New Zealand Mudsnail
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
- 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 livewell and bilge.
- Rinse waders, hip boots, and gear with hot water (113° F/45° C), OR
- Dry gear for five days before reuse.
- Report new sightings - note exact location; place specimens in a sealed plastic bag or store in rubbing (isopropyl) alcohol; and call Minnesota Sea Grant Program in Duluth, (218) 726-8712, or the Minnesota Department of Natural Resources in St. Paul, 1-888-MINNDNR or (651) 259-5100, or a local DNR fishery office.
Know the rules!
Specimens are needed to confirm sightings, but some jurisdictions prohibit possession of invasive aquatic animals and plants. Contact your local natural resource management agency for instructions.