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New Zealand Mudsnail (Potamopyrgus antipodarum)

New Zealand mudsnails (Potamopyrgus antipodarum) are tiny invasive snails that threaten the food webs of trout streams and other waters. Native to New Zealand, they were first found in Idaho's Snake River in 1987. They quickly spread to other Western rivers, sometimes reaching densities over 500,000 per square meter. In the Great Lakes, mudsnails were first found in Lake Ontario in the early 1990s. In 2001, they were found in Lake Superior in Thunder Bay, Ontario, and in 2005 in the Duluth-Superior Harbor, likely spread by ballast water discharged from ships.

Anglers pose a risk for spreading New Zealand mudsnails because they can be moved on waders and gear. They can close their shells allowing them to survive out of water for days. One snail can reproduce and start a new infestation. Eradicating infestations is nearly impossible. Your help in detecting and reporting new infestations is vital for preventing their spread.

Identify New Zealand Mudsnails

General Characteristics

  • Small, up to 1/5 inch (5 mm) long
  • Difficut to distinguish from native snails; shell more elongated
  • Usually horn-colored, but ranges from light to dark brown

What You Can Do

  • Learn to recognize New Zealand mudsnails.
  • Inspect and remove visible aquatic plants, animals, and mud from waders, hip boots, and field gear before transporting.
  • Drain lake or river water from bilge, livewell, and motor before leaving access.
  • Dispose of unwanted live bait, worms, and fish parts in the trash.
  • Scrub soles of footwear with stiff bristled brush.
  • Rinseboat and equipment with high pressure, hot water, AND/OR
  • Dry everything for five days or more before reuse.
  • Report new sightings - note exact location; place specimens in a sealed plastic bag or store in rubbing (isopropyl) alcohol; and call the Minnesota Sea Grant Program in Duluth, (218) 726-8712; or a Minnesota DNR Invasive Species Specialist (see www.mndnr.gov/invasives/contacts.html), 1-888-MINNDNR or (651) 259-5100.

Know the rules!

Specimens are needed to confirm sightings, but some jurisdictions prohibit possession and transport of invasive aquatic plants and animals. Contact your local natural resource management agency for instructions. Unauthorized introduction of plants, fish, or invertebrates into thewild is illegal. Protect your property and our waters.

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This page last modified on July 26, 2013     © 1996 – 2016 Regents of the University of Minnesota     The University of Minnesota is an equal opportunity educator and employer.
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