Grey with a bright yellow tail and two dark spots at its base, in large grazing shoals on Galapagos rock.
To 60 cm, commonly 25. The body is oval and compressed with a steep head profile and the eye set high. Adults are grey with a bright yellow tail, dark bars through the eye and across the shoulder, and black spots at the base of the tail. Juveniles are mostly yellow and look quite different.
The tail armature separates it from the true surgeonfish in the same water: it has several fixed bony plates in a row on each side of the base of the tail, not a single folding blade. That row of plates is why it is also called a sawtail.
Some fish carry heavier black spotting over the body than others, and the spotted form is more common in the north. Those were treated as a separate species until 2019, when a combined genetic, ecological and morphological study found no support for two species and merged them. So the spotted and plain fish are one animal, and the older name is retired. FishBase and the Smithsonian call it the razor surgeonfish or razor sawtail; this site keeps yellowtail surgeonfish, which is the name divers at Galapagos and Cocos actually use and which describes the fish.
It forms big dense schools in shallow water over rocky reef, which is one of the signature sights at Galapagos and Cocos, and it visits cleaning stations. It lives in the top 30 m and has been recorded to 65.
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.