The stone crab’s body is about is 5 to 6.5 inches long and about 5 inches wide in larger specimens. They are brownish red with gray spots and a tan underside, and have large and unequally-sized chlae (claws) with black tips. In addition to the usual sexual dimorphism exhibited by crabs, the female stone crabs have a larger body than males of a similar age, and males generally have larger claws than females.
Stone crabs prefer the bottoms of bays, grass flats, oyster reefs, and rock jetties where they can burrow or find refuge from predators. Juveniles do not usually dig burrows, but instead hide among rocks or in seagrass beds. It is dark brownish-red with gray interspersed. The claws are hinged, very dark, and banded with red and yellow. Adult Stone crabs make burrows in mud or sand below the low tide line, lying in wait for prey. Stone crabs prefer to feed on oysters and other small mollusks, polychaete worms, and other crustaceans. They will also occasionally eat seagrass and carrion. Predators that feed on stone crabs include horse conch, grouper, sea turtles, cobia, octopuses and humans.
Sexual maturity is reached at one year. Their long spawning season lasts all spring and summer, during which time females produce 500,000 to 1 million eggs. The larvae go through six stages in about 36 days before emerging as juvenile crabs. Their lifespan is seven to eight years. The male stone crab must wait for the female to molt her exoskeleton before they can mate. After mating, the male will stay to help protect the female for several hours to several days. The female will spawn four to six times each season. The stone crab loses its limbs easily to escape from predators or tight spaces, but their limbs will grow back. When a claw is broken such that the diaphragm at the body/claw joint is left intact, the wound will quickly heal itself and very little blood is lost. If, however, the claw is broken in the wrong place, more blood is lost and the crab’s chances of survival are much lower. It only takes about one year for the claw to grow back to its normal size. Each time the crab molts, the new claw grows larger.
The larger of the two claws is called the “crusher claw”. The smaller claw is called the “pincer claw”. If the larger crusher claw is on the right side of the crab’s body, the crab is “right-handed”. If the crusher claw is on the left side of the crab’s body, it is “left-handed”. Since crabs’ eyes are on stalks, they can see 360°. A large crab claw can weigh up to half a pound.
The crab only molts at night or in night-like conditions due to the crab being extremely vulnerable to predators without the protection of its shell. If the crab is becoming too large for its shell and the sun is up, the crab releases a hormone from a gland located on one of their eye stalks called the x-organ. This hormone prevents the crab from molting from its shell until it finds a safe place to molt or it has become dark enough outside to molt in safety.
The bodies of stone crabs are relatively small and so are rarely eaten, but the claws – large and strong enough to break an oyster’s shell, are considered a delicacy. Harvesting is accomplished by removing one claw from the live animal and returning it to the ocean where it can regrow the lost limb. To be kept, the claws must be 2.75 inches long, measured from the tips of the immovable finger to the first joint. Mortality rates are 47% for doubly-amputated crabs and 28% for single amputees. Stone crabs are legal for harvest from October 15 until May 15.
To prevent the meat from sticking to the shells, stone crab claws are cooked immediately before being chilled. Stone crab claws—typically the only part of the shellfish that’s eaten—are usually served chilled, but they’re still quite tasty when steamed and eaten with a little melted butter, like lobster.