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Dreissena Polymorpha, commonly known as Zebra Mussels, are indigenous to Europe and,
prior to 1988, were unknown in the waters of the United States and Canada. It is theorized a
foreign ship emptying its ballast introduced the Zebra Mussels to the waters of Lake St. Clair from
which they spread into the Great Lakes and have gone as far as the Ohio and Tennessee River
systems.
Biologists believe the Zebra Mussel ultimately will infect most areas South of Central
Canada and North of the Florida Panhandle, from the Atlantic to the Pacific coasts. Prolific
breeders, a single female Zebra Mussel may lay some ten thousand to two million eggs per year.
Zebra Mussels are extremely hardy, have few natural predators and can survive out of water for
substantial periods of time (up to 14 days), merely requiring moist or humid areas in which to
exist.
They have a four to eight-year life cycle comprising four stages. The Fertilized Egg, lasting two to
three days; the Veliger or larvae stage, lasting two to three weeks; the Settling Stage; and the
Adult Stage; which begins at about 12 months.
The Veliger Stage presents the greatest problem. Zebra Mussel Veliger’s hatch from eggs
at a size of approximately 70 microns (>.00275 inch). In this stage, they are a free
swimming plankton larval which may disperse for miles and are small enough to enter
residential water systems which draw their water supply from the Zebra Mussel
contaminated river, streams ponds and lakes.
Both shallow and deep intakes are affected since Zebra Mussels generally colonize from two feet
of the water surface to depths of 200 feet or more. In the settling stage they are visible to the eye
and possess visceral threads, known as busses, which cling to or attach to almost any solid
stationary surface in areas having low velocity currents, e.g. Iess than approximately seven feet
per second. They can attach to a variety of surfaces including Metal, Concrete, Plastic and
Teflon. They attempt to attach or connect to such surfaces and can colonize residential pipes and
other intake systems, blocking the free flow of water. They have been known to form into mats or
clumps up to five inches thick.
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