The small-spotted catshark (''Scyliorhinus canicula''), also known as the sandy dogfish, lesser-spotted dogfish, rough-hound or morgay (in Scotland and Cornwall), is a catshark of the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Scyliorhinidae Scyliorhinidae is a Family (biology), family of sharks, one of a few families whose members share the common name catsharks, belonging to the Order (biology), order Carcharhiniformes, the ground sharks. Although they are generally known as cats ...

. It is found on the

continental shelves A continental shelf is a portion of a continent that is submerged under an area of relatively shallow water, known as a shelf sea. Much of these shelves were exposed by drops in sea level during glacial periods. The shelf surrounding an island ...

and the uppermost continental slopes off the coasts of

Norway Norway, officially the Kingdom of Norway, is a Nordic countries, Nordic country located on the Scandinavian Peninsula in Northern Europe. The remote Arctic island of Jan Mayen and the archipelago of Svalbard also form part of the Kingdom of ...

and the

British Isles The British Isles are an archipelago in the Atlantic Ocean, North Atlantic Ocean off the north-western coast of continental Europe, consisting of the islands of Great Britain, Ireland, the Isle of Man, the Inner Hebrides, Inner and Outer Hebr ...

south to

Senegal Senegal, officially the Republic of Senegal, is the westernmost country in West Africa, situated on the Atlantic Ocean coastline. It borders Mauritania to Mauritania–Senegal border, the north, Mali to Mali–Senegal border, the east, Guinea t ...

and in the

Mediterranean The Mediterranean Sea ( ) is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean basin and almost completely enclosed by land: on the east by the Levant in West Asia, on the north by Anatolia in West Asia and Southern ...

, between latitudes 63° N and 12° N. It can grow up to a length of , and it can weigh more than . It is found primarily over sandy, gravelly, or muddy bottoms from depths of a few metres down to .Rodriguez-Cabello, C., Sanchez, F., Olaso, I. 2007. Distribution patterns and sexual segregations of ''Scyliorhinus canicula'' (L.) in the Cantabrian Sea. ''Journal of Fish Biology''. 70: 1568–1586 ''S. canicula'' is one of the most abundant

elasmobranch Elasmobranchii () is a subclass of Chondrichthyes or cartilaginous fish, including modern sharks ( division Selachii), and batomorphs (division Batomorphi, including rays, skates, and sawfish). Members of this subclass are characterised by h ...

s in the northeast Atlantic and Mediterranean Sea. The majority of the populations are stable in most areas.Ballard, W., Mellinger, J., Lechenault, H. 2005. A series of normal stages for development of ''Scyliorhinus canicula'' the lesser spotted dogfish ''(Chondrichthyes: Scyliorhinidae)''. ''Journal of Experimental Zoology''. 267: 318–336

Description

''S. canicula'' are small, shallow-water sharks with a slender body and a blunt head. The two dorsal fins are located towards the tail end of the body. The texture of their skin is rough, similar to the coarseness of sandpaper. The nostrils are located on the underside of the snout and are connected to the mouth by a curved groove. The upper side of the body is greyish brown with dark brown spots. The underside is a light greyish white. The teeth of ''S. canicula'' are larger in males than in females; in addition, male ''S. canicula'' from West African waters have stronger, larger, and more calcinated jaws. The differences in mouth dimensions and tooth length between males and females, and between immature and adult males, could be due to different feeding habits or adaptations for reproductive behaviour.

Reproduction

''S. canicula'' is

oviparous Oviparous animals are animals that reproduce by depositing fertilized zygotes outside the body (i.e., by laying or spawning) in metabolically independent incubation organs known as eggs, which nurture the embryo into moving offsprings kno ...

. They deposit egg cases protected by a horny capsule with long tendrils. Egg cases are mostly deposited on macroalgae in shallow coastal waters. When the egg cases are deposited farther from shore, they are placed on sessile erect invertebrates. Egg cases usually measure 4 cm by 2 cm, without ever exceeding .Ellis, J.R., Shackley, S.E. 1997. The reproductive biology of ''Scyliorhinus canicula'' in the Bristol Channel, U.K.'' Journal of Fish Biology'', 51: 361–372 These egg cases can be found around the coasts of Europe. The embryos develop for 5–11 months depending on the sea temperature, and the young are born with a measurement of .

Spawning Spawn is the Egg cell, eggs and Spermatozoa, sperm released or deposited into water by aquatic animals. As a verb, ''to spawn'' refers to the process of freely releasing eggs and sperm into a body of water (fresh or marine); the physical act is ...

can take place almost year round. However, there can be seasonal patterns in spawning activity as well. For example, ''S. canicula'' females located off the Mediterranean coast of France lay their eggs from March to June and in December. In the waters surrounding Great Britain, egg laying occurs in spring with a gap between August and October. On the Tunisian coast, the sharks lay their eggs starting in spring, peaking in the summer and then slightly decreasing during autumn. Males reach sexual maturity with a length of about . Females reach sexual maturity with a length of .

Feeding

''S. canicula'' is an

opportunistic 300px, ''Opportunity Seized, Opportunity Missed'', engraving by Theodoor Galle, 1605 Opportunism is the practice of taking advantage of circumstances — with little regard for principles or with what the consequences are for others. Opport ...

species, preying on a wide variety of organisms. Decapod crustaceans, molluscs and fishes are their main prey, but

echinoderm An echinoderm () is any animal of the phylum Echinodermata (), which includes starfish, brittle stars, sea urchins, sand dollars and sea cucumbers, as well as the sessile sea lilies or "stone lilies". While bilaterally symmetrical as ...

polychaete Polychaeta () is a paraphyletic class of generally marine Annelid, annelid worms, common name, commonly called bristle worms or polychaetes (). Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called c ...

sipunculid The Sipuncula or Sipunculida (common names sipunculid worms or peanut worms) is a class containing about 162 species of sea, marine Annelid, annelid worms, that have secondarily lost their segmentation. Sipuncula was once considered a phylum of ...

s and

tunicate Tunicates are marine invertebrates belonging to the subphylum Tunicata ( ). This grouping is part of the Chordata, a phylum which includes all animals with dorsal nerve cords and notochords (including vertebrates). The subphylum was at one time ...

s may also be eaten. Dietary preferences change with age; younger animals prefer small crustaceans, while older animals prefer hermit crabs and molluscs. Feeding intensity is highest during the summer due to the higher availability of prey life. Diet composition varies with body size. There are no significant differences in feeding habits between male and female ''S. canicula''. Juveniles of ''S. canicula'' feed by anchoring the prey item on the

dermal denticle A fish scale is a small rigid plate that grows out of the skin of a fish. The skin of most jawed fishes is covered with these protective scale (zoology), scales, which can also provide effective Underwater camouflage, camouflage through the us ...

s near their tail, and tearing bite-sized pieces off with rapid head and jaw movements, a behaviour known as "scale rasping". Use of dermal denticles to assist in feeding was first documented in this species.

Psychology

A study published in 2014 at

Exeter University The University of Exeter is a research university in the West Country of England, with its main campus in Exeter, Devon. Its predecessor institutions, St Luke's College, Exeter School of Science, Exeter School of Art, and the Camborne School o ...

showed that individual small-spotted catsharks have different

personality traits In psychology, trait theory (also called dispositional theory) is an approach to the study of human personality. Trait theorists are primarily interested in the measurement of ''traits'', which can be defined as habitual patterns of behavior, thou ...

. Some individuals are more sociable than others, some more aggressive, some more exploratory in nature.

Model organism

''S. canicula'' is well-suited for comparative analysis of

gastrulation Gastrulation is the stage in the early embryonic development of most animals, during which the blastula (a single-layered hollow sphere of cells), or in mammals, the blastocyst, is reorganized into a two-layered or three-layered embryo known as ...

for several reasons. * It is harvested in large numbers along all the coasts of Europe, and it is the only known

species from which individuals at any stage of development can be obtained in abundance at any time of year. * Fertilization is internal, but eggs are laid at early stages of development, before the formation of the

blastocoel The blastocoel (), also spelled blastocoele and blastocele, and also called cleavage cavity, or segmentation cavity is a fluid-filled or yolk-filled cavity that forms in the blastula during very early embryonic development. At this stage in mammal ...

. Once laid, they can go on developing normally in the laboratory, simply in oxygenated seawater.Mazan, S., Sauka-Splengler, T. 2004. "Gastrulation in the chondrichthyan, the dogfish ''Scyliorhinus canicula''." ''Gastrulation: from cells to embryo''. Ed. Claudio D. Stern. Cold Spring Harbor Laboratory Press. New York, NY, 151–155 pp. * The size and accessibility of the embryo makes analysis easier. * Five well-characterized stages can be distinguished between the onset of gastrulation and the beginning of

neurulation Neurulation refers to the folding process in vertebrate embryos, which includes the transformation of the neural plate into the neural tube. The embryo at this stage is termed the neurula. The process begins when the notochord induces the formati ...

Threat level

''S. canicula'' is one of the most abundant elasmobranchs in the northeast Atlantic and Mediterranean. It is regularly caught by near-shore fisheries, but the majority taken by commercial fishermen and recreational anglers are discarded. Studies have shown that post-discard survival rates are extremely high, around 98%. Although localized depletion may have occurred in some areas, surveys have shown that populations are stable or are even increasing throughout the majority of its range. However, continued monitoring of landing and discarded data is important to avoid any future decline. This species is currently listed as being of

least concern A least-concern species is a species that has been evaluated and categorized by the International Union for Conservation of Nature (IUCN) as not being a focus of wildlife conservation because the specific species is still plentiful in the wil ...

on the

IUCN Red List of Threatened Species The International Union for Conservation of Nature (IUCN) Red List of Threatened Species, also known as the IUCN Red List or Red Data Book, founded in 1964, is an inventory of the global conservation status and extinction risk of biological spe ...

, because there is no evidence to indicate that the global population has declined significantly. Since 2003, there have been yearly releases of these sharks into the Gullmarn fjord in Sweden by the public aquaria Havets Hus in

Lysekil Lysekil () is a Urban areas in Sweden, locality and the seat of Lysekil Municipality in Västra Götaland County, Sweden. It had about 7,600 inhabitants in 2018. Situated on the south tip of Stångenäs peninsula at the mouth of Gullmarn fjord, it ...

. More than 90 sharks have been released since 2003, of which one was found in southern Norway 10 years after its release. This means that these sharks can reach at least an age of 14 years.

Human consumption and use

''S. canicula'' is currently of low commercial value. In the recent past, it was one of the species sold in English and Scottish fish and chip shops as rock salmon, rock eel, huss, or sweet william. In other parts of its range, it is occasionally baked or used in fish soup. Its hard skin has been used as a substitute for

pumice Pumice (), called pumicite in its powdered or dust form, is a volcanic rock that consists of extremely vesicular rough-textured volcanic glass, which may or may not contain crystals. It is typically light-colored. Scoria is another vesicula ...

, but the fact that catsharks have to be skinned before they can be filleted discourages commercial fishermen from catching this species.

References

External links

* * * {{Authority control small-spotted catshark small-spotted catshark Fish of the East Atlantic Fish of the Mediterranean Sea Marine fish of North Africa small-spotted catshark