# Barreleye (*Opisthoproctus grimaldii*)

The Barreleye fish has a transparent head and tubular eyes that can rotate to look upwards. It lives in the deep sea, where it uses its unique eyes to spot prey above.

- **Category:** [Fish](https://www.snappit.app/explore/categories/fish)
- **Rarity:** Rare
- **Danger:** 1/5 · Very low
- **Habitat:** Deep Sea

![Barreleye](https://res.cloudinary.com/drieglelr/image/upload/v1771424454/objects/5888.jpg)

## Appearance

The Barreleye has a distinctive transparent, fluid-filled dome on its head, revealing its large, tubular, upward-pointing green eyes. Its body is generally slender and silvery-brown, with small, paddle-like fins. This unique head structure makes it visually different from most fish.

## Taxonomy

- **Kingdom:** Animalia
- **Phylum:** CHORDATA
- **Class:** Actinopterygii
- **Order:** OSMERIFORMES
- **Family:** OPISTHOPROCTIDAE
- **Genus:** Opisthoproctus

## Interesting facts

- Barreleyes often hang perfectly still in the water, waiting for dinner to drift right to them!
- Scientists only first observed a live barreleye with its transparent head intact in 2004!
- Their glowing green eyes act like sunglasses, helping them spot faint glowing prey!
- They are also known as 'spook fish' because of their incredibly strange and ghostly appearance!

## Special abilities

- **See-Through Skull:** Barreleye has a transparent head that protects its delicate eyes, allowing it to see clearly in the deep ocean.
- **Upward Gaze:** Barreleye can rotate its tubular eyes forward when hunting, helping it precisely target tiny prey from above.
- **Low-Light Vision:** Barreleye has specialized eye lenses that gather scarce light, helping it spot silhouettes of food in darkness.

## Measurements & details

- **Length:** 10-25 cm
- **Weight:** 0.05-0.2 kg
- **Lifespan:** 5-10 years
- **Swim Speed:** 0.5 km/h
- **Maximum Depth:** 1000 m
- **Water Type:** Saltwater

## Diet & Feeding

Barreleyes are carnivores that patiently ambush tiny crustaceans and other small deep-sea animals.

- **Primary Foods:** Copepods, Small Crustaceans, Siphonophores, Gelatinous Zooplankton
- **Foraging Method:** Ambush

## Ecological connections

- **Eats:** Copepod (*Calanus finmarchicus*) — A tiny, common crustacean, a staple food for many deep-sea fish.
- **Eaten by:** [Fangtooth](https://www.snappit.app/explore/fangtooth) (*Anoplogaster cornuta*) — This deep-sea predator has fearsome teeth for catching smaller fish.
- **Eaten by:** Black Swallower (*Chiasmodon niger*) — A formidable deep-sea fish known for swallowing prey larger than itself.

## Traits

- [Wildlife](https://www.snappit.app/explore/traits/wildlife): Wildlife encompasses all undomesticated animal and plant life existing in their natural habitats.
- [Piscivorous](https://www.snappit.app/explore/traits/piscivorous): Piscivorous organisms are animals that primarily subsist on a diet of fish.
- [Ambush Predator](https://www.snappit.app/explore/traits/ambush-predator): An ambush predator hunts by patiently waiting and concealing itself, then launching a sudden attack when unsuspecting prey comes within range.
- [Deep Sea](https://www.snappit.app/explore/traits/deep-sea): Deep sea habitats are characterized by extreme pressure, darkness, and cold temperatures, supporting unique life forms below the sunlit zone.
- [Echolocation](https://www.snappit.app/explore/traits/echolocation): Echolocation is a biological sonar used by animals to navigate, hunt, and communicate by emitting sound waves and interpreting the echoes.
- [Aquatic](https://www.snappit.app/explore/traits/aquatic): Aquatic habitats encompass environments where organisms live predominantly in water, including oceans, rivers, lakes, and wetlands.
- [Nocturnal](https://www.snappit.app/explore/traits/nocturnal): Nocturnal animals are primarily active during the nighttime hours, typically resting or sleeping during the day.

## Collections

- [Fish](https://www.snappit.app/explore/collections/fish)

## Safety

**Danger:** 1/5 · Very low

Barreleye fish live in the deep sea and are not encountered by people. They are not dangerous to humans.

## Frequently Asked Questions

### How to identify Barreleye?

Look at body shape, where the fins sit and their outline, mouth position, stripes and spots. Young fish and breeding adults can wear different patterns, and aquarium color varieties can look nothing like wild fish. Fish Identifier: upload a photo and compare the visible details.

### How long is Barreleye?

10-25 cm

### How much does Barreleye weigh?

0.05-0.2 kg

### How long does Barreleye live?

5-10 years

### What does Barreleye eat?

Barreleyes are carnivores that patiently ambush tiny crustaceans and other small deep-sea animals.

### How fast can Barreleye swim?

0.5 km/h

### Where is Barreleye usually found?

Deep Sea

### How does Barreleye hunt?

Ambush

## More Fish

- [Rainbow Trout](https://www.snappit.app/explore/rainbow-trout) (*Oncorhynchus mykiss*)
- [Brown Trout](https://www.snappit.app/explore/brown-trout) (*Salmo trutta*)
- [Brook Trout](https://www.snappit.app/explore/brook-trout) (*Salvelinus fontinalis*)
- [Lake Trout](https://www.snappit.app/explore/lake-trout) (*Salvelinus namaycush*)

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Source: [Barreleye: Characteristics, Facts & Places to See — Snappit](https://www.snappit.app/explore/barreleye)