Moorish Idol, Zanclus cornutus
Moorish Idol, Zanclus cornutus. Fish provided by the commercial fishermen of the greater Los Cabos area, Baja California Sur, March 2010. Length: 10.5 cm (4.1 inches). Note that the philomantis extension of the dorsal fin is black which is atypical of Zanclus cornutus and indicative that this might document the existence of at least two sub-species. Identification courtesy of H.J. Walker, Jr., Scripps Institution of Oceanography, La Jolla, California.
Moorish Idol, Zanclus cornutus. Fish provided by the commercial fishermen of the greater Los Cabos area, Baja California Sur, May 2012. Length: 11.5 cm (4.5 inches).
Moorish Idol, Zanclus cornutus. Fish caught from coastal waters off Kona, Hawaii, July 2017. Length: 10 cm (3.9 inches). Catch, photograph and identification courtesy of Eli (obsessiveangling.wordpress.com).
Moorish Idol, Zanclus cornutus. Fish caught from coastal waters off Kona, Hawaii, March 2021. Length: 11 cm (4.3 inches). Catch, photograph and identification courtesy of Luke Ovgard, Klamath Falls, Oregon. Note the traditional white philomantis extension.
Moorish Idol, Zanclus cornutus. Underwater photograph taken in coastal waters off Kailua-Kona, Hawaii, April 2015. Photograph courtesy of Bob Hillis, Ivins, Utah. Note the traditional white philomantis extension versus the black philomantis extension in the first two fish presented above. I see these as documentation of the existence of two subspecies of Zanclus cornutus.
Moorish Idol, Zanclus cornutus. Underwater photograph taken in coastal waters off Puerto Vallarta, Jalisco, September 2021. Photograph courtesy of Kevin Erwin, Seattle, Washington.
Moorish Idol, Zanclus cornutus. Underwater photograph taken in the greater Cabo San Lucas area, Baja California Sur, November 2017. Note the traditional white philomantis extension versus the black philomantis extension in the first two fish presented above.
Moorish Idol, Zanclus cornutus. Underwater photographs taken in Zihuantanejo Bay, Guerrero, March 2018. Photographs courtesy of Ron Woheau, Zihuantanejo. Note the traditional white philomantis extension versus the black philomantis extension in the first two fish presented above.
The Moorish Idol, Zanclus cornutus, is a member of the Moorish Idol or Zanclidae Family, and is known in Mexico as ídolo moro. The Moorish Idol is the sole global member of the genus Zanclus and the sole global member of the Zanclidae Family. It is found on a limited basis in Mexican waters of both the Atlantic and the Pacific Oceans.
The Moorish Idol has a deep, strongly compressed, disc-shaped body. The males cannot be separated from the females visually. A key to identification is their elongated whip-like dorsal spine, the philomantis extension. They are distinctively colored being white anteriorly and yellow posteriorly and having 2 broad vertical black bars, the first being wide and covering the head and the second located at the rear of the body and covering the anal and dorsal fins. Their dorsal fin filament is traditionally white. Their head has a long protruding tubular snout with short horn-like projections above the eyes. Their eyes are set high on the head and they have a small terminal mouth equipped with long bristle-like teeth. Their snout is black with an orange-bordered saddle and their caudal fin is black with a white margin. Their anal fin is triangular with 3 spines and 31 to 37 rays; their caudal fin is concave; their dorsal fin is sickle-shaped with 6 or 7 dramatically elongated spines and 39 to 43 rays; and, their pectoral fin has extended rays.
The Moorish Idol is found over hard bottom structures including shallow water reef flats and rocky and coral areas from the surface to depths up to 180 m (590 feet). They reach a maximum of 30 cm (12 inches) in length. They travel in small groups or in large schools of greater than 100 individuals. They have a preference for water temperatures between 25oC (75oF) and 28oC (82oF). They are highly selective omnivores and feed on algae, sponges, and other invertebrates. During the night, they attach themselves to the bottom and change to a drab color. Their long streamer, the philomantis extension, is believed to a deterrent to predators. They are known to be preyed upon by Moray Eels. Reproduction is not well understood but involves the release of pelagic eggs with external fertilization. Males become aggressive while breeding. They have an exceedingly long pelagic larval stage, which contributes to the wide distribution of this species. Larvae become very long and transition rapidly into excellent swimmers that are found on the surface for an extended period of time before transitioning to the reef environment. They have a lifespan of up to four years.
The Moorish Idol is widespread in the Indo-Pacific and tropical Eastern Pacific and are now expanding into other areas, which has been attributed to aquarium releases. In Mexican waters they have a limited distribution being found along the southeast coast of Baja California Sur and from Mazatlán, Sinaloa, southward along the coast of the mainland to Guatemala. The collections photographed below extend the range into the southwest tip of the Baja indicative that they are present at least 40 miles north into the Pacific Ocean.
The Moorish Idol is similar in appearance to several of the butterflyfish, including the Scythe Butterflyfish, Prognathodes falcifer, however, the butterflyfish lack the triangular anal fin and the philomantis extension of the dorsal fin.
From a conservation perspective the Moorish Idol is currently considered to be of Least Concern with stable, widely distributed populations. They are retained for human consumption by subsistence fishermen on a limited basis. They are primarily used as a popular pet in home aquariums with increased interest since the release of the movie Finding Nemo with a Moorish Idol named Gill being one of Nemo’s tank mates and in a limited roll in the movie Finding Dory. They are very active and very colorful, however, they are exceedingly difficult to raise and maintain requiring very large tanks and being very finicky eaters. In smaller aquariums they become highly aggressive and do not survive. They have been banned from importation into many European countries. The Moorish Idol is a direct descendant of the extinct Eozanclus brevirostris, which dates to the Eocene Period, 56,000,000 to 34,000,000 years ago.