Western Indian Ocean
Pomacanthus imperator – Acanthochaetodon imperator
The most widespread angelfish, known from the Red Sea and Western Indian Ocean east to Polynesia and Hawaii in the central Pacific. However, only one specimen suspected to have been released by a local ornamental fish importer is known from Hawaii and there are some geographical variations. Lives in coral rich lagoons and outer reefs from 3 to 70m, where the Emperor angelfish is usually encountered singly or in pairs. Adults are blue with diagonal narrow yellow lines; the eyes are covered by a mask-like dark band and they have a yellow caudal fin. Juveniles are completely different in colour, being almost black with white and blue curving lines, forming circles near the caudal base which distinguishes them form similar species.