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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 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 (shown below)

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

Read AIS Control Plan for New Zealand Mudsnails


Tips for New Zealand Mudsnails:

  • Freeze gear for a minimum of six hours.
  • Soak gear in hot (>120 Fahrenheit) water for at least five minutes
  • Soak gear in a 1:1 solution of Formula 409 Degreaser Disinfectant and water (other typical aquatic invasive species disinfection methods and other 409 brand products are not effective in killing NZM).

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


Getting to Know New Zealand Mudsnails