The commonest wrasse in the region and one of the most studied fish anywhere. Small yellow individuals clean other fish; the blue-headed terminal males are former females.
To about 20 cm, though the two standard sources disagree: STRI gives 15 cm and FishBase 25. Three appearances, and they look like three fish. Juveniles are yellow above and white below with a solid black stripe from the snout through the eye to the tail. Initial-phase adults are variable, yellow above the stripe on the reef and whitish inshore. The terminal male, always male, has a blue head, a bright white saddle with broad black borders just behind the pectoral fin, and a green body.
The juvenile is the one that catches people out, against a juvenile yellowhead wrasse. The stripe settles it: solid black here, blue with dark edges there.
Spawning is at midday, year round, at the same traditional sites. Sex change runs from female to male at around 8 cm. Juveniles clean parasites off other fish, which is worth knowing before handling one.
Nought to forty metres, on reef, in inshore bays and over seagrass.
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.