FWP reconsiders gill-netting lake trout in Swan Lake

Laura Lundquist

(Missoula Current) After an eight-year break, Montana Fish, Wildlife & Parks will resume efforts to shrink the invasive lake trout population in Swan Lake in order to save threatened bull trout.

On Friday, the Fish, Wildlife & Parks commission voted unanimously to allow the department’s fisheries staff to explore plans to resume efforts to control the lake trout population in Swan Lake.

Fisheries chief Eileen Ryce said her division would initiate a Montana Environmental Policy Act process to get additional public input before taking any action. But the plan is to conduct gill-netting this year, and staff will begin monitoring lake trout and bull trout populations to gauge changes. After that, the department would contract with commercial fishing services to do the work starting in 2025.

“The lake trout removal project is considered by the Swan Lake Bull Trout Working Group to be the most effective and efficient way to remove lake trout in order to provide an opportunity for the bull trout numbers to recover,” Ryce said. “Our concern is, without this management action, bull trout could be extirpated from the area.”

FWP and the working group are already familiar with gill-netting for lake trout in Swan Lake, because it’s been done before.

The Swan Valley used to boast the strongest bull-trout population in the state. But in 1998, the same year bull trout were listed as threatened, fishermen started catching lake trout in Swan Lake. The invasive population took off a few years later. Because lake trout outcompete with other trout and salmon and devour their young, the bull trout population began to dwindle. The number of bull trout spawning nests or “redds” in four Swan tributaries crashed from about 600 in 1998 to about 210 in 2010.

To address the problem, the Swan Lake Bull Trout Working Group formed, including the U.S. Fish and Wildlife Service, Forest Service, Montana Fish, Wildlife & Parks, Confederated Salish and Kootenai Tribes, and Montana Trout Unlimited.

The working group started a three-year experiment in 2009 to see if gill-netting would do the trick. More than 20,000 lake trout were eliminated, so FWP agreed to another five-year study, starting in 2012. It appeared to have an effect, because the number of netted lake trout declined, possibly because the population declined although some suggested lake trout had moved to other parts of the lake. The final FWP report published in May 2017 said there were no plans for continued netting in 2017.

In 2016, FWP had supported backing off the effort, partly because it got pushback from people who liked fishing for lake trout. At the time, the project cost about $100,000 a year. But the Forest Service kicked in $70,000 and Montana Trout Unlimited provided $18,000 and volunteer work.

A few years ago, the U.S. Fish and Wildlife Service said it would take over, so the other groups waited to see what would happen. Then, the Service said it had to go through a public comment process but never started it. However, the Service may finally release a draft environmental assessment for public comment in the next few weeks.

In the meantime, eight years have passed. During that time, bull trout and kokanee salmon populations continued to decline while lake trout have surged again. FWP’s fisheries surveys counted only 135 bull trout redds in 2023, barely half of the 244 redds counted in 2020 after the previous suppression efforts paused, and far less than the 5,000 redds estimated before lake trout were illegally introduced.

Montana Trout Unlimited spokesman Clayton Elliott praised FWP for taking action.

“We have a commitment to the statewide fisheries plan and getting that right as we went through that process regarding the focus on native fish management. It’s alarming to see what was once a stronghold of that population continuing to decline as the number of lake trout increase,” Elliott said. “I’m happy to see that perhaps the initiation of the state process is prodding the feds to get up to speed as well.”

FWP received 30 public comments on its initial proposal. While most were in support of the project, a few were worried about accidentally catching other species, while others like fishing for lake trout. To address complaints about less fishing opportunity, FWP staff would work to develop a kokanee fishery, once the lake trout population is sufficiently knocked back.

One of the commenters suggested developing a lake trout fishing derby to help reduce the number of lake trout. But Commissioner Pat Tabor said he’d met with the regional fisheries managers to learn more about the situation, and they cautioned against anything that might compete with the Flathead Lake fishing derby run by the Confederated Salish and Kootenai Tribes.

“Maybe if it can be done in conjunction with that,” Tabor said. “That’s on the radar, but it doesn’t take from the core mission that this has to be done to prevent any more invasion by this species.”

Contact reporter Laura Lundquist at lundquist@missoulacurrent.com.