Zebra mussel larvae found in Lake Bridgeport

Posted Thursday, Jun. 27, 2013  comments  Print Reprints
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Slowing down zebra mussels • Clean all vegetation, mud, algae and other debris from the boat and trailer before leaving the lake. • Drain all water from the motor as well as the live well, bilge, bait buckets and any other compartments or systems that hold water before leaving the lake. • Dry the vessel and associated equipment for a minimum of seven to 10 days during the months of May through October or for 15 to 20 days from November through April. Drying times are approximate, and conditions such as lower air temperatures, higher humidity and whether the vessel is kept in dry storage should be considered. For more information, go to www.texasinvasives.org. Source: Texas Parks and Wildlife Department

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For years, officials have feared zebra mussels would eventually find a way to jump to the West Fork of the Trinity River.

Now, it appears that may have happened.

Just days after a zebra mussel was confirmed to be in Lewisville Lake, which is on the Elm Fork of the Trinity River, zebra mussel larvae, known as veligers, have been found on the West Fork in Lake Bridgeport.

A colony on Lake Bridgeport would be the first on the West Fork and also pose a risk to Eagle Mountain Lake and Lake Worth, which are both downstream. The fear is zebra mussels could eventually spread downstream while also be transferred to other river basins by boaters.

“If zebra mussels are able to establish a population in Lake Bridgeport, then Eagle Mountain Lake and Lake Worth will be highly susceptible to infestation,” said Christopher Churchill, project chief of the zebra mussel monitoring program with the U.S. Geological Service.

The good news is zebra mussel larvae has only been found on one spot on Lake Bridgeport, said Robert McMahon, professor emeritus of biology with the University of Texas At Arlington and who tested the samples confirming the larvae.

“Since there is no upstream reproducing population above Lake Bridgeport, that means they had to come from somewhere in the lake,” McMahon said

At the current levels, there aren’t enough larvae traveling downstream to infest Eagle Mountain Lake. But that could change if they get established in Lake Bridgeport, where the high calcium levels and water temperatures appear to be favorable for the mussels.

“Only time will tell,” said McMahon, who was taking samples on Lake Texoma on Thursday. “As you can imagine, it's not a good sign.”

The mussels can clog public-water intake pipes, harm boats and motors that are in infested waters. They can attach themselves to boat hulls and clog water-cooling systems. They can make beaches and shorelines off-limits because of the razor-sharp edges to their shells.

Zebra mussels also push native species out of lakes.

“Any impact on baitfish in turn can affect their predators — game fish such as bass, striped bass and catfish,” said a Texas Parks and Wildlife press release. “Zebra mussels are also very harmful to native mussel populations because they will colonize on their shells and essentially suffocate them.”

‘They haven’t gone away’

When zebra mussels first arrived in the U.S., there was a thought that they couldn’t survive temperatures above 82.4 degrees. But the mussels have survived in temperatures as high as 86 degrees in Lake Texoma.

The zebra mussel population has dropped at Lake Texoma since its peak several years ago but that may be due to the drought. In 2011 and 2012, the lake level dropped at Texoma, exposing many of the mussels to air and killing them. But McMahon said there are plenty of veligers in Texoma’s water.

“They’re still here,” McMahon said. “They haven’t gone away.”

The Tarrant Regional Water District, which operates Lake Bridgeport and Eagle Mountain Lake, is already making preparations for zebra mussels arrival, said David Marshall, the water district’s engineering services director. Marshall said it was “impossible” to prevent the larvae from traveling downstream from Lake Bridgeport to Eagle Mountain, comparing it to zebra mussel larvae easily moving from Lake Ray Roberts downstream to Lewisville Lake.

“We’ve been planning long-term for the fact that our lakes are eventually going to have a viable population of zebra mussels,” Marshall said. “They are virtually impossible to stop if you have any boat traffic that migrates from one reservoir to another. They are some of the most tenacious little beasts you can meet.”

Tarrant Regional plans to spend about $11 million to retrofit pumps that are currently cooled by lake water and they’re also looking at any other piece of equipment that could be impacted by mussels. The water district has also planned for zebra mussels in the $2.3 billion integrated pipeline that will start bringing more water from Richland-Chambers reservoir in 2018 and Cedar Creek Lake about two years later.

While an actual mussel hasn’t been found in Lake Bridgeport, officials fear there is a zebra mussel population since zebra mussel DNA was found in the fall of 2011 and 2012, and some veligers were detected this spring in plankton tows.

Testing will continue

The Tarrant Regional Water District, which operates Lake Bridgeport, collected samples on June 6 and McMahon confirmed the larvae’s presence on June 17.

But Parks and Wildlife officials caution that no juvenile or adult zebra mussels have been found in Lake Bridgeport, which would suggest a self-sustaining population.

“Given the high mortality rates of zebra mussel veligers it’s not a guarantee that a population exists but given these results and the DNA results from the past two years it is likely that the lake is infested,” the press release said

Routine monitoring by Tarrant Regional, UTA and Texas Parks and Wildlife Department will continue to determine if there is any growth or spread of the mussels. Both Eagle Mountain and Lake Worth will continue to be monitored.

Officials have feared the spread of zebra mussels since they were first found in Lake Texoma in 2009. Since zebra mussels can be spread by transporting infested boats from lake to another, boats need to be cleaned, drained and dried. Parks and Wildlife has already imposed rules regarding the transfer of zebra mussel larvae in water from lakes Texoma, Lavon, Ray Roberts and Lewisville. To comply with these rules, boaters and anglers need to drain all water from their boats (including live wells) before leaving those lakes, the press release said.

Parks and Wildlife has also tried to educate boaters to prevent the spread.

Zebra mussels originally came from the Balkans, Poland and the former Soviet Union. They made 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.

Bill Hanna, 817-390-7698 Twitter: @fwhanna

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