Fish in rivers throughout Southwest Montana are declining at a rate that Big Hole River Fisheries biologist Jim Olsen says he hasn't seen in a long time.
"Usually this is something we see at the end of July, August kind of time period when our flows finally get really low and temperatures are warm -to see these closures go into effect in June is... since we’ve had these kinds of closures, we’ve never had it this early before," said Olsen.
The fish mostly affected by the high temperatures are trout.
"Trout, in general, are a cold water species specialist so they need cold water," said Olsen.
As water temperature rises, water itself can’t hold as much oxygen and the trout are not able to use it effectively because they’ve adapted to being in colder water. The high temperature causes stress.
The lethal limit for trout is just over 80 degrees.
"We’re seeing temperatures like that in some of our trout rivers now where they’re actually reaching 80 degrees so that’s the upper limit where they’re going to die," said Olsen.
Craig Jones, Owner of Great Divide Outfitters, said that businesses rely on the fishing season for work.
"Every small business that operates on any of these major rivers is driven by the fishing by bringing people in out of state. . .the bars, the restaurants, the hotels, the airbnbs, everybody is gonna feel an impact if this fishery keeps heading the way it’s heading," he said.
Jones said that fishermen can help ease the stress on fish.
"Barbless hooks, catch and release, no treble hooks, and no bait fishing, and right now in this river we’re obviously seeing a decline in all of our species and the fishermen are part of it and so we need to make sure that we’re doing our part to help and to fix it to hopefully turn it around in the future," said Jones.
Montana Fish, Wildlife and Parks are asking residents to avoid using the big rivers, instead looking to creeks, reservoirs and lakes.
"Our fish numbers are already way down in the river and then we throw this kind of event on top of them, it’s not going to be good," said Olsen.