New Zealand Mudsnails

The New Zealand mudsnail was first discovered locally in Boulder Creek in 2004. It has also been found below Elevenmile Reservoir Dam. The following information has been taken from the Colorado Division of Wildlife website:

The New Zealand mudsnail, a mollusk, is native only to New Zealand. It was first discovered in North America in the 1980s in the Snake, Madison and Idaho rivers, but no one knows how it arrived there. This small, invasive creature quickly spread to Yellowstone National Park. From there it spread to many other bodies of water, streams and rivers across the west.

The mudsnail invades new habitat when it becomes attached to fishing gear, boats, trailers or even fish and bait, and then comes off in the next stream or river where these things are used or discarded. Mudsnails consume aquatic vegetation, upsetting the balance of the aquatic environment.

How to Identify the New Zealand Mudsnail

- The mudsnail is an average of 1/8 of an inch long (but can be as small as a grain of sand) and has a gray-brown cone shaped shell that consists of five whirls.
- They can live in all kinds of waters - from silted river bottoms to clear mountain streams.
- The mudsnail can tolerate temperatures from 32º F to 77º F, but prefer temperatures of about 66º F.
- They reproduce asexually; it only takes ONE to start a whole new population!
- Mudsnails can survive out of water for several days, so it's easy to see how they can move about and survive on recreational gear.

Help Stop the New Zealand Mudsnail

Densities of over 500,000 per square yard have been found in Yellowstone National Park! Because of this mollusk's lack of predators (it's controlled naturally by a parasite in New Zealand), it often has a great advantage over native species and in many cases can overwhelm native plants and animals. Biological invasions can change the way we use and enjoy our natural resources and these changes are often not for the better. Trout and other recreational fisheries could be reduced forever. Help control the spread:

• The only sure way to prevent spread by anglers is to make sure waders, boots, tackle, etc. are thououghly washed and soaked in a solution of 50% water and 50% Commercial Solutions Formula 409® Cleaner Degreaser Disinfectant for 5 to 10 minutes before the boots, waders, equipment are used in another stream. Regular Formula 409 has not been shown to kill the snails. The Commercial Solutions Formula 409® Cleaner Degreaser Disinfectant may be found at local Home Depot stores.
• Freezing overnight will also kill the snails.
• Let equipment dry for several days between uses. Remember that mudsnails can survive several days out of water.
• Dry heat will kill them. Spray them with soapy water and leave them in the hot sun for several hours. (The soap breaks down the mucous that helps them hold on to moisture.)

The West Denver TU chapter has a good page with more information on the NZMS problem, the danger they pose and how to disinfect your gear.

DOW news release on first discovering mudsnails in Boulder Creek

Read about the DOW's lifting of the fishing closure in Boulder Creek

New Zealand mudsnail fact sheet

Informational poster

Denver Post's Charlie Meyers writes about the "Invasion of Wildlife Snatchers"

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