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Stop the Spread of New Zealand Mudsnails in Our Rivers

If you visit a site where New Zealand Mudsnails (NZM) have been found, taking some precautions will help prevent the snail from spreading to nearby streams.


Avoid wearing felt-soled waders with detachable neoprene booties. Tiny snails and other invasive species can hide in small spaces that stay damp and survive for many weeks.


After visiting a site, first clean your waders and then treat them using either the physical or chemical methods listed below. We recommend the following precautions:

  • Change your wading gear for use in different bodies of water, if possible.

  • Clean all gear before leaving a site, scrubbing with a stuff-bristled scrub brush and rinsing with clean, potable water. Clean your gear with a high-pressure hose as soon as possible. This is often the simplest and most effective for prevention.

  • Inspect gear before it is reused. Traces of sand, mud, gravel, and plant fragments on the gear are signs that gear has not been properly cleaned.

  • Select ONE recommended treatment method in addition to scrubbing and rinsing if NZM is suspected to be present.

  • PHYSICAL treatments are inexpensive, environmentally sound, and possibly, not as destructive to gear. Time/space requirements or lack of feasibility may make physical treatments impractical for specific types of gear.

  • Freeze gear for 6 hours. This is the best known treatment to kill all snails. Freezer temperatures should be 26 degrees Fahrenheit (-3 degrees Celsius); OR

  • Soak in hot water for 10 minutes. Hot water should be 120-140 degrees Fahrenheit (46 degrees Celsius). This method is not recommended for Gortex; OR

  • Dry gear before reuse. A drying time of at least 48 hours is recommended to remove all dampness. Gear should be completely dry for an additional 24 hours to limit snails. Check boots to ensure that they are completely dry before reuse.

  • CHEMICAL treatments can help, but the presence of mud on gear will limit its effectiveness. Avoid contamination of waterways and wetlands by (1) always scrubbing your gear before using these methods, and (2) rinse with potable water away from the water body. DO NOT rinse your chemically treated water in the water body.

  • Soak wading gear in 2% Virkon Aquatic Cleaner for 20 minutes to kill all snails; OR

  • Soak gear in Formula 409 Cleaner De-greaser at full strength for 10 minutes. This is known to kill snails. However, these compounds may result in the rubber's surface cracking and loss of water repellency on wading gear.

  • Some treatments are not effective against NZM. Bleach and salt solutions have not been found to be effective after treatment.



Planning your water activities can help limit the spread of NZM. When moving between infested and non-infested waterways, always start at areas with no known infestation and progress to more infested sites. Here are some additional recommendations:

  • Drain all of the water from your boat (including the bilge, live well, motor), trailer, tackle and gear before leaving the area.

  • Clean boots by removing debris, scrubbing trailers and motor blades, and have contact with a scrub brush.

  • Spray with hot water that should be 120-140 degrees Fahrenheit (46 degrees Celsius). Steam cleaning is highly recommended.

  • Dry thoroughly

  • Never transport live fish or any other aquatic plant or animal from one water body to another.

Working together we can help to protect against the spread of this invasive creature.

Picture showing the NZM's small size

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