How to Identify Bluefin Trevally

To identify Bluefin Trevally (Caranx melampygus), look at these key features.

Physical Characteristics

Body shape

compressed

Coloration

Adults typically have a silvery-grey to brassy-yellow body, often with numerous small, iridescent blue to black spots scattered over the flanks. The dorsal, anal, and caudal fins are often electric blue, especially in larger individuals and during breeding. Juveniles are generally silvery with faint vertical bars.

Scale type

cycloid

Mouth position

terminal

Distinctive features

Electric blue fins and spots (more pronounced in adults), Steeply sloped head profile, Large, deeply forked caudal fin, Prominent scutes along the lateral line near the caudal peduncle

Dorsal fin

Two dorsal fins; the first with 8 spines, the second with 1 spine and 21-24 soft rays. The anterior lobe of the second dorsal fin is elongated.

Tail fin

Deeply forked caudal fin, with prominent blue coloration.

Pectoral fin

Long, falcate (sickle-shaped) pectoral fins, typically blue.

Distinctive fins

Anal fin similar in shape to the second dorsal fin, with 2 detached spines followed by 1 spine and 17-20 soft rays. Pelvic fins are relatively small.

Identification Tips

1. 1

   Coloration

   Look for the distinctive electric blue fins (especially dorsal, anal, and caudal) and blue to black spots on the body. This is the most reliable field mark for adults.

2. 2

   Body Shape

   Observe the compressed, deep body and the steeply sloped head profile.

3. 3

   Fin Shape

   Note the long, falcate pectoral fins and the elongated anterior lobe of the second dorsal fin.

4. 4

   Scutes

   Examine the posterior section of the lateral line for a series of strong, bony scutes (enlarged scales).

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