Colorado Parks and Wildlife has finalized a new plan to eradicate zebra mussels at Highline Lake State Park after five adult mussels were found while removing buoys on Sunday, Oct. 1.
“We did not make this decision lightly or in haste,” said Invasive Species Program Manager Robert Walters. “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 that work that was performed last spring.”
The new plan will once again be a phased approach. The first phase will begin late 2023, with the second phase taking place gradually over 2024. During the first phase, CPW staff will apply a higher concentration of EarthTec QZ, the same EPA-registered 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.
“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,” said Walters. “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.”
In early 2024, CPW will begin slowly lowering Highline Lake with an anticipated complete emptying of the lake by the end of the year.
With the lower water levels, CPW is announcing Highline Lake will be closed to all motorized boating for the 2024 boating season.
“We understand that this isn’t ideal for our boating and angling community,” said Alan Martinez, Highline Lake State Park Manager. “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.”
Unfortunately, CPW cannot move fish out of Highline Lake into other waters prior to draining due to the risk of moving viable mussels on or inside fish. In this case, the only option is to reduce fish loss by removing bag and possession limits.
Anglers are reminded, effective Monday, October 9, that an emergency fish salvage is in place at Highline Lake until further notice. All bag and possession limits for the reservoir are removed for the duration of the salvage. Anglers can keep all of the fish they catch from the shoreline utilizing the lawful angling methods currently allowed at the lake. CPW reminds anglers that all fish must be dead prior to transport away from the lake.
“Eradication of zebra mussels has been, and will continue to be, our goal at Highline Lake,” said Ben Felt, Northwest Region Senior Aquatic Biologist. “Earlier this year, we pursued an option that had the potential to eradicate the mussels while maintaining the fishery. Based on this recent discovery, we recognize achieving both is not feasible. 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.”