Zebra and quagga mussels are bivalve molluscs. Zebra are native to the Black, Caspian and Aral seas, and quagga to the estuarine regions of rivers in the Ukraine. These mussels expanded their range westward with the construction of interbasin canals along large European rivers during the mid-1900s. Both species were introduced to the Great Lakes likely via ballast water discharge in the late 1980’s.

Zebra and quagga mussels have separate sexes and eggs are expelled by females to be fertilized outside of the body by males, usually in the spring or summer. The microscopic larvae, called veligers, emerge within 3-5 days and are free swimming for up to a month, being dispersed by water flow. After this time the veligers search for an attachment site, and metamorphosis and secretion of the adult shell begins. The mussels may reach maturity in the first year, but the second year is more usual. A fully mature female mussel is capable of producing up to one million eggs per season. These non-native mussels are filter feeders and each mature adult is capable of filtering at least one litre of water per day, removing plankton, algae, and even their own veligers. Any undesirable matter is ejected as pseudofeces. Filtering by these mussels increases water transparency and light penetration, decreased organic matter, and increased concentrations of ammonia, nitrates, and phosphates. Only certain algal species are consumed - cyanobacteria are not - leading to toxic algal blooms, which deplete the oxygen in the water, killing fish and plants

Zebra and quagga mussels will colonize surface standing or running waters, inland water bodies, estuaries, and brackish coastal estuaries. The salinity, pH and temperatures of Alberta’s lakes are well within the range of tolerance and optimal growth for both mussels. Water velocities exceeding two metres per second inhibit attachment.

Dreissenids are the only freshwater bivalves that attach themselves to hard substrates. Reproduction is prolific and once introduced to a new water body populations can reach a total biomass at least 10 times that of all other invertebrates. They attach themselves to hard surfaces by byssal threads, which are secreted from a byssal gland. They will attach to rocks, wood, some plants, and manmade materials such as concrete, metal, nylon, and fiberglass. All native mussels are free living and do not attach to anything

Prevention is so important for zebra and quagga mussels because once they establish in a natural body of water there is very little chance of eradicating them. Learn to recognize the physical characteristics of zebra/quagga mussels and know whether a body of water you enter is infested. The larval veligers can survive several days out of water in a moist environment like ropes, flotation vests, bilges, wet clothing, etc.