Additional Deep Sea Species

All of the species featured on this page are found in the deep sea areas around the British Isles. However, the species featured here are either rare, or relatively obscure and so do not have their own profiles. Scroll down to read through the species, or use the links below to jump to a fish species.

Bean’s BigscaleDeep-sea LizardfishRisso’s LanternfishCut-throat EelGreater ArgentineSlickhead SpeciesLeafscale Gulper SharkKnifetooth Dogfish.

Bean’s Bigscale

  • Scientific name: Scopelogadus beanii
  • Size: Up to 15cm in length
  • UK shore caught record: No record stands
  • IUCN Status
    • Global: DD (Data Deficient)
    • Europe: NE (Not Evaluated)
  • Distribution: Found on a worldwide basis in waters at least several hundred metres deep.
  • Feeds on: Small mid-water crustaceans and zooplankton.
  • Description: A small fish which has a large head, taking up between a quarter and a third of its overall length. The head is scaleless but may have marks present, while the rest of the body has is covered in large, loose scales. A single dorsal fin is present and the tail is small relative to the overall size of the fish. The colour is usually dark grey to black.

Bean’s bigscale is a deep-sea species of fish which is usually found at depths of several hundred metres down to over three thousand metres. It is found in the deep sea areas around the British Isles but has a global distribution, being found in the waters off North and South America, Australia and Africa. This species lives and feeds at a range of depths but is most common in mid-water, where it will feed on small crustaceans. Its small size means that it may also become prey itself for larger species.

Tarleton Hoffman Bean

Tarleton Hoffman Bean

Bean’s bigscale is of no interest to commercial fisheries, and any which are caught are likely to be discarded at sea as unwanted bycatch. The International Union for the Conservation of Nature (IUCN) classes Bean’s bigscale as a species of Least Concern in European waters, although there is not enough research to make an assessment of stock levels around the world, meaning it is classed as Data Deficient on a global basis. Bean’s bigscale are named after Tarleton Hoffman Bean (1846-1916), the American ichthyologist who has eight other species of fish and a genus of lanternfish named after him.

Deep-sea Lizardfish


  • Scientific name: Bathysaurus ferox
  • Also known as: Bathysaur
  • Size: Generally around 2ft in length when fully grown
  • ICUN Status
    • Global: LC (Least Concern)
    • Europe: LC (Least Concern)
  • Distribution: Found across most of the world in deep sea areas.
  • Feeds on: Thought to be a predator which will attack and eat small fish, squid and deep-water prawn species.
  • Description: Long, eel-like body which is can be brownish, silver or light grey in colour and covered in tough scales. Mouth is very large in relation to the overall size of the fish and is full of long, sharp teeth which may also be present on the tongue. Lower jaw protrudes slightly further than upper jaw.

There are over fifty species of lizardfish across the world and the vast majority of these live in shallow waters. However, the species of lizardfish which are found in UK and Irish waters are very deep sea creatures found at depths of several hundred metres to thousands of metres. For this reason they are poorly known to both anglers and the general public.


Deep-sea lizardfish are found in the deepest parts of the sea around the British Isles such as the Rockall Trough and Faroe-Shetland Channel. They are found throughout the North East Atlantic, although they are absent from areas such as the Baltic Sea, Black Sea and the Mediterranean. Their range extends across the Atlantic to the western coastline of the USA and Canada, and they are also found in the Southern Hemisphere off the coasts of South Africa, New Zealand, Australia and South America.


Deep-sea lizardfish are a poorly understood species, although the basic facts about how this species behaves are known. Despite their maximum size being only a few feet in length they are active predators, feeding on small fish, deep water crustaceans and squid. It is thought that deep-sea lizardfish wait on the seabed for smaller creatures to pass by and then launch themselves at their prey in an ambush attack. The sharp teeth of the deep-sea lizardfish are hinged backwards, meaning that prey cannot escape once it is in the mouth of the lizardfish. Despite this predatory nature it is also believed that they will scavenge on dead and rotting fish and other forms of animal matter which fall down to the seabed from surface.

Deep-sea lizardfish are synchronous hermaphrodites which means that they have both male and female sexual organs, although self-fertilisation is not thought to occur.

Second Species – Highfin Lizardfish

Highfin Lizardfish

A highfin lizardfish in its natural habitat on the seabed at the Davidson Seamount, 2375 metres below the surface.

There is a second species of lizardfish found in UK waters, the highfin lizardfish (Bathysaurus mollis). It is slightly larger than the deep-sea lizardfish, growing up to three feet in length. It is thought to prefer colder waters and may actually be present in greater numbers in British waters than the deep-sea lizardfish. Although it is also a poorly understood species its feeding, distribution and behaviour are thought to be very similar to the deep-sea lizardfish.

Commercial Value

While lizardfish may be caught by deep sea trawls and possibly by longlines they are have no commercial value at all and are likely to be discarded at sea if caught by commercial vessels. They are classed as a species of Least Concern by the International Union for the Conservation of Nature.

Risso’s Lanternfish

Risso's Lanternfish

  • Scientific name: Electrona risso
  • Also know as: Chubby Flashlight Fish, Electric Flashlight Fish
  • Size: Grows to around 8-9cm
  • IUCN status
    • Global: LC (Least Concern)
    • Europe: LC (Least Concern)
  • Distribution: Found worldwide in deep waters. Much of the European population is found around the Mediterranean with some populations found around the southern and western parts of the British Isles.
  • Feeds on: Tiny crustaceans and copepods.
  • Description: Large blunt head with upturned mouth and very large eyes. Body is short with small fins and small deeply forked tail. Light emitting photophores are located under the eyes and elsewhere on the body.

Risso’s lanternfish are a species of small deep-sea fish which are found in all of the seas and oceans of the world, with the exception of the polar and arctic regions. They generally live at a depth of at least 100 metres and can be found all of the way down to depths greater than 1000 metres.

Antoine Risso

Risso’s lanternfish are a small species, seldom exceeding 9cm in length. They shoal in huge numbers around sea mounts and other underwater features. They emit bio-luminescent light from photophores which are located under their eyes and along their lateral line. This light is thought to be used as a form of communication and allows Risso’s lanternfish to shoal together in great numbers, although it may also play a role in distracting and avoiding predators. Risso’s lanternfish make vertical migrations where they move upwards from their deep-sea habitat to mid-water during darkness. This may be done to pursue copepods and other tiny mid-water crustaceans which make up the vast majority of their diet, although their vertical migration may also be connected to avoiding predators which are more active at night. Although some species of lanternfish are caught commercially on a very small and specialised basis, Risso’s lanternfish are not targeted by commercial fisheries and have no value as a food fish. They are therefore classed as a species of Least Concern by the International Union for the Conservation of Nature (IUCN).

This species is named after Antoine Risso (1777 – 1845), the French naturalist who also has the Risso’s dolphin named after him.

Cut-throat Eel

Cut-throat Eel

  • Scientific name: Synaphobranchus kaupii
  • Also know as: Kaupt’s Arrowtooth Eel, Long-nosed Eel, Slatjaw Eel, Grey’s Cut-throat Eel
  • Size: Up to 3ft in length
  • IUCN status
    • Global: LC (Least Concern)
    • Europe: LC (Least Concern)
  • Distribution: Distributed worldwide. British populations concentrated in the Rockall Trough and Faroe-Shetland Channel.
  • Feeds on: Scavenger that will feed on dead fish and also eat any other bottom dwelling creatures it comes across such as deep-sea prawns and crustaceans.
  • Description: Elongated, typical eel-like body. Long snout with large, wide-opening mouth filled with sharp teeth. Dorsal fin starts half way back on body. Dark grey to dark purple in colour.

The cutthroat eel is a medium sized eel, growing to around one metre in length. They are found in very deep water across the world. They are classed as abundant in number across most of their range, mostly due to their lack of commercial value.


It is a deep sea species, which can be found all of the way down to depths of five thousand metres, although it has been known to live and feed at depths of around five hundred metres. It has a worldwide distribution being found throughout European waters with its range extending across the Atlantic to the coasts of Iceland and Greenland to the coasts of the USA and Canada. This species is also found all around the African continent, in Asian waters (particularly off the coast of Japan) and is also present in the Caribbean Sea and off the coast of South America.

Life Cycle and Feeding

The cutthroat eel is mostly a scavenger, scouring the seabed for pretty much anything it can find. They will eat all manner of bottom dwelling creatures such as deep-water prawns, crustaceans and dead and rotting fish, and may also hunt smaller fish and squid. Cutthroat eels may themselves become prey for larger species, such as deep-sea sharks.

Conservation Status

Cutthroat eels have no commercial value and are not targeted by fishing vessels. They may, however, be caught as bycatch where they will almost always be discarded at sea. Due to its widespread distribution and lack of commercial exploitation the IUCN (International Union for the Conservation of Nature) believe that the population of cutthroat eels is stable across the world (and abundant in European waters) and class this species as one of Least Concern.

Greater Argentine

Greater Argentine

  • Scientific name: Argentina silus
  • Also known as: Greater Silver Smelt
  • Size: Up to 2ft in length
  • IUCN status:
    • Global: NE (Not Evaluated)
    • Europe: LC (Least Concern)
  • Distribution: Found throughout the deep water Rockall Trough and Faroe-Shetland Channel, and throughout deep water areas in European and American waters.
  • Feeds on: Krill, plankton and tiny crustaceans, and will take small squid and fish when fully mature.
  • Description: Small, slim fish with streamlined body. Prominent first dorsal fin is high and distinctively shaped with second dorsal fin very small with no rays supporting it. Two anal fins present both set far back on the underside of the body. Tail is deeply forked. Eyes are very large. Colour silvery, sometimes with yellow/green tinge.

The greater argentine is a relatively small deep sea fish which lives at depths down to around 1500 metres, although it can also be found at just a few hundred metres of depth. They are found in the deep waters of northern Europe, with their range extending across the Atlantic to the waters of Canada and the USA. The greater argentine lives and feeds in large schools on the seabed, feeding on small marine crustaceans and prawns, although they will also take small fish and squid when fully grown. It is thought that the greater argentine cannot reproduce until it is around ten years old and may live for as long as thirty years.

Commercial Value

The greater argentine does have commercial value and is edible, and there is some demand for it as a food fish. However, a significant proportion of the greater argentines which are caught are used as fishmeal. The IUCN currently classes this species as one of Least Concern.

Slickhead Species

Slickheads are a family of fish which contains a large number of species across many genera. All are deep-water species and get their name due to the fact that they have no scales on their head or gill covers (they are also sometimes referred to as nakedheads or smooth-heads). The most common species in UK waters is Baird’s slickhead which is found in the deep waters around the Rockall Trough and the Faroe-Shetland Channel, and also has a distribution across the North Atlantic, meaning they are found in Icelandic, Greenlandic, American and Canadian waters. There are a number of other species of slickhead which are found in the waters around Britain and Ireland. These are similarly limited to very deep-water habitats.

Baird’s Slickhead

  • Scientific name: Alepocephalus bairdii
  • Size: Up to 3ft in length
  • IUCN status
    • Global: DD (Data Deficient)
    • Europe: DD (Data Deficient)
  • Description: Generally dark in colour with a silvery tint to the flanks. Body is covered in scales but scales are absent on the head and gill covers – hence the name of this species. There is a single dorsal fin set two thirds of the way along the body, and a tail fin clearly divided into two sections. Eyes are relatively large and a lateral line of darker scales runs the full length of the body.

Although Baird’s slickhead can be found at depths of several hundred metres they are generally found at over one thousand metres deep over sandy, muddy or other smooth seabeds. They tend to avoid rocky, heavy or broken ground. The life-cycle of this species is poorly understood but it is thought that they will feed on a range of species including jellyfish, comb jellies, deep-water shrimps and other invertebrates and will also take any small fish and squid they can catch. Little is known about their breeding patterns or spawning grounds.

Spencer Fullerton Baird

Spencer Fullerton Baird

Being a relatively small fish Baird’s slickhead is prey for other predatory species of fish (such as black scabbardfish and kitefin shark) even when fully grown. Baird’s slickhead are of very limited commercial value and have no mass appeal as a food fish, although they are eaten in coastal communities around the Mediterranean. They are often taken as bycatch in trawls for more commercially valuable deep water fish such as orange roughy or roundnose grenadier, and may occasionally be retained to be processed into fishmeal. This species of slickhead is known as Baird’s slickhead after Spencer Fullerton Baird (1823 – 1887), the American author and natural historian and who was the first curator of the Smithstonian Institution.

Other Slickheads in British Waters

Softskin Smooth-head

There are a number of other species of slickhead found in the waters around the British Isles. As stated they are most commonly found in very deep water areas, most commonly the Rockall Trough to the west of Ireland and the Faroe-Shetland Channel to the north of Scotland. These species include but are not limited to:

  • Softskin Smooth-head (Rouleina attrita) – pictured above.
  • Maderian Smooth-head (Rouleina maderensis)
  • Smallscale Smooth-head (Bathytroctes microlepis)
  • Agassiz’s Slickhead (Alepocephalus agassizii)

Most of these species have broadly similar feeding habits and a similar life cycle to Baird’s slickhead.

Leafscale Gulper Shark

Leafscale Gulper Shark

  • Scientific name: Centrophorus squamosus
  • Also know as: Deepsea Spiny Dogfish, Nilson’s Deepsea
  • Size: Up to 5ft in length
  • IUCN status
    • Global: VU (Vulnerable)
    • Europe: EN (Endangered)
  • Distribution: Found in the deep waters of Europe, Africa and Asia. UK populations restricted to the Rockall Trough and Faroe-Shetland Channel.
  • Feeds on: Fish and squid.
  • Description: Typical shark bodyshape. Two dorsal fins are present, both of which have a noticeable spine at their leading edge, pectoral fins are flat edged and there is no anal fin. Eyes are very large and green in colour, multiple gill slits are present and mouth is full of sharp teeth. Skin is very rough and made up of Y-shaped denticles which look like leaves, hence the name. Colour is usually dark grey to brown.

The leafscale gulper shark is a medium sized member of the shark family, growing up to around five feet in length. It is a deepwater species, generally found between depths of 1000 to 3000 metres, although occasionally it will be found at depths of just a few hundred metres. The leafscale gulper shark is a predator and hunts smaller fish and squid, although its feeding habits are poorly understood.


Distibution of the Leafscale Gulper Shark

Worldwide distibution of the leafscale gulper shark.

It is found throughout the world in limited numbers. The UK population is centred around the Rockall Trough and Faroe-Shetland Channel, as these are the only places deep enough to provide the appropriate habitat for this species. However, they are also populations throughout the north east Atlantic, off the western and southern coasts of Africa, and around Australia and New Zealand and off the coasts of China and Japan.

Commercial Value and Conservation Status

The leafscale gulper shark is targeted by deep sea commercial fisheries which use both deepwater trawls and long-lines to catch this species. There is a limited market for its flesh which is salted and sold for human consumption, the fins are made into (low value) shark fin soup and the liver is also eaten. The carcasses of leafscale gulper sharks may also be sent to fish processing plants to be made into fishmeal. Due to the commercial fishing pressure on this species its numbers have declined in recent years with ICES (Intenational Council for the Exploration of the Sea) stating that in some areas the numbers of leafscale gulper shark have been reduced by 80-90% in just three years. The IUCN (International Union for the Conservation of Nature) currently classify the leafscale gulper shark as Vulnerable with a declining population trend. Like most shark species the leafscale gulper shark does not become sexually mature until a later stage of its life, meaning that numbers will take a very long time to increase even if the commercial fishing pressure on this species reduces.

Knifetooth Dogfish

Knifetooth Dogfish

  • Scientific name: Scymnodon ringens
  • Size: Grows to around 3ft in length
  • ICUN Status
    • Global: DD (Data Deficient)
    • Europe: LC (Least Concern)
  • Distribution: Found in very deep water around the British Isles with its range extending throughout the North Atlantic.
  • Feeds on: Unknown.
  • Description: Thick and stout body with short snout. Mouth is full of sharp and distinctive teeth which give this species its name. Body is generally dark grey to blackish with large greenish eyes.

The knifetooth dogfish is a deep water species of shark. It is found predominantly in European waters. It is a species which is little understood by scientists and marine biologists.


The Knifetooth dogfish is found in the waters around Europe and northern Africa.

The knifetooth dogfish is found predominantly in European waters. Although it can be found in deep water all around the British Isles its main distribution is around the Rockall Trough to the west of Ireland and the Faroe-Shetland Channel off the northern coast of Scotland. Its range extends northwards along the Atlantic coasts of Spain and France and along the coast of Portugal, although it is not found in the Mediterranean. Its range extends along the western coast of the African continent as far as Senegal.

Life Cycle and Feeding

Knifetooth dogfish are thought to live at depths of at least several hundred metres, and can be found down to depths of over 2000 metres. As the knifetooth dogfish is so poorly studied it is not entirely clear what it feeds on. It is theorised that its sharp teeth are used to scavenge on the bodies of large sea creatures such as sharks and whales which fall to the seabed, but it is also believed that knifetooth dogfish hunt smaller fish and squid in some way. Little is known about the spawning and reproduction of this species.

Conservation Status

This species is of minimal commercial value. In the vast majority of cases any knifetooth dogfish caught by deep-sea trawlers will be discarded at sea as bycatch. However, in a small number of cases this species may be retained and processed into fishmeal. There is very little information available on the numbers of this species but – like most deep-sea species – knifetooth dogfish are slow-growing and late-maturing, meaning that they are vulnerable to their numbers being depleted. The International Union for the Conservation of Nature does not currently have enough information to assess the conservation status of this species, meaning it is classed as Data Deficient.

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