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Zebra Mussels in Manitoba

Zebra Mussels in Manitoba

Zebra mussels are freshwater clams that are native to the Black Sea region of Eurasia. The introduction of Zebra Mussels into Canada began in the 1980s in Lake Erie. They now exist in up to 800 different lakes, mostly in eastern North America.   In Manitoba, zebra mussels are now found in the Red River and the South and North basins of Lake Winnipeg, as well as Cedar Lake.  One individual can produce up to 1 million eggs during a spawning event, making the zebra mussel a difficult pest to manage. Young zebra mussels, called veligers, are microscopic and free-swimming in the water column.

Zebra mussel adult showing actual size compared to a dime. Photo credit: Province of Manitoba, Department of Sustainable Development.

Like all clams, zebra mussels are filter feeders, eating any unsuspecting prey that gets caught in the current of water passing through them, and making the water clearer. But isn’t this a good thing? Unfortunately, zebra mussels remove beneficial algae and zooplankton from the water, having a negative impact on fish and smaller organisms that depend on that same food source. Toxic blue-green algae and long strands of filamentous algae are not eaten by zebra mussels, so their growth is encouraged.

Zebra mussel colony on a native freshwater clam. Zebra mussels have a negative impact on native clam populations. Photo credit: Province of Manitoba, Department of Sustainable Development.

Zebra mussels have sticky fibers called byssal threads which help them cling to surfaces, such as boats and equipment. Veligers are able to travel in even a droplet of water. It is illegal to transport zebra mussels in Manitoba, so it is vitally important that all boats and water equipment are cleaned with high pressure hot water (50 ºC or higher), drained and completely dried before being moved to another water body.  The adult can survive out of water for 7 to 30 days depending on temperature and humidity.

Zebra mussels are already washing up on beaches around Lake Winnipeg, and their shells are extremely sharp, causing a hazard for swimmers and barefoot beach visitors. They will impact us further by causing economic damage, affecting Lake Winnipeg fisheries, clogging water intakes and boat motors, and growing on hydroelectric dams leading to high maintenance costs.

Young zebra mussels growing in a water intake pipe. Photo credit: Province of Manitoba, Department of Sustainable Development.

For more information on zebra mussels and what you can do to stop aquatic invasive species, please visit Manitoba Sustainable Development’s Stop the Spread at http://www.gov.mb.ca/stopthespread/ais/ .

To report an invasion in a new water body, either use the online form at the above webpage, or contact 1-87-STOP AIS-0.

Written by Nathan Entz, Summer Interpreter

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