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Nursehound
Photo of a nursehound, a small yellow shark with many large dark spots and a rounded head, resting on the bottom
Scientific classification Edit this classification
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Subclass: Elasmobranchii
Division: Selachii
Order: Carcharhiniformes
Family: Scyliorhinidae
Genus: Scyliorhinus
Species:
S. stellaris
Binomial name
Scyliorhinus stellaris
World map with blue outlines on the coastlines of southern Scandinavia, northern Europe, the British Isles, the Iberian Peninsula, the Mediterranean, and northwest Africa as far as the equator
Range of the nursehoundV
Synonyms

Scyllium acanthonotum* De Filippi, 1857
Scyllium catulus Müller & Henle, 1838
Squalus stellaris Linnaeus, 1758

* ambiguous synonym

The nursehound (Scyliorhinus stellaris), also known as the large-spotted dogfish, greater spotted dogfish or bull huss, is a species of catshark, belonging to the family Scyliorhinidae, found in the northeastern Atlantic Ocean. It is generally found among rocks or algae at a depth of 20–60 m (66–197 ft). Growing up to 1.6 m (5.2 ft) long, the nursehound has a robust body with a broad, rounded head and two dorsal fins placed far back. It shares its range with the more common and closely related small-spotted catshark (S. canicula), which it resembles in appearance but can be distinguished from, in having larger spots and nasal skin flaps that do not extend to the mouth.

Nursehounds have nocturnal habits and generally hide inside small holes during the day, often associating with other members of its species. A benthic predator, it feeds on a range of bony fishes, smaller sharks, crustaceans, and cephalopods. Like other catsharks, the nursehound is oviparous in reproduction. Females deposit large, thick-walled egg cases, two at a time, from March to October, securing them to bunches of seaweed. The eggs take 7–12 months to hatch. Nursehounds are marketed as food in several European countries 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. The International Union for Conservation of Nature (IUCN) has assessed the nursehound as Vulnerable, as its population in the Mediterranean Sea seems to have declined substantially from overfishing.

Taxonomy

[edit]
Early illustration of a nursehound from Les poissons (1877).

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.[2][3] 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.[4]

Distribution and habitat

[edit]

The nursehound is found in the northeastern Atlantic from southern Norway and Sweden to Senegal, including off the British Isles, throughout the Mediterranean Sea, and the Canary Islands. It may occur as far south as the mouth of the Congo River, though these West African records may represent misidentifications of the West African catshark (S. cervigoni).[5] Its range seems to be rather patchy, particularly around offshore islands, where there are small local populations with limited exchange between them.[1] The nursehound can be found from the intertidal zone to a depth of 400 m (1,300 ft), though it is most common between 20 m (66 ft) and 60–125 m (197–410 ft).[1] This bottom-dwelling species prefers quiet water over rough or rocky terrain, including sites with algal cover. In the Mediterranean, it favors algae-covered coral.[2][6]

Description

[edit]
Photo of a nursehound with crosswise dark bands, swimming over a strip from a fishing net
Young nursehounds have prominent saddle markings.

The nursehound attains a length of 1.6 m (5.2 ft), though most measure less than 1.3 m (4.3 ft).[2] This shark has a broad, rounded head and a stout body that tapers towards the tail. The eyes are oval in shape, with a thick fold of skin on the lower rim but no nictitating membrane. Unlike in the small-spotted catshark, the large flaps of skin beside the nares do not reach the mouth.[6] In the upper jaw, there are 22–27 tooth rows on either side and 0–2 teeth at the symphysis (center); 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.[7] The five pairs of gill slits are small, with the last two over the pectoral fin bases.[6]

The two dorsal fins are placed far back on the body; the first 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. The caudal fin is broad and nearly horizontal, with an indistinct lower lobe. The skin is very rough, due to a covering of large, upright dermal denticles.[2] The nursehound has small black dots covering its back and sides, interspersed with brown spots of varying shapes larger than the pupil, on a grayish or brownish background. The pattern is highly variable across individuals and ages; there may also be white spots, or the brown spots may be expanded so that almost the whole body is dark, or a series of faint "saddles" may be present. The underside is plain white.[5][6]

Biology and ecology

[edit]

Primarily nocturnal, nursehounds spend the day inside small holes in rocks and swim into deeper water at night to hunt. Sometimes two sharks will squeeze into the same hole, and several individuals will seek out refuges within the same local area. 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.[8] In captivity, these sharks are gregarious and tend to rest in groups, though the individuals comprising any particular group changes frequently.[9] This species is less common than the small-spotted catshark.[6]

The nursehound feeds on a variety of benthic organisms, including bony fishes such as mackerel, deepwater cardinalfishes, dragonets, gurnards, flatfishes, and herring, and smaller sharks such as the small-spotted catshark. It also consumes crustaceans, in particular crabs but also hermit crabs and large shrimp, and cephalopods.[2][10] Given the opportunity, this shark will scavenge.[6] Adults consume relatively more bony fish and cephalopods, and fewer crustaceans, than juveniles.[1] Known parasites of this species include the monogeneans Hexabothrium appendiculatum and Leptocotyle major,[11][12] the tapeworm Acanthobothrium coronatum,[13] the trypanosome Trypanosoma scyllii,[14] the isopod Ceratothoa oxyrrhynchaena,[15] and the copepod Lernaeopoda galei.[16] The netted dog whelk (Nassarius reticulatus) preys on the nursehound's eggs by piercing the case and extracting the yolk.[17]

Life history

[edit]
photo of nursehound egg capsules hanging in an aquarium, some cut open to show the embryo sharks inside
Nursehound egg capsules, some with their cases cut open to show the embryos inside.

Like other members of its family, the nursehound is oviparous. Known breeding grounds include the River Fal estuary and Wembury Bay in England,[17] and a number of coastal sites around the Italian Peninsula, in particular the Santa Croce Bank in the Gulf of Naples.[18] Adults move into shallow water in the spring or early summer, and mate only at night.[19] The eggs are deposited in the shallows from March to October.[10] 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.[19] The eggs mature and are released two at a time, one from each oviduct.[2] Each egg is enclosed in a thick, dark brown case measuring 10–13 cm (3.9–5.1 in) long and 3.5 cm (1.4 in) wide. There are tendrils at the four corners, that allow the female to secure the egg cases to bunches of seaweed (usually Cystoseira spp. or Laminaria saccharina).[17]

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. The length at hatching is 16 cm (6.3 in) off Britain, and 10–12 cm (3.9–4.7 in) off France. Newly hatched sharks grow at a rate of 0.45–0.56 mm (0.018–0.022 in) per day, and have prominent saddle markings. Sexual maturity is attained at a length of 77–79 cm (30–31 in), which corresponds to an age of four years if hatchling growth rates remain constant.[10][19] This species has a lifespan of at least 19 years.[20]

Human interactions

[edit]
photo of a nursehound in a public aquarium
A nursehound in a public aquarium; this species adapts well to captivity.

Nursehounds are generally harmless to humans.[21] However, 19th-century British naturalist Jonathan Couch noted that "although not so formidable with its teeth as many other sharks, this fish is well able to defend itself from an enemy. When seized it throws its body round the arm that holds it, and by a contractile and reversed action of its body grates over the surface of its enemy with the rugged spines of its skin, like a rasp. There are few animals that can bear so severe an infliction, by which their surface is torn with lacerated wounds."[22] This shark is displayed by many public aquariums and has been bred in captivity.[9]

The rough skin (called "rubskin") of the nursehound was once used to polish wood and alabaster, to smooth arrows and barrels, and to raise the hairs of beaver hats as a replacement for pumice. Rubskin was so valued that a pound of it was worth a hundredweight of sandpaper.[23][24] The liver was also used as a source of oil, and the carcasses cut up and used to bait crab traps.[23] The meat of this species is marketed fresh or dried and salted, though it is considered "coarse" in some quarters.[21][23] In the United Kingdom, it is one of the species sold under the names "flake", "catfish", "huss" "rock eel" or "rock salmon".[4][25] In France, it is sold as grande roussette or saumonette, as after being skinned and beheaded it resembles salmon.[26] This species 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.[1][2][27]

The impact of fishing activities on the nursehound is difficult to assess as species-specific data is generally lacking. This species is more susceptible to overfishing than the small-spotted catshark because of its larger size and fragmented distribution, which limits the recovery potential of depleted local stocks. There is evidence that its numbers have declined significantly in the Gulf of Lion, off Albania, and around the Balearic Islands.[1] In the upper Tyrrhenian Sea, its numbers have fallen by over 99% since the 1970s.[28] These declines have led the International Union for Conservation of Nature (IUCN) to list the nursehound as Vulnerable.[1]

References

[edit]
[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Nursehound

View on Grokipedia
from Grokipedia

The nursehound (Scyliorhinus stellaris), also known as the large-spotted dogfish or bull huss, is a of catshark in the family Scyliorhinidae, endemic to the coastal waters of the northeast from southern to , including the Mediterranean and Black Seas. This benthic attains a maximum total length of 1.6 meters, featuring a slender yet stocky build with prominent dark spots and saddles on a yellowish-brown body. It inhabits rocky and sandy seabeds from the to depths of 400 meters, though most commonly between 20 and 125 meters, where it remains largely inactive by day, sheltering in crevices or caves. The nursehound is oviparous, depositing pairs of distinctive purse-shaped egg cases containing embryos that develop over several months, and sustains itself primarily on bottom-dwelling crustaceans, mollusks, and small pursued nocturnally. Classified as Vulnerable on the owing to population declines from targeted fisheries, , and habitat loss, the faces ongoing conservation challenges despite some regional protections.

Taxonomy and nomenclature

Scientific classification

The nursehound is formally classified in the domain Eukarya, kingdom Animalia, phylum Chordata, class Chondrichthyes, subclass Elasmobranchii, order Carcharhiniformes, family Scyliorhinidae, subfamily Scyliorhininae, genus Scyliorhinus, and species Scyliorhinus stellaris (Linnaeus, 1758). This placement reflects its position among ground sharks characterized by cartilaginous skeletons, multiple gill slits, and oviparous reproduction typical of catsharks. Phylogenetic analyses using molecular data affirm the monophyly of the Scyliorhinidae family within , with S. stellaris nested among other catsharks in the genus Scyliorhinus. Sequencing of the complete mitochondrial genome of S. stellaris in 2022 demonstrated its close genetic affinity to congeners such as the (S. canicula), supporting a structure within the Scyliorhininae and highlighting low interspecific divergence driven by shared coastal habitats. These findings align with broader molecular phylogenies of chondrichthyans, where catsharks diverged from other elasmobranch lineages in the , though precise divergence estimates for Scyliorhinus species remain constrained by limited fossil-calibrated data.

Etymology and synonyms

The binomial name Scyliorhinus stellaris combines the genus Scyliorhinus, derived from skylion (dogfish or small shark) and rhine (rasp), alluding to the species' rough, denticle-covered skin, with the specific epithet stellaris, Latin for "starry" or "star-like," referring to the prominent dark spots resembling a starry pattern across its body. The species was first described by in 1758 as Squalus stellaris within the then-broad Squalus encompassing various . Common names reflect regional and descriptive usage, including "nursehound," originating from an early English fishermen's that the "nurses" or guards smaller relatives due to its relatively docile demeanor when handled; "bull huss," where "" denotes its bulkier form compared to smaller dogfishes and "huss" is an archaic English term for dogfish derived from phonetic adaptations of older Nordic or regional dialects; and "greater spotted dogfish," a descriptive English name emphasizing its larger size and spotted patterning to distinguish it from the similar but smaller Scyliorhinus canicula (lesser spotted catshark). Historical synonyms include Catulus stellaris (post-Linnaean reassignment to a junior ) and Scyllium acanthonotum (an 1857 description by Filippo De Filippi, later synonymized upon recognition of consistent morphological traits like spot size and body proportions). Early taxonomic confusion arose with S. canicula, leading to misidentifications in 19th-century records until vertebral counts and maximum size (up to 165 cm for S. stellaris versus under 100 cm for S. canicula) clarified distinctions in the early .

Physical characteristics

Morphology and identification

The nursehound (Scyliorhinus stellaris) exhibits a moderately broad head and body, with the greatest head width comprising about two-thirds of its head length. The body is elongated and fairly stocky, tapering posteriorly, with a depressed but not extremely so head profile and a short, bluntly rounded . Eyes are large, oval, and positioned dorsolaterally, featuring a thick fold on the lower rim, while openings are small, with the last not reaching eye level. Nasal flaps are expanded and rounded, extending but not quite reaching the mouth, without nasoral grooves, and anterior flaps remain unexpanded; these structures, along with labial furrows, aid in sensory detection on the seafloor. Fins include large, angular pectorals, with the first originating behind their free rear tips, over or slightly posterior to pelvic bases; the second dorsal is larger, positioned behind anal fin insertion. The anal fin displays a marked posterior indentation, and the caudal fin has a pronounced subterminal notch and well-developed lower lobe, lacking a ventral on the peduncle. Coloration consists of a yellowish-brown to grayish background dorsally, marked by large, close-set dark spots of similar size, interspersed with smaller black dots on body and , without white spots or saddles; ventral surfaces are paler. is covered in dermal denticles with multiple ridges, including five above pectoral fins where the median ridge is less prominent and does not extend fully to the crown apex, contributing to texture for identification and protection. Dentition features small, pointed teeth arranged in multiple rows, with upper jaw teeth typically bearing 3-5 cusps and lower jaw teeth more slender and pointed, exhibiting intraspecific variation that supports species differentiation within the genus via micro-computed tomography analysis. are distributed across the head, enhancing electroreception for prey detection in benthic environments. These traits collectively distinguish the nursehound from congeners like the (S. canicula), which has smaller spots and saddles.

Size, growth, and sexual dimorphism

The nursehound (Scyliorhinus stellaris) attains a maximum total length of approximately 165 cm, though commonly observed lengths are 50–100 cm; females generally reach larger maximum sizes than males. occurs at around 77 cm total length in males and 79 cm in females, corresponding to an estimated age of four years based on growth trajectories from . Growth data for the are limited, with no extensive tag-recapture studies available; however, juveniles hatch from eggs at 10–16 cm and exhibit steady somatic growth to reach maturity by age four, assuming consistent rates from early life stages. The lifespan is estimated at 19–20 years. is evident in reproductive structures, with males developing paired claspers on the pelvic fins for internal sperm transfer, while females possess specialized oviducal glands that secrete leathery, rectangular egg capsules measuring up to 12 cm long by 4 cm wide for oviposition. Females also exhibit subtle differences in and morphology compared to males, potentially linked to ontogenetic and dietary adaptations.

Distribution and habitat

Geographic range

The nursehound (Scyliorhinus stellaris) is distributed across the northeast , from southern southward to , encompassing coastal waters of the , , and northwest , as well as the . Its range includes the but excludes the due to unsuitable low-salinity conditions, and it occurs only patchily within much of the . Populations exhibit a patchy distribution throughout this extent, with verified records indicating higher relative abundances in areas such as the western and the . Recent surveys conducted from 2018 to 2024 have confirmed ongoing presence in Tuscan coastal waters off , including observations of spawning activities at depths of 25 to 50 meters. The Fal Estuary in , , remains a documented site for breeding grounds based on historical and continued records of egg-laying. Southern extensions to the are reported in some accounts but considered doubtful and unverified in contemporary assessments.

Environmental preferences and microhabitats

The nursehound (Scyliorhinus stellaris) primarily occupies benthic habitats on continental shelves at depths of 10–400 m, with peak abundances typically recorded between 20 and 63 m. It exhibits a strong preference for structurally complex, hard-bottom substrates such as rough rocky reefs, coralline grounds, and areas with macroalgal cover, which provide essential refuges including crevices and small caves. These microhabitats facilitate daytime concealment, with individuals often resting motionless within rocky interstices to avoid predation and conserve energy. Abiotic tolerances include seawater temperatures of 7.8–19.5°C, aligning with temperate northeastern Atlantic and Mediterranean conditions where bottom rarely exceeds this range. The avoids soft sedimentary bottoms like mud or sand, which lack the structural heterogeneity required for refuge and are less conducive to its ambush-oriented . While full marine salinities predominate, occasional occurrences in semi-enclosed coastal areas suggest moderate tolerance to slight fluctuations, though empirical data on thresholds remain limited. Habitat suitability models for Mediterranean elasmobranchs, including the nursehound, underscore seafloor and depth as primary predictors of occurrence over softer substrates.

Behavior and ecology

Activity patterns and social behavior

The nursehound (Scyliorhinus stellaris) displays predominantly nocturnal activity patterns, remaining largely benthic and inactive during daylight hours, when individuals seek refuge in caves, rocky crevices, or labyrinthine structures. Acoustic telemetry tracking of a sub-adult male over 168 days in a tidal lough revealed diel cycles characterized by minimal movement during the day, with philopatric fidelity to specific "" refuges, contrasting with more extensive nocturnal excursions. Social behavior is generally solitary or involves loose aggregations of conspecifics within refuges, often squeezing into confined spaces without evidence of coordinated or territorial hierarchies typical of some larger elasmobranchs. These groupings appear opportunistic, centered on rather than persistent social bonds, as supported by observations of multiple individuals sharing refuge sites during diurnal periods. In response to perceived threats, nursehounds erect their dermal denticles—rough, spine-like scales—for defensive posturing and may deliver bites when handled or provoked, reflecting an aggressive antipredator strategy suited to their cryptic lifestyle. Limited data indicate low overall interaction rates, with no documented complex signaling or behaviors beyond refuge sharing.

Diet, foraging, and predators

The nursehound (Scyliorhinus stellaris) functions as an opportunistic benthic predator, with its diet comprising bottom-dwelling such as crustaceans and mollusks, alongside demersal fishes and cephalopods; smaller sharks like the (S. canicula) are also consumed occasionally. content analyses of specimens from the yielded 52 prey items across 13 taxa, with cephalopods emerging as the dominant group—represented by nine taxa and constituting the most diverse and abundant component, underscoring a specialized trophic role in Mediterranean ecosystems. Foraging occurs primarily at night over rough, rocky, or algae-covered seabeds at depths of 20–63 m, where the employs chemosensory detection via olfactory organs to locate prey in low-light conditions, consistent with elasmobranch sensory adaptations to chemical stimuli. This nocturnal strategy aligns with ambush tactics targeting mobile or sessile benthic organisms, though evidence for pronounced seasonal dietary shifts remains limited in available analyses. As a , the nursehound faces predation from larger elasmobranchs such as sharks and rays, as well as demersal fishes, though specific predator-prey interactions are sparsely documented. Its metazoan parasite community is depauperate, featuring one monogenean (Hexabothrium appendiculatum) and three intestinal cestodes (Acanthobothrium coronatum, Yamaguticestus sp., Scyphophyllidium sp.), with A. coronatum for approximately 80% of total parasite abundance in examined hosts from the central Mediterranean. This low-diversity assemblage reflects the shark's position in coastal food webs with constrained parasite transmission opportunities.

Reproduction, life cycle, and genetics

The nursehound (Scyliorhinus stellaris) is oviparous, with females depositing leathery, rectangular cases in pairs, typically attaching them to macroalgae or securing them within rocky crevices for . Egg-laying occurs year-round, though peaking from spring to summer in temperate regions. Embryonic development within the egg case spans 9-12 months under natural conditions, during which the relies solely on for nourishment until as a fully formed miniature adult. Juveniles emerge at a total length of approximately 16 cm. Females exhibit evidence of sperm storage, enabling egg fertilization over extended periods post-mating, as demonstrated in captivity where hatching occurred across multiple years from a single insemination event. Fecundity varies, with captive studies recording 27-42 eggs laid per female over observation periods, though annual production may reach up to 100 eggs based on extended breeding records. Sexual maturity is attained at total lengths of 77 cm for males and 79 cm for females, corresponding to ages of roughly 4-6 years inferred from growth trajectories in controlled environments. Post-hatching, juveniles undergo gradual growth, transitioning to predatory feeding and reaching adult sizes exceeding 1 m over several years. Recent genetic analyses reveal protective mechanisms in eggs, including slight antibacterial activity in unfertilized samples against gram-positive pathogens like Staphylococcus aureus and Listeria monocytogenes, potentially aiding embryo viability by limiting microbial intrusion. The complete mitochondrial genome, sequenced in 2022 at 16,684 base pairs, facilitates phylogenetic placement within Scyliorhinidae, highlighting close relations to congeners and low genetic variability among Balearic populations, which informs conservation genetics for this species.

Conservation and threats

The nursehound (Scyliorhinus stellaris) is classified as Vulnerable on the , with the assessment conducted on 31 August 2020 under criterion A2bd, reflecting suspected reductions exceeding 30% over the past three generations based on observed regional declines and limited quantitative . Overall trends are decreasing, as indicated by the IUCN evaluation, though comprehensive global abundance metrics remain unavailable due to patchy historical and challenges in surveying demersal habitats. In the , empirical evidence points to substantial regional declines, with the species documented widely between the 1950s and 1990s but showing marked scarcity in recent decades across multiple subregions, including potential local extinctions in isolated areas. Fisher perceptions and trawl survey records corroborate these reductions, estimating declines of 30–50% in targeted areas like the central Mediterranean over multi-decadal scales. Nursery surveys in locations such as the , initiated around 2018, provide ongoing monitoring of juvenile densities but have yet to reverse indications of localized vulnerability. Northeast Atlantic populations, however, exhibit stability according to ICES assessments for subareas 6 and 7 (Celtic Seas to ), where trend indices hovered at 1.47 in 2023–2024 compared to 1.35 in 2021–2022, yielding a near unity that signals no directional shift. Corresponding landings averaged 638 tonnes annually from to 2022, consistent with prior periods and supporting inferences of sustained levels from fisheries-independent bottom-trawl surveys. These regional contrasts highlight localized rather than uniform risks, with no data suggesting imminent global despite the Vulnerable designation.

Primary threats and vulnerabilities

Intensive demersal fisheries targeting whitefish and other bottom-dwelling species capture nursehounds as in trawls, gillnets, and longlines, contributing to population declines across their range, particularly in the where fishing pressure has driven inferred reductions exceeding 30% over three generations. Targeted fisheries also exploit aggregations during breeding seasons, while recreational in coastal areas of the northeastern Atlantic adds mortality to adults. These impacts are compounded by the species' K-selected life history, including late at approximately 78 cm total length for both sexes—likely requiring 4–6 years given growth rates observed in congeners—and low annual of 30–40 eggs per female in captive conditions, limiting population recovery potential. High site fidelity to specific refuging, breeding, and nursery areas increases susceptibility to localized depletion, as individuals repeatedly return to the same benthic sites, exposing predictable aggregations to repeated fishing encounters. further constrains resilience, with protracted embryonic development (7–12 months) and yolk-dependent hatching at 11–16 cm, yielding few recruits amid ongoing adult removal. In efforts for conservation restocking, nursehounds demonstrate vulnerability to opportunistic pathogens; a 2023 histopathological study identified Photobacterium spp. as the causative agent of acute hemorrhagic septicemia in eight specimens that succumbed after 18 months in aquaria, highlighting risks from bacterial proliferation in confined, potentially stressed conditions.

and habitat change impacts

Ocean warming is projected to affect the nursehound's thermal habitat, with models under high-emission scenarios (SSP5-8.5) predicting reduced early-stage and delayed maturation, potentially lowering reproductive output for this late-maturing species. Such physiological responses stem from temperature-sensitive metabolic processes in ectothermic elasmobranchs, where elevated temperatures beyond optimal ranges (typically 12–20°C for nursehounds) could impair embryonic development and juvenile growth rates. Empirical observations of these effects remain sparse, as current population declines are primarily attributed to rather than climatic factors. Projected poleward range expansions in the northeast Atlantic may occur as southern s, particularly in the warming Mediterranean, become less suitable, leading to potential contractions in core distribution areas. The nursehound's dependence on coastal refugia for resting and egg-laying limits rapid dispersal, increasing risks from habitat mismatches where warming alters prey distributions or microhabitat stability, such as reduced macroalgal cover on seabeds. data on related catsharks suggest behavioral adjustments like altered refuge use under stress, but long-term monitoring for nursehounds is insufficient to confirm causal links to climate-driven shifts. Ocean , with projected pH declines of 0.14–0.5 units by 2100, shows limited direct impacts on nursehounds, though congeneric species exhibit disrupted acid-base regulation and behavioral changes under hypercapnic conditions. Interactions between warming and acidification could compound vulnerabilities during sensitive life stages, such as egg incubation on sedimented substrates prone to localized hypoxia, but species-specific data are provisional and model-dependent. Overall, while vulnerability assessments underscore elevated risks for narrowly distributed, low-mobility sharks, the paucity of direct tempers conclusions beyond projections.

Human interactions and utilization

Commercial and recreational fisheries

The nursehound is targeted in small-scale commercial fisheries in the northeastern Atlantic, particularly in ICES subareas 6 and 7 encompassing the west of Scotland, southern Celtic Sea, and English Channel, where it is caught using bottom trawls, gillnets, and traps for human consumption including in fish and chips preparations in the United Kingdom. ICES advises that landings should not exceed 758 tonnes annually in these areas for 2024 and 2025 to align with maximum sustainable yield principles, reflecting reported historical landings and stock assessments indicating stable but managed exploitation levels. In the Mediterranean Sea, commercial landings remain minimal, with approximately 5 tonnes reported in 2022, primarily as bycatch in demersal fisheries rather than directed effort. There is no total allowable catch or minimum landing size established for the species in these regions as of recent assessments. Recreational angling for nursehounds, known locally as bull huss in the British Isles, occurs via shore and boat methods using baits such as mackerel or squid over rocky or kelp-covered grounds, particularly in spring and summer when fish aggregate near coasts. Anglers value the species for sport due to its size—up to 16 pounds or more—and fighting behavior, with charters available in areas like North Devon and Anglesey targeting it alongside other demersal species. Human encounters pose low risk, though occasional bites can occur during handling due to the shark's oral dentition. Commercial utilization sometimes incorporates recreationally caught specimens, but directed angling contributes negligibly to overall harvest compared to professional fisheries.

Aquaculture, captivity, and research applications

The nursehound (Scyliorhinus stellaris) adapts well to , making it suitable for display in s and as a for elasmobranch research. Institutions maintain specimens under human care to study , , and , leveraging the species' oviparous nature and tolerance for confined environments. Captive breeding programs target conservation, particularly in regions with declining populations. The Acció Stellaris initiative in the , launched in 2021, has bred over 200 juveniles in captivity and released 141 into protected marine areas by December 2024 to bolster local stocks. Protocols for and juvenile rearing support reintroduction efforts, with enhancing growth rates in bred individuals. A 2018 conservation method involves salvaging viable egg cases from incidentally caught or dead females in fisheries, incubating them ex situ to increase hatchling survival without impacting wild breeding. Research applications include establishing baseline health metrics and testing therapeutics. In 2022, and plasma chemistry reference intervals were derived from 94 captive nursehounds, aiding veterinary assessments in . Pharmacokinetic studies in 2025 evaluated dosing—administered orally at 50 mg/kg or intramuscularly/intravenously at 4 mg/kg—for treating fungal infections, revealing route-specific absorption and disposition patterns in captive sharks. Observations of spawning , informed by 2025 surveys in Tuscany's coastal waters, guide captive by identifying optimal substrates like gorgonian meadows for egg attachment. No large-scale commercial aquaculture exists, as efforts prioritize and population recovery over production.

References

  1. https://www.fishbase.se/summary/Scyliorhinus-stellaris
  2. https://animalia.bio/nursehound
  3. https://www.marlin.ac.uk/species/detail/77
  4. https://www.fishi-pedia.com/fishes/scyliorhinus-stellaris
  5. http://www.marinespecies.org/aphia.php?p=taxdetails&id=105815
  6. https://www.fishbase.se/summary/854
  7. https://www.mdpi.com/1422-0067/23/18/10355
  8. https://zse.pensoft.net/article/52420/
  9. https://www.biolib.cz/en/taxon/id138389/
  10. https://www.blueplanetaquarium.com/discover/animals/bull-huss/
  11. https://www.jstor.org/stable/3090565
  12. https://shark-references.com/species/view/Scyliorhinus-stellaris
  13. https://www.gbif.org/species/2418670
  14. https://onlinelibrary.wiley.com/doi/10.1111/joa.13257
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  51. https://www.veals.co.uk/bull-huss-a-how-to-catch-guide/
  52. https://fishingbooker.com/fish/nursehound-bull-huss
  53. https://www.diariodeibiza.com/ibiza/conservation-project-releases-141-sharks-balearic-waters/
  54. https://oceanfamilyfoundation.org/good-news-for-nursehound-sharks-in-mallorca/
  55. https://www.researchgate.net/publication/395947322_BOOSTING_GROWTH_ENVIRONMENTAL_ENRICHMENT%27S_IMPACT_ON_CAPTIVE-BRED_Scyliorhinus_stellaris
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