Photo copyright Tim Nicholson.
Taken on Deadalus Reef, Southern Egyptian Red Sea.
Picasso Trigger Fish, Rhinecanthus assasi

Trigger fishes are so called because of the shark-fin shaped trigger they are able to raise in defense. They use this to jam themselves into a crevice in the coral. The trigger is actually the first spine of its dorsal (top) fin. They bend the second spine forward to fix the first firmly in position. When the fish is swimming the fin is flattened into a groove.

Trigger fish are easy to identify from their distinctive shape. They have deep bodies, high eyes, small mounths and colourful patterns - as evidenced by the Picasso Trigger Fish shown here. Rhinecanthus assasi lives in shallow areas of coral reefs in the Red Sea, Gulf of Oman and Arabian Gulf.

Further Reading
The Underwater Photographer: Digital and Traditional Techniques by Martin Edge, Paperback, 249 pages, 1999
Coral Reef Fishes, Indo-Pacific and Caribbean, by Ewald Lieske and Robert Myers, Harper Collins, 1999
The Red Sea in Egypt, Part I, Fishes, by Farid S Atiya, Elias Modern Printing House, 1994