How to Identify Longfin trevally

To identify Longfin trevally (Carangoides armatus), look at these key features.

Physical Characteristics

Body shape

compressed

Coloration

Adults are generally silvery-grey to bluish-green dorsally, fading to silvery-white ventrally. Juveniles often have 5-7 dark vertical bands on their flanks, which fade with age. A distinct black spot is usually present on the upper operculum.

Scale type

cycloid

Mouth position

terminal

Distinctive features

Extremely elongated, filamentous anterior rays of the second dorsal and anal fins, especially prominent in juveniles and sub-adults, often extending beyond the caudal fin., A distinct black spot on the upper operculum., Lateral line strongly arched anteriorly, becoming straight posteriorly, with 20-30 scutes (bony plates) on the straight posterior section., Deeply forked caudal fin.

Dorsal fin

Two dorsal fins; the first with 8 spines, the second with 1 spine and 20-22 soft rays. The anterior rays of the second dorsal fin are greatly elongated and filamentous.

Tail fin

Deeply forked caudal fin.

Pectoral fin

Long and falcate (sickle-shaped), extending beyond the origin of the anal fin.

Distinctive fins

The most distinctive feature is the extremely elongated, filamentous anterior lobes of the second dorsal and anal fins, which can be up to twice the length of the head in juveniles.

Identification Tips

1. 1

   Fin Lobes

   Look for the exceptionally long, filamentous anterior rays of the second dorsal and anal fins. This is the most definitive characteristic, especially in younger individuals.

2. 2

   Opercular Spot

   A prominent black spot on the upper part of the gill cover (operculum) is usually present.

3. 3

   Body Shape and Coloration

   Compressed, silvery body. Juveniles have vertical bands that fade with age. Adults are generally uniform silvery-grey.

4. 4

   Lateral Line

   Observe the strongly arched anterior section of the lateral line, transitioning to a straight posterior section with distinct scutes.

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