AUSTIN (KXAN) — The Texas Parks and Wildlife Department (TPWD) said Lake Walter E. Long in Travis County is now infested with zebra mussels.

The infestation signifies the mussels have an established population and are reproducing in the lake, the department explained in a press release Wednesday.

TPWD said it detected zebra mussel larvae in the lake in October 2018 and May 2019, but in later searches, including in 2021, the department did not find any juveniles or adults.

“The larvae are actually free-floating in the water, so they can be anywhere in the lake,” said Monica McGarrity, TPWD senior scientist of aquatic invasive species.

“When we’re sampling, we’re sampling only 1,000 liters of water out of that lake and finding a couple of larvae. So, it’s not possible to remove the larvae from the lake,” she added.

Then, this month, TPWD said biologists from the City of Austin Watershed Protection found two adult zebra mussels in the lake while conducting shoreline searches. That, they said, indicates the presence of an established zebra mussel population.

TPWD said zebra mussels have now spread to 34 Texas lakes, with 30 of them considered “fully infested.” McGarrity said that includes Lakes Travis and Austin.

“Really, once zebra mussels get into a lake, it’s extremely rare that anything can be done to eradicate them,” McGarrity said.

She said the message now is for people to take precautions and prevent further spread into more Texas lakes.

“Even though the lakes in the Travis County area are fully infested, there are other lakes elsewhere that are not, and just taking a few minutes to clean, drain and dry your boat or contact us if your boat’s been stored in the water to make sure it’s decontaminated properly before you move it, can really make a big difference for protecting other lakes,” McGarrity said.

A spokesperson for the City’s watershed department said Lake Walter E. Long isn’t used for drinking water, only Lakes Austin and Travis.

In 2019, McGarrity said some zebra mussels made their way inside of Austin Water’s pipeline and died there while one of the water plants was down for repairs.

“And we did have many Austin Water customers who experienced foul-smelling, foul-tasting water. So, that certainly can happen,” she said.

The department also said a private-access lake in Medina County is also now fully infested, likely due to being downstream of another fully-infested lake.

The map below shows where zebra mussels have been detected in Texas. An infested lake — those in red on the map below — has an established, reproducing population of zebra mussels. Lakes that have tested positive — blue on the map — have had multiple and/or repeated detections of zebra mussels, but there is no reproducing population.

Since zebra mussels are usually transported on or in boats, TPWD added boaters should clean and drain their boats before leaving the lake and allow everything to dry when they get home to help protect other lakes from becoming infested.

Zebra mussels can also attach to anything left in the water and hide in crevices, said TPWD, including anchors, and can survive for days out of water.

“Their larvae are microscopic and invisible to the naked eye, meaning they can be unknowingly transported by boats in residual water,” the TWPD release said.

TPWD said not only can invasive species hurt aquatic ecosystems, but they can also impact water infrastructure and lake activities like swimming.

They also said transporting these mollusks can get boaters in legal trouble in Texas, punishable with a fine of up to $500 per violation. TPWD also reminds everyone it’s the law for boaters to drain all water from their boat and any receptacles on board, like bait buckets, before leaving or going to a body of fresh water.

“They must also remove all invasive plants from the boat, trailer and tow vehicle before leaving a lake,” the department added in its press release.

TPWD said if you have stored your boat in a lake with zebra mussels, your boat is likely infested and at “an extremely high risk” for spreading the invasive species to a new lake. They urge you to call TPWD for help on how to decontaminate your boat at (512) 389-4848.

You can also find more information on how to clean, drain and dry your boat and equipment on the TPWD YouTube channel here and learn more about zebra mussels and other invasive species in Texas here.

If you find zebra mussels or other invasive species in a Texas lake or spot them on a boat or trailer, TPWD said you can report the sighting to TPWD at (512) 389-4848 or by emailing photos and location information to aquaticinvasives@tpwd.texas.gov.