Illegally introduced Yellow Perch caught in Island Park Reservoir

An angler ice fishing for trout on Island Park Reservoir on January 3, 2026 unexpectedly hooked into a 5-inch-long Yellow Perch, a species that does not belong in the reservoir. The angler retained the fish and immediately reported the catch to the Citizens Against Poaching hotline. 

Conservation Officers with Idaho Fish and Game met the angler on the ice and confirmed that it was indeed a Yellow Perch. With no connecting Yellow Perch fisheries in the area, it was determined that the fish was illegally stocked and is the first-ever confirmed report of a Yellow Perch in Island Park Reservoir. Island Park Reservoir is managed as a hatchery supported Rainbow Trout fishery.  

Transporting live fish in Idaho is illegal without the required permits. Illegal stocking of fish into a lake or reservoir can cause serious ecological consequences to Idaho's fishery resources. Individuals illegally transplanting or introducing fish where they don’t belong can be held legally responsible for the financial costs to restore the fishery to its prior condition. Restoration efforts could potentially total in the hundreds of thousands of dollars and can result in a possible felony charge.

“We will continue to monitor fish populations in Island Park Reservoir and the impact perch may have on the fishery,” says Fisheries Manager Brett High. “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.”

Fish and Game is encouraging anglers to harvest all Yellow Perch they come across in Island Park Reservoir. There is no bag-limit or size restrictions. 

 Conservation Officers are responsible for patrolling a tremendous amount of area, and can’t be everywhere at once. If you witness someone transporting live fish, or any wildlife violation, please call the Citizens Against Poaching hotline at 1-800-632-5999. Callers may remain anonymous, and they may be eligible for a reward.