Glacier National Park, historically one of the last best strongholds for native bull trout, has seen its wild populations decimated by the explosion of invasive lake trout, reducing Montana’s aquatic darling to an imperiled icon and pushing the species toward the brink of extinction.
But biologists with Glacier Park and the U.S. Geological Survey have pioneered a new effort to suppress lake trout in remote backcountry lakes and reintroduce dwindling bull trout populations, with recent results showing strong evidence of success, and indicating that the efforts could be applied to other invaded habitats and broader ranges.
“New results are promising. The park is kind of spearheading these innovative and proactive ways to save bull trout,” Clint Muhlfeld, an aquatic biologist with the U.S. Geological Survey (USGS), said. “It’s been so rewarding to have our science apply to on-the-ground management and leading conservation efforts in Glacier.”
In 2009, biologists with Glacier Park and the USGS began an experimental project on Quartz Lake, located in the park’s remote northwest corner, where lake trout invasion was still in its early stages of invasion. The aim was to reduce or eliminating lake trout by gillnetting, a project that required a boat to be helicoptered in and all of the supplies to be hauled in by biologists and mules.
Muhlfeld and his team first located so-called “Judas fish,” captured and radio-tagged them, then tracked the fish to spawning areas in order to capture and remove the densest concentrations of spawning lake trout.
In five years, the project has shown strong evidence of success in reducing lake trout, and is hailed as one of the first successful projects of its kind and a leading example that lake trout suppression, once thought to be futile, is possible.
Now, biologists with both agencies have received approval to continue the federal program on Quartz, and apply a similar method of lake trout removal to Logging Lake, which was once among the most robust bull trout fisheries in the park, but where the species is now on the cusp of blinking out due to lake trout invasion.
A second element to the Logging Lake project, approved last month, involved translocation of bull trout – the first of its kind in the upper Columbia basin – where biologists moved 107 bull trout from Logging Lake to a safe haven called Grace Lake, an upstream body of water that is protected from lake trout invasion by a waterfall, which serves as a natural barrier.
“We captured as many of the remaining bull trout in Logging Lake as possible and literally put them on our backs in a bucket, hiked up a trail and released them in Grace Lake,” Muhlfeld said. “Now we’ll focus our efforts on suppressing that Lake Trout population in Logging.”
With the upstream lakes of Glacier National Park invaded by lake trout that radiated out of Flathead Lake, the ecological network that supports native species is becoming increasingly fragmented, said Muhlfeld.
With Glacier National Park proposing to continue lake trout suppression on Quartz Lake and begin lake trout removal and bull trout conservation on Logging Lake, Muhlfeld said there’s hope that the population can be recovered, albeit slowly and in the face of numerous challenges.
“Without action to reduce the lake trout population and conserve the remaining bull trout, the Logging Lake bull trout faces functional extinction in the near term,” the environmental assessment issued by Glacier Park states.
Earlier this month, the bull trout conservation projects were approved at both locations.
Chris Downs, fisheries biologist for Glacier National Park, is in charge of the management component of the project, and said logging lake was identified because “historically, it was one of the most robust bull trout fisheries in the park.”
Researchers first gillnetted Logging Lake in 1969 to assess bull trout populations and see if they could detect lake trout. In that study, 61 bull trout were captured and no lake trout.
Lake Trout first appeared in Logging Lake in 1984 and in 2000, 12 lake trout were caught and seven bull trout. In 2005, 25 lake trout were caught and seven bull trout.
In 2010, Downs gillnetted 42 lake trout but no bull trout, a grim decline, he said.
By trans-locating bull trout Downs said he hopes to preserve the population and promote the species’ genetic diversity, particularly because bull trout have adapted to the changing environments of specific tributaries over the course of thousands of years.
“The more genetic diversity you have the more they are able to adapt and persist in a changing environment, particularly in the face of climate change,” he said.
Downs said the project, which has already received funding through grants, will be challenging due to the geography. Still, given the success of the Quartz project, he is optimistic that he will see some measure of success on Logging Lake now that the proposal has been approved.