Montana officials found more dead whitefish on the Yellowstone River on Thursday, but so far they aren’t finding anywhere near the number they saw a year ago.
Travis Horton, the regional fisheries manager for Montana Fish, Wildlife and Parks, said his staff found 18 dead whitefish and one that was dying during a float from Mallard’s Rest to Pine Creek on Thursday. Staff found 76 dead whitefish downstream of Livingston earlier in the week.
They can’t be certain they’re seeing all the dead fish, since scavengers often pick them up, but what they are seeing is still far fewer than what they saw in August 2016. Last year, a microscopic parasite combined with low streamflows and high water temperatures caused a major die-off of mountain whitefish. At one point last year, staff floating the same stretch they floated Thursday counted about dead 2,000 fish on one side of the river.
They still can’t say for sure whether the fish are being killed by the same parasite. Tissue samples were sent to the U.S. Fish and Wildlife Service’s fish health lab in Bozeman to try and determine a cause. Results are expected back next week.
But Horton said that while they aren’t seeing the same number of fish die, they are seeing the same species die as they did last year — mostly mountain whitefish, a few long-nosed suckers and a single brown trout.
“It sure has a lot of similarities to last year,” he said.
In response to last year’s kill, FWP shut down recreation on 183 miles of the river. Horton said that with the low number of fish they’ve found so far this year they haven’t even talked about that possibility yet.
“It’s not on the radar at this point,” he said.
FWP hadn’t found a significant group of dead fish on the Yellowstone until this week. River conditions are better than last year, with above average streamflows and water temperatures that stayed below 70 through the summer. Biologists have also said host organisms for the parasite were washed downstream during high flows this spring.
Horton said they sent a crew to look for dead fish this week after receiving two reports of about a dozen dead fish downstream of Livingston.
On Tuesday, staff found 52 dead whitefish from the Highway 89 Bridge to Springdale. They floated from Springdale to Grey Bear Fishing Access Site on Wednesday and saw another 24 dead whitefish. They also found one dead brown trout and two long-nosed suckers over those two days.
They chose the Mallard’s Rest to Pine Creek section on Thursday because that stretch was hit hardest by the kill in 2016. In addition to the whitefish, the crew also found a single long-nosed sucker.
A coup for FWP on Thursday was the capture of a moribund fish — one that is dying but hasn’t died yet. Horton said tissue from a dying fish is helpful in identifying what is killing the fish. Once they get the tissue under a microscope, they can actually see whether a parasite is present.
“If they’ve died, its too late,” he said.
A crew will float below Livingston again on Friday.
