Commercial fishing has tried to preserve the blue crab stock by not harvesting egg-bearing females, but fishing methods have become so efficient that scientists are alarmed about the effects on males. The number of legal-size males in the Chesapeake blue crab population has gone from near 60 percent in the late 1960s to just 10 percent last year. Watermen used to be able to make a good portion of their living oystering, or fishing gill nets for various fin fish. But now they're almost entirely dependent on making a year's living off of crabs. Eating Their Own Because blue crabs are cannibals, young males also have been falling prey to their elders in larger numbers as a result of real estate development near salt marshes.
Crabs grow only by molting, shedding their shells and growing new ones.
Until a crab's new shell forms, he is defenseless. Hines and other scientists say young males used to scramble up the bay's salt creek tributaries to seek shelter in woody debris along the banks. But restrictions on land development near bay shorelines has not stopped the development of farms and suburban housing complexes on once natural land. Whether the new arrival along the tributaries is a farm or a townhouse, scientists say, the first victim of development is the woody refuge of the blue crab. This year, scientists are testing the theory that the growing prevalence of younger males has brought about a drop in the crab population's sperm count.