Blog

With the 2024 field season coming to a close, we wanted to provide an update on the sampling that was completed in the upper Missouri Basin this year and what’s to come the next few years. If you’re not familiar with our efforts in response to the declines and fish health concerns in the Big Hole, Beaverhead, and Ruby rivers, FWP has committee nearly $3 million to studies that will help us better understand those fisheries and the potential limiting factors influencing brown and rainbow trout. We’ve committed to the following, which also involve the Madison River: 1) a mortality study that will compartmentalize individual factors contributing to adult trout survival , 2) a natal origins and recruitment study that will target survival and habitat use of juvenile trout in the mainstem rivers and tributaries, 3) a recreational study characterizing and quantifying use along each of the rivers including nonanglers such as floaters, campers, etc., and 4) a fish health study to identify the pathogens responsible for the head lesions and fungal infections observed in recent years as well as the prevalence and potential population-level effects of those infections. The first three studies are collaborative efforts between FWP and Montana State University and include a PhD student dedicated to each study. The fish health study is led by a workgroup that was established last winter that includes FWP staff and external partners from across the country including Montana State University, Washington State University, the U.S. Fish and Wildlife Service, and the U.S. Geological Survey.

The tagging efforts and creel surveys associated with the mortality and recreational studies have drawn a lot of attention since we began tagging fish last spring. We were able to tag over 10,000 trout this year, which provides an invaluable opportunity to learn more about our fisheries. As most of you have probably heard by now, the spring estimates indicated that the rainbow and brown trout in many of our sections in the upper Jefferson Basin stabilized or even increased following historic or near historic lows in 2023. However, 2024 has turned out to be another relatively dry year resulting in low flows and high water temperatures across much of SW Montana. Although we know water is the major limiting factor for our trout fisheries in the upper Missouri Basin, there’s nuance to exactly how water influences each population. By tagging and tracking individual trout over the next several years, FWP and MSU will be able to better understand the relative contributions of water temperatures, flows, disease, and angling to adult survival across a range of conditions that fish experience in the four rivers. Those efforts will entail FWP’s long-term sampling each spring and if conditions allow, a single pass through each section in the fall prior to brown trout spawning. The fall sampling efforts for these studies, which are much less extensive than was traditionally completed in the fall, provide an additional encounter opportunity for us to assess survival leading into the stressful spawning and winter seasons. Although folks are still out fishing, the number of reported tags is lower than we anticipated and what some of our fall sampling efforts indicated should be expected. The information gained from reported tags is vital in understanding what is or is not contributing to the declines in brown and rainbow trout abundances that have occurred over the last 10 years and other periods of drought. Better understanding the relative contributions of potential limiting factors will allow FWP and our partners to focus on what’s most important to maintaining these fisheries. For FWP and MSU to have a complete understanding of the complex issues facing our fisheries, we need support from the angling community, so please do your best to report tags (www.mtcfru.org/msutag), participate in the creel surveys (https://www.mtcfru.org/msurecsurvey), and encourage everyone you see on the river to do the same.

FWP has committed new staff and funds to directly assess the fish health issues that have drawn much attention the last few years. Our new technician in Dillon has improved our ability to respond to reports of sick or dead fish, which resulted in valuable tissue samples that likely would have not been collected without his help. Anglers and guides are still encouraged to call (406) 596-5175 to report fish with head lesions or fungal infections. However, please do not transport any sick or dead fish away from the river. Tissue samples collected throughout the year are continually being processed and sent to our workgroup partners for further evaluation. A comprehensive summary of those efforts will be available to the public by spring 2025. Those findings will be used by the workgroup to refine our monitoring and testing efforts next year.

As always, please reach out to me or one of the local biologists if you have questions or concerns. We’re happy to talk over the phone or visit in person to provide more details about our work. We’re also committed to providing regular updates throughout the year, including presentations on initial results and future efforts, so please stay engaged to ensure you’re informed.

Thanks!

Mike Duncan

Region 3 Fisheries Manager

Mike.Duncan@mt.gov

(406) 577-7871