How to Identify Squaretail Kob

To identify Squaretail Kob (Argyrosomus thorpei), look at these key features.

Physical Characteristics

Body shape

elongated

Coloration

Overall silvery, often with a darker dorsal surface transitioning to a lighter, silvery-white belly. Fins are typically dusky or yellowish. Juveniles may exhibit faint vertical bars or spots that fade with age.

Scale type

ctenoid

Mouth position

terminal

Distinctive features

Truncate (square-shaped) caudal fin, which is a key distinguishing feature., Large mouth extending to below the posterior margin of the eye., Two dorsal fins, the first spiny and the second soft-rayed., Lateral line prominent and slightly arched anteriorly., Presence of small pores on the snout and chin.

Dorsal fin

Two dorsal fins; the first with 9-10 spines, the second with 1 spine and 26-30 soft rays. The two fins are separated by a distinct notch.

Tail fin

Caudal fin is distinctly truncate (square-shaped) to slightly emarginate.

Pectoral fin

Pectoral fins are moderately long, typically reaching to or beyond the tip of the pelvic fins.

Distinctive fins

Anal fin with 2 spines and 7-8 soft rays. Pelvic fins thoracic, with 1 spine and 5 soft rays.

Identification Tips

1. 1

   Caudal Fin Shape

   The most reliable distinguishing feature is the truncate (square-cut) caudal fin. Other Argyrosomus species typically have emarginate or slightly forked caudal fins.

2. 2

   Dorsal Fin Ray Count

   Count the soft rays in the second dorsal fin (26-30) and compare with similar species.

3. 3

   Mouth Size

   The large mouth extending to below the posterior margin of the eye is characteristic.

4. 4

   Lateral Line

   Observe the prominent, slightly arched lateral line.

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