Testing by the U.S. Geological Survey found zebra mussel DNA in Lake Lavon and one veliger, or larva.
Besides Lavon, the other lakes that have tested positive for zebra mussels are Ray Roberts, Lewisville, Texoma, Bridgeport and Belton.
Three other lakes — Grapevine, Fork and Tawakoni — tested positive for zebra mussel DNA. While it’s the first time the DNA has been detected in Lake Fork and Lake Tawakoni, it’s the third consecutive positive test for Lake Grapevine.
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“Grapevine is certainly a concern for us, the fact that the USGS has had three positive DNA hits,” said Brian Van Zee, regional director of inland fisheries for the Texas Parks and Wildlife Department. “It is in close proximity to Ray Roberts and Lewisville, where zebra mussels have already been found.”
Zebra mussels were first found in 2009 at Lake Texoma and also established a presence in Lake Ray Roberts, said Robert McMahon, professor emeritus of biology at the University of Texas at Arlington, who sampled 23 Texas lakes this year for Texas Parks and Wildlife.
“What we’ve found is they’re growing extremely rapidly and having shorter life spans than other parts of the United States,” McMahon said. “In Lake Texoma, there’s fairly massive infestation in the lower part of the lake. It usually takes longer than that. That is something water users have to be aware of in this state.”
The U.S. Geological Survey plans to do follow-up surveys at Lake Lavon this month. It will resume routine sampling this spring at all monitored lakes, including Texoma, Lavon, Ray Roberts, Ray Hubbard, Lewisville, Grapevine, Fork, Tawakoni and Palestine.
The first sign of zebra mussels in Texas came in 2006 when they were found on boats being transported from out of state to Lake Texoma.
Though zebra mussels can move from one lake to another by floating downstream, boats are believed to be the main way a lake becomes infested. The only way to guarantee that zebra mussels aren’t moved from one lake to another is to clean, drain and completely dry boats, trailers and gear when they leave a lake or stream.
“The biggest thing is when you go to visit these six lakes, please take time to drain these boats, particularly a big one that’s been on the lake or a marina for some time,” Van Zee said. “Ideally, it needs to be thoroughly cleaned and set out in dry storage for a month or two.”
Texas Parks and Wildlife’s goal is to slow the spread of zebra mussels, but Van Zee said it will be difficult to completely stop them.
“It’s certainly an uphill battle,” he said. “I don’t want to give the impression that we can completely stop them. But every year we keep them from getting into another lake, that’s one more year we don’t have to spend dollars on cleanup and prevention in those lakes.”
He also said it’s important to keep the mussels from jumping from one river basin to another because once they get into an upper reservoir in that basin, they will probably migrate to other reservoirs.
The mussels can clog public-water intake pipes and harm boats and motors. They can attach themselves to boat hulls and can clog water-cooling systems, and they can make beaches and shorelines treacherous with the razor-sharp edges of their shells.
Zebra mussels originated in the Balkans, Poland and the former Soviet Union. They are believed to have made their way to the Americas in the 1980s via the ballast water of a ship. The small invaders were first found in 1988 in Lake St. Clair, Mich., and are known to have infested 29 states and more than 600 lakes or reservoirs in the U.S.