Boreogadus

Arctic cod have slender bodies, deeply forked tails, a projecting mouth, and a small chin barbel.

[6] 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.

[6] Arctic cod have several adaptations that allow them to function in freezing polar waters where most other species could not.

These waters, though incredibly cold, have a lower freezing point due to their high salt content.

[12] The key adaptation that allow for a decrease in their freezing point lies in their blood: specifically, high molecular mass antifreeze glycoproteins.

Antifreeze glycoproteins first occurred about 5 to 15 million years ago, coinciding with the freezing of the Antarctic Ocean.

Arctic cod have antifreeze glycoprotein genes that are similar to other notothenioid Antarctic fish, however, the protein-coding sequences are not identical.

This suggests that the ability to produce antifreeze glycoproteins evolved independently in both fish, showing convergent evolution due to similar cold environments.

Arctic cod have unique kidneys that lack glomeruli, structures found in most organisms that filter out toxins from the blood.

[13] This adaptation, shared with Antarctic notothenioid fish, help the cod retain vital antifreeze glycoproteins in their blood.

It also prevents the fish from experiencing osmotic stress, as the high salt content of the Arctic Oceans draws water out of their bodies.

[10] To withstand short summer growing seasons, Arctic cod juveniles enter winter with higher lipid concentrations compared to boreal species.

[10] Arctic cod are an r-selected species, meaning they reach maturity early and produce high numbers of offspring.

[10] Juvenile Arctic cod are found in the pelagic zone of the water column and descend deeper after their first summer.

[6] Greenlandic Inuit fishers locate schools of Arctic cod by observing the movements of predators in combination with the use of sonar.

[6] Arctic cod is caught as bycatch in bottom trawls used for Greenland halibut and northern and striped shrimp fishing.

[10] Their larvae must be in 3 °C to hatch normally, and a rise in ocean temperatures can easily lead to phenotypic changes of this cod species.

Arctic cod eggs will be increasingly exposed to UV radiation, turbulence and temperature changes, which could affect mortality.

Climate change will also affect the primary production and availability of Arctic cod prey.

This change will be favorable for young Arctic cod, but inter-annual variability in primary production might lead to different long-term outcomes.

Less sea ice will lead to increased anthropogenic activities in the Arctic, especially commercial shipping.

With shipping comes the possibility of oil spills, which will also affect Arctic cod as they lack glomeruli to filter out toxins from their blood.

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.
Dark (1,2,3) and Light (4,5) morphotypes described by Inuit fishers. [ 6 ]
Geographical distribution of Arctic cod. [ 2 ]
An Arctic Cod rests in an ice-covered space. Alaska, Beaufort Sea , North of Point Barrow .
Diagram of B. saida's (in this diagram, labeled polar cod) marine food web and the shift towards Subarctic as B. saida populations decrease, with indicated links and trophic levels (TL-1 to -4). Thickness of arrows indicates relative importance of energy flow based on known stomach content of predators [ 14 ]
Larvae of Arctic cod, total length 15.0-23.5 mm, from Severnaya Zemlya , Mikoyan Bay . [ 17 ]
Life Cycle of Arctic cod in a year. [ 10 ]
Arctic cod frozen at sea from a Russian vessel. Typically 10 or 16 kg net weight.
Uummannaq fishers preparing their longlines onboard dinghies used for Greenland halibut fishing, July 2022. The same dinghies are used for Arctic cod fishing, with nets instead of longlines. [ 6 ]