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New Zealand Mudsnails (NZM) (Potamopyrgus antipodarum) are native to freshwater streams and lakes in New Zealand and the surrounding islands. In New Zealand, NZM do not pose problems because native parasites and predators help to keep their populations in check. NZM have been spread widely into other countries, including the United States, most likely due to anthropogenic intervention. NZM have no natural predators or parasites the United States and, as a result, have become an invasive species in this country.


    • 1987 - First discovered in the U.S. in Idaho's Snake River
    • 2006 - Spread through Western U.S. States and found throughout Lake Erie, as well as four of the five Great Lakes
    • 2010 - NZM detected in Spring Creek in Centre County, PA
    • 2014 - Abundance and distribution of NZM increased in the Spring Creek basin
    • 2021 - NZM populations have been found in many waters throughout the commonwealth and the United States [VIEW USGS MAP​]

The North American NZM can reproduce asexually and can quickly overtake an ecosystem by outcompeting native snails and other macroinvertebrates. Because of their very small size and resistance to desiccation and cleaning agents, NZM can easily be spread on waders and other fishing gear. 


In May 2022, the Pennsylvania Fish and Boat Commission (PFBC) confirmed the presence of invasive New Zealand Mudsnails within portions of the Benner Spring and Pleasant Gap State Fish Hatcheries in Centre County.  Since those detections, the first within the state fish hatchery system, the PFBC has been working under the guidelines of a special response plan to prevent further spread within the hatchery system and cooperative nurseries.  This includes enhancements to biosecurity, disinfection of hatchery facilities including fish raceways, the establishment of quarantine zones for the monitoring of groups of fish, and investigation of water sources.  To date, no New Zealand Mudsnails have been detected in areas of the state fish hatcheries where fish are contained. 

Read AIS Control Plan for New Zealand Mudsnails

Read Press Release


Tips for New Zealand Mudsnails:

  • Freezing gear for a minimum of six hours.
  • Soaking gear in hot (>120 Fahrenheit) for at least five minutes
  • Dry gear completey for at least 5 days

Tips for Other AIS:

    • When retrieving your boat for the day, check the boat, motor and trailer for weeds and other things "tagging along."
    • Wash your boat's hull with hot water or with a high-pressure spray.
    • Drain livewells, bilges and other compartments.
    • Drain all standing water from your boat.
    • Don't dump leftover bait into the water you're fishing, unless you collected the bait there.


Getting to Know New Zealand MudsnailsMan holding many New Zealand Mudsnails. Picture is linked to a video on Getting to Know New Zealand Mudsnails.

For more on cleaning boats and gear, visit our Clean Your Gear page.