Paralithodes platypus

The blue king crab is found in cold waters in the Bering Sea, extending slightly into adjacent parts of the Chukchi Sea, off the Kamchatka Peninsula and northeastern Hokkaido, and in the Sea of Okhotsk. In the Bering Sea, the species is less widespread compared to red king crabs. The main populations near Alaska are found near the Diomede Islands, Point Hope, St. Matthew Island, and the Pribilof Islands.{{cite web |title=Blue King Crab |url=http://www.adfg.alaska.gov/index.cfm?adfg=bluekingcrab.main |accessdate=18 November 2018 |work=Species Profiles |publisher=Alaska Department of Fish and Game}} Additionally, a second, separate population exists in the Norton Sound all the way to St. Lawrence Island. Blue king crabs have a more northerly distribution compared to red king crabs, which is due to the colder waters of the northern Bering Sea being suitable for blue king crabs to survive.{{cite report |url=http://www.data.boem.gov/PI/PDFImages/ESPIS/0/418.pdf |title=Distribution & Abundance of decapod larvae in the southeastern Bering Sea with emphasis on commercial species |last1=Armstrong |first1=David |last2=Incze |first2=Lewis S. |date=1981 |publisher=University of Washington School of Fisheries |page=548 |last3=Wencker |first3=Deborah L. |last4=Armstrong |first4=Janet L. |archive-url=https://web.archive.org/web/20170131202429/https://www.data.boem.gov/PI/PDFImages/ESPIS/0/418.pdf |archive-date=31 January 2017 |url-status=dead |accessdate=8 December 2015}} Their limited distribution is hypothesized to have been caused by a retreat into deeper, colder waters during a period of post-glacial warming. The hypothesis additionally suggests that the cause of P. platypus' disjunct distribution within Alaska was caused by a dramatic contraction of their population during the warmer post-glacial period.

Female blue king crabs migrate seasonally from depths of {{convert|130–180|m|ft|abbr=on}} in winter to shallow depths of {{convert|6–10|m|ft|abbr=on}} for females with eggs and {{convert|50–80|m|ft|abbr=on}} for females without eggs.{{cite book |last1=Pereladov |first1=Mikhail V. |url= |title=Crabs in cold water regions: Biology, management and economics |last2=Miljutin |first2=Dmitry M. |date=January 2002 |publisher=University of Alaska Sea Grant College Program |isbn=1-56612-077-2 |editor-last1=Paul |editor-first1=A.J. |pages=511–520 |chapter=Population structure of blue king crab (Paralithodes platypus) in the northwestern Bering Sea |doi=10.4027/ccwrbme.2002.37 |id=Ak-SG-02-01 |editor-last2=Dawe |editor-first2=Earl G. |editor-last3=Elner |editor-first3=Robert |editor-last4=Jamieson |editor-first4=Glen S. |editor-last5=Kruse |editor-first5=Gordon H. |editor-last6=Otto |editor-first6=Robert S. |editor-last7=Sainte-Marie |editor-first7=Bernard |editor-last8=Shirley |editor-first8=Thomas C. |editor-last9=Woodby |editor-first9=Douglas |display-editors=1 |chapter-url=https://www.researchgate.net/publication/267321498 |via=ResearchGate}} The average depth for male crabs of commercial size is {{convert|70|m|ft|abbr=on}},{{cite journal | author1 = North Pacific Fishery Research Council | year = 2005 | title = Essential Fish Habitat Assessment Report for the Bering Sea and Aleutian Islands King and Tanner Crabs | journal = NOAA Fisheries Report | url = http://www.fakr.noaa.gov/habitat/seis/final/Volume_II/Appendix_F.3.pdf | url-status = dead | archiveurl = https://web.archive.org/web/20100528050924/http://www.fakr.noaa.gov/habitat/seis/final/Volume_II/Appendix_F.3.pdf | archivedate = 2010-05-28 }} although crabs can commonly be caught at shallower depths in winter.{{Citation needed|date=September 2024}}

Pribilof Island blue king crabs mate and produce eggs in late March to early May.{{cite journal |last1=Somerton |first1=David A. |last2=MacIntosh |first2=Richard A. |date=July 1985 |title=Reproductive biology of the female blue king crab Paralithodes platypus near the Pribilof Islands, Alaska |url=https://zenodo.org/record/1235081 |journal=Journal of Crustacean Biology |volume=5 |issue=3 |pages=365–376 |doi=10.2307/1547908 |jstor=1547908|bibcode=1985JCBio...5..365S }} Females generally brood their eggs externally for 12–14 months.{{cite journal |last1=Jensen |first1=Gregory C. |last2=Armstrong |first2=David A. |date=June 1989 |title=Biennial reproductive cycle of blue king crab, Paralithodes platypus, at the Pribilof Islands, Alaska and comparison to a congener Paralithodes camtschatica |url=https://www.researchgate.net/publication/237183192 |journal=Canadian Journal of Fisheries and Aquatic Sciences |volume=46 |issue=6 |pages=932–940 |doi=10.1139/f89-120 |bibcode=1989CJFAS..46..932J |via=ResearchGate}}{{cite journal |last=Stevens |first=Bradley G. |date=October 2006 |title=Timing and duration of larval hatching for blue king crab Paralithodes platypus Brandt, 1850 held in the laboratory |journal=Journal of Crustacean Biology |volume=26 |issue=4 |pages=495–502 |doi=10.1651/S-2677.1 |jstor=4094179 |doi-access=free|bibcode=2006JCBio..26..495S }} Since blue king crabs need more than a year to brood their eggs, they miss a breeding cycle just before the larvae hatch and only produce eggs every other year, although first-time breeders can often produce eggs in subsequent years. Females release larvae around the middle of April in the Pribilof Islands, while those held at warmer temperatures in the laboratory may release larvae as early as February.

Female blue king crabs in the Pribilof Islands grow to the largest size before they are reproductively mature. About 50% of crabs are mature at {{convert|5|in|abbr=on}} CL. St. Matthew Island females can become sexually mature at {{convert|3|in|abbr=on}} CL,{{cite journal | author = Somerton, D. A. | author2 = R. A. MacIntosh | year = 1983 | title = The size at sexual maturity of blue king crab, Paralithodes platypus, in Alaska | journal = Fishery Bulletin | volume = 81 | issue = 3 | pages = 621–628}} and Diomede crabs are similar. Larger female crabs from the Pribilof Islands have the highest fecundity, producing 162,360 eggs or 110,033 larvae per crab. The reduction in fecundity is about 33% between the egg and larval stages. In Japan, an average of 120,000 larvae were released from each blue king crab.{{cite journal | author = Sasakawa, Y. | year = 1973 | title = Studies on blue king crab resources in the western Bering Sea — III: Ovarian weight, carried egg number and diameter | journal = Bulletin of the Japanese Society of Scientific Fisheries | volume = 41 | issue = 9 | pages = 941–944| doi = 10.2331/suisan.41.941 | doi-access = free }} Diomede blue king crabs release an average of 60,000 larvae per female.

Environmental variables, such as tides, temperature, salinity, light, phytoplankton blooms, and predation, are seasonally pulsed and likely serve as cues for larval release.{{cite journal | doi = 10.1080/10236248909378738 | author = Shirley, T. C. | author2 = S. M. Shirley | year = 1989 | title = Temperature and salinity tolerances and preferences of red king crab larvae | journal = Marine Behaviour and Physiology | volume = 16 | issue = 1 | pages = 19–30}}{{cite book | author = Morgan, S. G. | year = 1995 | chapter= The timing of larval release | editor= L. R. McEdward |title=Ecology of marine invertebrate larvae | publisher= CRC Press |location=Boca Raton, FL | pages = 157–191 |isbn=978-0-8493-8046-4}} Release of larvae over a longer period may serve to give the female a larger window for larvae to correspond with any favorable environmental conditions that may exist, also known as “bet-hedging”.{{cite journal | author = Slatkin, M. | year = 1974 | title = Hedging one's evolutionary bets | journal = Nature | volume = 250 | pages = 704–705 |doi=10.1038/250704b0 | issue=5469| bibcode = 1974Natur.250..704S | s2cid = 38185482 }} In the laboratory, Pribilof larvae hatch over the course of about one month,{{cite journal | author = Stevens, B. G. | year = 2006 | title = Embryo development and morphometry in the blue king crab Paralithodes platypus studied by using image and cluster analysis | journal = Journal of Shellfish Research | volume = 25 | issue = 2 | pages = 569–576 | url = http://doc.nprb.org/web/publication/project_0316_stevens_jsr_2006.pdf | archive-url = https://web.archive.org/web/20110727132124/http://doc.nprb.org/web/publication/project_0316_stevens_jsr_2006.pdf | url-status = dead | archive-date = 2011-07-27 | doi = 10.2983/0730-8000(2006)25[569:EDAMIT]2.0.CO;2 }} and Diomede larvae hatch over the course of 2–3 weeks. These differences may be due to water temperature in the laboratory, which has a clear effect on embryonic and larval development, and is probably slightly different from hatch timing in a natural environment.

Commercial blue king crab fisheries around the eastern Bering Sea began in the mid-1960s. Over {{convert|13228000|lb|t}} of blue king crabs were caught during 1981, the peak for blue king crab fisheries as well as the year after red king crab fisheries peaked.{{cite journal |last1=Zheng |first1=Jie |last2=Kruse |first2=Gordon H. |year=2000 |title=Recruitment patterns of Alaskan crabs in relation to decadal shifts in climate and physical oceanography |journal=ICES Journal of Marine Science |volume=57 |issue=2 |pages=438–451 |bibcode=2000ICJMS..57..438Z |doi=10.1006/jmsc.1999.0521 |doi-access=free}}{{cite report |url=https://www.adfg.alaska.gov/fedaidpdfs/FMR08-73.pdf |title=Annual management report for the commercial and subsistence shellfish fisheries of the Aleutian Islands, Bering Sea and the westward region's shellfish observer program, 2007-2008 |last1=Bowers |first1=Forrest R. |last2=Schwenzfeier |first2=Mary |date=December 2008 |publisher=Alaska Department of Fish and Game |volume=269 |id=No. 08-73 |last3=Milani |first3=Krista |last4=Salmon |first4=Melissa |last5=Herring |first5=Kathleen |last6=Shaishnikoff |first6=Janis |last7=Russ |first7=Elisa |last8=Burt |first8=Ryan |last9=Barnhart |first9=Heather |display-authors=1}} The Pribilof Island harvest by the United States peaked in 1980 at {{convert|10935000|lb|t|abbr=on}} and was closed in 1988 due to population decline,{{cite journal | author = Zheng, J. | author2 = M. C. Murphy| year = 1997 | title = Application of a catch-survey analysis to blue king crab stocks near Pribilof and St. Matthew Islands | journal = Alaska Fishery Research Bulletin | volume = 4 | issue = 1 | pages = 62–74 |url=http://www.adfg.state.ak.us/pubs/afrb/vol4_n1/zhenv4n1.pdf|display-authors=etal}} then again in 1999 after being opened for three years.{{cite journal | author = Chilton, E. A. | author2 = C. E. Armistead| year = 2008 | title = The 2008 Eastern Bering Sea Continental Shelf Bottom Trawl Survey: Results for Commercial Crab Species | journal = NOAA Fisheries Report |url=http://www.afsc.noaa.gov/Publications/AFSC-TM/NOAA-TM-AFSC-187.pdf|display-authors=etal}} The St. Matthew fishery peaked in 1983 with {{convert|9453500|lb|t|abbr=on}} but experienced a similar decline and was closed in 1999. It was opened in 2009, and was featured on the television show Deadliest Catch. The St. Matthew stock is rebuilding but the fishery remains closed, while the Pribilof stock has not drastically improved. Diomede blue king crabs have never been harvested commercially, but support a subsistence fishery for the Native Village of Diomede, Alaska, population 170.

Colder water slows the rate of crab growth and crabs at northern latitudes are often smaller than more southern crabs. Commercial harvest of blue king crabs at the Pribilof Islands is limited to males with a carapace width (CW) over {{convert|6.5|in|cm|abbr=on}} and St. Matthew Island is limited to crabs with CW greater than {{convert|5.5|in|cm|abbr=on}},{{cite journal | author = Alaska Department of Fish and Game | year = 1998 | title = 1998-1999 commercial shellfish fishing regulations | journal = Alaska Department of Fish and Game, Juneau, Alaska | volume = 163 | author-link = Alaska Department of Fish and Game }} corresponding to crabs over {{convert|4.7|in|cm|abbr=on}} carapace length (CL).{{cite report |url=http://www.afsc.noaa.gov/Publications/ProcRpt/PR%202001-07.pdf |title=Report to Industry on the 2001 Eastern Bering Sea Crab Survey |last1=Rugolo |first1=Louis J. |last2=Haaga |first2=Jan A. |date=December 2001 |publisher=Alaska Fisheries Science Center |last3=MacIntosh |first3=Richard A. |id=AFSC Processed Report 2001-07}} Diomede blue king crabs are similar in size to St. Matthew Island crabs.

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{{cite WoRMS |title=Paralithodes platypus (J.F. Brandt in von Middendorf, 1851) |year=2020 |id=254493 |access-date=1 November 2020}}

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{{Lithodidae}}

{{Edible crustaceans}}

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Category:King crabs

Category:Edible crustaceans

Category:Commercial crustaceans

Category:Crustaceans of the eastern Pacific Ocean

Category:Anomura of the Pacific Ocean

Category:Crustaceans of the United States

Category:Crustaceans of Russia

Category:Crustaceans described in 1851

Category:Taxa named by Johann Friedrich von Brandt