Black Surgeonfish

Overview

The Black Surgeonfish (Acanthurus gahhm) is a marine ray-finned fish endemic to the Red Sea and the Gulf of Aden. This species is a member of the Acanthuridae family, characterized by its oval, laterally compressed body and a sharp, defensive spine located on the caudal peduncle.

Distribution & Habitat

This species is restricted to the northwestern Indian Ocean, specifically the Red Sea and the Gulf of Aden. It is a demersal fish that typically inhabits coral reefs, lagoons, and areas with sandy or rubble substrates. They are often found in open environments near rock or coral structures.

Appearance

Adults typically display a dark brown to black body coloration, accented by a distinctive yellow stripe behind the eyes and a white ring around the base of the tail. A key diagnostic feature is the presence of two longitudinal bands: one extending posteriorly from the eye and another reaching forward from the caudal peduncle spine. These markings develop as the fish matures, with juveniles lacking one or both bands depending on their size. The pectoral fins are often tipped with yellow, and the caudal fin is crescent-shaped.

Biology & Behavior

Black Surgeonfish are diurnal and can be observed either as solitary individuals or in small to large aggregations, sometimes mixing with other herbivorous reef species. Like other surgeonfishes, they utilize their sharp caudal spines for defense. They are primarily omnivorous, feeding on a diet of benthic algae, detritus, and zooplankton. Reproduction involves broadcast spawning, where eggs and sperm are released into the water column to drift with the currents.