Fish is the oldest vertebrate. The offspring of the hybridization  of some different chromosome Numbers are still fertile. They inhabit almost all aquatic environments on earth, from freshwater lakes and rivers to salty seas and oceans. Fish is a variable temperature vertebrate that lives in water all year round, breathing through gills, supporting body balance and movement with its fins. According to statistics Canada scholars, late global living species of fish, 24618 kinds, accounted for more than half the named vertebrates, and new species of fish have been found, on average every year to about 150 meter, more than 10 years has increased more than 1500 kinds, at present, the world has about 32100 species of named species. It is the most primitive and common group of vertebrate submen.