Invasive Species Zebra Mussel - NVCA

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​​​​Zebra and Quagga Mussels

Zebra mussels.jpg
In this photo: ​Zebra Mussels

Zebra and Quagga Mussels (Dreissena polymorpha & begensis) are two of Ontario's most unwanted invasive species. 

Both Zebra and quagga mussels are native to the Black Sea in Eurasia and were introduced to Ontario in the late 1980s via ship ballast. They both have the capability to densely colonize hard and soft surfaces of lake bottoms. Quagga mussels tends to inhabit deeper waters than zebra mussels. Both mussels can have significant impacts on lake ecosystems!


  • Zebra Mussels
    • Usually 2 cm long but can grow up to 4 cm
    • Sits on a flat surface
    • Triangular shape
    • Brown and yellow colouring, with zigzagging patterns
  • Quagga Mussels
    • Usually 2 cm long but can grow up to 3 cm
    • Cannot sit on a flat surface
    • Round in shape
    • Light colouring with dark concentric rings​​

Where are they found in our watershed?

Zebra and quagga mussels are abundant throughout Georgian Bay including Nottawasaga Bay and have impacted the entire lake ecosystem. They are present in the Collingwood Harbour and at the mouth of the Nottawasaga River. They also been observed in Bass Lake.

Why are they of concern?

Zebra and quagga mussels filter lake water to the point where there is limited food for native filter feeders including invertebrates that support entire lake food webs. 

Intense filtering increases water clarity, allowing sunlight to reach lower depths increasing the growth of filamentous green algae which can wash up to rot on local shorelines. 

Mussel waste can host botulism bacteria which can accumulate in the food chain resulting in mass die-offs of fish eating birds and Lake Sturgeon (a threatened species). 

Colonization of water-intake piping structures at power stations and water treatment plants results in clogging and expensive remedial measures.

How to Control the Spread

  • Remember to drain water from your motor, live well, and bilge whenever leaving a water body.
  • Clean all aquatic equipment by either warm water, water pressure washer, or leave in the sun for 5 days even if you do not see mussels on it, because larvae can still be transported!

Early Detection is Key

Early detection and rapid response is essential for the control and/or eradication of invasive species in an area. If you spot these mussels, please report the sighting to EDDmapS

More Information

Ontario’s Invading Speci​​es Awareness Program - Zebra & Quagga Mussels​