One Fish, Two Fish

Fish populations help track water quality

GALLATIN RIVER TASK FORCE

She walks calf-deep through the creek, following her rod in the hopes it will lead her to a healthy trout hidden in the West Fork’s cold riffles. Today, there’s no hook at the end of her line and no reel in her hand. Instead, she wields an electrofisher that conducts a weak electric pulse, and she’s shocking trout into her partner’s net. 

This volunteer is assisting a team of biologists hoping to establish baseline fisheries data on Gallatin River tributaries, tracking species composition over time and impacts from climate change, development and shifting angler pressures.

The fish count is being conducted under the leadership of Montana Fish, Wildlife and Parks, and agency fisheries biologist Mike Duncan is happy with what he sees. 

“This is standard to what we see on streams of similar size,” Duncan says. “Nothing surprising, and that’s encouraging.” 

Given 2021’s lack of precipitation, high temperatures and low stream flows, conditions could have been a lot worse, but this is why accurate monitoring is so vital. Decisions can’t be made on anecdotes alone.

“Having baseline data is critically important,” says Connor Parrish, Trout Unlimited project manager with the Gallatin Home Rivers Initiative. “If we aren’t out there collecting, how will we know when things are going wrong?”

This is a sentiment long held by the Gallatin River Task Force’s Chief Executive and Science Officer Kristin Gardner. “Our project work has always been data-driven,” Gardner says. “Fisheries data combined with our water quality and quantity data will provide us with a better understanding of how to best respond and prioritize our future conservation projects.”

In many ways, the species composition of the Gallatin and its tributaries can act as the canary in the coal mine—or brown trout in the West Fork, as it were. 

“Over time, we’ll be able to look at the changes in fish assemblages, and identify potential causes,” Duncan says. “Water use is a big change—more people use more water.”

As Big Sky continues to grow and visitation continues to increase, stream flows in tributaries will be impacted. Lower stream flows lead to higher water temperatures, and certain trout species do better as temps increase, such as browns.

Which isn’t to say that brown trout are a bad thing. If, however, their numbers increase in the upper Gallatin while cutthroat and rainbow numbers dwindle, it could signal unfavorable changes to water quality that will need to be addressed.

With only one data point to draw from, this collaborative monitoring effort is just getting underway. The partners will need time to collect more samples and begin analyzing results, but it is a promising sign of increased awareness and collaboration. 

“To ensure the Gallatin is healthy and that our fisheries remain vibrant, we’re going to need to pool resources, human, financial and otherwise,” Gardner says. “The more partners and stakeholders at the table, the more likely we are to succeed.”