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Lake Waco zebra mussels eradicated; scenario unlikely in infested Highland Lakes

Zebra mussels

Even though zebra mussels were eradicated from Lake Waco, Texas Parks and Wildlife Department officials don’t believe wiping the invasive species out of the Highland Lakes chain is possible due to the infestation level. The best thing Highland Lakes boaters can do is clean, drain, and dry their watercraft to prevent the spread of zebra mussels to uninfested lakes. Photo by Texas Parks and Wildlife Department

Invasive zebra mussels were recently eradicated from Lake Waco, but that is unlikely to happen in infected waters in the Highland Lakes chain, announced Texas Parks and Wildlife Department officials Jan. 21.

“Unfortunately, that was a very unique situation,” said Monica McGarrity, TPWD senior scientist for Aquatic Invasive Species Management, about the Lake Waco eradication. “If we had a situation of a new lake reported, maybe it could be done. But when you look at, say, Lake Travis, the zebra mussels are so well-established. They are all along the shores, along the bottom. It just can’t be done there.”

The same holds true farther up the chain at Lake Buchanan, which was listed as infested in December 2020. Currently, lakes Marble Falls, LBJ, Buchanan, and Travis are on the state’s infested list. Infestation is defined as “an established, reproducing population of zebra mussels” in a lake or body of water.

Zebra mussels have not been reported in Inks Lake as of December 2020, and officials are urging people to keep an eye on the lake and report any sightings of the invasive species.

Even though Lake Buchanan was only deemed infested in December 2020, McGarrity said the zebra mussel population included both adults and larvae in several spots. She added that the larvae are also likely moving about the lake, making it impossible to replicate what was accomplished at Lake Waco.

“At Lake Waco, we caught them right before they were getting to peak reproduction season,” McGarrity said.

The key to successfully ridding Lake Waco of the zebra mussels hinged on the very limited area the mussels had invaded, quick identification, and a team response.

City of Waco employees noticed possible zebra mussels at a boat ramp in September 2014 and reported it immediately.

“We went out and did a survey and found they were only in that one area by the boat ramp,” McGarrity said.

Officials also located the source of the zebra mussel infestation, a nearby barge that had been brought to the lake from somewhere else. The barge was removed within two days of the initial report.

TPWD deemed the lake as “positive” for zebra mussels but not “infested.”

In October 2014, Texas Parks and Wildlife, the U.S. Army Corps of Engineers, and the city of Waco installed more than an acre of plastic sheeting along the shoreline and the bottom of the area where the zebra mussels had been found. The sheeting blocked oxygen to the creatures to stop their reproduction and keep them from spreading across the lake.

Crews removed the sheeting in March 2015. TPWD officials continued to monitor the lake and deemed it “undetected/negative” in January 2021.

Zebra mussels are an Eurasian hard-shelled mussel that was first detected in Lake St. Clair between Canada and Michigan in 1988 and spread to the Great Lakes region. They were found in Lake Texoma in 2009 and have since spread to about 31 Texas lakes.

Though small in size individually, about 3.5 centimeters to 4 centimeters maximum, zebra mussels congregate in large masses or colonies. They can cause problems for water intakes and cover docks and cling to watercraft. With such a massive number on shores and lake bottoms, people can cut their feet or arms if they come in contact with the shells.

Though there’s no known way of controlling large areas of zebra mussels at this time, McGarrity noted that, once established, the population seems to peak over the first one to three years.

“Then, they’ll decline, and they’ll level out a bit, but then they may increase again,” she said. “It’s cyclic. A lot of it depends on their food, plankton.”

The best prospect right now, McGarrity said, is to stop the spread of the species. Individuals are asked to drain, clean and dry their boats and watercraft or anything else that comes into contact with the water after each use and before transporting them to another lake. Also, if a person has stored a boat, barge, or similar craft on a lake, particularly a lake deemed “positive” or “infested,” they must decontaminate if before moving it to another body of water.

And, if someone sees zebra mussels, McGarrity urged them to report the sightings.

“We don’t want any other lakes to get infested,” she said.

For more information on zebra mussels or to report a sighting, visit the Texas Invasives website.