FWP asks for Swan Lake gill-netting to continue

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

Over 20,000 lake trout were pulled from the lake during the initial project, which ran from 2009-11. Concern for Swan Lake’s bull trout population is the driving factor behind the $90,000-a-year project said FWP fish biologist Leo Rosenthal.

The project is a group effort between members of the Swan Valley Bull Trout Working Group, which includes Montana FWP, the Montana Department of Natural Resources, the Confederated Salish and Kootenai Tribes of the Flathead Nation, Montana Trout Unlimited, the U.S. Fish and Wildlife Service and the Flathead National Forest.

Bull trout was listed as threatened under the Endangered Species Act in 1998. Incidentally, that is the same year lake trout started popping up in the Swan system.

Since 2006 Swan Lake’s bull trout population has halved, from approximately 5,200 to 2,500.

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

“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.”

The thought is that reducing the population of lake trout will have a positive affect on bull trout population, and hopefully stall the steady decline that’s been seen over the last decade. They need to extend the length of 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 were spawned with the start of the project become mature enough to spawn themselves. Bull trout population numbers are estimated using the number of spots where eggs are laid in Swan system tributaries and are known as redd counts. 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 the bull trout coordinator for the U.S. Fish and Wildlife Service, Wade Fredenburg.

It was one of three places in Montana you could still harvest a bull trout until last year. While you can still harvest the fish in Koocanusa and Hungry Horse Reservoirs, it was listed as catch-and-release in Swan Lake because its numbers are so low.

“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.”

Although, there is no real way to eradicate lake trout from Swan Lake, Fredenburg said gill-netting is a viable way to try to reduce the number of fish that compete with native species because they can target area’s of the lake that lake trout like to hang out.

Swan Lake gill-netting took place while most adult bull trout were up tributaries spawning in August and September. And they only netted areas of the lake deeper than 60 feet.

The new five-year EA is scheduled to follow a similar process with some minor changes, such as using nets with smaller mesh to target juvenile lake trout between 11-22 inches.

Swan Lake resident Joe Lawrence caught his first bull trout when he was six-years-old. He is now 73, and has helped out on the gill-netting boats over the last few years.

He said he’s never caught a lake trout in Swan Lake, but has seen plenty on his fish finder.

“There’s an awful lot of lake trout in this lake, and there didn’t used to be,” Lawrence said. “Other guys catch them, I think they know I don’t like them.”

He thinks the ecosystem of the lake has changed dramatically since his youth, partially due to non-native species of fish that have been introduced to the lake over the years. The battle between bull trout, Kokanee and lake trout comes down to one thing for Lawrence, Mysis shrimp.

They were introduced to Swan Lake in the 1970s, and had the desired effect of growing larger Kokanee salmon and increasing the fishery on the lake. But according to Lawrence, when the lake trout showed up, that’s when everything went down hill.

“With the Mysis shrimp and lake trout and the bull trout and the salmon, one’s going to go away,” Lawrence said. “And it’s going to be like Flathead (Lake), the bull trout are going to go away, we have to do something.

The five-year EA draft is currently out for a 30-day public review through June 15. Questions and comments on the draft can be directed to Rosenthal by phone, 751-4548, email, lrosenthal@mt.gov, or mail, FWP, 490 North Meridian Road, Kalispell, MT 59901.