Colorado Parks and Wildlife Expands Zebra Mussel Sampling Down Colorado River

Colorado Parks and Wildlife is cranking up the intensity of its search for zebra mussels along the Colorado River, launching a more aggressive, weekly sampling regimen in 2026 that stretches from Granby all the way down to the Utah border. This isn’t a tentative probe; it’s a full-scale mobilization following the confirmed arrival of the invasive species, with veligers spotted in July 2024 and adult mussels found in 2025, signaling that the little invaders have moved from transient visitors to established residents.

The state is doubling down on its efforts by teaming up with River Corps, an AmeriCorps program run by the nonprofit River Science, to handle the heavier lifting. Three River Corps members have been assigned specifically to help CPW’s aquatic nuisance species program, with two of them dedicated solely to monitoring the river’s pulse. You can feel the shift in strategy here — they aren’t just dipping nets anymore; they’re building a data infrastructure designed to make sense of the river’s health for everyone from recreational boaters to water resource managers.

The work is meticulous. Technicians are using plankton nets to pull water samples, targeting different life stages of the mussels to catch them at every turn. Those samples don’t just sit on a shelf; they’re shipped to the ANS lab in Denver for evaluation, while high-priority catches get tested for zebra mussel DNA at CPW’s Aquatic Animal Health Lab. It’s early detection on steroids, and it’s crucial because once these mussels set up shop, they’re nearly impossible to evict.

But the sampling is only half the battle. While the scientists are busy in the water, CPW staff, wildlife officers, and state park employees are hitting the boat launches between Palisade and Loma throughout the summer, educating locals and visitors on how to spot and stop the spread. They’re working closely with the U.S. Fish and Wildlife Service, too, because this is a joint operation, not a solo act.

The map of infestation is getting darker, and the news from the sources is clear about where the mussels have already claimed territory. Highline Lake at Highline Lake State Park was flagged back in 2022, and Mack Mesa Lake joined the list in 2025. Over at James M. Robb-Colorado River State Park, West and East Lake in the Wildlife Area Section were designated infested in 2025. The river itself, from the confluence of the Eagle River downstream to the state line, was declared infested in 2025. Red Rocks Lake at the Fruita Section of James M. Robb-Colorado River State Park also got the label in 2025. By 2026, Grand River Park in New Castle joins the list.

There’s a stark contrast in the data, though. Between the headwaters of the Colorado River and the confluence of the Eagle River, there have been no detections. The Eagle and Roaring Fork rivers remain clean. But CPW ANS staff expects more discoveries in the Grand Valley, particularly in privately owned bodies of water, as the increased sampling uncovers what was previously hidden. It’s a reminder that while the main stem is under control, the tributaries and side pools are still being mapped out, one sample at a time.

The air in the boat launches smells of damp canvas and diesel, a familiar scent that now carries a new weight. You watch a family rinse their trailer, the water dripping off the tires, wondering if those tiny larvae are clinging to the rubber, waiting for a warm river to carry them downstream.