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Lifespan, longevity, and ageing

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Maximum longevity: 75 years (wild) Observations: These animals take about 20 years to reach sexual maturity and are extremely long-lived (Das 1994). Although their exact longevity is unknown, some estimates indicate these animals can live up to 50-75 years (Cailliet et al. 2001).
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Conservation Status

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No special status.

US Federal List: no special status

CITES: no special status

IUCN Red List of Threatened Species: endangered

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Street, R. 2002. "Squalus acanthias" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Squalus_acanthias.html
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Robin Street, University of Michigan-Ann Arbor
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Morphology

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The spiny dogfish can be recognized by its two dorsal fins, each with a spine; second dorsal is smaller than the first. Pectoral fins posses curved margins and rounded free rear tips. These sharks have narrow anterior nasal flaps. The teeth are oblique and smooth with a notch on the outer margin. Color is slate grey to brown above (often with scattered small white spots) and light grey to pure white on the belly. An albino was reported in Norwegian waters.

Range mass: 3.1 to 9.1 kg.

Other Physical Features: bilateral symmetry

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Street, R. 2002. "Squalus acanthias" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Squalus_acanthias.html
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Robin Street, University of Michigan-Ann Arbor
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Life Expectancy

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Average lifespan
Status: wild:
60.0 years.

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Street, R. 2002. "Squalus acanthias" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Squalus_acanthias.html
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Robin Street, University of Michigan-Ann Arbor
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Habitat

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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.

Aquatic Biomes: benthic ; coastal

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Street, R. 2002. "Squalus acanthias" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Squalus_acanthias.html
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Robin Street, University of Michigan-Ann Arbor
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Distribution

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The spiny dogfish inhabits the temperate and subarctic latitudes of the North Atlantic and North Pacific oceans. Specimens have been found in the Black and Mediterranean seas.

Biogeographic Regions: arctic ocean (Native ); atlantic ocean (Native ); pacific ocean (Native )

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Street, R. 2002. "Squalus acanthias" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Squalus_acanthias.html
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Robin Street, University of Michigan-Ann Arbor
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Trophic Strategy

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Spiny dogfish prey on bony fishes, smaller sharks, octopuses, squid, crabs, and eggcases of sharks and chimaeras.

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Street, R. 2002. "Squalus acanthias" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Squalus_acanthias.html
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Robin Street, University of Michigan-Ann Arbor
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Benefits

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This species is used for its oil and as fish meal. It is also a popular labratory animal. In some areas (Europe more than the U.S.), it is a popular food fish.

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Street, R. 2002. "Squalus acanthias" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Squalus_acanthias.html
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Robin Street, University of Michigan-Ann Arbor
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Benefits

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This fish causes tremendous damage when packs of them become entangled in commercial fishing nets.

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Street, R. 2002. "Squalus acanthias" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Squalus_acanthias.html
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Robin Street, University of Michigan-Ann Arbor
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Reproduction

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This shark is ovoviviparous. Males reach maturity between 80-100cm in length or at around 11 years of age; females mature at100-124 cm or in 18-21 years. Mating takes place during the winter months. As soon as the eggs are fertilized, the female secretes a thin, horny, transparent shell around them. The shells suround several eggs at once and are called candles. Gestation lasts between 22-24 months. Litters range between 2-11 pups and are between 20-30 cm at birth. They live for as long as 25-30 years.

Average age at sexual or reproductive maturity (male)
Sex: male:
3163 days.

Average age at sexual or reproductive maturity (female)
Sex: female:
7668 days.

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Street, R. 2002. "Squalus acanthias" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Squalus_acanthias.html
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Biology

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Said to be the most abundant living shark, the spiny dogfish is a slow, inactive swimmer and forms massive feeding aggregations of thousands of individuals. Tending to be same-sex and same-size shoals, they prey on shoals of bony fish, as well as octopuses, smaller sharks, squid, crabs and shark egg cases (3). They are highly migratory, moving towards the equatorial side of their range during winter (2). With estimates of between 20 years and 75 years, the spiny dogfish is thought to be a very long-lived fish that matures late and reproduces slowly, with gestation lasting two years – the longest of any vertebrate (1) (2) (3). An ovoviviparous species, spiny dogfish develop in eggs within the female, and gain nourishment from their yolk sacs, After four to six months, these eggs are shed, but the embryos continue to develop inside the female, still living off the yolk sac attached to their abdomens. Finally, after another 18 to 20 months of development, six to seven live young are born, measuring 20 to 33 centimetres. Despite possessing venom-delivering spines on each of its two dorsal fins, the spiny dogfish is eaten by cod, red hake, goosefish, other spiny dogfish, larger sharks, seals, and orcas (2).
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Conservation

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These sharks are especially vulnerable to over-fishing as they are slow to mature, have a very long gestation period, and produce very few young. Demand for these fish is highest in Europe, but they were commonly caught in American waters for export to Europe. The American National Marine Fisheries Services closed American waters to dogfish fishing in July 2003 on evidence that the population was on the edge of collapse (2). WWF have created a suggested recovery plan that aims to reduce exploitation to very low rates to allow recovery, and to reduce by-catch by avoiding areas with spiny dogfish. Monitoring and research on the spatial and seasonal patterns of distribution are also planned (6).
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Description

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The common name 'dogfish' was given by fisherman to small sharks due to their habit of hunting shoals of fish in 'packs' (3). The spiny dogfish is a small, slim fish with a narrow, pointed snout and distinctive white spots (4). The back is slate grey to brown and the belly is pale grey to white. It has two dorsal fins, the first of which is smaller (3). They both have a spine which can inject venom causing strong pain lasting for several hours, and very occasionally death in humans (4). The pectoral fins are curved and have rounded tips (3).
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Habitat

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Found from the surface to a depth of 900 metres, the spiny dogfish is thought to tolerate in temperatures of between 7 and 15 degrees Celsius.
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Range

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Distributed along coastlines, the spiny dogfish is found in the western Atlantic, eastern Atlantic, western Pacific and eastern Pacific, as well as the Mediterranean Sea and the Black Sea (4).
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Status

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Classified as Vulnerable (VU) on the IUCN Red List.
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Threats

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The spiny dogfish is considered to be the most abundant living shark, yet two particular subpopulations in the northwest and northeast Atlantic Ocean are considered to be at risk due to massive fishing pressure. This shark is caught for food, liver oil, and used to make sand paper, vitamins, leather, fertiliser, pet food and fish meal (1) (4). At a time of peak abundance between 1900 and 1910, it is estimated that up to 27 million spiny dogfish were caught off the Massachusetts coast every year (5).
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Brief Summary

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Spurdogs are regularly caught by fishermen in the North Sea. In October 2008, the fishing vessel TX68 caught many spurdogs in its net in just one fishing attempt. The crew filled more than 60 crates just with this shark. This shark is named after the characteristic spines, or spurs, on the front of its dorsal fins, which are defense weapons. This creates a problem for fishermen when trying to remove them from their nets. Otherwise, spurdogs are harmless.
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Benefits

provided by FAO species catalogs
This is one of the most important sharks for fisheries because of its abundance in colder waters, utilization in various fisheries, and damage it does to gear and catches of other fishes. Catches of Squalus acanthias reached a peak in 1972 (73,500 t) then declined but in the last decade they have stabilized in a range between 36,000 and 51,000 t. Most of the catches reported to FAO have come firstly from area 27 (Northeast Atlantic) and then from area 21 (Northwest Atlantic) but in 1995 and 1996 catches taken in area 21 have exceeded those from area 27. Minor catches have been reported from Northeast Pacific (maximum 5,314 t in 1988) and Mediterranean and Black Sea (peaking at 1,789 t in 1988 but only 143 t in 1996).The total catch reported for this species to FAO for 1999 was 22 756 t. The countries with the largest catches were Canada (5 536 t) and Norway (1 461 t). It is captured primarily in bottom trawls and with longlines and handlines, but also commonly with gill nets seines, fish traps, and other gear; it is also readily taken by rod and reel . It is utilized fresh, fresh-frozen, smoked, boiled-marinated, dried-salted, and in the form of fish cakes for human consumption. It is also used for liver oil, fish meal, pet food, fertilizer and leather. There are and have been numerous fisheries for picked dogfish around the world. There have been several cases of overexploitation of this species, which is the most abundant shark in the world (Compagno 1984), but the enormous abundance of the stocks usually prevents a total collapse and the fisheries normally stop for economic reasons. A combination of overexploitation, shifting markets and economic constraints has caused almost all picked dogfish fisheries to undergo declines. In most of these fisheries, the larger females are primarily targeted and this usually leads to overexploitation of the female stock while the male stock might be still at a healthy level (Holden 1968, Bonfil in press b). In European waters (mainly the North and Irish Seas), picked dogfish has been fished since the beginning of this century mainly by British and Norwegian fishermen, but later also by the French and the Irish (Bonfil 1994). Total catches were on average of 3,000 t/y before the 1930s, rose to over 12,000 t/y by 1937 mainly due to increases in the Norwegian fishery and then varied between 20,000-42,000 t/y in the period 1951-70 (Holden 1977). Holden (1968) considered that the female part of the Scottish-Norwegian stock of picked dogfish was being overfished in the late 1960s, but no stock assessments are known for any of the European fisheries for picked dogfish. Holden (1977) and Myklevoll (1989d) illustrate many of the factors that have caused the variations in the catches of picked dogfish in the British and Norwegian fisheries. These include among others, differences in size and presentation of the product due to different capture methods, competitiveness of prices, limits on market demand, and the existence of alternative and more profitable fisheries. The British Columbia picked dogfish fishery, which dates at least from the mid-19th century, has undergone also several booms and busts due mostly to economic factors (Ketchen 1986, Bonfil in press b). However, Ketchen (1986) reported a few signs of overexploitation for this stock during the heavy and uncontrolled vitamin A fishery, which might have brought about a large decline in the biomass of some local picked dogfish stocks. With that exception, the picked dogfish in the Northeastern Pacific has always remained at healthy levels. In Irish waters, a fishery for picked dogfish developed rapidly during the 1980s but decreasing catches in the NW fishing grounds shifted the effort towards the SW. This, together with the disappearance of larger females from the catches caused the concern of the Irish Department of the Marine (Rose 1996). In the western North Atlantic an increase in biomass of local picked dogfish stocks and a strong decline in more valuable groundfish stocks spurred an increase in dogfish exploitation mainly by US fishermen. Total dogfish catches rose from some 5,000 t/y in the mid-1980s to 22,500 t in 1993 (Rago et al . 1994). Most of this production of picked dogfish is exported to several markets in Europe for human consumption. The recreational catch of picked dogfish in this region is only about 8% of the commercial catch but large amounts of discards are suspected to happen in the size-discriminating commercial fishery and could add up to some 14,000 t/y (Rago et al. 1994). Fishable biomass of the NW Atlantic stock is estimated to have increased six-fold in the period 1968-89 to a peak of 300,000 t and then declined due to exploitation to less than 150,000 t (ICES 1998). A pronounced decrease in mean length of females has also been detected in this fishery where recently over 75% of the landed females were immature. The US Atlantic fishery is reported to have been recently declared as overexploited and a management plan is currently under preparation (ICES 1998). Conservation Status : Smith et al. (1998) found that the picked dogfish has the lowest intrinsic rebound potential of the 26 shark species they analysed. This is due to the extreme biological characteristics of this species, which is very slow growing and attains sexual maturity after many years. The abundance of picked dogfish is certainly very high in general but the declines in several heavily exploited stocks signal the high likelihood of impacting individual stocks if not managed properly. This species seems to be a good candidate for Lower Risk/Least Concern at the world level and Lower Risk/Conservation Dependent in the NE and NW Atlantic where it is heavily fished and still unmanaged.
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FAO species catalogue Vol.4. Sharks of the world. An Annotated and Illustrated Catalogue of Shark Species Known to Date Part 1 - Hexanchiformes to Lamniformes. Compagno, L.J.V. 1984. FAO Fish. Synop., (125) Vol.4, Part 1
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Brief Summary

provided by FAO species catalogs
An extremely abundant, boreal to warm-temperate,inshore and offshore dogfish of continental and insular shelf waters and the upper slopes, from the surface down to the bottom but usually near the bottom; found from the intertidal down to at least 900 m.This is possibly the most abundant living shark, despite its restricted range, and the only one that supports fisheries of a size rivalling those of the more commercially important bony fishes. Bigelow & Schroeder (1948) noted that in a time of peak abundance in 1904-05 an estimated 27,000,000 dogfish were taken off the Massachusetts coast each year. The piked dogfish is probably the best-known of living sharks, particularly from a morphological, experimental and fisheries-biological viewpoint, though its ecological relationships and ethology is far less well known than some other sharks, particularly certain tropical carcharhinids and sphyrnids. Knowledge of its biology clearly reflects the concerns of fisheries and the interests of fisheries biologists, as well as its great abundance, but even with the massive corpus of information available great gaps remain in our knowledge of its biology. The literature on this shark is so enormous that only a small amount of the available information can be presented here. [more...] The dogfish forms immense feeding aggregations or packs in rich foraging grounds and may be present in thousands.Longline sets of 700 to 1500 hooks with nearly every hook bearing a dogfish have been reported from the Western North Atlantic. Dogfish often occur in schools segregated by size and sex, including those of small juveniles of both sexes in equal numbers, mature males, larger immature females, and large mature females. Mixed schools of adults have also been reported, but at best these are probably less common than segregated schools. These schools are dense and localized in a given area, and move erratically over short periods of time, possibly reflecting pursuit of schooling prey fishes. In general, males occur in shallower water than females, with the exception of large pregnant females. Pregnant females may congregate in enclosed shallow bays like San Francisco Bay in California, and drop their young there. Dogfish are also found as solitary individuals and may also associate with schools or aggregations of other temperate sharks such as the leopard shark (Triakis semifasciata ) and the brown smoothhound (Mustelus henlei ) in the Eastern North Pacific. Although the piked dogfish is often found in enclosed bays and estuaries, and can tolerate brackish water, it apparently cannot survive fresh water for more than a few hours and does not occur there. During the rainy winter and spring of California dogfish may leave San Francisco Bay and other shallow bays and estuaries as the salinity drops, but return in late spring and summer. Much has been written of the seasonal, bathymetric, and localized movements of this shark.An important correlate of dogfish movements seems to be water temperature; the sharks favour a temperature range with a minimum of 7-8°C and maximum of 12-15°C, and apparently make latitudinal and depth migrations to stay within their optimum range. Thus in the Western North Atlantic dogfish move inshore from their wintering grounds in deep water off the US Middle Atlantic and Southern States as the water warms in spring, pressing northwards along the coasts of Newfoundland and Labrador and southwards along the US Atlantic coast occasionally to Cuba. [more...] An ovoviviparous shark, with litters of 1 to 20 young. There is much regional variation in reported litter sizes that may be correlated with other factors than maternal size, but in general larger mother sharks have larger litters of fetuses that attain a larger size before birth than smaller ones. The gestation period is variously reported as 18 to 24 months, and may differ in areas. Mating of dogfish may occur in the winter. Birth in the dogfish may occur primarily during the cold months of the year, with considerable variation and with some young produced in spring and summer. The sex ratio at birth is 1:1. Young are delivered head first with a series of rhythmic contractions reminiscent of birth in mammals. Age of piked dogfish is commonly determined by counting annual growth rings on the fin spines, though wear of the spines in large dogfish may limit the usefulness of this method. This is apparently a slow-growing and maturing species, that is very long-lived. Ages at maturity may vary regionally, and has been variously reported as 10-20 years for females and 11 or more years for males. Ketchen (1975), trying a variety of methods on British Columbian dogfish estimated an average of 14 years to maturation for males and 23 years for females. Maximum age is at least 25 to 30 years, with some estimates going much higher and approaching 100 years.This shark is a powerful, voracious predator that feeds primarily on bony fishes, and is capable of dismembering rather large prey with its strong jaws and clipper-like teeth. Its bony fish prey includes herring, sardines, menhaden and other clupeids, true smelt (Osmeridae) and their eggs, hake, cod, pollock, ling, haddock and other gadoids, midshipmen, blennies, sand lances, mackerel, porgies, croakers, flatfish and sculpins. [more...] The main impact of this shark on people is economic, however: both negative, as it displaces or chases off other fishes, gets hooked or netted in gear intended for other species, damages fishing gear, and destroys hooked and netted fishes; and positive, as a fisheries species and an integral and important member of offshore and inshore marine communities. Suggestions have been made to 'control' the numbers of dogfish in the western North Atlantic, by a variety of sometimes bizarre methods, though the necessity of doing this is largely a result of prejudice against dogfish as human food and unreasoned hatred for these sharks. [more...] Apart from human beings, this shark is preyed on by a number of larger sharks, some bony fishes, seals and killer whales.
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FAO species catalogue Vol.4. Sharks of the world. An Annotated and Illustrated Catalogue of Shark Species Known to Date Part 1 - Hexanchiformes to Lamniformes. Compagno, L.J.V. 1984. FAO Fish. Synop., (125) Vol.4, Part 1
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Size

provided by FAO species catalogs
May exceptionally reach 160 cm in the eastern north Pacific, but most individuals there are smaller, and other populations apparently reach smaller maximum sizes. Size of males at maturity from 59 to 72 cm and maximum size of mature males from 83 to 100 cm; size of females at maturity from 70 to 100 cm and maximum size of mature females from 101 to 124 cm; size of young at birth 22 to 33 cm.
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FAO species catalogue Vol.4. Sharks of the world. An Annotated and Illustrated Catalogue of Shark Species Known to Date Part 1 - Hexanchiformes to Lamniformes. Compagno, L.J.V. 1984. FAO Fish. Synop., (125) Vol.4, Part 1
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Distribution

provided by FAO species catalogs
AntetropicalWestern Atlantic: Greenland and Labrador (Canada) to Florida (USA), Cuba; Uruguay and Argentina. Eastern Atlantic: Iceland and Murman Coast (Russia) to Morocco, West Sahara, Canary Islands, Mediterranean and Black Sea; Cape coast of South Africa. Western Pacific: Bering Sea to Japan, Sea of Okhots, Republic of Korea and northern China; southern Australia, New Zealand, ? Papua New Guinea. Eastern Pacific: Bering Sea to southern Baja California, possibly Gulf of California; Chile.
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FAO species catalogue Vol.4. Sharks of the world. An Annotated and Illustrated Catalogue of Shark Species Known to Date Part 1 - Hexanchiformes to Lamniformes. Compagno, L.J.V. 1984. FAO Fish. Synop., (125) Vol.4, Part 1
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Diagnostic Description

provided by FAO species catalogs
fieldmarks: Two dorsal fins with ungrooved large spines, first dorsal spine origin behind pectoral rear tips, white spots on gray sides, oblique-cusped cutting teeth in both jaws, no subterminal notch on caudal fin, no anal fin, and upper precaudal pit and lateral keels on caudal peduncle. Body fairly slender. Snout subangular, pointed, narrow, and moderately long, diagonal distance from snout tip to excurrent aperture of nostril greater than that from excurrent aperture to upper labial furrow, preoral snout about 1.2-1.3 times mouth width, preorbital snout less than twice eye length. Eyes about equidistant between snout tip and first gill slits. Nostrils nearer snout tip than mouth; anterior nasal flap with posterior secondary lobe minute or absent. Lateral trunk denticles small, tricuspidate and with deeply scalloped posterior borders in adults. Pectoral fins narrow and falcate, posterior margins slightly concave, rear tips narrowly rounded. Pelvic midbases closer to second dorsal base than to first. First dorsal spine short, much shorter than fin base and with tip falling far below apex of fin; second moderately long, about as high as fin, and less than 5% of total length; first dorsal fin more posteriorly situated, with origin over or behind pectoral free rear tips and spine origin behind tips; first dorsal low, height less than half length from origin to rear tip; second dorsal markedly smaller than first, with height less than 5% of total length; pectoral fins narrow and falcate, posterior margins slightly concave, rear tips narrowly rounded; pelvic midbases closer to second dorsal base than to first; caudal fin narrow-lobed and moderately long, with a long ventral lobe and strongly notched postventral margin. Upper precaudal pit well developed on caudal peduncle. Colour gray above, white below, usually with conspicuous white spots present on sides of body, dorsal and fins without white edges but dusky-tipped in young and plain in adults. Size moderate to large, up to 1.5 m but mostly smaller.

References

  • Bigelow, & Schroeder, (1948, 1957)
  • Fowler, (1941)
  • Garrick, (1960)
  • Jensen, (1966)
  • Ketchen, (1975)

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FAO species catalogue Vol.4. Sharks of the world. An Annotated and Illustrated Catalogue of Shark Species Known to Date Part 1 - Hexanchiformes to Lamniformes. Compagno, L.J.V. 1984. FAO Fish. Synop., (125) Vol.4, Part 1
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Diagnostic Description

provided by Fishbase
This moderately sized species is distinguished by the following set of characters: very slender body, abdomen width 7.2-9.2% TL; narrow head, width at mouth 7.9-10.2% TL; mouth width 1.7-2.2 times its horizontal prenarial length; moderately long snout, preoral length 2.2-2.5 times horizontal prenarial length, 8.5-9.8% TL; single-lobed anterior nasal flap; small dorsal fins, raked, first dorsal-fin height 1.1-1.3 times its inner margin length, second dorsal-fin height 0.7-0.9 times its inner margin length; origin of first dorsal-fin located just posterior to pectoral-fin free rear tips; exposed bases of dorsal-fin spines relatively narrow, 0.4-0.7% TL; short spine of first dorsal fin, exposed length 1.7-2.7% TL; pectoral-fin anterior margin 1.9-3.1 times its inner margin length; preventral caudal margin 1.9-2.6 times inner margin of pelvic fin; pale caudal fin with poorly demarcated, whitish margin, blackish caudal blotch at the apex of upper lobe, anterior margins of both lobes whitish in juveniles; dark caudal bar absent; dorsal and lateral surfaces of body bluish grey with an irregular array of moderately-large white spots; whitish ventrally; flank denticles tricuspid; monospondylous centra 41-45, precaudal centra 74-79, total centra 100-105 (Ref. 58446).
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Recorder
Cristina V. Garilao
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Trophic Strategy

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Common in cold waters; usually at temperatures of 6-15°C (Ref. 5951); inhabits rocky regions (Ref. 9137). A carnivore (Ref. 9137) and opportunist feeder (Ref. 43115). Feeds on fishes (mackerel, sand lance, silver hake, white hake, haddock, pollock, Atlantic salmon, menhaden, winter flounder and longhorn sculpin), cephalopods (e.g. squids), amphipods, crabs, shrimps, molluscs, ctenophores, echinoderms (e.g. sea cucumber), polychaete worms, sea anemones, jellyfish, and red, green and brown algae; herring, capelin and cod found to be important foods (Ref. 5951, 28070). Smaller individuals (
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Morphology

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Dorsal spines (total): 2; Dorsal soft rays (total): 0; Analspines: 0; Analsoft rays: 0; Vertebrae: 101 - 109
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Migration

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Oceanodromous. Migrating within oceans typically between spawning and different feeding areas, as tunas do. Migrations should be cyclical and predictable and cover more than 100 km.
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Life Cycle

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Distinct pairing with embrace (Ref. 205). Ovoviviparous, with litters of 1 to 21 young (Ref. 247, 88865). Mating probably occurs in winter. 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 born in winter, with size at birth about 26-28 cm (Ref. 88864). Sex ratio at birth is 1:1. Gravid females congregate in enclosed shallow bays to give birth (Ref. 247). The mother shark experiences a series of rhythmic contractions, just like in mammals, and the young are delivered head first. Larger older females have bigger litters with larger pups; a female with 100 cm TL carries on average 4 times as many embryos compared to a 70 cm female and the former have higher survival rates than those born to small females (Ref. 4856, 88869, 88883).
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Biology

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Possibly the most abundant living shark (Ref. 247). A demersal, inshore and offshore dogfish of the continental and insular shelf and upper slopes (Ref. 247, 11230, 119696). Usually near the bottom, but also in midwater and at the surface (Ref. 26346); occurs mainly between 10-200 m depth (Ref. 247). Males and gravid females usually found shallower than non-gravid females. Tolerates brackish water, often found in enclosed bays and estuaries. Reported to enter freshwater (Ref. 11980) but cannot survive there for more than a few hours (Ref. 247). Highly migratory species, used to be observed in large foraging schools with up to thousands of individuals, usually segregated by size and /or sex, with schools of large gravid females preferentially targeted by fisheries. Their latitudinal (north-south) and depth-related (nearshore-offshore) movements appear to be correlated with their preferred temperature (Ref. 247). Tagging experiments showed that populations in the northern North Sea and northwest Scotland made winter migrations to off Norway and summer migrations to Scotland (Ref. 88880, 88881). Transoceanic migrations recorded, but rare (Ref. 88864). Longevity in the northern Atlantic is about 35-50 years (Ref. 88882), but most live only 20-24 years (Ref. 88187). Growth is slow. At sexual maturity, males are 60-70 cm long, females 75-90 cm (Ref. 35388). Gestation period is 2 years (Ref. 36731). Ovoviviparous (Ref. 205). Feeds on a diversity of prey, ranging from comb jellyfish, squid, mackarel and herring to a wide array of benthic fishes, shrimps, crabs and even sea cucumbers (Ref. 93252). The only species of horned sharks that can inflict toxins with its tail. Detects weak electric fields generated by potential prey (Ref. 10311). Utilized for human consumption, liver oil, vitamins, sand paper, leather, fertilizer, etc. (Ref. 247, 27436). Eaten fried, broiled, and baked (Ref. 9988).
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Importance

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fisheries: commercial; gamefish: yes
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Spiny dogfish

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The spiny dogfish (Squalus acanthias), spurdog, mud shark, or piked dogfish[2] is one of the best known species of the Squalidae (dogfish) family of sharks, which is part of the Squaliformes order.[3]

While these common names may apply to several species, Squalus acanthias is distinguished by two spines (one anterior to each dorsal fin) and no anal fin. It lives in shallow waters and further offshore in most parts of the world, especially in temperate waters. Those in the northern Pacific Ocean were reevaluated in 2010 and found to constitute a separate species, now called the Pacific spiny dogfish (Squalus suckleyi).[4]

Description and behaviour

Spiny dogfish pup

The spiny dogfish has dorsal fins, no anal fin, and white spot along its back. 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 captured, the shark can arch its back to pierce its captor with spines near the dorsal fins that secrete a mild venom into its predator.[5]

This shark is known to hunt in packs that can range up into the thousands. They are aggressive hunters and have a sizable diet that can range from squid, fish, crab, jellyfish, sea cucumber, shrimp and other invertebrates.[6]

Dogfish sharks experience one of the longest gestation periods of any organism, which can last from around 18 to 24 months. During spawning season, which occurs during the colder months of winter, females can lay anywhere from 2 to 12 eggs, which develop ovoviviparously and the pups are birthed as live young, with about 5 to 6 in each litter of pups, mainly depending on the size of the female. Reproduction occurs in the winter in offshore waters, while pups are normally born in the warmer and deeper offshore waters where it is harder for humans and predators to reach them. The reproductive cycle begins when females produce several large eggs of yellow coloring, which become fertilized once they pass through the shell gland and are wrapped in what is called a "candle", or a kind of reproductive capsule. One can determine if an egg is fertilized when the blastoderm is visible. The candle passes through the rest of the reproductive tract until it reaches the uterus. Attached to the gill region of the pup is a yolk sac which provides nutrients for them as they develop, which they absorb as they grow. Even after fully absorbing the yolk sac, the pups may live in the uterus for a period of time afterwards during the gestation period.[7][8] Both sexes are greyish brown in color and are countershaded. Males are identified by a pair of pelvic fins modified as sperm-transfer organs, or "claspers". The male inserts one clasper into the female cloaca during copulation.

In females the size of ova and the state of uteri determines whether sexual maturity has been reached, while in males, clasper length and calcification is the determination factor. Many of the growth patterns show a isometric growth pattern, as the pups have very similar features to the adults. Sexual maturity does not match body size development, they mature quite earlier than one would expect. Most males reach sexual maturity at an earlier ages of around 10 years, growing to be about 60–65 cm in length. Females take a longer period of time, around 16 years, to reach sexual maturity, and can grow to about 80–84 cm (30–30 in) at that time. Some dogfish have been seen to live nearly 70 years, but the average lifespan is around 30–40 years.[9][10] Male Spiny dogfish use their claspers to impregnate females, which take time to develop properly, and before reaching sexual maturity, tend to be longer than their pelvic fins. During this time, the testes develop, but no sperm will exist inside until later stages are reached, and genital ducts are deformed compared to adult ducts. Once the adult stage is reached, claspers have elongated, and are now hardened with calcium and are still slightly longer than their pelvic fin. At this point testes are fully developed, and sperm exist within the seminal vesicles, and genital ducts conform to a twisted shape we commonly see in adults.[11]

Spiny dogfish are bottom-dwellers. They are commonly found at depths of around 50–149 m (160–490 ft), but have been found deeper than 700 m (2,300 ft).[12]

Life span estimates based on analysis of vertebral centra and annuli in the dorsal spines range from 35 to 54 years.[13]

Commercial use

Braised dogfish

Spiny dogfish are sold as food in Europe, the United States, Canada, New Zealand,[14] Venezuela and Chile. The meat is primarily eaten in England, France, Italy, the Benelux countries, Germany, and as an unwitting houndshark in Greece. The fins and tails are processed into fin needles for cheaper versions of shark fin soup in Chinese cuisine. In England, dogfish are bought in fish and chip shops as "huss", and previously as "rock salmon" until the term was outlawed. Commercial harvests where banned in the UK from 2010 until 2023.[15] In France, they are sold as "small salmon" (saumonette) and in Belgium and Germany as "sea eel" (zeepaling and Seeaal, respectively). In Greece, all small dogfish are commercially called galéos, after the critically endangered Galeorhinus galeus that produces a seasonal dish; other small sharks such as the spiny dogfish substitute it.

Spiny dogfish bodies are ground into fertilizer, liver oil and pet food. Because of their availability, cartilaginous skulls and small sizes, they are popular vertebrate dissection specimens in high schools and universities.

Reported catches varied between 31,700 tonnes in 2000 and 13,800 tonnes in 2008.[16] Bottom trawlers and sink gillnets are the primary tools. In Mid-Atlantic and Southern New England fisheries, they are often caught with larger groundfish, classified as bycatch, and discarded. Recreational fishing accounts for an insignificant portion of the spiny dogfish catch.[17]

The Cape Cod Commercial Fishermen's Alliance promotes sustainable use of the dogfish in restaurants and fish markets in the Cape Cod area of Massachusetts, as of 2017, paid for by the National Oceanographic and Atmospheric Administration. It aims to persuade diners to buy less-popular fish.[18]

Conservation status and management

Once the most abundant shark species in the world, populations of Squalus acanthias have declined significantly. They are classified in the IUCN Red List of threatened species as Vulnerable globally and Critically endangered in the Northeast Atlantic, meaning stocks around Europe have decreased by at least 95%. This is a direct result of overfishing to supply northern Europe's taste for rock salmon, saumonette, and zeepaling. Despite these alarming figures, very few management or conservation measures are in place for Squalus acanthias.[1] In EU waters, a Total Allowable Catch (TAC) has been in place since 1999, but until 2007 it only applied to ICES Areas IIa and IV. It was also set well above the actual weight of fish being caught until 2005, rendering it meaningless. Since 2009 a maximum landing size of one metre (3 ft 3 in) has been imposed in order to protect the most valuable mature females. The TAC for 2011 was set at 0 tons, ending targeted fishing for the species in EU waters. It remains to be seen if populations will be able to recover.[19]

In the recent past the European market for spiny dogfish has increased dramatically, which led to the overfishing and decline of the species. This drastic increase led to the creation and implementation of many fishery management policies placing restrictions on the fishing of spiny dogfish. However, since the species is a late-maturing fish, it takes a while to rebuild the population.

In 2010, Greenpeace International added the spiny dogfish to its seafood red list. "The Greenpeace International seafood red list is a list of fish that are commonly sold in supermarkets around the world, and which have a very high risk of being sourced from unsustainable fisheries."[20] In the same year, the Convention on Migratory Species (CMS; also known as the Bonn Convention) listed the species (Northern Hemisphere populations) under Annex I of its Migratory Shark Memorandum of Understanding.[21]

In recent years, however, the US has implemented fishing controls and opened up the fishery. The proposed quota for 2011 was 16.1 million kilograms (35.5 million lb) with a trip limit of 1,800 kg (4,000 lb), an increase over past years in which the quota has ranged from 2 to 9 million kilograms (5 to 20 million lb), with trip limits from 900 to 1,400 kg (2,000 to 3,000 lb).[22] In 2010, NOAA announced the Eastern US Atlantic spiny dogfish stocks to be rebuilt,[23] and in 2011, concerns about dogfish posing a serious predatory threat to other stocks resulted in an emergency amendment of the quota with nearly 6.8 million kilograms (15 million lb) being added.[24]

In June 2018, the New Zealand Department of Conservation classified Squalus acanthias Linnaeus as "Not Threatened" with the qualifier "Secure Overseas" under the New Zealand Threat Classification System.[25]

In 2023, populations in EU and UK waters were determined to have recovered enough that they could be commercially fished.[26]

Fossil range

Squalus acanthias fossils are known from the Miocene of Denmark and the Netherlands, dating from approximately 11 million years ago.[27] As with other cartilaginous fish, the fossil record of Squalus acanthias consists predominantly of dental material, as cartilage does not fossilize well. The teeth of S. acanthus can be hard to differentiate from those of other squaliforme sharks,[28] making identification difficult.

References

  1. ^ a b Finucci, B.; Cheok, J.; Chiaramonte, G.E.; Cotton, C.F.; Dulvy, N.K.; Kulka, D.W.; Neat, F.C.; Pacoureau, N.; Rigby, C.L.; Tanaka, S.; Walker, T.I. (2020). "Squalus acanthias". IUCN Red List of Threatened Species. 2020: e.T91209505A124551959. doi:10.2305/IUCN.UK.2020-3.RLTS.T91209505A124551959.en. Retrieved 12 November 2021.
  2. ^ "Squalus acanthias". Florida Museum. 2017-05-12. Retrieved 2018-12-03.
  3. ^ "Species Squalus acanthias Linnaeus". FishWisePro. 1758. Retrieved 18 April 2020.
  4. ^ Ebert, D. A.; White, W. T.; Goldman, K. J.; Compagno, L. J.; Daly-Engel, T. S. & Ward, R. D. (2010). "Resurrection and redescription of Squalus suckleyi (Girard, 1854) from the North Pacific, with comments on the Squalus acanthias subgroup (Squaliformes: Squalidae)". Zootaxa. 2612: 22–40. doi:10.11646/zootaxa.2612.1.2.
  5. ^ "Spiny Dogfish". Oceana. Retrieved 2019-02-22.
  6. ^ "Squalus acanthias summary page". FishBase. Retrieved 2019-02-23.
  7. ^ Jones, Thomas S.; Ugland, Karl I. (15 Jan 2021). "Reproduction of female spiny dogfish,Squalus acanthias, in the Oslofjord". NOAA Fisheries Scientific Publications. 4 (99): 685–690. Retrieved 7 March 2022.
  8. ^ Natanson, Lisa J.; McCandless, Camilla T.; James, Kelsey; Hoey, John (8 August 2017). "Gestation period and pupping seasonality of female spiny dogfish (Squalus acanthias) off southern New England". NOAA Fisheries Scientific Publications. 4 (115): 473–483. doi:10.7755/FB.115.4.4.
  9. ^ "Spiny Dogfish". Government of Canada. Government of Canada. 19 December 2016. Retrieved 8 April 2022.
  10. ^ Bargione, Giada; Fortunata, Donato; La Mesa, Mario; Mazzoldi, Carlotta; Riginella, Emilio; Vasapollo, Claudio; Virgili, Massimo; Luchetti, Alessandro (4 October 2019). "Life-history traits of the spiny dogfish Squalus acanthias in the Adriatic Sea". Scientific Reports. 9 (14317): 26–38. Bibcode:2019NatSR...914317B. doi:10.1038/s41598-019-50883-w. PMC 6778190. PMID 31586144.
  11. ^ Ismen, Ali; Yigin, C. Cigdem (1 March 2013). "Reproductive Biology of Spiny Dogfish Squalus acanthias, in the North Aegean Sea". Turkish Journal of Fisheries and Aquatic Sciences. 13: 169–177. doi:10.4194/1303-2712-v13_1_20. Retrieved 28 April 2022.
  12. ^ Jose I. Castro (2011). The Sharks of North America. Oxford University Press, US. p. 58. ISBN 978-0-19-539294-4.
  13. ^ Bubley, W. J.; Kneebone, J.; Sulikowski, J. A.; Tsang, P. C. W. (2012). "Reassessment of spiny dogfish Squalus acanthias age and growth using vertebrae and dorsal-fin spines". Journal of Fish Biology. 80 (5): 1300–1319. doi:10.1111/j.1095-8649.2011.03171.x. ISSN 1095-8649. PMID 22497385.
  14. ^ Vennell, Robert (5 October 2022). Secrets of the Sea: The Story of New Zealand's Native Sea Creatures. HarperCollins Publishers Ltd. pp. 164–169. ISBN 978-1-77554-179-0. Wikidata Q114871191.
  15. ^ Harmsworth, Ellie (8 April 2023). "Rising Costs Put Shark Back on Menu at Britain's Chippies: FT". Retrieved 9 April 2023.
  16. ^ FAO (Food and Agriculture Organization of the United Nations) (2011). Yearbook of fishery and aquaculture statistics 2009. Capture production (PDF). Rome: FAO. pp. 302–303. Archived from the original (PDF) on 2017-05-19.
  17. ^ Katherine Sosebee; Paul Rago (December 2006). "Status of Fishery Resources off the Northeastern US: Spiny dogfish (Squalus acanthias)". NEFSC – Resource Evaluation and Assessment Division.
  18. ^ Wilcox, Meg (2017-07-04). "Dogfish — it's what's for dinner on the Cape". The Boston Globe. Retrieved 2017-07-05.
  19. ^ "Spurdog in the Northeast Atlantic" (PDF). Advice September 2011. ICES, Copenhagen. 2011. Archived (PDF) from the original on 29 May 2021. Retrieved 29 May 2021.
  20. ^ Greenpeace International Seafood Red list Archived February 5, 2010, at the Wayback Machine
  21. ^ Memorandum of Understanding on the Conservation of Migratory Sharks. PDF. Cms.int. Retrieved on 2016-11-14.
  22. ^ "Mid-Atlantic Council Adopts Increase in Spiny Dogfish Quotas". Atlantic Highlands Herald. 19 October 2011. Archived from the original on 2 November 2013.
  23. ^ NOAA Announces Recovery of Spiny Dogfish Stock. greateratlantic.fisheries.noaa.gov
  24. ^ "Threat of Dogfish Sharks Unite Commercial and Recreational Fishermen From Maine to North Carolina". FishNet USA via Prnewswire. May 4, 2009.
  25. ^ Duffy, Clinton A. J.; Francis, Malcolm; Dunn, M. R.; Finucci, Brit; Ford, Richard; Hitchmough, Rod; Rolfe, Jeremy (2018). Conservation status of New Zealand chondrichthyans (chimaeras, sharks and rays), 2016 (PDF). Wellington, New Zealand: Department of Conservation. p. 11. ISBN 9781988514628. OCLC 1042901090.
  26. ^ Chase, Chris (12 March 2023). "UK moving to reopen fishery for a once-endangered species". SeafoodSource. Retrieved 28 March 2023.
  27. ^ "Squalus acanthias Linnaeus 1758 (spiny dogfish)". 2021. Retrieved 17 December 2021.
  28. ^ Kriwet, Jürgen; Klug, Stefanie, eds. (2009), "Biology and Management of Dogfish Sharks", American Fisheries Society, doi:10.47886/9781934874073.ch3, ISBN 9781934874073, retrieved 2022-11-24 {{citation}}: Missing or empty |title= (help)

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Spiny dogfish: Brief Summary

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The spiny dogfish (Squalus acanthias), spurdog, mud shark, or piked dogfish is one of the best known species of the Squalidae (dogfish) family of sharks, which is part of the Squaliformes order.

While these common names may apply to several species, Squalus acanthias is distinguished by two spines (one anterior to each dorsal fin) and no anal fin. It lives in shallow waters and further offshore in most parts of the world, especially in temperate waters. Those in the northern Pacific Ocean were reevaluated in 2010 and found to constitute a separate species, now called the Pacific spiny dogfish (Squalus suckleyi).

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Diet

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Opportunistic feeder, but primarily small fishes such as herrring, capelin and cod

Reference

North-West Atlantic Ocean species (NWARMS)

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Distribution

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Greenland to Argentina

Reference

North-West Atlantic Ocean species (NWARMS)

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Habitat

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Frequents coastal and inshore waters, found at temperatures of 6-15 C.

Reference

North-West Atlantic Ocean species (NWARMS)

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Habitat

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nektonic

Reference

North-West Atlantic Ocean species (NWARMS)

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Habitat

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Known from seamounts and knolls

Reference

Stocks, K. 2009. Seamounts Online: an online information system for seamount biology. Version 2009-1. World Wide Web electronic publication.

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