Blue Crabs are harvested commercially and recreationally via many methods, including dredging, crab potting, and trawling. In Chesapeake Bay, Blue Crabs have the highest value of any commercial fishery. Because of this, monitoring programs such as the Trawl Survey are essential to provide fisheries managers with long-term population data.
Blue Crabs can easily be sexed by the differences in their abdomen shape. This is a male.
Female Blue Crabs have a triangular shaped abdomen when they are juveniles (shown in picture). After their terminal molt, at which time they mature, the abdomen is more dome shaped.
Most Blue Crabs in the Chesapeake Bay region are brownish green dorsally with off-white underparts. However, color variations, such as this specimen, are not unusual.
Blue Crab claws (or chelipeds) are multi-functional. They are used as organs of expression, as weapons, and to assist in feeding. Studies describe such acts as cheliped poking, striking, embracing, fending and shielding. As well, one pincher is usually used for crushing while the other is used for cutting.
The mating process of Blue Crabs begins when the females are ready for their terminal molt. At this time, a male crab will grasp onto her and carry her upright under his body. The male will release the female when she sheds the old exoskeleton, and then reposition her so that their ventral surfaces are together. The process of copulation (shown in photo) may last for several hours. After copulation, the female will resume the upright position and the male will carry her until the new shell hardens.
Although Blue Crabs mate in waters of low salinity, the females migrate to higher salinity areas to release the eggs. Therefore, most of the adult female Blue Crabs with egg masses (often called "sponge crabs") are collected by the survey in the Chesapeake Bay mainstem. For these crabs, their egg stage is noted in addition to their carapace width. For example, orange egg masses indicate early development, and black egg masses indicate late development.