The dumb gulper shark (''Centrophorus harrissoni'') is a rare and endangered deepwater
dogfish, found along the east coast of Australia and in isolated spots north and west of New Zealand. It is also known as the dumb shark, Harrison's deep-sea dogfish, or Harrison's dogfish.
Characteristics
The dumb gulper shark may grow to be long and has a long, robust head, a long, flattened snout, a large y mouth, and large, green eyes, which help it see at 820 to 1260 ft (250 to 385 m) under water.
[White, W.T., Ebert, D.A. & Compagno, L.J.V. (2008)]
Description of two new species of gulper sharks, genus Centrophorus (Chondrichthyes: Squaliformes: Centrophoridae) from Australia
(PDF), pp. 1–21. In: P.R. Last, W.T. White & J.J. Pogonoski (eds). Descriptions of New Australian Chondrichthyans. CSIRO Marine & Atmospheric Research Paper 022, 358 pp.
The body is slender and of moderate size, and is grey to greyish-brown in colour, with a paler underside. Of the two dorsal fins, the first is larger than the second, and each has a short spine, a white rear margin, and a dark blotch towards the front, which is more distinct in juveniles.
[ The large caudal fin is asymmetrical, with a longer upper lobe compared to the lower lobe.][
The broad teeth of this species differs between the upper and lower jaws, with the lower teeth being much larger. The teeth also differ between the male and female, with the male having much more erect, upright upper teeth, and upward-curving tips on the lower teeth.][ The dumb gulper shark is very similar in appearance to the closely related little gulper shark.
]
Habitat
This shark is found off the coasts of eastern Australia and New Zealand. Its habitat is in the demersal zone
The demersal zone is the part of the sea or ocean (or deep lake) consisting of the part of the water column near to (and significantly affected by) the seabed and the benthos. The demersal zone is just above the benthic zone and forms a layer o ...
on the upper to middle continental slope
A continental margin is the outer edge of continental crust abutting oceanic crust under coastal waters. It is one of the three major zones of the ocean floor, the other two being deep-ocean basins and mid-ocean ridges.
The continental margi ...
.
Behaviour
These sharks eat mostly teleost
Teleostei (; Ancient Greek, Greek ''teleios'' "complete" + ''osteon'' "bone"), members of which are known as teleosts (), is, by far, the largest group of ray-finned fishes (class Actinopterygii), with 96% of all neontology, extant species of f ...
fishes (particularly myctophids
Lanternfish (or myctophids, from the Greek language, Greek μυκτήρ ''myktḗr'', "nose" and ''ophis'', "serpent") are small mesopelagic fish of the large family (biology), family Myctophidae. One of two families in the order Myctophiformes, ...
), cephalopods
A cephalopod is any member of the molluscan Taxonomic rank, class Cephalopoda (Greek language, Greek plural , ; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral symm ...
and crustaceans
Crustaceans (from Latin meaning: "those with shells" or "crusted ones") are invertebrate animals that constitute one group of Arthropod, arthropods that are traditionally a part of the subphylum Crustacea (), a large, diverse group of mainly aquat ...
.[Daley, R., Stevens, J. and Graham, K. 2002. Catch analysis and productivity of the deepwater dogfish resource in southern Australia. Report by CSIRO Marine Research and NSW Fisheries to the Fisheries Research and Development Corporation. FRDC Project 1998/108.] Females produce a maximum of one to two pups every one to two years. Newborn pups range in size from 35 cm to 40 cm. Evidence suggests that the left-side uterus is less functional than the right-side.
Population
The population size is unknown, but numbers have decreased as much as 99% in some areas since the 1970s. This species is harvested, by trawling
Trawling is an industrial method of fishing that involves pulling a fishing net through the water behind one or more boats. The net used for trawling is called a trawl. This principle requires netting bags which are towed through water to catch di ...
or drop lining, for meat
Meat is animal Tissue (biology), tissue, often muscle, that is eaten as food. Humans have hunted and farmed other animals for meat since prehistory. The Neolithic Revolution allowed the domestication of vertebrates, including chickens, sheep, ...
and liver oil (squalene
Squalene is an organic compound. It is a triterpene with the formula C30H50. It is a colourless oil, although impure samples appear yellow. It was originally obtained from shark liver oil (hence its name, as '' Squalus'' is a genus of sharks). ...
). Upper-slope dogfish species are more vulnerable to capture than mid-slope species, because they are targeted throughout their vertical distribution and most of their local geographic distribution.[Andrew, N.L., Graham, K.J., Hodgson, K.E. and Gordon, G.N.G. 1997. Changes after twenty years in relative abundance and size composition of commercial fishes caught during fishery independent surveys on SEF trawl grounds. NSW Fisheries Final Report Series No. 1 FRDC Project No. 96/139.] The low reproductive rate, late age of maturity, and long lifespan typical of these sharks means they are likely unable to recover quickly after depletion.
Conservation
Action is being taken to preserve the dumb gulper, which includes being incorporated into the Environmental Protection and Biodiversity Conservation (EPBC) Act to create a plan to keep this species safe. In response to this species’ inherent low productivity and continuing reduced numbers, managers have introduced landing restrictions and area closures to enhance ''C. harrissoni'' stocks in southern Australian waters.Department of Conservation
Department may refer to:
* Departmentalization, division of a larger organization into parts with specific responsibility
Government and military
*Department (administrative division), a geographical and administrative division within a country, ...
has classified the dumb gulper shark as "Data Deficient" with the qualifier "Threatened Overseas" under the New Zealand Threat Classification System
The New Zealand Threat Classification System is used by the Department of Conservation to assess conservation priorities of species in New Zealand.
The system was developed because the IUCN Red List, a similar conservation status system, had s ...
.
References
External links
ARKIVE
Dumb gulper shark - Videos, photos and facts
{{Taxonbar, from=Q994856
dumb gulper shark
Fish of New Caledonia
Fauna of New South Wales
Tasman Sea
dumb gulper shark