Inspections protect Colorado waters from invasive mussels entering on boats

With the summer boating season nearing its end, Colorado Parks and Wildlife reported Wednesday it had intercepted 47 boats contaminated by invasive zebra and quagga mussels in 2018— the agency’s 10th year of protecting Colorado’s waters with its Aquatic Nuisance Species inspection and decontamination program.

ANS inspectors stopped everything from boats teeming with mussels to a boat with a single zebra mussel, the size of a pebble, at Lathrop State Park. Like most of the other contaminated vessels, the boat stopped at Lathrop had just come from Lake Powell.

“Of the 47 boats that were intercepted, 36 came from Lake Powell,” said CPW’s Elizabeth Brown, Invasive Species Coordinator. “This is a far greater number then we have ever seen in the past. Our previous statewide annual record was 26.”

Colorado has intercepted more than 145 boats infested with adult mussels since the ANS Program began in 2008. Initially, most infected boats came from the Great Lakes, Mississippi River and other Eastern states. In recent years, more infected boats are coming from the Lower Colorado River, which includes Lake Powell, a Colorado River reservoir that straddles the Utah-Arizona state line. It’s a popular destination for many Colorado boaters and it is one of several western U.S. waters severely infected with invasive quagga mussels.

CPW considers invasive mussels to be a significant threat to Colorado’s water users, which includes recreation users as well as drinking water, hydropower and agricultural users. To fight the threat, CPW worked collaboratively with partners and Colorado lawmakers to pass the Mussel-Free Colorado Act last spring.

On April 24, Gov. John Hickenlooper signed the act into law, providing $2.4 million for the ANS program for 2019 and beyond. CPW Director Bob Broscheid declared its passage “a huge win for protecting Colorado’s water.”

Brown said CPW’s ANS inspectors have logged 435,409 inspections requiring 13,691 decontaminations in 2018, to date.

“We remain one of only a few states in the West that are free of adult zebra and quagga mussels,” Brown said. “Our success is a credit to our diligent ANS inspectors and to Colorado’s boating public. Our program would not work without their cooperation and commitment to protecting Colorado’s waters from invasive species.”

CPW has made ANS inspections a priority because of the extreme threat posed by zebra and quagga mussels to reservoir infrastructure and drinking water systems.

The mussels are prolific, infesting waters by the billions, quickly clogging water-delivery systems for irrigation and power generation. Utility companies with mussel infestations spend millions each year to keep their systems functioning after an infestation. Those costs can be passed on to the consumer in the form of higher electricity and water use rates.

Water quality declines with mussel infestations and they degrade beaches, docks, buoys and boats. ANS inspectors have intercepted boats encrusted with billions of mussels in various stages of their life cycle.

Brown urged boaters to remain vigilant even as the most popular boating season ends and many reservoirs transition to an honor system for ANS inspections.

“It is critical our boating public continues to inspect their watercrafts for mussels and other invasive aquatic nuisance species,” Brown said. “Eradicating an adult mussel infestation in an open water body is nearly impossible. We have created an effective prevention program to stop mussel introduction with the ‘clean, drain and dry’ program.

“This winter, please help us keep Colorado free of the invasive mussels and other ANS.”

For more information about CPW’s ANS Program and the Mussel-Free Colorado Act, visit