New Zealand Mudsnail

Potamopyrgus antipodarum

Invader Images

    • New Zealand mudsnail size references
      New Zealand mudsnails are small, but can reach very high population densities
    • New Zealand mudsnails quickly overwhelm benthic communities
      Eurasian watermilfoil underwater (Photo credit: Washington Department of Fish and WIldlife)


New Zealand mudsnail will grow to lengths between 5 and 8 mm (0.2-0.3 in). They have a right handed spiral, and can either have a smooth or keeled shell, depending on the morph. The shell color appears in varying shades of brown.



The New Zealand mudsnail is native to freshwater streams and lakes of New Zealand and nearby islands.


Typically found in slow-moving, fresh water, the New Zealand mudsnail has been found in lentic environments up to 25 meters in depth, and is known to inhabit waters varying widely in temperature (0-34 degrees Celsius) and flow rate.

Ecological Threat

This species is not yet found in Lake Champlain. The New Zealand mudsnail has the potential to yield populations with densities over 300,000 individuals per square meter. While direct effects of this mudsnail are unknown, it has potential to compete for resources with native fish and macroinvertebrate species. They can also clog infrastructure and cause other social issues similar to other prolific invading mollusks, such as zebra mussels.

Management Options

Legal Status

There are regulations surrounding commercial sale and shipment of the species, but no legislation regarding transport in Vermont exist for the New Zealand mudsnail.

Control Options & Examples

Decontaminating boats and fishing/sport equipment, as well as draining motors and live wells can help prevent the spread of New Zealand mudsnail.

Vermont Distribution

New Zealand mudsnails have yet to be documented in any Vermont waterbody. They have invaded much of the Great Lakes, however, as well as many western lakes and rivers.Species distribution in the United States

How You Can Help

For most aquatic invasive species, humans are the primary vector of transport from one waterbody to another. Many of these nuisance plants and animals can be unknowingly carried on fishing gear, boating equipment, or in very small amounts of water in a watercraft. The easiest and most effective means to ensure that you are not moving aquatic invasives is to make sure that your vessel, as well as all your gear, is drainedclean, and dry.


  • CLEAN off any mud, plants, and animals from boat, trailer, motor and other equipment. Discard removed material in a trash receptacle or on high, dry ground where there is no danger of them washing into any water body.

  • DRAIN all water from boat, boat engine, and other equipment away from the water.

  • DRY anything that comes into contact with the water.  Drying boat, trailer, and equipment in the sun for at least five days is recommended. If this is not possible, then rinse your boat, trailer parts, and other equipment with hot, high-pressure water.

Interested in monitoring for aquatic invasives?


Hall, R.O., Jr., J.L. Tank, and M.F. Dybdahl. 2003. Exotic snails dominate nitrogen and carbon cycling in a highly productive stream. Frontiers in Ecology and the Environment 1(8):407–411.

U.S. Environmental Protection Agency (USEPA). 2008. Predicting future introductions of nonindigenous species to the Great Lakes. National Center for Environmental Assessment, Washington, DC; EPA/600/R-08/066F. Available from the National Technical Information Service, Springfield, VA, and

Zaranko, D.T., D.G. Farara, and F.G. Thompson. 1997. Another exotic mollusk in the Laurentian Great Lakes: the New Zealand native Potamopyrgus antipodarum. Canada Journal of Fisheries and Aquatic Science 54:809-814.