Wilderness Watch says that the state's practice of flying over wilderness areas and dropping hatchery fish into lakes and rivers is spreading foreign pollutants into the waterways. The group is suing under the Clean Water Act, focusing on stocking in high mountain lakes in Klamath, Humboldt and Lake Counties.
George Nickas with Wilderness Watch says introducing these fish can be detrimental to native fish and amphibians.
NICKAS: "There can be all kinds of pathogens from the fish hatcheries, other things that can be in water, when it's dumped in there. It could be other aquatic organisms, it could be diseases."
Nickas adds that many high mountain lakes historically have been fishless, and dropping in fish can upset the natural ecosystem.
The department says it has been monitoring high mountain lakes to study the impact of stocking fish.