Dorsal Fin

There is generally a prominent dorsal fin on the back of the dolphin though it is absent in northern and southern rightwhale dolphins. Some of the river dolphins do not have a dorsal fin, but only a slight ridge or hump on the back.

The size, shape and position of the dorsal fin varies from one species to another. The fin is not supported by any bone, but by tough fibrous tissue inside it. Dolphins can have fins that are falcate, triangular, bluntly rounded or totally absent. The functional significance of these different styles of in is uncertain. Some people believe that dorsal fins help dolphins to maintain stability in the water while others believe that a well-developed fin is not essential for survival.

However, the blood vessels in the dorsal fin do help to control body temperature. It acts as a heat exchanger during intense activity or when swimming in particularly warm water.

Bibliography

Harrison, Sir Richard, et. al. Whales, Dolphins and Porpoises. New York: Facts on File, Inc., 1994.

Mark Carwardine, The Book of Dolphins. Dragon's World Ltd, 1996

Tursi. "Tursi's Dolphin Page" Available http://www.neteng.bc.ca/~tursi/dolphins/index.htm, 4 September 1997, Accessed 4 April 1998