zebra mussel

Zebra mussels (Dreissena polymorpha) are one of the most widespread invasive freshwater animals in the world. They cause economic harm in North America of over one billion dollars per year. Their huge populations attach to hard surfaces, clog intake pipes for water treatment and power generating plants, encrust boat motors and hulls, may greatly reduce lakefront property values, and their sharp shells cut swimmer’s feet. Ecologically, they filter enormous quantities of microscopic algae and alter energy flow through aquatic ecosystems — with potentially large impacts on fish populations — and they smother and cause extinctions of native bivalve mollusks.

At MAISRC, researchers are sequencing the genome to identify control options, using population genetic and genomic markers to study spread throughout Minnesota, estimating the contribution of veliger larvae in residual water to the risk of spread from high-traffic lakes, developing quantitative molecular tests for the early detection of larvae in lakes, studying the effectiveness of pesticide treatments in lakes, and characterizing the microbiota in and around zebra mussels to determine if it contains potential biocontrols. Click here to download a factsheet about zebra mussel research at MAISRC.

About zebra mussels

What they look like

zebra mussel

Zebra mussels are ¼-1 ½ inch-long bivalve (2-shelled) molluscs. They evolved from ancestors similar to surf clams (used to make clam chowder) that invaded fresh waters in southern Russia. They have a D- or wedge-shaped shell, which is often marked by alternating brown and yellow bands in a zigzag pattern. They live on lake and river bottoms, rocks, aquatic plants, docks, lifts, and boats to which they attach using small dark fibers called "byssal threads." Viewed up-close underwater, two tiny siphons can be seen projecting into a narrow gap between the shell valves of each animal — these siphons are used to pump water for respiration and feeding.

Life cycle 

Each mussel is either male or female, and they release eggs (500,000 or more per female per year) or sperm into the water. Fertilization yields a tiny (< 1/10th millimeter) larva called a veliger — found in very few other freshwater molluscs. Veligers feed on algae and grow for about 3 weeks, drifting in the plankton, during which time wind and currents can transport them over large distances. After this, they settle down and attach to the lake or river bottom, and after about 12-18 months, they grow to reproductive size.

Where they're found

Zebra mussels are native to large rivers and lakes draining into the Black, Caspian, and Azov Seas of southwestern Russia and the Ukraine. Beginning in about 1800, they began spreading across western and northern Europe and most recently have reached inland waters in the British Isles, Spain, Portugal, and France. They appeared in North America in 1988, and in five years they spread rapidly throughout the Great Lakes and large rivers. In several Great Lakes (particularly Michigan and Erie) zebra mussels have been largely replaced by a related species — the quagga mussel (D. bugensis) — also from the Black Sea. Zebra mussels arrived in the Duluth Harbor in 1989 and the Mississippi River in 1993. As of 2015, they have been found in approximately 82 lakes and 12 rivers and streams in Minnesota.

How they spread zebra mussel

In the 19th century, zebra mussels spread throughout Europe in man-made canals, and in the late 20th century, on recreational watercraft and the nets of commercial fisherman. They were also spread to lakes in Poland and Belarus on the nets of commercial fisherman. In North America, barge traffic and (to unknown extent) larval dispersal were responsible for rapid initial spread throughout the Great Lakes, Mississippi, Ohio and Susquehanna Rivers. Spread to inland lakes has occurred by larvae transported down connected streams and waterways, and overland via mussels attached to vegetation and to surfaces of recreational boats, trailers, docks and lifts. Veliger larvae may also be transported in the "residual water" remaining inside boat compartments when trailered boats are moved between waterways.

Get involved

If you're interested in monitoring your lake for zebra mussels, read these new statewide protocols for early detection monitoring for zebra mussels. You can use the monitoring protocols in this document to assist in early detection monitoring for zebra mussels in a lake where zebra mussels have not yet been found and to apply for treatment if zebra mussels are detected. Or, consider becoming an AIS Detector or AIS Tracker.

Related news

Zebra mussel research at MAISRC

zebra mussels


Current efforts 

  • Sequencing the zebra mussel genome in collaboration with the University of Minnesota Genomics Center. This will allow researchers to analyze the genome and transcriptomes of expressed genes to find genes that could potentially be targeted for control.

  • Also in collaboration with UMGC, using population genetic and genomic markers to study spread throughout Minnesota. Highly variable genetic markers are being used to discriminate the sources of zebra mussels that infest inland lakes and rivzebra musselers, and to thereby determine spread pathways. These genetic results will be used to better target prevention.

  • Developing a decision-making tool that will help AIS managers, counties, and other agencies prioritize their resources for optimal prevention and intervention of AIS, including zebra mussels. This tool will take into account the likelihood of a species getting to a lake and its likelihood of survival, based on several variables including temperature, pH, and precipitation.

  • Partnering with the Minnesota Department of Natural Resources' Watercraft Inspection Program and Tonka Bay Marina and the Brunswick Freshwater Boat Group to estimate the contribution of veliger larvae in residual water (water that is left after boats are drained) to reduce the risk of spread from high-traffic lakes.

  • Characterizing the total microbial community associated with zebra mussels across time and space to see if any pathogenic relationships occur that could be developed into a biocontrol.

  • Creating a new, rapid molecular assay for the early detection and quantification of zebra and quagga mussel larvae. Once automated, this assay will be a very rapid way to screen water bodies for early detection.
  • Developing recommendations for underwater survey methods to estimate zebra mussel population abundance and distribution in newly infested lakes which will guide treatment options and post-treatment monitoring.

  • Quantifying the impacts of zebra mussels on walleye and their food webs in large lakes in order to identify management strategies.

  • Establishing how far zebra mussel larvae can spread down small rivers and streams. Research has shown that settlement of mussels occurs only a short distance down from the upstream lake. Small streams can carry large numbers of larvae down short (<10 miles) stretches of streams; over longer distances results depend on the lake/river — it was found that concentrations always drop, but not to zero in every case.

  • Evaluating the toxicity of low-dose molluscicide treatments for zebra mussel veligers

  • In partnership with the USGS, developing a set of rapid response protocols for treating localized zebra mussel infestations. The protocols, which will take water temperature into account for the first time, will provide managers with a critical support tool to swiftly select the correct molluscicide, determine the treatment concentration, and determine the treatment duration.

Current projects

Completed projects