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Destructive quagga mussels found in South Texas reservoir

closeup of a quagga mussel on a lake bottom
National Marine Sanctuaries, Public domain, via Wikimedia Commons

From Texas Standard:

By now, you've probably at least heard of zebra mussels -- the tiny, invasive mollusks that have infested Texas lakes and rivers over the past decade or so. The mussels are a big problem, since there's no effective way to get rid of them, and they can do major damage by clinging in clusters to underwater infrastructure.

Last week, the Texas Parks and Wildlife Department (TPWD) announced that a close cousin of the zebra mussel has also been found in Texas -- the quagga mussel. TPWD staff found quagga mussel larvae in Amistad Reservoir, 20 miles northwest of Del Rio along the border.

Monica McGarrity, a senior scientist for aquatic invasive species at the Texas Parks and Wildlife department, spoke to Texas Standard about the mussels’ potential impacts in Texas waterways. Listen to the interview above or read the transcript below.

This transcript has been edited lightly for clarity:

Texas Standard: What do quagga mussels look like? 

Monica McGarrity: The quagga mussels are very similar in appearance to zebra mussels. They’re small triangular mussels that grow up to about 1.5 inches. Also, they attach to hard surfaces like the zebra mussels — although they can also settle on soft sediments unlike the zebra mussels. They also have striping on their shells that may be a little bit less pronounced because of the ridge running down the shell the zebra mussels have. Their shells are paler in color towards the hinge and are pointed into the shell.

Last week, your department announced that for the first time, quagga mussels had been found in a Texas body of water. Where were they found?

The mussels were found in Lake Amistad in the Del Rio area in the Rio Grande basin along the border with Mexico.

Are there any clues as to how they got to this particular body of water?

Quagga mussels are native to Eurasia, same as the zebra mussels, and they came into the Great Lakes on boats. And then they've been transported overland to some of the western states nearby; Arizona, Nevada, Utah, California. And so they move over land on boats, and that's how they would have been introduced into Lake Amistad. That’s why it’s really important for folks to clean, drain and dry their boats.  

Zebra mussels can cause costly damage to things like pipes and piers. Do quagga mussels do the same sort of damage? 

Quagga mussels do cause the same sort of damage. They have an advantage over the zebra mussels in a variety of ways. Quagga mussels are able to inhabit greater depths and colonize more of the lake and they have greater energetic efficiency. So they're able to become more prolific and can occur at even higher densities than zebra mussels.

So, in other words, they could take care of our zebra mussel problem, but introduce a whole new problem for Texas?

Right. In some lakes where they're both present, they can largely replace the zebra mussels in about nine years, but they don't do it completely. So we still have the risk if a lake ends up with both species, that both could be causing problems and getting transported to other lakes. But quagga mussels do become the dominant species and the one that's most problematic.

Once they're there, is there anything you can do about it? 

Unfortunately, there are currently no good ways to eradicate zebra or quagga mussels from any of our large Texas lakes. Treatments are limited to localized areas. What can be done are efforts to mitigate their impacts on infrastructure, so some will have chemical injection systems or things to reduce their impacts on the pipelines and on water infrastructure itself.

What can we do to keep them from spreading? 

Like I said, zebra and quagga mussels are transported on boats. So it's really critical for people to clean, drain and dry their boats before they leave a water body. Remove any mud or vegetation that could have mussels attached, drain all of the water out of the boat and then let everything dry completely. If a boat has been stored in the water, it may actually have mussels attached to it, so that boat needs to be decontaminated completely before it's moved to another water body.

So if you've got a boat, should you just assume that you need to get that boat out of the water and dry it out now?

Keeping a boat out of the water or up on a lift definitely does reduce the risk of mussels attaching to it — which can damage the boat. If there is a lake that has invasive mussels, I would certainly recommend taking those steps.