Every spring in the predawn darkness, before the sun’s first rays illuminate the surface of Flathead Lake, Jason Mahlen loads his boat with an arsenal of fishing gear, carefully selecting rods, reels and a collection of tackle designed to entice lake trout from the deep. The spring air is cool, carrying a sense of anticipation as Mahlen prepares for another day of catching lakers in the Mack Days spring competition. 

Meanwhile, Keenan Blackbird, a dedicated fisheries biologist for the Confederated Salish and Kootenai Tribes of the Flathead Indian Reservation, captains a crew to retrieve gillnets full of lake trout and lake whitefish. Blackbird maneuvers the boat and its hydraulic lift that hoists the nets from the depths. He and his team work swiftly and efficiently, removing the entrapped fish from the nets, placing them on ice, and shuttling them back to a processing operation at Yellow Bay, where they are fileted, packaged and distributed to stores and restaurants around Montana. 

The Mack Days competition, gillnetting and the bustling fish-processing operation are part of a comprehensive strategy by the Confederated Salish and Kootenai Tribes (CSKT) to protect native fish in Flathead Lake by reducing the number of non-native lake trout. 

“Native fish are important to the culture, to the history of the Confederated Salish and Kootenai Tribes and the state of Montana,” said CSKT fisheries specialist Cindy Benson, who oversees Mack Days. 

Flathead Lake is the largest natural freshwater lake west of the Mississippi River. Historically, it was home to an abundance of native fish, including the threatened bull trout and westslope cutthroat trout. In the early 1900s, lake trout were introduced, likely by railroad workers. But they remained relatively dormant until the 1970s when mysis shrimp that were introduced upstream by Montana Fish, Wildlife and Parks began making their way to Flathead Lake. The mysis shrimp provided an abundant food source for lake trout, which exploded in population. Once they reach adulthood, however, lake trout also eat other fish, including smaller lake trout.  

Recognizing the issue, CSKT, Montana FWP and the U.S. Fish and Wildlife Service began brainstorming in 2000. Not everyone was keen on the idea of reducing lake trout, which had become a popular sport fish. So CSKT came up with the idea to let anglers take part in their reduction, and later, cover some costs by selling the harvested fish to local restaurants and grocery stores. 

Sitting near the boat dock outside the fish-processing operation at Yellow Bay, CSKT fisheries biologist Barry Hansen explained that the goal is not to eradicate lake trout. 

Money from the sale of lake trout and whitefish goes back into conservation efforts to protect native fish in Flathead Lake. “We want to preserve, maintain and protect the native trout, and the only way to do that is to reduce the lake trout,” CSKT biologist Barry Hansen said. “Without some intervention, we’re going to lose those native species.” Credit: Cameron Evans / MTFP

“Lake trout will always be here,” Benson said. “They come in from other areas into this lake and there’s just so many of them. The goal is to reduce their numbers and to hopefully see an increase in the populations of the native fish.”

Flathead Lake is co-managed by CSKT and the state. Although only the south half of the lake is on the Flathead Reservation, and the majority of lakefront property is privately owned, CSKT has taken charge of the ongoing challenge to preserve the lake’s ecosystem.


Beginning in 2002, the tribe started hosting the “Mack Days” competition, which takes place every spring and fall and features up to $225,000 in cash prizes for anglers. 

Over the years, Mack Days has evolved to encompass various categories and incentives for participants. The highlight of these contests is the catch of tagged fish, with the top fish cashing in at $10,000. 

“We work to grow Mack Days bigger and bigger,” Hansen said. “We got about 900 fish in the first contest. The contest we just finished, we got 33,000 fish.”

CSKT sponsors Mack Days with money the tribes receive from companies that take power from the Seli’š Ksanka Qlispe’ and Hungry Horse dams as compensation for the effects that raising and lowering of water levels in Flathead Lake have on fish and wildlife. About 20-30% of the funds come from selling the fish that are caught. 


Gillnetting is another essential component of reducing the lake trout populations. In 2017, the CSKT tribal council approved the incorporation of a nonprofit, Native Fish Keepers, which sells filets of  wild-caught lake trout and whitefish caught in its gill-netting operations, as well as fish harvested during Mack Days. 

“We have distributors that are buying them and distributing to stores and restaurants around Western Montana,” Benson said. “It helps to put back money into the program because this is something that is expensive to do.”

Anglers and gill-netting boats pull up to the boat dock at Yellow Bay and check stations to unload their catch. Staff bring the fish to the processing facility, or “fish house,” where bins of fish on ice await a fileting machine. Staff send the highest quality fish through the machine and separate the guts, which go to a composter. The filets are placed in vacuum-sealed bags, flash frozen and boxed for distributors. 


When CSKT began efforts to suppress the lake trout population, they estimated there were 1.4 million lake trout age 1 and older in Flathead Lake and set out to reduce the adult fish — age 8 and older — by 75%. 

Over the years, mysis shrimp have changed the flesh of lake trout from white to an orange, salmon-like hue. “People say it tastes way different than it used to,” said CSKT fisheries specialist Cindy Benson. “It’s good. The lake trout don’t have all the fat they used to from eating the kokanee salmon so they’re a lot leaner fish.” Credit: Cameron Evans / MTFP

“They generally reached maturity at age 8, so our target is to reduce the adult population,” Hansen said. “That’s when they’re eating the other fish.”

In order to reach that goal, CSKT and anglers will need to remove roughly 140,000 lake trout each year. The annual harvest is currently about 125,000. 

“It’s going to take time before the lake returns to its balance,” Hansen said. “We decided to remove them gradually so we wouldn’t abruptly change the system and so new fisheries would develop while the old fishery declined. And that seems to be working.”

Hansen said efforts to remove lake trout will likely continue in perpetuity, but he said it’s worth the effort. It’s not yet clear how the bull trout and cutthroat trout are faring, but it is clear that there aren’t many places left in Montana for bull trout to thrive, largely due to climate change and warming waters. Flathead Lake’s cold water provides refuge for bull trout and prime habitat that connects to waters in Glacier National Park, wilderness areas and well-managed forest lands. 

“This is the place where we can make a difference and hang on to that intact ecosystem,” Hansen said. 


While species reduction is the focus of fisheries biologists, many anglers participate in Mack Days simply for the competition and money. For them, removing predatory lake trout is an afterthought. 

Some participants have dedicated years to competing, like Mahlen, a seasoned angler who has taken part in spring Mack Days for nearly 15 years, winning the competition seven times and coming in second more times than he “would like to admit.”

“I did it to challenge myself,” Mahlen said. “I wanted to win. I don’t really pay a whole lot of attention to how to manage it.”

Top anglers can expect to take home between $10,000 to $15,000 each spring. But the money doesn’t come easy. 

Every spring, Mahlen works four 10-hour shifts at his day job so he’s able to take the weekends off for the competition. He fishes in the wind, rain and sometimes snow, hitting the water before the sun rises and not returning to the dock until dark. He’s lucky if he gets a few hours of sleep each night.

Anglers invest years of time and money into gear and figuring out the fishery, each with their own style of fishing. Mahlen, for one, hopes for an end to the current 100-fish daily limit.

“It would be interesting to see what anglers could do if there was no limit,” Mahlen said. “But hitting 100 fish is not easy.”

Hansen said Mack Days and gillnetting complement each other in efforts to protect native fish. Gillnetting allows biologists to catch big lake trout, while anglers jigging in deep waters can skillfully capture small lake trout while avoiding bull trout, which they can more easily release alive. Through their combined efforts, biologists and Mack Days competitors play a vital role in the future of native species. 

“We want to preserve, maintain and protect the native trout, and the only way to do that is to reduce the lake trout,” Hansen said. “Without some intervention, we’re going to lose those native species.”

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Cameron Evans is a freelance journalist based in Missoula. Cameron is a graduate of the University of Missouri’s School of Journalism and worked for the Missoulian. Her work has appeared in USA Today, Kaiser Health News, Business Insider and INSIDER. Find her at cameronevans.me or follow her on Twitter.