Shrimps Crabs and Lobsters: Decapoda

Physical characteristics: Red king crabs are a very large, reddish brown species with a carapace measuring up to 11 inches (280 millimeters) wide. Their legs stretch more than 6 feet (1.8 meters) across. Both the carapace and legs are covered with lots of sharp spines. The right claw is larger than the left. Only three pairs of walking legs are visible.

Geographic range: This species lives in the Sea of Japan to northern British Columbia. It was introduced into the Barents Sea and has spread westward to Norway.

Habitat: Red king crabs live at depths of 10 to 1,190 feet (3 to 366 meters) and prefer open habitats with sandy or muddy bottoms.

Two-year-old juveniles often gather by the hundreds or thousands to form spectacular mounds known as pods. (Eiichi Kurasawa/Photo Researchers, Inc.)

Diet: They prey on a variety of bottom-dwelling invertebrates, including brittle stars, sea stars, sand dollars, and sea urchins, barnacles, worms, mollusks, and sponges.

Behavior and reproduction: Two-year-old juveniles often gather by the hundreds or thousands to form spectacular mounds known as pods in shallow water. The pods are thought to discourage predators; they disperse shortly after dusk, as the crabs forage for prey, and form again before dawn.

Mating occurs just after the female molts, and her exoskeleton is still soft. The male uses his small fifth pair of walking legs to spread sperm over the female's pleopods. Anywhere from 150,000 to 400,000 eggs come out of the female's body right away, but they take almost a year to hatch. The larvae do not resemble the adults and molt four times before settling on the ocean bottom.

Red king crabs and people: Red king crabs were once the target of one of the most valuable fisheries off Alaska in United States waters. Commercial harvesting is carried out with large baited pots.

Conservation status: The World Conservation Union (IUCN) does not consider this species to be threatened or endangered. However, populations off the coast of Alaska and in the western Bering Sea have suffered as a result of over-fishing. A population introduced to the Barents Sea appears to be growing. ∎