Glacier Park project would help preserve native trout

April 7, 2019

People presumably acting with good intentions stocked once-fishless Camas Lake and Lake Evangeline in Glacier National Park in the 1920s and 1930s with non-native Yellowstone cutthroat trout.

Nearly a century later, trout species native to the park and its environs face a variety of threats, ranging from hybridization with or competition from non-native species to the impacts of climate change on water temperature and spawning beds.

Now, Glacier National Park stands poised to initiate a project that could boost the prospects for native westslope cutthroat trout and bull trout - both inside the park and in drainages of the North Fork of the Flathead River.

The project will hinge on the use of rotenone, a fish toxicant, to rid Camas Lake, Lake Evangeline and a stretch of Camas Creek above Arrow Lake of non-native Yellowstone cutthroat trout.

Eventually, native westslope cutthroat trout and bull trout would be added to the lakes and creek.

Chris Downs, fishery biologist for Glacier National Park, said the park service would partner with the Montana Department of Fish, Wildlife and Parks to administer the rotenone.

“They’re the experts in this technique,” Downs said during an interview Thursday. “We partner with them to share resources and to learn.”

Fish, Wildlife and Parks tackled in 2004 an ambitious 10-year project that used rotenone to re-establish westslope cutthroat trout populations in 21 remote, high-mountain lakes. Although controversial when first proposed, the South Fork Flathead Westslope Cutthroat Trout Conservation Program later won over many of its skeptics.

Glacier National Park said rotenone, a plant-derived toxin, “is proposed for this project because, compared with mechanical means of removing fish (e.g. netting, trapping, electro-fishing and angling), it would remove non-native fish in a period of days as opposed to years, and would achieve a complete removal.”

The toxicant interferes with cellular respiration of aquatic gilled organisms and is highly toxic to fish.

During application, many fish killed by the rotenone would remain submerged. Fish that might bob to the surface would be collected and either sunk or removed from the site to avoid attracting bears and other wildlife.

Downs said birds, bears or other animals that might eat the dead fish would not be affected by the toxicant.

The rotenone would likely kill some larvae of amphibian species. As envisioned, though, the project would be implemented in late summer, early fall, when “many amphibian species have developed into terrestrial adults,” according to the project’s environmental assessment.

Although rotenone provides a comparatively rapid method for removing the non-native fish, replacing them with native westslope cutthroat and bull trout would require time.

Generally speaking, the project staff would not scoop up the native fish from nearby “donor populations” in places like Starvation Creek, Ford Creek and Avalanche Lake and transport them directly to Camas Lake and Lake Evangeline.

Instead, the fish collected would be spawned and their fertilized eggs would be raised in a hatchery outside the park. That approach would maximize the potential for survival of the eggs and also allow for genetic testing of the donor fish, Downs said.

“The hatchery-raised westslope cutthroat trout and bull trout would remain in the hatchery until they are approximately two years of age, after which they would be transported by helicopter or pack stock to Camas Lake and/or Lake Evangeline,” according to the environmental assessment.

Downs said the initial focus would be establishing westslope cutthroat in the lakes, followed by bull trout.

Thus, even though the effort to preserve native trout in the Upper Camas Drainage would be comparatively fast-tracked, using rotenone to speed up the process, it would still likely require five to 10 years to bring to fruition, Downs said.

There is some urgency to act, he said.

The survival of pure-strain native westslope cutthroat is threatened by hybridization with rainbow trout, he said.

“The hybridization is progressing,” Downs said. “We are finding it further up the drainage.”

Threats to bull trout include competition from non-native lake trout, as well as sedimentation of streambeds and rising water temperatures tied to climate change.

“Now is the time, essentially,” he said, noting that Camas Lake and Lake Evangeline could provide cold-water refuges for native westslope cutthroat and bull trout that would be safe from hybridization.

“Several waterfalls between Camas Lake and downstream Arrow Lake provide natural barriers to upstream fish migration, preventing the invasion or re-invasion of non-native fish,” the environmental assessment reports.

Downs acknowledged that fisheries biologists in years past have intervened in natural processes in ways that later proved to have unintended negative consequences.

He said he believes the proposed interventions in the Upper Camas Drainage in Glacier National Park have been carefully designed to avoid the mistakes of years past. He said there would not be threats to fisheries downstream of the lakes slated for treatment and that Fish, Wildlife and Parks has demonstrated expertise in the use of fish toxicants, employing them effectively and safely.

“There’s always a chance something could go wrong, but as I look at it, it’s low risk, high reward,” he said.

The environmental assessment for the Westslope Cutthroat and Bull Trout Preservation in the Upper Camas Drainage project can be reviewed at parkplanning.nps.gov/UpperCamas

Comments about the environmental assessment are due April 17.

Reporter Duncan Adams may be reached at dadams@dailyinterlake.com or 758-4407.