Quagga mussels (Dreissena bugensis) are closely related to another invader, the zebra mussel (Dresssena polymorpha). Quagga mussels are native to Caspian Sea drainage in Eurasia. They most likely arrived as stowaways in the ballast water of ocean going ships. Quaggas like silty or sandy lake bottoms. They can live in waters ranging from warm and shallow to deep and cold. They are also able to tolerate brackish water. Since zebra mussels cannot survive this range of conditions, they can thrive in areas that zebra mussels cannot.
Unlike the zebra mussel, the quagga mussel shell has a rounded angle or carina. The quagga is light tan to almost white, with narrow stripes or mottled lines. It is fan-shaped, with pointed edges at either side. The ventral (bottom-side where the 2 shells attach) side of the quagga mussel is convex which makes the quagga mussel topple over when placed ventral side down on a flat surface. The zebra mussel will remain upright when placed in this position.
A quagga mussels feed all year, even in winter when its cousin the zebra mussel lies dormant. Some researchers believe that Lake Erie's dead zone is likely the partial work of the tiny quagga mussel’s non-stop feeding, its ability to live in deep water (it has been found at depths up to 130m in the Great Lakes) and the excretion of phosphorous with its waste.
So far, the quagga has been found only in Lake Michigan waters that border Wisconsin – not in any inland lakes. But because they prefer silt- and sand-bottomed lakes, quagga mussels may be able to successfully invade inland lakes with those characteristics if introduced, including some lakes not suitable for zebra mussel establishment.