Bluelined Emperor

The blue lines on the cheek are drawn, not dotted. Wavy, irregular and unbroken, they wander across the cheek, snout and gill cover of an otherwise golden brown fish. The spangled emperor carries blue on its face too, but those streaks radiate from the eye in straight lines; these do not. It matters, because the blue lines are the only part of this animal that stays put. Dark diagonal bars rise across the body and vanish again within seconds, so it can look barred in one photograph and blank in the next.

The genus name covers the other half. Gymnocranius means naked skull, for the scaleless cheek, and grandoculis means large-eyed, which is the first thing anyone notices. The eye sits high on the head against a steep forehead and is almost as long as the snout. A bony ridge crosses the nape, a bony shelf sits over the front of the eye, and the forked tail ends in pointed lobes with an orange edge.

Emperors are largely night feeders over soft ground and this one is built for it: canines at the front of the jaws for seizing, blunter teeth behind for crushing, and a diet of bottom invertebrates and small fish taken off sand, mud and rubble. It is usually alone or in a small group.

Where you meet it depends on its age. Juveniles and subadults come into shallow inshore bays over mud and seagrass, which is where most 🌊 Red Sea photographs of the species are taken. Adults move out and down. FishBase gives a range of 20 to 170 m, and the regional guide puts it in seagrass areas usually below 20 m. On an ordinary reef dive it is an uncommon fish.

It reaches 80 cm and 5.5 kg, with 64 cm a common adult size. Its range runs from the 🌊 Red Sea and 🇿🇦 South Africa east to the Tuamotus and north to 🇯🇵 Japan, and bottom longlines and trawls take it throughout.