Zebra Mussels

Zebra mussels are small non-native, clam-like, aquatic animals that are a significant environmental and economic concern to Manitoba. Native to Eastern Europe and Western Asia, zebra mussels have caused millions of dollars in damage to the Laurentian Great Lakes area and have cost the North American economy billions of dollars to control.

A Zebra Mussel
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Zebra Mussel impact:

  • Aggressively invade new areas and reproduce quickly. A female zebra mussel can produce upwards of one million eggs per year.
  • Colonize almost any hard surface including watercraft hulls, motors or anything immersed in the water and can interfere with engine cooling systems.
  • Negatively impact essential power and water-based infrastructures by obstructing water-intake pipes, such as, for public drinking water supply and cooling systems.
  • Threaten native fish and wildlife by reducing species of algae and microscopic aquatic animals that are important for the food chain. Zebra mussels attach to native mussels and crayfish making it hard to them to survive.
  • Costly nuisance to boaters, commercial fishers, anglers, and beach-goers. Zebra mussels can reduce recreational potential by littering beaches with numerous sharp shells and producing foul odours from decaying, dead zebra mussels. They can clog watercraft water intake pipes causing costly repairs

Zebra mussels colonizing a native clam making feeding difficult
Zebra mussels colonizing a native clam making feeding difficult.
Photo credit: Randy Westbrooks USGS Budwood.org

How to identify an adult Zebra Mussel:
  • Usually 1 to 3 cm (0.4 - 1.2 inches) long.
  • Triangular, or "D"- shaped shell.
  • Most have light and dark brown bands on shells (Figure 1).
  • Adult shells have very strong tufts of hair-like filaments, called byssal threads.
  • Usually grow in clusters containing numerous individuals.
  • Zebra mussels and quagga mussels are the ONLY freshwater mussels that attach firmly to surfaces, including rocks, watercraft hulls etc. Native mussels will bury into soft substrates on lake and river bottoms.
  • Unlike adults, young zebra mussels, called veligers, in their larval stage are free-swimming and microscopic; they are difficult to see with the naked eye.