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FWP’s Response To Trout Declines In Big Hole, Beaverhead And Ruby Rivers

Montana Fish, Wildlife & Parks is launching several research efforts in response to trout declines in the Big Hole, Beaverhead and Ruby rivers.

FWP, in partnership with Montana State University, has a four-pronged approach, including the following three studies:

  • Fish mortality study

A mortality study on the Big Hole, Beaverhead and Ruby rivers, as well as the Madison River, will include tagging adult fish to assess how flows, water temperatures, angling and disease influence survival. This study would also help measure the success of adaptive management plans for the Big Hole, Beaverhead and Ruby rivers that propose adjustments to fishing regulations in response to changes in trout populations.

  • Juvenile fish study

A juvenile fish study will focus on developing a better understanding of trout recruitment and the relative contributions of tributary spawning areas to mainstem trout populations. This would include using otolith microchemistry to examine fish movements and age, as well as geographical origins of juvenile fish.

  • Fish health study

A fish health study will examine the level that disease is impacting fish populations in the Big Hole, Beaverhead and Ruby rivers. This would include testing for novel pathogens and determining better ways to routinely sample fish for disease in the future.

  • Fish health monitoring

FWP is increasing fish health monitoring and reporting resources on the Big Hole, Beaverhead and Ruby rivers, including the new web portal, which launched last week.


Trout abundances in several areas of the Big Hole, Beaverhead and Ruby rivers have steadily declined since 2011 and are at or near historical lows. FWP is working to better understand the causes of these declines, which are linked to flows, water temperatures and other factors.

Monitoring and responding appropriately to these declines are top agency priorities for FWP. While research efforts begin, FWP has already taken several steps in addressing the situation:

  • On June 6, FWP announced new efforts to research and monitor trout population declines in the Jefferson Basin to better inform the state’s strategies and response.

  • FWP proposed temporary angling restrictions to protect spawning fish and limit angler-caused mortality on the Big Hole, Beaverhead and Ruby rivers to the Fish and Wildlife Commission. The commission adopted the emergency regulations.

  • On June 7, FWP Director Dustin Temple met with business owners and guides in Butte to discuss trout population declines in the Jefferson Basin.

  • FWP launched a new public web portal——where anglers can submit reports of sick or dead fish they observe. This portal allows for a direct line from anglers to the department in gathering timely information.

  • FWP staff will continue visiting sites along the Big Hole, Beaverhead, Ruby and Madison rivers to hear from anglers and monitor for sick or dead fish.

Rivers in southwest Montana are not only famous for their world-class fishing, but they are also critical to local and state economies. FWP biologists monitor fish health in waterbodies around the state. This monitoring includes sampling healthy, sick and dead fish, as well as evaluating water quality. Fish diseases are present in waterbodies, but generally don’t pose a population risk. However, fish can be more susceptible to disease and mortality when they are stressed.

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