Paralithodes camtschaticusred king crab

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)

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)

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)

  • 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)

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)

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)

  • 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)

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)

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)

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

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)

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.

Contributors

Renee Sherman Mulcrone (editor).

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

Glossary

Arctic Ocean

the body of water between Europe, Asia, and North America which occurs mostly north of the Arctic circle.

Atlantic Ocean

the body of water between Africa, Europe, the southern ocean (above 60 degrees south latitude), and the western hemisphere. It is the second largest ocean in the world after the Pacific Ocean.

World Map

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

Pacific Ocean

body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.

Palearctic

living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

World Map

benthic

Referring to an animal that lives on or near the bottom of a body of water. Also an aquatic biome consisting of the ocean bottom below the pelagic and coastal zones. Bottom habitats in the very deepest oceans (below 9000 m) are sometimes referred to as the abyssal zone. see also oceanic vent.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

coastal

the nearshore aquatic habitats near a coast, or shoreline.

colonial

used loosely to describe any group of organisms living together or in close proximity to each other - for example nesting shorebirds that live in large colonies. More specifically refers to a group of organisms in which members act as specialized subunits (a continuous, modular society) - as in clonal organisms.

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

external fertilization

fertilization takes place outside the female's body

fertilization

union of egg and spermatozoan

food

A substance that provides both nutrients and energy to a living thing.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

holarctic

a distribution that more or less circles the Arctic, so occurring in both the Nearctic and Palearctic biogeographic regions.

World Map

Found in northern North America and northern Europe or Asia.

intertidal or littoral

the area of shoreline influenced mainly by the tides, between the highest and lowest reaches of the tide. An aquatic habitat.

introduced

referring to animal species that have been transported to and established populations in regions outside of their natural range, usually through human action.

macroalgae

seaweed. Algae that are large and photosynthetic.

metamorphosis

A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

pheromones

chemicals released into air or water that are detected by and responded to by other animals of the same species

phytoplankton

photosynthetic or plant constituent of plankton; mainly unicellular algae. (Compare to zooplankton.)

planktivore

an animal that mainly eats plankton

polar

the regions of the earth that surround the north and south poles, from the north pole to 60 degrees north and from the south pole to 60 degrees south.

polygynous

having more than one female as a mate at one time

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

social

associates with others of its species; forms social groups.

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

visual

uses sight to communicate

zooplankton

animal constituent of plankton; mainly small crustaceans and fish larvae. (Compare to phytoplankton.)

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.