How to Identify Almaco Jack

To identify Almaco Jack (Seriola rivoliana), look at these key features.

Physical Characteristics

Body shape

compressed

Coloration

Dorsal side is typically dark blue to greenish-blue, fading to silvery-white on the ventral side. Often exhibits a faint amber or yellowish stripe along the lateral line, which may be more prominent in live specimens. Juveniles often have vertical bars or blotches that fade with age.

Scale type

cycloid

Mouth position

terminal

Distinctive features

Very deep body, giving it a more 'compressed' appearance compared to other Seriola species., High, angular anterior lobe of the second dorsal fin, which is noticeably taller than the anal fin lobe., Relatively short pectoral fins., Absence of scutes on the lateral line, unlike many other carangids.

Dorsal fin

Two dorsal fins; the first with 7-8 spines (often embedded in adults), the second with 1 spine and 27-33 soft rays. The anterior lobe of the second dorsal fin is distinctly elevated and falcate.

Tail fin

Deeply forked caudal fin with pointed lobes.

Pectoral fin

Relatively short, not reaching the origin of the anal fin.

Distinctive fins

Anal fin with 2 detached spines followed by 1 spine and 18-22 soft rays. The anterior lobe of the anal fin is also elevated but shorter than that of the second dorsal fin.

Identification Tips

1. 1

   Body Shape

   Look for a noticeably deeper and more compressed body compared to other amberjacks (Seriola dumerili, S. lalandi).

2. 2

   Dorsal Fin

   The most reliable distinguishing feature is the very high, angular anterior lobe of the second dorsal fin, which is significantly taller than the anterior lobe of the anal fin.

3. 3

   Pectoral Fin Length

   Pectoral fins are relatively short and do not extend to the origin of the anal fin.

4. 4

   Lateral Line

   Unlike many other jacks, the Almaco Jack lacks scutes (bony plates) on its lateral line.

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