Colorado Parks and Wildlife confirmed the first detection of invasive New Zealand mudsnails in Carter Lake, a popular Larimer County reservoir southwest of Loveland, prompting officials to expand inspection checkpoints. Because these tiny, self-cloning mollusks can quickly overrun ecosystems and are nearly impossible to eradicate once established, the agency is urging visitors to thoroughly clean, drain, and dry all recreational gear.
A Quarter-Inch Invader That Clones Itself
Measuring about the size of a nail clipping and barely one quarter of an inch, the brown New Zealand mudsnail is easily missed in lake sediment and can be carried away on wet gear without a person ever realizing it was there. Yet its biology presents an extraordinary management challenge. In the western United States, every single specimen is female, and each one is born carrying embryos. They reproduce asexually, meaning a solitary snail can create an entire population without needing a mate.
That self-sufficient reproductive engine allows populations to reach densities of hundreds of thousands of snails per square meter, which can also clog reservoir inlets, outlets, and recreational structures. In Carter Lake, this marks the first time the species has been officially documented, adding a new location to a statewide list where the snails have been confirmed in 41 other bodies of water.
These mud snails are very big eaters, and they just kind of go through all of the different nutrients that are in an ecosystem and don’t really provide any benefits back to anything else in there.
Ecological Disruption Without Natural Predators
Beyond their sheer numbers, the mollusks consume vital resources required by native aquatic species, competing with mayflies and other invertebrates for food. Native fish do not benefit from consuming the snails, and birds that ingest them may pass them through their digestion “unscathed,” as their shells allow them to survive and take energy from the ecosystem without becoming a meaningful food source.
While state wildlife officials emphasize that the tiny invaders pose no risk to human health, their presence severely disrupts aquatic environments. Once established across a large waterway, eliminating them demands drastic intervention.
It would take Herculean efforts to remove them from a waterway, like draining the water, years’ worth of treatment, and all of that.
Van Hoose
Containment Over Eradication at Carter Lake
Because officials are not promising to remove them and total eradication remains practically impossible for a large waterway, the focus has shifted entirely toward containment. Boat inspection checkpoints at Carter Lake have been expanded to include mudsnail screening along with checks for zebra mussels and other aquatic invasive species, inspecting watercraft when they arrive and when they leave.
However, physical inspections alone cannot stop every transfer. Mudsnails possess a formidable resilience, surviving outside the water for days and remaining on damp equipment for weeks. That means a single trip with wet gear can create an opportunity for the species to spread, so officials emphasize that it is best just to contain the spread and prevent it from moving further.
The Cleanup That Falls on Every Visitor
With state agencies relying heavily on the people who use Colorado’s lakes and rivers, the burden of containment falls squarely on public action through CPW’s Pain in the ANS
outreach campaign. Visitors to Carter Lake and other affected areas are encouraged to thoroughly clean equipment before moving between lakes and rivers, including boats, kayaks, paddleboards, fishing equipment, inner tubes, and anything else that comes into contact with the water.
Visitors must meticulously follow a strict clean, drain, and dry protocol because even a small amount of moisture can transport the snails. Other individuals are also fully invested in protecting ecosystems from invasive species, such as Ian, whose wife Kerry and sons Jake, George, and Ben help rear critically endangered invertebrates like scarlet malachite beetles, ladybird spiders, tadpole shrimp, and snails. As Ben, 27, explained about walking out into a freezing cold lake in the middle of January: You’ve got to have a certain mindset… But knowing that you’re helping is more than enough to make it all worth it.
