An abyssal plain is an underwater plain on the deep ocean floor, usually found at depths between 3,000 and 6,000 metres. Lying generally between the foot of a continental rise and a mid-ocean ridge, abyssal plains cover more than 50% of the Earth's surface. They are among the flattest, smoothest, and least explored regions on Earth. Abyssal plains are key geologic elements of oceanic basins.
The abyssal zone or abyssopelagic zone is a layer of the pelagic zone of the ocean. The word abyss comes from the Greek word ἄβυσσος (ábussos), meaning "bottomless". At depths of 4,000–6,000 m (13,000–20,000 ft), this zone remains in perpetual darkness. It covers 83% of the total area of the ocean and 60% of Earth's surface. The abyssal zone has temperatures around 2–3 °C (36–37 °F) through the large majority of its mass. The water pressure can reach up to 76 MPa.
The tripod fish or tripod spiderfish, Bathypterois grallator, is a deep-sea benthic fish in the family Ipnopidae found at lower latitudes. It is now relatively well known from photographs and submersible observations, and seems to prefer to perch on the ooze using much elongated fin rays in the tail and two pelvic fins to stand, facing upstream with the pectoral fins turned forward so the outthrust projecting fin rays resemble multiple antennae, and are indeed used as tactile organs. B. grallator is hermaphroditic. At least 18 species are placed in the genus Bathypterois, several of which have similar appearance and behavior to B. grallator. B. grallator is the largest member of its genus, commonly exceeding a standard length of 30 cm (12 in) and reaching up to 43.4 cm (17.1 in).
The Atlantic horse mackerel, also known as the European horse mackerel or common scad, is a species of jack mackerel in the family Carangidae, which includes the jacks, pompanos and trevallies. It is found in the eastern Atlantic Ocean off Europe and Africa and into the south-eastern Indian Ocean. It is an important species in commercial fisheries and is listed as a Vulnerable species on The IUCN Red List of Threatened Species.
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 black dogfish is a species of dogfish shark in the family Etmopteridae. It is common over the outer continental shelf and continental slope at depths of 180–2,250 m (590–7,380 ft). Females generally inhabit deeper water than males, and depending on the region, smaller sharks may occur at different depths than larger ones. This species is distributed widely in the Atlantic Ocean, from Greenland and Iceland to Virginia and West Africa in the north, and off southwestern Africa and Argentina in the south. The largest member of its family, the black dogfish, typically measures 60–75 cm (24–30 in) long. It has a stocky, dark brown body that is darker below than above, and bears scattered, minute bioluminescent organs. Its two dorsal fins are preceded by stout spines, and the anal fin is absent.
The Ipnopidae are a family of fishes in the order Aulopiformes. They are small, slender fishes, with maximum length ranging from about 10 to 40 cm. They are found in temperate and tropical deep waters of the Atlantic, Indian, and Pacific Oceans.
The abyssal grenadier, Coryphaenoides armatus, is an abyssal fish of the genus Coryphaenoides, found in all the world's oceans, at depths between 800 and 4,000 metres. Its adult length is 20 to 40 centimetres, although Fishbase gives lengths up to 1 metre. The abyssal grenadier's body is unique in that it contains two dorsal spines and about 124 dorsal soft rays, which are the flexible jointed rays supporting a fin nearest to the back in the spinal column. It has no anal spines, but has 115 anal soft rays along its body. The head and eyes of this fish are very large, while the mouth is very small. The color of the abyssal grenadier is brown apart from the abdomen, which is bluish.
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.
The crocodile shark is a species of mackerel shark and the only extant member of the family Pseudocarchariidae. A specialized inhabitant of the mesopelagic zone, the crocodile shark can be found worldwide in tropical waters from the surface to a depth of 590 m (1,940 ft). It performs a diel vertical migration, staying below a depth of 200 m (660 ft) during the day and ascending into shallower water at night to feed. Typically measuring only 1 m (3.3 ft) in length, the crocodile shark is the smallest living mackerel shark. It can be distinguished by its elongated cigar-shaped body, extremely large eyes, and relatively small fins.
The spinner shark is a type of requiem shark, in the family Carcharhinidae, named for the spinning leaps it makes as a part of its feeding strategy. This species occurs in tropical and warm temperate waters worldwide, except for in the eastern Pacific Ocean. It is found from coastal to offshore habitats to a depth of 100 m (330 ft), though it prefers shallow water. The spinner shark resembles a larger version of the blacktip shark, with a slender body, long snout, and black-marked fins. This species can be distinguished from the blacktip shark by the first dorsal fin, which has a different shape and is placed further back, and by the black tip on the anal fin. It attains a maximum length of 3 m (9.8 ft).
The velvet belly lanternshark is a species of dogfish shark in the family Etmopteridae. One of the most common deepwater sharks in the northeastern Atlantic Ocean, the velvet belly is found from Iceland and Norway to Gabon and South Africa at a depth of 20–2,490 m (66–8,169 ft). A small shark generally no more than 45 cm (18 in) long, the velvet belly is so named because its black underside is abruptly distinct from the brown coloration on the rest of its body. The body of this species is fairly stout, with a moderately long snout and tail, and very small gill slits. Like other lanternsharks, the velvet belly is bioluminescent, with light-emitting photophores forming a species-specific pattern over its flanks and abdomen. The ventral photophores are thought to function in counter-illumination, which camouflages the shark against predators and prey. The bioluminescent flank markings may play a role in intraspecific communication.
Sebastes capensis, the false jacopever or Cape redfish, is a species of marine ray-finned fish belonging to the subfamily Sebastinae, the rockfishes, part of the family Scorpaenidae. It is found in the South Atlantic Ocean and may also occur off southern and western South America.
The comber is a species of marine ray-finned fish from the family Serranidae, the sea basses. It is widely distributed in the eastern North and South Atlantic Oceans and into the southwestern Indian Ocean. It is caught for food and fishmeal in some parts of its range.
The mackerel scad, or speedo, is a species of fish of the family, Carangidae. While it can be considered gamefish, it is usually used as bait. It is popular for consumption in Hawaiʻi, the Philippines and the U.A.E. In Hawaiʻi, mackerel scad are called ʻopelu. In the Philippines they are called galunggong.
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).
The Atlantic flyingfish is a flying fish in the family Exocoetidae. It was first described by the French zoologist, Achille Valenciennes in a 22-volume work entitled Histoire naturelle des poissons, which was a collaboration with fellow zoologist Georges Cuvier.
Merluccius capensis is a ray-finned fish in the genus Merluccius, found in the south-eastern Atlantic Ocean, along the coast of South Africa. It is a long, lean fish with a large head, similar in appearance to the European hake and the deep-water Cape hake. By day, it lives close to the bottom on the continental shelf and upper slope at depths not usually exceeding 400 m (1,300 ft); it makes a large, daily vertical migration rising at night to feed in the nectonic zone, and it also migrates southwards in spring and northwards in autumn. It is an important commercial fish species in southern Africa.
Bathypterois is a genus of deepsea tripod fishes. They are a diverse genus that belong to the greater family Ipnopidae and order Aulopiformes. They are distinguished by having two elongated pelvic fins and an elongated caudal fin, which allow them to move and stand on the ocean floor, much like a tripod, hence the common name. Bathypterois are distributed worldwide with some particular species of the genus having specialized environmental niches, such as lower dissolved oxygen concentrations. Bathypterois have a reduced eye size, highly specified extended fins, and a mouth adapted to filter feeding. They are filter feeders whose main food source is benthopelagic planktonic calanoid copepods, but some variation is seen with maturity in secondary food sources. Bathypterois use their three elongated fins for a wide range of motion from landing to standing on the ocean floor to catching prey, for which these fins serve as specialized perceptory organs. Bathypterois have both male and female gonads at once making, them simultaneous hermaphrodites, whose gonads go through five stages of development following seasonal autumn spawning.
The sand steenbras or striped seabream is a species of marine fish in the family Sparidae, colloquially known as the common bastardfish for nipping at the legs of swimmers. It is found in shallow water in the Mediterranean Sea and in the eastern Atlantic Ocean from France to South Africa. It also occurs in the Red Sea and off the coast of Mozambique in the Indian Ocean. The IUCN has assessed its conservation status as being of "least concern".
