Additional Rare and Unusual Fish

This page features profiles of some of the species of rare and unusual fish which are not found regularly enough around the UK to have their own profile, but can be found in British waters from time to time. Scroll down to read through the different species, or click on the links below to jump to a section.

Mediterranean ScaldfishRudderfishCornish BlackfishBogueBlue RunnerLong Rough Dab

Mediterranean Scaldfish

Mediterranean Scaldfish

  • Scientific name: Arnoglossus laterna
  • Size: Up to 30cm
  • UK shore caught record: N/a
  • IUCN Status:
    • Global: LC (Least Concern)
    • Europe: LC (Least Concern)
  • Distribution: Found throughout European waters.
  • Feeds on: Marine invertebrates and other small creatures.
  • Description: A thin bodied flatfish which has an elongated oval body shape. Colour is usually light brown but can appear transparent, especially after the fish has been out of the water for some time. Some specimens may have darker patches or blotches on the body. Dorsal fin is longer than the anal fin and the lateral line has a distinctive curve to it.

The Mediterranean scaldfish is a small species of flatfish. Despite having a surprisingly wide distribution it remains an obscure species and is seldom caught on rod and line. As of 2015 there is no shore caught UK record for this species.

Distribution

As its name suggests the Mediterranean scaldfish can be found in the warmer waters of the Mediterranean Sea and surrounding waters. However, its range extends from the colder waters of the Norwegian Sea all of the way along the coasts of the African continent. In UK waters it is predominantly found along the southern and western coasts of the British Isles, but can turn up along the east coast of England and Scotland in smaller numbers.

Description, Size and Behaviour

The Mediterranean scaldfish is a small species, growing to a maximum of 30cm, with the average size being between 10cm and 20cm. They mostly prefer sandy, muddy or shingle seabeds, although they can be found across mixed ground and only avoid heavy and rocky ground. While they will happily live at depths of several hundred metres they will also come into relatively shallow water of ten or fifteen metres, making it something of a mystery why this species has not been reported caught on rod and line and no British shore caught or boat caught record stands. Perhaps the rising popularity of LRF (Light Rock Fishing) will see this species begin to turn up in angler’s catches. Mediterranean scaldfish feed on small invertebrates, marine worms and any other small creatures which they come across on the seabed. They may also feed on very small fish species and the fry of larger species.

Commercial Value

Mediterranean scaldfish are edible, but have only a limited commercial value, probably due to their small size and the limited amount of edible flesh they provide. Only small-scale artisan fishermen target this species, and it is available from fish markets and fish mongers in southern European countries. Larger scale fishing vessels are likely to discard any Mediterranean scaldfish they catch as unwanted bycatch. However, in some cases this species may be retained for non-human consumption, such as being turned into fishmeal.

Other Species of Scaldfish

The imperial scaldfish (Arnoglossus imperialis) is a species of scaldfish which is found in the north east Atlantic and parts of the Mediterranean. Although rare in British waters it can be found along the western coast of Scotland, Ireland and parts of Wales and the English Channel. It grows to the same size as the Mediterranean scaldfish, and the main method of distinguishing the species apart are the very unusual elongated rays which protrude from the dorsal fin near to the head of the imperial scaldfish. This species has no commercial value, although it is caught as bycatch by trawlers. The IUCN (International Union for the Conservation of Nature) class it as a species of Least Concern.

Thor's Scaldfish

Although less common, Thor’s Scaldfish is also found in British waters.

Another species Thor’s Scaldfish (Arnoglossus thori) is much less common but has been reported from the west coast of Ireland. This species also has the elongated dorsal fin rays, although they are fewer in number than those found in the imperial scaldfish. Thor’s scaldfish is also the smallest of the three species, rarely growing over 18cm.

Rudderfish

Rudderfish

  • Scientific name: Centrolophus niger
  • Also know as: Medusafish, Blackfish, Black Ruff
  • Size: Grows to a maximum of around 3ft in length.
  • UK shore caught record: 5lb 14oz
  • IUCN Status
    • Global: LC (Least Concern)
    • Europe: LC (Least Concern)
  • Distribution: Found worldwide in both warm and temperate seas.
  • Feeds on: Opportunistic feeder eat prawns, small fish and squid.
  • Description: Blunt snout with large, high head and relatively small mouth. High oval body with long single dorsal fin which runs for two thirds of the body length and anal fin is around one third of body length. Colour usually dark grey to black, sometimes with a bluish or brownish tinge.

The rudderfish is a rare fish in UK waters. It is found predominantly in the Pacific, Atlantic and Mediterranean but is found in the waters of the British Isles with the places most likely to hold this species being to the west of Ireland, off the south-west coast of England and in the English Channel, and although specimens turn up elsewhere around the British Isles. Although immature rudderfish may be found in shallower water the fully grown rudderfish is a deeper water fish which lives and feeds in waters of around 100 to 200 metres deep all of the way down to over 1000 metres. This means that the rudderfish is a very rare catch indeed for shore anglers. This species is related to the similarly rare Cornish blackfish, as both species are in the Medusafish family.

The life cycle and feeding habits of rudderfish have not been well studied by science. It is thought that they can grow to at least three feet in length, possibly larger, and they feed opportunistically on small fish, squid, shrimps and prawns, although some accounts state that they can feed on some forms of plankton as well. Rudderfish are thought to feed higher up in the water column but may also scavenge on the seabed.

Despite its rarity this species does have a British shore caught record with S. Ostler catching a 5lb 14oz specimen from Aldbrough Beach, East Yorkshire in 1998. The boat caught record – a rudderfish of 3lb 10oz – was caught in Scottish waters in 1972.

Commercial Value

The rudderfish has limited commercial value. It is not targeted directly by commercial fisheries but may be retained when it is inadvertently caught in trawls. The largest market for this species is in Europe with Spain and Portugal being the main consumers of this species. When supplied for human consumption it is often marketed under the name black ruff or black ruff-fish.

Cornish Blackfish

Cornish Blackfish

  • Scientific name: Schedophilus medusophagus
  • Also know as: Portrush Barrelfish
  • Size: Up to 3ft in length (but usually smaller than this).
  • UK shore caught record: 8oz 4dr
  • IUCN Status:
    • Global: NE (Not Evaluated)
    • Europe: LC (Least Concern)
  • Distribution: Found to the south west of England and Ireland. Distribution also extends across the Atlantic to American and Canadian waters and is also present in the warmer waters around Europe.
  • Feeds on: Thought to feed on jellyfish and small sea creatures.
  • Description: Elongated oval body with long dorsal fin which runs along the full length of the back. Anal fin is also long, approximately one third to half of the body length. Eyes are relatively large and located close to the snout, and lateral line curves upwards towards the gills. Colour usually black to brown, sometimes with mottled pattern.

The Cornish blackfish is a little understood and very rare species (in British waters) which, as its name suggests, is most commonly found to the south west of Britain and although populations may also be present in the English Channel. Smaller, immature Cornish blackfish may come into shallow waters but this is a deeper water fish once fully grown and is usually found at depths of around 300 to 1000 metres. The feeding habits of the Cornish blackfish are poorly understood, although it is confirmed that they consume jellyfish and similar creatures such as comb jellies, and may also take small crustaceans and invertebrates from the seabed. Practically nothing is known about the spawning or reproductive cycle of the this species.

Name and Species Confusion

The Cornish blackfish is so called as the first verified specimen came from the Cornish coast in 1859 and was given the scientific name Centrolophus Brittanicus. However, in 1878 an immature specimen was caught from the Northern Irish coast at Portrush. As juvenile Cornish blackfish look different to mature specimens this fish was mis-identified as a newly discovered species and was given the scientific name of Lirus medusophagus. The belief that these were two different species persisted into the Twentieth Century when it was eventually established that they were actually one species and were brought together under the scientific name of Schedophilus medusophagus.

The rudderfish Centrolophus niger (see above) is also sometimes referred to as blackfish. This species is also very rare in the waters around the British Isles and is a separate species to the Cornish blackfish.

Commercial Value and Scientific Interest

Cornish blackfish are occasionally caught in deep trawl nets which are targeting other species. As they have little commercial value and are classed as bycatch and are usually discarded back into the sea. Cornish blackfish are a rare catch indeed from either shore or boat. There is, however, a UK shore caught record for this species with a specimen of 8 ounces and 4 drams caught by Mr. R. Cooke on Cefn Sidan Beach, Carmarthenshire, Wales in 1983.

Bogue

Bogue

  • Scientific name: Boops boops
  • Also known as: Bream
  • Size: Up to 30cm and 2lbs
  • UK shore caught record: 1lb 15oz
  • IUCN status
    • Global: LC (Least Concern)
    • Europe: LC (Least Concern)
  • Distribution: Common throughout the warmer waters of the Mediterranean and North Africa. At the edges of its distribution in British and Irish waters, but does turn up around the south coasts of Ireland, England and Wales in the summer months.
  • Feeds on: Small crustaceans, prawns and shrimps, and can also feed on marine plants and seaweed, and have the ability to filter feed.
  • Description: Small, slender fish. Eyes are relatively large and located close to snout. A single dorsal fin is present and tail is deeply forked. Upper flanks are dark grey while rest of body is silvery. A number of dark golden stripes run along the length of the body.

The bogue is a small fish species that is found mostly throughout the warmer waters of Europe, especially the Mediterranean Sea, the Black Sea and in the warmer waters of the North East Atlantic. This species will live in shallow, inshore waters, but can also be found down in deeper waters of several hundred metres. They will feed on the seabed where they eat prawns, shrimps, marine worms and small crustaceans, and will also move up to mid-water to feed on the small mid-water crustaceans found there, and during darkness they may even come to the surface. Bogue will also eat plant matter such as seaweed and have a limited ability to filter feed on plankton through their gill rakers.

Bogue on sale

Bogue on sale at a fishmongers in Turkey.

Bogue are of commercial importance with Mediterranean countries such as Spain and Greece accounting for the majority of commercial catches of this species. The FAO (Food and Agriculture Organisation of the United Nations) stating that around 35,000 tons of this species are caught in total every year, mostly by trawling or purse seining. The flesh is of good quality for human consumption but British fishermen catching this species may discard catches at sea due to the lack of demand for this species in the UK. Bogue can also be used as a source of fish oil or fishmeal, or as live bait for commercial long lines which target tuna. Despite the relatively high levels of commercial exploitation bogue  is classed as a species of Least Concern with a stable population in both European waters and on a global basis.

Shoal of bogue

A shoal of bogue near the surface.

Despite being a rare fish there is a shore caught record for this species set in 1978 by S.G. Torode who caught a bogue weighing 1lb 15oz while fishing in Guernsey, Channel Islands. The boat caught record is a fish of 1lb 13oz caught by K. McBride off Eddystone Reef off the coast of South West England in 1981.

Blue Runner

Blue Runner

    • Scientific name: Caranx crysos
    • Also know as: Hardtail, Hardtailed Jack, Hardnose, Bluestripe, Blue Jack, Green Jack, Blue Mackerel, Egyptian Scad, Cavalli, Yellowtail Cavalli, Yellow Mackerel
    • Size: Up to 3ft and 10lbs, although typically around 1ft and 2lbs
    • UK shore caught record: 2lb 8oz
    • IUCN status
      • Global: LC (Least Concern)
      • Europe: LC (Least Concern)
    • Distribution: A species widespread throughout tropical and temperate waters, however the range of this species appears to be extending northwards and sporadic observations of this species have been made off the south west coast of Britain.
    • Feeds on: Small predator which feeds by hunting small fish. Occasionally other food sources such as crabs and prawns.
    • Description: Small, fast swimming fish which is similar in profile to a tuna. First dorsal fin is triangular and small, while second dorsal fin is long and runs down to the tailfin. Anal fin is similar in size. Pectoral fin is long while pelvic fins are short. Tail is long and deeply forked. Mouth has small, sharp teeth and eyes are large. Colour is usually bluish to green, fading to pale, sometimes silver on the underside. Black mark is often present on the gills and points of tail are also sometimes tipped with black.

The blue runner is a fast, swimming predatory fish which is abundant throughout many temperate and tropical waters throughout the world. Once considered absent from UK waters this species does appear to be extending its distribution northwards and is being observed off the south west coast of England, possibly as a result of warming sea temperatures caused by global warming.

Distribution

Blue Runner Distribution

Worldwide distribution of the blue runner.

In European waters the blue runner is found throughout the Mediterranean and off the coasts of Portugal, France and Spain. It is also found off the eastern coast North America, through the Caribbean Sea and the Gulf of Mexico and along the eastern coastline of South America.

Life Cycle and Feeding

The blue runner is a shoaling fish which behaves in a similar manner to small tuna species (such as skipjack). Large numbers of blue runner will join together to feed on any small preyfish they can hunt down. They are generally seen as a pelagic fish and do most of their hunting in mid-water on smaller fish, which means in British waters they will be most likely to feed on mackerel, herring and sandeels. However, they will occasionally feed on the seabed if food, such as prawns, is abundant there. Blue runner are not a deep water species and are generally found in water less than one hundred metres deep. Blue runner are known to be attracted to both natural reefs and man-made structures such as oil platforms artificial reefs, and will often be found shoaling around these structures.

Blue Runner under undersea platform

Blue Runner under shoaling underneath an oil platform in the Gulf of Mexico.

Blue runner spawn at any time of the year, with females releasing eggs which hatch into small plankton-feeding larva. Once fully formed the small fish will live in shallower water, moving into slightly deeper water once they reach around 20-30cm in length.

Commercial and Recreational Use

Blue runner caught off Florida

Blue runner caught by recreational anglers off the coast of Florida

The blue runner is edible and in some parts of the world this species makes up the main catch of small-scale fisheries, creating a source of both food and employment. Commercially the blue runner is caught in a variety of methods such as purse seining, trawling, gill nets and on long lines. The blue runner is thought to be abundant and is classed under the category of Least Concern by the IUCN (International Union for the Conservation of Nature) in both European waters and gobally. In recreational fishing terms the blue runner is seen as an excellent sportfish due to its fast swimming nature and powerful runs, especially when using light tackle. They are usually caught on artificial lures such as jigs and spinners. Due to the great fighting qualities of the blue runner many UK based anglers will be happy to see this species becoming more common around the British Isles and would welcome the opportunity to catch this species. The UK shore caught record was previously a fish of 1lb 4oz, but is now stated as being a specimen of 2lb 8oz, caught by Nick Rodgers off the the Cornish coast.

Long Rough Dab

Long Rough Dab
  • Scientific name: Hippoglossoides platessoides
  • Also known as: American Plaice, American Sole, Rough Dab
  • Size: Up to 50cm in length. Typically half this size.
  • UK shore caught record: 5oz 8dr
  • IUCN Status
    • Global: NE (Not Evaluated)
    • Europe: LC (Least Concern)
  • Distribution: Found throughout the North East Atlantic with separate populations in European waters and off the eastern coast of North America.
  • Feeds on: Marine worms, invertebrates and small crustaceans and small fish.
  • Description: Oval and somewhat elongated body. Eyes on right with dorsal fin starting level with eye. Colour usually brown with black/dark spots. Skin is rough to the touch. Mouth relatively large. Lateral line is nearly straight with only a slight curve towards the gills.
American Plaice

Close up of a long rough dab.

Long rough dab are often classed as a mini-species as the ones caught in UK waters are small – the shore caught record is just over five ounces. However, this species can in fact grow to over 50cm in length, although specimens of this size are rare as they are usually caught long before they can reach these sizes. They are caught much more often from the coast of countries such as Iceland and Scandinavian countries and, as an edible species, are a highly important commercial fish in the United States of America and in Canada. However, this species has a relatively low profile in the British Isles and is mostly unknown to both UK anglers and consumers.

Distribution and Species Differences

Long rough dab are a species which is endemic to the North Atlantic. They prefer cooler waters and on the European side of their distribution they are found throughout the Norwegian Sea, Baltic Sea and North Sea, as well as around the coast of Iceland and Greenland. They are found in the English Channel but are absent from the coastline of Spain, Portugal and the Mediterranean Sea. Their range continues across the Atlantic and they are found off the coast of Nova Scotia and down to Massachusetts.

There is evidence that the species found in North America and Europe are genetically different, with some scientific literature classing them as distinct subspecies. More research is needed in this area to establish the taxonomic status of this species.

Habitat, Feeding and Reproduction

Long rough dab live over clean muddy and sandy bottoms in water as shallow as ten metres, but are usually found in water much deeper than this, sometimes down as deep as four hundred metres. Long rough dab generally feed on marine worms, invertebrates, brittle stars and molluscs. As they get older and bigger they add fish to this and hunt for sprats, sandeels and capelin. When living in warmer climates towards the American edge of their range long rough dab are thought to be able to reproduce are three years old and around 30cm in length. However, in colder Scandinavian waters around Europe they may need reach an older age (possibly as old as seven or eight years) and a larger size before reproduction can happen. Spawning generally takes place in the spring months.

Commercial Value

Long rough dab are a commercially important species and are caught by trawling or static nets. On the North American side of the Atlantic this species was heavily overfished in from the late 1960s until well into the 1990s, severely deleting stocks – a situation made worse by disagreements and political wrangling: the USA’s Northwest Atlantic Fisheries Organization has considered this species to be subject to overfishing stated that stocks were in serious trouble, whereas the Canadian government believed this species was abundant continued to fish for it at a high intensity.

Commercial catches of long rough dab

However, it is now accepted that all stocks of long rough dab are depleted and a number of moratoriums and bycatch reduction schemes are in place throughout North American waters in an attempt to allow a stock recovery to take place. In Europe long rough dab are not as commercially valuable and fished for at a much lower intensity. The International Union for the Conservation of Nature classes them as a specie of Least Concern in the European assessment area.

Seafish – the taxpayer funded quango which represents the UK commercial fishing industry – states that long rough dab are a separate species to European plaice (Pleuronectes platessa) and should not be marketed under the plaice name in the United Kingdom.

Share this page: