Antarctic fishes

Antarctic fishes are a relatively limited but highly specialized group of species adapted to extreme cold in the Southern Ocean. Many belong to the “white-blooded” icefish group, such as the mackerel icefish that lack 'hemoglobin" and thus have colorless blood, a feature that is unique to this region. Other abundant types include ‘Antarctic cods’ though they are not true cods which possess antifreeze glycoproteins in their blood allowing them to survive in waters below the normal freezing point. Large species such as the Antarctic toothfish can grow up to two meters and live for decades, and inhabit depths from 100 meters to 3,000 meters, feeding on fish, squid and benthic crustaceans. Conservation concerns around the toothfish have required international regulation because of historical illegal, unreported and unregulated fishing, which once far exceeded legal catches in the region.

Antarctic fish is a common name for a variety of fish that inhabit the Southern Ocean. There are relatively few families in this region, the most species-rich being the Liparidae (snailfishes), followed by Nototheniidae (cod icefishes). The latter is one of eight different families that belong to the suborder Notothenioidei of the order Perciformes. They are also called notothenioids, but this name is also used to describe the other three, non-Antarctic families and some of the non-Antarctic genera in the mainly Antarctic families belonging to the suborder.

Antarctic fish are best known for their uses in studying adaptive radiation, the ecological process that causes the rapid development of several different species from one common ancestor of this fishes. These studies have been done using genetics, phylogeny, study of paleontology, and combinations of these fields to determine the sister lineage of the Antarctic fish.