Zebra mussels

This image shows a cluster of zebra mussels that were pulled from Lake Belton. As the recreation season begins, boaters are advised to take precautions against the invasive species.

The spread of zebra mussels in Texas lakes continues as three more reservoirs are now designated as “fully infested.”

Lake Brownwood, Inks Lake and Medina Lake, in the Colorado and San Antonio River basins, are infested with invasive zebra mussels, the Texas Parks and Wildlife Department said Thursday.

The agency said infested status signifies that there is an established, reproducing popula- tion of zebra mussels in each of the lakes. The designation comes after recent sampling efforts revealed evidence that zebra mussels in Lake Brownwood and Medina Lake are now fully established and reproducing as well as the detection of a new infestation in Inks Lake.

“As zebra mussels are continuing to spread westward and southward to new areas in Texas, and as those lakes become fully infested, nearby lakes have an increased risk of being invaded, and it is vital that boaters take steps to clean, drain, and dry boats to help slow the spread,” Monica McGarrity, a TPWD senior scientist for aquatic invasive species, said in a news release. “Boats owned or recently purchased that have been stored in the water must be decontaminated before moving them to another lake to prevent the spread of these highly invasive mussels.”

TPWD said zebra mussels have spread to 32 Texas lakes — including Bell County’s two reservoirs, Lake Belton and Stillhouse Hollow Lake. Twenty-seven of those lakes are fully infested.

At Lake Brownwood, about 140 miles northwest of Temple, zebra mussel larvae were first detected in plankton samples collected in November. Two zebra mussels were found on a pontoon boat at a marina on June 1 by employees of the Brown County Water Improvement District. Other zebra mussels have been found earlier this month, indicating an established, reproducing population, TPWD said.

In April, zebra mussel larvae were found in plankton samples collected by the Lower Colorado River Authority at Inks Lake in Burnet County, about 80 miles southwest of Temple.

Inks Lake now has an established reproducing zebra mussel population, TWPD said. Lake Buchanan, which is upstream of Inks Lake, became infested in 2020 and with inevitable downstream dispersal, the chances of Inks Lake becoming infested were extremely high, the agency said.

A zebra mussel sighting in February at Medina Lake led to other sightings in the spring — prompting the Bandera County River Authority & Groundwater District to conduct intensive shoreline and snorkeling surveys. The most recent discoveries, combined with the initial sightings in February, revealed numerous mussels of different sizes in multiple locations, indicating the presence of an established, reproducing population at Medina Lake, which is in the San Antonio area.

TPWD said boaters play a critical role in stopping the the spread of zebra mussels.

“Zebra mussels attach to boats and anything left in the water, including anchors, and can survive for days out of water, often hiding in crevices where they may not be seen easily,” the agency said. “Their larvae are microscopic and invisible to the naked eye, and can be unknowingly transported in residual water in boats. Boaters are urged to clean, drain and dry their boats and gear before traveling from lake to lake. Remove plants, mud and debris, drain all the water from the boat and gear, and then open up compartments once you get home and allow everything to dry completely for at least a week if possible.”

Texans who have stored their boats in the water at a lake with zebra mussels or purchased a boat stored on one of these lakes, it is likely infested with zebra mussels and poses an extremely high risk for moving this invasive species to a new lake, TPWD said.

Before moving your boat to another lake, call TPWD at 512-389-4848 for guidance on decontamination.

Transporting prohibited invasive species in Texas is illegal and punishable with a fine of up to $500 per violation. All boaters are required to drain water from their boat and onboard receptacles, including bait buckets, before leaving or approaching a body of fresh water.

TPWD and its partners monitor for zebra mussels in Texas lakes, but anyone who finds them in lakes where they haven’t been found before should report them immediately by emailing photos and location information to AquaticInvasives@tpwd.texas.gov.

A status map showing all lakes where zebra mussels have been found in Texas can be viewed at tpwd.texas.gov/ZebraMussels.

To learn more about zebra mussels, visit tpwd.texas.gov/StopInvasives.

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