Three years after the discovery that zebra mussels had established themselves in Lake Texoma, the destructive invasive species has been confirmed in Lake Ray Roberts north of Denton.
This is only the second lake in Texas found to have zebra mussels, and the first in the Trinity River basin.
“Unfortunately, from an environmental and economic standpoint, this is very bad news,” says Texas Parks and Wildlife Department Executive Director Carter Smith.
“For a host of reasons the implications of this discovery are substantial to Texas waters and their future use and management. We intend to continue working with our partners to do everything reasonably possible to try and prevent the further spread of this harmful invasive species.”
Smith emphasized that the discovery underscores the importance of boaters helping to prevent the spread of zebra mussels, which can be unknowingly spread when boats and trailers are moved from lake to lake. TPWD and a coalition of partners has a public education campaign underway in North Texas encouraging lake users to clean, drain and dry their boats, trailers and gear. An instructional video and other tips on how to prevent the spread are available here.
Originally from the Balkans, Poland and the former Soviet Union, zebra mussels found their way to the Americas in the 1980s via ballast water of a ship. The small invaders were first found in 1988 in Lake St. Clair, Mich., and are currently known to have infested 29 states and more than 600 lakes or reservoirs in the United States.
Zebra mussels can have economic and recreational impacts in Texas reservoirs. They can clog public-water intake pipes, harm boats and motors left in infested waters by covering boat hulls and clogging water-cooling systems, annoy boat-dock owners by completely covering anything left under water and can make water recreation hazardous because of their razor-sharp edges.
From the environmental perspective, zebra mussels are filter feeders, which mean they compete with baitfish such as shad for available forage. Any impact on baitfish in turn can affect their predators — game fish such as bass, striped bass and catfish. Zebra mussels are also very harmful to native mussel populations because they will colonize on their shells and essentially suffocate them.
The latest discovery came following the DNA analysis of water samples collected from 14 North Texas reservoirs. While 12 of the samples proved negative, zebra mussel DNA was confirmed in the Lake Ray Roberts and Lake Texoma samples. The Texoma results were expected, but the Ray Roberts results were very concerning.
Following receipt of those results, TPWD fisheries biologists conducted a survey of the lake and confirmed the presence of small zebra mussels in several different locations on the lake and immediately below the dam.
“This is the first confirmed reservoir on the Trinity River Basin to have an established population of zebra mussels,” explained Brian VanZee, TPWD’s regional Inland Fisheries director. “The ones that have been found are only 1/8 to ¼ of an inch in size, so that means they were likely spawned earlier this year.”
TPWD does not know exactly when or how the zebra mussels managed to reach Lake Ray Roberts, a 29,350-acre impoundment that sees heavy recreational use.
“More than likely, it was a boat that operated in Lake Texoma or some other lake infested with zebra mussels and then was used in Lake Ray Roberts without first being cleaned, drained and dried,” says Gary Saul, TPWD Inland Fisheries Division Director. “In reality, we’ll probably never know.”
In the late summer of 2010 TPWD tried without success to chemically eradicate zebra mussels in a creek which feeds into the Trinity River system in North Texas. Unfortunately, no magic bullet has been found that will eliminate the bivalves once they have established themselves in a body of water.
However, the spread of zebra mussels can be slowed by making sure that boats that operate in zebra mussel-infested waters are not used in any other body of water until they have been cleaned, drained and dried. In addition, TPWD has recently adopted rules regarding the transfer of zebra mussel larvae in water from Lake Texoma and Lavon. To comply with those rules, boaters and anglers need to drain all water from their boats (including live wells) before leaving those lakes.
For two years, TPWD and a coalition of partners have been reaching out to boaters in North Texas to help educate them about the importance of taking action to slow the spread of zebra mussels. These partners include: North Texas Municipal Water District, Tarrant Regional Water District, Trinity River Authority, City of Dallas Water Utilities Department, Sabine River Authority, Canadian River Municipal Water Authority, San Jacinto River Authority, Angelina and Neches River Authority, Brazos River Authority and Lady Bird Johnson Wildflower Center.
Saul said TPWD will be looking at expanding current regulations dealing with clean, drain and dry rules to prevent the transfer of zebra mussel larvae to other lakes.
“With this somber news, I hope Texas boaters will always remember to “Clean, Drain, Dry” their boats, trailers and gear because all it takes is one instance of not properly cleaning to introduce this highly invasive and unwelcome species to a water body in Texas,” Smith said.