The discovery of invaded species at Chesapeake bay area created worries among researchers by Gregory.The fuzzy-clawed crab that waterman Vince Meyer and his crew pulled from the Chesapeake Bay clearly did not belong there: it lacked the blue markings of the area's signature crustacean, plus it had hairy pincers. "He noticed it as soon as he saw it," Meyer said of his crewman, Henry DuPreez, who pulled in the creature in question, a Chinese mitten crab.This is the third year in a row watermen have found the invasive crab in the Mid-Atlantic bay, a development that worries environmental researchers and watermen.The species is not native to the region and can breed abundantly. If it becomes established in the area's waterways, no one knows how it might affect the Chesapeake's already-stressed ecosystem or its famous blue crab population."We can't predict what the impact would be," said Gregory Ruiz, a marine ecologist at the Smithsonian Environmental Research Center who examined Meyer's crab, now captive in an aquarium.He said the fear is the mitten crab would compete for food with the blue crabs, or eat them.Potential threats are not taken lightly. Blue crabs are the backbone of a major industry on the 200-mile-(320-km)-long Chesapeake Bay, the largest estuary in the United States. The crab harvest alone is worth more than $50 million, according to government figures.Chesapeake crabs are celebrated at fairs and festivals where crustacean queens are crowned and local craftsmen sell knickknacks and Christmas ornaments made from their shells.But mostly people eat them. Hundreds of crab shacks and seafood restaurants in the region serve them steamed to mallet-wielding patrons or pan-fried when the shells are soft. They are made into soups, dips, crab cakes and other delights.Limits have been placed on the size of the crab catch because of degraded conditions in the bay and concerns about the overall crab population, which a recent study found has been below target levels for a decade. The harvest is down from historical levels, but has been 50 million to 60 million pounds per year since 2000.About 170 invasive species have moved into the bay, contributing to its stressed condition. The nutria rodent is damaging marshes and the rapa whelk mollusk feeds on clams and oysters. Scientists say local species don't need any more competition, and that is the worry with the mitten crab."The concern is really the potential for high impact," Ruiz said, "but whether that would be borne out, I think, is not clear."Mitten crabs, a culinary delight in Asia, can be something of a nuisance. They are burrowers, exacerbating soil erosion. After establishing themselves in the San Francisco area in the early 1990s, they played havoc with the water system."The crabs basically were so abundant that they clogged water supply systems by clogging up filter screens," Ruiz said.They rear their offspring in freshwater tributaries, but migrate to shallower salt water areas to reproduce. Vulnerable blue crabs -- the babies and molting adults -- find refuge in the same kinds of habitats where mitten crabs breed, raising concerns they could become the invaders' prey.So far, there is no evidence mitten crabs are reproducing in the Chesapeake. The three examined by researchers were fully developed males. No females or babies have been seen.That suggests the mitten crabs found there may have been sucked aboard a ship taking on ballast water in Europe, Asia or San Francisco and then released into the bay when the vessel reached port. Researchers want to locate the source of the crabs, so watermen are on the alert as the summer crabbing season gets under way. For Meyer, who runs Vince's Crabhouse in the Baltimore suburb of Essex, Maryland, that means keeping a close watch as he checks his 500 to 600 crab pots each day. "They say they're not good for the bay," he said. "I guess they don't have predators and they're afraid they might maybe try to eat the blue crab."
No comments:
Post a Comment