Fish Tries To Get Oxygen, St. Petersburg, Russia

For example, the Antarctic icefish belong to the perciform suborder Notothenioidei and are the largely endemic, dominant fish taxa in the cold continental shelf waters surrounding Antarctica. At present, the suborder includes 8 families with 43 genera and 122 species. Although the Southern Ocean is relatively well sampled, new species of notothenioids are still being described.
The majority of Notothenioids live at seawater temperatures between of –2°C and 4°C, but some sub-polar species inhabit waters that may be as warm as 10°C around New Zealand and South America. It is possible to have seawater temperatures below the freezing point of fresh water (0°C) because dissolved salts lower the freezing point of a solution in a colligative manner.
The notothenioids all lack a swimbladder, and the majority of species are therefore benthic or demersal in nature. However, a depth-related diversification has given rise to some species attaining increased buoyancy, using lipid deposits in tissues and reduced ossification of bony structures.