Montana Fish, Wildlife and Parks (FWP) will begin sinking nets into Swan Lake to snare thousands of lake trout later this month. The experimental netting project—the state's first and among only eight underway around the West—is designed to contain the flourishing non-native species that threatens native bull trout populations.
"This is testing whether we can suppress a particular species," says Jim Vashro, FWP's Region 1 fisheries manager. "The end result in three years will hopefully give us a better idea of what the lake trout population looks like, what their relationship is with the other fish species in the lake, and whether we can suppress them through netting."
FWP approved the three-year project last week after two years of research and sampling. In 2008, biologists estimated that 8,800 lake trout live in Swan Lake, and 3,784 of them were removed.
Vashro says the number of lake trout the agency will catch and kill will vary from year to year. "But we've caught nearly 4,000 in the past," he says. "I would hope that we can exceed that."
During last year's sampling, 240 bull trout were netted, and about half were safely released. Vashro says FWP will minimize bull trout by-catch by netting in deeper parts of the lake and while they spawn in the tributary system.
Lake trout began to proliferate in Swan Lake about 10 years ago along with another non-native, mysis shrimp, a primary food source. The shrimp also triggered the lake trout boom in Flathead Lake in the early 1980s. Lake trout were introduced into Flathead Lake in the early 1900s, but the shrimp, as Vashro puts it, removed the "reproduction bottleneck."
Vasho says he's not just concerned with non-native species, but with the people who want to fish for them.
"Illegal introductions are a huge problem," he says. "I keep the database and I've probably documented 550 illegal introductions in the state so far, half of them being in this area."
As for the lake trout netted in the project, Vasho says the largest will be donated to area food banks.
"I know that the clients love it to have that fresh fish," says the Flathead Food Bank's Sherry Schauele.