Deep-sea fish are fish that live in the darkness below the sunlit surface waters, that is below the epipelagic or photic zone of the sea. The lanternfish is, by far, the most common deep-sea fish. Other deep-sea fishes include the flashlight fish, cookiecutter shark, bristlemouths, anglerfish, viperfish, and some species of eelpout.
The Portuguese man o' war, also known as the man-of-war or bluebottle, is a marine hydrozoan found in the Atlantic Ocean and the Indian Ocean. It is considered to be the same species as the Pacific man o' war or bluebottle, which is found mainly in the Pacific Ocean. The Portuguese man o' war is the only species in the genus Physalia, which in turn is the only genus in the family Physaliidae.
The vampire squid is a small cephalopod found throughout temperate and tropical oceans in extreme deep sea conditions. The vampire squid uses its bioluminescent organs and its unique oxygen metabolism to thrive in the parts of the ocean with the lowest concentrations of oxygen. It has two long retractile filaments, located between the first two pairs of arms on its dorsal side, which distinguish it from both octopuses and squids, and places it in its own order, Vampyromorphida, although its closest relatives are octopods. As a phylogenetic relict, it is the only known surviving member of its order.
Cetomimidae is a family of small, deep-sea cetomimiform fish. They are among the most deep-living fish known, with some species recorded at depths in excess of 3,500 m (11,500 ft). Females are known as flabby whalefishes, Males are known as bignose fishes, while juveniles are known as tapetails and were formerly thought to be in a separate family, dubbed Mirapinnidae. Adults exhibit extreme sexual dimorphism, and the adult males were once thought to be exemplars of still another family, Megalomycteridae.
Siphonophorae is an order within Hydrozoa, which is a class of marine organisms within the phylum Cnidaria. According to the World Register of Marine Species, the order contains 175 species described thus far.
Telescopefish are small, deep-sea aulopiform fish comprising the small family Giganturidae. The two known species are within the genus Gigantura. Though rarely captured, they are found in cold, deep tropical to subtropical waters worldwide.
Barreleyes, also known as spook fish, are small deep-sea argentiniform fish comprising the family Opisthoproctidae found in tropical-to-temperate waters of the Atlantic, Pacific, and Indian Oceans.
The Pacific viperfish, Chauliodus macouni, is a predatory deep-sea fish found in the North Pacific. It is reported as being either mesopelagic or bathypelagic, with diel vertical migration to shallower waters. The Pacific viperfish is one of the nine different species that belong to the genus Chauliodus, the viperfish. The Pacific viperfish tend to be the largest of the species, typically reaching lengths of up to 1 foot and are considered an example of deep-sea gigantism. The length-weight relationship of the pacific viperfish varies with sex with females tending to be longer and heavier than males.
Pelagic fish live in the pelagic zone of ocean or lake waters—being neither close to the bottom nor near the shore—in contrast with demersal fish that live on or near the bottom, and reef fish that are associated with coral reefs.
The Monterey Bay Aquarium Research Institute (MBARI) is a private, non-profit oceanographic research center in Moss Landing, California. MBARI was founded in 1987 by David Packard, and is primarily funded by the David and Lucile Packard Foundation. Christopher Scholin serves as the institute's president and chief executive officer, managing a work force of approximately 220 scientists, engineers, and operations and administrative staff.
The deep sea is broadly defined as the ocean depth where light begins to fade, at an approximate depth of 200 m (660 ft) or the point of transition from continental shelves to continental slopes. Conditions within the deep sea are a combination of low temperatures, darkness, and high pressure. The deep sea is considered the least explored Earth biome as the extreme conditions make the environment difficult to access and explore.
The sea toads and coffinfishes are a family, the Chaunacidae, of deep-sea ray-finned fishes belonging to the monotypic suborder Chaunacoidei within the order Lophiiformes, the anglerfishes. These are bottom-dwelling fishes found on the continental slopes of the Atlantic, Indian, and Pacific Oceans, at depths to at least 2,460 m (8,070 ft). There have also been findings of deep-sea anglerfishes off the coasts of Australia and New Caledonia. Other findings suggest some genera of Chaunacidae are found near volcanic slopes encrusted with manganese. Of the two genera in the family, Chaunacops are typically found at deeper depths than Chaunax, but with considerable overlap between the two genera.
Praya dubia, the giant siphonophore, lives in the mesopelagic zone to bathypelagic zone at 700 m (2,300 ft) to 1,000 m (3,300 ft) below sea level. It has been found off the coasts around the world, from Iceland in the North Atlantic to Chile in the South Pacific.
The brownsnout spookfish or brown-snout spookfish is a species of barreleye in the family Opisthoproctidae. It and the glasshead barreleye fish are the only vertebrates known to employ a mirror, in addition to a lens, to focus an image in its eyes. This species probably has a worldwide tropical and temperate distribution; in the Atlantic Ocean it is known from Bermuda, the Bahamas, the Greater Antilles, and the Gulf of Mexico, and in the Pacific Ocean it is known from the California Current region and the South China Sea. It is found in the mesopelagic and bathypelagic zones at a depth of 500–2,400 meters (1,600–7,900 ft), but usually occurs below 1,000 meters. In the Gulf of Mexico it is found shallower, at 310–460 meters (1,020–1,510 ft).
Fish are very diverse animals and can be categorised in many ways. Although most fish species have probably been discovered and described, about 250 new ones are still discovered every year. According to FishBase about 34,800 species of fish had been described as of February 2022, which is more than the combined total of all other vertebrate species: mammals, amphibians, reptiles and birds.
Underwater camouflage is the set of methods of achieving crypsis—avoidance of observation—that allows otherwise visible aquatic organisms to remain unnoticed by other organisms such as predators or prey.
Vision is an important sensory system for most species of fish. Fish eyes are similar to the eyes of terrestrial vertebrates like birds and mammals, but have a more spherical lens. Birds and mammals normally adjust focus by changing the shape of their lens, but fish normally adjust focus by moving the lens closer to or further from the retina. Fish retinas generally have both rod cells and cone cells, and most species have colour vision. Some fish can see ultraviolet and some are sensitive to polarised light.
Opisthoproctus soleatus is a species of fish in the family Opisthoproctidae. It was first described in 1888 by Léon Vaillant. The species lives in most tropical seas, but is more common in the eastern Atlantic, from western Ireland to Mauritania and from Sierra Leone to Angola, and also in the South China Sea. O. soleatus can grow to a standard length of 10.5 centimetres (4.1 in) and usually live from about 500 to 700 metres deep.
Saccopharynx lavenbergi is a species of gulper eel, also known as the whiptail gulper. This fish is known for its large mouth and long whiplike tail. This species is not commonly found in the wild, with fewer than twenty sightings over 30 years of ROV operation by MBARI. Even though it has rarely been sighted, this gulper eel was chosen to be the logo for MBARI.
Nanomia bijuga, first described by Stefano Delle Chiaje in 1844 and originally named Physsophora bijuga, is a species of mesopelagic siphonophore in the family Agalmatidae As with all members of the siphonophorae order, it is a colonial organism composed of individual zooids. N. bijuga has a fairly broad distribution, and has been observed in the coastal waters off of North America and Europe. The species has been found to occupy both epipelagic and mesopelagic depths. They utilize specialized swimming zooids for both propulsion and escape behaviors. Similar to other siphonophores, Nanomia bijuga employ stinging tentacles for hunting and defense. They primarily feed on small crustaceans, especially krill.
