Zebra and quagga mussel facts

Invasive mussels in B.C.

Quagga mussels (Dreissena rostriformis bugensis) and zebra mussels (Dreissena polymorpha) are not native to North America. They were introduced by trans-continental shipping from the Baltic Sea to Canada (the Great Lakes region) and the United States in the 1980s. Since their introduction, these mussels have spread in Ontario and Quebec and they are now found in over 24 American states as far west as California. In October 2013, zebra mussels were discovered in Lake Winnipeg, Manitoba and in 2016 invasive mussels were confirmed Tiber Reservoir in Montana. While not yet present in B.C., ZQM could survive in B.C. freshwater systems if introduced.


Unlike B.C.’s native mussels, Zebra and Quagga mussels attach to hard surfaces, allowing them to be moved between water bodies by boats and equipment. These small, freshwater mussels can easily attach themselves to boat hulls, trailers, motors, equipment, vegetation and other organisms. Newly settled mussels are particularly difficult to detect as they are only a few mm's in size. They multiply rapidly and are extremely difficult to eradicate once they become established in an area. In larger water bodies and complex ecosystems they may be impossible to eradicate unless detected and contained before they become established.

Zebra and quagga mussels can survive for several weeks without being immersed in water if they are left in a cool and moist environment, so mussels attached to boats or equipment can be transferred from one body of water to another. Their microscopic free-swimming larvae can also survive for several weeks in standing water in boats or other equipment. Freshwater invasive mussels spread by fouled recreational boats on trailers and boats destined for B.C. are intercepted by US jurisdictions every year.

Threat to B.C.

Zebra and quagga mussels pose a serious threat to B.C.’s aquatic ecosystems, salmon populations, hydro power stations and other infrastructure facilities.

Zebra and quagga mussels can substantially alter aquatic food webs which could result in the collapse of valuable native fish populations in B.C. such as sockeye salmon. Zebra and quagga mussel infestations can displace native aquatic plants and wildlife, degrade the environment and affect drinking water quality. These mussels have been identified as a threat to B.C.’s endangered Rocky Mountain Ridged Mussel (Gonidea angulata).

They can clog pipes, water intake systems (hydropower facilities, agriculture irrigation systems), and municipal water supply. This can increase maintenance costs for operating hydroelectric, industrial and agricultural facilities. These mussels can decrease the quality of the recreational experience and impact tourism as mussel shells can injure swimmers along shorelines and next to docks, foul boat propellers and potentially harm drinking water. The economic impact of these invasive mussels to hydropower, agricultural irrigation, municipal water supplies and recreational boating has been estimated to be $43 million per year. This estimate does not include additional impacts on commercial and recreational fisheries.

To date, there has been no reported introduction of live quagga or zebra mussels into B.C. lakes or waterways. Zebra and quagga mussels are not established in British Columbia, Alberta, Saskatchewan, Oregon, Idaho, or Washington.

invasive mussels

How to Identify Zebra & Quagga Mussels

Distinguishing features of Zebra & Quagga Mussels:

  • Range in size from 1 mm to 3 cm (1 inch) as adults
  • Have propeller shaped shells
  • Are brown or cream coloured, and may have zebra stripes (not distinguishing feature)
  • Often form in grouped clumps, like some marine mussels

mussel scale

invasive mussels

Native Freshwater mussels:

In comparison freshwater mussels native to B.C. are much larger and have a different shape and cannot attach to hard substrate.

  • Most species' adults are far larger than zebra and quagga mussels >3 cm/1 inch
  • Either oval or heart shaped
  • Buried, partially buried or on soft substrate or between cobbles
  • Do not form clumps or attach to vertical surfaces

freshwater mussel with scale

freshwater mussel scale

Size Comparison Between Zebra & Quagga Mussels Versus Native Mussels

Invasive mussels comparison