COLORADO PARKS & WILDLIFE

Grand Junction, Colo. - Colorado Parks and Wildlife has begun the process of lowering Highline Lake in the continued efforts to eradicate zebra mussels in the lake and stop the spread into additional waters. 

“The next phase to remove zebra mussels from Highline Lake will be twofold,” said State Park Manager Alan Martinez. “Our goal is to eliminate the mussels while protecting a quality warm water fishery that has taken decades to build.” 

Over the next few months, Highline Lake will be lowered approximately 30 feet.  This is an additional 20 feet from the initial lowering that began Nov. 28, 2022 to inspect the pump at the inlet that pulls water from the reservoir into the Government Highline Canal. 

In addition to lowering the lake to expose areas along and near the shoreline to kill zebra mussels through the natural processes of desiccation and freezing, CPW will apply EarthTec QZ, an EPA-registered copper-based molluscicide, to the lake. Once the lake has reached the desired level and the ice has come off the lake, CPW will perform the first application of EarthTec QZ to the east side of the lake. Park staff believe this will occur around March 1. After two weeks, a second application will be added to the west side of the lake. 

“Attempting this eradication now while population densities remain low is not only our best opportunity for successful eradication in Highline Lake, but also our best chance to prevent the spread of this highly detrimental invasive species to other waters in the state,” said CPW Invasive Species Program Manager Robert Walters.  

This two-step application approach will allow fish and other aquatic species the ability to move to areas of the lake where concentrations of the chemical are initially lower. Water from the canal will be turned back on in April, with Highline Lake returning to normal levels around the first week of May. 

CPW will continue to monitor Highline Lake for the presence of zebra mussels on a weekly basis following this treatment. It is important to note, even if no evidence of zebra mussels are found in the first year, Highline Lake will be considered “infested” for five years. If no zebra mussels or other aquatic nuisance species are found during this time, the lake would return to a negative prevention water and the containment boat inspection and decontamination program that began in September will no longer be required.

“After consulting with Earth Science Laboratories and doing extensive research, we have seen some very promising results in other bodies of water around the U.S.,” said Walters. “We are optimistic that with the combination of lowering Highline Lake and the EarthTec QZ application, we will be able to eradicate the mussels while limiting impacts to non-target organisms including preservation of the warm water fishery that Northwest Region staff have worked so hard to build.”

What to expect for the 2023 boating season: 

• Boats launching at Highline Lake will continue to be subject to inspection and decontamination protocols prior to launching. All boats must be clean, drained, and dry prior to launching at Highline Lake. 

• Upon exiting the lake, all boaters will have their boat inspected and decontaminated and will be issued a blue receipt that indicates it was last used on a body of water with a known aquatic nuisance species. 

• Boaters can expect decreased ramp hours and longer exit wait times when boating resumes at Highline in May. 

“We can’t stress this enough, please hold onto your blue receipt inspection receipts,” said Martinez. If you travel to another body of water in Colorado and do not have proof of decontamination, there is a high likelihood that your boat will be decontaminated again. 

CPW staff first discovered the presence of invasive zebra mussels during routine ANS inspection Sept. 14, 2022. After the discovery of additional invasive mussels in Highline Lake in October, CPW changed the status from “Suspect” to “Infested.” Subsequent surveys have resulted in the detection of additional mussels within and immediately below Highline Lake. Additional surveys were taken downstream from Highline lake in the Mack Wash and Salt Creek, and no zebra mussels were found. 

This designation is a first for a body of water in Colorado. Extensive surveys by CPW of the Colorado River and The Government Highline Canal upstream of Highline Lake did not provide any evidence to indicate there is an established population upstream of the reservoir.​ To date, no zebra mussels have been found in Mack Mesa. 

For more information on zebra and quagga mussels, visit the CPW website.