Invasive mussels’ larvae in Colorado could eventually cause problems in Nevada

Evidence of invasive, destructive zebra mussels in the Colorado River could mean trouble for wildlife, boaters and water companies alike, but it’s not yet clear if the thumbnail-sized mollusk will appear in Southern Nevada as a result.

Colorado Parks and Wildlife this month found zebra mussels’ microscopic larvae, called veligers, in the Colorado River and Government Highline Canal near Grand Junction, Colo.

They will take more samples and increase testing for veligers to determine if the species has gained a foothold in Colorado’s waters, officials said. 

“They are prolific breeders, they change ecosystems over time,” said Kelly Stockton, a biologist who works in invasive mussel remediation. “If they find a good spot, they will proliferate and take over an area.”

Stockton said it’s not always clear what a “good spot” is for the species and its equally disruptive cousin, the quagga. The persistent mussels have survived in conditions and climates scientists initially thought they couldn’t withstand, she said.

“The quagga mussels like deeper, colder locations, however that doesn’t hold true out west,” Stockton said.

She said if an established population of zebra mussels develops it would still take them “years” to make it through the obstacles along the Colorado River to Lake Mead.

“But I don’t know that for sure,” she said. “The only good example we have is the Mississippi and Missouri River basins. They have traveled downstream over time, but is that the same river system as the Colorado River? No.”

Zebra mussels cut into native species’ food supply, reproduce quickly and have very few natural predators, Stockton said. Conspicuously clear water that used to be cloudy is a sign of infestation.

They additionally settle into boats, which is how they appear in new locations. They can also attach themselves to water infrastructure in large numbers and clog up pipes and filters if left unchecked.

Stockton’s company — KASF Consulting — uses different chemicals to kill off the mussels, but finding a compound that won’t harm the native wildlife always poses a challenge when it comes to removing the species, she said. Lately, she’s been experimenting with copper products.

The zebra mussel originally hitched a ride from its native Eastern Europe to the Great Lakes in the 1980s in the ballasts of large shipping vessels, according to the United States Geological Survey.

They quickly spread through the eastern United States, but their spread in the West has been slower. 

Lake Havasu, Lake Mojave and Lake Mead have been home to the quagga mussel since 2007, according to the Utah State University extension.

The Hoover Dam is already equipped to deal with the quagga, signing a 10-year contract with Atlantium Technologies for a system that filters water and kills quagga veligers with ultraviolet lights.

In 2015, the Bureau of Reclamation began spending$900,000 a year on equipment to keep the mussels from overwhelming the dam’s penstocks, cooling systems and filters.

“It’s a constant battle within the dams to keep the lines clear,” said Stockton, who worked with Atlantium on the system.

Thomas Ashley, a hydrologist for the Hoover Dam, said the dam’s hydropower facilities have much narrower pipes that quagga mussels could easily clog.

Every five years or so, teams of workers will go into one of the 30-foot-wide intake penstock towers, build scaffolding and scrape out five years’ worth of accumulated quagga mussels and shells.

“It has presented a burden, but so far it’s been a controllable burden,” Ashley said.

Slow-moving parts of the river are especially vulnerable, the Colorado Parks and Wildlife said. The U.S. Fish and Wildlife Service, National Park Service and other federal agencies urge boaters to properly clean, drain and dry their watercraft to prevent the mussels from damaging their equipment or spreading to new bodies of water.