Zebra Mussel Life History

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Zebra mussels are small freshwater mollusks (fingernail sized) with a striped pattern on their shell. They typically live 2 to 5 years in temperate 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.

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 Sightings Distribution Map - USGS (updated daily)

Natural History

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

Spawning

Zebra mussels reach sexual maturity after 1 or 2 years, and one female can release up to one million eggs in a spawning season. External fertilization occurs when eggs and sperm are released directly into surrounding waters. Optimal spawning temperature: >54°F.

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.

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.

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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)

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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.

Zebra Mussel Impacts

The presence of zebra mussels in Massachusetts presents a variety of ecological, recreational and economic concerns.

Native Species at Greatest Risk

As of July 28, 2009, the Division of Fisheries and Wildlife has identified native species on the Massachusetts Endangered Species Act list that are at greatest risk from the presence of zebra mussels in the western part of the state.

Housatonic River Drainage

  • Boreal Marstonia (Marstonia lustrica) State Endangered

Connecticut River Drainage

  • Yellow Lampmussel (Lampsilis cariosa) State Endangered
  • Dwarf Wedgemussel (Alasmidonta heterodon) State & Federally Endangered
  • Brook Floater (Alasmidonta varicosa) State Endangered

Potential Ecological Effects

The possible ecological effects of zebra mussels include:

  • Reduction in density levels of phyto- and zooplankton
  • Diversion of energy from pelagic community to benthic community
  • Water quality-increased water clarity/plants
  • Fisheries community
  • Biomagnification of toxics in the food web

Zebra mussels can dominate the invertebrate community both in density and biomass in benthic communities. The mussels may either displace or reduce the abundance of indigenous species.

Industrial Impacts

Raw water intakes such as those at drinking water, electric generation, and industrial facilities can become blocked with zebra mussels.

 

Recreational Impacts

  • Beaches may be impacted by the sharp shells that wash up in shallow areas, which can cut bathers and litter beaches.
  • Decomposition of mussels can also create obnoxious odors.
  • Zebra mussels attached to boat hulls can increase drag and reduce speed resulting in increased fuel consumption in motorized boats.
  • Mussels clog engine intake.
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Photo Source: Wisconsin Dept.. Natural Resources/ Ontario Ministry of Natural Resources
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Photo Source: ZeeStop Company, Ontario, Canada
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Photo: Water Education Foundation, California

Zebra Mussel Management Efforts

The experience of other states shows there is no practical method to eradicate zebra mussels once they have become established in a waterbody.

Public education to reduce risk of human caused spread between water bodies is the best defense.

A couple of examples from neighboring states are instructive:

     Vermont--Zebra mussels were discovered in Lake Champlain in 1992. Since that time, only three other lakes have been infested.

     Connecticut--Zebra mussels confirmed East and West Twin Lakes in 1998 and 2001. No other lakes infested in the state.

Both states engaged in education efforts targeted at the various user groups of lakes and ponds to slow the spread of zebra mussels and other invasive species.

WHAT YOU CAN DO

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Help Stop The Spread of Invasive Species

  • INSPECT boat, trailer, and other recreational equipment that have been in contact with water.
  • REMOVE all mud, plants, or animals.
  • DRAIN all bilge water, live wells, bait buckets, and all other water from your boat, engine and equipment.
  • WASH all parts of your boat/paddles/other equipment that have been in contact with water. Do not allow wash water to flow into any water body or storm sewer.
  • DRY boats and trailers in sun for FIVE days before launching into another waterbody.

Table of Zebra Mussel Disinfectants and Usage Guidelines for Boats and Related Equipment