Zebra mussels in Lake Marble Falls

Boaters are asked to take steps in curbing the spread of the invasive zebra mussel by cleaning, draining, and drying their watercraft after taking them out of Lake Marble Falls. Texas Parks and Wildlife Department and Lower Colorado River Authority officials announced December 12, 2019, that the lake is infested with zebra mussels. Staff photo by Daniel Clifton

Even before state officials declared a zebra mussel infestation of Lake Marble Falls, the city of Marble Falls was planning to update its infrastructure in preparation for the invasive species.

But when the Texas Parks and Wildlife Department announced December 13 that biologists had found a reproducing population of zebra mussels in the lake, it got real.

“The city had kind of known this was coming our way,” said Marble Falls City Engineer Kacey Paul. “We have zebra mussels both upstream and downstream of us.”

Previously, Texas Parks and Wildlife and the Lower Colorado River Authority announced lakes LBJ and Travis were infested with zebra mussels.

The city is in the process of developing a plan that will equip raw water-intake infrastructures with screens made of materials to which zebra mussels are less likely to adhere. The plan, pending approval by the Texas Commission on Environmental Quality, also calls for dispersing molluscicide to kill and prevent zebra mussels from infesting critical infrastructure.

The city has been visiting with neighboring municipalities that are dealing with zebra mussels to get their feedback on effective prevention products and strategies.

“It’s very important for us to try and get ahead of this,” Paul said. “Some of the municipalities that have been experiencing issues with them are having to scrape their infrastructure two or three times a year. (Zebra mussels) cover their screens. They fill up pipes. They’re very invasive.”

Though only an inch or so when at full size, the zebra mussel causes damage as a group as thousands of the invasive species can pack a space as small as a square foot. On June 22, the Texas Parks and Wildlife Department and the Lower Colorado River Authority confirmed an established, reproducing population of zebra mussels in Lake Travis. Photo courtesy of Texas Parks and Wildlife Department
Though only an inch or so when at full size, the zebra mussel causes damage as a group as thousands of the invasive species can pack a space as small as a square foot. Photo courtesy of the Texas Parks and Wildlife Department

Though individually small, zebra mussels amass in large colonies that can clog water intakes, damage docks, and even overtake shorelines.

Informing the public about how to prevent the spread of zebra mussels is currently the best defense against them, said Monica McGarrity, senior scientist for Aquatic Invasive Species at Texas Parks and Wildlife.

If boaters put a watercraft in the lake for the day, it’s essential to clean, drain, and dry the boat after taking it out, she said.

“That means clean off any mud or debris, any plants that might have zebra mussels attached to them, checking the anchor really well because those pick up zebra mussels from the bottom of the lake,” McGarrity said. “Drain all of the water out of the boat, that is the law. Get all that residual water out that might contain zebra mussel larvae.”

Drying watercraft is especially crucial during cold weather because zebra mussels can survive longer above water in lower temperatures, closing their shells to trap water inside. Drying a boat at the peak of summer might take a couple of days, but, in late fall and winter, it could take a week or more.

While chemical and UV treatments can help minimize damage in and around intakes and other structures that process water on the lake, there is currently no way to get rid of zebra mussels in their entirety.

“Once they get in, there’s nothing that can be done to get rid of them altogether,” McGarrity said. “Keeping them out in the first place is the most effective strategy.”

U.S. scientists have conducted experiments and trials to deter and eliminate the mussels in smaller bodies of water, such as quarries, but it is too early to tell if these methods are effective.

“(Zebra mussels) haven’t been here that long,” McGarrity said of the freshwater mollusks that first arrived in the United States from Eurasia in the 1980s. “The hope is that scientists can find a way to help control that population. But, right now, there isn’t anything that can be done. That’s why it’s important for boaters to take those steps.”

Visit tpwd.texas.gov or call 512-389-4848 for information, recommendations, and case-specific advice on caring for watercraft and preventing the spread of zebra mussels.

alex@thepicayune.com

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