Illegal yellow perch found in Island Park Reservoir threatens trout fishery

An angler ice fishing on Island Park Reservoir hooked a 5-inch yellow perch on Jan. 3 and reported the catch to the Citizens Against Poaching hotline, leading fish conservation officers to confirm the specimen on the ice. With no nearby yellow perch fisheries or waterbody connections that would explain its presence, Idaho Fish and Game concluded the fish had been illegally stocked, marking the first confirmed record of yellow perch in Island Park Reservoir.

Island Park Reservoir is managed as a hatchery-supported rainbow trout fishery. Trout and yellow perch compete for the same basic food web resources in reservoirs - notably zooplankton - and perch can, in many cases, out-compete trout and reduce trout survival and growth. Fisheries Manager Brett High framed the concern plainly: "We will continue to monitor fish populations in Island Park Reservoir and the impact perch may have on the fishery," he said. "Trout are Idaho's most popular species and feed on small crustaceans often referred to as zooplankton in Idaho's reservoirs. Perch are a popular sportfish as well and eat the same food. Sometimes they can co-exist but often perch out-compete trout leading to poor survival and growth. How this illegal introduction may affect ongoing collaborative efforts to improve water quality and the fishery in Island Park Reservoir is unknown and concerning."

Transporting live fish in Idaho without the required permits is prohibited. Illegal stocking poses ecological risks and can trigger costly restoration responses. Individuals responsible for introducing nonnative fish can be held financially liable for restoration costs, which Fish and Game warns could potentially reach into the hundreds of thousands of dollars, and in some cases may lead to felony charges.

Because immediate containment is critical to reduce establishment risk, Fish and Game is urging anglers to harvest any yellow perch encountered in Island Park Reservoir. There are currently no bag limits or size restrictions for yellow perch in the reservoir. Anyone who witnesses someone transporting live fish or otherwise violating wildlife laws is asked to call the Citizens Against Poaching hotline at 1-800-632-5999. Callers may remain anonymous and could be eligible for a reward.

For Kootenai County anglers and others who use Island Park Reservoir, the discovery underscores the vulnerability of managed fisheries to individual actions. The coming weeks will focus on monitoring, angler reporting, and any investigation into how the fish was introduced. Local anglers can help protect the trout fishery by harvesting perch, reporting suspicious activity promptly, and staying informed as Fish and Game monitors population changes and coordinates any necessary response.