The perils of a crab in unfamiliar waters
When gill-netter Louis Williams returned to Gloucester late last month with a crab five times larger than anything he normally catches, wholesaler Frank Ciaramitaro thought the fisherman was pulling his leg.
Ciaramitaro, who had recently received a shipment of live crabs from the West Coast, immediately recognized Williams's find as a Dungeness crab. But the cold-water crustacean does not live in the Atlantic.
``I thought it was a joke," Ciaramitaro said. ``I can't believe it would travel that far."
The crab, which was netted in deep water several miles off Cape Ann , was turned over to the Gloucester Maritime Heritage Center the following day. Marine biologists from Texas to Washington state have since confirmed through photographs that the three-pound crab was indeed a Dungeness, the first of its kind ever found in Atlantic waters .
But just how the crab, which the center's staff later named Dungee, ended up here instead of on the West Coast remains a mystery. Possibilities range from a daring escape from a cruise ship kitchen, to rogue fishermen trying to establish a new fishery, to a Buddhist practice of setting sea creatures free as a form of prayer.
Ecologists don't think that the discovery of a single male Dungeness crab is indicative of a full-scale invasion. But even a single crab from the West Coast could spread diseases that local shellfish and crustaceans haven't been exposed to before and can't protect themselves against. And if a new species of crab did establish itself in large numbers on the East Coast, it could further reduce shellfish populations and push out other crabs, throwing the ecosystem out of balance.
That's what happened when the European green crab, a voracious predator of native clams and mussels, was somehow introduced to the East Coast and spread throughout New England by the 1950s. The Asian shore crab , another crab that preys on shellfish and was first spotted off New Jersey in 1988, can now be found from Maine to North Carolina.
The concerns are the same with East Coast lobsters, which occasionally pop up on the West Coast and can threaten native shellfish if they become widespread.
``Every few years we have someone who bought a lobster at Logan Airport for dinner but by the time they get home to the West Coast they feel sorry for it," said James T. Carlton, a Williams College Mystic Seaport expert in marine invasive species. ``They can't bring themselves to boil it, so the family makes an expedition to the seashore and releases it."
``We see it as playing ecological roulette," he said, adding that foreign species are nearly impossible to get rid of once they gain a foothold. ``It's not like planting carrots, where if you no longer want them you can plow your field."
A more common way marine organisms travel to new waters is by stowing away in the ballast water of ships. Large tankers often carry millions of gallons of water for added stability on the open sea. By picking up seawater at one port and dumping it at another, ships are continually introducing marine organisms to non-native waters.
According to researchers at the Massachusetts Institute of Technology's Sea Grant Center for Coastal Resources , as many as 3,000 species are transported in ships around the world each day.
Surviving such a transit, however, is difficult. Screens keep out the larger organisms, and many of the more vulnerable larvae do not survive. The seven-inch crab that Williams found on July 18 would have had to live for four years in foreign waters to reach its current size, making a ballast water transit unlikely.
A more probable explanation is that the crab came from a local live fish market. A recent survey conducted by the Sea Grant Center found that 12 out of 16 live seafood markets in the Boston area sell the Dungeness crab. Further, only large males, like Dungee, can legally be caught and sold in fish markets.
Researchers have no way of knowing for certain how Dungee ended up in the Atlantic, but Judith Pederson , a coastal resources specialist with MIT's Sea Grant program, figures someone probably released it.
One possibility: the Buddhist practice called prayer animal release . The practice is based on the belief that one might improve one's status in the next life by freeing captive animals.
In response to a previous threat posed by the invasive northern snakehead, Pederson said, she began distributing pamphlets in Chinese, Khmer , Korean, Vietnamese, Spanish, and English requesting people not to release fish and other marine organisms back into the wild.
Invasions have not always been well understood. For years the federal government transported live fish and other marine organisms by the trainload between the Atlantic and Pacific oceans. The cross-continent seeding was thought to enhance local waters on both coasts. In the late 1800s and early 1900s, thousands of American lobsters were transported from New England to Western ports on specially designed ``fish cars," though none of the transplanted lobster populations took hold.
Fishermen and scientists are wiser now, and, thanks to Dungee, some children have also learned about the threat presented by foreign species. Dungee remained on display at the Maritime Heritage Center for a week before he died, most likely due to the stress of being netted and the warmer water of its tank.
``He was a real hit while he lasted," said Eric Sabo , a marine biologist at the center. ``He really served as a great tool for educating people about invasive species and the importance of not letting them go."
