<P> The first appearance of the organism in northern Italy was in Lake Garda in 1973; in central Italy, they appeared in Tuscany in 2003 . </P> <P> Zebra mussels are also present in British waterways . Many water companies are reporting having problems with their water treatment plants with the mussels attaching themselves to pipeworks . Anglian Water has estimated that it costs £ 500,000 per year to remove the mussels from their treatment plants . It has been argued that zebra mussels have also had an effect on fish populations, with dwindling fish populations in areas such as Salford Quays . </P> <P> They were first detected in Canada in the Great Lakes in 1988, in Lake St. Clair, located east / northeast of Detroit and Windsor . It is believed they were inadvertently introduced into the lakes in the ballast water of ocean - going ships traversing the St. Lawrence Seaway . Another possible, often neglected, mode of introduction is on anchors and chains, although this has not been proven . Since adult zebra mussels can survive out of water for several days or weeks if the temperature is low and humidity is high, chain lockers provide temporary refuge for clusters of adult mussels that could easily be released when transoceanic ships drop anchor in freshwater ports . They have become an invasive species in North America, and as such they are the target of federal policy to control them, for instance in the National Invasive Species Act (1996). </P> <P> Using models based on the genetic algorithm for rule - set production (GARP), a group of researchers predicted that the southeastern United States is moderately to highly likely to be inhabited by zebra mussels and the Midwest unlikely to experience a zebra mussel invasion of water bodies . However, this model has since been proven incorrect . In 2006 a researcher (also using GARP) predicted invasion as far west as the North Platte River, Nebraska, by 2015 . As of March 2016, zebra mussels have affected hundreds of lakes in the Midwest including the Great Lake Michigan, and the largest freshwater lake in Wisconsin, Lake Winnebago . See the March 2016 USGS Zebra mussel distribution map for full scope of invasion . </P>

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