How to Identify Bullet Tuna

To identify Bullet Tuna (Auxis rochei), look at these key features.

Physical Characteristics

Body shape

torpedo

Coloration

Dorsal side is dark bluish-black, fading to silvery-white on the flanks and belly. The back often has a distinctive pattern of dark, wavy, oblique lines or 'worm-like' markings above the lateral line, which do not extend forward beyond the middle of the first dorsal fin.

Scale type

none

Mouth position

terminal

Distinctive features

Robust, fusiform body, slightly compressed., Two widely separated dorsal fins., Small, conical teeth., Corselet of scales well-developed, but body otherwise naked., Seven to nine dorsal finlets and six to eight anal finlets., Pectoral fins short, not reaching the vertical line from the anterior margin of the corselet., Absence of a swim bladder.

Dorsal fin

Two dorsal fins, widely separated. The first dorsal fin has 10-12 spines, and the second dorsal fin is followed by 7-9 finlets. The first dorsal fin is significantly taller than the second.

Tail fin

Deeply forked (lunate) caudal fin, characteristic of fast-swimming pelagic fish.

Pectoral fin

Short, triangular pectoral fins, typically not extending beyond the anterior margin of the scaly corselet.

Distinctive fins

Anal fin followed by 6-8 finlets. Pelvic fins are small and located beneath the pectoral fins.

Identification Tips

1. 1

   Dorsal Fin Separation

   The two dorsal fins are widely separated, a key characteristic distinguishing it from other scombrids.

2. 2

   Body Markings

   Look for the distinctive pattern of dark, wavy, oblique lines on the back above the lateral line, which do not extend forward beyond the middle of the first dorsal fin. This differentiates it from Auxis thazard (Frigate Tuna) where the markings extend further forward.

3. 3

   Pectoral Fin Length

   The pectoral fins are short and do not reach the vertical line from the anterior margin of the scaly corselet.

4. 4

   Absence of Swim Bladder

   While not visible externally, the absence of a swim bladder is a physiological characteristic of Auxis species, contributing to their constant swimming behavior.

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