AURORA — Attention Western Slope pond owners: Colorado Parks and Wildlife is on the hunt for hungry, fast-reproducing, invasive mussels — and that they might be hiding in your pond.
State and federal agencies, plus water districts, are fighting to track and contain zebra mussels in and around the Colorado River in Colorado. Officials are hiring new staff, doing sampling blitzes and catching mussel-bearing motorized boats at the state’s borders, but the populations of zebra mussels keep popping up. This year, the state is taking its search beyond public waters and irrigation systems.
Colorado Parks and Wildlife staff hope to survey as many as possible of the thousand-plus ponds on private property in the Grand Junction area during summer 2026.
“As this has gotten bigger and bigger and bigger out there in the Western Slope, it’s really, really important to us that we do everything we can to contain or stop this population from getting any further than it already has,” Robert Walters, the agency’s invasive species program manager, told a small gathering of water watchers Wednesday.
It was one of the first discussions at this year’s winter conference held by the Colorado Water Congress, a water professional association that works to shape Colorado law and policy to protect water resources.
Zebra mussels have already spread across the eastern U.S., but Western states have been working for years to prevent the spread.
Adult zebra mussels, about the size of a thumbnail with a zebra-striped shell, reproduce quickly and suck up nutrients, out-eating other native aquatic species. Their razor-sharp shells create walking hazards for beachgoers.
The mussels attach to surfaces with extraordinary strength and then pile on top of each other. In general, mussels’ sticky superpower has inspired surgical glue and underwater industrial adhesives.
But they can clog up pipes, valves and parts of dams, costing millions of dollars to remove.
Tracking the spread
The first adult zebra mussel in Colorado showed up in Highline Reservoir near Grand Junction in 2022.
In July 2024, Colorado Parks and Wildlife staff started detecting microscopic zebra mussels, called veligers, in the Government Highline Canal and the Colorado River. In 2025, they found zebra mussels in a small irrigation pond on the Mesa County Fairgrounds and more than 80 miles upstream in the New Castle area and in a privately owned lake in western Eagle County.
(Zebra mussels are free-floating creatures, which means they go with the flow. The only way they move upstream is if something carries them, like animals or a boat.)
In October, the state enlisted about 75 people from several agencies to do a last sampling effort before winter, dubbed the Colorado River aquatic nuisance species “blitz.” The teams did physical surveys of the Colorado River from Granby Dam out to Westwater, Utah, and they looked at portions of two main tributaries, the Eagle and Roaring Fork rivers.
They found more adult zebra mussels in the Colorado River in Glenwood Canyon and west of the town of Rifle, Walters said.
“I wish I could tell you that I believed that the story of zebra mussels in western Colorado was concluded, and that we knew everything about this population, but that would not be true,” he told the gathering.
The containment toolkit
Since 2022, the state has tried a variety of tools to contain the mussels, but historically, once an adult population is established it is very difficult to remove, experts say.
Colorado Parks and Wildlife treated Highline Lake and the private lake in Eagle County. The agency has found adult mussels in Highline Lake each year, and it will be years before they know if the private lake treatment was effective.
CPW expanded its monitoring efforts geographically and increased the size of the aquatic nuisance species laboratory in Denver to process samples faster.
They added staff to help with detection and ramped up efforts to check and disinfect watercraft at state lines and at reservoirs. In 2025, CPW did more than 1,800 decontaminations at Highline Lake State Park and intercepted 60 boats bearing mussels at four ports of entry into Colorado, Walters said.
Other agencies have gotten involved. The Bureau of Reclamation is keeping an eye on Western Slope systems that provide drinking and irrigation water or hydropower energy, like the Redlands Water and Power system, Shoshone Power Plant, the Colorado-Big Thompson Project, Blue Mesa Reservoir and the Uncompahgre project.
Water districts in the Grand Valley area around Grand Junction have also done proactive treatments on irrigation canals, Walters said.
The Grand Valley is a highly agricultural area where a vast network of canals and ditches are moving Colorado River water into homeowners association ponds, golf courses, parks and ponds in people’s backyards, Walters said.
“Every one of them that is receiving Colorado River water has the potential to be harboring a population of invasive mussels,” he said.
Hence the plan to reach out to private property owners to inspect their ponds. This year, CPW will also install its first decontamination dip tank, an emerging technology that allows for more efficient decontaminations. The tank will help prevent the spread of mussels from boats that are leaving Highline Lake, Walters said.
The agency is going beyond its prior focus on motorized vehicles to do more to educate kayakers, rafters, canoers and other paddlers. They’re coming up with catchy communication campaigns — “Be a pain in the ANS!” “Oh, shell no!” — and speaking face to face with thousands of people.
The main message: Clean, drain and dry your gear. And if you think you’ve found a zebra mussel or you’re not sure, contact the state’s aquatic nuisance species program.
The good news is that the vast majority of Colorado’s rivers and reservoirs are free of invasive mussels, Walters said.
“We still have an incredible fight ahead of us to make sure that these waters remain unimpacted by these aquatic nuisance species,” he added.