One of the country's worst invasive species continues to spread. The Utah Division of Wildlife Resources this week revealed that the Lake Powell reservoir between Utah and Arizona has been invaded by destructive quagga mussels, a large species of mollusk that reproduces rapidly, quickly crowds out native species and clogs pipes and other structures.

Quagga mussels first turned up in the Lake Erie in 1991 and have quickly spread to other parts of the country through boat ballasts. Many states have laws requiring boaters to decontaminate their vessels when moving from one body of water to another, but that has not been enough to stop the mussels' invasion. Many states have laws requiring boaters to decontaminate their vessels when moving from one body of water to another, but that has not been enough to stop the mussels' invasion.

Quagga mussels have been present in Lake Powell for some time, but this week the National Park Service revealed that the problem is much worse that previously suspected. Water levels in the Glen Canyon National Recreation Area have been lowered, revealing infestations that have until now been hidden.

"Thousands of adult quagga mussels have been found in various locations, such as canyon walls, Glen Canyon Dam, boats, and other underwater structures," spokeswoman Denise Shultz told National Parks Traveler. "The majority of mussels found are isolated adults, with additional groupings of small clusters. One adult mussel was found on the south canyon wall of Bullfrog Bay."

Although so far the mollusks in Lake Powell have not reached the peak mass seen in other locations, and no mass colonies have been found, officials said they fear that they could reproduce and spread quickly, as one adult quagga mussel can spread up to one million larvae in just a year. "I can picture what Lake Powell is going to look like and it isn’t pleasant," Greg Sheehan, director of the Utah Division of Wildlife Resources, told the Salt Lake City Tribune. "Every beautiful sandstone outcropping will be encrusted with snails. The days of running barefoot on the beaches will be gone." The mussels have strong, sharp shells which in other invasion sites have littered beaches, endangering peoples' feet.

In a statement, park superintendent Todd Brindle said the quagga mussels should not yet have an impact on park visitors. "Park staff, partners, and the public have worked hard to keep Lake Powell mussel free for the last ten years. It's very disappointing that mussels are in the lake, but most visitors will not notice them. The important thing now is to keep them from being transported to other lakes and rivers."

Officials are reminding boaters of necessary precautions to prevent the spread of quagga mussels, which at young ages can be the size of a pea or smaller and can be easy to miss if people aren't looking closely. Regulations require boaters to clean and drain their vehicles before leaving the vicinity of the lake; drying boats for a required amount of time before moving them to another body of water; or having them professionally decontaminated.

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