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Lake Medina fully infested with zebra mussels

June 23, 2021 - 05:00
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Medina Lake is one of 27 lakes in Texas designated by the Texas Parks and Wildlife Department (TPWD) as being fully infested with zebra mussels.

Infested status means there is an established, reproducing population of zebra mussels in the lake.

That designation follows event sampling efforts revealing evidence that zebra mussels in Medina Lake are now fully established and reproducing and detection of a new infestation in Inks Lake.

According to a TPWD release, a sighting by a member of the public in February and subsequent surveys uncovered a total of three zebra mussels at multiple sites on Medina Lake, leading to an initial designation of the lake as positive for zebra mussels.

In late May, a lakefront landowner reported a larger mussel at their dock on the lake near Elm Cove and provided a specimen.

The Bandera County River Authority & Groundwater District followed up by conducting intensive shoreline and snorkeling surveys, locating numerous zebra mussels at sites near Echo Point and Elm Cove.

“The most recent discoveries, combined with the initial sightings in February, revealed numerous mussels of different sizes in multiple locations, indicating the presence of an established, reproducing population and Medina Lake is now designated as fully infested,” read a release from TPWD.

“Unfortunately, zebra mussels have now spread to 32 Texas lakes, with 27 fully infested, but there are far more lakes that still haven’t been invaded and are at risk,” said Brian Van Zee, TPWD

Inland Fisheries Regional Director.

Roughly the size of a fingernail and featuring dark striped shells, zebra mussels filter out algae needed by native species for food and incapacitate native mussels.

They attach to boats and anything left in the water, including anchors, and can survive for days out of water, often hiding in crevices where they may not be seen easily. Their larvae are microscopic and invisible to the naked eye and can be unknowingly transported in residual water in boats.

According to TPWD biologists, there is no effective way to eradicate zebra mussels once they have become established in a water body, and opportunities for rapid response are extremely rare, since by the time they are detected it is usually too late because they have begun to spread.

Zebra mussels also spread by downstream dispersal, but unfortunately nothing can be done to prevent this as their larvae are microscopic and free-floating in the water, according to TPWD biologists.

This is why introductions to new river basins such as the San Antonio River Basin is a concern, as it puts downstream water bodies at risk.

“As zebra mussels are continuing to spread westward and southward to new areas in Texas and as those lakes become fully infested, nearby lakes have an increased risk of being invaded and it is vital that boaters take steps to clean, drain, and dry boats to help slow the spread,” said Monica McGarrity, Senior Scientist for Aquatic Invasive Species.

“Boats owned or recently purchased that have been stored in the water must be decontaminated before moving them to another lake to prevent the spread of these highly invasive mussels,” she said.

TPWD is urging boaters to clean, drain and dry their boats and gear before traveling from lake to lake, remove plants, mud and debris, drain all the water from the boat and gear, and then open up compartments at home to allow everything to dry completely for at least a week.

The transport of aquatic invasive species is punishable with a fine of up to $500 per violation.

Additionally, anyone who spots zebra mussels on boats, trailers or equipment being moved is asked to immediately report the sighting to TPWD at 512-389-4848.