Important facts about the blue crab

Published: Thursday, July 24, 2014 at 12:00 PM.

The blue crab swims beautifully through the water with great speed and ease using a pair of modified appendages that act as paddles. Mature crabs are often brilliant deep blue against a basic creamy white beneath. Bright red may be on the spines of the shell or carapace and on the tips of the claws.

Like all true crabs, the blue crab has 10 legs which may be specialized to walk, swim or pinch. The abdomen is a thin flap tucked below the main body part called the cephalothorax. Inside this hard carapace are the gills and internal organs. The first pair of legs are the large claws, used for catching, cutting and tearing food, and for defense. Behind these are three pairs of walking legs, followed by a pair of swimming legs or paddles.

The sex of the crab may be determined by examining the abdomen or tail folded up under the body. It is usually narrow, triangular, T-shaped and white in the male, but is broad, round and brownish in the female.

Crabs must molt or shed their outer covering or exoskeleton in order to grow.  They also have the power to regenerate lost appendages. Ordinarily, the crab increases one-quarter to one-third in size with each molt. During its life cycle a blue crab molts or sheds its shell about twenty-six times. Once the crab sheds its shell, it generally digs into the sand for protection or hides under submerged objects. From this soft state the carapace will pass through stages of hardness until the new shell is quite brittle.

Mating takes place about now, starting in June and through October, and is timed to when the female sheds her covering. The male blue crab carries the female two or more days until she sheds. You may have witnessed this behavior and wondered why one crab was carrying another. As the female mates only once in a molt this insures that the male will be present at the critical moment of shedding and will also be able to protect the soft female until her new shell is hard.

Eggs are carried in a mass containing 700,000 to 2,000,000 eggs in a fold between the abdomen and carapace. The eggs hatch in about 15 days. Of the vast numbers of eggs produced, less than 1 in 1,000,000 will hatch and survive disease, predation and pesticides to become a mature crab. It is illegal to harvest a gravid female with her egg mass. While legal to harvest females, it is also considered good conservation practice to release all female crabs. According to the Florida FWC, “mature females may store sperm in their bodies for several months after mating in order to spawn at a later date. If a mature female is harvested, though she may not exhibit eggs, there is no certainty that she has spawned.”

The molted or soft-shelled crab is quite a delicacy to eat and can be battered, fried and eaten entire.  In 2012, 68,898 pounds of soft-shell crabs were harvested in Florida, worth $627,246.

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