How to Identify American Butterfish

To identify American Butterfish (Peprilus triacanthus), look at these key features.

Physical Characteristics

Body shape

compressed

Coloration

Dorsal surface is iridescent blue-gray to dark blue, fading to silvery on the sides and belly. Often has several dark, irregular spots along the lateral line, particularly in juveniles. Fins are typically dusky or translucent.

Scale type

cycloid

Mouth position

terminal

Distinctive features

Highly compressed, deep, oval-shaped body., Small, terminal mouth., Absence of pelvic fins., Long, continuous dorsal and anal fins that are nearly symmetrical., Caudal fin deeply forked.

Dorsal fin

Single, long dorsal fin with 3-5 short, stiff spines followed by 40-47 soft rays. The anterior rays are often elevated.

Tail fin

Deeply forked caudal fin.

Pectoral fin

Small, rounded pectoral fins, typically with 19-23 rays.

Distinctive fins

Pelvic fins are entirely absent. The anal fin is long and similar in shape and size to the dorsal fin, with 2-3 short spines followed by 37-44 soft rays.

Identification Tips

1. 1

   Body Shape

   Look for a very deep, laterally compressed, oval-shaped body. This is a primary distinguishing feature.

2. 2

   Fin Configuration

   Note the absence of pelvic fins and the long, continuous, nearly symmetrical dorsal and anal fins. The caudal fin is deeply forked.

3. 3

   Coloration

   Iridescent blue-gray to dark blue dorsally, silvery on the sides and belly. Juveniles often have dark spots along the lateral line.

4. 4

   Size

   Adults typically range from 15-25 cm (6-10 inches) in total length, with a maximum recorded length of about 30 cm (12 inches).

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