How to Identify Frigate Tuna

To identify Frigate Tuna (Auxis thazard), 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 typically features a distinctive pattern of 15 or more narrow, wavy, dark lines above the lateral line, which do not extend forward beyond the middle of the first dorsal fin. A few dark spots may be present below the pectoral fin.

Scale type

none

Mouth position

terminal

Distinctive features

Robust, fusiform body, slightly compressed laterally., Two widely separated dorsal fins; the first dorsal fin has 10-12 spines and is much taller than the second., A series of 8-9 dorsal finlets and 6-8 anal finlets., Small, conical teeth in a single row., Absence of scales on the body except for the corselet (a patch of large, thick scales around the pectoral fin and along the lateral line) and the lateral line itself., Pectoral fins are short, not reaching the interspace between the dorsal fins., Caudal peduncle is slender with a prominent central keel and two smaller keels on either side.

Dorsal fin

Two widely separated dorsal fins. First dorsal fin with X-XII spines, much taller than the second. Second dorsal fin followed by 8-9 finlets.

Tail fin

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

Pectoral fin

Short, not reaching the interspace between the dorsal fins. Located low on the body.

Distinctive fins

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

Identification Tips

1. 1

   Dorsal Fin Separation

   The most distinguishing feature is the wide gap between the first and second dorsal fins. The first dorsal fin is significantly taller than the second.

2. 2

   Dorsal Pattern

   Look for the characteristic pattern of 15 or more narrow, wavy, dark lines on the back, above the lateral line. These lines do not extend forward beyond the middle of the first dorsal fin.

3. 3

   Corselet

   The presence of a well-developed corselet of scales around the pectoral fin and along the lateral line, with the rest of the body appearing scaleless.

4. 4

   Pectoral Fin Length

   The pectoral fins are short and do not reach the vertical line from the interspace between the dorsal fins.

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