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Monitoring Finds Quagga Mussel Larvae In Lake Powell, Unclear If Population Established
Posted on Friday, November 09, 2012 (PST)

Recent monitoring samples from southern Utah’s Lake Powell have revealed evidence of microscopic quagga mussel larvae and the National Park Service has accelerated laboratory and field efforts to identify the source, Glen Canyon National Recreation Area Superintendent Todd Brindle said in a Nov. 1 press release.

Quagga mussel larvae and DNA were found in separate water samples collected near Antelope Point and Glen Canyon Dam. The northern Arizona dam stalls the Colorado River to create Lake Powell.

"We don't know yet if there is a population trying to establish in the lake," said Brindle. "The DNA can last after the organism is dead, so there is a possibility that it could have washed off boats that had been in other infested waters."

Quagga mussels are an invasive species, having been introduced from eastern Europe to the United States. The species first known to have created a niche in the Great Lakes in the late 1980s.

The first sighting of quagga mussels outside the Great Lakes basin was made in the Mississippi River between St. Louis, Missouri and Alton, Illinois in 1995. In January 2007, populations of quagga mussels were discovered in Lake Mead near Boulder City, Nev., and in the southwest’s Lake Havasu and Lake Mohave on the California/Arizona border. By late 2007 and early 2008, quagga mussels were discovered in 15 southern California reservoirs.

Quagga mussel larvae, called veligers, were identified from six Colorado River reservoirs about that same time, including Lake Powell.

“Everyone was waiting for the adults to show up but nothing happened,” said Stephen Phillips, senior program manager for the Pacific States Marine Fisheries Commission’s Aquatic Invasive Species Prevention Program.

Aquatic nuisance or invasive species are nonindigenous species that threaten the diversity or abundance of native species or the ecological stability of infested waters, or commercial, agricultural, aquacultural, or recreational activities dependent on such waters. The PSMFC supports regionwide projects that are conducted by agencies and universities, including the fish and game agencies from the PSMFC five member states (Idaho, California, Washington, Oregon, and Alaska) and is a regional coordinator on invasive species issues.

The Pacific Northwest has so far avoided at quagga mussel invasion. A Powell infestation, if it were to happen, could bring that invasion one step closer.

“This is scarier,” Phillips said of the prospect of a quagga population becoming established in Lake Powell. The reservoir and river running down through the Glen Canyon National Recreation Area are popular among boaters and rafters of all types. Many may originate from and return to the Northwest.

“All you can do is sit back and wait and hope” that the veliger DNA samples found in Lake Powell were indeed dead material washed off boats that had become tainted elsewhere, Phillips said.

NPS aquatic ecologist Mark Anderson provided additional details on the sampling results.

"The bodies of four larval mussels were found in four different samples near the Glen Canyon Dam. The sampling process kills mussel larvae so it is not known if any of them were alive in the lake," Anderson said. "One of them had a broken shell, suggesting that it was dead when it was collected."

Anderson explained that testing occurs using two separate methods: DNA and microscopy. The DNA method is more sensitive and potentially detects the presence earlier, but can be less accurate. Detection using microscopes is more accurate but requires an organism or piece of organism that is large enough to be visible in the microscope. Samples are taken using both methods at multiple sites around Lake Powell.

Brindle remains hopeful that the monitoring results are not evidence of an established population of mussels. If it is an early detection, the mussels may not establish and grow into adults, said Brindle.

"Scientists are not sure why but many western waters have shown similar findings and then never developed a noticeable population, such as at Lake Granby, Lake Pueblo, Electric Lake, Red Fleet, Navajo Lake, Grand, Shadow Mountain, Willow Creek, and even Lake Powell in 2007."

In the meantime, monitoring and testing by the NPS will continue.

"It is possible that these results will not be duplicated and a population of quagga mussels is not developing," said Anderson. In addition to the water sampling, NPS divers and underwater remote operated vessels will be used to search for adult mussels.

"However, if test results continue to show positive for DNA or if there are adult mussels visible, it could indicate that a population is starting," Anderson said.

If there is a population of mussels, Brindle said he is committed to working with all agencies and partners to determine the extent of the population and investigate and implement strategies for control. Depending on the extent of an early population, removing, wrapping or burying the mussel colony might be effective in preventing additional reproduction.

"We will continue the boat inspections that are currently in place," Anderson said. "Prevention is still the most effective way to fight invasive species. Continue to clean, drain, and dry your boat and equipment after every use."

Additional monitoring information and updates are posted on the Glen Canyon National Recreation Area webpage at www.nps.gov/glca/parknews/musselupdate.htm.

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