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Ray-finned Fishes of Zihuatanejo

CLASS ACTINOPTERYGII

-Animals (Kingdom Animalia)

-Chordates (Phylum Chordata)

-Vertebrates (Subphylum Vertebrata)

-Ray-finned Fishes (Class Actinopterygii)

-Butterflyfishes, Angelfishes, and Allies (Order Acanthuriformes)

-Surgeonfishes, Tangs, and Unicornfishes (Family Acanthuridae)

-Genus Acanthurus

-Convict Surgeonfish (Acanthurus triostegus)


This species is easily recognized by its bold black vertical bars on a pale white to silvery body, giving it a “convict-like” striped appearance. It has an oval, laterally compressed body and grows to about 20–26 cm (8–10 inches) in length. Like other surgeonfishes, it possesses a sharp, scalpel-like spine on each side of the tail base, used for defence. The Convict Surgeonfish is primarily herbivorous, feeding almost exclusively on fine filamentous algae and turf algae growing on rocks and dead coral. It is often seen grazing actively during the day, either alone or in large schools that move across reef flats.

Diet

  • Herbivorous grazer that feeds primarily on filamentous and other benthic algae growing on rocks and dead coral.

  • Often feeds in groups, scraping algae from hard surfaces with its small, comb-like teeth.

  • It may concentrate near freshwater runoff where algae grow particularly well on submerged rocks.

Range

  • Widely distributed throughout the tropical Indo-Pacific.

  • In the eastern Pacific, it ranges from the southern Gulf of California and Pacific coast of Mexico south to Chile.

  • It occurs along the Mexican Pacific coast, including Guerrero, and is within the broader Zihuatanejo region.

Habitat

  • Primarily associated with shallow rocky and coral reefs, including lagoons and exposed seaward reefs.

  • Adults are generally found over hard substrate, while young fish are commonly found in shallow tide pools.

  • Usually encountered in shallow water, particularly around 1–10 metres.

  • Often forms feeding aggregations while grazing over reef surfaces.

Description

  • Medium-sized, laterally compressed surgeonfish with an elongated oval body and a small, low-set mouth.

  • Body is whitish to light greenish-grey, with six narrow black vertical bars across the head and body.

  • One dark bar passes directly through the eye, while another occurs across the caudal peduncle.

  • Reaches approximately 27 cm in total length, with a common length of about 17 cm.

  • A small, sharp, forward-pointing spine occurs on each side of the caudal peduncle; each spine folds into a groove and can be erected when the fish is threatened or excited.

Convict Surgeonfish

Acanthurus triostegus

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