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.
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.
Demersal fish,also known as groundfish,live and feed on or near the bottom of seas or lakes. They occupy the sea floors and lake beds,which usually consist of mud,sand,gravel or rocks. In coastal waters,they are found on or near the continental shelf,and in deep waters,they are found on or near the continental slope or along the continental rise. They are not generally found in the deepest waters,such as abyssal depths or on the abyssal plain,but they can be found around seamounts and islands. The word demersal comes from the Latin demergere,which means to sink.
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.
The Portuguese dogfish or Portuguese shark,is a species of sleeper shark of the family Somniosidae. This globally distributed species has been reported down to a depth of 3,675 m (12,057 ft),making it the deepest-living shark known. It inhabits lower continental slopes and abyssal plains,usually staying near the bottom. Stocky and dark brown in color,the Portuguese dogfish can be distinguished from similar-looking species by the small spines in front of its dorsal fins. Its dermal denticles are also unusual,resembling the scales of a bony fish. This species typically reaches 0.9–1 m (3.0–3.3 ft) in length;sharks in the Mediterranean Sea are much smaller and have distinct depth and food preferences.
Hotspot Ecosystem Research and Man's Impact On European Seas (HERMIONE) is an international multidisciplinary project,started in April 2009,that studies deep-sea ecosystems. HERMIONE scientists study the distribution of hotspot ecosystems,how they function and how they interconnect,partially in the context of how these ecosystems are being affected by climate change and impacted by humans through overfishing,resource extraction,seabed installations and pollution. Major aims of the project are to understand how humans are affecting the deep-sea environment and to provide policy makers with accurate scientific information,enabling effective management strategies to protect deep sea ecosystems. The HERMIONE project is funded by the European Commission's Seventh Framework Programme,and is the successor to the HERMES project,which concluded in March 2009.
The following outline is provided as an overview of and topical guide to fisheries:
Baited remote underwater video (BRUV) is a system used in marine biology research. By attracting fish into the field of view of a remotely controlled camera,the technique records fish diversity,abundance and behaviour of species. Sites are sampled by video recording the region surrounding a baited canister which is lowered to the bottom from a surface vessel or less commonly by a submersible or remotely operated underwater vehicle. The video can be transmitted directly to the surface by cable,or recorded for later analysis.
Torquaratoridae is a family of acorn worms (Hemichordata) that lives in deep waters between 350 and 4000 meters. They can grow up to three feet in length and have semitransparent gelatinous bodies,often brightly colored.
The short beard codling is a species of marine bony fish in the family Moridae. Native to the western Atlantic Ocean,it is found on the continental slope at depths between 50 and 1,620 m.
Neolithodes diomedeae is a species of king crab which is found in the eastern Pacific Ocean,the southwestern Atlantic Ocean,and the Bellingshausen and Scotia Seas in the Southern Ocean. They occur from 200 to 2,454 m.
Alan John Jamieson is a Scottish marine biologist,engineer,explorer and author,best known for his deep-sea exploration and study of life at the deepest places in the oceans. He is known for extensive use of deep-sea landers to establish the maximum depth and community dynamics of many organismal groups,as well as the discovery of many new species and highlighting the presence of anthropogenic impacts at full ocean depth. During the Five Deeps Expedition,and follow on expeditions in 2020,he completed various dives in a manned submersible to some of the deepest places in the world. He has published over 100 scientific papers and participated in 65 deep-sea expeditions.
Bathypolypus sponsalis,commonly called the globose octopus,is a deep sea cephalopod that can be found in both the eastern Atlantic Ocean and the Mediterranean Sea. It possesses many morphological traits adapted to a deep sea environment,including large eggs,reduced gills,no ink sac,and subgelatinous tissues. A distinguishing factor are the relatively large reproductive organs. Their diet consists of predominantly crustaceans and molluscs,but they sometimes consume fish as well. Bathypolypus sponsalis usually dies quickly after reproduction and only spawns once in their lifetime. Sexually mature females have a mantle length of at least 34 mm and sexually mature males have a mantle length of about 24 mm. Juveniles are white and transition to dark brown then to dark purple once maturity is reached.
Cataetyx alleni,sometimes called Allen's brotula,is a species of fish in the family Bythitidae.
The salmon smooth-head,also called the deepsea slickhead,is a species of fish in the family Alepocephalidae.
Günther's grenadier is a species of deep-sea fish in the family Macrouridae.
The bigeye rockling is a species of fish in the family Lotidae.
Bigelow's ray,also called the chocolate skate or Bigelow's skate,is a species of skate in the family Rajidae. It is named in honour of the oceanographer Henry Bryant Bigelow.
The rough abyssal grenadier is a species of deep-sea grenadier fish in the family Macrouridae. First described as a separate species in 1974,the rough abyssal grenadier was historically confused with its congener,Coryphaenoides armatus. Unlike C. armatus,which has been recorded in the waters of the Atlantic,Pacific,Indian,and Southern oceans,observations of C. yaquinae have been confined exclusively to the Pacific ocean. C. yaquinae tends to inhabit abyssopelagic depths between 3,400 and 5,800 meters. However,observations of C. yaquinae have been made as deep as 7,000 meters (23,000 ft) below sea level.
The white-headed hagfish is a species of jawless fish of the family Myxinidae (hagfish).
