Dorsal fin

fin on the dorsal of fish and cetaceans

A dorsal fin is a fin on the back of most marine and freshwater vertebrates.

Dorsal fin of a shark

The main function of the fin is to stabilize the animal against rolling and to help sudden turns. There are some secondary functions: some fish have dorsal fins which produce venom at the tip, for example, the spiny dogfish.

Functions change

Some species have further adapted their dorsal fins to other uses.