BLACK DOGFISH

Taxonomy:

Phylum– Chordata

Class– Chondrichthyles

Subclass– Elasmobranchii

Order– Squaliformes

Common Name– Dogfish Sharks

Family– Etmopteridae

Common Name– Lantern Sharks

Genus– Centroscyllium

Species– fabriciI

Status: IUCN Red List LEAST CONCERN

Average Size and Length: The Black dogfish are born around 15 cm. Males typically measures between 1.5-2 feet, and females between 1.6-2.2 feet. The maximum recorded length is between 2.8-3.5 feet long. It is one of the largest members of its family. It seems that the average length at maturity for both males and females differ by location.

Current Rare Mythical Sightings: 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. German biologists Johannes Müller and Jakob Henle, in their 1839–41 Systematische Beschreibung der Plagiostomen, created the new genus Centroscyllium.

Teeth and Jaw: The mouth of the Black dogfish 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, consisting of 68 teeth; each tooth has three (and sometimes up to five) slender cusps. The central cusp is the longest. The teeth are comb-like in both jaws.

Head: The Black dogfish has a long, thick, and flattened snout that forms a very broad arch at the front. The sizable, horizontally oval eyes are a reflective green when living and lack nictitating membranes. There are short spiracles behind the eyes. The nostrils are anteriorly placed and preceded by short flaps of skin.

Denticles: The skin is densely covered by tiny close-set dermal denticles; each one is recurved and thorn-like, rising from an irregular star-shaped base. They are short and conical with hooked cusps and ridged, stellate bases. The skin contains tiny pigmented bioluminescent dots.

Tail: The caudal peduncle of the Black dogfish is short and leads to a broad caudal fin covering less than a quarter of the total length. The upper lobe has a convex upper margin leading to a squared-off tip. The lower lobe is indistinct.

Demographic, Distribution, Habitat, Environment and Range: Black dogfish is widespread and can be found in the Atlantic Ocean in temperate waters, from Greenland and Iceland to Virginia and West Africa in the north, and off southwestern Africa and Argentina in the south. The tropical sightings aren’t confirmed and could be a misidentification of a separate species. Black dogfish can be found over the outer continental shelf and continental slope at depths of 591-5,250 feet, and possibly as deep as 7,382 feet. They are typically found in depths greater than 902 feet, but each preferred depth per location may vary. Females normally inhabit deeper water than males. The size and depth correlation can differ depending on region. In the higher latitudes, they are typically found closer to the surface during dark winter months. The Black dogfish prefers water temperatures of 38.3–40.1 °F, though off northern Canada, it is most abundant in water of 41.0–43.7 °F and it can tolerate temperatures down to 34 °F.

There is some evidence that this species conducts seasonal migrations, spending winter and spring in shallower water Black dogfish off northern Canada perform development-related movements that are not observed off western Greenland, suggesting the presence of two distinct groups in the northwestern Atlantic.

Diet: They typically eat crustaceans, bony fish, and cephalopods. They are highly active and opportunistic predators and scavengers. Rattails, whitings, rockfishes, lanternfishes, and barracudinas are some preferred bony fish. Fish become a progressively more important food source as the shark ages, while crustaceans like krill and shrimp become less important. Infrequently, polychaete worms and jellyfish are also eaten. In the northwestern Atlantic, Greenland halibut (Reinhardtius hippoglossoides) and rattail offal discarded from fishing vessels have become a major source of food for this species, particularly for older sharks that are capable of consuming larger pieces such as heads.

Potential predators of the Black dogfish are larger sharks and bony fishes.

Aesthetic Identification: The Black dogfish is dark brown dorsally, and even darker ventrally. Its body is stalky and lateral compressed. The Black dogfish has tiny bioluminescent organs that are scattered and not uniform. They resemble tiny dots. Both dorsal fins are immediately preceded by stout, grooved spines that are white, 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. Some suggest that juvenile sharks have white edges on the dorsal, pectoral, and pelvic fins, but this is unconfirmed.

Biology and Reproduction: The Black dogfish is ovoviviparous having 7-8 pups per litter. There are some suggestions that they may have at least 14 pups per litter. Breeding season isn’t defined and seems to take place year-round.

One known parasite is the barnacle Anelasma squalicola, which attaches in front of the second dorsal fin and impairs the reproductive development. Other known parasites include the fluke Otodistomum cestoides, the copepods Neoalbionella fabricii and Neoalbionella centroscyllii, and the protozoans Haemogregarina delagei and Trypanosoma rajae.

Behavioral Traits, Sensing and Intelligence: The Black dogfish are known to form a shoal or a school and do segregate by sex. The larger schools are found in shallower water during winter and spring. They are active and opportunistic predators in open water. They do scavenge towards the bottom.

Speed: Its swimming muscles exhibit lower activity of glycolytic enzymes and higher activity of creatine phosphokinase, suggesting a lesser capacity for bursts of speed. It has a lipid-filled liver that comprises about one-fifth of its total weight and functions in maintaining neutral buoyancy.

Black Dogfish Future and Conservation: The Black dogfish is abundant and of least concern overall. They are discarded as bycatch. There is very little commercial value. Some may be returned to port and used in processing fish meal. There is very little deepwater commercial fishing activity within its range. It has been assessed as Near Threatened in the northeastern Atlantic, where its numbers may have declined from heavy fishing pressure. These statistics do vary by location.

Black Dogfish Recorded Attacks on Humans: Not a threat to humans.