“We recognize that this decision will have a significant impact on many people. However, we must act to protect this public resource for present and future generations,” Hagener said in a press release.

Fishing and floating outfitters have been supportive of the closure so far, Jones said. But how long that support would last in the face of a lengthy closure is still to be seen.

"A threat to the health of Montana's fish populations is a threat to Montana's entire outdoor economy and the tens of thousands of jobs it sustains," said Gov. Steve Bullock, noting that Montana's outdoor recreation economy is responsible for more than 64,000 Montana jobs and nearly $6 billion in yearly economic activity. "We must be guided by science. Our state cannot afford this infectious disease to spread to other streams and rivers, and it's my responsibility to do everything we can to stop this threat in its tracks and protect Montana jobs and livelihoods."

Bailey said there were few customers in his downtown Livingston store on Friday, and the upcoming Labor Day weekend is traditionally one of the busiest times of the year.

"It's very unprecedented," he said. "I'm not against this, but we don't know when it will end."

Bailey noted that stream flows won't increase until next spring.