Return to the Wild - Evolving perspectives on Canadian wildlife
The zebra mussel is not native to Canada but now flourishes in the Great Lakes and beyond.

Did you know?

In one year, a female adult zebra mussel can produce from 30,000 to one million eggs.

Scientific name: Dreissena polymorpha
Average length: 2 cm–4 cm
Average lifespan: 2–4 years
A woman holds a stick with many zebra mussels attached to it.

Our changing understanding

Faster than you can say “bivalve,” the zebra mussel has made its way from Europe to infiltrate the lakes and waterways of Canada in staggering numbers.

Reports in the magazine document the mussel’s appearance in Canadian waters in the 1980s. By the 1990s, the insidious mollusc can be found in concentrations of up to 350,000 per square metre (in Europe, the average is about 5,000 per square metre). The Great Lakes system, including the St. Lawrence River, is affected, as are smaller lakes, such as Muskoka.

However, the presence and grudging acceptance of the zebra mussel show a shift in approaches to invading foreign species. A bit of picking your battles and learning to live with a species has been Canada’s response to the animal.

Although scientists have suggested methods of destroying the mussels, such as ultraviolet rays, chemicals and pathogens, the techniques aren’t considered environmentally safe or entirely effective. Gone are the days of the DDT cure-all; more long-term thinking must be employed. One preventive measure is to require international ships destined for Canadian waters to do a mid-ocean exchange of fresh water for salt water in bilges to reduce the possibility of introducing stowaway animals from afar. And while this method is effective only two-thirds of the time, it illustrates a change in thinking — a change for the better.