Quagga and Zebra Mussels

Quagga (Dreissena bugensis) and Zebra Mussels (Dreissena polymorpha) are aquatic invasive mollusks that impact native species, the ecosystem, recreation and industry. Economic and social impacts of mussel attachment to objects range from inconvenience to expensive repairs. Most of the lakes in the Great Lakes region are at risk for being invaded.

Understanding the Impact of Quagga and Zebra Mussels

Quagga and zebra mussels are filter-feeders, and feed by drawing water into their bodies and straining out microscopic plants, animals, and debris for food. This process can lead to increased water clarity and a depleted food supply for other aquatic organisms. Increased water clarity, and thus increased light penetration, can lead to an increase in rooted plants. A reduced food supply may affect the food web, including game fish.

The mussels’ filtering process can also lead to algal blooms. When filtering, quagga and zebra mussels tend to reject blue-green algae, and spit them back into the water. These algae are then able to thrive because other types of algae are reduced.

Quagga and zebra mussels attach to submerged surfaces. Boats, boat motors, water intake pipes, submersible pumps, docks, floats, rocks, native mussels, and aquatic plants are all susceptible to being colonized by mussels. Large colonies can take over fish spawning areas and beaches, cutting the feet of potential swimmers. Their dense colonies also clog water intake lines.

Download the factsheet Zebra Mussels: Questions and Answers for Inland Lake Managers

Lake Michigan Quagga Mussel Density

Invasive quagga mussels are so entwined and influential in Lake Michigan’s food web that they are an essential first line of study. Scientists on the R/V Lake Guardian in 2015 measured the density and biomass of quaggas all across the lake using traditional sampling methods like PONAR grab...

Environmental impacts of Zebra and Quagga Mussels

Zebra and quagga primarily consume phytoplankton, which reduces the plankton availability for other organisms, and effects can be seen throughout the food web. This filtering also increases the amount of sunlight in the water, promoting algal blooms and leading to decreased water quality. Invasive mussels also attach to the shells of native species, suffocating populations of already threatened populations of freshwater mussels. Invasive mussels also retain toxins as they filter the water, which can lead to botulism in mussel-eating fish and waterfowl.

Recent research suggests invasive mussels have a role in the phosphorus cycle in large lakes, which could impact everything from phytoplankton communities to large predatory fish.

Economic Impacts

The ability of quagga and zebra mussels to rapidly colonize surfaces can cause serious economic harm. Invasive mussels can clog water intake structures, such as pipes and screens, therefore reducing pumping capabilities for power and water treatment plants and other industrial facilities and posing costs to industries, companies, and communities. Recreation-based industries and activities have also been impacted; docks, breakwalls, buoys, boats, and beaches have all been heavily colonized by these mussels.

Navigational and recreational boating can be affected by increased drag due to attached mussels. Small mussels can get into engine cooling systems causing overheating and damage. Navigational buoys have sunk under the weight of attached mussels. Fishing gear can be fouled if left in the water for long periods.

History of Quagga and Zebra Mussels

Quagga and zebra mussels are native to eastern Europe. The quagga mussel originated from Dnieper River drainage of Ukraine. The zebra mussel was first described from the lakes of southeast Russia and its natural distribution also includes the Black and Caspian Sea

Quagga and zebra mussels were most likely brought to the Great Lakes in the 1980s as larvae in ballast water of ships that traveled from freshwater Eurasian ports inhabited by the mussels and into the Great Lakes, where the ballast water with mussel larvae were released. From the Great Lakes, these mussels have spread across the continental U.S. In 1991, zebra mussels escaped the Great Lakes basin and found their way into the Illinois and Hudson rivers. The first sighting of quagga mussels outside the Great Lakes basin was made in the Mississippi River between St. Louis, Missouri and Alton, Ill., in 1995. The Illinois River was the key to their introduction into the Mississippi River drainage.

Quagga and zebra mussel larvae and adults can be spread by many mechanisms including ballast water, water currents, anglers’ bait buckets, and boaters’ bilge and livewells. Adults can also be spread when they attach to boats and aquatic plants, which are then transported to other lakes. Short distance spread between fresh waterways within countries most likely occurs through recreational boats. These mussels can survive for three to five days out of water.

Because their physical and chemical characteristics fall within the ranges required by quagga and zebra mussels, most of the lakes in the Great Lakes region are at risk for being invaded.

Regulation of Quagga and Zebra Mussels

Both quagga and zebra mussels are listed as "injurious" under the federal Lacey Act, 18 USC 42, a criminal statute that prohibits the importation and interstate transport of species listed under the statutory provisions as "injurious wildlife." Illinois lists both quagga and zebra mussels as injurious species (ILL. ADM. CODE CH. 1, § 805).

A group of muscles
Identification of Quagga and Zebra Mussels

Quagga and zebra mussels are closely related to each other and look very similar. Both species are small bivalve mollusks and typically grow to the size of a fingernail. They have a two-halved shell and are related to clams. Their shells characteristically have alternating light and dark bands, such as like a zebra, but may be entirely light or dark. The quagga mussel was discovered after the zebra mussel, and therefore gets its name from an extinct relative of the zebra.

Although the quagga mussel looks like the zebra mussel, the two species can be distinguished by their shell morphology. When placed on a surface, zebra mussels are stable on their flattened underside while quagga mussels, lacking a flat underside, will fall over. Quagga mussels are rounder and have more concentric rings as opposed to the striped pattern of a zebra mussel.

While zebra mussels are limited to colonizing hard surfaces, quagga mussels can also colonize on soft substrates. They are also able to survive in low-food environments, so when both species co-exist, quagga mussels are the dominant species and can out-compete zebra mussels.

Management of Quagga and Zebra Mussels

Quagga and zebra mussels will accumulate on docks and floats, but will die if the docks and floats are pulled up on land during the winter. Boat motors should be flushed and thoroughly drained after boating to prevent quagga and zebra mussels from surviving and settling within the cooling system.

Swimmers and beachgoers can protect their feet from cuts by mussel shells by wearing sandals or swimsocks.

Water intakes can be protected by converting them to sand-filter intakes. Some property owners allow inexpensive intakes (e.g., PVC pipe) to become clogged, and replace them when necessary. Water pumps and a home’s internal piping can be protected by installing a filter between the lake and the pump.

Never release captive animals or plants into the wild, and take proper precautions when moving boats and other equipment from one water body to another.

Before you leave a body of water after boating or fishing, always remove, drain, and dry:

  • REMOVE plants, animals, and mud from all equipment. Mud and plant fragments can also hide aquatic invasive species that are too small to be seen with the naked eye.
  • DRAIN all water from your boat and gear. Boaters should ensure plugs are pulled from bilge and live wells before leaving a waterway. Bait bucket water should be drained on land.
  • DRY everything thoroughly with a towel. All equipment that comes into contact with water should be wiped off and dried with quick-dry towel. If possible, dry everything for five days before entering new waters.

Clean other equipment as necessary. Waders and boots should be scrubbed and rinsed with tap or well water. If possible, use hot or high-pressure water to clean your equipment. Using a car wash for your boat and trailer is a great alternative. Full-strength white vinegar or a solution of ¼ cup bleach per gallon of water can be used to disinfect equipment and confined spaces like live wells.