Stone crabs are found in the western north Atlantic from the Carolinas, throughout the northern Gulf, to the Yucatan Peninsula and throughout the Caribbean. Gulf stone crabs live on mud flats and oyster reefs in nearshore and estuarine areas. Florida stone crabs live in seagrass beds or on rocky bottoms in higher salinity waters.
Stone crabs grow by molting—their hard shell restricts growth so they must shed it to increase in size. They can grow up to six inches carapace (shell) width. Stone crab are able to reproduce by age one. They can only mate after the female has molted and her shell is soft. Large males travel to inshore waters near oyster reefs and seagrass beds to mate with molting females, usually in the fall. They deposit their sperm into the females; females store the sperm over the winter and fertilize their eggs internally during the following spring and summer. Females push the fertilized eggs out beneath their abdomen in a mass called a sponge. They can store as many as one million eggs in the sponge and can produce several sponges in a single spawning season. Stone crab can live up to seven or eight years.
Stone crabs are generally carnivores but will occasionally feed on plant material. Larvae feed on zooplankton while juvenile and adult stone crab feed on shellfish such as mussels, clams, and oysters, anemones, worms, and other crustaceans. Their powerful claws help them crush, cut, and tear their prey. If a crab loses one or both of its claws, it makes feeding more difficult so the crab may change its feeding behavior and resort to scavenging. Fish, larger crabs, sea turtles, and octopi feed on stone crabs, especially juveniles, as they haven’t yet developed their larger claws.
Stone crabs are crustaceans with a hard upper shell and ten legs: eight for swimming and walking and two claws for pinching prey or predators. One is a large crusher claw and the other is a smaller pincer claw with numerous small teeth used for cutting. Stone crabs are usually “right-handed,” meaning that the crusher claw is usually on the right.
There are two species of true stone crabs: Florida (Menippe mercenaria) and Gulf (M. adina). The two also interbreed, creating a hybrid. Gulf stone crabs are maroon brown. Florida stone crab is tan to light gray with small black spots and dark legs with white bands. Stone crab claws have black tips. You can distinguish male and female stone crabs by their abdomen—females have a wide round abdomen and males have a long narrow abdomen.