There’s a lake trout swimming around Montana’s Flathead Lake that’s worth $10,000 for the lucky angler who reels it in between now and May 10.
But whatever fishing superstitions you may have, you’ll probably need them: The $10,000-tagged fish has only been caught three times since 2007, when the Mack Days event began offering the tempting prize.
The biannual event, which is sponsored by the Confederated Salish and Kootenai Tribes (CSKT) and sanctioned by Montana Fish Wildlife & Parks, offers potential prizes for participating anglers totaling $225,000.
In the first week since its March 13 start, more than 6,600 fish were caught and brought into the three check-in stations on the lake.
While prize money may lure in some participants, the real reward is that these events help to address a long-running problem in the largest natural freshwater lake in the Western United States. Native fish species, like bull trout and westslope cutthroat trout are being crowded out by non-native lake trout.
“The most important thing about our event is that we’re here trying to increase the population of the native fish that used to dominate the fish population in Flathead Lake,” said Cynthia Bras-Benson, the fisheries specialist with the CSKT’s natural resources department.
Were they elephants instead of fish, people might better appreciate just how problematic these non-native species have become, said Bras-Benson, adding that, “Since they’re underwater, people don’t realize what’s happened.”
What’s Happened
Mack Days was dreamed up in the early 2000s as a way to involve anglers in combating a problem that dates back to the late-1800s, when non-native fish species were first introduced to Flathead Lake.
Depending on which part of the lake anglers choose to put their rod in the water, they must have a state and/or tribal fishing license, as the southern half of the lake is part of the Flathead Indian Reservation. Fishing licenses can cost more than $100 for out-of-staters, depending on the duration and type of license.
Even for Montanans, fishing can be a costly pastime, which is why the CSKT pays out lucrative prizes to bring in as many participants as possible, Bras-Benson said. “The lottery prizes and other prizes are offered to encourage people to come out and fish, and fish for these fish.”
And unlike other fishing competitions where the bigger the fish, the bigger payout, Mack Days has a wide variety of prizes in several categories, including prizes for the smallest lake trout caught and lottery drawings that anglers who only catch one fish are eligible to enter.
So far, this year’s event is tracking a little bit ahead of past spring events, and particularly with the number of small fish that anglers are bringing in, according to Bras-Benson. But it’s hard to know if that’s a sign these events are successfully reducing the number of invasive lake trout, as planned, she said.
“Doing something like this takes years,” Bras-Benson added. “It doesn’t happen quickly.”
The Salois family of Pablo, Montana show off their lake trout entry in a past Mack Days event. (Courtesy of Mack Days) 
Nicole Peters caught the largest lake trout entered in Mack Days on Mother's Day in 2010. It measured 45 inches and weighed 38.5 pounds. (Courtesy of Mack Days) 
Ryker Bair, left, of Helena, Montana, caught the winning large lake trout in the 2024 fall Mack Days, measuring 36.25 inches and weighing 20.05 pounds. He fished with his father, Justin Bair, of Dillon, Montana. (Courtesy of Mack Days)
Finding the $10,000 Fish
With about seven weeks left in the event, there’s plenty of time for anglers to try to find the big-money fish swimming around the lake. In addition to that fish tagged for a $10,000 payout, there are two fish carrying prizes of $5,000 each and five fish tagged for $1,000 prizes each.
There’s no special process for picking the big-money fish; rather, they’re among some 9,000-plus fish that Mack Days organizers netted the week before the event began. “We’re pretty confident those fish are still out there,” Bras-Benson said.
But these fish have plenty of places to hide in the 197-square-mile lake with depths that reach more than 370 feet, and they have mostly eluded the bait of anglers in years past: Only one $5,000 fish has been caught since 2007, along with only one $1,000 fish. Though some tagged fish from prior events may still net anglers a decent payout, the big prizes don’t carry over.
Anglers can still rack up some decent payouts thanks to a bonus system that incentivizes the number of fish caught. Some competitors have already caught 300 fish.
Considerations For Out-of-State Anglers
The spring Mack Days event typically draws more participants, as the fall event must compete with football and hunting seasons, Bras-Benson said. And increasingly, more out-of-staters are coming to the Flathead Valley for the event.
Participants who will be bringing a boat need to certify that their boats are mussel-free to participate in Mack Days, and all watercraft entering the Flathead Basin must have proof of inspection from an authorized inspector.
In addition, anglers are responsible for reading and adhering to all Montana and Tribal fishing regulations, including securing the appropriate licenses. And participants must register and agree to the event rules. More information about the rules and prizes can be found by visiting www.mackdays.com.
Finally, Bras-Benson urges anglers to take appropriate safety precautions, including checking the weather every day and ensuring they have the proper safety equipment aboard their watercraft before heading out on the water.
Anglers also need to know how to correctly identify lake trout — so far this year, two bull trout have been brought to the check-in stations, and anglers who mistakenly keep these fish can be cited and fined.
The Mack Days website has a wide range of tips for participants, along with statistics on prizes awarded so far. Anglers who don’t want to keep the fish they catch can donate them and the CSKT will take these fish and process them, with proceeds put back into the program, Bras-Benson said.
Charter boats are also an option for out-of-towners who come to the area without a boat. And even if participants can only make it out on the lake for a day or two, there are still opportunities to go home a winner, Bras-Benson noted. “We take entries up until the last day.”
