After years of taking steps to keep zebra mussels out of Colorado's rivers and lakes, state officials said on Tuesday they are “devastated” to learn the invasive species has now made its way into the Colorado River, potentially affecting four states, and they are working on a rapid response to stop it from spreading.
"This news is devastating,” said Tina Bergonzini, Grand Valley Water Users Association general manager “Having our canal and the Colorado River test positive increases the threat of this invasive species and could impact everyone in the Grand Valley. The ramifications cannot be underestimated or overstated from irrigation to drinking water.”
According to the Colorado Parks and Wildlife, the zebra mussel was found in the Colorado River and Government High Line Canal through routine testing in early July.
On July 1, the state’s Aquatic Nuisance Species team collected a plankton sample from the Government Highline Canal near Clifton. The sample was evaluated at a lab in Denver, where a suspected single zebra mussel veliger was found, officials said.
A veliger is the free-floating larval stage of a mussel. At this stage in the life cycle, a zebra mussel can only be confirmed through a microscope. The mussels eat plankton, which takes away from fish that rely on it for food.
After further analysis on July 9, the lab notified Invasive Species Manager Robert Walters that the sample was positive for zebra mussel DNA, officials said.
Since the positive testing, the nuisance species team had collected plankton samples from two locations in the Colorado River upstream of the Grand Valley Water Users Canal. By July 11, both samples were confirmed for zebra mussel DNA.
Justyn Liff, the Bureau of Reclamation's public affairs specialist, told Colorado Politics that sampling will increase upstream, and more meetings will be held between state and federal agencies to develop a solution to stop the species from spreading.
Colorado Parks and Wildlife officials said that, with single detections in both waters, the areas are now designated as “suspect” for the presence of zebra mussels. The response must be rapid, with the state wildlife agency rolling out the Invasive Species Rapid Response Plan, which starts with taking more samples to determine if the official classification should be changed from “suspect” to “positive.”
“This challenging discovery has ecological and economic impacts not only on the Grand Valley but potential statewide impacts as well,” Jeff Davis, the director of CPW said in the news release. “CPW is committed to working with all of our partners as we work to better understand the extent of this discovery and the next steps in protecting the natural resources and infrastructure.”
Female zebra mussels can produce up to one million eggs in a spawning season, which is a year. A female zebra mussel can begin reproducing within six to seven weeks of attaching, producing between 30,000 and 40,000 eggs in each cycle.
As the mussels mature, they bond to surfaces with byssal threads, making them difficult to remove. A zebra mussel's lifespan is five to six years.
Sign Up For Free: Denver Gazette Outdoors
View all of our newsletters.
Success! Thank you for subscribing to our newsletter.
Between their rapid reproduction and their ability to attach by byssal threads, mussels can clog waterways, creating costly maintenance issues.
Liff said that various solutions are being discussed. One option could be to add a “coating” to any structures the mussels can attach to. She also mentioned the use of UV lighting.
“We will work with parks and wildlife and water users to see what options we have to prevent the veliger from spreading,” Liff said.
Ed Warner, the area manager for the Bureau of Reclamation for the Western Colorado Area Office, said, “We know how much effort CPW has put into keeping the Colorado River clear of zebra mussels. This is an extremely difficult scenario for all who rely on the Upper Colorado River system.”
Small boats, kayaks, paddleboards can spread zebra mussels
Colorado wildlife officials have been working for several years to stop the spread of zebra mussels in lakes and rivers. The freshwater invasive species is being spread through boats and recreational activities.
Liff explained that there is a misconception that they are spread by big boats. However, she said small boats, kayaks, paddleboards, and blow-up devices are spreading the young mussels from waterway to waterway.
“Big boats are required to get washed off after leaving the water,” Liff said. “If you have a floatation device, it’s important to clean and dry it.”
Liff said it is common to take a device like a kayak or a paddle board from one reservoir to the next. If it isn’t cleaned and dried in between sessions, the potential to release young mussels into each waterway is high.
The state has stepped up inspections of boats and devices. In May, Colorado Parks and Wildlife highlighted that watercraft inspections helped prevent the spread of disease during Memorial Day weekend.
In a news release, the agency said that through various check stations, people were required to have their watercraft inspected before moving on to lakes and reservoirs.
If a watercraft is not cleaned and dried correctly, Liff said adult mussels can attach and be released in a new waterway ready to reproduce.
Liff said it is essential for anyone using a watercraft to clean and adequately let the device dry out before entering another body of water.
