Big Hole: Trout numbers better than last year but still below average

  • DUNCAN ADAMS Montana Standard
  • 50 mins ago


Montana Fish, Wildlife & Parks Conservation Technician Lucas Bateman nets a fish while performing an electrofishing survey on the Big Hole River in April. 

  • JOSEPH SCHELLER/The Montana Standard


Montana Fish, Wildlife & Parks’ Jim Olsen, Lance Breen and Anthony Zenga perform an electrofishing survey on the Big Hole River in April. 

  • JOSEPH SCHELLER/The Montana Standard

Montana Fish, Wildlife & Parks Fisheries Technician Lance Breen, left, tags a trout while conducting an electrofishing survey on the Big Hole River with FWP’s Jim Olsen, Lucas Bateman, and Anthony Zenga in April. 

  • JOSEPH SCHELLER/The Montana Standard

Montana Fish, Wildlife & Parks Conservation Technician Lucas Bateman attaches a tag to a trout while conducting an electrofishing survey on the Big Hole River in April. 

  • JOSEPH SCHELLER/The Montana Standard

A great hue and cry produced a prodigious splash last year — like a burly brown trout pursuing a salmonfly. The fuss and fuming focused on trout populations declining since 2011 in the nationally acclaimed Big Hole River. 

In May 2023, more than 30 fishing outfitters and guides in Montana beseeched Gov. Greg Gianforte to move swiftly to harness state resources to help understand the how and why of waning trout populations in the river.

More than two months later, Gianforte convened a roundtable discussion in Wise River that included fishing guides, irrigators, agriculture producers and biologists. People with ag interests dominated the crowd at the community center.  

On Wednesday, Gianforte returned to the Wise River area to receive an update from Jim Olsen, a fisheries biologist for Montana Fish, Wildlife & Parks whose territory includes the Big Hole River. FWP Director Dustin Temple was also on hand.

There was good news and so-so news. A press release Thursday from the governor’s office emphasized the former.

The good news focused on electrofishing sampling this spring by Olsen and his crew that found a general increase in juvenile fish, an indication of improved recruitment of the younger fish that might someday become bigger fish.

The so-so news was that in all four sections of the river that were sampled the numbers of brown and rainbow trout remained well below long-term averages. In some sections, including Hogback and Pennington, rainbow trout numbers had declined, either since sampling last year or from sampling completed in 2021.  

In the river’s Melrose section, estimates in 2024 suggested 506 brown trout per mile. That was up from a 2023 estimate of 324 brown trout per mile but well below the 908 per mile long-term average for that stretch.

In the Jerry Creek section, brown trout were an estimated 710 per mile, the best tally since 2015 and up from the 422 count in 2023. Yet that lagged the long-term average of 749 per mile.

Rainbow trout numbers in the Jerry Creek section improved from an estimated 498 per mile in 2023 to 779 per mile in 2024. Yet the long-term average in this stretch is an estimated 1,606 per mile.

In the Hogback section, which runs from the Glen Fishing Access Site to the Tony Schoonen Fishing Access Site, biologists found an estimated 268 rainbow trout per mile and 722 brown trout per mile. Rainbow trout numbers decreased slightly from 2023’s estimate of 288 fish. Brown trout estimates, however, more than doubled from last year’s estimate of 289. The long-term averages for this section are 473 rainbow trout per mile and 920 brown trout per mile.

Olsen has said that good water levels in 2023 likely helped improve the survival of juvenile trout because most of the population increase observed this year was in 2-year-old fish.

“While trout populations are still well below the long-term average, this year’s estimates so far are encouraging,” Olsen said earlier this year.

Not counting chickens

Wade Fellin, an outfitter, co-owner of the Big Hole Lodge and a co-founder of the nonprofit Save Wild Trout, responded to the numbers.  

“Seeing incremental increases in wild trout populations is certainly something to celebrate, however, we aren’t going to count the chickens before they hatch,” Fellin said. “FWP biologists have done a tremendous job laying out and beginning necessary studies to identify what’s affecting trout populations but they can’t build resiliency into our waterways alone. Healthy cold-water fisheries that sustain robust wild trout populations need biological, physical and chemical balances to thrive.”

Fellin said the Big Hole River and many other blue-ribbon waterways face persistent pollution above allowable levels which, when mixed with warmer temperatures driven by climate change, are creating an unnatural mix he said is unsustainable for fishery health.

“The state of Montana still needs to address these underlying issues,” he said. “Save Wild Trout and the Big Hole River Foundation are collecting valuable water chemistry and macroinvertebrate data to help inform protection of these rivers.”

The Big Hole River Foundation has been collecting water quality data on the Big Hole for several years. The Montana Department of Environmental Quality approved the nonprofit’s sampling and analysis plan in 2020.

Brian Wheeler, the foundation’s executive director, has put a lot of miles on his pickup to collect water samples along the Big Hole.

He said DEQ’s “total maximum daily loads” for the river consider temperature, sediment, nutrients and heavy metals as potential pollutants.

“In addition, dissolved oxygen is a very important parameter for aquatic life, which, like nutrients, hasn’t been documented until recently with the Big Hole River Foundation pilot project last year — and full DEQ approval this year — and the huge effort by Save Wild Trout to document dissolved oxygen throughout the Jefferson Basin this year,” Wheeler said.

Disease questions remain 

Olsen shared data about fish numbers and health during the May 15 meeting of the Big Hole Watershed Committee in Divide.

In recent years, observers of trout health in the Big Hole have shot photos of the coldwater fish showing fungus or head lesions.

Fungus is not unusual, Olsen said.

“The stuff on the head is something we don’t fully understand,” he said. “But we really have a good group of people right now who are willing to help us understand the disease issue.”

He emphasized that the key driver of a healthy trout population is keeping an adequate flow of water — especially cold water — in the river.

During low water years, and 2024 seems destined to be one, tensions often escalate between ranchers who irrigate hayfields to feed cattle during the Big Hole Valley’s long winters and outfitters and guides who count on summer bookings to make a living.

Watching the river flow 

The Natural Resources Conservation Service has forecast that the Jefferson River Basin will have about 50% to 60% of normal streamflow through July.

When flows drop and temperatures increase, FWP often closes stretches of the river to fishing because angling can have negative impacts on already stressed fish.  

Last year, Eileen Ryce, then the agency’s fisheries division administrator, addressed the flow conundrum.

“Trout populations in many streams in southwest Montana have seen decline in recent years, and research continues to point to perennially low stream flows and high water temperatures as contributing factors,” Ryce said then.

Last month, without explanation, Ryce was put on administrative leave.

FWP and Montana State University launched a cooperative research effort after annual sampling found fish numbers to be at or near historic lows in sections of the Big Hole, Beaverhead and Ruby rivers last year. This partnership included hiring PhD students and additional staff to study fish mortality, recruitment and health.

Spring population sampling found similar patterns in the Beaverhead and Ruby rivers, with numbers generally but not uniformly better than last year but still below long-term averages.

This spring, FWP staff tagged fish in the three rivers, as well as the lower Madison River. Anglers reporting tagged fish can help researchers identify individual fish and monitor their health, survival, movement and other indicators over time. Anglers submitting reports could also be eligible for rewards.


Meanwhile, there were complaints this spring from some outfitters and guides who believed negative publicity last year about declining trout populations had been overwrought and had affected their businesses. 

Many said fishing during the summer of 2023 was generally good. 

Outfitter Shaun Jeszenka, owner of Frontier Anglers in Dillon, said negative publicity created an unduly downbeat impression of fishing conditions in the Jefferson River Basin. 

On Thursday, with the salmonfly hatch underway, Jeszenka was out guiding clients. But Steve Wilson, shop manager at Frontier Anglers, said fishing experiences this month have reflected the more upbeat population estimates. 

“People are catching a lot of healthy, big fat browns,” Wilson said.