The red king crab is one of the largest and most valuable king crab species and is the target of a large fishery throughout the Bering Sea and adjacent areas. It lives on soft-bottom habitats from the shallows down to depths of at least 600 feet (180 m). Along with true crabs, prawns, and lobsters, the king crabs are decapods; they have ten legs.
Red king crabs are covered with a spiny exoskeleton that provides them some protection from potential predators, but at different stages of its lifecycle, the species is preyed upon by fishes, octopuses, and some marine mammals. red king crab are also known to be occasionally cannibalistic.
Red king crabs are omnivorous and will eat just about any dead or decaying organic matter (plant or animal) and a variety of invertebrates. Like in all decapods, the red king crab’s shell really is a skeleton on the outside of its body. The exoskeleton does not expand, and therefore individuals must molt (shed) it regularly in order to grow bigger. Before molting, an individual begins building a new, larger skeleton inside the existing one. As it gets too big to be contained, it splits open the outer shell, and the new exoskeleton hardens. During this process, the new exoskeleton can be soft for some time, and the crab is vulnerable to predation.
This species reproduces via internal fertilization, and the females brood the fertilized eggs under their abdomen for as long as a year. Red king crabs prefer cold water, so they stay relatively deep during the summer when they primarily concentrate on feeding and caring for their eggs. In the winter, they migrate to shallower waters, where the eggs hatch, and the sexually mature individuals molt and mate again. Adult red king crabs can be very large, with leg spans reaching nearly five feet (1.8 m) and weighing over 20 pounds (9 kg).
The large size and attractive taste of the red king crab make it one of the most valuable and sought after fisheries species in the North Pacific and the most coveted king crab. Despite its value, the red king crab fishery is generally considered to be well managed, and the species is not currently one of concern. There have been recent population declines, however, and the total amount that resource managers allow fishers to take is lower than it has been in recent years. Fortunately, this species is captured via trap, rather than by trawl or other destructive bottom fishing gear, so the fishery does not alter the ecosystem significantly. One concern involves the invasive nature of this species in the Barents Sea. Red king crabs were purposely introduced to that basin in the 1960s and have increased in numbers and distribution every year because of a lack of natural predators. There is now a valuable fishery for the species there, but the large numbers of red king crabs are damaging the natural ecosystem and threatening native species.
Size and Sex Determination
Male red king crabs grow larger than females and their sex is determined by examining their abdomens. Male red king crabs have a narrow abdominal flap whereas female red king crabs have a wide abdominal flap that covers most of the underside of the abdomen.