Rhinogobius flumineus(Hamamatsu,Shizuoka,Japan)

Demersal fish, also known as groundfish, live and feed on or near the bottom of

sea The sea, connected as the world ocean or simply the ocean, is the body of salty water that covers approximately 71% of the Earth's surface. The word sea is also used to denote second-order sections of the sea, such as the Mediterranean Sea, ...

s or

lake A lake is an area filled with water, localized in a basin, surrounded by land, and distinct from any river or other outlet that serves to feed or drain the lake. Lakes lie on land and are not part of the ocean, although, like the much large ...

s (the demersal zone).Walrond
Carl . "Coastal fish - Fish of the open sea floor"
Te Ara - the Encyclopedia of New Zealand. Updated 2 March 2009 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 An abyssal plain is an underwater plain on the deep ocean floor, usually found at depths between and . 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 ...

, but they can be found around seamounts and islands. The word ''demersal'' comes from the

Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through ...

''demergere'', which means ''to sink''. Demersal fish are bottom feeders. They can be contrasted with pelagic fish which live and feed away from the bottom in the open water column. Demersal fish fillets contain little fish oil (one to four percent), whereas pelagic fish can contain up to 30 percent.

Types

Demersal fish can be divided into two main types: strictly benthic fish which can rest on the sea floor, and benthopelagic fish which can float in the water column just above the sea floor. Benthopelagic fish have neutral buoyancy, so they can float at depth without much effort, while strictly benthic fish are denser, with negative buoyancy so they can lie on the bottom without any effort. Most demersal fish are benthopelagic. As with other bottom feeders, a mechanism to deal with substrate is often necessary. With demersal fish the sand is usually pumped out of the mouth through the

gill slit Gill slits are individual openings to gills, i.e., multiple gill arches, which lack a single outer cover. Such gills are characteristic of cartilaginous fish such as sharks and rays, as well as deep-branching vertebrates such as lampreys. In co ...

. Most demersal fish exhibit a flat ventral region so as to more easily rest their body on the substrate. The exception may be the flatfish, which are laterally depressed but lie on their sides. Also, many exhibit what is termed an "inferior" mouth, which means that the mouth is pointed downwards; this is beneficial as their food is often below them in the substrate. Those bottom feeders with upward-pointing mouths, such as

stargazer Stargazer may refer to: * an observational astronomer, particularly an amateur Aerospace * Stargazer (aircraft), a Lockheed L-1011 airliner used to launch the Pegasus rocket * Orbiting Astronomical Observatory 2, nicknamed Stargazer, the first ...

s, tend to seize swimming prey.

Benthic fish

Benthic fish are denser than water, so they can rest on the sea floor. They either lie-and-wait as ambush predators, at times covering themselves with sand or otherwise camouflaging themselves, or move actively over the bottom in search for food. Benthic fish which can bury themselves include dragonets, flatfish and stingrays. Flatfish are an

order Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of ...

ray-finned Actinopterygii (; ), members of which are known as ray-finned fishes, is a class of bony fish. They comprise over 50% of living vertebrate species. The ray-finned fishes are so called because their fins are webs of skin supported by bony or ho ...

benthic fishes which lie flat on the ocean floor. Examples are flounder, sole, turbot, plaice, and halibut. The adult fish of many species have both eyes on one side of the head. When the fish hatches, one eye is located on each side of its head. But as the fish grows from the larval stage, one eye migrates to the other side of the body as a process of metamorphosis. The flatfish then changes its habits, and camouflages itself by lying on the bottom of the ocean floor with both eyes facing upwards. The side to which one eye migrates depends on the species; with some species both eyes are ultimately on the left side, whereas with other species the eyes are on the right. File:Pseudopleuronectes americanus.jpg, Flounder have both eyes on one side of their head File:Flounder camo md.jpg, Some flatfish can camouflage themselves on the ocean floor File:Taeniura lymma 2.jpg, Bluespotted ribbontail rays migrate in schools onto shallow sands to feed on mollusks, shrimps, crabs and worms. File:Sphyrna mokarran head.jpg, The great hammerhead detects the electrical signatures of stingrays buried in the sand and pins them with its "hammer". Flounder ambush their prey, feeding at soft muddy area of the sea bottom, near bridge piles, docks, artificial and coral reefs. Their diet consists mainly of fish spawn,

crustacean Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapoda, decapods, ostracoda, seed shrimp, branchiopoda, branchiopods, argulidae, fish lice, krill, remipedes, isopoda, isopods, barnacles, copepods, ...

s, polychaetes and small fish. The great hammerhead swings its head in broad angles over the sea floor to pick up the electrical signatures of stingrays buried in the sand. It then uses its "hammer" to pin down the stingray.Hammerschlag, Rick
Sandy Plains: Great Hammerhead Shark
''ReefQuest Centre for Shark Research''. Retrieved: 6 June 2022. File:Pacific hagfish Myxine.jpg, Pacific hagfish resting on bottom. Hagfish coat themselves and any dead fish they find with noxious slime making them inedible to other species. File:Bathypterois grallator.jpg, The tripodfish ('' Bathypterois grallator''), a species of spiderfish, uses its fin extensions to "stand" on the bottom. File:Caelorinchus mirus (Gargoyle fish).gif,

Gargoyle fish The gargoyle fish or small-eye rattail, ''Coelorinchus mirus'', is a species of rattail found around southeast Australia and between New Zealand and the Chatham Islands The Chatham Islands ( ) (Moriori: ''Rēkohu'', 'Misty Sun'; mi, Whare ...

File:Fringe-Lipped Flathead.jpg, The fringe-lipped flathead is found in estuaries Some fishes do not fit into the above classification. For example, the family of nearly blind

spiderfish The Ipnopidae (deepsea tripod fishes) are a family of fishes in the order Aulopiformes. They are small, slender fishes, with maximum length ranging from about . They are found in temperate and tropical deep waters of the Atlantic, Indian, an ...

es, common and widely distributed, feed on benthopelagic zooplankton. Yet they are strictly benthic fish, since they stay in contact with the bottom. Their fins have long rays they use to "stand" on the bottom while they face the current and grab zooplankton as it passes by. The bodies of benthic fish are adapted for ongoing contact with the sea floor. Swimbladders are usually absent or reduced, and the bodies are usually flattened in one way or another.Moyle and Cech, 2004, p. 13 Following Moyle and Cech (2004) they can be divided into five overlapping body shapes:

Benthopelagic fish

Benthopelagic fish inhabit the water just above the bottom, feeding on

benthos Benthos (), also known as benthon, is the community of organisms that live on, in, or near the bottom of a sea, river, lake, or stream, also known as the benthic zone.zooplankton. Most demersal fish are benthopelagic. Deep sea benthopelagic teleosts all have swimbladders. The dominant species,

rattail Grenadiers or rattails are generally large, brown to black gadiform marine fish of the subfamily Macrourinae, the largest subfamily of the family Macrouridae. Found at great depths from the Arctic to Antarctic, members of this subfamily are amon ...

s and cusk eels, have considerable biomass. Other species include deep sea cods ( morids), deep sea eels,

halosaur Halosaurs are eel-shaped fishes found only at great ocean depths. As the family Halosauridae, halosaurs are one of two families within the order Notacanthiformes; the other being the deep-sea spiny eels, Notacanthidae. Halosaurs are thought to h ...

s and notacanths.Bone 2008, p. 43. Benthopelagic sharks, like the deep sea squaloid sharks, achieve neutral buoyancy with the use of large oil-filled livers.Bone 2008, p. 42. Sharks adapt well to fairly high pressures. They can often be found on slopes down to about 2000 metres, scavenging on food falls such as dead whales. However, the energy demands of sharks are high, since they need to swim constantly and maintain a large amount of oil for buoyancy. These energy needs cannot be met in the extreme oligotrophic conditions that occur at great depths. Shallow water stingrays are benthic, and can lie on the bottom because of their negative buoyancy. Deep sea stingrays are benthopelagic, and like the squaloids have very large livers which give them neutral buoyancy. Benthopelagic fish can be divided into flabby or robust body types. Flabby benthopelagic fishes are like bathypelagic fishes; they have a reduced body mass, and low metabolic rates, expending minimal energy as they lie and wait to

ambush An ambush is a long-established military tactic in which a combatant uses an advantage of concealment or the element of surprise to attack unsuspecting enemy combatants from concealed positions, such as among dense underbrush or behind moun ...

prey. An example of a flabby fish is the cusk-eel ''Acanthonus armatus'', a predator with a huge head and a body that is 90 percent water. This fish has the largest ears ( otoliths) and the smallest brain in relation to its body size of all known vertebrates.Fine ML, Horn MH and Cox B (1987
"''Acanthonus armatus'', a Deep-Sea Teleost Fish with a Minute Brain and Large Ears"
''Proceedings of the Royal Society B'', 230(1259)257-265. Deepwater benthopelagic fish are robust, muscular swimmers that actively cruise the bottom searching for prey. They often live around features, such as seamounts, which have strong currents. Commercial examples are the orange roughy and Patagonian toothfish.

Habitats

The edge of the continental shelf marks the boundary where the shelf gives way to, and then gradually drops into abyssal depths. This edge marks the boundary between coastal, relatively shallow, benthic habitats, and the deep benthic habitats. Coastal demersal fishes live on the bottom of inshore waters, such as bays and estuaries, and further out, on the floor of the continental shelf. Deep water demersal fish live beyond this edge, mostly down the continental slopes and along the continental rises which drop to the

s. This is the

continental margin A continental margin is the outer edge of continental crust abutting oceanic crust under coastal waters. It is one of the three major zones of the ocean floor, the other two being deep-ocean basins and mid-ocean ridges. The continental margin ...

, constituting about 28% of the total oceanic area.P. J. Cook, Chris Carleton (2000) "Continental Shelf Limits: The Scientific and Legal Interface", Other deep sea demersal fish can also be found around seamounts and islands. The term ''bathydemersal fish'' is sometimes used instead of "deep water demersal fish". ''Bathydemersal'' refers to demersal fish which live at depths greater than 200 metres. The term ''epibenthic'' is also used to refer to organism that live on top of the ocean floor, as opposed to those that burrow into the seafloor substrate. However the terms ''mesodemersal'', ''epidemersal'', ''mesobenthic'' and ''bathybenthic'' are not used.

Coastal

Coastal demersal fish are found on or near the seabed of coastal waters between the shoreline and the edge of the continental shelf, where the shelf drops into the deep ocean. Since the continental shelf is generally less than 200 metres deep, this means that coastal waters are generally epipelagic. The term includes demersal reef fish and demersal fish that inhabit

estuaries An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environme ...

, inlets and

bay A bay is a recessed, coastal body of water that directly connects to a larger main body of water, such as an ocean, a lake, or another bay. A large bay is usually called a gulf, sea, sound, or bight. A cove is a small, circular bay with a na ...

s. File:Mangrovejack.jpg, The mangrove jack eats

s File:Puffer Fish DSC01257.JPG, Many puffer fish species crush the shells of molluscs File:Opsanus beta 1.jpg, The venomous toadfish, a benthic ambush predator, blends into sandy or muddy bottoms. File:Titan Triggerfish.jpg,

Triggerfish Triggerfish are about 40 species of often brightly colored fish of the family Balistidae. Often marked by lines and spots, they inhabit tropical and subtropical oceans throughout the world, with the greatest species richness in the Indo-Pacif ...

use a jet of water to uncover sand dollars buried in sand Young mangrove jacks, a sought after eating and sport fish, dwell in

around mangrove roots, fallen trees, rock walls, and any other snag areas where smaller prey reside for protection. When they mature, they migrate into open waters, sometimes hundreds of kilometres from the coast to spawn. Uranoscopus sulphureus

Stargazer Stargazer may refer to: * an observational astronomer, particularly an amateur Aerospace * Stargazer (aircraft), a Lockheed L-1011 airliner used to launch the Pegasus rocket * Orbiting Astronomical Observatory 2, nicknamed Stargazer, the first ...

s are found worldwide in shallow waters. They have eyes on top of their heads and a large upward-facing mouth. They bury themselves in sand, and leap upwards to ambush benthopelagic fish and

invertebrate Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chorda ...

s that pass overhead. Some species have a worm-shaped lure growing out of the floor of the mouth, which they wiggle to attract prey. Stargazers are venomous and can deliver electric shocks. They have been called "the meanest things in creation." Other examples of coastal demersal fish are cod, plaice, monkfish and sole.

Deep water

Deep water demersal fish occupy the benthic regions beyond the continental margins. On the continental slope, demersal fishes are common. They are more diverse than coastal demersal fish, since there is more habitat diversity. Further out are the

s. These flat, featureless regions occupy about 40 percent of the ocean floor. They are covered with

sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sand ...

but largely devoid of benthic life (

benthos Benthos (), also known as benthon, is the community of organisms that live on, in, or near the bottom of a sea, river, lake, or stream, also known as the benthic zone.seamounts) can intercept deep sea currents, and cause productive upwellings which support benthic fish. Undersea mountain ranges can separate underwater regions into different ecosystems.Moyle and Cech, 2004, p. 587

Rattail Grenadiers or rattails are generally large, brown to black gadiform marine fish of the subfamily Macrourinae, the largest subfamily of the family Macrouridae. Found at great depths from the Arctic to Antarctic, members of this subfamily are amon ...

s and brotulas are common, and other well-established families are eels, eelpouts, hagfishes, greeneyes, batfishes and lumpfishes. The bodies of deep water demersal fishes are muscular with well developed organs. In this way they are closer to mesopelagic fishes than bathypelagic fishes. In other ways, they are more variable. Photophores are usually absent, eyes and swimbladders range from absent to well developed. They vary in size, and larger species, greater than one metre, are not uncommon. Giant grenadier

Deep sea demersal fish are usually long and narrow. Many are eels or shaped like eels. This may be because long bodies have long lateral lines. Lateral lines detect low-frequency sounds, and some demersal fishes have muscles that drum such sounds to attract mates.Haedrich RL (1996
"Deep-water fishes: evolution and adaptation in the earth's largest living spaces"
''Journal of Fish Biology'' 49(sA):40-53. Smell is also important, as indicated by the rapidity with which demersal fish find traps baited with

bait fish 300px, Feeder Goldfish are common baitfish. Bait fish (or baitfish) are small-sized fish caught and used by anglers as bait to attract larger predatory fish, particularly game fish. Baitfish species are typically those that are common and bre ...

. The main diet of deep sea demersal fish is

s of the deep sea

benthos Benthos (), also known as benthon, is the community of organisms that live on, in, or near the bottom of a sea, river, lake, or stream, also known as the benthic zone.carrion. Smell, touch and lateral line sensitivities seem to be the main sensory devices for locating these.Moyle and Cech, 2004, p. 588 Like coastal demersal fish, deep sea demersal fish can be divided into benthic fish and benthopelagic fish, where the benthic fish are negatively buoyant and benthopelagic fish are neutrally buoyant. The availability of plankton for food diminishes rapidly with depth. At , the biomass of plankton is typically about 1 percent of that at the surface, and at about 0.01 percent. Given there is no sunlight, energy enters deep water zones as organic matter. There are three main ways this happens. Firstly, organic matter can move into the zone from the continental landmass, for example, through currents that carry the matter down rivers, then plume along the continental shelf and finally spill down the continental slope. Other matter enters as particulate matter raining down from the overhead water column in the form of marine snow, or as sinking overhead plant material such as eelgrass, or as "large particles" such as dead fish and whales sinking to the bottom. A third way energy can arrive is through fish, such as vertically migrating mesopelagic fishes that can enter into the demersal zone as they ascend or descend. The demersal fish and invertebrates consume organic matter that does arrive, break it down and recycle it. A consequence of these energy delivery mechanisms is that the abundance of demersal fish and invertebrates gradually decrease as the distance from continental shorelines increases.Moyle and Cech, 2004, p. 594 Although deep water demersal fish species are not generally picky about what they eat, there is still some degree of specialisation. For example, different fish have different mouth sizes, which determines the size of the prey they can handle. Some feed mostly on benthopelagic organisms. Others fed mostly on epifauna (invertebrates on top of the seafloor surface, also called ''epibenthos''), or alternatively on

infauna Fauna is all of the animal life present in a particular region or time. The corresponding term for plants is ''flora'', and for fungi, it is ''funga''. Flora, fauna, funga and other forms of life are collectively referred to as '' biota''. Zool ...

(invertebrates that burrow into the seafloor substrate). Infauna feeders can have considerable sediment in their stomachs. Scavengers, such as

snubnosed eel The snubnosed eel, ''Simenchelys parasitica'', also known as the pug-nosed eel, slime eel, or snub-nose parasitic eel, is a species of deep-sea eel and the only member of its genus. Some authors classify it as the sole member of the subfamily Sim ...

s and hagfish, also eat infauna as a secondary food source.Sedberry GR and Musick JA (1978
"Feeding strategies of some demersal fishes of the continental slope and rise off the mid-Atlantic coast of the USA"
''Marine Biology'', 44:357-375. File:Simenchelys parasiticus.jpg,

Snubnosed eel The snubnosed eel, ''Simenchelys parasitica'', also known as the pug-nosed eel, slime eel, or snub-nose parasitic eel, is a species of deep-sea eel and the only member of its genus. Some authors classify it as the sole member of the subfamily Sim ...

File:Ilyophis brunneus.jpg,

Muddy arrowtooth eel The muddy arrowtooth eel, ''Ilyophis brunneus'', is a cutthroat eel in the family Synaphobranchidae Cutthroat eels are a family, Synaphobranchidae, of eels, the only members of the suborder Synaphobranchoidei. They are found worldwide in temp ...

File:Urophycis tenuis.jpg, White hake Some feed on carrion. Cameras show that when a dead fish is placed on the bottom, vertebrate and invertebrate scavengers appear very quickly. If the fish is large, some scavengers burrow in and eat it from the inside out. Some fish, such as grenadiers, also appear and start feeding on the scavenging invertebrates and amphipods. Other specialization is based on depth distribution. Some of the more abundant upper continental slope fish species, such as

cutthroat eel Cutthroat eels are a family, Synaphobranchidae, of eels, the only members of the suborder Synaphobranchoidei. They are found worldwide in temperate and tropical seas. Cutthroat eels range from in length. They are bottom-dwelling fish, found in ...

and longfinned hake, mainly feed on

epipelagic fish 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 do live on or near the bottom, and reef fish that are associated with coral re ...

. But generally, the most abundant deep water demersal fish species feed on invertebrates.Moyle and Cech, 2004, p. 595 At great depths, food scarcity and extreme pressure limits the ability of fish to survive. The deepest point of the ocean is about 11,000 metres. Bathypelagic fishes are not normally found below 3,000 metres. It may be that extreme pressures interfere with essential enzyme functions.Ryan
"Deep-sea creatures: The bathypelagic zone"
''Te Ara - the Encyclopedia of New Zealand''. Updated 21 September 2007. The deepest-living fish known, the strictly benthic '' Abyssobrotula galatheae'', eel-like and blind, feeds on benthic invertebrates. A living example was trawled from the bottom of the Puerto Rico Trench in 1970 from a depth of 8,370 metres (27,453 ft). In 2008, a shoal of 17 hadal snailfish, a species of deep water snailfish, was filmed by a UK-Japan team using remote operated landers at depths of in the

Japan Trench The Japan Trench is an oceanic trench part of the Pacific Ring of Fire off northeast Japan. It extends from the Kuril Islands to the northern end of the Izu Islands, and is at its deepest. It links the Kuril–Kamchatka Trench to the north and ...

in the Pacific. The fish were 30 centimetres long (12 in), and were darting about, using vibration sensors on their nose to catch shrimps. The team also reported that the appearance of the fish, unlike that of most deep sea fish, was surprisingly "cute", and that they were surprised by how active the fish were at these depths.

Demersal fisheries

Most demersal fish of commercial or recreational interest are coastal, confined to the upper 200 metres. Commercially important demersal food fish species include flatfish, such as flounder, sole, turbot, plaice, and halibut. Also important are cod, hake, redfish, haddock,

bass Bass or Basses may refer to: Fish * Bass (fish), various saltwater and freshwater species Music * Bass (sound), describing low-frequency sound or one of several instruments in the bass range: ** Bass (instrument), including: ** Acoustic bass gui ...

conger ''Conger'' ( ) is a genus of marine congrid eels. It includes some of the largest types of eels, ranging up to 2 m (6 ft) or more in length, in the case of the European conger. Large congers have often been observed by divers during ...

shark Sharks are a group of elasmobranch fish characterized by a cartilaginous skeleton, five to seven gill slits on the sides of the head, and pectoral fins that are not fused to the head. Modern sharks are classified within the clade Selachi ...

ray Ray may refer to: Fish * Ray (fish), any cartilaginous fish of the superorder Batoidea * Ray (fish fin anatomy), a bony or horny spine on a fin Science and mathematics * Ray (geometry), half of a line proceeding from an initial point * Ray (gr ...

s and chimaeras.Grainger RJK and Garcia SM (1996
"Chronicles of Marine Fishery Landings (1950-1994): Trend Analysis and Fisheries Potential"
'' FAO: Fisheries technical paper 359.'' Rome. . The following table shows the world capture production of some groups of demersal species in tonnes. Black sea bass inhabit US coasts from

Maine Maine () is a state in the New England and Northeastern regions of the United States. It borders New Hampshire to the west, the Gulf of Maine to the southeast, and the Canadian provinces of New Brunswick and Quebec to the northeast and nor ...

to NE

Florida Florida is a state located in the Southeastern region of the United States. Florida is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia, to the east by the Bahamas and Atlantic Ocean, and ...

and the eastern

Gulf of Mexico The Gulf of Mexico ( es, Golfo de México) is an ocean basin and a marginal sea of the Atlantic Ocean, largely surrounded by the North American continent. It is bounded on the northeast, north and northwest by the Gulf Coast of the United ...

, and are most abundant off the waters of New York. They are found in inshore waters (bays and sounds) and offshore in waters up to a depth of 130 m (425'). They spend most of their time close to the sea floor and are often congregated around bottom formations such as rocks,

man-made reef An artificial reef is a human-created underwater structure, typically built to promote marine life in areas with a generally featureless bottom, to control erosion, block ship passage, block the use of trawling nets, or improve surfing. Many re ...

s, wrecks, jetties, piers, and

bridge pilings A pile bridge is a structure that uses foundations consisting of long poles (referred to as piles), which are made of wood, concrete or steel and which are hammered into the soft soils beneath the bridge until the end of the pile reaches a hard ...

. Black sea bass are sought after recreational and commercial fish, and have been

overfished Overfishing is the removal of a species of fish (i.e. fishing) from a body of water at a rate greater than that the species can replenish its population naturally (i.e. the overexploitation of the fishery's existing fish stock), resulting in ...

. File:Hippoglossoides platessoides.jpg, American plaice are usually found between 90 and 250 metres (but have been found at 3000 m). They feed on small fishes and invertebrates. File:Atlantic cod.jpg, Atlantic cod are usually found between 150 and 200 metres, they are omnivorous and feed on invertebrates and fish, including young cod. File:Centropristis striata.png, Black sea bass File:Epinephelus malabaricus.jpg,

Grouper Groupers are fish of any of a number of genera in the subfamily Epinephelinae of the family Serranidae, in the order Perciformes. Not all serranids are called "groupers"; the family also includes the sea basses. The common name "grouper" ...

are ambush predators with a powerful sucking system that sucks their prey in from a distance

are often found around reefs. They have stout bodies and large mouths. They are not built for long-distance or fast swimming. They can be quite large, and lengths over a meter and weights up to 100 kg are not uncommon. They swallow prey rather than biting pieces off it. They do not have many teeth on the edges of their jaws, but they have heavy crushing tooth plates inside the

pharynx The pharynx (plural: pharynges) is the part of the throat behind the mouth and nasal cavity, and above the oesophagus and trachea (the tubes going down to the stomach and the lungs). It is found in vertebrates and invertebrates, though its st ...

. They lie in wait, rather than chasing in open water. They are found in areas of hard or consolidated substrate, and use structural features such as ledges, rocks, and coral reefs (as well as

artificial reef An artificial reef is a human-created underwater structure, typically built to promote marine life in areas with a generally featureless bottom, to control erosion, block ship passage, block the use of trawling nets, or improve surfing. Many ...

s like wrecks and sunken barges) as their habitat. Their mouth and

gill A gill () is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they ar ...

s form a powerful sucking system that sucks their prey in from a distance. They also use their mouth to dig into sand to form their shelters under big rocks, jetting it out through their gills. Their gill muscles are so powerful that it is nearly impossible to pull them out of their cave if they feel attacked and extend those muscles to lock themselves in. There is some research indicating that roving coral groupers (''Plectropomus pessuliferus'') sometimes cooperate with giant morays in hunting. File:Toothfish.jpg, The Patagonian toothfish is a robust benthopelagic fish File:Orange roughy.png, The orange roughy is also a robust benthopelagic fish File:Macruronus novaezelandiae.jpg, The

blue grenadier The blue grenadier (also known as hoki, blue hake, New Zealand whiptail, or whiptail hake, ''Macruronus novaezelandiae'') is a merluccid hake of the family Merlucciidae found around southern Australia and New Zealand, as well as off both the Atla ...

(hoki), a deep water demersal fish, is subjected to a large sustainable fishing industry in New Zealand. Deepwater benthopelagic fish are robust, muscular swimmers that actively cruise the bottom searching for prey. They often live around features, such as seamounts, which have strong currents. Commercial examples are the orange roughy and Patagonian toothfish. Because these fish were once abundant, and because their robust bodies are good to eat, these fish have been commercially harvested.

Conservation status

Major demersal fishery species in the

North Sea The North Sea lies between Great Britain, Norway, Denmark, Germany, the Netherlands and Belgium. An epeiric sea on the European continental shelf, it connects to the Atlantic Ocean through the English Channel in the south and the Norwegian ...

such as cod, plaice, monkfish and sole, are listed by the ICES as "outside safe biological limits." * The True Sole '' solea solea'' is sufficiently broadly distributed that it is not considered a threatened species; however, overfishing in Europe has produced severely diminished populations, with declining catches in many regions. For example, the western

English Channel The English Channel, "The Sleeve"; nrf, la Maunche, "The Sleeve" ( Cotentinais) or ( Jèrriais), ( Guernésiais), "The Channel"; br, Mor Breizh, "Sea of Brittany"; cy, Môr Udd, "Lord's Sea"; kw, Mor Bretannek, "British Sea"; nl, Het Ka ...

and

Irish Sea The Irish Sea or , gv, Y Keayn Yernagh, sco, Erse Sie, gd, Muir Èireann , Ulster-Scots: ''Airish Sea'', cy, Môr Iwerddon . is an extensive body of water that separates the islands of Ireland and Great Britain. It is linked to the C ...

sole fisheries face potential collapse according to data in the UK Biodiversity Action Plan. * Sole, along with the other major bottom-feeding fish in the North Sea such as cod, monkfish, and plaice, is listed by the ICES as "outside safe biological limits." Moreover, they are growing less quickly now and are rarely older than six years, although they can reach forty. World stocks of large predatory fish and large ground fish such as sole and flounder were estimated in 2003 to be only about 10% of pre-industrial levels. According to the

World Wildlife Fund The World Wide Fund for Nature Inc. (WWF) is an international non-governmental organization founded in 1961 that works in the field of wilderness preservation and the reduction of human impact on the environment. It was formerly named the W ...

in 2006, "of the nine sole stocks, seven are overfished with the status of the remaining two unknown." Data is insufficient to assess the remaining stocks; however, landings for all stocks are at or near historical lows." * World stocks of large predatory fish and large ground fish such as sole and flounder were estimated in 2003 to be only about 10% of pre-industrial levels, largely due to overfishing. Most overfishing is due to the extensive activities of the fishing industry. Current research indicate that the flounder population could be as low as 15 million due to heavy overfishing and industrial pollution along the Gulf of Mexico surrounding the coast of Texas. * Seafood Watch have placed on their list of seafood that

sustainability Specific definitions of sustainability are difficult to agree on and have varied in the literature and over time. The concept of sustainability can be used to guide decisions at the global, national, and individual levels (e.g. sustainable livi ...

-minded consumers should avoid the following demersal fish: sturgeon (imported wild), Chilean seabass, cod (Atlantic, imported Pacific), flounder (Atlantic), halibut (Atlantic), sole (Atlantic),

grouper Groupers are fish of any of a number of genera in the subfamily Epinephelinae of the family Serranidae, in the order Perciformes. Not all serranids are called "groupers"; the family also includes the sea basses. The common name "grouper" ...

, monkfish, orange roughy, demersal

, red snapper and tilapia (Asia farmed).

Notes

References

* Bone Q and Moore RH (2008
''Biology of Fishes''
Taylor & Francis Group. * Merrett NR and Haedrich RL (1997
''Deep-sea demersal fish and fisheries''
Chapman and Hall. . * Moyle, PB and Cech, JJ (2004) ''Fishes, An Introduction to Ichthyology.'' 5th Ed, Benjamin Cummings.
Demersal fisheries
Fishery Research Services. Retrieved 22 July 2009.
Deep water demersal fisheries
Joint Nature Conservation Committee. Retrieved 22 July 2009.

External links

Groundfish retention
{{DEFAULTSORT:Demersal Fish Aquatic ecology Marine biology Ichthyology Fishing industry