At the Border, Battling a Destructive Mussel Invader : Ecology: If fast-growing species enters lakes or streams, it soon can disable water systems by clogging pipes.


The latest stowaways slipped into California aboard a 44-foot yacht named Resolute. Clinging to its hull, they were spotted and quickly seized by a keen-eyed inspector at a border station in the Sierra town of Truckee.

It was yet another case of foreign invaders nabbed at the California border. For the fourth time in the past six months, an exotic species of mussel has been detected on vacationers’ yachts at border inspection stations.

This isn’t just any mussel; this is the most dreaded animal species in North America. If there were ever a foreign immigrant that justifiably invokes fear in California, it’s the zebra mussel, an innocuous-looking, black-and-white-striped mussel that is only slightly bigger than the tip of a thumb.


Nearly invincible, the mussel can cling to virtually any hard surface and is capable of reproducing so rapidly that it can clog pipelines and disable water systems within a few years of its arrival in a lake or stream.

The recent discoveries of zebra mussels at California’s border are reverberating throughout the state, since water engineers know they can threaten the security of the massive water systems that are the state’s lifeline.

In an area as dependent on the movement of water as California, zebra mussels can wreak havoc. The biggest fear is that they will--or perhaps already did--infiltrate the State Water Project and the federal Central Valley Project that supply cities, suburbs and farmers throughout California.

“Nothing equals the threat of zebra mussels to water systems and the freshwater ecosystems in California,” said Dan Peterson, chief of the state Department of Water Resources’ environmental assessment branch. “If it gets here, it will be a big problem. Or should I say when it gets here.”

The zebra mussel, alias Dreissena polymorpha, invokes such fear because its ranks can grow thousands-fold in just a year’s time. It has no natural predators, and there is virtually no known way to stop it from transforming a water system once it arrives.

“There is nothing you can do to kill zebra mussels that won’t also kill other organisms that are valuable to you, including people,” said Dave Culver, an Ohio State zoology professor who is studying the creature’s spread.

Native to an area of Russia near the Caspian Sea, the zebra mussel is a fairly new arrival in the United States. Yet it has already caused an ecological crisis in the Great Lakes, where water systems have been shut down in some areas and maintenance costs have skyrocketed.

Apparently traveling in the ballast water of ships originating in the former Soviet Union, the mussels were first discovered in Canada’s Lake St. Clair in 1988. Within a year, they had colonized virtually every solid object in western Lake Erie. Since then, they have swept through all the Great Lakes as well as the Mississippi, Ohio, Hudson, Illinois, Arkansas and Tennessee rivers, most likely transported on barges.

“I thought it would never get beyond the Great Lakes,” said Dave Garton, an Indiana University associate professor of biology who was the first to find zebra mussels in U.S. waters. “Boy, was I wrong.”

Each female mussel lays as many as 1 million eggs each year, and although only about 20,000 of those survive, the population can multiply with astounding speed.

“It’s mind-numbing when you stop to think about it,” Garton said. “I’ve never seen an organism so dominate a system in every way as this one has.”

To many researchers, it’s not a question of whether it will invade California lakes and streams; it’s a question of when. Culver gives it “a 100% chance” of eventually infesting the state.

“The whole water system for California is at risk,” he said. “It will be there . . . sooner or later.”

Some biologists, however, believe that the West will be somewhat protected, at least for awhile.

“The reason they spread so much in the East is from navigation. Barges have spread them everywhere, and you don’t have that in the West,” said Amy Benson, a fisheries biologist with the National Biological Service. “The Continental Divide is going to be a pretty good barrier for quite a while.”

Aquatic scientists worry that the recent discoveries at the California border are like the opening salvo from the infantry in a foreign invasion.

It is anybody’s guess how many, if any, might already have crossed into the state and are now swimming and breeding in California lakes.

The 44-foot yacht that brought a clump of the mussels to Truckee on June 13 was headed to Sausalito from the northern banks of Lake Michigan. It came a mere four days after another Michigan boat--this one a 27-foot cruiser from Muskegon--was stopped at the same inspection station carrying mussels on its motor housing. The first was found at an inspection station in Needles in 1993.

Two of the boats contained mussels that were still alive, and, as one aquatic biologist said, if a mussel can survive Needles, it can survive anything.

“If you snatch your boat out of the water and drive straight to California, there will be a high probability you have zebra mussels with you,” Garton said.

California inspectors now spend five to 10 minutes checking boats from states known to be home to the mussels. Vessels harboring mussels cannot be launched in California freshwater until they are declared clean by state Fish and Game wardens.

“There are a tremendous amount of boats being brought across into California every day,” said Bill Sandige of the state Department of Food and Agriculture. “The biggest risk is the snowbirds that come to California every fall or winter and who may pull their houseboat with them.”