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July 9, 2015

After Floods, Boaters Reminded to help Stem Spread of Invasive Zebra Mussels

AUSTIN— Boaters in Texas are being reminded that their actions are critical to help stem the spread of invasive zebra mussels. Despite recent flooding that some feared might spread the dangerous nuisance species, experts say that boaters who “Clean, Drain and Dry” their boats, trailers and gear before traveling from one Texas waterway to another are still key to containing the costly problem.

While recent rains have helped refill drought-parched reservoirs, rivers and bays across Texas, experts say this could potentially help spread the zebra mussels downstream. Zebra mussel larvae, called veligers, are suspended in the water column for a month or so after spawning, and they are readily transported downstream with flowing water. This is especially true now, at a time of year when zebra mussels are spawning, because there are likely many veligers in the water and they can be moved a long distance downstream in the flows Texas is now experiencing.

“However, despite the danger of flood distribution, zebra mussels are also susceptible to rough conditions caused by floods, such as water turbulence, turbidity (cloudy water), and low oxygen levels,” said Brian Van Zee, Inland Fisheries Regional Director in Waco for Texas Parks and Wildlife Department. “So these flood conditions could potentially help by causing high levels of zebra mussel mortality. Right now it’s hard to say what impact the flooding will have on zebra mussel populations. We probably won’t really know for months, as we continue monitoring efforts.”

Van Zee said that while flooding can spread zebra mussels downstream within the same river basin, the only way zebra mussels would likely move to another basin would be via boaters or interbasin transfers of water through pipelines from one lake or river basin to another. Right now, the Red River, Trinity River, and Brazos River systems are the only river basins where zebra mussels have been found.

“Besides the Red, Brazos and Trinity basins, all the other river basins in the state are still uninfested, and boaters’ actions are still absolutely vital to help prevent zebra mussels from spreading to any new river basins,” Van Zee said. “Boaters getting informed and taking action to help is still our best defense.”

Boaters won’t be unsupported. A coalition of river authorities, water districts and municipalities across the state, led by the Texas Parks and Wildlife Department, is investing more than $400,000 in a zebra mussel public information campaign; the largest such investment in public awareness since zebra mussels were discovered in Texas in 2009.

It is illegal to possess or transport any prohibited aquatic invasive species in Texas. Since zebra mussel veligers are invisible to the naked eye, boaters must drain all water from their boat and all receptacles on board when traveling on a public road to or from a public water body in Texas.

Originally from Eurasia, the rapidly reproducing mussels pose serious economic and recreational threats. They can clog water intake pipes, damage boats and motors by attaching to boat hulls and clogging water-cooling systems, completely cover anything under water, and litter the shoreline with their sharp shells. They can damage drinking water facilities and electric power plants, causing losses estimated in the millions of dollars annually.

Zebra mussels have been found in seven lakes in Texas since they were first discovered in Lake Texoma in 2009. Other infested lakes include Lake Ray Roberts, Lakes Bridgeport, Lavon, Lewisville, Belton, and most recently in Lake Waco. It’s worth noting that while this year’s rains have generally been good for boaters across most of Texas, flooding has caused boat ramp closures on many of the infested lakes, including Texoma, Lavon, and Ray Roberts, and some boat ramps on Belton and Waco. As the water recedes and boat ramps re-open on infested lakes, boaters should be vigilant about zebra mussels.

Partners for the awareness campaign include; the North Texas Municipal Water District; Tarrant Regional Water District; City of Dallas Water Utilities Department; Trinity River Authority; San Jacinto River Authority; Sabine River Authority; Brazos River Authority; Guadalupe-Blanco River Authority; Lower Colorado River Authority; Upper Trinity Regional Water District; City of Houston; City of Grapevine; Water Oriented Recreation District of Comal County; the Lady Bird Johnson Wildflower Center and the Sport Fish Restoration Program.

Information about zebra mussels can be found at

For images of zebra mussels, visit:

Video about zebra mussels is also available, including:

Stop Zebra Mussels — Public Service Announcement:

Attack of the Zebra Mussels! — Public Service Announcement:


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