Zebra mussels (Dreissena polymorpha) are a small invasive freshwater mussel from southwestern Europe (specifically the Black and Caspian Seas) that first arrived in the Great Lakes in the1980s through infested ballast water that was discharged from ships. Since then, they have been spreading through eastern Canada and the United States impacting ecosystems, recreational activities, and infrastructure.
Zebra mussels are filter feeders that will attach themselves to any solid surfaces touching infested waterways, such as boats, docks, rocks, plants, and native mussels. The females can produce up to 1 million eggs per breeding season, and the free-swimming veligers (larvae) can float in the water column for up to a month before attaching to available surfaces, colonizing in densities of up to 700,00 individual mussels per m2.
The presence of zebra mussels can negatively impact freshwater ecosystems by:
- Filtering water to the point where important food sources like plankton are depleted, which alters food webs. The over-filtering also creates clear water allowing sunlight to penetrate deeper which can increase growth of invasive aquatic plants like Eurasian Watermilfoil.
- Increasing toxic algae blooms, pathogenic bacteria, avian botulism, which impacts fish and wildlife.
- Altering spawning areas by changing the materials on the bottom on the waterways, which impacts fish egg survival.
Since they are capable of heavily colonizing on various surfaces, they can also negatively impact recreational activities and vital infrastructure. Due to their razor-sharp shell, recreational users are at a risk of cutting their feet while walking on beaches or swimming in water infested by zebra mussels. These invasive mussels are also responsible for clogging intake structures used by water treatments facilities and power plants. The management of zebra mussels can also be costly for local government agencies. Between 2017 and 2019, municipalities in Ontario reported spending $4.5 million annually on the control, prevention, and detection of these mussels.
Larval zebra mussels, called veligers, are difficult to identify as they are microscopic and therefore too small to see with the naked eye. They are unable to swim on their own and so are free-floating, moving with the water currents.
Adult zebra mussels can be identified by their:
- triangular shape, often with dark and/ or light bands on their shells,
- small size; ranging from 2 cm to 4 cm (~1 inch) long,
- tuft of fine threads, called byssal threads, near the opening of the bottom of the shell which they use to firmly attach to under-water surfaces.
What Can I Do?
- Clean, Drain and Dry any recreational equipment (boats, canoes, kayaks, fishing gear, etc.) before entering a new body of water. Learn more on the Canadian Council on Invasive Species' website and/ or the New Brunswick Invasive Species Council (NBISC) website.
- Learn how to identify zebra mussels using the Identification above and/or by visiting NBISC’s website.
- Report any sightings immediately to:
New Brunswick Invasive Species Council
Phone: (506) 262-6247
Department of Fisheries and Oceans
Department of Natural Resources and Energy Development
Phone: (506) 453-3826
Include the following information:
– The exact location of the sighting (GPS coordinates) and date;
– Identifying features and photos of the mussel(s).