The Greatest Westslope Cutthroat Fishery on the Planet, Part I

by Mike Peterson

Leo and I grew up in the same hometown, but a decade apart. I knew the reputation of his father, Paul, as a dentist, fly tier, award-winning caster, but more importantly, an excellent fisherman. Paul's flies still remain in my arsenal, and his story of early adoption of sight and tight line nymphing unlocked the Beaverhead in the '70s and '80s (legendary stuff). Leo was on the same path. A biology degree in hand from the U of M and dental applications in the mail. Then came a volunteer research opportunity that changed his life. A wildlife Grad student, named Sophie, set him on a project to study American Dippers on the Bitterroot River. Leo is a passionate speaker, with great command of our language. He will quickly tell you, in an engaging manner, that the experience of walking around in nature, observing animals, "blew his mind". The dental school apps were forgotten, and it was off to MSU for a Masters in Fisheries Biology.


Fast forward a few years. Leo is now the Fisheries Management Biologist for the west side of the Bob Marshall and the Swan range. It includes the South Fork & Middle Fork of the Flathead River drainages in the Bob Marshall and Jewell Basin in the Swan range. Hard to top that for an office.

So how does one study fish in such a vast expanse of wilderness?? You better have boots that will walk, wade, and ride, and the skills to go along with them. 

Fishing and Floating in an Alpaca raft. That's his job.
On a recent South Fork of Flathead trip, I serendipitously ran into Leo. What was he doing? Fishing and Floating in an Alpaca raft. That's his job. Monitoring Westslope Cutthroat trout means population studies to compare to past data. It's a wilderness. That means no electrofishing or motors allowed. So, how do they do it?? 
Using a population algorithm, he can estimate the number of fish per mile.
Westslope in the South Fork have adapted to live where there is not much food. They are eager to the Fly. Leo picks out a two to three-mile section of the river (three such sections are used on the South Fork). Annually, six anglers fish for two days. They will catch 200 to 300 fish. They mark the fish with a bright tag (that will eventually fall off): Blue for less than 10 inches, Red for 10 to 12 inches, and Yellow for the bigger ones. Then, on day three, Leo and crew put on dry suits and snorkel the river. The water is clear. They can count the number of fish tagged and not tagged. Using a population algorithm, he can estimate the number of fish per mile. Those six anglers will have handled and tagged about 30% of the population of cutthroat. There lies the problem. 

The Hungry Horse dam was built in 1953. It isolated the South Fork from the rest of the Flathead drainage. This created a complete river system with genetically pure native cutthroat trout, the largest system of its kind on the entire planet!! These fish evolved to live in a clear mountain streams with minimal food. They are aggressive and eager to the fly which is awesome for an angler. The downside is the use of the Flathead River system is dramatically increasing. The fish are being caught a lot. The river is being loved to death


Enter my friend Leo. By tracking the population of Cutthroat, they can monitor the fishery and make recommendations about its use. For example, in the last few years, they have seen 40% of the fish over 12 inches with mouth scars from hooks. So, just last year, treble hooks were banned on the South Fork. However, with increased use, what other thoughts should we have as responsible anglers? Leo's big three are: 1) Limit your catch. Maybe after 5-10 fish, take a break and just enjoy the river  2) Consider pinching down your barb or buying barbless flies. 3) Release fish quickly and do not remove them from the water for photos. These Cutthroat rarely exceed 16 inches.

The South Fork and the Bob Marshall are very special places. Thanks, Leo for taking care of it. I hope you all get the chance to see this river, and even run into Leo while he is "On the Job". 

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