Moorish Idol

The Moorish idol's body is highly laterally compressed and disc-like in shape with a tube-like snout and small bony protuberances above the eyes in adults. The mouth is small and has many long, bristle like teeth. There are no spines or serrations on the preoperculum or caudal peduncle. The dorsal fin is supported by 6 or 7 spines, which are elongated into a long filament which resembles a whip, and between 39 and 45 soft rays. The anal fin contains 3 spines and between 31 and 37 soft rays. The maximum published total length is 23 cm (9.1 in), although 21 cm (8.3 in) is more typical. They have a white background color, with two wide black vertical bands on the body with a yellow patch on the posterior end of the body and a yellow saddle on the snout. The caudal fin is black with a white margin.

The Moorish idol has a wide range in the Indian and Pacific Oceans. They are found from the eastern coast of Africa between Somalia and South Africa east to Hawaii and Easter Island. They are also found in the eastern Pacific from the southern Gulf of California to Peru, including many islands such as the Galapagos and Cocos Island.

These fish are pelagic spawners. The males and females release sperm and eggs into the water, and the eggs drift away on the current following fertilization. Like their closely related family, the Acanthuridae, the Moorish idol has larvae that are specialized for a long pelagic life stage, and this is why they are so widespread and geographically uniform. In acanthuridae, the pelagic, pre-juvenile stage larvae can reach lengths of 60 mm before settling in their habitat. The Moorish idol's various larval stages have been described and illustrated. The preflexion larval stage refers to the stage from hatchling to the start of upward flexion of the notochord. The preflexion larval stage of the Moorish idol has no fin spines, soft rays, or internal support structures for the fins. However, in a 3.2 mm specimen there is the start of the dorsal and anal fins.

Since their last assessment in 2015, the Moorish idol is listed as a species of least concern by the IUCN. They were found to be widely distributed and locally abundant with no major threats to the species. However, their habitat type, particularly coral reefs, are known to be in decline due to climate change. The species has been found to do well in restored coral reefs and artificial reef structures.