Fact-checked by Grok 2 weeks ago

Spiny dogfish

The spiny dogfish (Squalus acanthias) is a small to medium-sized shark species in the family Squalidae, distinguished by its slender, greyish-brown body reaching up to 200 cm in total length, two dorsal fins each preceded by a stout venomous spine, large eyes, and low-slung caudal fin.^[1]^[2] This aplacental viviparous species exhibits internal fertilization and a protracted gestation period of up to two years, producing litters of 2–15 pups that measure 20–30 cm at birth.^[3] It inhabits temperate and boreal coastal and offshore waters worldwide, from the surface to depths exceeding 900 m, preferring temperatures of 6–11°C and often forming large, sexually segregated schools that undertake seasonal migrations.^[4]^[2] Ecologically, it serves as both predator and prey, feeding primarily on small fishes, crustaceans, and squid, while facing intense fishing pressure that has led to global population declines, resulting in an IUCN Vulnerable status due to slow life-history traits like late maturity and low fecundity.^[5] Despite historical overexploitation, some regional stocks, such as in the Northwest Atlantic, have shown recovery following management measures like quotas.^[4]

Taxonomy and phylogeny

Taxonomic classification

The spiny dogfish, scientifically named Squalus acanthias by Carl Linnaeus in 1758, is a species of shark classified in the domain Eukarya, kingdom Animalia, phylum Chordata, subphylum Vertebrata, class Chondrichthyes, subclass Elasmobranchii, order Squaliformes, family Squalidae, genus Squalus, and species S. acanthias.^[6]^[7]^[2] This classification reflects its position among cartilaginous fishes characterized by skeletons of cartilage rather than bone, paired fins, and placoid scales.^[4]

Taxonomic Rank	Classification
Kingdom	Animalia
Phylum	Chordata
Class	Chondrichthyes
Order	Squaliformes
Family	Squalidae
Genus	Squalus
Species	S. acanthias

The genus name Squalus derives from Latin for "shark," while acanthias refers to "thorny" or "prickly," alluding to the prominent dorsal fin spines.^[1]^[7] No widely recognized synonyms exist for the nominal species, though genetic studies have identified distinct populations, such as North Pacific variants previously subsumed under S. acanthias but sometimes treated as S. suckleyi in regional contexts.^[7]^[6] The classification remains stable, with S. acanthias accepted as the valid binomial for the primarily Atlantic and Northeast Pacific form.^[9]

Evolutionary history

The spiny dogfish (Squalus acanthias) belongs to the class Chondrichthyes, cartilaginous fishes whose lineage diverged from bony vertebrate ancestors more than 400 million years ago during the Silurian-Devonian periods.^[10] Within Chondrichthyes, the order Squaliformes encompasses deep-water sharks adapted to low-light environments, with the group's fossil record beginning in the Early Cretaceous Barremian stage approximately 125 million years ago.^[11] The family Squalidae, which includes Squalus, originated no later than this period, as indicated by fossils of the stem-group taxon Protosqualus from Barremian deposits in Germany.^[12] Genus-level fossils of Squalus first appear in the Upper Cretaceous, marking early diversification among spiny dogfish-like forms.^[13] Teeth morphologically similar to those of modern S. acanthias are documented from Late Cretaceous Campanian sediments (approximately 75–72 million years ago), suggesting continuity in dental adaptations for grasping prey.^[12] However, unambiguous species-level fossils of S. acanthias are more recent, with records from Miocene strata around 11 million years ago and Early Pliocene deposits (5.3–3.6 million years ago) in the North Atlantic, indicating post-Messinian establishment in that basin.^[14] These findings align with palaeontological evidence of squaliform radiation during the Paleogene, driven by ecological opportunities in expanding deep-sea habitats following the Cretaceous-Paleogene extinction.^[15] Molecular phylogeography reveals a Pacific origin for S. acanthias populations, with the North Pacific lineage diverging from Atlantic and southern Pacific groups through vicariance across the equatorial Pacific, estimated at 5.9–14.9 million years ago based on mitochondrial ND2 sequences and microsatellites.^[14] This deep split (>7.8 million years ago) corresponds to Miocene tectonic and oceanographic barriers, such as equatorial upwelling intensification, while recent gene flow has been limited in the Atlantic.^[14] North Atlantic colonization likely occurred via southern dispersal routes rather than trans-Arctic migration, reconciling fossil appearances with genetic patterns of low divergence between Atlantic and South Pacific clades.^[16]

Physical description

Morphology and anatomy

The spiny dogfish exhibits a slender, fusiform body adapted for agile swimming, featuring a pointed snout, large eyes positioned dorsally for enhanced binocular vision, and five external gill slits on each side.^[1] ^[17] Spiracles are present posterior to the eyes, facilitating supplementary water intake for gill respiration during feeding or rest.^[18] The body is covered in placoid scales, or dermal denticles, which are tooth-like structures composed of dentin and enameloid, oriented posteriorly to minimize hydrodynamic drag and protect against abrasion.^[19] ^[20] Coloration consists of grayish-brown dorsal surfaces often marked with white spots, transitioning to pale ventral areas for crypsis against oceanic backgrounds.^[1] ^[17] The pectoral fins are broad and triangular, aiding in lift and maneuverability, while the pelvic fins are smaller and positioned ventrally. Two dorsal fins are present, each preceded by a stout, ungrooved spine that can erect defensively; these spines are associated with mild venom glands at their bases, capable of inflicting painful, inflammatory wounds upon contact.^[17] ^[21] ^[22] An anal fin is absent, and the caudal fin is heterocercal, with an enlarged upper lobe contributing to thrust and upward lift during propulsion.^[23] ^[24] Internally, the endoskeleton is entirely cartilaginous, lacking ossification and providing flexibility while encasing vital organs.^[25] Buoyancy is maintained without a swim bladder, relying instead on a large, lipid-rich liver that constitutes up to 25% of body mass and stores squalene for neutral buoyancy.^[26] ^[27] The dentition is heterodont, with upper teeth featuring oblique cusps for grasping prey and lower teeth forming sharp, blade-like edges for slicing flesh.^[26] The digestive tract includes a short esophagus leading to a J-shaped stomach for initial digestion, followed by a duodenum, a coiled valvular intestine with a spiral valve to maximize nutrient absorption surface area, and a rectum.^[28] ^[29] Associated organs encompass a triangular spleen adjacent to the stomach's posterior end, functioning in blood filtration despite its lymphatic role, and a pancreas contributing digestive enzymes via a duct to the duodenum.^[27] The gills are supported by a cartilaginous branchial basket, enabling efficient oxygen extraction from water pumped over the filaments.^[30]

Size, growth, and sexual dimorphism

The spiny dogfish (Squalus acanthias) displays marked sexual dimorphism, primarily in body size and maturation timing, with females consistently achieving greater maximum total lengths than males. In the western North Atlantic population, adult females reach up to 133 cm, while males attain a maximum of 100 cm.^[4] Newborn pups, born live after a gestation of 18-24 months, measure 20-33 cm in length, with litter sizes averaging 6 but varying with maternal size.^[1]^[4] Growth is slow and protracted, reflecting the species' long lifespan, which can exceed 75 years in some populations.^[31] Age and length data are typically derived from banding patterns in vertebral centra or dorsal fin spines, though estimates vary by methodology and region; the von Bertalanffy or Gompertz growth models are commonly applied, revealing sex-specific differences in asymptotic length (L∞) and growth coefficients (k). For instance, in the Adriatic Sea, Gompertz parameters yield L∞ values of 113 cm (k=0.18 year-1) for females and 92 cm (k=0.24 year-1) for males, indicating females approach larger sizes more gradually.^[32] Sexual maturity further underscores dimorphism, as females mature at larger sizes and older ages than males across populations. In the western North Atlantic, males reach maturity at 63-80 cm total length and 6-11 years, whereas females do so at 80-100 cm and 12-23 years.^[4] Comparable patterns appear in the Adriatic, where the size at 50% maturity (L50) is 65.9 cm (7.5 years) for females and 57.5 cm (5.5 years) for males, based on vertebral ageing.^[32] These disparities contribute to sex-segregated schooling post-maturity, with females' slower growth and delayed reproduction enhancing population resilience but increasing vulnerability to overexploitation.^[4]

Distribution and habitat

Global range

The spiny dogfish (Squalus acanthias) exhibits a cosmopolitan distribution primarily in temperate and boreal waters across multiple ocean basins, with an antitropical pattern avoiding tropical regions.^[5]^[16] It is present in the North Atlantic from Greenland and Iceland southward to the Gulf of Mexico and Argentina in the west, and from Norway and the British Isles to South Africa in the east, including the Mediterranean and Black Seas.^[1]^[7] In the Pacific Ocean, populations occur from the Bering Sea southward to Baja California in the eastern Pacific and to New Zealand in the western Pacific, encompassing coastal and shelf waters.^[1]^[33] The species is also recorded in the Indo-Pacific region, though less commonly in equatorial zones, reflecting its preference for cooler waters between approximately 40°N and 60°N latitudes in the north, and corresponding southern latitudes.^[7]^[34] Genetic studies indicate distinct populations across these basins, with limited gene flow suggesting regional management considerations despite the broad range.^[16] Occurrences are rare in polar Arctic waters but extend into subarctic zones.^[7]

Habitat preferences and migrations

The spiny dogfish (Squalus acanthias) inhabits coastal and shelf waters in temperate and subarctic regions of the North Atlantic, North Pacific, and southern oceans, primarily over continental shelves at depths from nearshore shallows to approximately 300 m, though individuals have been recorded up to 644 m.^[35] These sharks show a strong preference for cooler waters, with median temperatures around 9-10 °C and most time spent in ranges of 8-14 °C, though tolerances extend to 4.5-18.2 °C depending on season and location.^[35] ^[36] Habitat selection is heavily influenced by temperature gradients, with individuals avoiding extremes and often associating with benthic or near-bottom environments in areas of suitable thermal conditions.^[37] Migration patterns vary by region and population, with evidence of both resident behaviors and seasonal long-distance movements driven by temperature and prey availability. In the northwestern Atlantic, satellite tagging reveals that many individuals exhibit localized residency—67% in the Gulf of Maine and 73% off North Carolina—with mean depths of 27-93 m and limited north-south displacements, challenging assumptions of uniform high migratoriness; however, subsets (27-33%) undertake seasonal shifts, such as northeastward in spring or southward in autumn, often overlapping near Cape Cod.^[36] In the North Pacific, tagging studies indicate broader traversals, with some fish moving from Oregon northward to British Columbia between summer and winter, following cooler surface waters.^[38] Female spurdog in Nordic waters display seasonal habitat shifts, occupying deeper (150-200 m), colder (~8 °C) depths in winter-spring and shallower (<20 m), warmer (12-15 °C) zones in summer-autumn, alongside diel vertical migrations involving daytime descents and nocturnal ascents, particularly pronounced in colder seasons.^[35] These patterns underscore temperature as a primary driver, enabling year-round persistence in thermally stable fjords while prompting dispersal elsewhere.^[37]

Behavior and ecology

Spiny dogfish (Squalus acanthias) exhibit gregarious social behavior, forming large schools numbering in the hundreds to thousands of individuals, which are typically segregated by size, sex, or maturity stage.^[2] Schools often consist of individuals from the same size class, with immature sharks mixing sexes while mature groups are predominantly single-sex, comprising either males or females.^[1] This segregation extends temporally and spatially, as male and female schools may occupy overlapping areas but at different times, potentially minimizing intraspecific competition or predation risks.^[39] Such aggregations provide collective sensory advantages for detecting prey, as evidenced by shared detection of fish, squid, and ctenophores in school stomach contents.^[40] Schooling influences behavioral responses, including elevated thresholds for fast-start escape maneuvers, where grouped individuals display longer latencies and slower C-start responses compared to solitary ones, possibly due to reduced individual vigilance needs.^[41] Dogfish are rarely observed alone and maintain these schools during seasonal migrations, traveling north-south along continental shelves.^[4]^[40] In locomotion, spiny dogfish employ steady, undulatory swimming powered by lateral body and caudal fin oscillations, characteristic of many elasmobranchs, enabling sustained cruising at moderate speeds suited to their benthic and mid-water habitats.^[42] They are described as relatively slow and inactive swimmers relative to faster shark species, with low thrust generation limiting burst performance.^[40]^[43] During yaw turns, pectoral fins move asynchronously in a drag-based manner for volitional steering, while the first dorsal fin adjusts dynamically to stabilize body pitch and roll during steady forward propulsion.^[44]^[45] Escape responses involve C-type bends, bending the body into a C-shape for rapid acceleration, though overall locomotor capabilities remain modest due to morphological constraints like a heterocercal tail and reduced muscle power.^[41]

Diet and predation

The spiny dogfish (Squalus acanthias) is an opportunistic predator whose diet varies by region, size, and prey availability. Stomach content analyses from multiple populations reveal a primary reliance on teleost fishes such as herring (Clupea spp.) and capelin (Mallotus villosus), supplemented by crustaceans including squat lobsters (Galatheidae) and shrimp.^[46]^[47] In northeastern Pacific waters, summer feeding includes small schooling fishes and euphausiids, with evidence of bottom foraging on bivalves and crabs.^[48]^[40] Ontogenetic shifts in diet occur, with juveniles under 650–700 mm total length favoring invertebrates like crustaceans, transitioning to fish-dominated diets in larger individuals.^[49] Feeding employs a combination of suction for prey capture and transport, alongside ram feeding for manipulation, facilitated by the species' protrusible jaws and specialized dentition.^[50] In the northwest Atlantic, NOAA assessments confirm smaller dogfish targeting crustaceans while adults prefer bony fishes, reflecting adaptive foraging strategies.^[4] As mesopredators, spiny dogfish face predation from larger teleosts including cod (Gadus morhua), red hake (Urophycis chuss), and goosefish (Lophius americanus), as well as conspecifics and pinnipeds.^[1] Larger sharks and cetaceans such as killer whales (Orcinus orca) also prey upon them, though documented instances are infrequent due to defensive spines and schooling behavior.^[51] Overall, natural predation pressure is low relative to commercial fishing impacts.^[52]

Reproduction and life cycle

The spiny dogfish (Squalus acanthias) exhibits ovoviviparity, in which embryos develop within eggs that hatch internally, with females giving birth to live young without a placental connection.^[4]^[53] Fertilization occurs internally, followed by a gestation period of 18 to 24 months, the longest recorded among vertebrates.^[54]^[55]^[4] This extended development aligns with the species' slow life history, contributing to low population resilience.^[3] Females typically produce litters of 6 to 15 pups, though sizes range from 1 to 20 depending on maternal length and regional populations; biennial fecundity averages 8 to 11 embryos per female due to the two-year reproductive cycle.^[46]^[32]^[56] Pups are born at lengths of 23 to 36 cm, fully formed and independent.^[55]^[57] Shortly after parturition, females ovulate and conceive again, enabling near-continuous reproductive activity every other year.^[3] Sexual maturity is reached later in females than males, with 50% maturity at approximately 78 to 100 cm total length and ages of 12 to 26 years, varying by population and growth rates.^[58]^[54]^[59] Males mature at smaller sizes, around 57 to 88 cm and 10 to 11 years.^[58]^[56] This K-selected strategy, characterized by delayed maturity, small litter sizes, and extended gestation, underscores the species' vulnerability to exploitation.^[60] The life cycle integrates slow somatic growth with infrequent reproduction; individuals may live 75 to 100 years, with females allocating resources biennially to maximize pup survival in nutrient-poor environments.^[53] Embryonic growth occurs gradually, with pups reaching 21 to 28 cm at birth in some Atlantic populations.^[32] Post-birth, juveniles grow incrementally, attaining maturity after over a decade, reinforcing population recovery times exceeding decades following perturbations.^[61]^[62]

Human interactions

Commercial exploitation

The spiny dogfish (Squalus acanthias) has been commercially exploited since the late 19th century, initially for liver oil used in industrial lubricants and later for vitamin A extraction during World War II, with peak removals of 16,876 metric tons in 1944 off the U.S. Pacific coast.^[63] By the mid-20th century, fisheries expanded to target meat, fins, and other products, driven by European demand.^[64] Primary products include meat processed into fillets or "belly flaps" for fish and chips in the United Kingdom and as smoked snacks (Schillerlocken) in Germany, with carcasses often used for fishmeal.^[57] Fins contribute to the shark fin trade, while historical uses encompassed skin for leather and oil for pharmaceuticals.^[65] Major fisheries operate in the North Atlantic, with the United States and Canada as key suppliers exporting primarily to the European Union, which absorbs over 58% of U.S. dogfish exports as of 2001 data showing 2,700 metric tons shipped from the U.S. alone.^[66] In the U.S. Atlantic, commercial landings peaked at over 22,000 metric tons in 1993, comprising mostly mature females, before declining due to management measures, with 2017 landings dropping 9% from 2016 levels amid quotas.^[67]^[68] The 2024 U.S. Atlantic commercial quota stood at 4,649 metric tons, of which approximately 82% was landed, reflecting sustained directed fishing via trawls, gillnets, and longlines.^[69]^[70] In the Pacific, exploitation remains lower-scale; U.S. West Coast landings in 2023 totaled about 226 metric tons valued at $3,700, primarily as bycatch in groundfish fisheries, though historical directed efforts targeted aggregations.^[71] Canadian Pacific fisheries date to 1870, with ongoing harvests limited by non-science-based quotas despite high abundance.^[72] New Zealand reports significant landings from trawl fisheries since the 1980s, concentrated in southern waters, contributing to global catches estimated in tens of thousands of metric tons annually in the early 2000s before regulatory constraints.^[73] Economic value derives mainly from meat exports, with EU market preferences for larger specimens fueling selective harvesting of gravid females.^[74]

Bycatch and incidental impacts

Spiny dogfish (Squalus acanthias) are commonly captured as bycatch in commercial fisheries targeting groundfish, halibut, cod, and other demersal species using trawl, gillnet, and longline gear, particularly in the North Atlantic and Pacific.^[75]^[76] In the western North Atlantic, these incidental captures occur in state waters via gillnets and longlines, as well as federal trawl operations for species like monkfish.^[75] Pacific populations face similar issues in salmon gillnet fisheries off regions such as the Kuril Islands and Kamchatka, where over 1,300 captures were documented in sampled hauls. Discard mortality represents a significant incidental impact, with trawled spiny dogfish exhibiting a 29% mortality rate within 72 hours post-capture in holding pens, comparable to untrawled controls but below broader estimates of 50% for at-sea discards.^[77] Factors exacerbating this include tow duration and intensity; heavier tows correlate with higher stress and injury levels, leading to elevated delayed mortality from barotrauma, exhaustion, and predation upon release.^[77] In gillnet fisheries, such as those in the northeast Atlantic, discarded bycatch contributes unknown but potentially substantial population-level effects due to poor local markets and at-sea disposal practices.^[78] Regulatory efforts aim to mitigate these impacts, including quota adjustments and gear modifications to reduce unintended captures, though discards persist in multispecies fisheries where spiny dogfish abundance overlaps with target stocks.^[70] In U.S. Northeast waters, frameworks like Adjustment 6 to the Spiny Dogfish Fishery Management Plan incorporate measures to minimize bycatch of protected species in dogfish-directed fisheries, indirectly addressing reciprocal incidental effects.^[79] Additionally, the species' dorsal spines can damage fishing gear and contaminate targeted catches, prompting immediate discards that amplify mortality without utilization.^[80]

Conservation and management

Population status and threats

The spiny dogfish (Squalus acanthias) is classified as Vulnerable on the IUCN Red List (version 2025-1), based on observed population declines exceeding 30% over three generations in many parts of its range, primarily driven by historical overfishing.^[81] This assessment reflects the species' low intrinsic rate of increase, with minimum population doubling times exceeding 14 years, rendering it susceptible to exploitation.^[81] In the Northeast Atlantic, populations experienced an 80% decline since 1980 and up to 95% from pre-exploitation baselines, largely due to targeted fisheries, though recent quota recommendations—22,309 tonnes for 2025 and 22,594 tonnes for 2026—indicate stabilization efforts.^[82] Conversely, the Northwest Atlantic stock has recovered substantially since quotas were imposed in the late 1990s, with the 2023 assessment confirming it is neither overfished nor experiencing overfishing, projecting stable mature biomass through 2032 under current management.^[4] In the Pacific, U.S. stocks are deemed sustainably managed, with commercial landings around 500,000 pounds in 2023, and the species remains the most abundant shark in areas like Puget Sound despite past 20th-century declines.^[71]^[83] Primary threats stem from commercial fishing pressure, exacerbated by the species' K-selected life history: females reach maturity at 12–20 years, gestation lasts 18–24 months, and litters of 2–15 pups occur biennially, limiting rebound potential in unmanaged regions.^[4] Bycatch in demersal fisheries and habitat degradation from bottom trawling and dredging further compound risks, particularly in coastal nurseries.^[84] Climate change contributes indirectly through distributional shifts—evident in northward expansions in the Salish Sea—and potential alterations in prey availability or contaminant bioaccumulation, such as mercury, amid warming oceans.^[85]^[86]

Regulatory measures and recovery

In the United States, the National Marine Fisheries Service (NMFS) declared the Atlantic spiny dogfish stock overfished in 1998, prompting the development of a joint Fishery Management Plan (FMP) by the Mid-Atlantic Fishery Management Council (MAFMC) and New England Fishery Management Council (NEFMC) in 1999, which was implemented in 2000 to end overfishing and rebuild the stock.^[57] The Atlantic States Marine Fisheries Commission (ASMFC) approved a complementary Interstate FMP in 2003, establishing coastwide commercial quotas and possession limits based on fishing mortality reference points to protect reproductively mature females, whose long gestation periods (18-24 months) make the species vulnerable to overexploitation.^[57] Quotas are allocated regionally, with northern states (Maine to Connecticut) receiving 58% and southern states the remainder; for the 2024-2025 fishing year, the total quota was set at 10,699,021 pounds, reduced to 9,338,770 pounds for 2025-2026 due to assessments indicating declining productivity, and projected to increase to 11,223,720 pounds for 2026-2027.^[57] Additional measures include trip limits, such as 7,500 pounds per day in the northern region, and recent restrictions like Addendum VII (approved February 2025), which bans overnight gillnet soaks from November to March in Maryland and Virginia waters to minimize bycatch of endangered Atlantic sturgeon, effective May 1, 2025.^[57] In the European Union, science-based regulations prohibited industrial targeted fisheries for spiny dogfish in the Northeast Atlantic by 2010, shifting landings to incidental catches only, though enforcement challenges persist due to the species' migratory nature across international boundaries.^[87] Internationally, no binding bilateral or multilateral agreements specifically target spiny dogfish management, despite calls for enhanced monitoring under frameworks like CITES, where Appendix II listing proposals have been rejected due to evidence of regional recoveries.^[65] These measures have facilitated stock recovery in the Northwest Atlantic; the 2023 ASMFC Management Track Stock Assessment determined that the species is not overfished (spawning stock biomass of 191 million pups exceeding the 188 million-pound threshold) and overfishing is not occurring (fishing mortality rate of 0.02 below the 0.0246 reference point).^[57] Historical quotas from the late 1990s onward reversed severe depletion, with biomass increases documented in assessments from 2006 onward, enabling sustainable harvests under U.S. regulations that classify the fishery as responsibly managed.^[57] However, ongoing vigilance is required, as productivity declines signal potential future adjustments to prevent reversion to overfished status.^[57]

Debates on overfishing and sustainability

The spiny dogfish fishery in the U.S. Northwest Atlantic has been cited as a success of regulatory intervention, with the stock declared overfished in 1998 and a rebuilding plan implemented in 2000, leading to biomass recovery above target levels by 2010 and no overfishing as of the 2022 assessment.^[88]^[70] However, debates persist over the reliability of stock assessments, particularly a reported fourfold increase in spawning-stock biomass from 2005 to 2009, which some researchers argue is biologically implausible given the species' slow maturation (up to 12-35 years depending on sex and region), 18-24 month gestation, and low litter sizes of 2-15 pups biennially.^[89] Critics attribute such surges to potential biases in Northeast Fisheries Science Center trawl survey data, including changes in vertical distribution or capture efficiency, rather than true population dynamics, raising questions about whether quotas adequately prevent overexploitation.^[89] In the Pacific, the British Columbia fishery achieved Marine Stewardship Council certification as the world's first sustainable shark fishery in 2011, based on healthy stocks, low bycatch, and electronic monitoring, but voluntarily withdrew certification shortly thereafter amid uncaught quotas exceeding 95% in subsequent years.^[90]^[91] The decline stemmed not from overfishing but from factors including a 2014-2016 marine heatwave ("The Blob") displacing stocks northward, shifts in fleet incentives toward higher-value species under integrated management, and processor consolidation halting dogfish lines due to low margins and complex filleting needs.^[90]^[91] Conservation advocates, emphasizing the species' K-selected traits, have leveraged such cases to argue against any directed shark fisheries, viewing certifications as greenwashing that undermine broader anti-shark-harvest campaigns, while industry representatives counter that targeted management enables sustainability without stock collapse, as evidenced by stable Pacific abundances.^[91] Additional contention arises from ecological roles, with some fishing stakeholders claiming high dogfish densities suppress recovery of groundfish stocks through predation or competition, advocating relaxed quotas or culls, a view contested by assessments showing no overfished status and calls for ecosystem-based limits to avoid rebound overexploitation. In Europe, the Northeast Atlantic stock's 2011 fishery closure due to depletion has yielded mixed recovery signals, fueling disputes over quota resumption amid variable survey indices and transboundary migration complicating assessments.^[92] These debates underscore tensions between precautionary conservation, which prioritizes life-history vulnerabilities, and evidence-based management demonstrating rebound potential under enforced limits, with peer-reviewed analyses favoring the latter for this species when data-driven.^[91]^[88]

References

[1]
Spiny Dogfish – Discover Fishes - Florida Museum of Natural History
Feb 12, 2025 · This long, slender dogfish has a pointed snout, large eyes, and spines in front of its two dorsal fins. It is a brownish slate color, fading to a pale ...Conservation · Habitat · Biology<|separator|>
[2]
Squalus acanthias (Grayfish) | INFORMATION - Animal Diversity Web
Spiny dogfish exist in an oceanic environment of depths from the surface to 400 fathoms or more. They prefer a temperature range of 6-11 degrees centregade ...
[3]
Life-history traits of the spiny dogfish Squalus acanthias in ... - Nature
Oct 4, 2019 · The spiny dogfish is an aplacental viviparous species, with a long gestation, estimated up to two years. The main aim of this study is to ...
[4]
Atlantic Spiny Dogfish - NOAA Fisheries
Spiny dogfish live inshore and offshore, usually near the bottom but also in mid-water and at the surface. · They swim in large schools and migrate seasonally ...
[5]
(PDF) Squalus acanthias. The IUCN Red List of Threatened Species ...
Apr 27, 2021 · Squalus acanthias has a cosmopolitan distribution and was once considered to be the most abundant shark species in the world (Compagno 1984).
[6]
World Register of Marine Species - Squalus acanthias Linnaeus, 1758
Jan 15, 2008 · Animalia (Kingdom) ; Chordata (Phylum) ; Vertebrata (Subphylum) ; Gnathostomata (Infraphylum) ; Chondrichthyes (Parvphylum) ...
[7]
https://www.fishbase.se/summary/Squalus-acanthias
[8]
Squalus acanthias | NatureServe Explorer
Phylum: Craniata ; Class: Chondrichthyes ; Order: Squaliformes ; Family: Squalidae ; Genus: Squalus.
[9]
Squalus acanthias - Shark-References
Squalus acanthias. Linnaeus, 1758. Piked dogfish. Classification: Elasmobranchii Squaliformes Squalidae. Reference of the original description.
[10]
Dogfish - an overview | ScienceDirect Topics
The spiny dogfish shark—Squalus acanthias—belongs to Chondrichthyes, which first appeared in the Silurian Period and is among the earliest to branch off from ...<|separator|>
[11]
Of teeth and trees: A fossil tip‐dating approach to infer divergence ...
The fossil record of Squaliformes comprises mostly isolated teeth and dates back to the Early Cretaceous with the emergence of the Squalidae in the Barremian ( ...
[12]
[PDF] 2. Fossil Record and Origin of Squaliform Sharks
Squaliform shark fossil record is mainly isolated teeth, dating back to the Barremian (Early Cretaceous), ca. 125 million years ago. Complete skeletons are ...<|control11|><|separator|>
[13]
Squalus - ELASMO.COM Fossil Genera
The Fossil Record. Cappetta (1987) notes that this genus has been reported from the Upper Cretaceous of Belgium, Lower Eocene of the USSR, Oligocene of Oregon & ...<|control11|><|separator|>
[14]
[PDF] Global population structure of the spiny dogfish Squalus acanthias ...
The clear break in both genetic diversity and life history strategies found for fish on either side of the Pacific equator, and the large estimate of time since ...
[15]
Of teeth and trees: A fossil tip‐dating approach to infer divergence ...
Aug 2, 2018 · Of teeth and trees: A fossil tip-dating approach to infer divergence times of extinct and extant squaliform sharks. Christina K. Flammensbeck ...
[16]
Global population structure of the spiny dogfish Squalus acanthias ...
Mar 22, 2010 · A low level of genetic divergence was found among collections from the Atlantic and South Pacific basins, whereas a high level of genetic ...
[17]
Piked Dogfishes, Squalus acanthias - MarineBio Conservation Society
Piked dogfish are slim sharks with narrow, pointed snouts and characteristic white spots. They have two dorsal fins with ungrooved large spines.
[18]
Species: Squalus acanthias, Pike Dogfish Shark, Spiny Dogfish ...
... gill slits, without nictitating membrane; moderate sized spiracles just behind eyes; nasal flaps short, slender, not reaching mouth, with a minute or no ...
[19]
Fluorescence Digital Image Gallery - Dogfish Shark Placoid Scales
Spiny dogfishes feature two spines ... The bodies of dogfishes, like all sharks, are externally lined with placoid scales, also known as dermal denticles.
[20]
Close up of dermal denticles or placoid scales on skin of shark ...
Close up of dermal denticles or placoid scales on skin of shark. Keeled spines on scales reduce hydrodynamic drag . Spiny dogfish (Squalus acanthias, Squalidae) ...
[21]
Dogfish Shark | Online Learning Center | Aquarium of the Pacific
Oct 25, 2024 · Dogfish have venomous spines in front of each dorsal fin to protect them from predators like larger sharks and seals. Dogfish are also ...
[22]
Spiny Dogfish - New Jersey Scuba Diving
Of more concern are the two mildly poisonous spines on the back, with which the shark will lash out to defend itself if necessary. They are graceful sinuous ...Missing: venomous | Show results with:venomous
[23]
Ontogenetic Scaling of Caudal Fin Shape in Squalus acanthias ...
Jun 25, 2010 · The shark heterocercal caudal fin and its contribution to locomotion are of interest to biologists and paleontologists.
[24]
Shark, Spiny Dogfish - Marine Life Database
The caudal fin has asymmetrical lobes, forming a heterocercal tail. The species name acanthias refers to the shark's two spines. These are used defensively. If ...
[25]
Squalus acanthias
Being a member of the Class Chondricthyes suggest that the entire body skeleton is formed of cartilage. This provides protection for internal organs as well ...
[26]
Squalus acanthias - an overview | ScienceDirect Topics
Squalus acanthias, commonly known as the pike dogfish, is a medium-sized shark species that has been widely used as a model organism and subject of dissection, ...
[27]
[PDF] Sharks and the dogfish - Mayfield City Schools
Spleen - Near the posterior end of the stomach is the triangular-shaped spleen. Although not a part of the digestive system but the lymphatic system, it is ...
[28]
Activity 2: Shark Digestive Anatomy
Although a part the Iymphatic system, the spleen is closely associated with the digestive organs in all vertebrates. The valvular intestine is the second ...Missing: skeletal | Show results with:skeletal
[29]
Digestive System of the Dogfish Shark
The spiral valve allows the food to be completely absorbed and digested. The more food that can be absorbed, the less a shark has to eat.Missing: spiny | Show results with:spiny
[30]
Branchial basket of the dogfish Squalus acanthias - Anatomy To You
Jan 4, 2016 · The branchial basket is a cartilagenous structure which supports the gills (around the fine branches at either side). Image courtesy of RVC.
[31]
Squalus acanthias, Piked dogfish : fisheries, gamefish - FishBase
IUCN Red List Status (Ref. 130435: Version 2025-1). Vulnerable (VU) (A2bd); ... 120179): Very Low, minimum population doubling time more than 14 years (rm ...
[32]
Life-history traits of the spiny dogfish Squalus acanthias in the ...
Oct 4, 2019 · The size at sexual maturity (L50) was 659 mm for females and 575 mm for males, corresponding to 7.5 and 5.5 years of age (A50), respectively.Missing: peer- | Show results with:peer-
[33]
[PDF] 11 Spiny Dogfish, Squalus acanthias - CA.gov
In the eastern North Pacific, the geographical range of the spiny dogfish extends from the Gulf of Alaska southward to San Martin Island (southern Baja ...
[34]
Spiny dogfish
Nov 23, 2018 · Range. This shark is present in all of the worlds temperate oceans It ranges throughout the coastal waters of the Atlantic and Pacific oceans.
[35]
Seasonal habitat use and diel vertical migration in female spurdog ...
Sep 6, 2024 · To investigate seasonal variations in fine-scale niche use and vertical movement patterns in female spurdog, we used archival data from 19 pregnant individuals.
[36]
The Use of Satellite Tags to Redefine Movement Patterns of Spiny ...
Spiny dogfish (Squalus acanthias) are assumed to be a highly migratory species, making habitual north-south migrations throughout their northwestern Atlantic ...
[37]
Fine-scale residency and temperature-driven habitat selection in a ...
Dec 11, 2024 · McMillan D, Morse W (1999) Essential fish habitat source document: spiny dogfish, Squalus acanthias, life history and habitat characteristics.
[38]
[PDF] Migration patterns of spiny dogfish (Squalus acanthias) in the North ...
He concluded that some individuals may traverse the full commercial range of the species (Oregon to northern British Columbia) be- tween summer and winter, but ...Missing: depth temperature preferences
[39]
Sexual segregation of spiny dogfish (Squalus acanthias) off the ...
Schools of males and females can occupy the same areas, but at different times, causing spatial and temporal segregation within the stock (Burgess, 2002, ...
[40]
[PDF] Spiny Dogfish, Squalus acanthias, Life History and Habitat ...
Spiny dogfish have a long life, late maturation, a long gestation period, and low fecundity.Missing: anatomical | Show results with:anatomical
[41]
Escape manoeuvres in the spiny dogfish (Squalus acanthias)
Jun 1, 2004 · ... schooling may raise the threshold for initiation of fast escape responses, inducing longer latencies and slower responses that are more ...
[42]
Imitation of the body/caudal fin undulatory swimming of a spiny ...
May 12, 2015 · Undulatory swimming is generated by alternately coordinated sequential contractions of muscle segments along both sides of the fish. These ...
[43]
[PDF] Escape manoeuvres in the spiny dogfish (Squalus acanthias)
The locomotor performance observed in dogfish is consistent with their morphological characteristics: (1) low locomotor performance associated with low thrust.
[44]
Three-dimensional movements of the pectoral fin during yaw turns in ...
Based on these findings, we propose that Pacific spiny dogfish uses drag-based turning during volitional swimming. Post-mortem muscle stimulation revealed ...
[45]
Dorsal fin function in spiny dogfish during steady swimming - Maia
Oct 26, 2015 · This study provides evidence that spiny dogfish control movements of the first dorsal fin during steady swimming to stabilize body position. In ...
[46]
Age, Growth, Reproduction and Feeding of the Spurdog (Squalus ...
The estimated von Bertalanffy growth parameters were: W∞=12021 (g), L∞=157 (cm), K=0·12 (year−1) and t0=−1·30 (year). The size at first maturity was 82 cm for ...
[47]
Diet of spiny dogfish, Squalus acanthias Linnaeus, on the east coast ...
The major dietary components based on occurrence were 60% crustaceans and 15% fish. The principal food items were the post-larval phase of the squat lobster, ...Missing: sources | Show results with:sources
[48]
[PDF] 3. Summer Distribution and Feeding of Spiny Dogfish off the ...
—Our understanding of the spiny dogfish Squalus acanthias of the northeastern Pacific is based almost exclusively on nearshore populations from enclosed regions ...
[49]
Food and feeding habits of the spiny dogfish Squalus acanthias ...
The dogfish diet also shifted from an invertebrate-based to a teleost fish-based diet between 650-700 mm TL. Atlantic menhaden, (Brevoortia tyrannus) and ...Missing: scientific | Show results with:scientific
[50]
Conservation and variation in the feeding mechanism of the spiny ...
In this study, Squalus acanthias used both suction and ram behaviors to capture and manipulate prey, while only suction was used to transport prey.Missing: peer- reviewed
[51]
Spiny Dogfish Fish Facts - Squalus acanthias - A-Z Animals
Aug 24, 2025 · Spiny Dogfish ; Class: Chondrichthyes ; Order: Squaliformes ; Family: Squalidae ; Genus: Squalus ; Scientific Name: Squalus acanthias.
[52]
[PDF] Spiny Dogfish (Squalus acanthias) - Species at risk public registry
Spiny Dogfish (Squalus acanthias Linnaeus 1758) belongs to the order Squaliformes and the family Squalidae.
[53]
Spiny dogfish - Squalus acanthias - Shark Research Institute
May live 75 to 100 years. Reproduction – Aplacental viviparous, with an 18 to 24 month gestation period before giving birth. Litters average up to 20 pups.
[54]
[PDF] Reproduction of female spiny dogfish, Squalus acanthias, in the ...
The spiny dogfish (Squalus acanthias) longest gestation periods of any living is a relatively small shark with a char- vertebrate (up to 24 months) (Ketchen ...
[55]
Reproduction Summary - Squalus acanthias - FishBase
Gestation period of 18 to 24 months, longest known of all chondrichthyans (Ref. 26346). Size at birth 18-30 cm (Ref. 26346). In the northeast Atlantic, pups are ...
[56]
Maturity and Fecundity of Spiny Dogfish (Squalus acanthias L., 1758 ...
Age and length at 50% maturity were 10.49 years and 87.57 cm for males, and 11.99 years and 102.97 cm for females, respectively. Mean biennial fecundity was 19 ...
[57]
Spiny Dogfish - Atlantic States Marine Fisheries Commission
After an 18 to 24 month gestation period, pups are released live and fully formed at about 14 inches.
[58]
Growth and Reproduction in Spiny Dogfish Squalus Acanthias L ...
Nov 6, 2010 · Fifty per cent maturity was estimated at 57.5 cm in males and 78.2 cm in females, and fecundity was positively correlated with female size.
[59]
Size at Maturity, Fecundity, and Embryonic Growth of the Spiny ...
Females in the North Pacific mature at an average length of 92–100 cm depending on region, as compared to 77–82 cm in the North Atlantic. Males likewise mature ...
[60]
Reproductive and population parameters of spiny dogfish Squalus ...
Mar 28, 2016 · The results indicate that S. acanthias is susceptible to fishing pressure on account of its length at maturity, extended reproductive cycles and ...
[61]
Age and length at maturity of the female spiny dogfish,Squalus ...
The median age at maturity for females was 35.5 years with 95% confidence limits between 35.0 and 35.9 years. It was found that slower growing dogfish tended to ...
[62]
[PDF] Enhance International Shark Conservation
Spiny dogfish are exceptionally vulnerable to overfishing and long lasting depletion due to their slow growth, late maturity, and small litters. Female dogfish ...
[63]
[PDF] Status of the Pacific Spiny Dogfish shark resource off the continental ...
During the vitamin A fishery, removals averaged around 6,821mt per year reaching their peak of 16,876 mt in 1944.
[64]
Pacific spiny dogfish research
Dec 19, 2016 · As early as 1870, spiny dogfish were fished commercially and spiny dogfish liver and body oil was used extensively for industrial lubricants and ...
[65]
[PDF] p. 1 AC20 Inf. 22 Conservation and Management Status of Spiny ...
Other scenarios carried out in this assessment revealed population status as low as 2% of K. Page 3. AC20 Inf. 22 – p. 3. Figure 1. Squalus acanthias catches in ...
[66]
The international trade and fishery management of spiny dogfish
The major demand for its meat is from the European Union (EU) market, with the US and Canada as its two major contributors.
[67]
Implications of recent increases in catches on the dynamics of ...
Dec 15, 1998 · US commercial landings of spiny dogfish have increased five-fold since 1987 to over 22 000 mt in 1993. Over 95% of the landings consist of ...
[68]
[PDF] Update on the Status of Spiny Dogfish in 2018 and Projected ...
Aug 31, 2018 · The spiny dogfish population is not overfished, with a SSB estimate of 106.8 kt. US commercial landings decreased by 9% from 2016 to 2017. ...
[69]
Spiny Dogfish Accountability Measures (AMs) and 2026
Jun 25, 2025 · The final adjusted 2024 commercial quota was 4,649 MT (10,249,260 lbs). Some other MAFMC-managed fisheries, such as summer flounder, have ...
[70]
[PDF] 2025 Spiny Dogfish Fishery Information Document
Aug 15, 2025 · The 2024 fishing year quota was about 10.2 million pounds (15% lower than. 2023's quota). About 82% of the 2024 quota was landed. • The ...Missing: industry | Show results with:industry
[71]
Pacific Spiny Dogfish | NOAA Fisheries
Pacific spiny dogfish are found from the Bering Sea to Baja California. They are more common off the U.S. West Coast and British Columbia than in the Gulf of ...Missing: distribution | Show results with:distribution
[72]
Spiny dogfish research
Jan 29, 2018 · The spiny dogfish is a long-lived, slow growing fish. The few previous studies based on spine growth suggested a growth rate of about 3.5 cm per year.
[73]
[PDF] SPINY DOGFISH (SPD) 1. FISHERY SUMMARY
1.1. Commercial fisheries. Spiny dogfish are found throughout the southern half of New Zealand, extending to East Cape and.
[74]
[PDF] p. 1 CoP14 Prop. 16 CONVENTION ON INTERNATIONAL TRADE ...
Squalus acanthias meat is highly valued, particularly in Europe, with European market demand driving fisheries that preferentially target aggregations of mature ...
[75]
Atlantic Spiny Dogfish: Management - NOAA Fisheries
Fishermen must have a permit to harvest spiny dogfish. Annual catch limits and a commercial quota are set. Trip limits used to control the catch rate. The ...
[76]
Reducing elasmobranch bycatch: Laboratory investigation of rare ...
Spiny dogfish (Squalus acanthius) comprises a significant unwanted bycatch on demersal longlines set for halibut and cod in shelf waters of the east and ...
[77]
The estimated short-term discard mortality of a trawled ...
Trawled spiny dogfish had a 29% 72-hour mortality rate in pens, similar to control groups, but lower than the estimated 50% discard rate. Heavier tows increase ...
[78]
Recent incidental catch of sharks in gillnet fisheries of ...
The majority of these catches are discarded at sea owing to poor local markets; the impact of these catches on the species' populations is unknown at present ( ...
[79]
Framework Adjustment 6 to the Spiny Dogfish Fishery Management ...
Dec 18, 2024 · This action is necessary to minimize bycatch of Atlantic sturgeon in the monkfish and spiny dogfish fisheries to the extent practicable and ...
[80]
Like finding a Pacific spiny dogfish in a haystack
Nov 28, 2024 · This bycatch is certainly problematic for the fishermen because it displaces their desired catch. Plus, as the name “spiny dogfish” suggests, ...
[81]
Squalus acanthias, Piked dogfish : fisheries, gamefish - FishBase
Elasmobranchii (sharks and rays) > Squaliformes (Sleeper and dogfish sharks) > Squalidae (Dogfish sharks) Etymology: Squalus: Genus name from Latin ...
[82]
Experience of spiny dogfish Squalus acanthias interactions with ...
Jun 12, 2025 · Once inside the cages, they are observed to display a calm swimming pattern and typically feed on dead fish. There have been isolated reports of ...Missing: habits | Show results with:habits
[83]
Spiny dogfish on the move | Encyclopedia of Puget Sound
Oct 27, 2024 · Commercial fishers seeking more valuable fish along the coast frequently catch and discard dogfish as unwanted bycatch. Since 2015, harvest ...
[84]
Spiny Dogfish (Squalus acanthias) - State of The Coast
Globally, spiny dogfish are classed as vulnerable (IUCN Red List, 2018). In the Northeast Atlantic however, they are now considered recovered to the extent that ...
[85]
Spiny dogfish on the move - Salish Current
Nov 12, 2024 · The small size of dogfish litters, uncertainty about their reproductive cycles, and ongoing changes in habitat and climate have raised concerns ...Missing: threats | Show results with:threats
[86]
Climate change likely to increase human exposure to toxic ...
Aug 7, 2019 · Environmental factors, such as rising sea temperatures and over-fishing, impact levels of mercury in fish.
[87]
[PDF] Squalus acanthias, Spiny Dogfish - ResearchGate
The Spiny Dogfish (Squalus acanthias) is a medium-sized (to 200 cm total length) shark known from a global distribution in boreal and temperate waters in all ...
[88]
Atlantic Spiny Dogfish Benefits from Sustainable Shark Management
Aug 1, 2019 · Population Assessments · Resources ... Scientists will re-evaluate the fishery status in 2021 during the next spiny dogfish stock assessment.
[89]
Dismissing dogma? What do we really know about the spiny dogfish ...
Feb 6, 2024 · The status of the spiny dogfish (Squalus acanthias) stock in the US portion of the Northwest Atlantic has become a contentious issue.<|separator|>
[90]
What happened to the world's first certified sustainable shark fishery?
Jun 26, 2023 · Spiny dogfish sharks have had a complicated history when it comes to fisheries management, going from hated pest to crashed fishery to ...
[91]
“A prized Pacific shark”: the rise and fall (and ... - Wiley Online Library
May 30, 2023 · In the midst of debates over the existence of sustainable shark fisheries, British Columbia's (BC) fishery for Pacific spiny dogfish (Squalus ...
[92]
Survivability of spurdog (Squalus acanthias) in an inshore otter trawl ...
Spurdog (Squalus acanthias) was previously fished by European Union (EU) vessels, but the fishery closed in 2011 due to poor stock status. Following positive ...Missing: controversies | Show results with:controversies