These are some interesting facts about fish. Fish have been on the earth for more than 450 million years. Fish were well established long before dinosaurs roamed the earth. They are here before and after the extinction of the dinosaurs. I guess they are intelligent than the dinosaurs too. There are over 25,000 identified species of fish on the earth. It is estimated that there may still be over 15,000 fish species that have not yet been identified. These are truly beautiful creatures. Maybe that's why some men would rather be photographed with their fish than their wives.