Latin name

Etmopterus spinax

Other names

Velvet belly, Peshkaqeni barkzi (Albanian), Noshchna akula (Bulgarian), Donkerbuiklantaarnhaai (Dutch), Μαυροαγκαθίτης (Mavroangathitis) (Greek), Negrito (Spanish), Sagri' nero, Moretto (Italian), Kleiner Schwarzer Dornhai (German), Kolczak czarny (Polish), Lixinha da fundura (Portuguese), Kostelj crnac (Serbian, Croatian), Črni svetilec (Slovenian), Mahmuzluköpek balığı (Turkish), Sagre commun (French), Žralok černý (Czech).

Identification

It is a dense-bodied fish with a moderately elongated, broad, flattened snout. The mouth is surrounded by thin, smooth lips. The upper teeth are small, with a narrow central tooth and usually no more than three pairs of lateral teeth. The lower teeth are much larger, with sharply bevelled teeth like knife blades at the top, and with interlocking bases. The shark has five pairs of very small gill slits, comparable in size to splash gills. Both dorsal fins have thick, grooved spines at the front, with the posterior spine being longer and more curved. 

This shark's liver has specialised proteins that can neutralise cadmium, copper, mercury, zinc and other toxic substances. 

Features of fish fins

The first dorsal fin begins behind the short and rounded pectoral fins; the second dorsal fin is twice the size of the first and begins behind the pelvic fins. There is no anal fin. The slender tail merges into a long caudal fin with a small lower lobe and a low upper lobe with a protruding tooth on the underside of the tip.

Fish colouring

Dermal denticles thin, with curved tips, clearly separated from each other, not forming a distinct pattern on the skin. The colouration of the dorsal surface of the body is brown, which changes sharply to black on the ventral surface. There are black spots above and behind the pelvic fins and along the caudal fin. 

The body of these fish is covered with many photophores, which emit a blue-green light visible from 3-4 metres. The photophores are grouped along the sides and on the abdomen in eight patches of varying density, forming a characteristic pattern. Photophores are present along the lateral line, scattered under the head excluding the mouth area, dotted on the abdomen and particularly densely concentrated around the pectoral fins and under the tail peduncle.

Distribution

The range of the Velvet Belly in the eastern Atlantic extends from Iceland and Norway to Gabon, including the Mediterranean, the Azores, the Canary Islands and Cape Verde. There are reports of their capture in the waters of Cape Province, South Africa. 

Habitat

This shark mainly inhabits the upper mud and clay slopes of the outer and island continental shelves, from the bottom to the middle of the water column. This species is found at depths ranging from 70 to 2,490 metres. They are most commonly found between 200 and 500 metres.

Size

The largest specimen caught has reached 60 centimetres, but sharks over 45 centimetres are rare. Females tend to be larger than males. The maximum recorded weight is 850g.

Behavior

The Velvet belly is one of the most common deepwater sharks in the North East Atlantic. They are found both individually and in small schools. 

It is thought that bioluminescence acts as a backlight, blurring the shark's silhouette and making it invisible to upward looking predators. In addition, bioluminescence, which is species-specific, may also have a social function, such as coordinating group behaviour or finding a sexual partner. 

Food and feeding habits

Velvet belly is an important food item for larger fish. Dipturus oxyrinchus is thought to be the main predator.

As a predator, the shark feeds on crustaceans (e.g. shrimps), cephalopods (e.g. squid, cuttlefish) and bony fishes (Sternoptychidae, Paralepididae, Myctophidae, small cod). In Italian coastal waters, night sharks eat small quantities of roundworms and polychaete worms and prey on other cartilaginous fish. Studies of night sharks off Norway and Portugal, as well as in the Rockall Inlet, have shown that small sharks up to 27 centimetres in length feed mainly on krill of the species Meganyctiphanes norvegica and small fish Maurolicus muelleri. As they grow, their diet becomes more diverse, with squid and prawns of the species Pasiphaea tarda becoming the mainstay, and other fish species appearing in addition to M. muelleri.

Reproduction

An oviparous fish in which the embryos, supplied with a yolk sac, develop in the uterus. The reproductive cycle can last 2-3 years, ovulation occurs in early spring, fertilisation occurs in summer (possibly in winter if females have the ability to retain sperm), and offspring are born in late winter or early spring. Pregnancy lasts approximately one year. Litter sizes range from 6-20, increasing with the weight of the female. The size of the newborn is 12-14 centimetres. 

Night sharks acquire the ability to luminesce before birth; the yolk sac begins to fluoresce even before photophores are formed, probably due to the transfer of luminescent substances from mother to offspring. The first luminescent tissues appear when the embryos reach 55 millimetres, and fully luminescent areas are formed by the time the embryos grow to 95 millimetres. By the time the young sharks are born, 80 per cent of their abdominal surface is luminescent.

Sharks grow slowly, although slightly faster than some other deep-sea sharks such as Centrophorus squamosus or Squalus mitsukurii. Males become sexually mature at a size of 28-33 centimetres and females at 34-36 centimetres. The average age of maturity is 4 years for males and 4.7 years for females, although mature four-year-old individuals of both sexes and immature eight-year-old females have been observed. The probable life span of sharks of this species is estimated to be 18 years for males and 22 years for females. Specimens aged 8 and 11 years have been captured.

Fishing

Caught as bycatch in bottom trawl fisheries for shrimps and lobsters and in deep-sea longline fisheries for other fish. No commercial value.

Relationship with a person

No cases of human attacks have been reported.