New Zealand Mudsnail
Potamopyrgus antipodarum

The New Zealand mudsnail (Potamopyrgus antipodarum) is a small aquatic snail.  As its name states, this species is native to freshwater lakes and streams of New Zealand.  Like many organisms today, it is being incidentally carried to many locations around the world such as Europe, Asia, and North America. In the U.S., this snail was first detected in the mid-1980s in the Snake River region of Idaho.  Since then, it has spread to waters of Montana, Wyoming, California, Arizona, Oregon, and Utah. They have even found their way into the waters of Yellowstone National Park.  The only known population in the eastern U.S. is in Lake Ontario where a population was discovered in the early 1990s.

Photo Gallery

Mudsnail densities of over one-half million per meter square in western streams are a cause for concern. Because the West is known for abundant trout and productive fishing spots, there is concern that the mudsnails will impact the food chain for native trout and the physical characteristics of the streams themselves.  Research is needed to determine the impacts of large populations of mudsnails on the native fauna, such as aquatic insects and native snails, and on any changes in the physical environment.  The images above are New Zealand mudsnails collected from southwestern Montana either in or near the Madison River.

Current Distribution Map of the New Zealand mudsnail, Potamopyrgus antipodarum, populations in the U.S. To view a list of documented occurrences, click here.

Link to: New Zealand Mudsnail in the Western USA
Click here for a printable FISC Information Bulletin
Go to NAS Mollusk page
Submit a Sighting

or Amy Benson
abenson@usgs.gov