Sign In
Top Invasive Concerns: New Zealand Mudsnails
Top Invasive Concerns: New Zealand Mudsnails
New Zealand mudsnail size compared to a dime

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

​​​​​​​​New Zealand mudsnails are an invasive freshwater snail. They are New Zealand mudsnailsvoracious eaters that reproduce rapidly, eating much of the available food. This negatively ​effects 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.

​New Zealand Mudsnail Positive Waters in Colorado​

​Water Body

​Year First Detected

​South Platte River (just below Eleven Mile dam in Park County)​2004
​Boulder Creek, City of Boulder
​Green River within Dinosaur National Monument
​Dry Creek, City of Boulder
(2 distinct populations)
​South Delaney Buttes State Wildlife Area (Jackson County)
​East Delaney Buttes State Wildlife Area (Jackson County)
​Eleven Mile Reservoir State Park & Charlie Meyer SWA
​College Lake, CSU, Fort Collins
​Spinney Mountain State Park
​Fountain Creek
​Chatfield Reservoir
​Gunnison River (West of Delta)
​Fourmile Canyon Creek (Boulder County)
​Monument Lake
​South Platte River (Near Deckers)
​Uncompahgre River (Town of Montrose)
​Jimmy Camp Creek
​Monument Reservoir
​Trinidad Lake
​Lake Capote
​Chatfield Pond #1
​Elmer’s 2 Mile Park (Boulder County)
South Platte River (City of Denver)
​Trout Creek
​South Boulder Creek
Goose Creek​
​Wonderland Creek
​Badger Creek
​Arkansas River
​Sutherland Ditch
​Colorado River (Near Parachute)
​Highline Government Canal
​St. Vrain Creek

New Zealand Mudsnail Distribution for 2020 Map image
*Click on map for larger version

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:


Cleaning Waders - Bucket, spray and wadersSubmerge 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!