When thousands of fish washed up on the banks of the Yellowstone River in August 2016, it didn’t go unnoticed. That’s because people’s livelihoods in this part of Montana depend on the river and fish. A short film about the die-off, Trout County, was released by the Sierra Club on April 24.

The whitefish died of toxic shock syndrome and kidney disease brought on by a parasite that thrives in warm water. The Yellowstone’s cold, clear water was warmer than usual that year, in part due to low snowpack attributed to climate change.

Dan Vermillion of Sweetwater Travel Co. is the outgoing chair of the Montana Fish and Wildlife Commission. He was the one who made the call, with input from Governor Steve Bullock, to shut down a 200-mile stretch of the Yellowstone to recreation for three weeks that year. It cost the local economy — guides, restaurants, lodges — more than $500,000.

“It’s hard telling your buddies, ‘You can’t go to work today,’ ” he says. “The impact on the economy was drastic.”

Trout County explores the intertwined nature of the environment and the economy as locals grapple with the immediate and long-term impacts of climate change. The fishery rebounded, and communities are collecting water-quality data that could help shape solutions.

The free, 15-minute film is part love letter to the Yellowstone River, part cautionary tale of fishing in a warmer world. Trout County is posted below.