A National Park Wants to Use Rat Poison to Get Rid of a Fish They Brought In

Glacier National Park in Montana is a fisherman’s paradise. Hundreds of snow-fed lakes pepper the park, home to over 20 species of fish, including six kinds of trout. And, because it’s federal land, no license is required to cast a reel. But in a warming world, the National Park Service (NPS) is hoping to transform one of Glacier National Park’s coldest lakes into a refuge for a species of trout.

But it’s not as simple as translocating this species into the park. In order to create an environment for these fish, NPS first needs to get rid of the non-native trout that currently inhabit that lake.

The plan proposed by the park, which, if approved, would begin September 2023, recommends using a long-used pesticide and rat poison called rotenone. Despite being a naturally derived compound, it has been banned for use on rodents since 2005. While it is still a widely used fish toxin, or piscicide, as well as a widely used pesticide, researchers have unearthed strong epidemiological links with Parkinson’s Disease.

Like many lakes in the Western United States, Gunsight Lake was historically fishless. However, in the early 1900s, this picturesque body of water nestled between the towering peaks of Fusillade, Jackson, and Gunsight Mountains was artificially stocked with rainbow trout to improve recreational fishing opportunities. Since then, according to the scoping document, or the proposed plan, released by the NPS, the rainbow trout established a self-sustaining population in the lake. Through hybridization, i.e. the mixing of gene pools, they threaten the existence of native cutthroat trout within the same Saint Mary’s waterways (a listed species of concern for the state of Montana).

In order to help establish their population, the park is proposing to apply the fish toxicant via an inflatable boat and backpack sprayers with helicopters transporting materials. While rotenone naturally breaks down due to sunlight, to further limit potential contamination of the Saint Mary River and the rest of the Saint Mary water system, a neutralizing agent, likely potassium permanganate, would be used downstream. Once the non-native fish are eradicated, the park would then translocate (i.e. stock) the river with the cutthroat trout.

This is all to say, the park is proposing using poison to kill one fish in order to save another. And it’s not uncommon, either. In the Grand Canyon, the NPS is currently planning to use similar methods in order to save a native, endangered fish species in the park.

While environmentalists support the action being taken at the Grand Canyon, arguing that the case aims to protect a federally endangered species whose only habitat is that river, they insist that in the case of Glacier National Park, perhaps an alternative to poison should be considered.

Margaret Townsend, an attorney for the Center for Biological Diversity, a non-profit focused on conservation, urged the park to consider alternatives, something their scoping document did not discuss. “Because poison is indiscriminate, because it’d just kill everything in the lake, we’d prefer other options be explored in a situation like this one,” she said.

Townsend suggested a few alternatives: she cited the idea of electrofishing, a method which uses electricity in order to more effectively harvest undesirable fish. Another option to be explored, according to Townsend, is hosting a fishing derby, a contest that encourages anglers to catch as many fish as possible. She also suggested a hybrid model, perhaps one which utilizes both electrofishing, then tracking to ensure all of the fish are captured.

Chris Downs, a fisheries biologist for the park, argued that these methods take too long: “We’ve tried many of these other methods in the past and they haven’t been extremely effective,” he said. “They can take years and years and years, rotenone takes a week.”

However, Townsend argues that perhaps the poison should only be used in emergency situations. The main difference with the case in the Grand Canyon, is that the native species is listed as endangered and that lake is their only habitat in the world. “For the Grand Canyon, time is of the essence,” Townsend argued, “But for Glacier National Park, I’m not so sure.”

Beyond the issue of whether or not to poison these fish in order to protect another, Dana Johnson, a Staff Attorney for Wilderness Watch, a non-profit organization dedicated to protecting wilderness areas, argues that the way in which the park is planning to deploy the poison is a problem.

“The proposals run head-on into the Wilderness Act's "untrammeled" mandate, which says natural processes and conditions are supposed to dictate what type and how many species persist rather than intentional human control and manipulation,” Johnson said.

In short, Johnson argues that because most of Glacier National Park is recommended wilderness—it should be treated as such—and human interference should be limited.

It’s an ideology Townsend shares, and in her opinion, points to larger issues around conservation that need to be addressed. In her opinion, while the park is attempting to create a cold-water refuge for this species, it is a “Band-Aid solution,” one that does not address that waters are warming all over the West, and the world.

“Killing one species to save another is something we have to come to terms with,” Townsend said. “We’ve created these problems and then are trying to resolve them with a very quick fix, but there is so much more we could do to save cold water habitat.”

On the other hand, one could see this as the park attempting to take action and do their part in protecting wilderness in the face of a warming world. “We can’t control the changing climate,” Downs said, “we’re just trying to buy these fish more time to adapt.”