Tiny invaders

Zebra Mussels have attached themselves to a beer can that was submerged for several weeks in the summer of 2015 due to flooding at Temple Lake Park on Lake Belton.

Zebra mussels — first found locally in Lake Belton in 2013 and in Stillhouse Hollow Lake in 2016 — continue to spread across Texas lakes.

Two bodies of water — Medina Lake near Bandera and Lake Placid near Sequin are the latest lakes to be re-classified as “detected” and “fully invested,” respectively, Texas Parks and Wildlife Department said.

Infested status signifies that there is evidence of an established, reproducing population of zebra mussels in the lakes, the agency said.

The detection in Medina Lake marks the first introduction of invasive zebra mussels in the San Antonio River Basin. TWPD received a photograph on Feb. 11 from a resident that showed a zebra mussel at a boat ramp. Biologists later located two zebra mussels attached to rocks along the shoreline.

Another search on Feb. 24 by the Bandera County River Authority & Groundwater District located a single zebra mussel attached to a dock about three miles upstream from the first location where mussels were detected. The agency later conducted additional surveys of shorelines, boat docks, boat hulls and engines at numerous sites around the lake; no additional zebra mussels were found.

Due to these discoveries, Medina Lake will be designated “positive” for zebra mussels, which means there have been multiple detections, but evidence of a reproducing population has yet to be discovered.

Lake Placid was previously designated as “positive” for zebra mussels, but will now be upgraded to “fully infested” status, the parks department.

In May 2019, zebra mussel larvae and a single adult were documented at Lake Placid, but biologists had not yet found evidence of an established, reproducing population in the lake. However, in early February 2021, during some routine maintenance at the Lake Placid dam, Guadalupe-Blanco River Authority employees discovered a population of adult zebra mussels in the hydroelectric turbine near the bottom of the dam, TWPD said.

 “Although zebra mussels are now found in 31 Texas lakes, there are still many other lakes in the state that they haven’t invaded,” Brian Van Zee, TPWD inland fisheries regional director, said in a news release.

“Boaters play a critical role in preventing them from spreading to new lakes,” he said. “Before traveling from lake to lake, clean, drain and dry your boat and gear. 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,”

A status map showing all lakes where zebra mussels have been found in Texas is online at tpwd.texas.gov/zebramussels.

To learn more about zebra mussels and other invasive species in Texas, visit tpwd.texas.gov/StopInvasives.

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