Tens Of Thousands Of Fish Die In Yellowstone River, Prompting Authorities To Close It Down

Dead Whitefish in Yellowstone River

One of tens of thousands of dead whitefish found floating in the Yellowstone River. Hunter D'Antuono/AP/Press Association Images

Officials from Montana Fish, Wildlife and Parks announced that they have closed a 183-mile (294-kilometer) stretch of the Yellowstone River amid an ongoing die-off of tens of thousands of fish. The mass mortality event, thought to be caused by a parasite that infects the fish, means that all river-based activities – including fishing, wading, and boating – will be banned for the foreseeable future in an attempt to limit the spread of the disease and protect the fisheries.

The deadly organism is thought to be Tetracapsuloides bryosalmonae, a type of myxozoan parasite. It is a major parasite for fish such as trout, char, and whitefish, and can cause serious problems for fisheries. The parasite itself doesn’t directly kill the fish, but it does cause them to develop proliferative kidney disease (PKD), and with a mortality rate of up to 90 percent, it has been behind massive die-offs in other regions of the state, as well as in Canada and Europe. The worry here is that it will have a lasting impact on the reputation of the Yellowstone River as a world-class trout fishery.


“A threat to the health of Montana's fish populations is a threat to Montana's entire outdoor economy and the tens of thousands of jobs it sustains,” said Governor Steve Bullock in a statement. “We must be guided by science. Our state cannot afford this infectious disease to spread to other streams and rivers and it's my responsibility to do everything we can to stop this threat in its tracks and protect Montana jobs and livelihoods.”

While the environmental impact is obviously disastrous, the destruction of the fisheries and waterways could also have a severe economic impact. Outdoor activities, including boating and fishing, are thought to generate close to $6 billion annually in Montana and support over 64,000 jobs in the state. The parks authority so far report over 2,000 dead mountain whitefish, but they estimate that the actual figure is far higher, sitting somewhere in the tens of thousands.

There is now concern that the parasite will rapidly spread to the rainbow trout living in the same rivers, and hence the decision to try and limit the spread by stopping all activities on the water. Even though many of the smaller tributaries that flow into the Yellowstone River originate in the world famous National Park that shares its name, it appears that the parasite has not established itself within the park just yet, as fish populations remain healthy within its boundaries.


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