Scientists tracking progress of an invasive crab in the Chesapeake Bay say a third Chinese mitten crab was caught Friday. Two water men checking crab pots in southern Maryland discovered one of the crabs, which burrow in tributary banks and may compete with native blue crabs for food. Gregory M. Ruiz, senior scientist at the Smithsonian Environmental Research Center in Edgewater, told The (Baltimore) Sun the mitten crabs are either reproducing in the Chesapeake Bay or repeatedly being released in the ballast water of ships. Biologists fear the mitten crab, which has furry claws and long legs, could swarm over riverbanks, dig burrows that cause erosion and rip up fishing nets. The crabs are believed to have hitchhiked to the Chesapeake aboard ships from Asia.The crab also has been found in California, Germany and England. “It’s a concern, because there is a lot of evidence that this crab could establish itself here,” said Ruiz, a marine ecologist. “In other places where it has been established, it goes through years where there are outbreaks, and they are incredibly abundant.” Ruiz said that mitten crabs aren’t likely to directly hurt blue crabs, but they could compete for valuable food sources such as submerged aquatic vegetation and young blue crabs and mussels.