Jackknife-fish Identification Guide

Key identification features

• Deep, compressed, blade-shaped body that gives the species its name
• One bold black diagonal band sweeping from the top of the head through the eye down to the base of the tail
• Long, whip-like extension trailing off the tall first dorsal fin, especially pronounced in juveniles
• Pale yellowish-white to silvery background color
• Small mouth and large eye typical of a shade-dwelling reef fish

Common look-alikes

• Cubbyu: lacks the sweeping diagonal band and long dorsal streamer, showing instead horizontal stripes (juveniles) or an overall dark tone (adults).
• Spotted drum: has a more curved, S-shaped black band and spotted dorsal and tail fins rather than a single straight diagonal stripe.
• High-hat: shows several parallel horizontal stripes instead of one diagonal band, with no long dorsal streamer.

Where you'll see one

Jackknife-fish are found in the western Atlantic from Florida and the Gulf of Mexico through the Caribbean to Brazil, usually solitary or in small groups hovering near reef ledges, wrecks, and rocky crevices at moderate depths, often tilted head-down in shaded cover during daylight hours.