Zebra and/or quagga mussels have been identified in moss ball products sold in stores in Canada.
We urge everyone who may have purchased moss ball products in Canada or online to dispose of them responsibly.
Source: Department of Fisheries & Oceans
Identifying features
Zebra Mussels (Dreissena polymorpha) are freshwater hinged mollusks. You can identify them by their:
 | – flat underside – triangular shape – varying zigzagged patterns of black or brown with white and yellow average size of 2 to 2.5 cm, reaching up to 4 cm long |
The Zebra Mussel resembles the Quagga Mussel; however, the Zebra Mussel is smaller, more square, and narrower while the Quagga Mussel has a rounded underside.
Impacts
Zebra Mussels are filter feeders that attach themselves to solid surfaces. They breed very quickly, as females can release up to one million eggs each breeding season. After the eggs are fertilized, larvae (called veligers) emerge and are free-swimming for up to a month. The combination of these factors mean that Zebra Mussels can colonize in densities over 700,000/m2 on surfaces such as:
- docks
- rocks
- plants
- native mussels
Ecological Impacts
Zebra Mussels can have significant negative impacts on freshwater habitats by out-competing native species for food. This affects the composition of other communities within the ecosystem by:
- altering food webs by removing native species’ food sources, such as plankton
- affecting fish spawning areas by changing important substrates, which impacts the survival of fish eggs
- creating clearer water, which:
- allows sunlight to penetrate deeper
- increases the growth of submerged aquatic vegetation
- leads to toxic algal blooms as Zebra Mussels do not feed on toxic algae
- increases pathogenic bacteria, avian botulism, and localized anoxia
Zebra Mussels are especially harmful for native mussels, many of which are species at risk. They outcompete these species for food and will attach themselves to native mussels, suffocating them.
Socio-economic impacts
In Canada, Zebra Mussels cause millions of dollars in damage every year by clogging intake structures in power stations and water treatment plants as well as damaging watercrafts.