Diversity of fish
Fish are very diverse animals and can be categorised in many ways. This article is an overview of some of ways in which fish are categorised. Although most fish species have probably been discovered and described, about 250 new ones are still discovered every year. According to FishBase, 33,100 species of fish had been described by April 2015. That is more than the combined total of all other vertebrate species: mammals, amphibians, reptiles and birds.