1. A fish is an animal which lives and breathes in water. All fish are vertebrates (have a backbone) and most breathe through gills and have fins and scales. Fish make up about half of all known vertebrate species. Fish have been on the earth for more than 500 million years. Fish were well established long before dinosaurs roamed the earth.
2. The 25,000 known species of fish are divided into three main groups. There are three classes of fish: jawless, cartilaginous, and bony. All fish have a backbone. It is estimated that there may still be over 15,000 fish species that have not yet been identified. There are more species of fish than all the species of amphibians, reptiles, birds and mammals combined.
3. Fish are cold-blooded, which means their internal body temperature changes as the surrounding temperature changes.
4. 40% of all fish species inhabit fresh water, yet less than .01% of the earth's water is fresh water. Tropical fish are one of the most popular pets in the U.S.
5. Some fish like sharks don't possess an air bladder to help keep them afloat and must either swim continually or rest on the bottom. Some species of fish can fly (glide) others can skip along the surface and others can even climb rock. Fish have a specialized sense organ called the lateral line which works much like radar and helps them navigate in dark or murky water.
6. The largest fish is the great whale shark which can reach fifty feet in length. The smallest fish is the Philippine goby that is less than 1/3 of an inch when fully grown.
7. Fish have excellent senses of sight, touch, taste and many possess a good sense of smell and 'hearing’. Fish feel pain and suffer stress just like mammals and birds.
8. Fish eat other fish, fish eggs, mollusks, aquatic plants, algae, zooplankton, terrestrial insects, water birds, turtles, frogs, snakes and mice
9. A person who studies fish called an ichthyologist.
10. In some species the males and females have different shaped bodies or different coloring; in other species there is no visible difference.