Hundreds of dead fish have washed up in the Yellowstone River. Reports of the dead mountain whitefish began in late August, and an investigation into their deaths has been launched. While the reason for the deaths has not been confirmed, many think a parasite that affects salmonoids is the killer.
Similar mass mortality occurred in 2016. Bozeman Fish Health Center identified Proliferative Kidney Disease as the cause, says the National Park Service. Before the 2016 incident, the parasite was not known to be found in the Yellowstone River.
In 2016, nearly 4,000 whitefish were found dead in the river, due to the parasite. The river closed as a result. Montana Fish, Wildlife, and Parks report that within three days they found almost 200 dead mountain whitefish along the river. Right now, there has been no forced closure of the park, due to this year’s fish-kill. The website also states that there has been no trout mortality in this year’s fishkill.
Montana FWP says they are working to confirm the cause of death. In their September 1 news release, they say, “FWP has worked with other agencies to submit samples for testing to determine whether PKD is a factor in this most recent whitefish mortality.”