|Dead mussels along the Clinch River|
(Photo by Meagan Racey, U.S. Fish and Wildlife Service)
"Biologists at a regional branch of the United States Fish and Wildlife Service in southwestern Virginia first learned about losses in fall of 2016 when locals in reported that large numbers of pheasantshell mussels (Actinonaias pectorosa) were dying in the Clinch River along the Virginia and Tennessee border," Jason Daley reports for Smithsonian Magazine. "The Clinch River isn’t alone. Biologists have also recorded recent mass freshwater mussel die-offs in the Pacific Northwest, Oklahoma, Wisconsin, Michigan and even one in Spain. What exactly is killing off the mollusks is not clear, and testing has not identified a single culprit. At first, researchers suspected chemical spill or some pollutant was responsible. But the fact that only one species—the pheasantshell—was affected at first suggests a disease is responsible."