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News Release
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TPWD News,, 512-389-8030

Aug. 17, 2009

Zebra Mussels Spreading in Texas

Invasive Threat Believed to be Entering Trinity River via Lake Lavon

AUSTIN, Texas — Invasive zebra mussels (Dreissena polymorpha) have been confirmed to have spread from Lake Texoma into the head waters of Lake Lavon, and experts fear they could eventually spread throughout the Red River and Trinity River watersheds.

Zebra mussels multiply rapidly and can block water treatment plant intakes and pipes as well as attach themselves to boats, ropes or anything else left in the water. They can cause declines in fish populations, native mussels, and birds. They can also restrict water flow in pipes, foul swimming beaches, damage boat engine cooling systems and cause navigation buoys to sink. The financial cost of controlling and removing zebra mussels from fouled water intake structures can be significant.

Since 2006 there have been five documented cases of zebra mussels being found on boats at Lake Texoma that were trailered in from other states. All five boats were quarantined and cleaned of all mussels prior to being allowed to launch into Lake Texoma. However, April 3 of this year marked the first time that an adult zebra mussel was documented as living in Texas waters. Since that time, additional live specimens have been reported in Lake Texoma and are now believed to be well established.

In addition, on Aug. 3 live zebra mussels were found in West Prong Sister Grove Creek in Grayson County approximately 300 yards downstream of the Lake Texoma water transfer pipe. This creek flows into Lake Lavon.

"The only motile stage of this animal is the veliger (larvae), which, in Lake Texoma, had to be a product of reproduction," said Bruce Hysmith, Texas Parks and Wildlife Department (TPWD) inland fisheries biologist for Lake Texoma.

"The larvae are free floating in the water column, and some were likely transported via the North Texas Municipal Water District water transfer system into West Prong Sister Grove Creek," Hysmith said. "While we have no proof, we feel certain zebra mussels are in Lake Lavon."

Hysmith said TPWD has deployed sampling equipment throughout Lake Lavon from the U.S. 380 bridge to the south shoreline and will be monitoring to see if zebra mussels show up and confirm department suspicions.

"Lake Lavon is in the headwaters of the vast Trinity River Basin, which extends southward to the Gulf of Mexico, so the potential impacts to water quality, fisheries resources, water distribution systems and recreation are huge," Hysmith said.

"Zebra mussels have the potential to be an even greater threat to Texas freshwater resources than invasive aquatic plants such as giant salvinia and toxic organisms such as golden alga," said Phil Durocher, director of TPWD’s Inland Fisheries Division.

Zebra mussels pose a possible threat to North Texas water supply and distribution systems. Their spread is magnified by the interconnection of many reservoirs within the DFW area through water transfer pipelines.

According to the online National Atlas of the United States, "Once zebra mussels become established in a water body, they are impossible to eradicate with the technology currently available. The cost of dealing with zebra mussels varies widely, [but] for many plants, costs average hundreds of thousands of dollars a year."

Zebra mussels originated in the Balkans, Poland, and the former Soviet Union and were first introduced in North American in 1988 in Lake St. Clair, a small water body connecting Lakes Huron and Erie.

In the coming weeks TPWD will be working with local, state and federal agencies, reservoir controlling authorities and water districts to develop a plan for dealing with this latest invasive threat to Texas waters.

Boaters and anglers can help slow the spread of zebra mussels from one water body to another by practicing the following steps when leaving any water suspected of having zebra mussels.

Boaters and anglers can also help by reporting sightings of suspected zebra mussels to the Operation Game Thief toll-free hotline at (800) 792-4263. OGT is Texas’ wildlife crime-stoppers program, a function of Texas Parks and Wildlife Department’s Law Enforcement Division. OGT offers rewards of up to $1,000 for information leading to the arrest and conviction of individuals who violate game and fish laws.

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