Colorado lakes, reservoirs are free of invasive mussels

DENVER – More boats requiring decontamination because of infestations of destructive mussels entered Colorado in 2020 compared to previous years; but the statewide inspection program coordinated by Colorado Parks and Wildlife again succeeded in keeping invasive mussels out of the state’s lakes and reservoirs.

Thanks to CPW’s comprehensive Aquatic Nuisance Species (ANS) prevention program, all waters in the state are now officially free of evidence of mussels. In 2017, veligers, the microscopic larval stage of quagga mussels, found at Green Mountain Reservoir showed that mussels might exist there. But three years of subsequent water testing were negative for mussel species.

“Colorado Parks and Wildlife continues to meet the challenge of protecting the state’s waters and infrastructure from aquatic nuisance species,” said Robert Walters, CPW’s ANS program manager. “But as boating season approaches we continue to ask for help from boat owners in maintaining our mussel-free status.”

Mussels are destructive to aquatic habitat, can seriously damage reservoir infrastructure and cause problems on boats.

As usual, Colorado’s ANS inspectors were plenty busy during 2020. Staff conducted a total of 647,325 inspections and decontaminated 24,771 boats suspected of carrying mussels, other aquatic invasive species or standing water. That was a huge increase of 34 percent in inspections from 2019 when 481,253 boats were inspected and 22,947 were decontaminated. Most concerning is the continued increase in the number of boats fouled with mussels. In 2019, 86 boats were found to be fouled with invasive mussels and in 2020 that number jumped to 100. Only 16 boats with mussels were found in 2017.

Contaminated boats come into Colorado from neighboring states, especially Utah and Arizona because of our proximity to Lake Powell which has been mussel-infested for years. Other neighboring states with mussel infestations include Kansas, Nebraska, Oklahoma, Texas and South Dakota. Most Midwestern and East Coast states also have infested waters.

Some of the increase in inspections can be attributed to the large influx of outdoor recreation Colorado has experienced since the start of the pandemic. Colorado Parks and Wildlife understands that outdoor recreation is important to everyone’s physical and mental health and the state made a commitment to keep state parks open during the pandemic.

Since CPW’s ANS inspection program started in 2008, 5.6 million boats have been inspected and 144,000 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. CPW also works proactively looking for aquatic nuisance species by sampling waters throughout the state. In 2020, crews sampled 175 standing waters and four flowing waters. The National Park Service provided CPW with 14 water samples.

CPW has also been instrumental in establishing the Water Inspection and Decontamination (WID) protocols which are now used by states throughout the West. Agency staff also are active with the Western Regional Panel on Aquatic Nuisance Species Watercraft Inspection and Decontamination Committee.

Walters said that CPW will always remain vigilant in the fight against mussels.

“Mussels aren’t going away. However, by continuing our preventative watercraft inspection program we can keep Colorado’s waters free of invasive mussels.”

Boat owners are reminded to “clean, drain and dry” boats after every use. Boaters should also inspect their trailers and look in hard-to-reach spots on boats and engines for evidence of mussels. Anyone who has used a boat in waters outside of Colorado should tell boat inspectors. Boat owners can also call any state park or wildlife office if they have questions or concerns.

For more information about aquatic nuisance species and CPW’s program, visit: or read the Boater’s Guide to ANS Inspections.