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Invasive New Zealand mudsnails found in South Boulder Creek

A single mudsnail can produce a colony of 40 million snails in just one year.
Credit: KUSA
Mudsnails next to a coin. Adult mudsnails are about the size of a grain of rice.

BOULDER, Colorado — New Zealand mudsnails – an invasive aquatic species that can disrupt aquatic ecosystems, harm fish populations and displace native insects - have been found in South Boulder Creek in Boulder.

With the discovery of the mudsnails in a creek area near the East Boulder Community Center, the city is asking for the community to help prevent their spread into additional waterways.

The best way to do that is to stay out of the creek since the invasive snail is so small.

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.

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Due to their tiny size, they can easily 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.

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Officials have temporarily closed South Boulder Creek access south of South Boulder Road to Marshall Road to help stem further human-caused spread of mud snails along the creek. Educational advisory signs along the creek area also being installed which encourage visitors to stay out of the creek in areas that aren’t included in the temporary closure.

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 to the postpone implementation of the Gebhard Integrated Site Project – a habitat protection and recreational access project planned for an area near where the mudsnails were discovered.

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