Big Hole Update: 2024 Research Finds Healthy Trout

There’s more positive news for trout in the upper Jefferson River drainage. Montana Fish Wildlife and Parks (FWP) recently released its 2024 Fish Study Results and of the nearly 12,000 fish looked at by FWP, “only three of them had issues that were obviously concerning,” Morgan Jacobsen, FWP spokesman said on a KPAX report. “And of the roughly 5,000 fish that we handled in tributaries, none of those had apparent infections that we could detect.”

According to a news release, FWP staff tagged brown and rainbow trout in the Big Hole, Beaverhead, Ruby and Madison rivers last year and relied on anglers to report tagged fish. 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. 

“We’re using angling as a way to measure how environmental factors like water flows and temperatures have an effect on trout mortalities,” Jacobsen said.

Less than 1 percent of the captured fish showed signs of infection.

FWP staff also counted 156 trout redds in the Big Hole River near Melrose last year, up from 108 redds in 2023.

“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, in the release. “We’ll continue to monitor trout health closely in 2025.”

In 2023, FWP data from the Big Hole River revealed the lowest recorded numbers of brown and rainbow trout since 1969. Brown-trout population issues were first noted across southwest Montana in 2021, but that data also showed a decimated rainbow trout population. The causes for these declines is unknown, but low flows and hot summers, agricultural runoff, and increased recreation of all been cited as possible factors.

These studies will continue in 2025 on the Big Hole, Ruby, Beaverhead, and Madison rivers, and FWP will add research on the upper Yellowstone drainage as well. The Yellowstone has also seen its share of hardships in the past decade including the revelation of proliferative kidney disease (PKD), the discovery of a smallmouth bass near the Yellowstone National Park boundary, and the June 2022 flood that took out Carbella Bridge.

In response to the trout declines, Save Wild Trout was formed to investigate the causes behind the decline in wild trout numbers and develop science-based solutions. Read more or donate to Save Wild Trout here.

Annual interim reports of the ongoing MSU studies study will soon be available on FWP’s website.

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