As drought deepens across Western rivers, a new web tool aims to tell anglers and managers where the next closures are coming before the water gets there. Called TroutCast, it launched June 1 and pulls together weather data, historic trout population counts, and streamflow records to forecast drought risk, population trends, and the likelihood of drought-related fishing closures on Montana’s blue-ribbon rivers.
The forecasts run in real time on the U.S. Geological Survey’s website. MidCurrent has tracked a record-low western snowpack heading into 2026 that has Montana’s freestone rivers bracing for low flows, warm water, and fishing restrictions weeks ahead of schedule. The same drought is forcing blunter calls elsewhere in the West: in Colorado, Denver Water has drained a reservoir and dropped its catch limits for an emergency fish salvage, the fish unlikely to outlast the summer.
How TroutCast Works
TroutCast is a collaboration among Montana State University, the USGS, Montana Fish, Wildlife and Parks, and NOAA’s National Integrated Drought Information System. It comes in two parts. A population tool gives one-year forecasts of trout numbers and shows whether a river’s fish are likely to climb, hold steady, or fall against recent trends; managers can use it to gauge how populations are responding to drought, compare conditions from one river to the next, and see where streamflow matters most for keeping a fishery productive. A management tool looks up to a month ahead at potential closures or hoot-owl restrictions that limit fishing at certain times of day, and points anglers and outfitters toward waters where conditions may hold. Built-in tutorials walk new users through both.
The underlying models came out of work by Timothy Cline, an assistant professor of cold-water fish ecology at Montana State, and scientists at the USGS Northern Rocky Mountain Science Center, with funding from NOAA and the USGS. The project set out to pin down how the reduced streamflows and warmer water that come with more frequent, more severe drought are tied to falling trout numbers across the West. Drawing on Montana FWP population records and USGS flow data, the team built age-structured population models that translate streamflow into forecasts of trout abundance and productivity. The central finding is that flow does most of the work. “What we’ve found is that it’s basically driven by streamflow,” Cline said. Water has always been understood as essential to trout, he noted, but until now no one had measured exactly how much it drives their production and abundance.
The effect can be dramatic. On the Ruby River, the team found about 384 trout per mile at a flow of 140 cubic feet per second — a number that could nearly double with another 20 cfs. A slider on the population tool lets users see that relationship for themselves.
Putting It Into Practice
Researchers and managers say the value is in turning flow and temperature data into decisions a manager can act on, supporting both the fisheries and the businesses that depend on them. Clint Muhlfeld of the USGS described it as a step toward proactive, science-based management; David Schmetterling, fisheries research coordinator for Montana FWP, said it improves how the state communicates trends in its fish populations, manages angling opportunities, and informs instream flows. Cline said the outfitters he has talked with are eager for a way to plan around drought rather than be caught out by it, and the tool is expected to help local and regional economies by sustaining recreational fishing through dry years. The multi-agency effort also feeds Montana’s Drought Management Plan, the USGS Integrated Drought Science Strategy, and NOAA’s national drought-information network, improving early warning for the people who manage water and fish.
The first version covers Montana, with planned expansion to the upper Snake River basin in Idaho and Wyoming and, eventually, other drought-hit Western states. TroutCast is available at usgs.gov/apps/troutcast/.
