These species made the trip to America by stowing away in the ballast water of ocean-going vessels. When the vessels dumped their ballast into the Great Lakes, the travelers had a new home. Evidence indicates that the Great Lakes' most famous recent invader, the zebra mussel, got its start that way. Zebra mussels look like small clams and are about the size of a thumbnail. These fibers allow the mussels to attach to any hard surface-including other mussels.
Female mussels can reach maturity in less than a year.
Once mature, they can produce more than one million eggs per year. Veligers can remain in the water column for more than a month before settling and attaching. During this time, they can be transported great distances by currents. History tells us that zebra mussels have always been on the move. They're native to the Ponto-Caspian region of western Russia.