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Natural Heritage and Endangered Species

Zebra Mussel Life History

Zebra mussels are small freshwater mollusks (fingernail sized) with a striped pattern on their shell. They typically live 2 to 5 years in Zebra Musseltemperate climates. This is the only freshwater mussel that can attach to a hard surface. Zebra mussels breed prolifically and can form dense clusters, in some cases over 700,000 per square meter.

(Photo Source: US Geological Survey)

Zebra mussels are native to the Eastern Europe/Western Asia and are believed to have been transported by freighters from European ports in ballast water, which was discharged into the Great Lakes. They were first discovered on this continent in 1988 in Lake St. Clair.

Zebra Mussels Sighting Distribution Map - USGS (updated daily)

NATURAL HISTORY

  • Zebra mussels reach sexual maturity after 1 or 2 years.
  • Optimal spawning temperature: >54°F.
  • External fertilization method by release of eggs and sperm directly into surrounding waters.
  • Up to one million eggs per female in a spawning season.

Life Cycle

Zebra mussels have a free floating larval stage and an attached adult stage.

Larval Stage

The larvae, called veligers, emerge within 3 to 5 days and are free-swimming for up to a month. Veligers are microscopic in size (0.04 -0.07mm) and can be found in densities of 500,000 per cubic meter. Optimal temperatures for larval development range from 68-72°F. Under the right environmental conditions, the veligers can survive 3-5 days in moist conditions.

Zebra Mussel Life Cycle

(Image Source: US Fish and Wildlife Service)

Juvenile Stage

After about a month, the veligers settle to the bottom and crawl about by means of a "foot" in search suitable substrate. They prefer a hard or rocky substrate, but have been known to attach to vegetation. Juveniles tend to settle and attach near or on the shells of established adults by means of a byssus (threads). Juveniles have a difficult time staying attached when water velocities exceed 6 feet per second.

Adult Stage

After one or two years, the mussels become adults and can begin reproduction. Natural populations of 5,000 to 30,000 individual mussels per square meter are not uncommon.

Feeding

Zebra mussels are filter feeders-an adult mussel can filter one quart of water/day. They feed primarily on phytoplankton and zooplankton but also bacteria and detritus. Filter feeding will removes virtually all suspended particulate matter from the water. Intra-specific competition for food can be a significant population-regulating mechanism.

HOW ZEBRA MUSSELS SPREAD

Within a Waterbody

Veligers (larvae) disperse passively as plankton.

Between Waterbodies

The microscopic veligers may be transported by live wells, bait buckets, bilge water, dive gear, waterfowl, and nearly anything else that goes from one waterbody to another.

Adult and juvenile mussels are transported on boat hulls, sea planes, docks, and buoys moved from one waterbody to another.

HABITAT

Zebra mussels can be found in freshwater lakes, ponds, and rivers. They will be found on all kinds of hard surfaces including: rocks, wood, vinyl, metal, and cement. Other species such as crayfish, turtles and even other mussels are also suitable substrates. Zebra mussels can also attach to aquatic plants.

Water Chemistry Needs

Zebra mussels are found in water temperature ranging from 32 - 90 °F; optimal temperatures are 63 - 74°F. They will survive in water with a pH range of 7.4 - 9.0 and calcium of 20 - 125 parts per million. Their dissolved oxygen needs are 8-10 ppm.

Potential Zebra Mussel Habitat in Massachusetts
From: Douglas Smith, UMASS, Amherst, 1993


Potential Zebra Mussel Habitat in Massachusetts

The above information was derived from a review and subsequent presentation by DFW staff about zebra mussels made at a Fisheries and Wildlife Board Meeting on July 28, 2009.