How to Identify Lined Rainbowfish

To identify Lined Rainbowfish (Stethojulis strigiventer), look at these key features.

Physical Characteristics

Body shape

elongated

Coloration

Initial Phase (IP) individuals (females and some males) typically exhibit a pale greenish-brown to yellowish-brown body with several prominent dark longitudinal stripes along the lower flanks, often appearing as a series of dashes or broken lines. A distinct black spot is usually present on the caudal peduncle. The head may have iridescent blue or green markings. Terminal Phase (TP) males are more brightly colored, often displaying a greenish-blue body with a prominent orange or reddish stripe running from the snout through the eye to the operculum, and another along the mid-flank. The ventral side remains paler with faint striations. Juveniles resemble IP females but are generally duller.

Scale type

cycloid

Mouth position

terminal

Distinctive features

Small, pointed snout, Continuous dorsal fin, Distinctive longitudinal stripes on the lower flanks (especially in IP), Black spot on caudal peduncle (especially in IP), Buries in sand at night or when threatened

Dorsal fin

Single, continuous dorsal fin with 9 spines and 11 soft rays. The spinous portion is typically lower than the soft-rayed portion.

Tail fin

Rounded to slightly truncate caudal fin.

Pectoral fin

Relatively small and rounded pectoral fins.

Distinctive fins

Pelvic fins are small and located ventrally, just behind the pectoral fins.

Identification Tips

1. 1

   Body Stripes

   Look for the characteristic dark longitudinal stripes or dashed lines on the lower half of the body, particularly prominent in initial phase individuals.

2. 2

   Caudal Peduncle Spot

   A distinct black spot on the caudal peduncle (the narrow part of the body connecting to the tail fin) is a key identifier, especially in initial phase fish.

3. 3

   Terminal Phase Coloration

   Terminal phase males will display brighter colors, often with an orange or reddish stripe through the eye and along the mid-flank, distinguishing them from initial phase individuals.

4. 4

   Behavior

   Observe its behavior; it often forages actively over sand and rubble, and will quickly bury itself in the sand when startled or at night.

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