How to Identify Chocolate Tang

To identify Chocolate Tang (Acanthurus thompsoni), look at these key features.

Physical Characteristics

Body shape

compressed

Coloration

Adults are typically a uniform dark brown to black, often appearing chocolate brown, sometimes with a purplish or bluish sheen. The caudal fin can be slightly paler. Juveniles may have a lighter body with a darker caudal fin. A small, pale spot may be present at the base of the pectoral fin in some individuals, though this is not always prominent.

Scale type

ctenoid

Mouth position

terminal

Distinctive features

Small, terminal mouth, Elongated, oval body shape, Scalpel-like spine on each side of the caudal peduncle, Relatively small pectoral fins compared to other tangs, Absence of prominent markings or patterns on the body

Dorsal fin

Dorsal fin with 8 spines and 23-26 soft rays, continuous and relatively high.

Tail fin

Lunate (crescent-shaped) caudal fin, often with a slightly paler posterior margin.

Pectoral fin

Pectoral fins with 16-17 rays, relatively small and translucent.

Distinctive fins

Anal fin with 3 spines and 23-26 soft rays. Pelvic fins with 1 spine and 5 soft rays. The caudal peduncle bears a single, sharp, retractable scalpel on each side.

Identification Tips

1. 1

   Coloration

   Uniform dark brown to black body, lacking prominent patterns or stripes. This distinguishes it from many other tang species.

2. 2

   Body Shape

   More elongated and less disc-shaped than many other Acanthurus species, with a relatively small head.

3. 3

   Caudal Fin

   Distinctly lunate (crescent-shaped) tail, often with a slightly lighter posterior edge.

4. 4

   Pectoral Fins

   Relatively small and translucent pectoral fins, which can appear almost clear.

5. 5

   Scalpel

   Presence of a single, sharp, retractable scalpel on each side of the caudal peduncle, characteristic of all surgeonfishes.

Explore Chocolate Tang