How to Identify Indian Threadfish

To identify Indian Threadfish (Alectis indica), look at these key features.

Physical Characteristics

Body shape

compressed

Coloration

Adults are silvery, often with a metallic blue-green sheen dorsally, fading to silvery-white ventrally. Juveniles have a more silvery body with faint vertical bands, and their filamentous fin rays are often dark or black.

Scale type

none

Mouth position

terminal

Distinctive features

Highly compressed, deep, diamond-shaped body, especially in juveniles., Extremely long, filamentous rays on the dorsal and anal fins in juveniles, which shorten significantly with age., Forehead profile is steep and convex., Lateral line strongly arched anteriorly, becoming straight posteriorly.

Dorsal fin

Two dorsal fins; the first with 7-8 short, embedded spines (often not visible in adults), the second with 1 spine and 18-20 soft rays. The anterior soft rays are greatly elongated in juveniles.

Tail fin

Deeply forked caudal fin.

Pectoral fin

Long and falcate (sickle-shaped).

Distinctive fins

Anal fin with 2 detached spines followed by 1 spine and 15-17 soft rays. Anterior anal fin rays also greatly elongated in juveniles. Pelvic fins are small.

Identification Tips

1. 1

   Body Shape

   Look for the very deep, compressed, diamond-shaped body, especially pronounced in younger individuals.

2. 2

   Fin Filaments

   Juveniles are unmistakable due to their extremely long, trailing dorsal and anal fin rays. These shorten dramatically as the fish matures.

3. 3

   Coloration

   Adults are uniformly silvery, sometimes with a bluish or greenish tinge dorsally. Juveniles may have faint vertical bands.

4. 4

   Forehead Profile

   The steep, convex forehead profile is a good indicator, particularly in larger specimens.

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