Zebra Mussel

Dreissena polymorpha

Do you think you have discovered an aquatic invasive species?

  1. Do not return the species to the water.
  2. Note the exact location (GPS coordinates) and the observation date.
  3. Take photos.
  4. Take note of identifying features.
  5. Report an Aquatic Invasive Species, depending on where you are.
  6. What you can do to reduce the risk.
Zebra Mussel

Zebra Mussel

Zebra Mussel is capable of heavily colonizing hard and soft surfaces, including, docks, boats, break walls and beaches. This colonization’s is also responsible for clogging intake structures in power stations and water treatment plants.

Identifying features

  • Average 2-2.5 cm, reaching up to 4 cm long
  • Sits flat on its underside
  • Triangular in shape
  • Black or brown with white to yellow zigzagged patterns
  • Colour patterns can vary.

Similar species (native)

Quagga Mussel (Dreissena polymorpha)

The Zebra Mussel differs from the Quagga Mussel in being smaller, squarer and narrower. The Quagga Mussel has a convex ventral surface.

Where it has been found

Zebra Mussels are found throughout all the Great Lakes, Lake St. Clair and the Mississippi river watershed.

Ecological and economic impacts

  • Zebra Mussel filters water to the point where food sources such as plankton are removed, altering food webs. This also causes clearer water, allowing sunlight to penetrate deeper, increasing growth of aquatic vegetation.
  • Impact fish and wildlife by increasing toxic algal blooms.
  • Females can release up to a million eggs each season which enhances the natural dispersal of this species from locations where it is introduced.
  • Large colonies affect spawning areas, potentially impacting the survival of fish eggs.
  • These mussel species can cause millions of dollars in damage to boat engines, power plant and public water intakes by fouling infrastructure, blocking water flow and costing time and money removing them from affected structures.

Origins and mode of arrival

Native of the Black and Caspian seas region in Southeastern Europe.

The Zebra Mussel, as the Quagga Mussel, was introduced to the Laurentian Great Lakes of North America via ballast water.

Mode of dissemination

The Zebra Mussel have rapidly dispersed throughout the Great Lakes region into river systems and smaller lakes due to passive drifting at the larval stage and their ability to attach to the hulls of boats. In addition, these mussels are very prolific and can have profound effects on ecosystems by depleting the biomass of phytoplankton communities, which in turn affect the composition of other communities within the ecosystem.

Zebra Mussel

Zebra Mussel

Government action

Scientific research

Fisheries and Oceans Canada is studying the Zebra Mussel population to improve its understanding of how it reacts and adapts to Canadian conditions.

For further information


  • DFO. 2014. Lake Winnipeg Zebra Mussel treatment. DFO Can. Sci. Advis. Sec. Sci. Resp. 2014/031.
  • Therriault, T.W., Weise, A.M., Higgins S.N., Guo, S. and Duhaime, J. 2013. Risk Assessment for Three Dreissenid Mussels (Dreissena polymorpha, Dreissena rostriformis bugensis, and Mytilopsis leucophaeata) in Canadian Freshwater Ecosystems. DFO Can. Sci. Advis. Sec. Res. Doc. 2012/174 v + 88 p.
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