Colorado Parks and Wildlife (CPW) Aquatic Nuisance Species (ANS) staff continue to see success in fighting the introduction and spread of invasive species in Colorado's water bodies through inspections, decontaminations and education in 2025.
"As the challenge of protecting the state's waters and infrastructure from aquatic nuisance species continues to grow, CPW continues to lead the charge against these destructive species," said Robert Walters, CPW's Invasive Species Program Manager. "By continuing our preventative watercraft inspection program, Colorado can continue to not only protect our waters but aid in protecting waters across the West."
At lakes across the state, Colorado's ANS inspectors were busy during the 2025 boating season. From Jan. 1 to Dec. 31, ANS staff conducted a total of 438,272 watercraft inspections and decontaminated 30,039 high-risk boats that pose a threat to Colorado's waters.
Additionally, ANS staff intercepted 136 watercraft that were fouled by invasive mussels. Any motorized boat found with mussels or any other potentially invasive specie(s) was required to go through a mandatory decontamination before launching.
The following locations recorded the highest numbers of inspections for the 2025 boating season.
- Pueblo Reservoir - inspected 63,357 watercraft and found 10 mussel-fouled watercraft
- Chatfield Reservoir - inspected 59,571 watercraft and found 1 mussel-fouled watercraft
- Horsetooth Reservoir- inspected 38,768 watercraft and found 5 mussel-fouled watercraft
- Boyd Lake - inspected 29,317 watercraft and found 10 mussel-fouled watercraft
- Cherry Creek Reservoir - inspected 22,194 watercraft and found 1 mussel-fouled watercraft
It's important to note that because Highline Lake is an infested body of water, all motorized watercraft leaving the lake must go through mandatory decontaminations. Here, ANS inspectors inspected 3,697 watercraft and found 16 mussel-fouled watercraft prior to launch.
Prevention beyond the boat ramp
CPW has continued to see success from the mandatory roadside Aquatic Nuisance Species Check stations implemented since the passage of House Bill 21-1226, which was signed into law in 2021. In addition to the Loma and Trinidad ports of entry (P.O.E), both operating seven days a week, CPW has also added new checkpoints at the Fort Morgan P.O.E and Limon P.O.E.
During 2025, CPW conducted the following inspections, decontaminations and interceptions of vessels carrying invasive species:
- Loma P.O.E - 3,647 inspections, 1,044 decontaminations and 57 interceptions.
- Trinidad P.O.E - 357 inspections, 52 decontaminations and 3 interceptions.
- Fort Morgan P.O.E - 1,107 inspections, 163 decontaminations and 0 interceptions.
- Limon P.O.E. - 186 inspections, 20 decontaminations and 0 interceptions.
"Inspecting the highest risk watercraft at ports of entry continues to serve as a first line of defense and helps ensure Colorado's lakes and reservoirs remain free of highly destructive aquatic nuisance species. With the help of our partners at Colorado State Patrol Port of Entry and the Colorado Department of Transportation, we look forward to continuing the fight against invasive species," said Walters.
Zebra Mussels on Colorado's Western Slope
Increased sampling efforts on the Colorado River and nearby bodies of water continued in 2025. Beginning in April and lasting through October, CPW ANS crews conducted weekly shoreline and water sampling along sections of the Colorado River between Granby and the Colorado-Utah border as part of increased sampling efforts after the discovery of zebra mussel veligers (larvae) in the river in July 2024.
Over the course of several months, ANS sampling crews sampled 227 standing and 41 flowing waters across the state. These sampling efforts produced 2,207 plankton samples, all of which were processed by CPW's own ANS Laboratory located in Denver. Many of these samples were also evaluated for the presence of zebra mussel eDNA (environmental DNA) at CPW's Aquatic Animal Health Laboratory in Brush.
On Sept. 15, 2025, CPW announced the discovery of adult zebra mussels in the Colorado River and a nearby lake in Grand Junction. This was the first time adult zebra mussels had been found in the Colorado River and this discovery is a direct result of increased sampling efforts by CPW.
On Oct. 29, 2025, roughly 75 people from multiple partner agencies and groups joined CPW for a one-day sampling effort on the Colorado River. Through this large-scale effort, CPW confirmed a single adult zebra mussel in the Colorado River near Rifle. During subsequent surveys, staff discovered additional adult zebra mussels within Glenwood Canyon.
With these new findings, the Colorado River is now considered infested from the confluence of the Eagle River down to the Colorado-Utah border.
"While the findings were no doubt disappointing, they are a direct result of the increased capacity within the ANS Program. This includes the hiring of new full-time employees, physical expansion of the ANS laboratory in Denver, and the use of cutting-edge technologies such as environmental DNA detection techniques," said Walters.
In 2026, ANS staff will continue increased sampling and outreach in the Grand Valley and areas with high recreation use, including Two Rivers Park in Glenwood Springs. In addition to the Colorado River, CPW plans to work with its federal and local partners to sample as many Grand Valley ponds, lakes and other bodies of water that receive water from the Colorado River as possible.
If you own a pond or lake that utilizes water from the Colorado River or Grand Junction area canal systems, CPW would like to sample your body of water. You can request sampling of your body of water by CPW staff at Invasive.Species@state.co.us.
At Highline Lake, an installation of a decontamination dip tank, a first for Colorado, is planned to open for 2026. The installation of the dip tank will support the containment program, while reducing wait times for boats leaving the lake.
Take Action: Be a Pain in the ANS
Along with inspections and increased sampling, education and outreach continue to be a top priority for CPW's ANS staff.
In 2025, staff participated at multiple events, including GoPro Mountain Games in Vail and Denver Boat Show. In addition, ANS staff made 7,036 face-to-face educational contacts, of which 5,103 were Colorado River users.
Simple actions like cleaning, draining and drying your motorized and hand-launched vessels — including paddleboards and kayaks — and angling gear after you leave the water can make a big difference to protect Colorado's waters.
Learn more about how you can prevent the spread of aquatic nuisance species and tips to properly clean, drain and dry your boating and fishing gear by visiting our website. Tips for anglers and a map of CPW's new gear and watercraft cleaning stations are available here.
MEDIA PACKAGE: Aquatic Nuisance Species in Colorado
About Colorado's ANS Program
Aquatic Nuisance Species (ANS) are aquatic plants and animals that invade lakes, reservoirs, rivers and streams. ANS can wreak havoc on ecosystems, outdoor recreation, hydroelectric power equipment and the economy.
In May 2008, the State Aquatic Nuisance Species Act was signed into law, which allocated funding to establish an Aquatic Nuisance Species (ANS) program in Colorado aimed at preventing the spread of invasive species. In 2018, the Colorado General Assembly passed the Mussel Free Colorado Act (House Bill 18-1008), which created a stable funding source for this initiative. The new legislation also increased fines for violations and allowed Colorado Parks and Wildlife to recover costs for the decontamination of quarantined and impounded vessels.
Since CPW's ANS inspection program started in 2008, over 7.9 million boats have been inspected and 295,000 boats have been decontaminated. The agency is aided in the program by Colorado counties, municipalities, water districts, federal agencies and private companies that also conduct inspections.
In 2021, Colorado Legislature passed House Bill 21-1226, which authorized Colorado Parks and Wildlife to implement a pilot roadside watercraft inspection and decontamination program.
CPW has also been instrumental in establishing the Water Inspection and Decontamination (WID) protocols which are now used by states throughout the nation. Agency staff also are active with the Western Regional Panel on Aquatic Nuisance Species Watercraft Inspection and Decontamination Committee.