LAKESIDE — The guessing has begun on Flathead Lake.
There are a lot of theories on what’s going to happen to the fishery on the largest natural freshwater lake west of the Mississippi, but more than a century of man’s meddling in the lake’s natural order has made it challenging for anyone to say for certain.
The Confederated Salish and Kootenai Tribes wrapped up their fourth year of gill netting operations aimed at suppressing numbers of the non-native lake trout.
A biologist with the tribes said lake trout numbers in the lake are trending downward.
Flathead Charter boat operators say they’ve seen a drop in both the numbers and size of the lake trout they catch.
Norm Brewer has run a charter boat operation out of Lakeside for years.
“I’ve seen our catch rate drop dramatically,” Brewer said. “It used to be that we would go out and catch 15 to 25 in day. A few years ago, it dropped down to 10 to 15. Currently, we catch between two to seven.”
The 20- to 30-inch fish that customers like to keep to eat are also becoming more difficult to find.
“For years tourists from all over the world came here because we had some of the best lake trout fishing in the whole United States,” Brewer said. “We’re seeing that disappear.”
Mike Howe owns the largest charter boat operations on Flathead Lake. In a season, his boats make 700 trips to take upwards of 3,000 fishermen out for a day of angling.
He’s also seen a drop in his daily catch and his fishermen aren’t catching many of the 28- to 35-inch fish that made Flathead Lake a destination fishery.
Howe is opposed to the tribes' gill net operations and their decision to sell some what they catch to help offset the cost of the suppression efforts.
“If they are going to manage lake trout populations, there are better ways to do it,” Howe said. “I think there are going to be unintended consequences. …This was a world-class lake trout fishery for both size and numbers of fish. It simply isn’t that anymore. I have longtime customers, who have been coming here since the '80s and '90s, not return.
“It’s a complex issue,” he said. “I’m anti-gill net. I don’t think it’s right to take a fish that belongs to the citizens of Montana and sell it for profit.”
Last spring, the CSKT Tribal Council established the nonprofit Native Fish Keeper Inc. business that sells some of the lake trout and whitefish caught in suppression efforts to help offset some of the costs of their native trout restoration project.
The tribes’ long-term goal is reduce lake trout numbers enough that native bull and westslope cutthroat trout will return to the lake.
When the effort began, experts pegged the lake trout population at about 1.5 million. In order to see a reduction in the lake’s overall population of lake trout, biologists said the tribes would have to find a way to remove 143,000 lake trout a year.
So far, that’s not happened.
The two Mack Days derbys and netting operations in 2016 resulted in the capture of 100,000 fish.
“One of the principles that we’ve had all along was that we would approach this in an incremental way,” said CSKT fisheries biologist Barry Hansen. “It would be a slow change that would take years before new fisheries would come on.”
There will always be a lake trout fishery in Flathead.
“We didn’t even have an alternative in the EIS (environmental impact statement) to zero out lake trout in Flathead,” Hansen said. “The alternative we selected was 75 percent. While that is a substantial reduction, no one knows for sure that we can get there.
“Our suppression efforts are complicated by the fact that lake trout have been in Flathead for 100 years,” he said.
The netting operation in Flathead Lake is focused on lake trout in the 8-year-old range. Reducing those mid-sized fish opens the door for a boom in younger fish that will grow faster without the competition.
“We are going to have to fish through that expansion,” Hansen said. “This is something that we’ll have to continue for years and years.”
The reduction in lake trout numbers will change the fishery. It could provide opportunities for perch populations to swell, which would give anglers a chance to catch lake whitefish in the summer.
The hope is that it will allow bull trout and westslope cutthroats to return to the lake.
Hansen said biologists have been seeing larger numbers of juvenile bull trout in the lake, but it’s too early tell what that might mean.
With climate change, the lake could become for a refuge for the coldwater- dependent native species, as waters in the rivers and streams begin to warm.
“It’s the biggest lake in the West,” Hansen said. “And it’s deep. It will provide a thermal refuge for fish.”
Retired state fisheries manager Jim Vashro said it’s hard to know exactly what will happen with the lake’s fishery as lake trout numbers are reduced.
“Bull trout were holding out pretty well into the 1980s, but then the fly in the ointment appeared,” Vashro said. “Mysis shrimp profoundly changed the whole picture. The Flathead Lake of the 1980s no longer exists.
“Everything that happens now is just a Band-Aid,” he said. “They are treating a symptom by trying to suppress lake trout with gill netting. Lake trout are really robust. They will just bounce back and the expensive suppression efforts will have to go on forever.”
The shrimp were introduced in lakes upstream as a food source for kokanee salmon and drifted into Flathead Lake, where they ate the plankton on which the kokanee also depended. Their appearance eventually ended in the crash of the kokanee population and boom in lake trout numbers. During that cascade of events, bull trout and cutthroats became prey for the growing numbers of lake trout, and their populations dropped dramatically in the lake.
During that time, biologists saw the numbers of bull trout redds — the nests of spawning bull trout — on the Middle and North forks of the Flathead River drop by about 60 percent.
Today, bull trout redds are at about 60 percent on the Middle Fork and at much lower numbers on the North Fork.
There’s debate on why bull trout are faring better on the Middle Fork.
Vashro said the North Fork’s problems stem from fire history, resource development and experimental research on three important spawning tributaries where biologists tagged juvenile bull trout only to see them die.
“Their numbers have never really bounced back,” Vashro said.
Biologists from the tribes have a different theory.
Hansen said they believe that bull trout on the Middle Fork have adapted to the presence of lake trout in the lake by living their lives out in the river where they have had a better chance of surviving long enough to spawn.
Bull trout in the North Fork have continued to migrate into the lake and therefore haven’t done as well, he said.
Lake trout spawn along the shoreline of the lake.
Montana Fish, Wildlife and Parks fisheries biologist Kenny Breidinger monitors lake trout populations on the north end of Flathead Lake and bull trout redds upstream.
Over the last few years, he said both have remained stable.
Overall, the redd counts are about 60 percent of where they were before bull trout crashed in the mid 1990s. That hasn’t changed much over last few years.
Breidinger also hasn’t noticed a shift in lake trout numbers that he catches in the spring during population netting surveys.
“When you’re dealing with a really big lake like this one where relatively small numbers of fish are being removed, it’s really too early in the game to expect to see changes in the fishery,” he said. “That’s going to take a while for that to play out.”
And it’s way too early to predict what the fishery will be when that happens.
“It would certainly be a different fishery if lake trout numbers drop dramatically,” Breidinger said. “Lake trout are in higher densities than we would ever expect to see from bull trout.”
Whitefish are currently the abundant species in the lake. Prior to the explosion of lake trout, kokanee were in the lake in high numbers.
“It’s really hard to predict what would happen if lake trout suddenly disappeared or their numbers were cut back substantially,” he said. “All of these systems are in a constant state of flux. They are being impacted by climate change, introduction of new species, water quality, and surrounding land use. It’s really complex and almost impossible to predict.”