Several dead burbot, sealed in a plastic bag, were recently discovered along Highway 16 south of Emmett.
No edible portions had been removed from any of the fish.
Idaho Fish and Game staff is looking for information about where the fish came from and how they ended up in a roadside ditch hundreds of miles from their native waters.
Eel-like in appearance, burbot are a freshwater cod. In Idaho, burbot are found only in the Kootenai River drainage in the northern portion of the state. Because of population declines, Idaho burbot are fully protected, and no harvest is allowed. Efforts continue to rebuild native stocks.
In surrounding states, such as Wyoming, Montana and Utah, burbot populations are stable enough to allow legal harvest.
"It's quite possible that these fish were harvested legally, transported to Idaho, and wasted," Fish and Game fisheries manager Joe Kozfkay said. "Alternatively, someone may have imported live burbot into the state with the intention of releasing them. Both scenarios are concerning."
Illegal introductions of burbot in other states have had disastrous impacts on trout, salmon and other game fish species through fish egg consumption and juvenile fish predation by burbot. For this and other reasons, transporting and releasing any live fish in Idaho is prohibited unless specifically permitted by Fish and Game.
Anyone with information about the discarded burbot is encouraged to contact Fish and Game's Nampa office at 208-465-8465, or call the Citizens Against Poaching (CAP) hotline, at 1-800-632-5999, 24 hours a day. Callers may remain anonymous and may be eligible for a reward.