A large blue-green parrotfish of eastern Pacific reef, scraping algae from rock with a fused beak.
To about 60 or 68 cm depending on the source, commonly 35. Like all parrotfish it has two phases that look like different fish. Initial-phase fish have a brownish head and front body, blue-green over the rear half, dark lines radiating from the eye and vertical rows of grey spots making diffuse bars. Terminal-phase males are mostly green with orange-brown outlines to every scale, a green snout, and irregular green bands radiating from the eye. Adults develop a slight forehead hump.
The eastern Pacific bumphead parrotfish is the confusion. Its hump is pronounced, its beak is dark blue and its eye lines are dark and spoke-like; this fish has only a slight hump and orange-brown scale edging.
It lives on rocky, boulder-strewn reef between 3 and 25 m and scrapes algae off rock. It is uncommon. There is a genuinely unusual thing about it: published work in 2020 concluded that the species arose through hybridisation between two ancient eastern Pacific species pairs across the whole region. It is recorded from the central Gulf of California to Ecuador and at Revillagigedo, Cocos and the Galapagos.
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.