Two conservation groups are petitioning the Montana Department of Environmental Quality to designate the Big Hole River, a treasured southwestern Montana fishery, as impaired for nutrient pollution.
The groups argue that an impairment designation will lead the state to put the Big Hole on a “pollution diet” to limit the nitrogen and phosphorous that are contributing to the fishery-damaging algal blooms that have become a recurrent issue.
Common sources of nutrient pollution runoff from fertilizers, insecticides and herbicides as well as poorly maintained septic systems and manure from livestock.
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Upper Missouri Waterkeeper and the Big Hole River Foundation are basing their petition on five years of data collection that has found consistently high levels of nitrogen and phosphorus at multiple sites on the Big Hole. The groups also incorporated a macroinvertebrat, or bug, study and an overview of the state and federal laws governing the beneficial uses of waterways in their petition.
“There’s no disputing that there’s a nutrient pollution problem on the Big Hole River, with neon-green algal blooms fueled by nutrients cropping up each summer,” Upper Missouri Waterkeeper Executive Director Guy Alsentzer wrote in a release Wednesday about the petition. “Thankfully, the State of Montana has the tools to restore rivers impaired by nutrients, like the Big Hole. We now need to hold the State accountable for taking the necessary steps to designate the river as impaired, develop a pollution diet, and work to reduce pollutant sources that are causing degradation.”
Overgrown algae can , harming fish and some of the macroinvertebrates they eat. In some areas, an increase in algae is and diminished ecological resilience.
The petitioners would like the DEQ to acknowledge that portions of the Big Hole are exceeding established water quality thresholds, recognize they “are not fully attaining their aquatic life or recreational uses” and designate the waterway as impaired for nutrient pollution. The petition also notes the historically low flows, high water temperatures, and declining fish populations the Big Hole has seen in recent years.
The comes as anglers and researchers attempt to understand the factors contributing to a marked decline of trout populations in a handful of cold-water fisheries in the Jefferson Basin.
In 2023, FWP biologists recorded . Anglers and conservationists floated a number of possibilities that may be contributing to the decline, ranging from pathogens and drought conditions to angling pressure and unmitigated pollution. Save Wild Trout, a nonprofit formed in 2023 to understand which factors merit further investigation, has described the 2023 southwestern Montana fishery “collapse” as a “canary in the coal mine moment.”
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Save Wild Trout members are hopeful that a nimble, privately funded effort will help state biologists determine what’s driving down trout populations. The group says parts of the Big Hole River, an iconic fly-fishing destination, are suffering historically low counts for rainbow and brown trout.
Wade Fellin, a longtime fishing guide who serves as Save Wild Trout’s program director, described the impairment designation petition as part of his group’s larger effort to help the Big Hole recover from chronic and acute threats.
“The Big Hole is suffering blow after blow — extremely low flows prompting mid-season fishing closures, and miles-long algal blooms,” Fellin said in the release. “We must do what we can now to make measurable improvements for the river, and that should start with an official impairment determination to clean up the nutrient pollution that is degrading water quality and aquatic habitat.”
A spokesperson for DEQ wrote in an email to MTFP on Wednesday that “nutrient conditions and other algae growth factors appear to be at levels conducive for algae growth in the Big Hole River and several of its tributaries.”
The agencies noted that it has been monitoring algae levels on the Big Hole since 2020 and that streamflows and temperatures play an important role in both overall fishery health and algae growth.
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Under existing law, DEQ is required to provide an initial determination on the petition within 60 days, although Montana lawmakers are debating a bill by , that would stretch the agency’s response time to 180 days. passed through the House last month and cleared an initial Senate vote on Wednesday.
In response to the 2023 population slump, Gov. Greg Gianforte rivers that Montana Fish, Wildlife and Parks is coordinating with Montana State University.
Researchers are just embarking on the second year of that research, which will continue for at least three years, according to FWP spokesperson Morgan Jacobsen.
One component of that research is examining how flows, water temperature, angling and disease may be contributing to adult fish mortality. A second prong will evaluate tributaries’ contribution to the recruitment of juvenile fish into the adult population. Finally, FWP is examining disease threats with the hope of developing a way to proactively support fish health.
To facilitate that research, biologists have tagged trout in the Big Hole, Ruby, Beaverhead and Madison Rivers. FWP is asking anglers who catch a tagged trout to to aid researchers.
Last year, biologists noted on the Big Hole compared to 2023. Both species are still . Jacobsen said the 2025 counts are currently underway and estimated that data from those surveys should be available in about a month.
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