Sloane’s Viperfish

  • Scientific name: Chauliodus sloani
  • Also know as: Sloane’s Fangfish, Dannevig’s Dragonfish, Needletooth Fish
  • Size: Up to 20cm in length
  • UK minimum size: N/a
  • UK shore caught record: N/a
  • Distribution: Found on a worldwide basis in waters at least several hundred metres deep.
  • Feeds on: Small and immature fish
  • Description: A small fish which has a large head and fang-like teeth which are very large relative to its body length. Long eel-like tapering body with a hugely extended ray fist ray in the dorsal fin and a small forked tail. Bioluminescent scales are present along the blue-silver body.

Sloane’s viperfish is a little understood species of viperfish in the Stomiidae family. It is generally found at depth of several thousand metres. Due to its deep-sea habitat and the fact it is of next to no commercial value it has been poorly studied by the scientific community.

Distribution and Habitat

This species is classed as a deep sea fish, being found at depths of several thousand metres. However, there is evidence that Sloane’s viperfish may make vertical migrations to within several hundred metres of the surface during darkness in search of prey. They have a wide distribution, being found across the temperate and sub-tropical seas and oceans of the world. In terms of their distribution around the British Isles they are found in the deep areas of the Atlantic, but appear to be absent from the relatively shallow waters of the North Sea.

Feeding and Behaviour

Sloane’s viperfish teeth

Little research has been carried out into the feeding habits of Sloane’s viperfish. They are believed to be predators which use their sharp, fanglike teeth to prey on smaller fish. They can extend their mouths open extremely wide to take in fish around two-thirds of their own body length as prey. The teeth are so large relative to the body size that the mouth of this species cannot fully close. Indeed, Sloane’s viperfish competes with the common fangtooth to have the record as the species with the largest teeth relative to body size. Sloane’s viperfish are thought to use the massively extended bioluminescent front ray of their dorsal fin as a lure to attract smaller prey fish close to them in a manner similar to that of an anglerfish, although due to the difficulties of seeing this species feed in the wild this has never been confirmed.

The vertical migrations that Sloane’s viperfish make into shallower water may be linked to moving into areas where small prey fish are more common. Due to their small size Sloane’s viperfish themselves become prey for larger predators such as deep water sharks, eels and fish such as orange roughy. Practically nothing is known about how Sloane’s viperfish reproduce, but they may use their bioluminescence to communicate with and attract other viperfish during the spawning times. They are calculated to have a lifespan of twenty to thirty years. There are nine other species of viperfish in the Chauliodus genus, but only Sloane’s viperfish is found in British waters in any number

Species Name

Sir Hans Sloane

Sloane’s viperfish are named after Sir Hans Sloane (1660 – 1753). He was an Anglo-Irish naturalist and medical doctor who left his vast collection of preserved animals, human and animal skeletons, books, manuscripts and illustrations to the nation on his death. This collection formed the basis of the British Museum and also part of the British Library. Several other species of plants and animals are also named after Sir Hans Sloane, as is Sloane Square in London.

Commercial Value

Sloane’s viperfish have no commercial value and commercial fishing vessels do not actively target this species. Any Sloane’s viperfish which are inadvertently caught by trawlers are likely to be discarded as worthless bycatch. However, bycatch levels are not believed to be a threat to this species and their wide distribution and lack of commercial value mean that the IUCN (International Union for the Conservation of Nature) class Sloane’s viperfish as a species of Least Concern.

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