State: Major fish kill not expected on Yellowstone this year

Source: Bozeman Daily Chronicle
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By Michael Wright

Montana officials don’t expect to see a significant fish kill on the Yellowstone River this year after a heavy winter and good flows.

Eileen Ryce, the fisheries division administrator for Montana Fish, Wildlife and Parks, told the state’s Fish and Wildlife Commission Thursday that high spring flows washed out a sponge-like organism that serves as a host for the parasite that killed thousands of mountain whitefish in the Yellowstone last August. With fewer hosts available for the parasite, Ryce expects the fish to get through the year mostly unscathed.

“I think we’re going to get through the year without any major events,” Ryce said.

Dead mountain whitefish first started turning up in large number on the Yellowstone at this time last year. FWP confirmed that a microscopic parasite that causes proliferative kidney disease was to blame. Tens of thousands of fish went belly up, many of them rotting on the banks.

The state responded by closing 183 miles of the Yellowstone River and all of its tributaries to all recreation as a way to give the fish a chance to survive and reduce the risk of spreading the parasite to other rivers and lakes. After nearly two weeks, the state began to reopen the river piece by piece. It was more than a month before the full river was opened again.

Outfitters and business owners throughout the Paradise Valley lost money because of the closure, and they worried the whole ordeal might come back again this year. The parasite has killed fish in five consecutive years in Idaho’s upper Snake River drainage, albeit in smaller number each year.

It hasn’t happened so far on the Yellowstone, and biologists say that’s because the river conditions are much better. Low flows helped the parasite thrive and pound the whitefish population in 2016, but this year, flows are significantly higher.

The river basin saw good snows through the winter, and the flows have stayed high through the summer. On Thursday afternoon, the Yellowstone was running at 4,400 cubic feet per second at Livingston — a number that’s roughly 500 cubic feet per second above average.

“We’re much better than we were condition-wise last year at this time,” Opitz said.

That combined with days getting shorter and nights getting longer — which helps keep water temperatures low — gives FWP some confidence that a massive kill won’t happen again this year.

But Opitz and FWP are still keeping watch. Opitz floated the river last week and didn’t see any dead fish. He said there’s certainly potential for another kill, but he doesn’t expect it to be near the magnitude that was seen in 2016.

Biologists have also responded to reports of dead fish on other streams around the state, but they haven’t seen anything abnormal.