What is the quagga mussels current distribution in the United States?
The quagga mussel is currently distributed in all five Great Lakes, throughout the St. Lawrence River north to Quebec City, and in a number of inland water occurrences in New York, Ohio, Michigan, Pennsylvania, and southwestern United States. The first sighting of the quaggas outside the Great Lakes basin was made in the Mississippi River between St. Louis, Missouri and Alton, Illinois in 1995 (S. J. Nichols, pers. comm.). No others have been found in the river since then. The absence of quagga mussels from areas where zebra mussels are present may be related to the timing and location of introduction rather than physiological tolerances (MacIsaac, 1994). The quagga must have arrived more recently than the zebra based on differences in size classes, and therefore it seems plausible that the quagga is still in the process of expanding its nonindigenous range (May and Marsden, 1992; MacIsaac, 1994). In fact in 2005, the first quagga mussel was confirmed from Lake Superior in Duluth Super
