Transportation of zebra mussels from infested waters to noninfested waters can occur by boats, trailers, and anglers. Juvenile and adult mussels can attach themselves to ship and recreational boat hulls and trailers. However, the microscopic mussel larvae can easily be transported in ballast water, boat bilge, engine cooling systems, bait buckets, and live wells. This inadvertent transportation of larval mussels has likely enhanced the bivalve's dispersion and rapid expansion into noninfested inland waters of the United States. They are usually marked with alternating light and dark herringbone bands, but the number and pattern of the bands or stripes is highly variable.
Most zebra mussels are thumbnail size, but some grow up to two inches long.
Zebra mussels grow in dense clusters that contain numerous individuals attached firmly to surfaces by strong adhesive threads called byssal fibers. This often results in drastically reducing the water flow into the plants. Colonies of zebra mussels can also be found along lakeshores, riverbanks, and piers. And mussels will attach to aquatic plants, rocks, floating debris, other bivalves, and crustaceans. Reports of zebra mussel densities along many shallow areas of Lake Erie exceed 30,000 per square meter.