Monday January 19, 2026
Prism News —
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.”