This Sunday, 21 August 2016, photo shows dead whitefish floating in the Yellowstone River near Emigrant, Montana. Montana wildlife officials closed a stretch of the river and numerous tributaries after a massive fish kill that is blamed on the contagious parasite Tetracalsula bryosalmonae. Photo: Matthew Brown / AP

By Sarah Jane Keller
25 August 2016

( – It was the kind of clear late-August day that anglers live for. Yet at the Yellowstone River near Livingston, Montana, not a single oar boat or even a fishing line broke the river’s calm surface. All was still, save for an osprey scavenging the corpses of pale, shimmering whitefish along the gravelly shoreline. A light breeze carried the sweetish smell of aquatic decay.

Earlier this month, the Yellowstone River made national headlines with the news of an unprecedented fish die-off in its usually healthy waters. Starting in mid-August, biologists counted 4,000 dead whitefish floating on the Yellowstone or washed ashore, but they estimate that the true number is in the tens of thousands. As if that wasn’t enough, they’ve recently spotted rainbow trout and Yellowstone cutthroat trout—both economically important species—go belly-up as well.

This devastating scene has state officials so worried that, on August 19, they closed a 183-mile stretch of the river and all of its tributaries until further notice. Fishing boats, inner tubers, even swimming dogs: none are allowed to get into the water.

The culprit is a tiny, highly contagious parasite called Tetracalsula bryosalmonae, which exclusively attacks fish. It worms its way into fishes’ kidneys, where it causes proliferative kidney disease and can obliterate fish populations, according to state biologists. (Science writer Ed Yong explains how this scientifically elusive parasite evolved from a jellyfish-like creature at The Atlantic.)

Those biologists note that it’s been a hot summer, and streamflows have been historically low—stressful conditions that make cold-adapted fish populations ripe for a deadly disease outbreak. The river closure is meant to keep the parasite out of other rivers and to keep fishers and boaters from further taxing sick fish. […]

News of the whitefish kill didn’t surprise Clint Muhlfeld, a U.S. Geological Survey aquatic ecologist and University of Montana researcher who studies climate change impacts on cold-water ecosystems. “We’re seeing severe impacts on Montana’s waters, mainly increases in stream temperatures and decreases in flows. These climate-induced changes are likely going to begin to interact with existing stressors such as habitat loss and invasive species,” he says. “The climate is warming, and there are going to be consequences for our freshwater ecosystems.” [more]

The Massive Yellowstone Fish Die-Off: A Glimpse Into Our Climate Future?



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