Montana Fish, Wildlife & Parks continues to monitor fish health in the upper Missouri River Basin and has collected several tissue samples from sick fish this summer.

Thus far, the sampling efforts have shown no abnormal results. Staff have received seasonal reports of sick or dead fish in the Big Hole, Beaverhead and Ruby rivers this summer. Sick fish were reported in 2023 as well. Compared to the fish population size, angler reports of sick fish have been relatively few.

FWP staff have leaned on prompt reports of sick fish from anglers and added staff capacity in response to ongoing fish health and trout population concerns in the upper Missouri River Basin.

This fish health monitoring effort is supported by a new plan for a multi-year fish health assessment in the basin. The Big Hole Fish Health Workgroup—comprised of staff from FWP, the U.S. Fish & Wildlife Service, U.S. Geological Survey, Montana State University, and Washington State University—helped establish new strategies for FWP to regularly assess fish health in southwestern Montana. This assembly of partners will help address the backlog of fish tissue samples that was an issue in 2023.

In accordance with the plan, FWP staff will collect fish tissue samples during current fish health monitoring, annual population sampling efforts in the spring and fall, and opportunistically while responding to reports of sick fish. Those samples will be evaluated by disease experts at Washington State University, Montana State University, and the U.S. Fish & Wildlife Service to better understand what may be contributing to fish health concerns.

Anglers have reported fish with head lesions or fungal infections, but the causes of these maladies remain unknown. Anglers can continue to report sick and dead fish from the Big Hole, Beaverhead and Ruby rivers by calling fish health staff based in Dillon at 406-596-5175 or going online to sickfish.mt.gov. Anglers should not transport sick fish away from the river unless directed by FWP staff.

“We’re grateful to anglers who have promptly reported sick or dead fish in the upper Missouri River Basin,” said Mike Duncan, FWP fisheries program manager. “Anglers play an important role in the research that will inform how we respond to the fish health and population concerns in these rivers.”

Background

FWP and MSU embarked on a new cooperative research effort last year when annual sampling found fish numbers to be at or near historic lows in sections of the Big Hole, Beaverhead and Ruby rivers. This was coupled with reports of sick and dead fish in these rivers.

FWP’s partnership with MSU includes hiring three PhD students and additional staff to study fish mortality, recruitment and health. Annual summaries published next spring will be made available to the public via FWP’s website.

To learn more about fish research in this area, click here.