How to Identify Pacific Butterfish

To identify Pacific Butterfish (Peprilus simillimus), look at these key features.

Physical Characteristics

Body shape

compressed

Coloration

Dorsal surface is iridescent blue-green to olive-green, fading to bright silvery on the sides and belly. Fins are typically translucent or dusky. Juveniles may have faint vertical bars.

Scale type

cycloid

Mouth position

terminal

Distinctive features

Highly compressed, oval to rhomboidal body shape., Small, cycloid scales that are easily shed., Absence of pelvic fins., A single, long dorsal fin and a similarly shaped anal fin., Deeply forked caudal fin.

Dorsal fin

Single, long dorsal fin originating above the pectoral fin base, with 3-5 spines and 40-47 soft rays. The anterior rays are often elevated.

Tail fin

Deeply forked caudal fin, with two distinct lobes.

Pectoral fin

Long and pointed pectoral fins, typically extending beyond the origin of the anal fin. No pelvic fins are present.

Distinctive fins

Dorsal and anal fins are symmetrical in shape and size, extending almost the entire length of the body from the pectoral fin base to the caudal peduncle.

Identification Tips

1. 1

   Body Shape

   Look for a very thin, oval-shaped body that is highly compressed laterally. This is a key characteristic of the Stromateidae family.

2. 2

   Coloration

   The iridescent blue-green or olive-green back transitioning to bright silver sides and belly is distinctive. Absence of prominent markings or spots.

3. 3

   Fins

   Note the single, long dorsal and anal fins that mirror each other in shape and extend far back on the body. The complete absence of pelvic fins is a crucial identifier. The caudal fin is deeply forked.

4. 4

   Size

   Adults typically reach a maximum length of about 30 cm (12 inches), though most commonly observed around 15-20 cm (6-8 inches).

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