Blue Tang, Acanthurus coerulens

Blue Tang, Acanthurus coerulens, Juvenile. Underwater photographs taken in coastal waters of Yal-Ku, Quintana Roo, April 2016. Photographs courtesy of Juan Rojo, Akumal.

Blue Tang, Acanthurus coerulens. Fish caught from coastal waters off Caye Ambergris, Belize, June 2013. Length: 15 cm (5.9 inches). Catch, photograph and identification courtesy of Eli (obsessiveangling.wordpress.com).

Blue Tang, Acanthurus coerulens. Underwater photographs taken in coastal waters of Yal-Ku, Quintana Roo, April 2016. Photographs courtesy of Juan Rojo, Akumal.

Blue Tang, Acanthurus coeruleus, Mixed In With a School of Mimicking Ocean Surgeonfish, Acanthurus tractus. Underwater photograph taken in coastal waters of Bonaire in December 2019. Photograph courtesy of Bob Hillis, Ivins, Utah.

The Blue Tang, Acanthurus coerulens, whose common Spanish name is cirujano rayado, is a member of the Surgeonfish or Acanthuridae Family, that is also known as the Blue Tang Surgeonfish and in Mexico as cirujano rayado. Globally, there are forty-two species in the genus Acanthurus, of which seven are found in Mexican waters, three in the Atlantic and four in the Pacific Ocean.

The Blue Tang has a deep strongly compressed oval body. The adults are a uniform blue color with dark thin wavy lines on the sides and a bright yellow highly visible “scalpel” at the base of the tail. Juveniles are yellow or yellow with blue fin margins; sub-adults are blue with a yellow tail. Their head has a steep profile with a pointed snout with eyes set high on the head, a small protrusible mouth set low on the head with eighteen fixed flattened teeth on upper jaw and twenty on the lower jaw. Their anal fin has 3 spines and 24 to 26 rays; their caudal fin is concave with sharp tips; their dorsal fin is continuous with 9 spines and 26 to 28 rays. They have short caudal peduncles with a single razor-sharp spine on each side that is utilized for defense. They have 13 to 14 gill rakers. They are covered with small scales.

The Blue Tang is found around and within coral reefs, rocky habitats and nearby seagrass beds singly, in pairs or in small groups of up to twelve individuals at depths up to 60 m (200 feet). They reach a maximum of 36 cm (14 inches) in length. The juveniles are solitary and territorial and seldom seen by humans as they hide deep within the reef to avoid predation; the adults can be territorial or non-territorial and form large, dense, mixed-species schools. They are active diurnally and take shelter at night to avoid predation. They feed on a wide variety of benthic algae and are classified as grazers. All developmental stages (eggs, larvae, juveniles, and adults) are preyed upon by larger fish including Bar Jacks, Tiger Grouper and various Tunas. The juveniles are known to set up cleaning salons for the Green Sea Turtle, Chelonia mydas. The sexes are similar in appearance. Reproduction is oviparous with annual breeding cycles and will spawn in pairs of in large aggregations. They are broadcast spawners and release pelagic eggs, that are fertilized externally, that quickly hatch into pelagic larvae. They have lifespans of up to twenty-two years.

The Blue Tang is a resident of all Mexican waters of the Atlantic Ocean including the Gulf of Mexico and the east coast of the Yucatán Peninsula in the Caribbean.

The Blue Tang is uniquely colored and cannot be confused with any other species with the possible exception of the Blue Parrotfish, Scarus coeruleus (elongated body, no yellow tail scalpel).

From a conservation perspective the Blue Tang is currently considered to be of Least Concern with stable and widely distributed populations. Some populations are in decline regionally due to fishing pressure. They play an important role on the ecology of the coral reefs being bioeroders. Their long-term survival will be based on the preservation of the coral reefs in which they reside. The Blue Tangs form large highly visible schools on the reef and they are easy to identify due to their all blue color with prominent yellow scalpel at the tail base they flee when approach by divers and make for very difficult photographic subjects. Although caught and consumed by subsistence fishermen they are not a popular food fish as they possess a strong odor and are known to contain ciguatoxin. They are utilized by the aquarium trade and currently can be purchased via the internet. They are however, one of the more difficult Surgeonfishes to handle (due the sharp hidden scalpel in the caudal peduncle) and maintain. They can be used as a bait fish.

A word of caution. The spines at the tail base of this fish provide a unique defense mechanism and can inflict major slashing wounds, rendering them dangerous to handle.