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Fish health sampling last year found that an overwhelming majority of trout from rivers in the upper Missouri River Basin are healthy.
Fish health sampling was part of the field work for joint studies between Montana Fish, Wildlife & Parks and Montana State University that began in 2024. This work also includes fish tagging and creel clerk surveys. Angler participation has been key in these efforts and will continue to play a crucial role going forward.
Trout health
Fish health sampling and monitoring increased after trout with fungal infections and head lesions caught the attention of FWP staff and anglers in the years leading up to 2023.
Following recommendations from the Big Hole Fish Health Workgroup, extensive fish health sampling began in the Big Hole, Beaverhead and Ruby rivers. During spring and fall sampling, less than 1 percent of the captured fish showed signs of infection, and none of the nearly 5,000 juvenile fish that were captured in tributaries to those rivers showed signs of infection.
Of the nearly 8,000 adult trout that FWP staff captured in the fall, only three fish exhibited signs of an infection.
“It’s encouraging that almost all fish in last year’s sampling efforts in the basin appeared healthy,” said Mike Duncan, FWP’s fisheries program manager in Region 3. “We’ll continue to monitor trout health closely in 2025.”
FWP staff also completed a count of trout spawning redds in the Big Hole River near Melrose. They counted 156 redds last year, up from 108 redds in 2023.
Angler participation
FWP staff tagged nearly 12,000 brown and rainbow trout in the Big Hole, Beaverhead, Ruby and Madison rivers last year. To date, anglers have sent almost 1,300 reports of catching the tagged trout, including about 50 reports of yellow tags that are each worth a $100 reward.
Anglers who report catching tagged fish are helping biologists and MSU study trout population declines in parts of the basin. Fish managers can use angling and annual sampling as ways to measure how environmental factors like flows and water temperatures are affecting fish populations by species, age class, waterbody and time of year.
Each tag has a unique number and is attached to the fish near the dorsal fin. However, the tags may not be as vibrant or obvious to anglers who land a tagged fish in 2025 because of algal growth or exposure to other environmental conditions over the last year.
Anglers should use clippers to remove the tag from the fish, then submit a report online for each tagged fish they catch. Blue tag reports put anglers into drawings for prizes, and yellow tag reports are worth cash rewards.
Last year, about 3,599 anglers and recreationists took part in surveys to better understand all recreational use on rivers. Similar efforts will continue for several years and expand to include the upper Yellowstone River in 2025.
Montana Trout Unlimited held six drawings for anglers who reported catching tagged fish and recreationists who completed creel surveys. Multiple prizes were awarded in each drawing, including a guided fishing trip, artwork, clothing and fishing gear. Montana Trout Unlimited also held a grand prize drawing recently that included more than $1,000 in fishing gear to an angler who reported a tagged fish in 2024.
FWP staff will continue to tag trout and conduct surveys among anglers and other recreationists in 2025, and prize drawings will continue for members of the public who participate.
“Angler participation continues to be critically important to these studies that will help us manage for robust and healthy fisheries,” said Duncan. “We are thankful to Montana State University, Montana Trout Unlimited, anglers and prize donors for their collaboration.”
Annual interim reports of the ongoing MSU studies study will soon be available on FWP’s website. To learn more, go to: https://fwp.mt.gov/conservation/fisheries-management/trout-mgmt-sw-mt.