Fish

Fish is a member of vertebrates poikilotermik (cold-blooded) that live in water and breathe with gills. The fish are more different species of vertebrates more than 27,000 worldwide. In the standings, the fish belonging to the paraphyletic group relationship is still debated, generally divided into fish without jaws fish (class Agnatha, 75 species of fish including Harpies lampreys), cartilaginous fishes (class Chondrichthyes, 800 species, including sharks and rays ), and the rest are classified as hard bony fish (class Osteichthyes).

Fish can be found in almost all the "puddle" of water that are large both freshwater, brackish water or salt water at varying depths, from near surface to several thousand meters below the surface. However, hyper-saline lakes like the Great Salt Lake do not support fish. There are several species of fish cultivated for maintained to be exhibited in the aquarium.

Fish are an important food source. Other aquatic animals, such as molluscs and crustaceans also sometimes regarded as a fish when used as a food source. Catch fish for food in small quantities or sports are often referred to as fishing. Results of fishing the world each year approximately 100 million tons.