State wants to continue Swan Lake netting

Montana Fish, Wildlife and Parks recently released an environmental assessment proposing a five-year extension for the lake trout gill-netting project completed on Swan Lake in the fall of 2011.

More than 20,000 lake trout were removed from the lake during the initial project, which ran from 2009 to 2011. Concern for Swan Lake’s bull trout population is the driving factor behind the $90,000-a-year project, FWP fish biologist Leo Rosenthal said.

The Swan Valley Bull Trout Working Group heads up the project, which includes FWP, the Montana Department of Natural Resources, the Confederated Salish and Kootenai Tribes, Montana Trout Unlimited, the U.S. Fish and Wildlife Service and the Flathead National Forest.

Bull trout were listed as threatened under the Endangered Species Act in 1998 — the same year lake trout appeared in the Swan River drainage. Since 2006, Swan Lake’s estimated bull trout population decreased from 5,200 to 2,500.

While by-catch from the gill-netting project killed about 100-150 bull trout a year over the life of the project, Rosenthal said competition with and predation by lake trout is most likely the root cause of the decline in bull trout numbers.

“There’s many places in the west where lake trout are having an adverse affect on native species of fish,” Rosenthal said. “Finding ways to feasibly control them is something Fish, Wildlife and Parks is actively looking for.”

FWP wants to extend the project to determine how successful it was in reducing Swan Lake’s lake trout population and increasing the lake’s bull trout and kokanee salmon populations.

“To see a response in the bull trout and kokanee is going to take a bit more time to see if the project was effective,” Rosenthal said. “The more data you have, the better your capability becomes to evaluate whether or not your methods have been effective.”

In this case some of the data won’t be available until bull trout that spawned with the start of the project become mature enough to spawn themselves.

Bull trout population numbers are estimated counting the number of redds — nests where eggs are laid — in the Swan drainage. Bull trout take 5-6 years to reach adulthood.

Swan Lake has historically had one of the most stable bull trout populations in Montana, said Wade Fredenburg, bull trout coordinator for the U.S. Fish and Wildlife Service. It was one of three places in Montana where fishermen could still harvest bull trout until last year.

But while bull trout can still be harvested in Lake Koocanusa and Hungry Horse Reservoir, it was catch-and-release in Swan Lake because of their low numbers.

“Swan Lake is kind of a gem for fishing for bull trout,” Fredenburg said. “In this case, it’s more about holding onto what we got rather than restoring.”

While acknowledging no sure way exists to eradicate lake trout from Swan Lake, Fredenburg said gill-netting is a viable way to try to reduce lake trout because they can target areas where lake trout typically hang out.

The draft EA is available for public review through June 15. Comments can be made by calling 751-4548, e-mailing lrosenthal@mt.gov or by mailing to Montana Fish, Wildlife and Parks, 490 North Meridian Road, Kalispell MT 59901.