Glacier withdraws plan to put bull trout in Gunsight Lake

Glacier National Park and the U.S. Fish and Wildlife Service have withdrawn a plan to stock native bull trout into Gunsight Lake, an iconic high mountain lake in the park on the east side of the Continental Divide.

Biologists from both agencies used rotenone, a common fish poison, to rid the lake of non-native rainbow trout in 2023. Rotenone’s effects are temporary and a lake can be restocked shortly after treatment. The plan was to then restock the lake with native westslope cutthroat trout, whitefish and bull trout. The lake was seen as an ideal location for such a project because it is protected from upstream migration of lake trout and other species by natural waterfalls. That was considered phase II of the project.

Lake trout are a significant threat to bull trout, which are listed as threatened under the Endangered Species Act.

But Friends of the Wild Swan and the Council on Wildlife sued the agencies in 2024, claiming the plan to take bull trout from area waters east of the divide, raise some in hatcheries and then restock them in Gunsight violated the Endangered Species Act and the National Environmental Policy Act.

“We are glad to see this ill-conceived project withdrawn,” said Arlene Montgomery, Program Director for Friends of the Wild Swan in a release. “It was an experiment to create an isolated bull trout population without determining the true impacts to them —both in Gunsight Lake and in the streams where they were taking bull trout from.”

“The groups showed the environmental documents never answered key questions on how many bull trout it will take from streams, from what particular streams it will take them, at what hatchery it will propagate them, or how many it will introduce into Gunsight Lake to establish a genetically viable population. The lawsuit stopped that half-baked plan in its tracks,” the groups claimed in a release.

The Park Service, in court filings, conceded the plan needed more analysis.

The Park Service “identified substantial concerns regarding ... the analysis of the environmental effects of the second stage of the Gunsight Lake Project,” Kate Hammond, regional director of the Park Service noted in federal court documents filed April 9. “In particular, NPS has identified that  the Environmental Assessment analysis of the environmental effects of the second stage of the Gunsight Lake Project lacks sufficient discussion of the impacts of project activities on bull trout;  the NPS relied on a programmatic biological opinion that lacks sufficient consideration of effects to bull trout from Gunsight Lake Project activities, and (the U.S, Fish and Wildlife Service permit) does not adequately cover activities conducted under the Gunsight Lake Project.”

The Park Service, in turn, withdrew the project from consideration, at least for the time being. It plans on taking a closer look at the project in the future and could bring it back.

“Upon completion of the additional review, the NPS will determine whether to proceed with the project and issue new or revised NEPA and ESA analyses and a new decision, in coordination with FWS as appropriate,” Hammond surmised.

Glacier has done similar projects in the past, as has the state of Montana. On the west side of the divide, park biologists took bull trout from Logging Lake and transplanted them into Grace Lake.

The Logging Lake bull trout population was under severe threat from invasive lake trout. Lake trout are native species west of the divide, but not east of the divide.

Grace Lake, like Gunsight, is protected by a waterfall from lake trout.

In the Bob Marshall Wilderness and surrounding wildlands, the state of Montana several years ago removed non-native fish from 21 lakes using rotenone and re-stocked them with native cutthroat trout reared in hatcheries.

That project was largely seen as a conservation success story, although the state did not stock the lakes with bull trout.

In addition, Glacier has taken to netting out non-native lake trout in Quartz and Logging lakes in an ongoing effort to reduce lake trout numbers. The effort has been particularly successful in Quartz Lake, where bull trout numbers have rebounded after several years of netting and killing lake trout.