Alanna Mayham

(CN) — Conservationists sued the U.S. Forest Service on Wednesday over its plan to replace introduced rainbow trout in the Buffalo Creek drainage of Montana’s Absaroka-Beartooth Wilderness with Yellowstone cutthroat trout.

The lawsuit, filed by the nonprofit Wilderness Watch in Montana's federal court, accuses the agency of approving a plan that violates the Wilderness Act, which Congress implemented in 1964 to protect wilderness or areas “untrammeled by man” and preserve natural conditions.

The law has applied to the Absaroka-Beartooth Wilderness and its connective watersheds since 1978, enshrining protections for over 900,000 acres of remote, mountainous wilderness from the Custer and Gallatin National Forests. Those protections were later extended for another 23,750 acres from the Shoshone National Forest.

Before those protections, however, Wilderness Watch contends that human activities had already influenced the area in ways the government is planning to do again. The complaint states that, in 1932, Montana state officials introduced thousands of rainbow trout into Hidden Lake within Glacier National Park, which have since traveled into the Buffalo Fork Creek tributary to create what the Forest Service calls “a rainbow trout fishery.”

As a tributary to Slough Creek and the Lamar River in Yellowstone National Park, the Forest Service cites Buffalo Creek as the main source of non-native rainbow trout that are spreading downstream and hybridizing with native Yellowstone cutthroat trout — a species already impacted by predatory lake trout that were illegally introduced to Yellowstone Lake in the 1980s.

To mitigate unwanted hybridization and the further spread of rainbow trout, the Forest Service devised a plan to eradicate the species in Hidden Lake and 46 stream miles that extend to the wilderness area using rotenone — a piscicide that targets all gill-breathing organisms — for up to five years. Thereafter, the Forest Service intends to restock the waterways with unhybridized Yellowstone cutthroat trout in hopes of conserving the species. The project is set to begin in the summer of 2024.

When the Forest Service announced its Buffalo Creek Project in 2022, Gardiner District Ranger Mike Thom called the project a prime opportunity to work jointly with Montana Fish, Wildlife and Parks “to benefit the natural characteristics of wilderness with native fish communities critical to our ecosystem.”

And yet Wilderness Watch argues that the upper reaches of Buffalo Creek, including other mountainous lakes like Hidden Lake, are naturally fishless waters.

“Like in a significant portion of the streams and lakes in the Greater Yellowstone Ecosystem, the presence of trout in this watershed is a human contrivance, perpetuated in the pursuit of recreational sportfishing and borne of a subjective human value system that led fisheries and land managers to refer to fishless waters as ‘barren,’ despite their abundance of other aquatic life, and to stock them with desired fish species,” the group wrote in its complaint on Wednesday.

While the Forest Service touts the program as a “climate refugia,” Wilderness Watch accuses the agency of working at the behest of Montana Fish, Wildlife and Parks to treat the protected wilderness “as a repository for growing supplemental, artificial populations of fish to compensate for harms to the species from human activity elsewhere on the landscape.”

Representatives of both agencies did not immediately respond to requests for comment or an interview.

In addition to the use of rotenone — which will also be sprayed aerially over 25 acres of open water in two wetland meadows — Wilderness Watch took issue with other aspects of the project, including its use of helicopters to transport personnel and over 12,000 pounds of equipment, the Forest Service’s plans to erect a radio repeater and three remote field camps or the use of gas-powered pumps to distribute rotenone in lakes and wetlands.

“A plain reading of the Wilderness Act makes clear that the statutorily permissible scope of administrative work to safeguard untrammeled nature should not encompass the sort of work that requires a decade’s worth of habitat reengineering effort in reliance on modern industrial technology like helicopters, generators, gasoline pumps and piscicides,” Wilderness Watch writes.

In a statement on Wednesday, Wilderness Watch’s executive director George Nickas expressed how the protected wilderness “is no place for the massive use of poisons or helicopters, nor is it a place for managers to play God with species and habitat manipulation.”

“The Wilderness Act was passed precisely to rein in the propensity of managers to want to control nature,” Nickas added. “Our lawsuit seeks to preserve the wild character of the Wilderness and to let nature continue to evolve of its own free will.”

Wilderness Watch is represented by its staff attorney, Andrew Hursh.