Ghost fish discovered by Okeanus Explorer during an expedition of the Northern Mariana Islands, in the Pacific Ocean.

Ghost fish discovered by Okeanus Explorer during an expedition of the Northern Mariana Islands, in the Pacific Ocean. YouTube/oceanexplorergov

Researchers are baffled after discovering for the first time a ghostly fish that measures just 10 centimetres. It is for the first time that researchers have spotted this fish alive, more than two kilometres below the ocean’s surface. The pale slug-like fish was caught on camera by the Okeanus Explorer during an expedition of the Northern Mariana Islands, in the Pacific Ocean. The ghostly-looking creature is believed to belong to the Aphyonidae family.

“This is just remarkable ... I am sure that this is an Aphyonid and I am sure that this is the first time a fish of this family has ever been seen alive,” he added. “This is really an unusual sighting,” Fisheries biologist with the NOAA National Marine Fisheries Service, Dr. Bruce Mundy, said in the video.

Mundy added that up to now, fish belonging to the Aphyonidae family, in the same Ophidiiformes order as cusk eels, have only been seen dead after being brought up to surface by dredgers or deep-sea trawlers. He explained that experts who work with various fish species generally have a bucket list. Fish in this family is definitely at the top of the list for many experts.

The Okeanos Explorer team will be surveying the deep water areas of the Commonwealth of the Northern Mariana Islands and Marianas Trench Marine National Monument till July 10. They have been investigating ridges, mud volcanoes, sponge communities, deep sea corals and fish habitats to better understand the extreme life inside the trench.

#Okeanos scientists image ghostly fish that has never been seen alive -- until now: https://t.co/BniyP2Ay2i pic.twitter.com/Wc1hCiFWmR — NOAA Ocean Explorer (@oceanexplorer) July 1, 2016

This family of eel-like fish have transparent, gelatinous skin lacking any scales. They have underdeveloped muscles and gills and their skeletons are only partially calcified. The males have the ability to bundle their sperm into small sacs so that they can store them for extended periods, informs Wikipedia.

Watch First Fish Sighting: 2016 Deepwater Exploration of the Marianas here.

Source: YouTube/oceanexplorergov