Zebra and quagga mussels originated in southern Russia and Ukraine, but have spread across Europe, Great Britain, and parts of North America. They are two of the most significant aquatic invasive species in the United States. Since 1998 when they were first detected in the Great Lakes, infestations have fundamentally changed the food web of the Great Lakes and cost utilities in that region hundreds of millions of dollars in damage and repairs.

Although zebra or quagga mussels had been found in the middle and lower Missouri drainage prior to this fall, there was no evidence these species occurred upstream in eastern or central Montana. The Columbia River basin, which includes portions of northwest Montana, is the only major watershed in the west still believed to be free of these invasive species. Finding zebra or quagga mussels in Tiber Reservoir puts them within a few-hours? drive of Flathead Lake, the largest natural freshwater lake in the conterminous states west of the Mississippi.

Dr. Tom Bansak, assistant director of the University of Montana?s Flathead Lake Biological Station said, ?This is a huge deal. We have been bracing ourselves for this for a long time and hoped it would never happen. Well, it?s here, it?s now, it?s real, and the only possible chance of getting rid of them is finding them early and in a localized area.?