Biologists in Texas and other states have been on the lookout for zebra mussels, an invasive species of shellfish that can wreck an area's ecosystem, the Associated Press reported.

Studying around three dozen Texas lakes, researchers lower microphone-like devices into the water to gather samples and see if the zebra mussel is lurking in the depths.

The striped shellfish are about the size of a fingernail and have been spreading across the central and eastern portions of the U.S.

"More or less, once they attach, that's it," said Monica McGarrity, an aquatic invasive species biologist for the Texas Parks and Wildlife Department, as quoted by the AP. "Then they filter, filter, filter. All of the stuff I'm catching here. They filter away and that's how they make the water more clear. They're eating all the nutrients that the fish eat."

Just one female zebra mussel can produce a million eggs in a year. The shellfish latch on to almost anything, multiplying on everything from the undersides of docks to old soda cans. Because they filter the water, extra sunlight can come through to nourish "undesirable" plants, which interrupt the natural food chain.

"Once they're in, it doesn't take long," said Robert McMahon, a University of Texas at Arlington biology professor who has studied zebra mussels for years. "I don't want to be saying it's doomsday. It's just they're economic and ecological pests. They plug up water works and that can cost millions."

Starting on July 1, the state Parks and Wildlife Commission began requiring people to drain, rinse and clean their vessels prior to leaving or approaching public water.

Zebra mussels are native to Ukraine and are believed to have come to the U.S. in the late 1980s, hitching a ride on a cargo vessel near Detroit.

One of the invasive shellfish was discovered in Lake Cornelia, Iowa, according to the Department of Natural Resources. Larval specimens of zebra mussels were also found in the water, the Mason City Globe Gazette reported.

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