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).[1] 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.