Colorado Parks and Wildlife plans to drain Highline Lake west of Grand Junction as part of additional efforts to eradicate an infestation of zebra mussels.

“We understand that this isn’t ideal for our boating and angling community,” said Alan Martinez, manager of Highline Lake State Park. “What we hope is that people see this and understand how serious this problem is, and that it can be avoided by simply cleaning, draining and drying your boat or any equipment that comes in contact with the water in between each and every use.”

A phased plan was finalized after five adult mussels were found while removing buoys on the lake on Oct. 1.

The first phase will begin later this year. CPW staff will apply a higher concentration of EarthTec QZ, the same copper-based molluscicide that was applied to the lake in March. The goal of this application is to suppress the population to minimize reproductive potential in 2024.

In early 2024, CPW will begin slowly lowering Highline Lake with an anticipated emptying of the lake by the end of the year. With lower water levels, Highline Lake will be closed to motorized boating for the 2024 season.

CPW can’t move fish out of Highline Lake due to the risk of moving viable mussels on or inside fish. The only option was to remove bag and possession limits for the duration of the salvage. Anglers can keep all the fish they catch from the shoreline using lawful methods. All fish must be dead prior to transporting them from the lake.

“We did not make this decision lightly or in haste,” said Robert Walters, manager of the CPW invasive species program. “Over the past year we have had numerous discussions with CPW’s Northwest Region aquatic, regional and state park staff, and we have come up with a plan that builds upon the work that was performed last spring.

“While the efforts in early 2023 did not achieve our ultimate goal of eradicating zebra mussels, we believe it helped to keep population numbers at a manageable level,” Walters said. “A single female zebra mussel can produce more than 30,000 eggs per reproductive cycle. Any mussel we can keep from reproducing in the immediate future increases the probability of our success next fall.”

Ben Felt, senior aquatic biologist with the Northwest Region, said eradication of zebra mussels remains the goal at Highline.

“To do nothing would be detrimental to Highline Lake and would put fisheries across the state at risk. CPW is committed to rebuilding the Highline Lake fishery once the zebra mussel eradication project is complete.”