Telescopefish Identification Guide

Key identification features

• Slender, elongated, scaleless body, silvery on the sides fading darker on the back
• Large, tubular eyes fused into a telescope-like structure pointed upward, used to silhouette prey against faint surface light
• Small mouth relative to other deep-sea predators, without the exaggerated fangs seen in many mesopelagic fishes
• Forked tail with a notably elongated lower lobe
• Thin, almost translucent fins with no spines
• Moderate size, reaching roughly 20 to 30 cm

Common look-alikes

• Barreleyes / spookfish (Opisthoproctidae): also have upward-directed tubular eyes, but have a shorter, often barrel-shaped body and, in some species, a transparent dome over the head, unlike the telescopefish's slender torpedo shape.
• Deep-sea hatchetfish: share tubular, upward-oriented eyes, but have a strongly flattened, deep hatchet-shaped body rather than the telescopefish's elongated, slender form.
• Lancetfish: similarly slender and silvery, but have a large sail-like dorsal fin and normal, forward-facing eyes.

Where you'll see one

Telescopefish range through mesopelagic to bathypelagic waters of tropical and subtropical oceans worldwide, migrating vertically each day between roughly 500 and 2,000 meters, using their upturned telescope eyes to spot prey silhouetted from below.