Zebra mussels, mitten crabs invade Northwest

By TAYLOR PITTMAN and KEVIN ANDERSON
Special to the Journal

For all the talk about alien' plants and animals invading Puget Sound and the waters of the Northwest, we are still in the midst of a silent crisis. What are non-native species? And why should we worry?

Native to Europe, the green crab was first collected in San Francisco Bay in 1989. It was found in Willapa Bay in 1997 and reported in British Columbia in 1999. The crab is very aggressive and, although small only 3-4 inches across the carapace it can eat up to 40 half-inch clams each day.

The ecological and economic costs associated with invasive species are very high. In 1990, Congress was driven to pass the Non-Indigenous Aquatic Nuisance Prevention and Control Act after the arrival of the tiny zebra mussel in the Great Lakes. This fingernail-sized creature is a native of the Caspian Sea region of central Asia and probably hitchhiked a ride in transoceanic ship ballast water. Since 1988, the mussels spread quickly and became established in many river systems east of the Mississippi River, including the Mississippi itself. In the 10 years since it arrived, the mussel has colonized on docks, boat hulls, commercial fishing nets, water intake pipes and valves, and on native clams and mussels. It costs local water utilities about $3 billion each year to clean up and prevent the zebra mussels from clogging fouled intake pipes to water treatment and power plants.

Chinese mitten crab

In 1992, a shrimper in the San Francisco Bay hauled up the first Chinese mitten crab. This species originates, as its name implies, from Asia. Since this first discovery, the mitten crab population has increased to epidemic proportions, clogging state water pumps and fish screens in the Sacramento River Delta with their seething multitudes.

But that's only part of the story. The mitten crabs live part of their lives in freshwater and like to burrow into levees, dikes and other shoreline features threatening to collapse them. The cost for fixing the problem is astronomical.

As a consequence of the 1990 Act, the Aquatic Nuisance Species Task Force was formed, co-chaired by the U.S. Fish and Wildlife Service and the National Oceanic and Atmospheric Administration. This national task force is establishing guidelines and coordinating national efforts to prevent the introduction and spread of non-indigenous species in U.S. waters.

How do they come here?

There are many ways nonnative species are carried into alien waters, but the primary means is through ballast water. The zebra mussel, for example, arrived in the ballast water of cargo ships doing trade in the Great Lakes.

Most non-native species are accidentally introduced, but others were deliberately introduced. For example, Spartina cord grass was intentionally introduced to stabilize reclaimed shoreline areas in Willapa Bay and Padilla Bay. Spartina has displaced large areas of native vegetation and has changed the habitat in Willapa Bay and Puget Sound.

Transportation of live shellfish and seafood across the country or from international markets is another way exotic species are introduced. For example, shellfish stock brought into Washington waters from other areas may harbor unwelcome visitors either in the shellfish stock itself or the packing material for the shellfish.

Pet stores and private aquarium owners are another pathway. Pet stores sell fish, snails and exotic plants for home aquariums but sometimes they end up in the nearest body of water and threaten native species.

Public aquariums are sometimes responsible for unintentionally allowing exotic plants and animals to escape into nearby waterways. Biological supply houses, research facilities and college laboratories prepare, ship, receive and use exotic species for research and investigation. These species, if not properly handled and disposed of, can easily be introduced into our waters. The great equalizer, Mother Nature, also moves live species outside of their normal range by providing favorable environmental conditions and a way for the species to get there, i.e. the El Nino oscillations.

Washington is at risk

Washington and our Canadian neighbor are, so far, fortunate compared to other areas of the nation. But recent discoveries of the European green crab along the Washington and British Columbia coasts are an ominous sign. Puget Sound currently has 49 identified non-indigenous species compared to San Francisco Bay's 250. However, Washington state and British Columbia's $200 million-a-year shellfish industry are at risk.

Specific aquatic nuisance species issues in Washington state include the potential for zebra mussel introductions in the lower Columbia River, which would be disastrous to the shipping, irrigation and hydroelectric facilities of the region. The effects on salmon are unknown. In addition to the possibility for widespread disruption of our coastal ecosystems, these species pose a threat to the Washington oyster industry, which contributes some $40-50 million per year to the state's economy.

In the Puget Sound region prior to 1979, spartina cord grass was only recorded in Port Susan with a total coverage of less than 15 acres. By 1997, spartina had invaded North Puget Sound to more than 660 solid acres, spread over 7,780. Spartina threatens Willapa Bay where it was accidentally introduced in the late 1800's.

During the last decade, spartina has increased dramatically and is estimated to cover about 15 percent of the Bay's mudflats. If not controlled, the destructive grass is expected to cover 75 percent of the bay's mudflats by 2030.

Prevention is the best defense

Once non-native species are established, they are extremely difficult, if not impossible, to eradicate. Prevention is the most effective and cost effective approach to controlling invasions of non-indigenous species.

Business and industry groups are concerned about the problem and are working with federal and state agencies to help solve and prevent the introduction of aquatic nuisance species to Washington waters. The shellfish industry, for example, worked with the state department of Fish and Wildlife to improve management practices at their facilities to minimize the risk of introducing non-native species from imported shellfish and shell stock.

Various West Coast steamship operator associations were instrumental in pulling together regulators, environmentalists and others to find workable solutions to the ballast water problem. The group developed a Pacific Coast Ballast Water management plan that addresses the scope of the problem, ballast water management programs, new technologies, monitoring, research and legislation. The plan is intended to direct coastal states and the shipping industry in developing equitable solutions to the ballast water problem.

As a result, Washington is the only state along the West Coast, and the fifth in the nation with a completed aquatic nuisance species management plan. The Washington State Aquatic Nuisance Species Management Plan was signed by Governor Locke last year and has been submitted to the national task force for approval. The plan will be used to coordinate aquatic nuisance species prevention and is aimed at minimizing the introduction of new aquatic nuisance species and eradicating species already present.

The Washington plan is in conjunction with the nation's efforts to pull ahead in this ferocious race against time and invasion. On Feb. 3, President Clinton signed an Executive Order to "mobilize the federal government to defend against these aggressive predators and pests." He "urged Congress to join us in protecting our economy and our natural heritage against the threat of non-native species."

Jamie Clark, director of the U.S. Fish and Wildlife Service, put it this way: "The battle against invasive species is now one of this agency's highest priorities. We have plants and animals that can endanger our crops, our parks and wildlife refuges, our industry and certainly many of our native plants and animals. This is a serious fight, and we mean to make a serious effort."

The silent crisis of invasive species will be eradicated only through the strong and consistent efforts of everyone who cares about our coasts' ecological and economic future.

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