 An Oregon State University map shows the level of quagga and zebra mussel risk across the United States. Invasive quagga and zebra mussels appear to be steadily making their way into new areas of California, with Southern California officials reporting new finds in previously unaffected reservoirs. {sidebar id=48}
On Dec. 24, the City of San Diego's Water Department reported that quagga mussels were found attached to dock and work floats in Miramar Reservoir.
The discovery of the large population of quaggas is the first in any city reservoir in California, the City of San Diego reported. Quagga velifers – or larvae – have been found in San Diego's Murray, Lower Otay and San Vincente reservoirs as well.
In the coming weeks, the City of San Diego will increase its inspections of watercraft used by the public at Miramar, the city reported.
Quaggas and their cousins, the zebra mussel, are both extremely damaging to waterways, changing the ecosystem, affecting water quality and causing damage to water systems, officials report.
The invasive mussels, which originated in Ukraine, can spread rapidly, with watercraft – both commercial and recreational – their main mode of transport, according to the California Department of Fish and Game.
The aquatic hitchhikers, which can be microscopic in size during the larval stage, can even travel in bait buckets, on natives clams mussels – even on larval dragonflies, according to researchers.
They also attach to, and weigh down, native freshwater clams and mussels, crayfish and even large aquatic insects like larval dragonflies. When they attach to native clams and mussels, the researchers say, these invaded compete directly for food.
Fish and Game reported that the quagga mussel was first discovered in California in January. The state reported that the mussel poses “significant environmental, recreational and economic impacts” for California once they become established.
Such is the case in the Great Lakes, where the quagga mussel first appeared in 1989, the US Geological Survey reported. By 1995, the mussels had spread to the Mississippi River, between St. Louis, Miss., and Alton, Ill.
Fish and Game reported that the mussels covered everything from boat engines to water transport facilities, disrupted the lakes' natural food chain, released toxins affecting other species. “Spread of the quagga could result in millions of dollars in damage to water transport facilities,” Fish and Game reported.
The West Coast discovery “was an extremely large leap in their range and cause for much concern to limited water supplies and endangered fishes in the southwestern US,” according to a report from the US Geological Survey.
Since the mussels arrived on the West Coast earlier this year, researchers report they've been found in Nevada and Arizona as well as California, where they've spread not only to San Diego County but also to Riverside.
County emphasizes prevention
For Lake County, the mussels haven't yet been found in Clear Lake, which was tested for signs of quaggas and zebras over the summer, as Lake County News reported.
On May 22 the Board of Supervisors – sitting as the Board of Directors of Lake County Watershed Protection District – authorized the Water Resources Division to spend water quality improvement funds from the county's Marketing and Economic Development budget to test the 10 most used launch sites on Clear Lake for quaggas.
On June 5, the board also approved drafting a letter to state and federal legislators, surrounding counties, the California State Association of Counties and the Regional Council of Rural Counties asking for help to fight the mussel.
At the board's following meeting on June 12 members voted unanimously to pass a resolution declaring the need for emergency action to protect Clear Lake from the invasive species.
Water Resources Deputy Director Pam Francis told Lake County News in a summer interview that the county plans to continue testing on a monthly basis through the summer.
The county thus far is emphasizing prevention, which is the least expensive option, Francis told Lake County News over the summer.
As part of the prevention campaign, the county has taken a public education effort, from signs along area highways, to brochures, letters to boat owners and residents with buoy, dock or pier leases, Francis stated. The county also encourages anyone putting a boat in the water to making sure it has been allowed to dry completely – inside and out – before launching in area lakes.
In October, Fish and Game rolled out a new K-9 Program that will train as many as 24 dogs to serve the agency statewide. Among their skills will be detecting quagga mussels, as well as detecting ammunition and hidden firearms, and searching for missing persons and suspects.
Game Warden Lynette Shimek, who serves Lake County, was assigned a dog named Kyrie.
“A dog’s scent ability has been estimated to be up to a million times stronger than humans,” said Shimek. “When dealing with something as small as quagga mussels or waterfowl hidden in the trunk of a vehicle, a dog will let us know quickly that something is not right.”
New research points to seriousness of threat
On Dec. 3 Oregon State University, Corvallis, released the results of a new risk assessment study along with a new map outlining the risk of zebra and quagga mussel invasion in the United States.
Oregon State reported that, based on its assessment, the Great Plains and American Southwest could be next in line for invasion.
Researchers believe that the spread of quagga and zebra mussels may be controlled by calcium levels in streams and lakes, which puts the Plains states and the Southwest in a high-risk ecoregion.
“If there isn’t enough calcium in the water, you probably aren’t going to get zebra or quagga mussels,” said Thom Whittier, a faculty research assistant in the Department of Fisheries and Wildlife at Oregon State University and lead author on the study. “If you have sufficient calcium, it doesn’t necessarily mean you have a problem. These mussels also need colonies in still water to maintain populations over the long term. In rivers, this means there needs to be an invaded upstream lake, canal or reservoir to supply new larvae.”
Whittier said a female zebra mussel may produce a million eggs a year, and can be hard to get rid of once established.
Quaggas, according to Oregon State, appear to be overcoming zebra mussels, especially in areas like the Great Lakes.
Scientists emphasize the importance of prevention, cleaning equipment to help prevent the mussels spreading.
“As scientists, when we do our research, we scrub and disinfect our boots, our nets and all of our equipment,” said Alan Herlihy, an Oregon State research professor in the Department of Fisheries and Wildlife. “We take this threat seriously.”
E-mail Elizabeth Larson at
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