All fish share two traits: they live in water and they have a backbone—they are vertebrates.

Is fish an invertebrate?

The animal kingdom can be split into two main groups: vertebrates and invertebrates. Vertebrates such as mammals, fish, birds, reptiles and amphibians all have a backbone, whereas invertebrates, such as butterflies, slugs, worms, and spiders, don't.

Do fish have backs?

Dorsal fins: Located on the back of the fish, dorsal fins serve to prevent the fish from rolling and assist in sudden turns and stops. Most fishes have one dorsal fin, but some fishes have two or three. ... The caudal peduncle is the narrow part of the fish's body.