The facts: Zebra and Quagga Mussels

Invasive Species Council of BC 

Species: Dreissena polymorpha & Dreissena bugensis

Zebra (Dreissena polymorpha) and quagga mussels (Dreissena rostriformis bugensis) are fingernail-sized, freshwater mollusks that can easily attach themselves to objects and other organisms. They can clog pipes of water treatment and power plants, disrupt ecosystems with large monocultures, are difficult to remove and non-native to British Columbia. Zebra and quagga mussels are an ALERT SPECIES—currently they have not become established in Oregon, Idaho, Washington, Montana or British Columba—prevention is key!

Zebra mussels

Zebra Mussels

Zebra mussels grow up to 15 mm in size and have a “D-shaped” shell that can lay flat on surfaces. Their colour may vary from light to dark brown and the shell has obvious striping.

Quagga mussels grow up to 20 mm in size. Its shell is rounder in shape than the zebra mussel and does not sit flat. The color of the quagga shell is pale near its hinge and usually features dark, concentric rings.

The best identifying characteristic these two mussels share (which our native mussels do not have) are their tough byssal threads. Byssal threads are strong, sticky fibers that certain mollusks (including some mussels) use to attach themselves to rocks and other surfaces.

Both of these species originate from Europe. They were introduced to Canada (in the Great Lakes region) and the United States in the 1980s, as the result of ballast water being discharged by vessels travelling from Europe. Since then, mussels have been found in the Great Lakes in Ontario and Quebec, and in at least 24 American states as far west as California and Colorado.

Zebra and quagga mussels pose a serious threat to the biodiversity and fisheries of any water system, since they reduce the amount of food available for native fish (including salmon) and other organisms. Species that are dependent on plankton — such as sockeye salmon and kokanee — or species that feed on these plankton feeders (such as large-bodied strains of rainbow trout and bull trout) could be severely depleted if these mussels become established in BC’s lakes.

They can upset the balance of algae in an area, resulting in a higher concentration of blue-green algae. High levels of blue-green algae can become toxic to aquatic life, can cause taste and odor problems in drinking water supplies, and can be very unpleasant for recreational users.

These mussels create thick colonies on hard surfaces and can harm native mussels, clams, turtles and crustaceans by making it difficult for other organisms to feed. Their tissues can accumulate high levels of contaminants, which other wildlife become exposed to through the natural food chain.

Invasive mussels can colonize on boats and other watercraft (on hulls, engines and steering components), as well as on recreational equipment. If left unchecked, zebra and quagga mussels can restrict the effectiveness of engine cooling systems and damage boat motors. They also attach to aquatic plants and submerged surfaces, including piers, pilings, water intakes and fish screens.

Zebra and quagga mussels create massive colonies that can block water intakes and interfere with municipal water supplies, agricultural irrigation and power plant operations. BC power producers could end up spending hundreds of millions of dollars to protect and maintain hydro generation stations if these mussels become established in our province.

Zebra and quagga mussels can survive for several weeks without being immersed in water, if they’re left in a cool and moist environment. This means that live mussels attached to recreational vehicles, boats, boating equipment and fishing gear can be easily transferred from one body of water to another.

Adult mussels can attach themselves to boat hulls, trailers, motors, vegetation and equipment. The sticky fibers that they produce (byssal threads) make it easy for them to “hitchhike” on hard surfaces. Immature mussels (“veligers”) can float undetected in water in bait buckets, fishing gear, live-wells, pumps and bilges.

The public has an important role to play in the battle against invasive mussels. Anglers and recreational boaters who are transporting boats by trailer into BC from other provinces and states should ensure they have thoroughly cleaned, drained and dried their boats and equipment to remove any visible mud, plants, fish or animals.

If the boat (or other water-based recreational equipment) has come from a known or suspected mussel-infested area, it must be totally drained (including components such as bilges, pumps, intakes, etc.) and must not be put into any body of water for 30 days.

Within BC, it is important for all boaters and anglers to completely CLEAN, DRAIN and DRY their boat and equipment before putting the boat into a new body of water. Please report ALL sightings of zebra or quagga mussels to the Report All Poachers and Polluters (RAPP) hotline: 1-877-952-7277


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