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Southwest Montana Trout Populations Continue Alarming Decline

The Big Hole, Ruby, Beaverhead, Jefferson, and Clark Fork rivers are seeing severely reduced trout populations. Where are the Montana officials and agencies?

Southwest Montana Trout Populations Continue Alarming Decline

New data reveals the lowest recorded numbers of brown and rainbow trout in the Big Hole River since 1969, with a 61-percent decline over the past decade. (Photo courtesy of Wade Fellin/Big Hole Lodge)

UPDATE, 6/8/2023: The Montana Fish Wildlife and Parks (FWP) Fish and Wildlife Commission has responded to requests for action on the trout declines in the Jefferson River drainage by approving new regulations for the Big Hole, Beaverhead, and Ruby rivers. Click here to see a full list of the new laws, which go into effect immediately.


The Big Hole and other southwest Montana rivers are facing an ongoing decline in their trout populations, and guides, outfitters, fly-shop owners and anglers are expressing grave concerns about the worsening situation.

Montana Fish Wildlife and Parks (FWP) data from the Big Hole River reveals the lowest recorded numbers of brown and rainbow trout since 1969. Brown-trout population issues were first noted across southwest Montana in 2021, but the recent data also shows a decimated rainbow trout population.

“I’m very concerned," Jim Olsen, the FWP Fisheries Biologist in charge of the Big Hole drainage, said in a KXLF news story. "It’s because A, the whole population is low, and B, we have very few small fish. So, the prognosis for next year and the coming years is not very good.”

A blog post by the Big Hole River Foundation (BHRF) corroborates that the combined population of brown and rainbow trout in the Big Hole has plummeted by an alarming 61 percent over the past decade. Similar trends are also being seen on the Beaverhead, Ruby, and Jefferson rivers (the Big Hole combines with the Beaverhead and Ruby to create the Jefferson). Click here to jump down to graphics for these rivers.

“An apparent bureaucratic shift away from prioritizing research and towards a focus on ‘customer service’ has resulted in the inability to provide the data and support needed to ensure healthy ecosystems,” according to a portion of the BHRF post.

Nutrient pollution from agricultural runoff has been identified as a potential factor in the decline. Eutrophication (excess nutrients which cause dense plant growth and lead to fish kills due to lack of oxygen), from elevated levels of nitrogen and phosphorus attributed to agriculture and natural phosphorus mines, have also been documented in the river over the past three years. These pollutants, along with dewatering, low-water years, rapid growth and development, climate change, and increased recreational pressure are believed to be culprits.

These factors can also heighten the impacts of proliferative kidney disease (PKD), which was behind 2016’s Yellowstone River whitefish die-off. PKD impacts fish respiration, reproduction, and growth.

Since brown trout are considered relatively hardy and tolerant compared to rainbows, brookies, and cutthroats, and because the other species have not simply moved in to fill the void left by the missing brown trout, BHRF believes that a disease or diseases such as PKD are also likely factors.




Five large sick and dead brown trout laying on the bottom of a boat.
BHRF believes that a disease or diseases are also likely factors in the recent trout population declines. (Photo courtesy of Montana FWP)

"FWP moved with some urgency (on the 2016 Yellowstone fish kill)," Steve Luebeck, Vice President of the George Grant Chapter of Trout Unlimited (GGTU), said in a recent article in the Montana Standard newspaper. "They got samples, they got them analyzed, they diagnosed the problem. They fixed it. There does not seem to be the same level of urgency on the Big Hole. They took samples in the river last fall. It's May. Where's the data?"

Another survey conducted this spring on the nearby (but separated by the Continental Divide) upper Clark Fork River found a mere 25 trout per mile, when a decade ago there was thought to be upwards of 2,000 trout per mile. The cause here is also not fully understood, but this upper portion of the Clark Fork is within a large Superfund site which has caused significant damage in the past.

In this case, FWP officials believe climate change causing increased water temperature and drought, metals contamination from past mining operations, declines in recruitment, dewatering, recent fish kills (including a 2019 event in which fisheries biologists found more than 30 dead trout in this narrow section, attributed to mine waste), low levels of dissolved oxygen, and unknown diseases are behind these incredibly low numbers.

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FWP also reportedly noted a decrease in natural reproduction on these fisheries, which could mean the worst is yet to come.

To address these issues, local outfitters, guides, fly-shop owners and others have drafted a letter hoping to compel state officials, most importantly Governor Greg Gianforte, to take urgent action and develop a comprehensive plan. Prompt sampling, analysis, and problem diagnosis, they say, are crucial. However, even if the immediate challenges are resolved, there is a need for continued monitoring and efforts to sustain the river's health. Click here to view the full letter.

“Clean, healthy rivers and vibrant wild fisheries are part of our unique Montana way of life,” said a statement in the letter. “They are also critical to Montana’s outdoor economy, which accounts for $7.1 billion in consumer spending and supports more than 71,000 jobs.”

Impacts of climate change, such as reduced trout habitat, rising air and water temperatures, reduced and fast-melting snowpack, and severe wildfire seasons also loom large on Montana’s landscape. Population declines in Montana's native bull and cutthroat trout have already been linked to climate change, but no official study has been conducted on the rainbow and brown trout since they are not native.

Additionally, the absence of long-term data from FWP on native whitefish populations, which are an indicator species, has also been criticized. Collecting such data could provide valuable insights into the broader issues affecting the Big Hole River and other rivers in the region.

A mountain whitefish with blood on its side in a landing net
The absence of long-term data from FWP on native whitefish populations has also been criticized. (Photo courtesy of Wade Fellin/Big Hole Lodge)

"We depend on the state to ensure that a clean and healthful environment is proactively maintained on our behalf, as is explicitly afforded us in the State Constitution," BHRF executive director Brian Wheeler said in the aforementioned newspaper article.

“It’s time to stop pointing fingers and start addressing the problem, before it’s truly too late,” added Guy Alsentzer, Executive Director of the Upper Missouri Waterkeeper (UMW). “The State of Montana has a legal obligation and moral responsibility to protect the public trust in healthy rivers and cold-water fisheries. Sitting on its hands, ignoring the requests from thousands of Montanans, and failing to take action is a violation of the public trust and a major blow to Southwest Montana’s $167 million outdoor economy, thousands of local jobs, and dozens of local businesses that depend upon clean and healthy fisheries.”

UMW lead the 2021 charge in demanding that Governor Gianforte create a “Cold Water Fisheries Task Force,” which has thus far fallen on deaf ears.

"So just as we've seen with the impacts on our forest–beetle kill, fires–the EPA predicted significant declines (in Rocky Mountain trout populations) by 2030," Professor and author Pat Munday told the Standard. "So I think in some ways we're seeing those kinds of predictions about climate come true."

A dead trout in a Montana trout stream.
A dead brown trout on the Big Hole. (Photo courtesy of Wade Fellin/Big Hole Lodge)

Click here to urge Montana Governor Greg Gianforte to take action to save Montana’s trout.

Click here to contact FWP about this issue.

Click here to read a recent report presented by FWP to the GGTU on this dire situation.

Click here to support the Big Hole River Foundation.

Click here to support the George Grant Chapter of Trout Unlimited.

Click here to support the Upper Missouri Waterkeeper.

See below for a message from the Big Hole Lodge's Wade Fellin:

 
 
 
 
 
View this post on Instagram
 
 
 
 
 
 
 
 
 
 
 

A post shared by BIG • HOLE • LODGE (@bigholelodge)

Addendum: Fish Population Graphs

A graph showing declining trout numbers.
(Graphic courtesy of Montana FWP)
A graph showing declining trout numbers.
Trout numbers over time on the Melrose section of the Big Hole. (Graphic courtesy of Montana FWP)
A graph showing declining trout numbers.
(Graphic courtesy of Montana FWP)
A graph showing declining trout numbers.
Trout numbers over the years on the Beaverhead River. (Graphic courtesy of Montana FWP)
A graph showing declining trout numbers.
Trout numbers over the years on the Ruby River. (Graphic courtesy of Montana FWP)

Joshua Bergan, Fly Fisherman's digital editor, lives in Belgrade, Montana with his wife Liz, kiddo Thomas, and dogs Mika and Koda. If you would like to share newsworthy fly-fishing related information, please e-mail him here.

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