The largest damselfish of the eastern Pacific, dark with a bright blue-edged tail, holding territory on rock.
To about 31 cm, the largest damselfish in the eastern Pacific. Dark grey-blue to nearly bluish-black with narrow white or light blue margins on the soft dorsal, tail and anal fins and pointed pale fin tips. There is no forehead bump. The juvenile is blue-grey with neon-blue facial markings, and breeding males go very pale, nearly whitish, over the front of the body. A lime-green variant occurs in the Gulf of Chiriqui.
The bumphead damselfish is the confusion and the forehead settles it.
One to twenty-five metres on rocky reef, mostly just below the surf zone. It feeds on low-growing attached algae, so it is a genuine farmer, and FishBase states plainly that it defends both feeding and breeding territories by driving off other fish and divers who come too close. It is the one damselfish on this site that will reliably come at you.
Ratings are per location: 1 means found on most dives that look for it, 5 means a handful of records. Where enough dives have been logged the figure is calculated from them; otherwise it is an editorial estimate, and says so. We publish habitat and destination, not the dive site.