Green Mountain Reservoir is now officially clear of a prohibited aquatic nuisance species, the quagga mussel larvae, which was found in the Summit County body of water in 2017.
The reservoir, after three consecutive years of “negative” testing, has been “delisted” and Colorado, statewide, is currently considered negative for both zebra and quagga mussels, said Robert Walters, invasive species specialist with Colorado Parks and Wildlife.
“This is absolutely good news,” Walters said. “This makes Colorado the only state in the nation to go from positive to completely delisted.”
When pesky mussels take hold, they invade bodies of water in the millions, exhausting plankton and “devastating the basis of the aquatic food web,” Walters said.
With plankton gone, higher aquatic species, including “sport fish,” die off because of the interruption in the food source.
“Rainbow trout, if it didn’t take them out completely, it would impact the quality of those fish,” Walters said.
Beyond ecological impact, mussels, in massive numbers, are also known to destroy and wreck infrastructure, including pipe, water treatment plants and dams. Construction repair and replacement of damaged property and machinery, including boat engines, is a massive cost to consumers and business, Walters said.
Waters infested by zebra and quagga mussels are widespread in states east of Colorado, and in Southern California, Nevada and Arizona, according to the U.S. Geological Survey.
In Colorado, more than 500 people are certified to inspect and decontaminate boats, keeping the nuisance out of the lakes, reservoirs and water systems. With more than 70 inspection locations, including at Cherry Creek and Chatfield reservoirs, more than 647,000 boats were inspected statewide in 2020, Walters said.
Inspectors decontaminated 24,771 boats and 100 boats were found to harbor mussels. Of the 100, some 72 vessels were traced to Lake Powell as the source of origin, Walters said.
In December, the national Aquatic Nuisance Species Task Force approved the State of Colorado Aquatic Nuisance Species (ANS) Management Plan to protect Colorado waterways.
“The approval of this plan is a significant milestone in ANS program history because it sets a clear path forward on how we can prevent and manage aquatic nuisance species in Colorado,” said Reid DeWalt, CPW’s assistant director for aquatic, terrestrial and natural resources, in a news release. “Invasive species have the potential to cause significant irreversible environmental impacts. The ANS management plan includes a coordinated prevention plan to keep Colorado’s waters free of ANS and a rapid response strategy that is designed to quickly contain new populations that may establish. This aims to minimize negative impacts on human safety, our wildlife populations and our native ecosystems.”
Mussel larvae, known as veligers, have been found in Colorado in the past.
Pueblo Reservoir was “delisted” in 2017. Blue Mesa, Jumbo, Granby, Shadow Mountain and Tarryall reservoirs, and Grand Lake were all delisted in 2014.
Local, state and federal officials have worked hard over the years, through tireless vessel inspections and decontaminations, in warding off the mussels in Colorado.
“We continue to have a growing number of infestations in surrounding states,” Walters said. “So, we can’t drop our guard.”
While microscopic and larvae stage of the invasive zebra and quagga mussels have been detected in Colorado waterways, grown mussels have not.
“We have never found an adult zebra or quagga mussel,” Walters said.
