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Invasive New Zealand Mudsnails Discovered in South Boulder Creek

Recent city wildlife monitoring in South Boulder Creek has discovered New Zealand mudsnails – an invasive aquatic species that can disrupt aquatic ecosystems, harm fish populations and displace native insects.

With the discovery of mudsnails in a creek area near the East Boulder Community Center, the City of Boulder requests community assistance in preventing their spread to additional stretches of the creek and other water bodies. It also advises open space visitors the best way to prevent the spread of this invasive snail is to stay out of the creek.

Adult mudsnails are about the size of a grain of rice and can rapidly reproduce through cloning – a single mudsnail can produce a colony of 40 million snails in just one year. Because they are so small, they can hitch a ride from one water body to another on everything from a dog’s paw to fishing equipment, including boots and waders. Mudsnails can also easily adapt to a wide range of aquatic ecosystems and once established in a creek, there are no practical means of removing them all.

The city reminds residents – particularly anglers and dog guardians – to practice these responsible recreation practices:

  • Visitors should not access streams or creek areas where mudsnails have been found. If individuals fish in an affected area, they should use a wire brush to remove mud and vegetation from their boots and gear immediately after stepping back onto dry ground.
  • If dogs enter South Boulder Creek, guardians should carefully brush their paws and bellies on dry land.
  • Visitors, and especially anglers, should take precautionary steps detailed by Colorado Parks and Wildlife when they are back home or before they go to another body of water. Those measures include freezing boots and gear overnight, soaking equipment in hot water, submerging waders and other equipment in solution specified by CPW, or drying boots and gear – preferably in direct sunlight – for at least 48 hours.
  • Community members should not flush water used to clean boots or rinse equipment down storm drains.

OSMP has temporarily closed South Boulder Creek access south of South Boulder Road to Marshall Road to help stem further human-caused spread of mudsnails along the creek. OSMP also will install educational advisory signs along the creek encouraging visitors to stay out of the creek in areas that aren’t included in the temporary closure.

During this temporary closure and community-outreach period, OSMP will assess its current management of South Boulder Creek – one of the city’s most diverse creek areas and home to federally protected wildlife and plant species – and may implement additional measures and creek access restrictions. The city currently has year-round New Zealand mudsnail closures in portions of Dry Creek and Boulder Creek.

The discovery of New Zealand mudsnails in South Boulder Creek also has led OSMP to postpone implementation of its Gebhard Integrated Site Project – a habitat protection and recreational access project planned for an area near where OSMP discovered mudsnails. The department anticipates sharing updates about this project with community members in early 2021.

Media Contacts: 
Phillip Yates, Media Relations, 303-349-2438

Published Oct. 30, 2020