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.
Cetomimidae is a family of small, deep-sea beryciform ray-finned 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.
Sabertooth or sabretooth fish are small, fierce-looking deep-sea aulopiform fish comprising the family Evermannellidae. The family is small, with just eight species in three genera represented; they are distributed throughout tropical to subtropical waters of the Atlantic, Indian, and Pacific Oceans.
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, 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 bigeye thresher is a species of thresher shark, family Alopiidae, found in temperate and tropical oceans worldwide. Like the other thresher sharks, nearly half its total length consists of the elongated upper lobe of the tail fin. Its common name comes from its enormous eyes, which are placed in keyhole-shaped sockets that allow them to be rotated upward. This species can also be distinguished by a pair of deep grooves on the top of its head, from which its scientific name is derived.
Nomeus gronovii, the man-of-war fish or bluebottle fish, is a species of fish in the family Nomeidae, the driftfish. It is a distinct species characterized by an elongated body, large eyes, and blackish-blue stripes, growing up to 39 cm long. Inhabiting warm, deep pelagic zones of the Atlantic, Pacific, and Indian Oceans between 200 and 1,000 meters deep, this fish lives within the tentacles of the Portuguese man o' war, feeding on its tentacles and gonads. Although it possesses resistance to the toxin produced by the man o' war, this species actively avoids larger tentacles and occasionally feeds on smaller ones. The species' agility, high vertebrae count, and specialized skin features contribute to its toxin avoidance. It is the sole known species in its genus and undergoes a lifestyle shift from pelagic to demersal as it matures. Reproduction involves egg release by females, yielding larvae adapted to open water life, with each female capable of producing 100 to 1000 offspring.
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 pearleyes are a family, Scopelarchidae, of aulopiform ray-finned fish, distinguished by their unique visual system, with two retinas in each eye.
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.
Bathylychnops exilis, the Javelin spookfish, is a species of barreleye found in the northern Pacific and in the eastern Atlantic Ocean near the Azores where it is found at depths of around 640 metres (2,100 ft). This species grows to a length of 50 centimetres (20 in) SL.
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.
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.
