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Last updated on April 19, 2014 at 1:20 EDT

Mollusks Pose a Threat to California

June 4, 2008

Central California lakes and waterways are being threatened by tiny mollusk invaders that pose as hitchhikers.

Because quagga and zebra mussels are spread primarily through human-related activities, the Department of Fish and Game is asking for cooperation from boaters to prevent these destructive species from gaining a foothold in the San Joaquin Valley.

Many other areas of the state have been on high alert since last fall, when quagga mussels were discovered in numerous places along the Colorado River drainage, including Lake Mead, Lake Havasu and several San Diego-area reservoirs. Closer to home, zebra mussels were found inhabiting San Justo Reservoir outside Hollister in January.

Although these close cousins, which belong to the same family of shellfish, have yet to turn up in the Valley, their history suggests it’s only a matter of time.

“Right now there’s not really anything keeping people from coming up here and spreading these mussels,” said Mark Watson, the quagga/zebra mussel biologist for DFG Region 4, which is headquartered in Fresno. “People need to be educated.”

Once established, fast-reproducing quagga and zebra mussels can destroy a lake’s ecology by overwhelming vital elements of the food chain. They also can clog waterway infrastructure and damage boats.

Quagga and zebra mussels are typically about the size of a fingernail but can grow up to 2 inches in diameter. After attaching to hard surfaces, including metal, glass, plastic and wood, they feed themselves by consuming microscopic plants and animals from the water. Each adult mussel can filter up to one liter of water per day.

“They filter out all the food, and the native fish don’t have anything left to eat,” Watson said. “It basically changes the whole ecosystem.”

These invaders colonize on hulls, engines and steering components of boats and other watercraft. Reproducing rapidly, they also can attach themselves to piers, pipes and fish screens, blocking water intake and hampering municipal water supplies, irrigation systems and power plants.

The potential economic impacts are staggering.

“The consequences can be very severe,” said Steve Haugen, watermaster of the Kings River Water Association. “Once they get here, it’s management of them — not elimination. You have to live with them.”

Quagga and zebra mussels are native to Russia and the Ukraine. Biologists theorize that they came to the U.S. in the mid-1980s on cargo ships bound for the Great Lakes.

Zebra mussels were first detected in Lake St. Clair in 1988. A year later, quagga mussels were found in the same area. By the late 1990s, both species had spread to 23 states and two Canadian provinces.

Once these invasive mussels started turning up in California, alarm bells began to sound.

All vessels launching at Lake Tahoe face mandatory inspections, and owners who refuse are subject to a $5,000 fine. Officials in Santa Clara, San Luis Obispo and Lake counties also have instituted mandatory inspections — with boat owners in Santa Clara County being charged a $7 inspection fee. Last week, the East Bay Regional Park District banned all out-of-state boats from its four Bay Area reservoirs.

So far, the response throughout the central San Joaquin Valley has been noticeably less urgent. Recreation and water officials are mainly relying on public education to get the word out.

Calvin Foster, area manager for the U.S. Army Corps of Engineers, which manages recreation on several area reservoirs, said his agency is in the discussion and planning stages with the DFG.

“We don’t have any room in our budget to just go out and inspect boats,” Foster said. “But we’ll support those activities, for sure.”

At Millerton Lake, supervising ranger Lt. Gideon Coyle said the Department of Water Resources recently tested for quagga and zebra mussels but he had not heard the results.

Even though he hasn’t received any directives on how to deal with mussels, Coyle said he has handed out fliers and discussed the issue with boat owners. He described current awareness levels at Millerton Lake as “very low.”

“Out of 10 boaters I talk to about these mussels, maybe one in 10 knows what they are,” Coyle said. “Most people go, ‘What are you talking about? What’s a quagga mussel?’ “

Watson, the DFG biologist, said the best way to keep quagga and zebra mussels from spreading is through proper care by boat owners.

Vessels must be thoroughly washed and dried upon leaving the water, including bilge pumps, live wells and outboard unit, and should sit for at least five days between trips to different freshwater lakes.

Why so long? Quagga and zebra mussels can survive out of water for up to a week.

“Keep your boat clean and dry before you launch it,” Watson said. “That’s the best advice I can give.”