ABSTRACT
There are sizeable numbers of species in four of the vertebrate classes: Amphibia 4300; Reptilia 6000; Aves 9000; Mammalia 8000. These are all round numbers, but, even so, they are almost certainly unlikely to be added to significantly by the discovery of new species. More likely, extinction (often our fault by habitat reduction) will reduce them. But the fish class “Pisces” is different to the others, on two counts. First, there are more kinds of fish than all other vertebrates added together. So far, over 25 000 different species of fish are known, and around 100 more are described each year, so that the final total may well exceed 30 000. The great majority are bony teleosts, the cartilaginous elasmobranchs coming a very poor second with just over 800 species. All other fish groups have insignificant numbers of species, although they may be of great zoological interest, and sometimes, as are the sturgeons, of considerable gastronomic and economic importance.
