Acanthurus polyzona, commonly known as the black-barred surgeonfish or zebra tang, is a tropical fish found in coral reefs in the western Indian Ocean. First described by the Dutch ichthyologist Pieter Bleeker in 1868, this striking fish has a laterally flattened body, roughly shaped like an almond, and can grow to a length of about 20 cm (8 inches). Its head is short with a pointed snout and a terminal mouth featuring thick lips. The eyes are large, and the two pairs of nostrils sit immediately in front of the eyes. The overall color of the zebra tang is a very pale yellow, with olive-grey dorsally and silvery-white ventrally. Superimposed on this pale background are nine broad black bands, narrowing slightly towards the belly. The first band passes through the eye, the second extends from the front of the dorsal fin to the base of the pectoral fins, and the eighth and ninth bands appear on the caudal peduncle. On either side of the peduncle, there are small, retractable spines.
Interestingly, the only fish with which it is likely to be confused is the “convict tang” (Acanthurus triostegus). The convict tang has a yellower background color and just six vertical, slender black bands. It is more widely distributed, and even within the zebra tang’s restricted range, the convict tang is the more common of the two.
Distribution:
- Acanthurus polyzona has a rather restricted distribution in the tropical western Indian Ocean, including Madagascar, Mauritius, Réunion, and the Comoro Islands.
- It inhabits shallow reef habitats, lagoons, and outer reef slopes, over sandy, rocky, or coral seabeds at depths down to about 15 meters (50 feet).
Ecology:
- The zebra tang is diurnal and feeds primarily on algae, especially filamentous algae.
- It often associates with shoals of convict tangs, taking advantage of the protection provided by numbers.
- While the reproduction of this fish has not been extensively studied, the growth rate of young fish is fast, potentially leading to a doubling of the population in as little as 15 months.
