Hatchetfish Identification Guide

Key identification features

• Strongly compressed, deep, hatchet-shaped body with a thin, narrow tail stalk
• Large, upward-directed, often telescoping eyes
• Highly reflective, silvery scales that help camouflage the fish from below
• Rows of ventral photophores (light organs) running along the ridge of the deep belly
• Small mouth positioned near the top of the head
• Typically small, 1-4 inches in length
• Sharp, keel-like belly ridge that houses the row of downward-pointing photophores used for counter-illumination

Common look-alikes

• Lanternfish: more elongated, typical fish-shaped body rather than a laterally compressed, hatchet-like profile
• Bristlemouths: slender, elongated body with a large gaping mouth, lacking the hatchetfish's deep, blade-like shape
• Viperfish: elongated and slender with prominent fangs, very different from the hatchetfish's compact, disc-like body

Where you'll see one

Marine hatchetfish occupy the mesopelagic zone of oceans worldwide, generally between 200 and 1,500 meters deep. Their upward-facing eyes and silvery, mirror-like sides help them detect prey silhouetted above while remaining camouflaged from predators looking up from below in the dim, filtered light.