Zebra mussel DNA detected in five North Texas lakes

The latest tests and monitoring looking for zebra mussels in North Texas lakes yielded mixed results.

While zebra mussel DNA was detected in Lakes Texoma, Ray Roberts, Lewisville, Bridgeport and Bob Sandlin, no zebra mussel populations could be confirmed by physical inspection in Lewisville, Bridgeport and Bob Sandlin.

“We know a zebra mussel population exists in Lakes Texoma and Ray Roberts,” said Brian Van Zee, Texas Parks and Wildlife Department’s regional director of Inland Fisheries. “Our district biologists have looked for evidence of zebra mussel populations in Lakes Lewisville, Bridgeport and Bob Sandlin since receiving the DNA test results, but none were found. This is not uncommon, as the test is very sensitive and has been known to show positive results in several lakes where zebra mussels have never been documented. It’s possible that the results are showing us that boat owners may be moving contaminated boats to these lakes, but that viable populations haven’t developed.”

Dr. Robert McMahon, professor emeritus of Biology at the University of Texas at Arlington, has been monitoring 14 North Texas reservoirs for the presence of zebra mussels using three techniques. One technique looks for zebra mussel DNA in the water, another uses a microscope to look for zebra mussel larvae (veligers) in the water, and the third uses a submerged monitor to look for newly settled juvenile mussels.

“The DNA test results for Lakes Bridgeport and Bob Sandlin were very weak positives,” McMahon said. “The results for Bob Sandlin were so weak as to almost be below the limit of detection.”

“These results are a reminder that boaters need to take the necessary precautions before moving a boat from one lake to another,” Mr. Van Zee said. “TPWD will continue monitoring these lakes for the presence of zebra mussels and doing everything it can to encourage boaters and anglers to clean, drain and dry their boats before moving them to another lake. We encourage boaters and anglers to visit http://www.texasinvasives.org/ to learn more about how they can help protect the waters they enjoy.”

Texas Parks and Wildlife Department is asking anyone transporting a vessel that has been used on Lakes Texoma, Ray Roberts, Lavon or Lewisville to another water body to take the following precautions. (1) Clean all vegetation, mud, algae and other debris from the boat and trailer. (2) Drain all water from the motor as well as the live-well, bilge, bait buckets and any other compartments or systems that hold water. (3) Dry the vessel and associated equipment for a week to 10 days during the months of May through October or for 15 to 20 days from November through April. These drying times are approximations, and conditions such as cooler air temperatures, higher humidity and whether or not the vessel is kept in dry storage should be considered. These are the easiest preventive measures that boat owners can do to help prevent the spread of zebra mussels.

However, boats and other vessels that have been kept on a lake known to be infested with zebra mussels for an extended period of time may require additional cleaning procedures. Power-washing with water at least 140 degrees Fahrenheit and flushing the motor, bilges, live-wells and other raw water intake systems with 140-degree water will kill zebra mussels. To be effective the water coming out of the flushed systems needs to reach 140 degrees to ensure the entire system was exposed to water hot enough to kill the mussels.

If it is not possible to clean the internal systems or compartments using 140-degree water, the use of either straight vinegar or a chlorine bleach and water solution (one-half ounce bleach to one gallon water) can be effective at killing zebra mussels as long as the mixture is kept in contact with the mussels for a sufficient amount of time (20 to 30 minutes). Clean water should be used to flush the chemicals and dead mussels from the boat following treatment. Boat owners should check with their manufacturer to be sure using these chemicals will not void their warranty.

Large vessels with complex water intake systems such as those used for cooling the engine, air conditioning or personal sanitation may require decontamination by a boat mechanic or marina.

A video showing how to decontaminate a boat can be viewed at http://www.100thmeridian.org.

Under the Texas Parks and Wildlife Department and Texas Penal Codes, possession or transporting of zebra mussels in Texas is a Class C misdemeanor punishable by a fine of not less than $25 nor more than $500 for the first offense. However, repeat offenses can be elevated to a Class B misdemeanor which is punishable by a fine of up to $2,000, jail time up to 180 days, or both. If an individual is convicted a third time for this same offense it becomes a Class A misdemeanor which is a fine of up to $4,000, jail time not to exceed one year, or both.