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The Spokesman-Review Newspaper
Spokane, Washington  Est. May 19, 1883

Wilderness fish removal project aimed at helping Yellowstone waters

Beaver dams like this one will be breached to help spread the poison to ensure nonnative rainbow trout are killed. This view looks up Buffalo Creek toward Lookout Mountain. It is part of an effort to protect the area’s Yellowstone cutthroat trout population.  (BRETT FRENCH, Billings Gazette)
By Brett French Billings Gazette

Starting in August, the sounds of a helicopter could be reverberating in the Absaroka-Beartooth Wilderness just north of Yellowstone National Park.

The Park Service, Montana Department of Fish, Wildlife & Parks and Forest Service are cooperating on an extensive plan to remove nonnative rainbow trout from about 46 miles of the Buffalo Creek drainage and adjoining Hidden Lake in the wilderness. It is estimated the project could take five years. The plan is to be out of the woods by Sept. 15 each year to avoid intruding into the big game hunting season.

“This project is an essential piece in Yellowstone cutthroat trout conservation work,” Mike Thom, Gardiner District Ranger, said in a statement. “The Custer Gallatin National Forest and specifically portions of the Absaroka Beartooth Wilderness is poised to create secure cold water refugia and strongholds for the long-term sustainability and success of Yellowstone cutthroat trout. This is one of those prime opportunities working jointly with Montana Fish, Wildlife & Parks to benefit the natural characteristics of wilderness with native fish communities critical to our ecosystem.”


To remove the trout, the fish-killing chemical rotenone, which affects only gill breathing organisms, would be used. Removal projects using rotenone have been completed across the state in the past decade, but this is one of the largest and most logistically difficult.

Potassium permanganate is added downstream from the target area to disable the poison. Animals that drink from the water or eat dead fish are unlikely to be sickened as the amount of chemical is relatively small. Most of the dead fish are expected to sink into the water after dying.

In a similar fish removal project years ago in a Madison River tributary, the Forest Service reported the fishery recovered “to the pretreatment levels in three to four years” by planting fish of different sizes and incubating eggs in the stream.

The creek

The Buffalo Creek watershed arises deep in the Absaroka Mountains at an elevation of about 10,000 feet. The creek flows through conifer forests, wide mountain valleys choked with brush and a meadow scattered with beaver dams. The downstream end of the project area is more than 7,200 feet above sea level.

Rainbow trout were planted in the Buffalo Creek drainage in 1932. Since then, some of the trout have drifted downstream into Slough Creek in Yellowstone National Park. From there, the fish can interbreed with native Yellowstone cutthroat trout. To protect the native species, the agencies have cooperated on this new plan for fish removal.

“When it comes to rainbow trout mitigation, the Buffalo Creek project is the biggest and most-needed we have,” Todd Koel, Yellowstone’s lead fisheries biologist, told the Billings Gazette in 2021.


Most troubling to environmental groups is that a helicopter would be used to haul in gear to a staging area. Some of that gear would include boat motors, generators and motorized sprayers. Under the 1964 Wilderness Act, motorized use is frowned upon.

“Except as specifically provided for in this Act … and except as necessary to meet minimum requirements for the administration of the area for the purpose of this Act … no use of motor vehicles, motorized equipment or motorboats, no landing of aircraft, no other form of mechanical transport, and no structure or installation within any such area,” the Wilderness Act states.

Carrying everything in by pack mule was considered, but the cost was higher, according to Bob Gibson of Montana Fish, Wildlife & Parks’ Billings office. “It is roughly twice the price of using the helicopter. And would not allow us to use aerial application, resulting in a less effective treatment.”

To meet the Wilderness Act’s requirements, FWP and the Forest Service wilderness managers prepared a minimum requirements decision guide – a process used to identify, analyze and recommend management actions that are the minimum necessary for wilderness administration. In the document, posted online, the agency noted that removal of nonnative rainbow trout helps “preserve (improve) the natural quality of wilderness character that is currently degraded by the presence of a nonnative species.”

The analysis also noted that the negative effects would be short-term while the positive effects, once the work was done, would be long-term.

Food, gear

The intricacy of the operation is outlined in the Forest Service’s final environmental assessment.

Three remote field camps and the Buffalo Creek cabin would be used for housing workers. Forty-five pack stock would be used over four days to transport 6,000 pounds of food, gear and equipment to and from field camps.

“Helicopters would be used to transport 4,923 pounds of rotenone and treatment equipment to, within, and from the project area. Aerial transport of rotenone and treatment equipment in bear-proof cages is necessary to ensure that it is safe and secure from wildlife and on-site when crews arrive. This would require up to 15 landings on four separate days with a total of 12,446 pounds of gear and equipment airlifted. The total number of landings is not to exceed 45 over the five-year project duration.”

The copter would also be used to spray the 25 acres of open water with rotenone in the two large meadows on two separate days.

Restocking the river and adjoining Hidden Lake with Yellowstone cutthroat trout would take place after the rotenone treatment “using up to 18 total helicopter landings (six air drops and 12 physical landings). Stream stocking would be accomplished by utilizing hikers and pack stock, where feasible, to distribute fish to multiple locations from each helicopter landing.”

The rotenone treatment is expected to take up to 12 days each year, and would be repeated for three consecutive years. Fish stocking would take up to three days annually for up to five years.

At least 14 stream miles and 11 lake acres in the wilderness would not be restocked.

The estimated cost of the project is around $110,000, with some of the financing coming from grants and nonprofit donations, according to FWP’s Gibson. The costs will be split between the three agencies.


Creating the additional habitat for Yellowstone cutthroat trout, especially at an elevation where the waters should remain cooler as the climate warms, is projected to result in a 22% increase in secure habitat for the species in the Yellowstone River’s headwaters, said Mariah Leuschen-Lonergan, of the Custer Gallatin National Forest. Combined with other cutthroat restoration work on Soda Butte Creek, the Lamar River and Slough Creek, 352 miles of stream would be restored to cutthroat habitat, she added.

“The Buffalo Creek project is important for the long-term viability of the natural Yellowstone cutthroat trout in the Lamar River in Yellowstone National Park,” said Mike Ruggles, FWP’s regional supervisor in Billings.

According to the Forest Service EA, “Yellowstone cutthroat trout are better adapted to the cold and relatively sterile conditions in the watershed than rainbow trout, and the project would likely result in greater numbers and larger sizes than the fishery currently provides.”


The draft decision notices approving the project starts a 45-day Forest Service objection period and 30 days for FWP appeals.

Those who have previously submitted comments to the Forest Service are able to file written objections based on previously submitted comments, unless new information has arisen. Objections, including attachments, must be filed via email or by mail to:

By mail write to: Objection Reviewing Officer, USDA Forest Service, Northern Region, 26 Fort Missoula Road, Missoula, MT 59804.

Hand-delivery can be made by appointment, Monday – Friday, 8 a.m. to 4:30 p.m., excluding holidays, at USDA Forest Service, 26 Fort Missoula Road, Missoula, MT 59804.

FWP appeals may be addressed to: Director, Fish Wildlife & Parks, 1420 East 6th Ave.. Helena, MT 59620-0701.

Documents are available for review and download at: or