Addition by subtraction



Scientists say the Confederated Salish Kootenai Tribal Council's recommendation to remove up to 75 percent of the adult population of lake trout in Flathead Lake is imperative to ensuring the survival of native fish throughout the Crown of the Continent region. In all, the decision could mean eliminating 142,466 fish.

"It isn't just about Flathead, it's about Glacier too," says ecologist Clint Muhlfeld. "There's a huge bottleneck of lake trout in Flathead Lake and they're moving upstream."

The migration is a problem because lake trout outcompete bull trout and can further threaten the endangered species. As it stands, there might not be enough bull trout in Glacier National Park to support a viable population.

"Lake trout radiated from Flathead Lake and caused a trophic cascade into the lake system throughout the Flathead Valley," Muhlfeld says. "They're in nine of 12 interconnected lakes in Glacier National Park."

Bull trout live in all 12 of those lakes, but they've become functionally extinct in eight of them since lake trout moved in. Glacier National Park comprises a third of bull trout's migratory habitat in the entire Columbia River Basin.

Muhlfeld works as a research aquatic ecologist for the Northern Rocky Mountain Science Center in the park and contributed to the Draft Environmental Impact Statement for Flathead Lake. To restore native bull and cutthroat trout populations and reduce invasive species numbers, he helped recommend four options for Flathead Lake in the EIS: no action, or the removal of 25, 50 or 75 percent of the lake trout.

CSKT Wildlife Division Manager Tom McDonald says the council's decision doesn't mean it will remove the full 75 percent of lake trout, but at least it has the option to do so.

"Like it or not, there's too many lake trout in Flathead," McDonald says. "The population is stunted, the fish are in poor condition and they're not growing or reproducing normally."

Reducing their numbers will mean healthier fisheries overall, but Muhlfeld says it's reached a critical stage if the goal is to have native fish. "The writing's on the wall," he says.

This story was updated Friday, Sept. 20, to correct the number of fish that could be removed.

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