Blue King Crab | Oceana
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Cephalopods, Crustaceans, & Other Shellfish

Blue King Crab

Paralithodes Platypus

The blue king crab is the largest king crab species and one of the largest crustaceans. In the past, this species supported a large fishery, worth millions of dollars, but numbers have been reduced to the point that commercial fishers no longer target the blue king crab directly. It lives on soft bottom habitats throughout the Bering Sea and adjacent waters. Along with true crabs, prawns, and lobsters, the king crabs are decapods; they have ten legs. Blue 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 other predators.

Distribution

Cold temperate and sub-polar latitudes of the north Pacific Ocean

Ecosystem/Habitat

Soft bottoms

Feeding Habits

Foraging omnivore

Conservation Status

Unknown

Taxonomy

Subphylum Crustacea (crabs, shrimps, and relatives), Family Lithodidae (king crabs)

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The blue king crab is the largest king crab species and one of the largest crustaceans. In the past, this species supported a large fishery, worth millions of dollars, but numbers have been reduced to the point that commercial fishers no longer target the blue king crab directly. It lives on soft bottom habitats throughout the Bering Sea and adjacent waters. Along with true crabs, prawns, and lobsters, the king crabs are decapods; they have ten legs. Blue 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 other predators.

Blue king crabs are omnivorous and will eat just about any dead or decaying organic matter (plant or animal) and a variety of living invertebrates.  Like in all decapods, the blue 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. 

As mentioned above, blue king crab populations have declined significantly in the last few decades, and they are no longer targeted directly by commercial fishers.  They are still legally captured in fisheries targeting other species, so they continue to be fished to some degree.  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.  The conservation status of the blue king crab is not well known, but their populations are apparently struggling to recover, even in the face of reduced fishing.  Further study into the life history and further monitoring of the population trends of this species are necessary to determine whether or not any conservation actions need to be taken.

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Additional Resources:

http://www.adfg.alaska.gov/index.cfm?adfg=bluekingcrab.main

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