Deep sea represents extreme environment due to high pressure and lack of sun light. No matter to those conditions, which are extreme for humans, some fish were able to adjust their living in deep sea environment and it became normal way of life for them. Deep sea zone shows poor biomass regarding the species diversity, but looking through biological performances it has very interesting fauna. Thousands of meters below the surface, the pressure is one hundred times higher than on the surface. Most featured characteristics of deep sea fishes are capability of bioluminescence, big or stunted eyes, slow metabolism and big jaws.

Duboko more predstavlja ekstreman okoliš zbog nedosatka svijetla i visokog tlaka. Bez obzira na navedene uvjete koji su ekstremni za čovjeka, neke ribe su se uspjele prilagoditi i život u dubokomorskom okolišu za njih je normalan život. Zona dubokih voda pokazuje po vrstama i biomasi siromašnu, ali po biologijskim osobinama vrlo zanimljivu dubokomorsku faunu. Tisuću metara ispod površine vode tlak je 100 puta veći nego na površini. Najistaknutije karakteristike dubokomorskih riba su sposobnost bioluminiscencije, velike ili zakržljale oči, usporen metabolizam, velike čeljusti.