King crabs are large, spine-covered crustaceans found primarily in the cold, deep waters of the North Pacific Ocean. They are recognized globally for their massive size and the high value of their sweet, tender meat. King crabs are a significant component of the marine ecosystem and support one of the world’s most famous commercial fisheries. Understanding the basic facts about these seabed dwellers provides context for their prominence in the natural world and the seafood market.
Defining Features and Classification
King crabs are often mistakenly grouped with “true crabs,” but they belong to the infraorder Anomura, which also includes hermit crabs. True crabs are classified in the infraorder Brachyura. The king crab’s superficial resemblance to true crabs is due to carcinization, where non-crab-like crustaceans evolve a crab-like body form.
A fundamental difference lies in their functional leg count. King crabs possess only three pairs of walking legs plus a pair of large claws (chelipeds), totaling eight visible appendages. True crabs, by contrast, have four pairs of walking legs in addition to their claws. The tiny, fourth pair of walking legs on a king crab is tucked away inside the carapace (shell) and is used for cleaning the gills or assisting in reproduction.
Their massive size is a defining characteristic, with some species reaching a leg span of up to five feet and weighing over 20 pounds, making them among the largest arthropods. The exoskeleton is heavily calcified and often covered with sharp spines, providing robust protection. King crabs also possess a fan-shaped abdomen that is tucked underneath the rear of the shell, unlike the fully tucked abdomen of a true crab.
The Primary Species of Commercial Value
The commercial king crab fishery focuses predominantly on three species, distinguished by color, size, and distribution. The Red King Crab (Paralithodes camtschaticus) is the most sought-after species, known for its deep red or burgundy shell. It is the largest of the three, with some males reaching up to 24 pounds, and is the most abundant in areas like Bristol Bay and the Kodiak Archipelago in Alaska.
The Blue King Crab (Paralithodes platypus) is similar in size to the red king crab but has a blue-toned shell that turns red when cooked. Blue king crabs are found in localized populations, such as around the Pribilof Islands and St. Matthew Island in the North Pacific. The third major species is the Golden or Brown King Crab (Lithodes aequispinus).
The Golden King Crab is the smallest of the three, typically weighing between five and eight pounds. This species inhabits deeper waters, often exceeding 1,800 feet, and is found along the Aleutian Islands and down to British Columbia.
Habitat, Diet, and Reproduction
King crabs are adapted to the cold, benthic environments of the continental shelf and slope, typically living at depths below 600 feet. They inhabit soft substrates like mud and silt, but juveniles seek out complex, shallower habitats such as shell hash and kelp forests for protection. These crustaceans are omnivorous and opportunistic feeders, acting as scavengers and predators on the ocean floor. Their diet includes bottom-dwelling invertebrates, such as worms, small clams, mussels, sea stars, and sea urchins.
The reproductive cycle begins with an annual migration to shallower waters in the late winter or early spring for mating. The female releases a chemical signal to attract a male, who clasps her until she molts, which is necessary for mating. After fertilization, the female attaches the thousands of embryos (50,000 to 500,000) to her abdomen, where they are brooded for nearly a year. The eggs hatch into free-swimming larvae called zoea, which drift in the water column for several months before settling to the bottom and metamorphosing into tiny crabs.
The King Crab Fishery
The pursuit of highly valued king crab meat has established an economically significant fishery. Primary harvest areas are concentrated in the cold waters of Alaska, particularly the Bering Sea and Aleutian Islands. Russia and Norway also contribute significantly to the global catch. The fishing season is short, typically occurring in the fall, and is strictly managed to protect the stock, often lasting only a few weeks.
The high demand for king crab translates to a premium market price, with the red king crab commanding the highest value. Fishing vessels use large, heavy, mesh-covered pots or traps, which are baited and dropped to the seabed. Management is based on the “three S’s”—size, sex, and season. This strategy dictates that only male crabs above a certain size can be retained, ensuring the breeding female population is protected.