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Highline Lake Zebra Mussel Levels Reach Record High

Invasive shellfish were found on park equipment in October, impacting management plans for the Mesa County recreation area.

Updated on Oct. 30, 2026 in Hiking

Gouache-painted editorial illustration of a weathered dock post densely covered in small, jagged zebra mussel shells.
Invasive zebra mussels reached record numbers at Highline Lake in Mesa County, complicating ongoing environmental efforts to contain the species. AI Illustration. Upload story photo >

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Do you believe boaters in your community should be required to clean equipment to prevent invasives?

Colorado Parks and Wildlife staff identified a record number of invasive adult zebra mussels on equipment removed from Highline Lake on October 3, 2026. These mussels were found on docks and buoys during routine seasonal maintenance at the Mesa County park.

Why it matters

The discovery marks a significant increase in the presence of these invasive shellfish compared to previous years, complicating efforts to manage the infestation. The persistent mussel presence highlights the challenges of containing the species within the regional watershed.

Official inspection findings from October 2026 show a record volume of zebra mussels on lake equipment compared to all years since the initial 2022 discovery. The current extent of the infestation across the broader Colorado River and Highline Canal systems remains under investigation.

The players

Colorado Parks and Wildlife

The state agency responsible for managing wildlife, state parks, and invasive species containment efforts across Colorado.

The details

Zebra mussels are invasive freshwater shellfish that attach to hard surfaces like docks, buoys, and boat hulls. They reproduce rapidly, with microscopic larvae known as veligers spreading through water currents to colonize new areas. After Highline Lake was drained in 2024 to attempt eradication, the presence of these mussels on equipment indicates the population has persisted and expanded despite previous interventions.

Timeline

  1. 2022: Zebra mussels were first discovered in Highline Lake.

  2. 2024: The lake was fully drained for eradication efforts.

  3. Summer 2024: Veligers were detected in the Colorado River and Highline Canal.

  4. July 2025: The source of the infestation was identified in Eagle County.

  5. October 3, 2026: Staff removed equipment for winter inspection.

Health Landscape

The persistent infestation of Highline Lake follows ongoing efforts by Colorado Parks and Wildlife to contain invasive zebra mussels across the state. This discovery challenges the effectiveness of previous eradication measures, such as full lake drainage, in managing this regional ecological threat.

While zebra mussels primarily impact water infrastructure and ecosystems, they can create sharp, hazardous shells on submerged rocks or structures in affected areas. Hikers and water enthusiasts at Highline Lake should wear appropriate footwear when entering the water to avoid potential injuries from the shells.

The takeaway

The return of zebra mussels to Highline Lake serves as a reminder of how quickly invasive species can re-establish themselves in aquatic environments. Visitors should adhere to all posted signage and equipment cleaning requirements to help slow the spread of these organisms to other Colorado waters.

Further reading

For more information on how to protect local waterways during your outdoor excursions, visit Hiking.

Live Poll

Do you believe boaters in your community should be required to clean equipment to prevent invasives?