How to Identify Atlantic threadfin

To identify Atlantic threadfin (Polydactylus octonemus), look at these key features.

Physical Characteristics

Body shape

elongated

Coloration

Silvery-gray to yellowish-brown on the back, fading to white or silvery on the belly. Fins are typically dusky or yellowish. No prominent markings.

Scale type

ctenoid

Mouth position

subterminal

Distinctive features

Eight free, filamentous rays on the lower part of each pectoral fin, which are significantly longer than the upper rays., Snout projects slightly beyond the mouth., Large eyes.

Dorsal fin

Two dorsal fins; the first is spiny with 8 spines, the second is soft-rayed with 1 spine and 12-14 soft rays.

Tail fin

Deeply forked caudal fin.

Pectoral fin

Divided into two parts: an upper part with 14-16 rays connected by a membrane, and a lower part with 8 long, free, filamentous rays.

Distinctive fins

The eight free pectoral fin rays are the most distinguishing feature, used for sensory exploration of the substrate.

Identification Tips

1. 1

   Pectoral Fin Rays

   Count the free, filamentous rays on the lower part of the pectoral fin. Polydactylus octonemus consistently has eight such rays, which are notably long.

2. 2

   Snout

   Observe the snout, which protrudes slightly beyond the mouth, a characteristic of many threadfin species.

3. 3

   Body Coloration

   Note the generally silvery to yellowish-brown body color, lacking prominent bars or spots.

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