On a boat on the southern half of Flathead Lake, a small tribal fishing crew is waging a slow battle. As gears turn, a carefully placed gill net is hauled into the boat. Mostly lake trout and whitefish are tangled in the net, writhing in the open air. Crewmembers untangle the fish and toss them into their respective bins, removing them from the lake’s population and moving one step closer to accomplishing their goal: restoring the populations of native westslope cutthroat trout and bull trout in the largest freshwater lake west of the Mississippi.

Populations of non-native lake trout and whitefish have been growing since they were introduced to Flathead Lake around 1905. Their population exploded in 1981, when mysis shrimp introduced to lakes above Flathead made their way down to the big lake. That population explosion meant lake trout began crowding out native bull and cutthroat trout.

Left unimpeded, the native fish could be crowded out to the point that they only exist in rivers and other points of the watershed above the lake, said Confederated Salish and Kootenai Tribes biologist Barry Hansen. If the lake ceases to be fertile ground for the native fish, Hansen said they won’t get as big or be as numerous, and the species that was a prominent food source and cultural symbol for area tribes won’t be preserved the way it was.

To stem the tide, 143,000 lake trout need to be removed from Flathead Lake every year. Reaching that number will require a combination of efforts, but as of now the four-man fishing crew and the on-shore staff that works in the processing and packaging plant are the biggest chess piece in the complex affair.

They call themselves the Native Fish Keepers.

Gill netting is the process of spreading vertical nets that hang suspended in the water. Fish will swim into the net that is difficult to detect, and when it tries to wriggle free, the net snags the fish behind the gills.

The practice — widely used by commercial fishing operations on the Pacific Ocean — is controversial among some fishing guides on Flathead Lake and some conservationists because it is indiscriminate. If a fish of the right size swims into the net, there is a good chance it will be caught. Native fish that are not the target Native Fish Keepers’ efforts that become ensnared in the net are called by-catch.

From the beginning, Hansen said the team understood that limiting by-catch was key to their success. Since non-native fish outnumber the native cutthroat and bull trout so severely, every native fish snared represents a step backward.

The crew mitigates the risk of by-catch by placing the gill nets in areas they know lake trout and whitefish congregate without native fish in their ranks. They know bull trout enjoy the shallower lake closer to the shores, so they move farther out into the lake to place their nets. They also pick specific sizes of netting to target the fish they want to catch.

Hansen said the efforts have been successful.

“We’ve never caught a cutthroat,” Hansen said.

The Mack Days fishing tournament the tribes host twice a year also helps reduce the non-native populations. Those fishermen are taught how to distinguish a native fish from a non-native one. Hansen said those efforts have been a success, with 37,000 lake trout turned in during this year’s event and only one bull trout.

Once the fish are captured, the crew uses a second boat to ferry the catch back to a processing center at Flathead Lake State Park on the east shore.

There, the processing crew sort the fish by species and size before running them through a fillet machine, rinsing the product and cutting off any rough edges by hand before packaging them. The packages are placed in a flash freezer and then sold in retail outlets across the state to offset the costs of the effort.

“From a food quality perspective, it’s pretty hard to buy a fish that was put in the freezer two hours after it was caught,” Hansen said.

The program has expanded steadily over the last 12 months, and a larger fishing boat purchased earlier this year has helped the crew get even more fresh fish to the market.

The lake trout and whitefish fillets can be purchased at Albertsons in Kalispell, Third Street Market in Whitefish, Harvest Foods in Bigfork and the Good Food Store in Missoula. It is also served in local restaurants like Tamarack Brewing Company in Lakeside, Latitude 48 in Whitefish and Three Forks Grille in Columbia Falls. They also sell fish to Xanterra, the company with the concessions contracts in Yellowstone and Glacier National Parks, and make donations to local food banks.

Despite the retail successes, Hansen insists that the venture is not a commercial one and the problem they are trying to solve is ecological rather than economical.

“We’re not out to make money,” Hansen said. “We’re out here to generate revenue to offset costs. This has to continue, and it has to be sustainable.”

He said that the program is an expensive one and to really have an impact it needs to go on for a long time, perhaps in perpetuity.

“We will never fish lake trout out,” Hansen said. “This is a forever program.”

Woody Red Cloud, who works on the four-man crew on the boat, said restoring the role of native fish in the Flathead Lake ecosystem has cultural significance because the fish have been a part of his and his ancestors’ lives for many generations.

“We depend on fish, that’s what fed our family back in the day,” Red Cloud said. “We all take pride in our name, Native Fish Keepers.”

On the boat back to the processing center, Red Cloud is covered in fish scales that glimmer in the sunlight. He said he believes his work is important, and he enjoys it too. Sometimes eagles follow their boat as they travel across the lake, and other fisherman often pull up and ask for their expertise about the best fishing spots.

They establish a rapport with each other on long days spent out on the lake. Some of the days are excruciatingly hot, and others are numbing cold. One by one, they fish from the net and progress is made.

“Us natives, we live by the fish,” Red Cloud said.

Reporter Peregrine Frissell can be reached at (406) 758-4438 or pfrissell@dailyinterlake.com.