Jackknife-fish

The jackknife-fish (Equetus lanceolatus) is a striking, boldly striped member of the drum family, Sciaenidae, found on reefs and rocky bottoms throughout the western Atlantic, including Florida, the Bahamas, Bermuda, the Caribbean, and south to Brazil. Its long, curved, trailing dorsal fin resembles an open pocketknife blade, giving the species its common name. Juveniles show an even more exaggerated dorsal filament than adults. Popular with divers and photographers for its dramatic pattern, the jackknife-fish is a shy, secretive reef inhabitant rather than an open-water species. It is common throughout its range and not considered at risk, though it is rarely seen in the open due to its cave-dwelling habits.

The jackknife-fish is unmistakable among reef drums thanks to its bold pattern and dramatic fin shape.

• Pattern: alternating black and white (or silver) horizontal to diagonal stripes running the length of the body
• Dorsal fin: tall, curved, and elongated, sweeping back like an open jackknife blade; longest in juveniles
• Body: elongated, laterally compressed, with a pointed snout
• Size: typically 15-23 cm as adults

It differs from the closely related spotted drum, which shows heavier black banding and a shorter, blunter first dorsal, and from cubbyu, which lacks the extended dorsal filament and shows only faint striping.

Jackknife-fish live in warm, shallow reef and rocky-bottom habitats throughout the tropical and subtropical western Atlantic, including Florida, Bermuda, the Bahamas, the wider Caribbean, and along the coasts of Central and South America to Brazil. They are typically found from just below the surface to around 30 meters, favoring caves, overhangs, crevices, and areas beneath coral heads or wreck structure that offer daytime shelter. Juveniles often occupy shallower, more sheltered pockets than adults. The species prefers clear, structured coastal waters and is rarely encountered over open sand or seagrass far from cover.

Jackknife-fish are shy, solitary, and largely nocturnal, spending daylight hours hidden in caves, crevices, and beneath ledges, often positioned head-down or angled into the shadows. At night they emerge to forage along the bottom for small crustaceans, worms, and other invertebrates. They rarely form schools, though juveniles and adults may occasionally be seen sharing the same shelter. Like other sciaenids, they can produce drumming sounds using muscles attached to the swim bladder. Little is documented about their spawning behavior, but it is presumed to involve pelagic eggs typical of the drum family. Their dramatic coloration and fin shape may serve as a visual deterrent or disruptive camouflage against predators.