Fish kill in Montana's Big Hole River blamed on fungus

MELROSE, Mont., Oct. 16 (UPI) —

Dozens of trout in Montana are dying and floating lifelessly onto the banks of the Big Hole River. The culprit is a fungus called Saprolegnia, and although the uptick in dead fish have local fly fisherman a bit concerned, wildlife officials say it’s business as usual.

"It’s not like whirling disease or some new unknown pathogen has shown up there," Travis Horton, a fisheries manager with Montana Fish, Wildlife and Parks, told the local paper Ravalli Republic. "This is not a cause for alarm."

Saprolegnia, Horton says, is commonly found in almost every freshwater stream and river in the state of Montana. But why is it proving deadlier than usual? Horton and other officials aren’t entirely sure.

"We have pretty high densities of brown trout right now," Horton said. "Brown trout are spawning and so they are stressed as they fight and dig around to build their redds."

Redds are the name for nests, which female trout dig in the riverbed gravel with their tails.

Although Saprolegnia does cause visible symptoms, sometimes causing an infected fish to become covered with white or gray fibrous patches, the real damage is done by weakening the immune system, making the trout more susceptible to other illnesses.