CPW notifies public of "devastating" discovery in Colorado River

Officials have called the discovery of zebra mussel veligers in the Colorado River and Government Highline Canal "devastating" after the invasive species was detected during routine testing in July.

The initial detection occurred when Colorado Parks and Wildlife's Aquatic Nuisance Species team collected a plankton sample on July 1 from the Government Highline Canal near Clifton. A single zebra mussel veliger was found, with a veliger being the free-floating larval stage of the mussel that's only visible under a microscope.

The same team then collected plankton samples from two locations in the Colorado River upstream of the Grand Valley Water Users Canal diversion on July 8, finding a single zebra mussel veliger in each sample.

Officials clarified that no adults mussels have been found at any of the aforementioned locations.

With the detection of the veligers, both the Colorado River and the Government Highline Canal are considered "suspect" for the presence of zebra mussels. Increased sampling is underway to determine if a reclassification as "positive" is appropriate.

“This challenging discovery has ecological and economic impacts not only on the Grand Valley but potential statewide impacts as well. 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,” said CPW Director Jeff Davis.

It's expected that the presence of zebra mussels in the Colorado River would negatively impact native fish populations due to the mussels' filter-feeding strategy, which strips essential prey items, like plankton, from the water. Officials noted that slower-moving parts of the river, along with pools and eddies, are particularly at risk.

Another impact of zebra mussels is that the species can clog water infrastructures, leading to long-term maintenance issues.

"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. From irrigation to drinking water, the ramifications cannot be underestimated or overstated. Our efforts, alongside our partners at CPW and the BOR, will be increased to protect our infrastructure, the livelihoods of so many, and water security for us all.”

Colorado Parks and Wildlife stressed how important it is for those on Colorado's waters to take precautions and be proactive when it comes to preventing the spread of the zebra mussel species. It's important to clean, drain, and dry any water vessel after use.

Colorado Parks and Wildlife staff are set to continue to look into the situation as a determination is made about the best way to proceed.

Colorado's struggle to prevent the spread of zebra mussels in the state's waters is ongoing. Currently, Highline Lake is the only spot considered to be "infested" with the species, with the species first detected there in September 2022. Pueblo Lake, Granby Reservoir, Grand Lake, Shadow Mountain Reservoir, Willow Creek Reservoir, Tarryall Reservoir, Jumbo Reservoir, Green Mountain Reservoir, and Blue Mesa Reservoir have all tested positive for zebra mussels or the similar quagga mussel in the past.

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