No additional larval or adult zebra mussels have been found in the Colorado River or Government Highline Canal since veligers were first discovered in early July. A veliger is the free-floating, larval stage of the invasive mussel and can only be seen under a microscope. While zebra mussels were previously discovered in a lake in Loma, Colorado, this was the first time they had been detected in the Colorado River.
Colorado Parks and Wildlife (CPW) has finished water sampling for 2024. As of Nov. 1, CPW staff collected nearly 450 water samples from the Colorado River, Government Highline Canal, James M. Robb-Colorado River and Highline Lake state parks, as well as additional areas throughout the Grand Valley. The Bureau of Reclamation and the Grand Valley Water Entities collected additional samples within the canal system.
CPW has increased education efforts on the Colorado River, including voluntary boat inspections. Since July, CPW worked with local government and Bureau of Land Management partners to post signage and conduct outreach at multiple water access points from the De Beque Canyon to the Utah Westwater boat ramp. CPW staff made more than 4,000 face-to-face contacts on the Colorado River. During one multi-day operation in July, the agency talked to nearly 600 people regarding the importance of cleaning, draining and drying their boats and equipment.
In early September, CPW Aquatic Nuisance Species staff partnered with the United States Geological Survey to install an autonomous sampler on the Colorado River near the Grand Valley Water Users Canal diversion. The sampler was programmed to collect eDNA samples from the river once per day and store them for up to eight days. Technicians collect and replace the filters once a week.
“While we have concluded our sampling efforts for the year, our work is not done,” said Invasive Species Program Manager Robert Walters. “Staff will continue to look for opportunities to educate the public on simple steps to prevent the spread of zebra mussels or any invasive species in Colorado waters.”
Invasive species sampling will resume in the spring of 2025 once water temperatures rise and become suitable for veliger production again. With the designation of “positive” bodies of water, increased sampling in the Colorado River and Government Highline Canal will continue for the next five years.
On Nov. 18, CPW finished draining Highline Lake in Loma as part of the plan to eradicate zebra mussels from the lake. Small areas of water are expected to remain, but will evaporate with sun exposure or freeze with the colder temperatures. The lake will stay empty throughout the winter to expose as many areas as possible on the lake bed and shoreline — eliminating any remaining veligers or adult zebra mussels. During routine inspections in early November, park staff discovered five adult mussels, all of which were dead.
Highline Lake will be refilled and reopened to boating in the spring of 2025. CPW will begin restocking Highline Lake following the return of normal water levels.
(Source: Colorado Parks and Wildlife.)
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