Deep Ocean Fish

The depth of the ocean is much more than the highest landforms present on the surface of Earth. On an average, the depth of ocean is estimated to be about two miles. Ocean is divided into many layers or zones, based on the amount of light that reaches a specific depth. The first layer is sunlight or photic zone (from ocean surface to 200 meters deep), below which lies the twilight or mesopelagic zone (200 meter to more than 1000 meter). The midnight zone is about 2000 meters below the ocean surface. In some oceans, the deepest layers (estimated to be about three times the average depth) are present, for example, the Marianas Trench.

There is no doubt that marine biome represents the highest biomass on Earth. The type of life forms (microbes, plants and fish) present in each ocean layer varies. To be precise, the deepest layers are inhabited by organisms that require minimum sunlight and have the ability to withstand high hydrostatic pressure and extremely cold conditions. Till now, humans have unravel only up to the mesopelagic layer. Let's take a look at some of the fascinating deep ocean fish.

Viper Fish
Viper fish (or Viperfish) is a deep ocean fish, which is found in the mesopelagic zone at a depth of about 800 - 1500 meters. They have extraordinarily large eyes that serve the purpose for collecting light. Some of the Viper fish types are totally black in color; they possess light-sensitive parts (photophores) in the body. The photophores on the dorsal fin are used for luring their prey. Some of them lack pigment and are translucent.

Gulper Eel
Gulper Eel fish is another species that is adapted to the mesopelagic layer of the ocean. One characteristic feature of this fish type is the hinged, rotatable skull adapted for swallowing large-sized preys. Gulper fish also possesses a large mouth and stomach, which are adaptive features for feeding on larger preys (as big as its own size).

Abyssobrotula galatheae
Abyssobrotula galatheae holds the record for the deepest ocean fish till now. It was found in the Puerto Rico Trench at a depth of about 8 km (5 miles). However, this fish was dead by the time it reached the ocean surface. Hence, more extensive studies could not be done regarding their adaptive characteristics.

Pseudoliparis amblystomopsis
This species is by far the deepest living fish discovered by scientists. It was found at a depth of 7.7 km (4.8 miles) in the Japan Trench, Pacific Ocean. The Pseudoliparis amblystomopsis is about 30 cm long and use vibration receptors (present in the snout) for locating food and navigating in the ocean.

Brotulid Fish
The deepest ocean fish is the Brotulid fish that survives at a depth of about 7000 meters below the ocean surface. There is no significant information about this mysterious fish. However, marine scientists are of the opinion that brotulid does not have eyes, rather it has other adaptive features that compensates the lack of vision.

Besides these, other species of fishes residing deep in the ocean are Flashlight fish, Angler fish and Bristlemouth fish. Some characteristic features shared by these fish are big eyes, translucent body and large, dagger-like teeth. Usually, they are bioluminescent and produces light on their own. Currently, various projects have been taken up in order to unravel the mysterious organisms of the deep oceans.