A dark damselfish with a bright yellow tail, holding a grazing territory on Galapagos and Cocos rock.
To about 16 cm. Dark yellow-brown with yellow lips, yellow at the tail base and yellow fin tips, and large visible scales. In juveniles the yellow of the tail runs forward onto the rear body and there is an eyespot on the dorsal fin.
The Galapagos ringtail damselfish is sympatric and the tail separates them: yellow or gold here, dark with a white band there.
One to thirty metres on rock and coral, and locally very abundant. It is strongly territorial and actively attacks fish that enter its space. A 2022 study in the Galapagos found that what it defends is an algal lawn, and that aggression rises with the density of other damselfish and falls as territory size increases — so this is a confirmed farmer, not just a defender.
Endemic to the tropical eastern Pacific islands: the Galapagos, Cocos, Malpelo, Gorgona and La Plata.
This entry used to be called the yellowtail damselfish. That name belongs to the Caribbean Microspathodon chrysurus in every major reference, so it has been changed; the old URL redirects here.
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.