Las Vegas Sun

January 21, 2018

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Lake Mead mussels identified as quagga, not zebra

A newly discovered freshwater mussel at Lake Mead has been identified as the quagga mussel - not the zebra mussel, as first suspected - and that is just half of a double dose of bad news.

The other is that the mussel has spread. Agencies are finding the quagga mussel in areas away from the original discovery point at Hemenway Harbor, including in fish hatcheries fed by the same water line that serves Henderson.

The quagga and its cousin the zebra mussel, which have cost water agencies billions by fouling water-system lines in the Midwest, have also been found on Saddle Island - the site of intakes for the water pipelines serving Las Vegas, unincorporated Clark County and North Las Vegas.

Jon Sjoberg, supervising fisheries biologist with the state wildlife division, said both discoveries are bad news. The quagga mussel adapts to a wider variety of conditions than the zebra mussel. The zebra needs shallower water and a hard surface to attach itself, but the quagga can establish itself in deeper water and on silt and sand.

"It is a different species," he said. "These guys are like zebra mussels with an attitude in terms of what they will tolerate."

The basic effect of either species is the same, however: Both clog pipes and other aquatic infrastructure, can damage boats and can completely transform freshwater ecosystems by removing nutrients that would otherwise support other life.

But there is some good news. None of the mussels has been found at Willow Beach downstream from Hoover Dam on the Colorado River, potentially indicating that the mussel invasion is thus far limited to Lake Mead.

And Sjoberg said none of the mussels has been found at Temple Bar in the northern part of the lake, suggesting that the animal may be restricted to Boulder Basin in the south.

"So far, they're clean," he said of the other sites. "The immediate concern is how do we contain these things."

Federal, state and local agencies across the West are concerned that the mussels could spread to other locations, especially because Lake Mead is a central location for recreational boating. Boats are the suspected vector for introduction of the mussel to the lake and could transport the animal to other areas. Agencies and staff members from state and federal agencies are ramping up to - they hope - meet that challenge.

J.C. Davis, a spokesman for the Southern Nevada Water Authority, said it is not clear whether the mussels found at Saddle Island came through the water lines that bring water to Henderson.

The infected hatcheries are fed water through the 56-year-old pipeline built for the Basic Magnesium Inc. plant. They are not part of the same pipelines that supply most of Henderson and the rest of the urban area.

Davis said divers are scheduled to inspect those intakes in Lake Mead on Jan. 20.

"The implications of this showing up in Lake Mead and the Colorado River system are enormous," said Allen Biaggi, director of the Nevada Conservation and Natural Resources Department.

Quagga mussels were first discovered in the Great Lakes in 1989, a year after zebra mussels were identified.

Zebra and quagga mussels have caused billions of dollars of damage to water systems and have profoundly transformed freshwater ecologies in lakes and rivers, in many cases eliminating native species of fish and other mollusks.

The threat of invasion is especially critical to California, which relies on a network of inland canals and aqueducts to move water to thirsty urban users and agricultural producers.

Rick Soehren, water policy adviser in Sacramento for the California Water Resources Department, says water for agricultural and municipal needs, as well as to sustain the environment, could be disrupted if the mussels move west.

Soehren's department recently did a preliminary study on how the zebra mussel could affect the California State Water Project, a 700-mile network of canals and pipelines serving 23 million people and 755,000 acres of farmland. If the mussels get into the water project, which is just one of several such networks serving the state, the cost would be at least $70 million for new capital projects and $40 million annually in new maintenance costs.

The connected canals and pipelines would give the mussels a highway to colonize the Golden State.

Not that they need much of a road. Quagga and zebra mussels can move around readily on boats hauled from one water body to another. That is almost certainly how they were introduced to Lake Mead.

In Arizona, officials share the same concerns. Larry Riley, fisheries chief of the Arizona Game and Fish Department, said officials have been thinking about the possibility of an invasion by the mussels for years.

Riley said that one short-term goal will be to ensure that the mussels have not established colonies downstream from Lake Mead in lakes Mohave or Havasu.

Although officials from the National Park Service, which runs the Lake Mead National Recreation Area, have said it probably would not be possible to eradicate mussels now that they have established colonies in the lake, Riley said he wants to keep open the option of some kind of eradication program.

An experiment in a small lake in Virginia infested with zebra mussels seemed to show that treating the water with potassium salts eliminated them. Lake Mead, however, at 155,000 acres the largest artificial reservoir in the United States, could be a different story.

"Lake Mead is bigger than a 12-acre quarry," Sjoberg said. Nonetheless, "research is ongoing. There's always a hope that someone will find some sort of miracle cure."

Even if eradication is not possible, similar chemical treatments are probably going to be used to keep the mussel from colonizing water intakes and potential sewage outflows.

Biaggi, the Nevada conservation official, said that agency representatives plan to meet with their counterparts from across the West to discuss the mussel threat Jan. 31 in Las Vegas.

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