Alaska King Crab

Wow…. what an Alaska King crab.

Alaska King Crabs

King or stone crabs occur around the world. Commercial fisheries have existed for them in Alaska, Canada, Russia, Japan, Korea, New Zealand, Australia, South Georgia and Falkland Islands, Argentina, and Chile. King crabs have “tails,” or abdomens, that are distinctive, being fan-shaped and tucked underneath the rear of the shell. They also have five pairs of legs; the first bears their claws or pincers, the right claw is usually the largest on the adults, the next three pairs are their walking legs, and the fifth pair of legs are small and normally tucked underneath the rear portion of their carapace (the shell covering their back). These specialized legs are used by adult females to clean their embryos (fertilized eggs) and the male uses them to transfer sperm to the female during mating.

Distribution: In Alaska there are three commercial king crab species. Red king crabs, Paralithodes camtschaticus, have been the commercial “king” of Alaska’s crabs. It occurs from British Columbia to Japan with Bristol Bay and the Kodiak Archipelago being the centers of its abundance in Alaska. Blue king crabs, P. platypus, live from Southeastern Alaska to Japan with the Pribilof and St. Matthew Islands being their highest abundance areas in Alaska. Golden king crabs, Lithodes aequispinus, are distributed from British Columbia to Japan with the Aleutian Islands their Alaska stronghold of abundance. Red and blue kings can occur from the intertidal zone to 100 fathoms or more. Golden king crabs live mostly between 100-400 fathoms, but can occur from 50-500 fathoms.

Life History: Adult females brood thousands of embryos underneath their tail flap for about a year’s time. When the embryos are fully developed they hatch as swimming larvae, but they are still susceptible to the movements of tides and currents. After feeding on plant and animal plankton for several months and undergoing several body changes with each molt, the larvae settle to the ocean bottom and molt into nonswimmers, looking for the first time like king crabs as we normally think of them, except they are smaller than a dime. Red and blue king crabs settle in waters less than 90 and 200 feet deep respectively, while golden king crabs appear to settle in waters 300 feet or deeper!
Because a crab’s skeleton is its shell (made mostly of calcium), it must molt its shell in order to grow. Juveniles molt many times in their first few years, then less frequently until they reach sexual maturity in four or five years. Adult females must molt in order to mate but males do not. Adult males often skip a molt and keep the same shell for one or two years. Red king crabs are the largest of these three species with the record female and male weighing 10.5 and 24 pounds, respectively. These large crabs were estimated to be 20-30 years old. The male’s leg span was nearly 5 feet across.

Adult red and blue king crabs exhibit nearshore to offshore (or shallow to deep) and back, annual migrations. They come to shallow water in late winter and by spring the female’s embryos hatch. Adult females and some adult males molt and mate before they start their offshore feeding migration to deeper waters. Adult crabs tend to segregate by sex off the mating-molting grounds. Red, blue, and golden king crabs are seldom found co-existing with one another even though the depth ranges they live in and habitats may overlap. Adult male red king crabs have been known to migrate up to 100 miles round-trip annually, moving at times as fast as a mile per day! Less is known of the migration of golden king crabs, but it is believed they migrate more in a vertical fashion since they generally inhabit steep-sided ocean bottoms.

Food eaten by king crabs varies by species, size, and depth inhabited. King crabs are known to eat a wide assortment of marine life including worms, clams, mussels, snails, brittle stars, sea stars, sea urchins, sand dollars, barnacles, crabs, other crustaceans, fish parts, sponges, and algae.

King crabs are eaten by a wide variety of organisms including but not limited to fishes (Pacific cod, sculpins, halibut, yellowfin sole), octopuses, king crabs (they can be cannibalistic), sea otters, and several new species of nemertean worms, which have been found to eat king crab embryos.

Alaska King Crab