The Canals made shipping more efficient, but as an unintended consequence also allowed rapid expansion of the zebra mussel's range. By the 1830s, these mussels covered much of Europe and Britain.
Successful introduction of zebra mussels into the Great Lakes probably occurred in 1985 or 1986, after transoceanic ships discharged contaminated ballast water from foreign ports into lakes St. Clair and Erie.
