of Idaho on a graduate research project to determine how predation by smallmouth bass, northern pikeminnow, and large jumbo perch influences juvenile perch production.

“Throwing walleye into the mix certainly adds another layer of complexity to this research project, but it is a good time for us to learn more about their occurrence and what it may mean for the future of the Cascade fishery,” Thomas noted. 

The illegal stocking of walleye is a potential problem

Walleye are very efficient predators, and establishment of a walleye population in Lake Cascade could completely change the dynamics of that and other downstream fisheries.

Walleye are a popular sport fish among many anglers and are known for making great table fare, and Fish and Game is often asked why the agency is unwilling to provide a greater number of walleye fisheries in Idaho. In the case of Lake Cascade and many other Idaho waters, they simply do not have the prey bases needed to sustain quality walleye fisheries.

“It’s true that walleye commonly prey on yellow perch in their native range, and some anglers might look at a lake with a strong perch fishery, like Cascade, and question how Fish and Game can claim the prey base is not there,” Kozfkay said. “What those folks often fail to recognize is the lack of other forage fish that are common within the walleye’s native range, such as smelt, shad or various minnow species. Absent those forage fish in a system like Lake Cascade, a walleye’s diet is going to consist largely of other game fish species, which creates that potential threat to established and popular fisheries.”

The negative ramifications of this illegal stocking extends well beyond the shores of Lake Cascade. Fish and Game resources will be diverted away from other projects to expand fish sampling in Lake Cascade this year to see if more adult walleye are present and to determine whether reproduction is occurring within the lake.

Because of the illegal stocking and the threat walleye pose to Cascade’s and other downstream fisheries, Citizens Against Poaching (CAP) is offering a cash reward for information regarding this criminal case. Call the CAP hotline anytime at 1-800-632-5999 with information.

Idaho Fish and Game staff will continue providing updates on this case. In the meantime, we are asking that any anglers who encounter walleye in Lake Cascade, please harvest the fish (do not release) and report it to the Idaho Department of Fish and Game office in McCall (208) 634-8137.