Last month, Texas Parks and Wildlife Department announced that Lake Meredith, near Amarillo, was designated as “fully infested” with invasive zebra mussels.
Zebra mussels are native to Eurasia and likely made their way to America starting with the Great Lakes in the 1980s through ocean vessels coming from Europe. From there, zebra mussels have spread through the Mississippi River Basin and beyond, with boats unknowingly transporting larvae. Zebra mussel larvae are microscopic and free-floating in water. While adult zebra mussels can survive outside of water for up to a month.
Monica McGarrity is the senior scientist for aquatic invasive species with the Texas Parks and Wildlife Department (TPWD). She works to coordinate between agencies, states, and regions to provide guidance on invasive species, including outreach, prevention, detection, and management.
McGarrity explained that in the case of Lake Meredith, “infested” means the mussels are fully established and reproducing in the lake.
“Typically the populations in our Texas lakes tend to kind of take off within the first one to three years and rapidly increase,” she said.
The first infestation in Texas was found in Lake Texoma in 2009, according to TPWD. Since then, invasive mussels have been identified in 40 lakes in Texas and 35 have been declared fully infested. The department said that the population in Lake Meredith is likely dispersed throughout the reservoir and McGarrity said it could be a “steppingstone” to other western states.
“This is important, because not only is it a very long distance movement that puts nearby lakes at risk, it's a new river basin, and it also is close to I-40, which is a corridor heading west,” she explained.
Zebra mussels have “razor sharp shells” and McGarrity suggested that those visiting the lake be prepared to wear water shoes and be cautious around the edge of the water.
“The population's not at that level now, but definitely something to anticipate in the future,” she said.
McGarrity said that, as an invasive species, zebra mussels can affect the food supply of other filter-feeding species and can attach themselves to native mussels, impacting their health.
Native freshwater mussels settle on sediment and their larvae are not free-floating. McGarrity explained that one of the main concerns with zebra mussels is how they attach and damage infrastructure.
“The zebra mussels can attach to each other and form colonies that could be clogging, damaging to pipes and infrastructure,” she said. “So one of the main reasons why we work with a lot of partners on early detection is to try to give operators of any water treatment facilities or any facilities using raw surface water advance notice, so they can start mitigation.”
Along with being a recreation site, Lake Meredith is part of the Canadian River Municipal Water Authority (CRMWA), which provides water to eleven cities, including Lubbock. McGarrity said the CRMWA has been “very proactive” and has already begun implementing mitigation strategies.
Chad Pernell, deputy general manager of CRMWA, said the authority has been testing for zebra mussels multiple times a year since they first entered the state. At this stage, he said he is not overly concerned about the impact on cities that utilize the lake’s water.
“There's not a significant concern in terms of our water supply,” he said. “Over time, there have been ways that have been developed to treat zebra mussels and to mitigate the effect that they can have on our system.”
Current efforts include using a chemical treatment frequently used in reservoirs to control the zebra mussel population. In other cases, Pernell said some coatings can be put on infrastructure to keep mussels from sticking, but those have not been implemented yet.
CRMWA will continue looking into new developments and learning from other systems that have dealt with invasive mussels, he said.
Those visiting the lake can also help prevent the further spread of zebra mussels. TPWD requires that boaters clean, drain, and dry their crafts and equipment between visits to different bodies of water.
“When you're coming to Lake Meredith. Make sure you've cleaned, drained, and dried after leaving the previous lake you visited,” McGarrity instructed. “You might be bringing an invasive plant that's not present in the lake already. When you leave the lake, make sure you clean, drain, and dry before you go to another water body for the same reason.”
She said that for a boat that’s only been in the water for a few days, the concern is not mussels attaching to the vessel itself, but to mud or plants that may be on the boat. Meanwhile invisible larvae may be present in water stuck in the boat.
“Go ahead and drain all the water out of all the compartments, raise and lower the motor a couple of times to get the water out of there, and then open up all of the compartments and try to let it dry for a week if you can once you get home,” she encouraged.
Boats stored in water may have mussels attached in hard-to-reach crevices. In those cases, McGarrity recommended folks reach out to TPWD for guidance.
Draining boats, receptacles, and bait buckets before leaving or approaching public fresh water is mandatory under state law. And the fine for transporting “prohibited aquatic invasive species” in Texas is up to $500 per violation.
“Preventing the spread of zebra mussels requires everyone doing their part, and the more folks take a few minutes to clean, drain, and dry their boats, the more we can slow the spread of this invasive species,” McGarrity added. “They're already present in many of our lakes, but there are far more where they have not yet invaded, so let's all do our part and protect the lakes we love.”
You can learn more about invasive species, their impact on Texas lakes, and instructions on cleaning, draining, and drying equipment at tpwd.texas.gov/StopInvasives.
Those who have stored their board in a body of water known to have invasive mussels can contact Texas Parks and Wildlife Department at (512) 389-4848 for guidance on decontamination.