The Zebra Mussel Threat

Zebra mussels are highly invasive freshwater mollusks, introduced to the United States in the late 1980s. They only grow to approximately an inch long, but have the ability to attach to most hard surfaces. They form dense colonies on docks, boats, and marinas, inside pipes, and on other structures under the water. Their microscopic larvae float freely in the water, allowing them to infiltrate boat motors and ballast tanks. Adults can survive for weeks out of water under certain conditions. These characteristics have allowed zebra mussels to spread through both natural and artificial waterways as well as over land by "hitchhiking" on commercial and recreational boats that aren’t properly cleaned, drained, and dried. Since they were first found in Lake Texoma (2009), invasive zebra mussels have infested many Texas waterways. They encrust shorelines, damage boats, and clog intake pipes of water and power production facilities. 

To combat the spread of this invasive species, Texas Parks and Wildlife Department has taken a multi-pronged approach.

Enlisting Public Support

  • A public awareness campaign, conducted during peak water recreation seasons, informs boaters and anglers about invasive zebra mussels and how they can help to slow the spread of this pest.
  • Marinas play a key role in the boating industry on Texas lakes and can serve as checkpoints or "gatekeepers" to help prevent contaminated boats from entering non-infested waters without being properly decontaminated. In summer 2016, TPWD visited nearly 80 marinas, providing informative materials for boat owners and sharing strategies and procedures for preventing the spread of invasive species. Marina outreach expands in 2019 with new public awareness items and information on decontamiting boats from infested waters.
  • Transport of zebra mussels attached to boats is illegal, but figuring out where to have your boat decontaminated can be a daunting task. We are working to identify locations that can provide fee-based decontamination services for infested boats to help us facilitate proper decontamination and inspection of boats.


Monitoring & Inspection

Boats that have been stored on infested lakes, in Texas and elsewhere, are at high risk of creating new infestations. Zebra mussels colonize hulls, propellers, water systems, and other parts of boats, including some spots where they are difficult to detect. TPWD staff work with marinas and boat owners to make sure these boats are thoroughly decontaminated and inspected before being moved to new locations.

Twice per year — in spring and fall — biologists from TPWD and numerous partner agencies monitor more than 50 Texas water bodies for early detection of zebra mussels. Early detection can reduce economic impacts of new infestations by helping to target boater advisories and enabling controlling authorities to prepare to deal with the problems caused by infestation. The partner group also monitors status of lakes where zebra mussel DNA was recently detected, along with monitoring population dynamics in some infested lakes.

TPWD staff checks a decontaminated boat

Collaborative Research

Downstream Dispersal and Risk Assessment

TPWD partnered with Texas Tech University (TTU) and Texas State University (TSU) to conduct the first ever Texas-specific zebra mussel risk assessments: studies that ask which Texas lakes are at greatest risk of invasion by zebra mussels and how far they are likely to spread downstream. The risk assessments considered a variety of factors such as lake characteristics, distance from other invaded lakes, and boater activity. Although results of these studies will help guide efforts to prevent and monitor for new infestations, they also show that potential for introductions to occur anywhere in Texas is high. Impounded river systems have created chains of reservoirs at risk of invasive species arriving not only via overland transport on boats, but also by downstream dispersal and pipeline transport. As in other states, successful zebra mussel settlement appears to be most common close to the reservoir source population. Although downstream dispersal research is ongoing, preliminary results suggest that man-made barriers may play a role in enabling zebra mussel dispersal in rivers.

Kayaker samples plankton

Text TPWD ZM to 468-311 to get updates by text.