In the past three decades, wild populations of bull trout have suffered a marked decline in Glacier National Park, historically one of the last best strongholds for the native Montana fish, which is listed as threatened under the Endangered Species Act. But even as invasive lake trout gnaw at the bull trout population, biologists believe that new conservation and management efforts can help preserve the keystone species.
An explosion of nonnative lake trout in Flathead Lake has decimated bull trout populations for decades, out-competing a species that would otherwise be a top iconic predator in its indigenous range. But the lake trout are steadily overwhelming bull trout habitat, even in historic strongholds like the Flathead Basin.
Of the 17 lakes that support bull trout on the west side of Glacier Park, 12 are connected to Flathead Lake, meaning they are accessible to lake trout, and nine have been invaded. Two more are at risk of invasion and a third has been invaded by brook trout.
In 2009, biologists with Glacier Park and the U.S. Geological Survey began an experimental project on Quartz Lake, which was still in its early stages of lake trout invasion, with the aim of reducing or eliminating lake trout. The fish were caught, radio-tagged and tracked to spawning areas in order to capture and remove spawning lake trout.
Overall, 91 percent of radio-tagged adult lake trout were removed from Quartz Lake during gill netting operations in 2009, and 44 percent were removed in 2010. All 11 radio-tagged lake trout tagged in 2011 and 2012 were caught and removed.
Now, biologists with both agencies are looking to continue the federal program on Quartz, located in the park’s remote northwest corner, and apply the same method of lake trout removal to Logging Lake, which was once among the most robust bull trout fisheries in the park.
With the upstream lakes of Glacier National Park invaded by lake trout, the ecological network that supports native species is becoming increasingly fragmented, said USGS fisheries biologist Clint Muhlfeld, who spearheaded the Quartz project.
“Bull trout populations in these upstream lakes are becoming functionally extinct, and we want to preserve all these different populations,” he said. “We want to maintain the genetic diversity of the species so it can continue to adapt, especially in the face of climate change. The question is, can we do anything about it? And we’ve answered that question. We’ve found that the results at Quartz have been promising.”
Many sites have already been lost — Kintla Lake, Bowman Lake, Coal Creek — while much of the habitat is badly fragmented.
Nonetheless, researchers believed it was critical to see what could be done to save the remaining strongholds.
On Dec. 19, Glacier National Park proposed to continue lake trout suppression on Quartz Lake and begin lake trout removal and bull trout conservation on Logging Lake. The park released an environmental assessment for the proposal, and launched a public comment period that runs through Jan. 22.
“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 states.
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.
“So in the span of 30 years the it has completely flipped,” Downs said.
In addition to removing lake trout from Logging Lake, the proposal also calls for trans-locating bull trout from Logging Lake to Grace Lake, an upstream body of water that is protected from invasion by a waterfall, which serves as a natural barrier. Downs said he hopes to preserve the population and promote the species’ genetic diversity.
“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.”
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 if the proposal is approved.
“There is nothing easy about it. But it is our feeling that Logging Lake has the greatest recovery potential,” Downs said. “But it is still going to be a challenge.”
Comment on the environmental assessment online at http://parkplanning.nps.gov/LoggingQuartz or mail comments to: Superintendent, Glacier National Park, Attention: Logging/Quartz EA, PO Box 128, West Glacier, Montana 59936.