How to Identify Diamond Trevally

To identify Diamond Trevally (Megalaspis cordyla), look at these key features.

Physical Characteristics

Body shape

torpedo

Coloration

Dorsal surface is typically metallic blue-green to dark blue, fading to silvery white on the flanks and belly. Fins are dusky to yellowish, with the caudal fin often dark-tipped.

Scale type

cycloid

Mouth position

terminal

Distinctive features

Elongated, fusiform body, moderately compressed., A series of 8-10 detached finlets behind the second dorsal and anal fins, a key diagnostic feature., Large, deeply forked caudal fin with long lobes., Lateral line with a long, posterior straight section armed with 50-60 very strong, scute-like scales (scutes) that are much larger and more prominent than in most other carangids., Snout pointed, mouth terminal, reaching to below the anterior margin of the eye., Two separate dorsal fins: the first with 8 spines, the second with 1 spine and 10-11 soft rays, followed by finlets., Anal fin with 2 detached spines followed by 1 spine and 8-9 soft rays, then finlets.

Dorsal fin

Two separate dorsal fins; first with 8 spines, second with 1 spine and 10-11 soft rays, followed by 8-10 finlets.

Tail fin

Deeply forked with long, slender lobes.

Pectoral fin

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

Distinctive fins

Presence of 8-10 detached finlets behind both the second dorsal and anal fins.

Identification Tips

1. 1

   Finlets

   The most definitive feature is the presence of 8-10 detached finlets behind both the dorsal and anal fins, a characteristic shared with mackerel scads but distinct from most other trevallies.

2. 2

   Lateral Line Scutes

   The posterior straight section of the lateral line is heavily armed with 50-60 very large, strong scutes, which are noticeably more prominent and numerous than in other carangids.

3. 3

   Body Shape

   Its elongated, torpedo-like body and deeply forked caudal fin distinguish it from the more compressed, disc-shaped trevallies.

4. 4

   Pectoral Fin

   The long, falcate pectoral fin is another good indicator, extending well past the origin of the second dorsal fin.

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