Invasive zebra mussel (top) and quagga mussels collected from Lake Michigan in 2006. USFWS photo by Gary Wege

Quagga mussels (Dreissena bugensis) have been found in the Upper Mississippi River based on 2004 – 2006 surveys conducted for the U.S. Environmental Protection Agency.  Quagga mussels resemble zebra mussels, another invasive species which has infested the Upper Mississippi River and other waterways.  Both species entered the Great Lakes from the ballast water of large ocean-going vessels.  Once Lake Michigan became infested, the mussels traveled downstream via the Illinois River to the Mississippi River, where they were transported upstream by towboats and other large craft using the federal navigation system.  Although their densities were very low compared to zebra mussels, quagga mussels were collected from Pools 4, 5, 7 and 10.  This river reach includes a variety of state and federally listed native mussels including Higgins eye (Lampsilis higginsii).  Both quagga and zebra mussels attach to hard surfaces, clogging marine equipment and water intake facilities. They can adversely affect native mussels by interefering with their shell opening/closing and ability to bury into sediments, competing for food, lowering dissolved oxygen levels, and interfering with reproduction. At high densities, they can form a thick carpet (up to several feet thick) on the river bottom completely burying mussels and other bottom-dwelling organisms.