What are the economic importance of crab?

crab supply food for food-fishes, are of great service as scavengers, and are used as human food in various parts of the world. In the United States the principal crab so used is the blue crab (Callincctcs hautains), hundreds of thousands of which are sent to market every year from the waters of Chesapeake Bay alone. The little pea-crabs (Pinnotheres) often found in oysters (see COMMEN8ALISM) are regarded as a great luxury. In К u ropo the species most frequently used are those of the genus Cancer, especially the great Cancer panurus, and there is no reason why the two eastern American species of this genus, the 'rock' and 'lonah' crabs (qq.v.l. should not he far more utilized as food than they are. To this group belong the principal edible crab of the American Pacific coast (Cancer maaistcr), and others smaller which are eaten by the Chinese, etc. This species usually measures 7 to 9 inches in breadth of body, and abounds from Alaska to Mexico, usually below low-tide level on sandy bottom. Crabs which have just shed their shell, and are covered only by a soft skin, are regarded as best, and are called 'shedders* or 'soft-shelled.'