Acanthurus tractus

Common Name

Ocean Surgeonfish

Year Described

Poey, 1860


Dorsal Fin: IX, 23-26
Anal Fin: III, 21-23
Pectoral Fin: 15-16
Pelvic Fin: I, 5
Gill Rakers: 18-24
Teeth: 14 in upper jaw, 16 in lower jaw

Body deep, oval-shaped, and compressed. Head profile steep with eye high on head. Mouth terminal and very small. A single blade-like spine on both sides of caudal peduncle. Scales ctenoid and small, covering body, parts of head, and fin bases. Caudal fin lunate.


Variable from olive, yellowish, brownish, to bluish-gray, with very fine blue lines on body (only visible close up). A series of blue and yellow lines radiate from posterior eye and around nostrils. Edge of opercle blue. Dorsal fin with alternating oblique lines of yellowish and bluish basally, and bright blue on the margin. Anal fin olive to gray with more blue on the margin, often with parallel darker lines. Caudal fin body colored to yellowish, with a white or blue rear margin. A white band may be present on the caudal peduncle. A blue line circles the caudal spine. Pelvic fin black with a white spine. Pectoral fin yellowish to olive.


Common to 18cm. Maximum size to 35cm.


Coral reefs, rocky areas, and sandy bottoms. Grazes on algae in small groups.


Massachusetts to N. South America, including Bermuda, the Gulf of Mexico, and the Caribbean islands.


Bernal, M.A. and L.A. Rocha. 2011. Acanthurus tractus Poey, 1860, a valid western Atlantic species of surgeonfish (Teleostei, Acanthuridae), distinct from Acanthurus bahianus Castelnau, 1855. Zootaxa No. 2905: 63-68.

Randall, J.E. 2002. Acanthuridae (pp 1801-1805). In: Carpenter. 2002. The living marine resources of the Western Central Atlantic. Vol. 3: Bony fishes part 2 (Opistognathidae to Molidae), sea turtles and sea mammals. FAO Species Identification Guides for Fisheries Purposes. American Society of Ichthyologists and Herpetologists Special Publication No. 5.

Smith-Vaniz, W. F. , H. L. Jelks, and J. E. Randall. 2002. The Gulf surgeon, Acanthurus randalli, a junior synonym of the ocean surgeon, Acanthurus bahianus (Teleostei: Acanthuridae). Gulf of Mexico Science v. 20 (no. 2): 98-105.

Other Notes

This is the species called Acanthurus bahianus in most modern literature and field guides, but that species was originally described from Brazil and is found only in the southwestern Atlantic. It is separable by minor color pattern differences, but more clearly by genetic evidence (Bernal & Rocha, 2011). The two species are allopatric in distribution.

Another species, Acanthurus randalli (Briggs & Caldwell, 1957), from the NE Gulf of Mexico, is now considered the same species (Smith-Vaniz et al., 2002).