How to Identify Indian Threadfin

To identify Indian Threadfin (Leptomelanosoma indicum), look at these key features.

Physical Characteristics

Body shape

elongated

Coloration

Dorsal surface is typically silvery-grey to brownish-grey, fading to silvery-white on the flanks and belly. Fins are generally dusky or yellowish, with the caudal fin often having a darker margin.

Scale type

ctenoid

Mouth position

subterminal

Distinctive features

Four to seven (usually 5-7) long, free, filamentous pectoral fin rays, significantly longer than the main pectoral fin., Two separate dorsal fins., Large, deeply forked caudal fin., Snout projects slightly beyond the mouth., Large scales.

Dorsal fin

Two separate dorsal fins; the first with 8 spines, the second with 1 spine and 13-15 soft rays.

Tail fin

Deeply forked caudal fin with pointed lobes.

Pectoral fin

Pectoral fins are located low on the body, with 15-17 rays, and 5-7 long, free, filamentous rays below the main fin.

Distinctive fins

The free pectoral fin rays are a key diagnostic feature, used for sensing prey in turbid waters.

Identification Tips

1. 1

   Free Pectoral Fin Rays

   Count the number of free, thread-like rays below the main pectoral fin. Leptomelanosoma indicum typically has 5-7 such rays, which are notably long.

2. 2

   Body Shape and Coloration

   Observe the elongated, somewhat compressed body and the silvery-grey to brownish-grey dorsal coloration fading to white ventrally. The snout projects slightly.

3. 3

   Caudal Fin

   Note the deeply forked caudal fin with pointed lobes, which is characteristic of the species.

4. 4

   Lateral Line

   The lateral line is simple and extends from the upper margin of the operculum to the caudal fin base, with 65-75 scales.

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