Are Zebra Mussels Still Spreading?
In the mid-1980s a new species found its way to North America. The zebra mussel (Dreissena polymorpha), a small, clamlike mollusk that grows to about 25 centimeters as an adult, was introduced into the waters of the Great Lakes, probably carried in the bilge of a Russian freighter. The zebra mussel can reproduce in less than a year, and a single female can release 1 million eggs each year. In the absence of their natural pathogens, parasites, and predators, the zebra mussel populations in the Great Lakes has grown enormously and are now invading eight major river systems, including the St. Lawrence, Hudson, Mississippi, Ohio, Illinois, Tennessee, Susquehanna, and Arkansas rivers. The mussels are spread from one body of water to another by natural flow, carried on the feathers or feet of migrating waterfowl, or by human transport in bait buckets or on trailered boats. Most of the freshwater systems in North America are now threatened by invasion of the zebra mussel. The zebra mussels gr
