Fish
Mackerel Icefish
Champsocephalus gunnari · also called Antarctic icefish
Carrying blood so pale it runs almost clear, a mackerel icefish survives the freezing Southern Ocean without haemoglobin at all, a physiological trick shared only by its icefish relatives, though decades of heavy fishing have left its population still recovering under strict modern quotas.
Overview
The mackerel icefish, Champsocephalus gunnari, is a Near Threatened fish native to ocean and polar habitat across the Southern Ocean continental shelf, concentrated around South Georgia, Kerguelen, and the Antarctic Peninsula. Its haemoglobin-free blood, history as one of the most heavily fished icefish species, and antifreeze-protected physiology make it one of the more scientifically and economically significant fish species found anywhere in Antarctic waters.
A fishery that nearly collapsed its own target
Before strict international quotas were introduced, unregulated fishing fleets targeted the mackerel icefish so intensively around its main breeding grounds that populations crashed within a matter of years, a cautionary tale now cited whenever new Southern Ocean fisheries are proposed.
Status
Near Threatened, having collapsed sharply under unregulated commercial fishing in past decades and remaining below historic levels despite recovery efforts under strict modern catch quotas.
Mackerel Icefish: common questions
Why is the mackerel icefish's blood almost clear?
This species lacks haemoglobin entirely, like all icefish, leaving its blood nearly colourless and relying instead on oxygen dissolved directly in its plasma rather than carried by red blood cells.
Why is the mackerel icefish managed under fishing quotas?
This species was historically one of the most heavily targeted icefish species by commercial fisheries, and unregulated catches caused sharp population collapses before strict international quotas were introduced.
How does the mackerel icefish survive freezing Antarctic water?
This species produces antifreeze glycoproteins in its blood and tissues, preventing ice crystals from forming even in the sub-zero temperatures typical of the Southern Ocean continental shelf.
Where is the mackerel icefish found?
This species is native to ocean and polar habitat across the Southern Ocean continental shelf, concentrated most heavily around South Georgia, the Kerguelen Plateau, and the Antarctic Peninsula.