Animal Diversity Web

Ge­o­graphic Range

Par­alith­odes camtschati­cus is dis­trib­uted through­out the north­ern Pa­cific Ocean. They can be found as far south as the Sea of Japan, and north up to the Kam­chatka Penin­sula. On the west coast of North Amer­ica the south­ern limit is the Queen Char­lotte Is­lands, and the most north­ern point is Bar­row, Alaska. Par­alith­odes camtschati­cus is also found in the south­east­ern Bering Sea. While not na­tive to the At­lantic Ocean, P. camtschati­cus was com­mer­cially in­tro­duced in the Bar­ents Sea, north of Rus­sia. (Bliss, 1982; For­rest Blau , et al., 2002; Jew­ett and Onuf, 1988)

• Biogeographic Regions
• nearctic
• palearctic
• arctic ocean
• atlantic ocean
  • introduced
• pacific ocean

• Other Geographic Terms
• holarctic

Habi­tat

Adults are found in the in­ter­tidal zone at depths of more than 200 m in the pre­ferred sand and mud sub­strates. An­nual mi­gra­tions from the deep to shal­low wa­ters (50 m or shal­lower) occur in the late win­ter/early spring for mat­ing. (For­rest Blau , et al., 2002; Jew­ett and Onuf, 1988)

• Habitat Regions
• temperate
• polar
• saltwater or marine

• Aquatic Biomes
• benthic
• coastal

• Other Habitat Features
• intertidal or littoral

Phys­i­cal De­scrip­tion

Par­alith­odes camtschati­cus have a dark red body and are char­ac­ter­ized by hav­ing a fan shaped tail. King crabs have 5 sets of ap­pendages, the first two are pin­cers, the right is usu­ally larger then the left. The last ap­pendages are used for mat­ing. For males the last two ap­pendages are used to spread sper­matophore over the gen­i­tal open­ing of a fe­male, and for fe­males the ap­pendages are used to aid in the spread­ing of the sper­matophore. (Bliss, 1982; Jew­ett and Onuf, 1988)

• Other Physical Features
• ectothermic
• heterothermic
• bilateral symmetry

• Sexual Dimorphism
• sexes alike

• Range mass

  12.7 (high) kg

  27.97 (high) lb

• Average mass

  10 kg

  22.03 lb

• Average length

  220 mm

  8.66 in

De­vel­op­ment

Alaskan king crabs have two stages of de­vel­op­ment. In the first stage of de­vel­op­ment P. camtschati­cus are free-swim­ming zoea. Zoea are very small and do not re­sem­ble the adult crab. Dur­ing 3 to 4 months, the zoea molt 5 times. After the fifth molt the lar­val zoea begin to re­sem­ble the adult form, they are about 1/8 of an inch at this point, and adopt a ben­thic, or bot­tom dwelling, lifestyle. (Jew­ett and Onuf, 1988)

• Development - Life Cycle
• metamorphosis

Re­pro­duc­tion

Fe­males at­tract males with a chem­i­cal that is re­leased after eggs have hatched. The male then clasps onto the fe­male and they re­main con­nected until the fe­male molts, and pro­duces new eggs. Fe­males mate once a year while males may mate mul­ti­ple times each spring. (For­rest Blau , et al., 2002; Jew­ett and Onuf, 1988)

• Mating System
• polygynous

Fe­male Alaskan king crabs mate im­me­di­ately after the eggs hatch. Dur­ing this process a male is at­tracted by a chem­i­cal that is re­leased by the fe­male. The male then clasps onto the fe­male and holds her until she molts. The fe­male and male may re­main con­nected for up to 7 days. After molt­ing the male uses his fifth pair of legs to spread sper­matophores over the fe­males open­ing. The fe­males eggs are then re­leased and pass over the sper­matophores and be­come fer­til­ized. These fer­til­ized eggs are at­tached by the fe­male to her pleopods under the ab­domen and are in­cu­bated for ap­prox­i­mately a year be­fore hatch­ing. (Bliss, 1982; Jew­ett and Onuf, 1988)

• Key Reproductive Features
• seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual
• fertilization
  • external

• Breeding interval

  Females breed once annually, while males can possibly mate with 11 females during the breeding season.

• Breeding season

  Alaskan King Crabs breed in the spring after migrating to water depths of 50 meters or less.

• Range number of offspring

  150,000 to 400,000

• Range age at sexual or reproductive maturity (female)

  5 to 6 years

• Range age at sexual or reproductive maturity (male)

  5 to 6 years

Fe­male Alaskan king crabs in­cu­bate eggs for 1 year, pro­vid­ing pro­tec­tion. Within days of hatch­ing, the fe­male be­gins in­cu­bat­ing next group of eggs. (Bliss, 1982; Jew­ett and Onuf, 1988)

• Parental Investment
• pre-fertilization
  • provisioning
• pre-hatching/birth
  • protecting
    • female

Lifes­pan/Longevity

The ex­pected lifes­pan of P. camtschati­cus is 15 to 20 years. The biggest non-com­mer­cial threat is molt­ing. Molt­ing can be stress­ful and cause death. In ad­di­tion, the days after a molt are the most dan­ger­ous for P. camtschati­cus, when the soft shell is vul­ner­a­ble to pre­da­tion. How­ever, the main limit on life span for Alaskan king crabs is over-fish­ing. (For­rest Blau , et al., 2002; Jew­ett and Onuf, 1988)

• Range lifespan
  Status: wild

  20 to 30 years

• Typical lifespan
  Status: wild

  15 to 20 years

Be­hav­ior

Alaskan king crabs tend to be seg­re­gated by sex when at deeper wa­ters. So­cial and colo­nial char­ac­ter­is­tics are seen in ju­ve­niles be­tween the ages of 1 to 4 years old, when they pod, or form large groups of in­di­vid­u­als. Pod­ding oc­curs at shal­low depths and is used for pro­tec­tion. Alaskan king crabs are nata­to­r­ial, or adapted for swim­ming, when they are in their pelagic stage in the form of free-swim­ming zoea. (For­rest Blau , et al., 2002; Jew­ett and Onuf, 1988)

• Key Behaviors
• natatorial
• motile
• social
• colonial

Com­mu­ni­ca­tion and Per­cep­tion

Alaskan king crabs com­mu­ni­cate dur­ing mat­ing when the fe­male re­leases a chem­i­cal that sig­nals a male that she is ready to ovu­late. (Jew­ett and Onuf, 1988)

• Communication Channels
• tactile
• chemical

• Other Communication Modes
• pheromones

• Perception Channels
• visual
• tactile
• chemical

Food Habits

Lar­val P. camtschati­cus are plank­ti­vores. The adult form feeds on many dif­fer­ent an­i­mals in­clud­ing some fish parts and are gen­er­al­ized car­ni­vore. (For­rest Blau , et al., 2002; Jew­ett and Onuf, 1988)

• Primary Diet
• carnivore
  • eats non-insect arthropods
• planktivore

• Animal Foods
• fish
• mollusks
• aquatic or marine worms
• aquatic crustaceans
• echinoderms
• zooplankton

• Plant Foods
• algae
• macroalgae
• phytoplankton

Pre­da­tion

Dur­ing the first year Alaskan king crabs hide in crevices formed by rocks or kelp forests to avoid pre­da­tion. From the ages of 1 to 4 Alaskan king crabs form clus­ters of up to 500,000 in­di­vid­u­als called pods. The pods dis­perse only for feed­ing. This be­hav­ior is thought to be used for pro­tec­tion dur­ing molt­ing, when a crab is most vul­ner­a­ble. The adult Alaskan king crabs have few preda­tors be­cause of their heav­ily ar­mored and bumpy cara­pace. Car­ci­none­mertes (ne­mertean worms) feed on eggs while mother is in­cu­bat­ing. Er­i­macrus isen­beckii (Ko­rean hair crab), En­hy­dra lutris (sea ot­ters), and Heim­lepi­do­tus or My­ox­o­cephalus (sculpins) are pos­si­ble preda­tors for adults. (Bliss, 1982; Jew­ett and Onuf, 1988; Warner , 1977)

• Known Predators

  • nemertean worms (Carcinonemertes)
  • Korean hair crabs (Erimacrus isenbeckii)
  • sea otters (Enhydra lutris)
  • Irish lords (Hemilepidotus)
  • sculpins (Myoxocephalus)

Ecosys­tem Roles

As adults, Alaskan king crabs are major preda­tors. The mass num­bers of zoea also serve as a food source for many or­gan­isms. (Bliss, 1982; For­rest Blau , et al., 2002; Jew­ett and Onuf, 1988; Pa­cific Seafood Group, 2001-2002; Warner , 1977)

Eco­nomic Im­por­tance for Hu­mans: Pos­i­tive

From 1960 to 1970 Alaskan king crabs gen­er­ated hun­dreds of mil­lions of dol­lars in eco­nomic rev­enue. How­ever, within two years of over fish­ing in a given area catch re­turns di­min­ish to a frac­tion of the orig­i­nal catch. Now the United States gets the ma­jor­ity of its crab meat from the North At­lantic Ocean north of Rus­sia. There is now a rule for fish­ers that they can only catch males. (Bliss, 1982; For­rest Blau , et al., 2002; Jew­ett and Onuf, 1988; Pa­cific Seafood Group, 2001-2002; Warner , 1977)

• Positive Impacts
• food

Eco­nomic Im­por­tance for Hu­mans: Neg­a­tive

There are no known ad­verse af­fects of P. camtschati­cus on hu­mans.

Con­ser­va­tion Sta­tus

There is no spe­cial sta­tus on Alaskan king crabs. How­ever, due to over har­vest­ing the pop­u­la­tion of P. camtschati­cus is con­sis­tently low. A pro­posed pos­si­ble so­lu­tion is that crab­bers are only al­lowed to catch male Alaskan king crabs.

• IUCN Red List

  No special status

• US Federal List

  No special status

• CITES

  No special status

Con­trib­u­tors

Renee Sher­man Mul­crone (ed­i­tor).

Michael Kluce (au­thor), Uni­ver­sity of Michi­gan-Ann Arbor, Phil Myers (ed­i­tor), Mu­seum of Zo­ol­ogy, Uni­ver­sity of Michi­gan-Ann Arbor.

Ref­er­ences

Bliss, D. 1982. Shrimps, Lob­sters, and Crabs. New Jer­sey: New Cen­tury Pub­lish­ers INC.

For­rest Blau , S., D. Kuk­lok , S. Comp­ton . 2002. "Alaska King Crabs" (On-line ). ADF&G Wildlife Note­book Se­ries. Ac­cessed 03/17/03 at http://​www.​state.​ak.​us/​local/​akpages/​FISH.​GAME/​notebook/​shellfsh/​kingcrab.​htm.

Jew­ett, S., C. Onuf. 1988. "Habi­tat Suit­abil­ity Index Mod­els: Red King Crab" (On-line ). Ac­cessed 03/19/03 at http://​www.​nwrc.​gov/​wdb/​pub/​hsi/​hsi-153.​pdf.

Pa­cific Seafood Group, 2001-2002. "King Crab" (On-line ). Pa­cific Seafood. Ac­cessed 03/17/03 at http://​www.​pacseafood.​com/​products/​king_​crab.​html.

Warner , G. 1977. The Bi­ol­ogy of Crabs. Great Britain: Pail Elek (Sci­en­tific Books) Ltd.