Sign In
Top Invasive Concerns: New Zealand Mudsnails
Top Invasive Concerns: New Zealand Mudsnails

​​​​​​What are ​​​​​​​​​New Zealand Mudsnails?

​​​​​​​​New Zealand mudsnails are an invasive freshwater snail. They are voracious eaters that reproduce rapidly, eating much of the available food. This negatively a​ffects aquatic insect larvae, native snails, as well as fish populations. Humans inadvertently move NZMS from one stream to another when they cling to waders, boots, boats, dogs and other gear. They can reproduce sexually or asexually, so just one snail can start an entirely new population! They are also able to pass through a fish's digestive system unharmed, leaving the fish malnourished.

Where have ​​​​​​​​​​New Zealand Mudsnail been found?​

  • New Zealand Mudsnail was most recently discovered in Chatfield Reservoir in 2015.  
  • 2013 - Fountain Creek in Colorado Springs.  
  • 2012 - Spinney Mountain State Park (similar to the previous year's detection in neighboring Eleven Mile Reservoir State Park)
  • 2011 - East Delaney Buttes State Wildlife Area and College Lake, CSU, Fort Collins.  
  • 2010 - South Delaney Buttes State Wildlife Area, and two sites within the City of Boulder along Dry Creek.  
  • The invasive snail was first found in Colorado in 2004 in Boulder Creek, the South Platte River below Eleven Mile dam and the Green River in Dinosaur National Monument.  
    • There were no detections 2005-2009. ​


Help prevent the spread of New Zealand Mudsnails​!

Report​ any sightings to CPW!

Keep all gear free of mud, plants, and organic debris in between each and every use. Unknowingly moving a species from one body of water to another, even within different stretches of the same river, can start a domino effect of invasion, causing irreversible ecological damage. It is especially important to keep waders clean.

People recreating in Colorado's waters should scrub the bottom of boots or waders with a brush and remove all mud, plants, and organic materials in
between each and every use.  They should then perform ONE of the following options before going into the next body of water:


Submerge waders and gear in a large tub filled with a mixture of 6 ounces per gallon quaternary ammonia-based institutional cleaner (such as Super HDQ Neutral) and water for at least 10 minutes, scrubbing debris from the gear, and visually inspecting the gear for snails before rinsing. Follow all precautionary label instructions! Rinse water must be from a New Zealand ​mudsnail-free source (to avoid re-infection), and the chemical bath must
be properly disposed of, away from the water body.


Spray or soak waders and gear with 140º Fahrenheit water for at least 10 minutes.


Dry your waders and equipment completely for a minimum of 10 days in between each use (remember that mudsnails can survive several days out of water).​


Place waders and boots in a freezer overnight between use.

Thank you for protecting Colorado’s waters from the harmful impacts of invasive species!