Anglers looking for trophy-sized grayling might want to rethink heading to Rogers Lake for the time being, since state wildlife officials are investigating a disease outbreak affecting the popular fishery southwest of Kila.

Mark Deleray, the regional fisheries manager for Montana Fish, Wildlife and Parks, said his office first began getting calls about dead grayling washing up on the shore about three weeks ago.

He described the illness as a “white fungus” that only seems to be affecting large spawning-age grayling. No other fish in the lake have been affected, and Deleray said he isn’t aware of any human health risks from the diseased fish.

“That type of outbreak usually occurs when the fish are stressed,” he said. “Last year we had a very warm summer, so water temperatures were high in the lake. It’s quite possible the fish were stressed last summer, then went into the winter in much poorer condition than normal.”

He brought in a fish health specialist from Great Falls two weeks ago, but still is waiting on the lab results to figure out the cause of the outbreak.

“We’re watching it, we’re well aware of it, and I think at this point we’ve done everything we can do,” he said.

It’s not the first time this type of outbreak has occurred in the region, but Deleray wasn’t aware of any significant die-offs of grayling in recent years.

Rogers Lake contains substantial cutthroat and grayling populations; the latter are regularly stocked by the state’s fish hatcheries in Somers and on Rose Creek.

State biologists don’t expect the outbreak to have any long-term impacts on the fishery, Deleray said, adding that bald eagles seem to be enjoying the easy meals washing up on the shoreline.

“There’s literally thousands of grayling in Rogers Lake, so a minor mortality level will not damage the population in the long run,” he said. “The concern is more that this might be shaping up to be another hot, long summer, so it may again be a stressful year.”

Reporter Sam Wilson can be reached at 758-4407 or by email at swilson@dailyinterlake.com.