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Black dogfish
The black dogfish (Centroscyllium fabricii) is a species of dogfish shark in the family Etmopteridae. It is common over the outer continental shelf and continental slope at depths of 180–2,250 m (590–7,380 ft). Females generally inhabit deeper water than males, and depending on the region, smaller sharks may occur at different depths than larger ones. This species is distributed widely in the Atlantic Ocean, from Greenland and Iceland to Virginia and West Africa in the north, and off southwestern Africa and Argentina in the south. The largest member of its family, the black dogfish, typically measures 60–75 cm (24–30 in) long. It has a stocky, dark brown body that is darker below than above, and bears scattered, minute bioluminescent organs. Its two dorsal fins are preceded by stout spines, and the anal fin is absent.
Active and schooling, the black dogfish is an opportunistic predator and scavenger that mainly consumes bony fishes, crustaceans, and cephalopods. It is aplacental viviparous, with females producing litters of four to 40 pups that are sustained to term by a yolk sac. There is no well-defined breeding season, and mating and birthing take place year-round. The black dogfish contributes significantly to the bycatch of deep-sea commercial fisheries operating in the North Atlantic; it is of little commercial value and is usually discarded. As large portions of its range see little deepwater fishing activity and its northwestern Atlantic population seems to be stable, the International Union for Conservation of Nature has listed this species under Least Concern overall. It has been assessed as Near Threatened in the northeastern Atlantic, where its numbers may have declined from heavy fishing pressure.
The first known specimen of the black dogfish was collected near Julianehåb in Greenland and described by Danish zoologist Johannes Reinhardt in his 1825 Ichthyologiske bidrag. Reinhardt gave it the name Spinax fabricii in honor of missionary and naturalist Otto Fabricius, who pioneered the study of Greenlandic fishes. German biologists Johannes Müller and Jakob Henle, in their 1839–41 Systematische Beschreibung der Plagiostomen, created the new genus Centroscyllium for this species.
According to the IUCN, further taxonomic investigation is required to confirm the black dogfish in the North Atlantic and the southeastern Atlantic represent the same species. A 2010 phylogenetic study by Nicolas Straube and colleagues, based on nuclear and mitochondrial DNA, found the black dogfish is the sister species of the whitefin dogfish (C. ritteri), and the two are, in turn, sister to the clade formed by the granular dogfish (C. granulatum) and combtooth dogfish (C. nigrum).
The black dogfish is a common species, with a wide but discontinuous distribution in the temperate waters of the Atlantic Ocean; its range abuts, but does not extend into, the Arctic Ocean. In the northeast, it occurs from Iceland to Sierra Leone, including the Faroe Islands, southern Norway, and the Rockall Trough and Porcupine Seabight off Ireland. In the northwest, it is found from southern Greenland and Baffin Island to Virginia, being particularly abundant in the Laurentian Channel, and may occur further south to the Gulf of Mexico off Alabama. In the southeast, it is found off Namibia and South Africa as far as Cape Agulhas. In the southwest, it has been recorded from the Beagle Channel at the southern tip of Argentina.
Inhabiting the outer continental shelf and continental slope, the black dogfish is found mostly near the bottom in water 180–2,250 m (590–7,380 ft) deep. It is most common at depths of 800–1,200 m (2,600–3,900 ft) off Iceland, 1,250–1,500 m (4,100–4,920 ft) in the Rockall Trough, 500–1,300 m (1,600–4,300 ft) off Greenland, 350–500 m (1,150–1,640 ft) off northern Canada, and below 500 m (1,600 ft) off southern Africa. The species may venture closer to the surface in the northern extreme of its range, particularly during the dark, cold winter months. Depth segregation by sex has been documented in the North Atlantic, with females outnumbering males at depths greater than 1 km (0.62 mi). Depth segregation by size varies by region: larger sharks are generally found in deeper water off western Greenland, in shallower water off western Iceland, and without pattern with respect to depth off eastern Iceland. The black dogfish prefers water temperatures of 3.5–4.5 °C (38.3–40.1 °F), though off northern Canada, it is most abundant in water of 5–6.5 °C (41.0–43.7 °F); it can tolerate temperatures down to 1 °C (34 °F). There is some evidence that this species conducts seasonal migrations, spending winter and spring in shallower water. Sharks off northern Canada perform development-related movements (see below) not observed off western Greenland, suggesting the presence of two distinct stocks in the northwestern Atlantic.
Adult black dogfish typically measure 60–75 cm (24–30 in) in length and can reach 1.1 m (3.6 ft), making it the largest member of its family. Females attain a larger ultimate size than males. The shark has a rather stocky and laterally compressed body, with a moderately long, thick, and flattened snout that forms a very broad arch at the front. The sizable, horizontally oval eyes are a reflective green in life and lack nictitating membranes (protective third eyelids); they are followed a short distance behind by much smaller spiracles (accessory respiratory openings). The nostrils are anteriorly placed and preceded by short flaps of skin. The mouth is wide and evenly arched, with thin lips and short but deep furrows around the corners. There are around 34 tooth rows in either side of both jaws; each tooth has three (occasionally up to five) slender cusps, with the central one the longest.
Both dorsal fins are immediately preceded by stout, grooved spines, with the second much longer than the first. The small first dorsal fin has a rounded apex and a nearly straight trailing margin, with its origin lying behind the pectoral fins. The second dorsal fin is rather angular and has about double the area of the first, with its origin located opposite the midpoint of the pelvic fin bases. The pectoral fins are small and rounded. The pelvic fins are about as large as the second dorsal fin, with rounded tips and nearly straight trailing margins. The caudal peduncle is short and leads to a broad caudal fin comprising less than a quarter of the total length; the upper lobe has a convex upper margin leading to a squared-off tip, while the lower lobe is indistinct. The skin is densely covered by tiny dermal denticles; each one is recurved and thornlike, rising from an irregular star-shaped base. This species is a plain dark brown above, darkening to almost black below, with white dorsal fin spines. Juvenile sharks have white edges on the dorsal, pectoral, and pelvic fins. Minute, luminescent dots are scattered about the skin without a regular pattern.
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Black dogfish
The black dogfish (Centroscyllium fabricii) is a species of dogfish shark in the family Etmopteridae. It is common over the outer continental shelf and continental slope at depths of 180–2,250 m (590–7,380 ft). Females generally inhabit deeper water than males, and depending on the region, smaller sharks may occur at different depths than larger ones. This species is distributed widely in the Atlantic Ocean, from Greenland and Iceland to Virginia and West Africa in the north, and off southwestern Africa and Argentina in the south. The largest member of its family, the black dogfish, typically measures 60–75 cm (24–30 in) long. It has a stocky, dark brown body that is darker below than above, and bears scattered, minute bioluminescent organs. Its two dorsal fins are preceded by stout spines, and the anal fin is absent.
Active and schooling, the black dogfish is an opportunistic predator and scavenger that mainly consumes bony fishes, crustaceans, and cephalopods. It is aplacental viviparous, with females producing litters of four to 40 pups that are sustained to term by a yolk sac. There is no well-defined breeding season, and mating and birthing take place year-round. The black dogfish contributes significantly to the bycatch of deep-sea commercial fisheries operating in the North Atlantic; it is of little commercial value and is usually discarded. As large portions of its range see little deepwater fishing activity and its northwestern Atlantic population seems to be stable, the International Union for Conservation of Nature has listed this species under Least Concern overall. It has been assessed as Near Threatened in the northeastern Atlantic, where its numbers may have declined from heavy fishing pressure.
The first known specimen of the black dogfish was collected near Julianehåb in Greenland and described by Danish zoologist Johannes Reinhardt in his 1825 Ichthyologiske bidrag. Reinhardt gave it the name Spinax fabricii in honor of missionary and naturalist Otto Fabricius, who pioneered the study of Greenlandic fishes. German biologists Johannes Müller and Jakob Henle, in their 1839–41 Systematische Beschreibung der Plagiostomen, created the new genus Centroscyllium for this species.
According to the IUCN, further taxonomic investigation is required to confirm the black dogfish in the North Atlantic and the southeastern Atlantic represent the same species. A 2010 phylogenetic study by Nicolas Straube and colleagues, based on nuclear and mitochondrial DNA, found the black dogfish is the sister species of the whitefin dogfish (C. ritteri), and the two are, in turn, sister to the clade formed by the granular dogfish (C. granulatum) and combtooth dogfish (C. nigrum).
The black dogfish is a common species, with a wide but discontinuous distribution in the temperate waters of the Atlantic Ocean; its range abuts, but does not extend into, the Arctic Ocean. In the northeast, it occurs from Iceland to Sierra Leone, including the Faroe Islands, southern Norway, and the Rockall Trough and Porcupine Seabight off Ireland. In the northwest, it is found from southern Greenland and Baffin Island to Virginia, being particularly abundant in the Laurentian Channel, and may occur further south to the Gulf of Mexico off Alabama. In the southeast, it is found off Namibia and South Africa as far as Cape Agulhas. In the southwest, it has been recorded from the Beagle Channel at the southern tip of Argentina.
Inhabiting the outer continental shelf and continental slope, the black dogfish is found mostly near the bottom in water 180–2,250 m (590–7,380 ft) deep. It is most common at depths of 800–1,200 m (2,600–3,900 ft) off Iceland, 1,250–1,500 m (4,100–4,920 ft) in the Rockall Trough, 500–1,300 m (1,600–4,300 ft) off Greenland, 350–500 m (1,150–1,640 ft) off northern Canada, and below 500 m (1,600 ft) off southern Africa. The species may venture closer to the surface in the northern extreme of its range, particularly during the dark, cold winter months. Depth segregation by sex has been documented in the North Atlantic, with females outnumbering males at depths greater than 1 km (0.62 mi). Depth segregation by size varies by region: larger sharks are generally found in deeper water off western Greenland, in shallower water off western Iceland, and without pattern with respect to depth off eastern Iceland. The black dogfish prefers water temperatures of 3.5–4.5 °C (38.3–40.1 °F), though off northern Canada, it is most abundant in water of 5–6.5 °C (41.0–43.7 °F); it can tolerate temperatures down to 1 °C (34 °F). There is some evidence that this species conducts seasonal migrations, spending winter and spring in shallower water. Sharks off northern Canada perform development-related movements (see below) not observed off western Greenland, suggesting the presence of two distinct stocks in the northwestern Atlantic.
Adult black dogfish typically measure 60–75 cm (24–30 in) in length and can reach 1.1 m (3.6 ft), making it the largest member of its family. Females attain a larger ultimate size than males. The shark has a rather stocky and laterally compressed body, with a moderately long, thick, and flattened snout that forms a very broad arch at the front. The sizable, horizontally oval eyes are a reflective green in life and lack nictitating membranes (protective third eyelids); they are followed a short distance behind by much smaller spiracles (accessory respiratory openings). The nostrils are anteriorly placed and preceded by short flaps of skin. The mouth is wide and evenly arched, with thin lips and short but deep furrows around the corners. There are around 34 tooth rows in either side of both jaws; each tooth has three (occasionally up to five) slender cusps, with the central one the longest.
Both dorsal fins are immediately preceded by stout, grooved spines, with the second much longer than the first. The small first dorsal fin has a rounded apex and a nearly straight trailing margin, with its origin lying behind the pectoral fins. The second dorsal fin is rather angular and has about double the area of the first, with its origin located opposite the midpoint of the pelvic fin bases. The pectoral fins are small and rounded. The pelvic fins are about as large as the second dorsal fin, with rounded tips and nearly straight trailing margins. The caudal peduncle is short and leads to a broad caudal fin comprising less than a quarter of the total length; the upper lobe has a convex upper margin leading to a squared-off tip, while the lower lobe is indistinct. The skin is densely covered by tiny dermal denticles; each one is recurved and thornlike, rising from an irregular star-shaped base. This species is a plain dark brown above, darkening to almost black below, with white dorsal fin spines. Juvenile sharks have white edges on the dorsal, pectoral, and pelvic fins. Minute, luminescent dots are scattered about the skin without a regular pattern.
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