Zebra Mussels

Zebra mussels, Dreissena polymorpha, are small, fingernail-sized, freshwater mollusks accidentally introduced to North America via ballast water from a transoceanic vessel. Since their introduction in the mid 1980s, they have spread rapidly to all of the Great Lakes and an increasing number of inland waterways in the United States and Canada. Zebra mussels colonize on surfaces, such as docks, boat hulls, commercial fishing nets, water intake pipes and valves, native mollusks and other zebra mussels. Their known predators, some diving ducks, freshwater drum, carp, and sturgeon, are not numerous enough to have a significant effect on population levels. Zebra mussels have impacted the Great Lakes ecosystem and economy greatly. (Source: National Sea Grant)

Impact on Waterbodies

Zebra mussels are filter feeders. As water passes through their body, all of the particles are filtered out and then either digested or wrapped in mucus and spit out. Because a single mussel is capable of processing up to a gallon of water per day, high density populations of zebra mussels eventually clear the water of even the largest lakes.

Unfortunately, zebra mussels filter algae and microscopic animals from the water that serve as a food supply to young fish and invertebrates. This change in food availability at the bottom of the food chain, causes a domino-effect that has lead to declines in some fish and animal populations.

Clearer waters also allow sunlight to penetrate to greater depths, resulting in an increase in aquatic plant growth. While more plants can benefit many types of fish, they can also cause problems for boaters and swimmers, clog water intake pipes, and increase taste and odor problems in drinking water.

Impact on Swimmers

Zebra mussel shells are razor sharp and can cause painful cuts to swimmers with unprotected feet. Swimmers should wear protective footwear, such as aqua-shoes, when walking or wading in waters infested with zebra mussels.

Although removing zebra mussels from a lake or river is almost impossible, preventing their spread into new areas is not. Human activities have spread zebra mussels into many inland lakes and streams, usually through recreational boating, fishing, and diving practices. Simple steps such as draining live wells, cleaning vegetation off boat trailers, removing attached zebra mussels from boat hulls, and not dumping bait into lakes or rivers can prevent the spread of zebra mussels and other exotics into non-infested waters.

Impact on Water Intake Pipes


Zebra mussels can attach themselves to hard surfaces including docks, rocks, boats, water lines, retaining walls and buoys. They are capable of clogging intake pipes as well as household pipes. However, whether or not the mussels will infest a particular home is unpredictable.

Zebra mussels can enter water intakes at different life stages via different mechanisms. In the larval stage, the tiny larvae (called veligers) are carried by the water flow. As juveniles, they can crawl using their clam-like foot and as adults they can break loose from colonies and travel to the mouths of intakes by lake currents.

The first indication that zebra mussels are in a water intake is usually the discharge of shells or shell parts at the shore end of the pipe, a noticeable decrease in water pressure or foul tastes and odors in the water.

Lakeshore residents that get their water from either Otisco or Skaneateles Lake should take early action to keep the mussels out of household pipes in order to avoid costly repairs. The two methods used to protect household pipes are in-line filtration (filter size 40 microns absolute or smaller) and in-line chlorination. Both of these methods have the added benefit of providing cleaner, safer water for your home.