Glacier National Park released an environmental assessment Friday for a proposal to kill off non-native fish in a remote area. Biologists say that could help fortify native species against the threats of climate change, invasive species and habitat loss.
The assessment says poisoning Yellowstone cutthroat trout in remote park lakes and replacing them with native species won’t cause any lasting impact to recreation, ecosystems or wildlife.
Glacier National Park fisheries program manager Chris Downs says it’s part of a multifaceted strategy to help fish like the west slope cutthroat and bull trout survive.
"We’re trying what we can do below fish barriers to try and benefit native fish by removing non-native fish. But that’s a big task. And this is an opportunity to sort of hedge our bets about the success or failure of those efforts downstream by establishing secure populations that don’t need management."
If approved, managers will treat Camas Lake, Lake Evangeline and Camas Creek – all above Arrow Lake in the upper Camas drainage in the heart of the park – with rotenone, a toxicant that kills fish.
Downs says the piscicide process will only take a few days. Rotenone breaks down naturally, and they’ll speed up that process by detoxifying the water to make sure it doesn’t pose a problem downstream.
After officials have fished out as many dead trout as they can, they’ll begin reintroducing westslope cutthroat, bull trout and native sculpin.
Non-native fish won’t be able to get past a waterfall into these populations upstream. But the new, native fish in the lakes will be able to swim downstream at will.
"It’s like a one-and-done thing. You’ve essentially accomplished the objective of providing additional security for that species," Downs says.
The historic range of native westslope cutthroat and bull trout has decreased substantially – and both are “species of concern” in Montana. In Glacier, the federal government enthusiastically stocked parts of the park with non-native fish to satisfy anglers for decades, starting in the early 1900s. But the spread of those species and other invasives put pressure on native fish from overcrowding, habitat loss and hybridization.
Now, there’s another threat too: climate change.
"We’re looking at warmer water temperatures, hotter drier summers, potential increases in wildland fire, potentially getting more of our precipitation in the fall and winter in terms of rain. And if those things increase over time, it’s gonna be hard for these critters to adapt in the short-term when they’re facing additional pressures from non-native fish," Downs says.
Historically, no fish lived in these upper Camas lakes. But as part of that stocking process the Park Service introduced Yellowstone cutthroat – a non-native – nearly a century ago in the 1920s and 30s. Downs says in that time, the introduced fish have already impacted the zooplankton and amphibian communities of the lakes – so there shouldn’t be any new ecological impacts.
State officials have conducted similar projects on dozens of lakes in the Bob Marshall Wilderness in years past. Downs says these native fish have cultural importance to indigenous groups in the area, and there’s also an economic benefit.
"You know in the summertime, when you’re at the airport you can see almost as many rod cases as suitcases. People aren’t coming here to catch rainbow trout and brown trout. They’re coming here to catch our native fish. This is one of the best places where you can do that."
Downs says a lack of native fish can cause an ecological ripple effect, too.
"That relationship between, not only fish-to-fish, but fish to terrestrial ecosystems, I mean we have some obligate piscivores, we have ospreys, we have loons, things that eat our native fish. And if they have to adapt to trying to eat a deep-dwelling lake trout, that’s a whole different situation. That’s the mission of what we’re here to try and do, is try and conserve the native resources unimpaired for future generations."
If approved, the project will likely begin in the fall – after peak tourist season. Public comment opened on Friday and goes until April 17.