The zebra mussel is a small freshwater mussel, this species was originally native to the lakes of southern Russia. Since their first appearance in American waters in 1988, zebra mussels have spread to a large number of waterways, including Lake Simcoe in the Great Lakes region and the Mississippi, Cumberland, Ohio, Tennessee, Michigan, Colorado and Arkansas. Unfortunately, the zebra mussel invasion continues. For example, in 2009 the Massachusetts Department of Conservation and Recreation confirmed that zebra mussels had been found in Laurel Lake in the Berkshires. That same year the Minnesota Department of Natural Resources announced that live zebra mussels had been found in Pelican Lake, Minnesota. This was the first confirmed sighting in the Red River basin, which extends across the international border into the province of Manitoba. In July 2010, the North Dakota Game and Fish Department confirmed the presence of zebra mussels in the Red River. Recently, in 2010, California also reported similar invasions. In 2011, a mussel invasion caused a reduction in water supplies during a year-long drought, worsening water restrictions throughout the Dallas area. However, it has been accidentally introduced into many other areas and has become an invasive species in many different countries around the world. Zebra mussels get their name from a striped pattern that is commonly seen on their shells, although it is not universally present. They are usually the size of a fingernail, but can reach a maximum length of nearly two inches. Zebra mussel shells are D-shaped. Zebra mussels are organisms that filter and remove particles from sediment on lake beds. Zebra mussels process up to a liter of water... half a paper... d when transoceanic ships drop anchor in freshwater ports. They have become an invasive species in North America and as such are the target of federal policy to control them, for example in the National Invasive Species Act (1996). A common hypothesis made by scientists predicts that the zebra mussel will continue to spread passively, via ships and recreational boats, to more rivers in North America. Towed boat traffic is the most likely cause of the invasion of North America. This spread can be prevented if boaters thoroughly clean and dry their boats and related equipment before transporting them to new bodies of water. Since no North American predator or combination of predators has been shown to significantly reduce zebra mussel numbers, such spread would most likely result in the permanent establishment of zebra mussels in many North American waterways..