Invasive mussels haven’t been found in Colorado’s lakes and reservoirs

Wildlife officials are battling to keep it that way


Zebra and quagga mussels do not yet exist in Colorado’s lakes and reservoirs, and Colorado Parks and Wildlife leaders are working hard to keep it that way.

They’re stepping up enforcement efforts through a statewide decontamination program. Each year, the department runs the Aquatic Nuisance Species Program, where inspectors at 73 locations decontaminate boats before they enter and exit Colorado’s waterways. Since the program’s inception in 2008, almost 500,000 boats have been inspected annually. The inspections help detect species like zebra and quagga mussels that attach to boats. If knocked off, the muscles can drop into, and infect, Colorado waters.

“Each year, the number of boats we are intercepting here in Colorado is increasing significantly,” said Robert Walters, invasive species program manager. “In 2017, we intercepted 26 boats coming into the state that had mussels on them. In 2021 alone, we intercepted 181.”

Colorado is not free of all invasive aquatic nuisance species. Some bodies of water in Colorado contain Eurasian watermilfoil, for example, which grows quickly and blocks sunlight, and can kill off native aquatic plants that fish and other underwater species rely on for food and shelter.

Colorado Parks and Wildlife leaders remain concerned about the possibility of zebra and quagga mussels possibly popping up across the state. The department is conducting an awareness campaign this month ahead of Memorial Day, which is when the boating season generally kicks off in Colorado.

A single mussel can produce up to 1 million babies in a single year.

The aquatic nuisances can attach to solid or semi-solid surfaces and clog up boat engines or distribution pipes at water treatment facilities. In those cases, the mussels can disrupt recreation and cause millions of dollars in damage to infrastructure. Once mussels are introduced into a region’s waterway, they are impossible to remove.

The greatest risk comes from boats traveling out of state, particularly to Lake Powell, on the Utah-Arizona border. The popular destination for Colorado boaters is infested with quagga mussels. Any time boaters travel outside of the state, it’s even more important that they ensure their boats are cleaned, drained and dry before launching back into Colorado, Walters said.

“Our program has been effective for almost 15 years at stopping these species from becoming established in Colorado waters,” he said. “But many other states don’t have the same level of protection, so every year mussels spread into new waters in our surrounding states, which increases our level of risk here in Colorado.”

For some, the inspection process could take less than 1 minute, said Luke Stucker, a senior ranger managing the aquatic nuisance program, at Cherry Creek State Park. If the boat has just returned from an area containing many invasive species, such as Lake Powell, the decontamination process will likely take longer, he said.

Every state park has a decontamination station, where boats sit on a trailer, away from bodies of water. Inspectors move through the vessel, checking the rear, outside and interior compartments of the boat. Then, 140-degree water is used to decontaminate the boat, killing any invasive species present. All the water is then drained into an open field or retention pond, Stucker said.

Most boaters are already aware of their responsibility to have their boats inspected before launching it into local water. But the pandemic added a new layer of complexity for state leaders trying to keep local lakes and reservoirs safe. Many people became first-time boaters during the pandemic and aren’t educated about the inspection process and the need for it, Stucker said.

Mussels can live outside of water for 27 days under the right conditions. The filter feeders can pass almost an entire liter of water through their shells each day, consuming nutrients needed by other fish and plants in the ecosystem.

Their high levels of filter feeding can alter food sources in lakes and reservoirs. And when mussels defecate or dry out on shorelines, they can cause a rancid smell, making it less desirable to recreate in these areas, Walters said.

“There’s a whole slew of potential recreational impacts,” he added. “In Eastern Europe, they had a role in filtering water and were a food source for native species that kept them in check. Here in Colorado, they would not serve much of a purpose, and would mostly cause problems.”

Inspectors are among those with the most important jobs in the state, which is to protect Colorado’s waterways, Stucker said. As an avid boater, he works to ensure that his kids can grow up with the same opportunities he had as a child while recreating on Colorado’s lakes and rivers.

“If I can prevent that mussel boat from launching, or if my inspectors can prevent that mussel boat from launching, then it’s a win in my book,” he said.

This story is from The Colorado Sun, a journalist-owned news outlet based in Denver and covering the state. For more, and to support The Colorado Sun, visit The Colorado Sun is a partner in the Colorado News Conservancy, owner of Colorado Community Media.


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