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The environment desk at Aspen Public Radio covers issues in the Roaring Fork Valley and throughout the state of Colorado including water use and quality, impact of recreation, population growth and oil and gas development. APR’s Environment Reporter is Elizabeth Stewart-Severy.

Mussel screenings: Officials work to keep invasive species at bay

Elizabeth Stewart-Severy
Aspen Public Radio

Visitors at Ruedi Reservoir this summer will find new gates at the boat ramp, as officials are restricting access so they can more effectively screen for invasive species of mussels. Keeping these creatures out of the reservoir is top priority.

On a windy afternoon in late May, the first big boating weekend of the summer, Mark Fuller stood by the gates at the Ruedi Reservoir boat ramp. All vessels in and out of the water are closely inspected.

“What we’re looking for are boats that have been cleaned, that have been drained of water and that are dry,” Fuller explained.  

Fuller is the director of the Ruedi Water and Power Authority, tasked with keeping two invasive species of mussels out of the reservoir. Zebra and quagga mussels have infested waters in nearly all of Colorado’s neighboring states, and officials are concerned about people from affected areas bringing the creatures in on wet boats.

Credit Elizabeth Stewart-Severy / Aspen Public Radio
Aspen Public Radio
A boat inspector tags vessels leaving Ruedi Reservoir, showing that they have been cleared.

“The larval form of these animals can live in any wet surface for an extremely long time, even [on] a wet towel or a wet sponge,” Fuller said.

For the first time, no boat is allowed on the water unless it’s been inspected. Fuller has worked with seven local governments, the U.S. Forest Service and the Ute Water Conservancy to secure triple the amount of funding of years’ past. This year, screenings are seven days a week instead of five, and the lake is only to open to boats when inspections are happening — from dawn til dusk.  

So, why the concern? Well, the mussels are filter feeders and they eat the smallest plankton, the base of the aquatic food chain.

“They can filter that water and take that base of the food web out at an alarming rate, which then, there’s no food for the small fishies, and then there’s no food for the big fishies,” said Elizabeth Brown, an expert on invasive species with Colorado Parks and Wildlife (CPW). “So it basically can impact the food web from the bottom up.”


Plus, mussels use a strong, silky fiber called a byssal thread to attach themselves to pretty much any hard surface — rocks, dams, boats, flip flops. Fuller said officials from CPW brought in a sandal that had been dropped in an infested lake.

“It was just this shoe-shaped mass of shell, of these creatures who had not only glommed onto the flip flop but then had glommed on to each other,” he said. “It’s really scary.”

When the mussels attach to other hard surfaces, like the inner workings of dams, it can be even more frightening. Fuller said an infestation at Ruedi could mean constant maintenance to keep vital parts of the dam working and the right amount of water flowing out of the reservoir.

In addition to clogging infrastructure, Brown explained that zebra and quagga mussels can sometimes attach to and smother native mollusks.

“So, they really can have a pretty tremendous impact because they can crash the food web from two different layers,” she said.

Once these mussels get into a body of water, there’s no getting them out.

So far, Colorado’s inspection system has been successful in preventing the spread of these mussels, but other popular spots have not been so lucky. Mark Anderson is an aquatic ecologist for the National Park Service.

“We watched from 2013 to 2016 as their population expanded and moved across Lake Powell,” he said. That’s more than 200 miles in three years.

In trying to prevent Lake Powell from being infested, the Park Service spent more than a million dollars annually, but staff still couldn’t keep up with the 400,000 boat launches on the lake every year.

“The whole way through our prevention program, we always felt like we were just barely a step ahead of it,” Anderson said. “I think we just weren’t able to move fast enough, ultimately.”

As officials at Lake Powell keep an extra eye on infrastructure there, they are also working to contain the mussels and help prevent infestations elsewhere. From Lake Powell to Ruedi, and at reservoirs across the West, the mantra is “clean, drain and dry.”

It’s a way of educating boaters about their role in stopping the spread of invasive species, even as state funding for inspections dries up. Colorado Parks and Wildlife lost about $4 million in funding in 2016, and boaters might feel the consequences.

Harvey Gap Reservoir near Rifle is no longer allowing motorized boats, and CPW programs that monitor other aquatic species have been cut to direct more attention to this most pressing concern. Brown said these mussels are the most environmentally devastating and economically challenging species in the country. It’s going to take creative partnerships to keep the inspections going.

“If we can all keep working together — boaters and industry and governments together — we can stay ahead of this issue and protect boating and fishing and infrastructure for water in Colorado,” Brown said.

And that’s what’s happening at Ruedi, where nine different entities are keeping the mussels at bay.

Aspen native Elizabeth Stewart-Severy is excited to be making a return to both the Red Brick, where she attended kindergarten, and the field of journalism. She has spent her entire life playing in the mountains and rivers around Aspen, and is thrilled to be reporting about all things environmental in this special place. She attended the University of Colorado with a Boettcher Scholarship, and graduated as the top student from the School of Journalism in 2006. Her lifelong love of hockey lead to a stint working for the Colorado Avalanche, and she still plays in local leagues and coaches the Aspen Junior Hockey U-19 girls.
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