National Park

National Park Service makes ‘unfortunate’ discovery at Southwest Texas lake: Invasive new mussel

The quagga mussel – a more harmful close relative of the zebra mussel that has already invaded 33 state lakes – has been detected in Texas for the first time.

The Texas Department of Parks and Wildlife said quagga mussel larvae have been discovered by National Park Service personnel on four occasions at Amistad International Reservoir. The lake is located near Del Rio and straddles the US-Mexico border.

Although no juvenile or adult mussels were located – only larvae – TPWD said now was the time to prevent the spread and development of a fully established population.

Zebra mussels are known to damage boats, injure aquatic life and clog pipes, but TPWD said quagga mussels are more harmful.

“This detection of invasive quagga mussels is a very unfortunate first for Texas,” Monica McGarrity, TPWD’s senior aquatic invasive species scientist, said in a news release. “Quagga mussels can inhabit greater depths and are also able to settle on soft substrates like mud or sand in addition to hard surfaces like rock or infrastructure – unlike zebra mussels – meaning that they can colonize a larger part of the lake.”

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“Quagga mussels are very prolific and can form larger populations which can have greater effects on the lake ecosystem as a whole, especially in deep lakes.”

It is also the first discovery of an invasive mussel species in the Rio Grande basin, TPWD said.

NPS routinely inspects the shores and docks of Lake Amistad for invasive mussels, even using mussel detection dogs, according to TPWD.

McGarrity added that lakes with zebra mussels are already threatened by the introduction of quagga mussels.

So far in the San Antonio area, zebra mussels have infested Buchanan, Canyon, Inks, Lyndon B. Johnson, Marble Falls, Medina and Placid Lakes. Zebra mussels have also been detected at Dunlap and McQueeney lakes.

Boaters can help stop the spread by clearing debris from their boats, draining water and letting gear dry.

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According to, boaters could face a $500 fine for transporting or possessing invasive mussels if they fail to clean, drain and dry their boats.

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