Barreleye Fish
What is barreleye fish?
Key facts
Barreleye fish are deep-sea fish in the family Opisthoproctidae, best known for their transparent head and upward-looking eyes.
Context
Barreleye fish are deep-sea fish in the family Opisthoproctidae, with the best-known species being Macropinna microstoma [1]. They are notable for living in the ocean’s twilight zone and for having a transparent head with eyes that can look upward through the head [1]. These fish are found in the North Pacific Ocean at depths of 600–800 meters [1]. They feed on zooplankton, including crustaceans and siphonophores [1]. Barreleye fish are sometimes confused with spookfish, but they are distinct species [2].
Documented claims
- Barreleye fish live in the ocean’s twilight to midnight zones. [1]
- The fish has eyes behind its face that gaze upward, and a transparent head. [1]
- Its diet consists primarily of zooplankton. [1]
- Researchers believe barreleye fish are pelagic spawners, releasing eggs and sperm directly into the water. [1]
Questions and answers
Why do barreleye fish have a transparent head?
The transparent head allows the fish’s tubular eyes to look upward through its skull, helping it spot prey in the dim twilight zone [1].
How rare is the barreleye fish?
Barreleye fish are rarely seen because they live at depths of 600–800 meters in the North Pacific, making them difficult to observe in their natural habitat [1].
Can barreleye fish be eaten?
There is no information in the sources about barreleye fish being eaten; they are primarily studied for their unique adaptations [1].
Sources
- 14 Crazy Barreleye Fish Facts (Macropinna Microstoma) — factanimal.com (retrieved August 3, 2026)
- Sea Wonder: Barreleye | Ocean Creatures | Marine Sanctuary — marinesanctuary.org (retrieved August 3, 2026)