Manitoba Water Stewardship
The Zebra Mussel (Dreissena polymorpha)
Zebra mussels are small, 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.
Figure 1. A zebra mussel.
Photo credit: Ohio Sea Grant
ZEBRA MUSSEL IMPACTS:
- 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 (Figure 2).
- 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
Figure 2. 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 are the ONLY freshwater mussel that firmly attaches itself to solid objects, 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.
No. To date, live zebra mussels have not been found in Manitoba - but they are in the United States portion of the Red River.
On July 1, 2010, microscopic, larval zebra mussels were found for the first time in the Red River. The mussels were found where the Ottertail River empties into the Red River at Wahpeton, North Dakota and Breckenridge, Minnesota. This is the first time zebra mussels have been reported in North Dakota.
Previous to this, live zebra mussels were found in (Big) Pelican Lake, Minnesota approximately 50 kilometres south east of Fargo, North Dakota and Moorhead, Minnesota in September 2009. This was the first know incidence of zebra mussels in the Red River watershed.
Zebra mussels were likely transported into Pelican Lake by unsuspecting boaters who previously launched their boat in zebra mussel-infested waters.
Waters from Pelican Lake flow into Pelican River, which flows into the Ottertail River near Fergus Falls, Minnesota and then into the Red River at Breckenridge, Minnesota. All water that originates in the Red River watershed eventually flows into Manitoba and Lake Winnipeg (Figure 3).
Since the initial introduction in North America in 1985, zebra mussels have steadily invaded south-eastern Canada and the majority of the eastern half of the United States. They have infested the Laurentian Great Lakes, and the Hudson and the Mississippi drainage areas (Figure 4). Zebra mussels are also found in parts of California, Arizona, Nevada, Utah, Colorado and Texas.
Figure 3. Distribution of zebra mussels in the Red River watershed.
Figure 3.Distribution of zebra mussels in the Red River watershed.
Figure 4. Distribution of zebra mussels in south-eastern Canada and the eastern half of the United States (Update January 2010).
Figure 4.Distribution of zebra mussels in south-eastern Canada and the eastern half of the United States (Updated January 2010).
HOW CAN ZEBRA MUSSELS SPREAD?
Each year thousands of tourists, recreational boaters and anglers flock to Manitoba's numerous lakes and rivers. With this comes the threat of transporting zebra mussels overland to new areas on watercraft, trailers and gear.
Because they can close their shell, adult zebra mussels are able to survive out of water for up to 15 days in cool, damp conditions. As a result, they can easily be transported long distances on firm surfaces such as:
- watercraft,
- motors,
- fishing nets,
- aquatic plants/debris,
- scuba equipment,
- scientific sampling equipment,
- float plane pontoons, and
- related equipment.
Young, microscopic zebra mussels can die quickly out of water. However they can easily survive and be transported to new in-infested areas in almost any remaining water found in:
- livewells,
- motor compartment,
- bait buckets, and / or
- bilge.
Once introduced into a new area, young (larval, free-swimming) zebra mussels can spread by:
- inter-connecting waterways, and
- illegal bait-bucket transfers, bilge or livewell discharges.
HOW YOU CAN HELP:
Help protect Manitoba's waters. Once zebra mussels establish in Manitoba, they are here to stay!
Before launching any watercraft into any Manitoba waterbody such as a lake, river or wetland, and before leaving the boat launch:
CLEAN watercraft, trailer, equipment and gear.
- Remove all visible plants, animals and mud.
- Rinse using very high pressure, hot tap water - preferably 50 oC (120 oF).
- Inspect drain holes, speedometer brackets, motors, propellers, and other difficult to clean areas, including the trailer and vehicle (Figure 5).
Figure 5.Common places where adult and larval zebra mussels can be found on boat, trailer and vehicle.
Image courtesy of California Department of Fish and Game
DRAIN all water from the motor, livewell, bilge and bait buckets.
DRY your watercraft for at least 5 days in the hot sun (if rinsing with a high pressure, hot water washer is not available). Or dry for 18 days in the spring/fall or 3 days of freezing.
- Young zebra mussels can die quickly out of water; adults can survive up to 15 days in damp conditions.
DISPOSE of unwanted live bait and
worms in the trash, and dump bait bucket water on land.
Never release aquarium pets,
plants or water into our lakes, rivers or wetlands.
Background Information:
WHERE DID ZEBRA MUSSELS ORIGINATE?
Zebra mussels are native to the Caspian, Black and Azov seas of Eastern Europe; they were initially discovered in the Caspian Sea in 1769.
Scientists first discovered a population of zebra mussels in Lake St. Clair in 1988. The zebra mussels were likely transported to North America in the ballast water of a ocean-going ship. This ballast water was then discharged in Lake St. Clair, Ontario, likely in 1985 or 1986.
WHAT ARE ZEBRA MUSSELS?
The zebra mussel (Dreissena polymorpha) is a small aquatic animal that resembles freshwater clams. Zebra mussels grow up to five centimetres (two inches) in length and may live up to five years. Their name originated from the brown and white striped colour of its shell. One mature female zebra mussels can produce up to one million eggs per year depending on water quality conditions.
The eggs hatch into free-swimming microscopic larvae called veligers. During this stage, which lasts for approximately 8 to 33 days, the larvae remain suspended in the water. It is during this stage that the veligers can be transported undetected from lake to lake in bait buckets, live wells, and bilge water.
The distribution of zebra mussels is thought to be controlled mainly by temperature and calcium concentration in the water. They begin laying eggs when water temperatures rise to approximately 12 ºC and continue until it cools below this temperature in the fall. Calcium is required for mussels to develop their hard shell.
Adult zebra mussels can survive out of water, in moist conditions, for up to two weeks. They attach to boats or other equipment being transported from one body of water to another and easily spread to new areas.
CURRENT MANITOBA REGULATIONS:
Zebra mussels are listed on the Manitoba Prohibited Species List (Schedule IX) of the Manitoba Fisheries Regulations under The Fisheries Act.
Please Conact:
Manitoba Water Stewardship, Water Science and Management BranchWater Quality Management Section
123 Main Street, Suite 160
Winnipeg, Manitoba, R3C 1A5
Telephone: (204) 945-8146 or (204)945-7095
Fax: (204) 948-2357
Email: mws@gov.mb.ca
