Pencilled surgeon Acanthurus dussumieri
There are 51 species of surgeon fish, 19 of which occur in southern African waters.
Surgeon fish are so named because of the scalpel-like spines on either side of their tail fins, which are folded into a groove when not in use.
When surgeons are threatened or alarmed, they lift their scalpel spines, using them to slash at their attackers! They also use the spines to wedge themselves into cracks in the reef.
The pencilled surgeon has a single fixed spine on each side of the base of its caudal fin, which is used in defense or when fighting.
Adults live in caves on reefs at depths of up to 100m, or in open water around sea mounts and islands.
The juveniles are found in estuaries where they graze on algae-covered rocks.