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Wildlife officials to study trout population crash in the Jefferson Basin


Montana wildlife officials will begin studies this year to get to the bottom of a historic trout population crash in the Jefferson Basin.

Spring trout population surveys in the basin were the lowest on record.

At a recent meeting of the Big Hole Watershed Committee, the community was assured by Fish Wildlife & Parks Biologist Jim Olsen that multiple studies into the population crash will start this year.

“This is our focus, this is what we’re really putting a lot of time and effort into right now,” Olsen said.

Conservationists and outfitters in the region have been asking the state to study the fish population decline as numbers have dropped in recent years.

Olsen said the department is partnering with Montana State University to study what is responsible for the historic fish death.

The department also recently hired an ecologist who will analyze historical data from the watershed and search for patterns and blind spots. The historical analysis will begin this year and the mortality study will kick off in 2024.

Montana wildlife officials have also created a new web portal for residents to submit reports of dead and diseased fish. The tool was created as part of efforts to address historic population crashes hitting trout in southwest Montana.

Fishing guides and outfitters on the Big Hole, Beaverhead, Ruby and Jefferson rivers have found fish with fungal infections and lesions in recent years.

Montana Fish Wildlife & Parks says they’re interested in data from around the state, but particularly focused on reports from those four rivers in the Jefferson Basin. The new portal can be found at

John joined the Montana Public Radio team in August 2022. Born and raised in Helena, he graduated from the University of Montana’s School of Media Arts and created the Montana history podcast Land Grab. John can be contacted at
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