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{{Redirect|Polar cod|the related species which shares its common names|Arctogadus glacialis}}{{In use|time=08:35, 13 November 2024 (UTC)}}{{Speciesbox
| image = Boreogadus saida.jpg
| status = Highly Threatened
| status_system = Norwegian Red List
| genus = Boreogadus
| status_ref =
| parent_authority = [[Albert Günther|Günther]], 1862
| species = saida
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*''Pollachius polaris'' <small>(Sabine, 1824)</small>
*''Gadus fabricii'' <small>[[John Richardson (naturalist)|Richardson]], 1836</small>
*''Gadus agilis'' <small>[[Johan Reinhardt|Reinhardt]], 1837</small>
}}
'''''Boreogadus saida''''', known as the '''polar cod'''<ref name="FB">{{FishBase|Boreogadus|saida| month = April | year = 2012}}</ref><ref name="FAO">{{cite book | editor1 = Daniel M. Cohen | editor2 = Tadashi Inada | editor3 = Tomio Iwamoto | editor4 = Nadia Scialabba | name-list-style = amp | year = 1990 | title = FAO species catalogue. Vol. 10. Gadiform fishes of the world (Order Gadiformes). An Annotated and Illustrated Catalogue of Cods, Hakes, Grenadiers and other Gadiform Fishes Known to Date | publisher = [[Food and Agriculture Organization]] of the United Nations | isbn = 978-92-5-102890-2 | pages = 27–29 | url = http://www.fao.org/3/t0243e/t0243e00.htm }}</ref><ref>[http://www.imr.no/temasider/fisk/torsk/polartorsk/en Polar cod] Institute of Marine Research, Norway</ref> or as the '''Arctic cod''',<ref name="FB" /><ref>[http://www.arcodiv.org/seaice/arctic_cod/Boreogadus_saida.html Arctic Cod: ''Boreogadus saida''] Arctic Ocean Diversity. Census of Marine Life.</ref><ref>[http://www.dfo-mpo.gc.ca/species-especes/aquatic-aquatique/arctic-cod-eng.htm Arctic Cod] {{webarchive |url=https://web.archive.org/web/20111122214847/http://www.dfo-mpo.gc.ca/species-especes/aquatic-aquatique/arctic-cod-eng.htm |date=November 22, 2011 }} Aquatic species. Fisheries and Oceans Canada.</ref> is a fish of the cod [[Family (biology)|family]] [[Gadidae]], related to the true [[cod]] (genus ''Gadus''). Another fish species for which both the common names Arctic cod and polar cod are used is ''[[Arctogadus glacialis]]''.
== Species Description ==
[[File:Boreogadus saida morphotypes.png|alt=The image shows a close-up view of five Boreogadus saida lying horizontally in a pile within a plastic basket with orange slats. Each fish has a number label placed above it, ranging from 1 to 5, helping distinguish them from one another. These fish appear similar in shape and color, with silvery bodies, large eyes, and prominent mouths. However, the top three fish, labelled 1 to 3, are slightly darker in color. The bottom two fish, labelled 4 to 5, are slightly lighter in color and smaller.|thumb|Dark (1,2,3) and Light (4,5) [[Polymorphism (biology)|morphotypes]] described by Inuit fishers<ref name=":0" />.|259x259px|left]]Arctic cod have slender bodies, deeply forked tails, a projecting mouth, and a small chin [[Barbel (anatomy)|barbel]].
Arctic cod are frequently misidentified as polar cod ([[Arctogadus glacialis]]) during their larval and early juvenile stages. The species can be differentiated through the analysis of [[Otolith|otoliths]] or molecular data.<ref>{{Cite journal |last1=Bouchard |first1=Caroline |last2=Mollard |first2=Salomé |last3=Suzuki |first3=Keita |last4=Robert |first4=Dominique |last5=Fortier |first5=Louis |date=2016-06-01 |title=Contrasting the early life histories of sympatric Arctic gadids Boreogadus saida and Arctogadus glacialis in the Canadian Beaufort Sea |url=https://link.springer.com/article/10.1007/s00300-014-1617-4 |journal=Polar Biology |language=en |volume=39 |issue=6 |pages=1005–1022 |doi=10.1007/s00300-014-1617-4 |bibcode=2016PoBio..39.1005B |issn=1432-2056}}</ref>
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Arctic cod grow to an average length of 25 cm (9.8 in), and a maximum length of {{convert|40|cm|in|abbr=on}}<ref name="FAO" />.
== Geographical Distribution ==
[[File:Boreogadus Saida geographical distribution.png|thumb|340x340px|Geographical distribution of Arctic cod.<ref name="FAO" />]]▼
This species is found further north than any other fish<ref>Christiansen JS (2012): TUNU Programme: Euro-Arctic marine fishes - Adaptation and evolution. pp 35-50. In: Adaptation and Evolution in Marine Environments, Vol. 1: The Impacts of Global Change on Biodiversity. Springer-Verlag, Berlin Heidelberg.</ref>
Arctic cod exhibit [[diel vertical migration]] patterns during winter and spring, but migration is not observed during summer.<ref name=":0" />
== Habitat ==
Early life stages of Arctic cod are found near the surface in both ice-covered and open water; however, adults are found deeper in the water column.<ref name=":1">{{Cite journal |last1=Geoffroy |first1=Maxime |last2=Bouchard |first2=Caroline |last3=Flores |first3=Hauke |last4=Robert |first4=Dominique |last5=Gjøsæter |first5=Harald |last6=Hoover |first6=Carie |last7=Hop |first7=Haakon |last8=Hussey |first8=Nigel E. |last9=Nahrgang |first9=Jasmine |last10=Steiner |first10=Nadja |last11=Bender |first11=Morgan |last12=Berge |first12=Jørgen |last13=Castellani |first13=Giulia |last14=Chernova |first14=Natalia |last15=Copeman |first15=Louise |date=2023-08-08 |title=The circumpolar impacts of climate change and anthropogenic stressors on Arctic cod ( Boreogadus saida ) and its ecosystem |url=https://online.ucpress.edu/elementa/article/11/1/00097/196994/The-circumpolar-impacts-of-climate-change-and |journal=Elem Sci Anth |language=en |volume=11 |issue=1 |page=00097 |doi=10.1525/elementa.2022.00097 |bibcode=2023EleSA..11...97G |issn=2325-1026}}</ref> In the [[Canadian Arctic]], Arctic cod will separate vertically in the water column by size, with younger fish in the upper 100 meters of the water column, and juvenile and immature fish below 200 meters.<ref name=":2">{{Cite journal |last1=Herbig |first1=Jennifer |last2=Fisher |first2=Jonathan |last3=Bouchard |first3=Caroline |last4=Niemi |first4=Andrea |last5=LeBlanc |first5=Mathieu |last6=Majewski |first6=Andrew |last7=Gauthier |first7=Stéphane |last8=Geoffroy |first8=Maxime |date=2023-09-22 |title=Climate and juvenile recruitment as drivers of Arctic cod ( Boreogadus saida ) dynamics in two Canadian Arctic seas |url=https://online.ucpress.edu/elementa/article/11/1/00033/197376/Climate-and-juvenile-recruitment-as-drivers-of |journal=Elem Sci Anth |language=en |volume=11 |issue=1 |page=00033 |doi=10.1525/elementa.2023.00033 |bibcode=2023EleSA..11...33H |issn=2325-1026}}</ref>
Arctic cod can also be found in dense schools near glacial fronts and [[Polynya|polynyas]].<ref name=":0" /> Subsurface plumes of freshwater discharged from glaciers create foraging hotspots, aggregating [[zooplankton]] where they are stunned or killed by [[osmotic shock]], making them easy prey for Arctic cod.<ref name=":0" /> Greenlandic Inuit fishers have reported the presence of Arctic cod near the [[Sermilik Glacier|Sermilik]] and Sermeq Avannarleq glaciers, located off the southwestern coast of [[Greenland]].<ref name=":0" />
== Reproduction and Life Stages ==
▲[[File:Boreogadus Saida geographical distribution.png|thumb|340x340px|Geographical distribution of Arctic cod.<ref name="FAO" />]]
Arctic cod have multiple reproductive cycles throughout their lives.<ref name=":1" /> Arctic cod are an [[R/K selection theory|r-selected]] species, meaning they reach maturity early and produce high numbers of offspring. On average, a female will lay between 9,000 to 21,000 eggs.<ref name="FAO" /> Spawning occurs between September and April, and peaks between January and February.<ref name=":1" /> Spawning locations are not fully known, but spawning is suggested to occur in the [[Barents Sea|Barens Sea]] to the southwest of the Svalbard Island chain, and the [[Kara sea|Kara]] and [[Pechora Sea|Pechora]] seas.<ref name=":1" /> In the [[Northern Canada|Canadian Arctic]], spawning is suggested to occur near the [[Franklin Bay|Franklin]] and [[Darnley Bay|Darney]] bays. In the Pacific Arctic, spawning is suggested to occur in the northern [[Bering Sea]], [[Chukchi Sea]], and [[Kotzebue Sound]]. Greenlandic Inuit fishers have noted a spawning area near [[Saattut|Saattut Island]].<ref name=":0" />
[[File:Boreogadus saida larvae.png|thumb|235x235px|Larvae of Arctic cod, total length 15.0-23.5 mm, from [[Severnaya Zemlya]], [[Mikoyan Bay]].<ref>{{Cite journal |last=Chernova |first=N.V. |last2=Spiridonov |first2=V.A. |last3=Syomin |first3=V.L. |last4=Gavrilo |first4=M.V. |date=2021-06-25 |title=Notes on the fishes of the Severnaya Zemlya archipelago and the spawning area of polar cod Boreogadus saida (Gadidae) |url=https://www.zin.ru/journals/trudyzin/eng/publication.html?id=438 |journal=Proceedings of the Zoological Institute RAS |language=ru |volume=325 |issue=2 |pages=248–268 |doi=10.31610/trudyzin/2021.325.2.248 |issn=0206-0477}}</ref>]]
The development and viability of Arctic cod eggs depend heavily on temperature. Eggs develop normally between -1.5ºC and 3ºC; however, hatching success severely declines above 2ºC.<ref name=":1" /> Incubation time decreases as temperatures increase: at 1.5ºC, it will take 79 days for larvae to hatch, but at 3.8ºC, incubation time decreases to 29 days.<ref name=":1" /> In the [[Northern Canada|Canadian Arctic]], Arctic cod hatch under the ice from January to July and remain under the ice until
[[File:Life Cycle of Boreogadus Saida within a year.png|thumb|445x445px|Life Cycle of Arctic cod in a year.<ref>{{Cite journal |last1=Geoffroy |first1=Maxime |last2=Bouchard |first2=Caroline |last3=Flores |first3=Hauke |last4=Robert |first4=Dominique |last5=Gjøsæter |first5=Harald |last6=Hoover |first6=Carie |last7=Hop |first7=Haakon |last8=Hussey |first8=Nigel E. |last9=Nahrgang |first9=Jasmine |last10=Steiner |first10=Nadja |last11=Bender |first11=Morgan |last12=Berge |first12=Jørgen |last13=Castellani |first13=Giulia |last14=Chernova |first14=Natalia |last15=Copeman |first15=Louise |date=2023-08-08 |title=The circumpolar impacts of climate change and anthropogenic stressors on Arctic cod ( Boreogadus saida ) and its ecosystem |url=https://online.ucpress.edu/elementa/article/11/1/00097/196994/The-circumpolar-impacts-of-climate-change-and |journal=Elem Sci Anth |language=en |volume=11 |issue=1 |page=00097 |doi=10.1525/elementa.2022.00097 |bibcode=2023EleSA..11...97G |issn=2325-1026}}</ref>]]
Arctic cod larvae can be between 3.5mm and 7mm after hatching; however, in experimental settings, length after hatching decreases when temperatures increase. The larvae have a higher temperature tolerance range than the eggs. Larvae are [[euryhaline]], meaning that they can withstand different salinity concentrations.<ref name=":1" /> Therefore, they can be found in areas with [[Meltwater|glacial meltwater]], in river mouths, or in ice-covered areas. The larger the larvae is, the higher the chance of survival it has, especially during the transition between yolk feeding to exogenous feeding.<ref name=":1" />
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