Zebra and Quagga Mussels

  • Zebra and Quagga Mussels

    (Dreissena polymorpha and D. bugensis)

    Native to the Black Sea region in Eurasia, Zebra Mussels and the smaller Quagga Mussel were likely introduced as larvae to North America in the late 1980s through ballast water from ocean-going ships. The two species live for 3 to 5 years and are capable of producing large colonies on hard and soft surfaces. They can release 30,000 to 50,000 fertilized eggs in a breeding cycle and about one million in a year. In addition to docks, boats, breakaways and beaches, they have colonized intake structures in power stations and water treatment plants, leading to clogging of water intakes. They looking like small clams.

    The Round Goby, which is an invasive fish species originally from the same environment as the Zebra Mussel in Eurasia, is a natural predator, eating up to 78 Zebra Mussels per day. Diving ducks and Freshwater Drum (Aplodinotus grunniens) also eat Zebra Mussels.


    Zebra Mussels have spread throughout the Great Lakes, Lake St. Clair and the Mississippi River watershed while Quagga Mussels have until recently been limited to Lake Erie, Lake Ontario, Lake Huron and Lake Michigan as well as the St. Lawrence River north to Quebec City. Quagga Mussels were found in Lake Mead in 2007, where they are believed to have been introduced on recreational watercraft. They have since been introduced into California watersheds which draw raw water from Lake Mead.

  • Identification

    • Zebra Mussels are the larger of the two species of mussels, averaging about 2 to 2.5 cm but also reaching up to 4 cm in length. Quagga Mussels average about 2 cm but also reach up to 3 cm in length.
    • Zebra Mussels sit flat on its underside while Quagga Mussels do not sit flat.
    • Zebra Mussels are triangular in shape while Quagga Mussels are round in shape.
    • Zebra Mussels are black or brown in colour with white to yellow zigzag patterns while Quagga Mussels have dark concentric rings.
    • Quagga Mussels are paler in colour near the hinge while Zebra Mussel colour patterns can vary.


    Zebra and Quagga mussels alter food webs by filtering water and reducing food sources such as plankton. This causes clearer water, which allows sunlight to penetrate and may promote the growth of aquatic plants.
    The mussels impact fish and wildlife by increasing algal blooms.
    Large colonies of the mussels affect spawning areas, which may impact the survival of native fish eggs.
    The spread of invasive mussels has been associated with significant reductions in the range and abundance of some native invertebrate species.
    Sharp mussel shells can cut the feet of swimmers, affecting recreational activities.

    How can you help?

    Learn to identify the Zebra and Quagga mussels and how to prevent their spread to other water bodies.
    Inspect your boat and equipment and remove any plants, animals or mud before relocating.
    Completely drain water from your boat motor, bilge and live well and transom wells while high and dry.
    Rinse all recreational equipment with high pressure and hot water or dry in sunlight for 5 days or more.
    If you observe Zebra and Quagga mussels or other invasive species, please contact the Turtle Island Invaders hotline at 1-844-872-2348 (1-844-TRACE-IT) toll-free or report the sighting to your local Lands or Natural Resources officer.

    Chiefs of Ontario Zebra Mussels PDF
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