Why are many Antarctic bottom fish found nowhere else on Earth?

Many Antarctic bottom fish are found nowhere else on Earth because they are highly endemic, a fact that supports biological and geological evidence indicating that Antarctica has been isolated for a very long time.1

This long-term isolation has limited the exchange of species with other regions, allowing for the development of unique evolutionary adaptations to the continent's extreme, cold environment. For instance, many of these fishes belong to the superfamily Notothenioidea, which has evolved specialized physiological traits to survive in freezing waters, such as the production of glycoproteins that act as cryoprotectants to prevent ice crystal formation in their tissues.1234

Because these species have evolved in such a distinct and isolated habitat, they have become highly specialized, resulting in approximately 90 percent of the sea-bottom fish species in the region being found exclusively in Antarctic waters.1