Non-native rainbow trout will be removed from Gunsight Lake and native fish species will be translocated to the lake. The action will remove the risk of hybridization to downstream native WCT, provide WCT and bull trout with habitat that is secure from the threats of hybridization and climate change, and support native trout genetics throughout the St. Mary River drainage.

Non-native rainbow trout will be removed from the lake using an EPA registered and approved fish toxicant, rotenone. While rotenone degrades naturally with sunlight and water movement, detoxification will be hastened with a neutralizing agent. The neutralizing agent, potassium permanganate, is widely used for the treatment of municipal drinking water and wastewater. Both rotenone and potassium permanganate will dissipate with no detectable long-term changes to water quality. Following the removal of the non-native rainbow trout, genetically pure WCT, bull trout, and mountain whitefish will be translocated into Gunsight Lake.

Project activities will begin late August or early September of 2023. The treatment area will be temporarily closed to the pubic during rotenone application and detoxification. The park anticipates closing Gunsight Pass Trail for approximately one week around the site preparation and rotenone treatment application period. The closure will extend from Reynolds Campground junction, and just east of Gunsight Pass. Gunsight Lake wilderness campground will close September 1, 2023, until spring of 2024.

From May 14 – June 15, 2023, the NPS solicited formal public comments on the EA. A summary of substantive comments and NPS responses is appended to the FONSI. For more detailed information on the project, the EA, FONSI, and a Minimum Requirements Analysis are available on the NPS Planning, Environment & Public Comment (PEPC) website.

Project funding is being provided by the NPS Natural Resources Preservation Program and the Glacier National Park Conservancy.