Mud Snail Closures on Boulder Creek and Dry Creek

Dry Creek and Boulder Creek downstream of Valmont Road are two of only three locations in Colorado where the non-native, invasive New Zealand mud snail has been found.

Mud snails can be spread by boots, waders, a dog's pads, and most anything they come in contact with. The snails are very tiny and thus can easily go undetected as they hitch a ride to a new area. Highly resilient, the snails can survive several days out of water and can withstand a wide range of temperatures.

Because they reproduce by cloning, it only takes one New Zealand mud snail to start a new colony!

Please stay out of the closure areas to avoid the spread of mud snails, and subsequent threats to our aquatic ecosystems.

Dry Creek Closure, effective Sept. 21, 2010

 Map of Dry Creek Closure area 446.53 Kb

Access to the Dry Creek Trail and Trailhead and access to the creek, south of Baseline Road is prohibited.

Boulder Creek Closure

Map - OVERVIEW of entire Boulder Creek closure area 2.33 Mb
Close up, Map - Boulder Creek Western closure area 2.39 Mb

Close up, Map - Boulder Creek Eastern closure area 2.33 Mb

Due to the highly invasive New Zealand Mud Snail and the potential for detrimental impact on Boulder Creek, the city of Boulder has enacted an emergency closure of all access to a stretch of the creek and several Open Space & Mountain Parks properties adjacent to the creek. This closure remains in effect until management actions are taken (such as fencing) or until information suggests that the closures are no longer necessary.

New Zealand mud snails (Potamopyrgus antipodarum), which are native to the Southern Hemisphere, were found in Boulder Creek in November 2004. The discovery in Colorado of the miniscule snail that has invaded rivers and streams across the West raises concerns that the fast-spreading invertebrate could push out native species and compromise the long-term health of the region's aquatic ecosystems.

U.S. biologists first discovered the snails in Idaho's Snake River some 20 years ago. Aside from Colorado, they have spread into Montana, California, Arizona, Oregon, Utah and Wyoming, including Yellowstone National Park.

Photo - a host of fully grown New Zealand Mud Snails with a key for scale.

At only 2-to-5 millimeters in length, the mud snails are difficult to contain once they have invaded an aquatic ecosystem, and are so small they cannot be skimmed from waters. The snails can cling to birds and other wildlife, and are thought to be spread by human and domestic pet activities, including hiking and fishing. They can be spread by boots, waders, and “most anything they come in contact with”, said Heather Swanson, OSMP Wildlife Ecologist. Highly resilient, the snails can survive several days out of water and can withstand a wide range of temperatures. The tiny invertebrates can even pass unscathed through the digestive tracts of fish.

Officials stressed that public awareness is crucial to stopping the spread of exotic species in Colorado's streams, rivers and lakes precisely because of the difficulty of removing them once they have arrived. The Board of Directors of the Boulder Flycasters has endorsed the actions of the city in the closure of Boulder Creek.

Last Updated on Friday, 27 July 2012 08:57