NURSEHOUND

Taxonomy:

Phylum– Chordata

Class– Chondrichthyles

Order– Carcharhiniformes

Common Name– Ground Sharks

Family– Scyliorhinidae

Common Name– Catsharks

Genus– Scyliorhinus

Species– stellaris

Status: IUCN Red List NEAR THREATENED

Average Size and Length: Each egg case measures between 10-13 cm/3.9-5.1 inches long. Hatchlings have measured around 16 cm/6.3 inches. It is common for them to reach 125 cm/4.1 feet and the maximum recorded has been 162 cm/5.3 feet.

Current Rare Mythical Sightings: The first scientific description of the Nursehound was published by Carl Linnaeus, in the 1758 tenth edition of Systema Naturae. He gave it the name Squalus stellaris, the specific epithet stellaris being Latin for “starry”. No type specimen was designated. In 1973, Stewart Springer moved this species to the genus Scyliorhinus.

The common name “Nursehound” came from an old belief by English fishermen that this shark attends to its smaller relatives, while the name “Huss” may have come from a distortion of the word “nurse” over time.

Teeth and Jaw: In the upper jaw, there are 22–27 tooth rows on either side and 0–2 teeth at the symphysis. In the lower jaw, there are 18–21 tooth rows on either side and 2–4 teeth at the symphysis. The teeth are Y-shaped and smooth-edged. The anterior teeth have a single central cusp, while the posterior teeth have an additional pair of lateral cusplets. Towards the rear of the jaws, the teeth become progressively smaller and more angled, with proportionately larger lateral cusplets. The teeth are slender, with one extremely long, pointed straight central cusp and two very tiny, almost non-visible surrounding cusplets on the top rows, and the single cusp on the bottom rows.

Head: The head is broad and rounded. It differs from the Smallspotted catshark in that its nasal skin flaps do not extend to the mouth. The eyes are oval in shape, with a thick fold of skin on the lower rim but no nictitating membrane.

Denticles: The dermal denticles are upright, giving the skin a rough feel to the touch.

Tail: The caudal fin is broad and nearly horizontal, with an indistinct lower lobe.

Demographic, Distribution, Habitat, Environment and Range: The Nursehound can be found in the northeast Atlantic in southern Scandinavia to the Mediterranean, Morocco, the Canary Islands, Mauritania to Senegal (°N – 12°N, 18°W – 36°E). There are records further south to the Gulf of Guinea and the Congo River mouth, but more than likely these are sightings of the West African catshark. They can be found on the continental shelf between 1-410 feet, and more commonly found between 66-207 feet on rocky or seaweed covered bottoms. Its range around the island chains seems to be patchy. It shares its range with the more common and closely related Smallspotted catshark. They are considered benthic subtropical.

Known breeding grounds include the River Fal estuary and Wembury Bay in England, and a number of coastal sites around the Italian Peninsula, in particular the Santa Croce Bank in the Gulf of Naples. Adults move into shallow water in the spring or early summer, and mate only at night.

Diet: The Nursehound eats mostly crustaceans (crabs, hermit crabs and large shrimp), cephalopods, other mollusks, bony fish and even other small sharks like the Smallspotted catshark. Some bony fish include mackerel, deep-water cardinalfishes, dragonets, gurnards, flatfishes, and herring. Juveniles eat more crustaceans.

The Netted Dog whelk Nassarius reticulatus preys on the Nursehound’s eggs by piercing the case and extracting what is inside.

Aesthetic Identification: The Nursehound is robust, large and stalky, tapering towards the tail, with many small and large black spots, with sometimes white spots all over a pale greyish or brownish background. The saddles are extremely faint or absent altogether. The large spots may be irregular, occasionally expanded into large blotches covering the body. The ventral side is pale white. The five pairs of gill slits are small, with the last two over the pectoral fin bases. The two dorsal fins are placed far back. The first dorsal fin is larger than the second and originates over the bases of the pelvic fins. The pectoral fins are large. In males, the inner margins of the pelvic fins are merged into an apron over the claspers. It differs from the Smallspotted catshark in that it has larger spots.

Biology and Reproduction: The Nursehound is oviparous, having a single egg per oviduct. They lay their eggs in spring and summer (March to October). They deposit large, thick-walled egg cases with strong tendrils on the corners gripping them on algae or seaweed. They may take up to nine months to hatch, but sometimes as few as seven and as many as twelve; eggs in the North Sea and the Atlantic take 10–12 months to hatch, while those from the southern Mediterranean take 7 months to hatch.

Although a single female produces 77–109 oocytes per year, not all of these are ovulated and estimates of the actual number of eggs laid range from 9 to 41.

Newly hatched Nursehounds grow at a rate of 0.45–0.56 mm per day and have prominent saddle markings. Sexual maturity is attained at a length of 77–79 cm/2.5-2.6 feet, which corresponds to an age of four years if hatchling growth rates remain constant. The Nursehound has a lifespan of at least 19 years.

Known parasites of the Nursehound include the monogeneans Hexabothrium appendiculatum and Leptocotyle major, the tapeworm Acanthobothrium coronatum, the trypanosome Trypanosoma scyllii, the isopod Ceratothoa oxyrrhynchaena, and the copepod Lernaeopoda galei.

Behavioral Traits, Sensing and Intelligence: Nursehounds are nocturnal, generally hiding inside small holes during the day often in small groups. Some have even been seen squeezing into the same small hole. It may swim into deeper water at night to hunt. It is also a known scavenger.

In one tracking study, a single immature Nursehound was observed to use five different refuges in succession over a period of 168 days, consistently returning to each one over a number of days before moving on. Nursehounds may occupy refuges to hide from predators, avoid harassment by mature conspecifics, and/or to facilitate thermoregulation. (Sims, D.W.; Southall, E.J.; Wearmouth, V.J.; Hutchinson, N.; Budd, G.C. & Morritt, D. (2005). “Refuging behaviour in the nursehound Scyliorhinus stellaris (Chondrichthyes: Elasmobranchii): preliminary evidence from acoustic telemetry“. Journal of the Marine Biological Association of the United Kingdom. 85 (5): 1137–1140).

In captivity, the Nursehounds are sociable and tend to rest in groups, though the individuals comprising any particular group changes frequently.

Nursehound Future and Conservation: They are currently listed as near threatened. They are less common among their range and in the Mediterranean their populations have declined from overfishing. In some European countries, Nursehounds are considered food under various names, including “flake”, “catfish”, “rock eel”, and “rock salmon”. It was once also valued for its rough skin (called “rubskin”), which was used as an abrasive. Rubskin was once so valued that a pound of it was worth a hundredweight of sandpaper. The liver was also used as a source of oil, and the carcasses cut up and used to bait crab traps.

The Nursehound is also sometimes processed into fishmeal, or its fins dried and exported to the Asian market. In European waters, commercial production of this species is led by France, followed by the UK and Portugal; it is caught using bottom trawls, gillnets, bottom set longlines, handlines and fixed bottom nets. In 2004, a total catch of 208 tons was reported from the northeastern Atlantic.

There is evidence that its numbers have declined significantly in the Gulf of Lion, off Albania, and around the Balearic Islands. In the upper Tyrrhenian Sea, its numbers have fallen by over 99% since the 1970s.

The Nursehound is displayed by many public aquariums and has been bred in captivity.

Nursehound Recorded Attacks on Humans: They are not a threat to humans but could do some damage with its teeth if you get too close and harass it.