New Zealand Mud Snail
Potamopyrgus antipodarum

New Zealand Mud Snail is a small freshwater snail.

Report a discovery in an unlisted area

If you think you’ve seen or caught a New Zealand Mud Snail:

  • Do not release it into the water.
  • Catch it and keep it frozen. If you can’t do that, destroy it.
  • Note the location (with GPS coordinates if possible) as well as the observation date.
  • Contact Fisheries and Oceans Canada.

Identifying features

The New Zealand Mud Snail can easily be confused with various native species, although its shell is narrower, longer, and has 7 to 8 whorls than native species'. These are grey to dark brown in colour and about six millimetres long. The shell opening is round to slightly oval and, if the snail is held tip down with the shell opening toward you, the opening will appear on the left.

Where it has been found

New Zealand Mud Snail was introduced to the Great Lakes in 1991 and, more recently, was identified on the west coast of Canada in 2006.

In B.C., New Zealand Mud Snails have been reported at Port Alberni on the west coast of Vancouver Island. As the species was only recently identified in B.C., it is unclear if this is the only location where they can be found. Efforts are currently underway to determine if this species is more widespread.

Ecological and economic impacts

New Zealand Mud Snail reaches extremely high densities, up to 300,000 individuals per square metre have been recorded. It may compete with native snails for food and space. Females mature rapidly, becoming sexually mature at three to six months of age. It only takes one female to start a colony in water because they are self-reproducing and bear live, well developed clones, which contribute to long-term survival.

Origins and mode of arrival

Native of New Zealand

Since its introduction to the US in the 1980s it has spread rapidly. New Zealand Mud Snails can be transported from one body of water to another by birds and other wildlife, as well as by boaters, anglers, and researchers. This species is very resilient and can survive for extended periods out of water.

Mode of dissemination

New Zealand Mud Snail will disperse mainly through ballast water (especially for Great Lakes) and aquaculture (putative source of introduction to western North America).

It can also disperse by numerous other vectors, including fish culture, stocking, boat trailers, dredging, movement through migratory birds, livestock, water flow, volition/move upstream.

Government action

Scientific research

Fisheries and Oceans Canada is studying the New Zealand Mud Snail population to improve its understanding of how it reacts and adapts to Canadian conditions.

For further information


DFO. 2010. Proceedings of the CSAS Peer-review of the risk assessment for New Zealand Mud Snail in Canadian waters; 24-25 March 2010. DFO Can. Sci. Advis. Sec. Proceed. Ser.2010/023.

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