Fish Identification: Moorish Idol

Keeping up with a Finding Nemo theme, started last week with the regal blue tang, this week’s fish also makes an appearance in the Pixar movie. The character Gill (voiced by Willem Dafoe) is a moorish idol.

Physical description

Moorish idols are not big fish, reaching a maximum length of 23 cm (about 9 inches), but are often smaller.

Idols have a highly compressed (flat) body that is shaped like a disc. Sharply contrasted vertical bands of white, yellow, and black make them stand out.

Besides the color (which is shared by a few butterflyfish), the snout and dorsal fin are the defining characteristics of a moorish idol. The snout is shaped like a tube, with a tiny mouth on the end. The dorsal fin is long and extends backwards, narrowing into a trailing extension with a distinctive white color.

Geography and habitat

Moorish idols live in tropical to subtropical areas throughout the Pacific and Indo-Pacific regions. They are usually found in reefs, but are often spotted in lagoons as well.

They prefer flat reefs at practically all depths, and are not picky about clarity of water.

Imposters

If you are in the Caribbean and insist you saw a moorish idol, more than likely you saw an imposter. The two candidates are the pennant coralfish (sometimes called the “poor man’s moorish idol”) and the schooling bannerfish (also called “false moorish idol”).

If you need to distinguish between them, moorish idols have a completely black tail fin, with a thin white trim, while the others have yellow caudal fins. Also, the moorish idol’s tubular snout is distinctive. The others have narrow snouts, but aren’t nearly as elongated as the moorish idol.