Thorntail stingray
Encyclopedia
The thorntail stingray, black stingray, or longtail stingray (Dasyatis thetidis) is a species
of stingray
in the family
Dasyatidae. It is found off southern Africa
, Australia
, and New Zealand
from the intertidal zone
to a depth of 440 m (1,443.6 ft). This bottom-dweller inhabits soft-bottomed habitat
s such as lagoon
s, estuaries, and reef
s. Growing to 1.8 m (5.9 ft) across and over 200 kg (440.9 lb) in weight, the thorntail stingray is among the largest stingrays in the world. Uniformly dark above and light below, it has a diamond-shaped pectoral fin disc and a very long, whip-like tail with a fin fold underneath. The upper surface of the disc and the tail bear numerous stout, sharp thorns.
The diet of the thorntail stingray consists of benthic invertebrate
s and bony fishes. It has been known to gather in large groups during summertime. Like other stingrays, it is aplacental viviparous, with the developing embryo
s sustained to term by histotroph ("uterine milk") produced by the mother. The venom
ous stinging spine of the thorntail stingray can inflict a painful injury, though it is not aggressive towards humans. It is caught by commercial
and recreational fishers
, though the impact of such activities on its population is unknown. As a result, the International Union for Conservation of Nature (IUCN) has listed this species as Data Deficient
.
Australia
n ichthyologist James Douglas Ogilby originally described the thorntail stingray from four specimens collected off New South Wales
during the 1898 scientific expedition of the trawler HMCS Thetis, after which the species was named. His account was published a year later in the scientific journal
Memoirs of the Australian Museum. Other common name
s for this species include black skate, black stingaree, long-tailed stingaree, longtail black stingray, thorn stingray, and thorntail ray.
from Algoa Bay
, South Africa
to Barra da Falsa, Mozambique
and Réunion
, as well as off Australia from Shark Bay
to northern New South Wales
, Lord Howe Island
, Norfolk Island
, and New Zealand. It is fairly common off Australia and New Zealand and less so elsewhere. Favoring inshore habitats with soft bottoms, this benthic species is commonly encountered in estuaries and lagoon
s, around rocky and coral reef
s, and over reef flats. In Australia, it has been known to swim up river
s. Off New Zealand, large groups of thorntail stingrays have been seen inside caves and beneath rocky arches. This species is known to occur as deep as 440 m (1,443.6 ft).
e across the floor with the outermost pair smaller and set apart from the others. The tooth rows number 25–43 in the upper jaw and 29–48 in the lower jaw, and are arranged with a quincunx
pattern into pavement-like surfaces.
The pelvic fins have rounded tips and gently curved trailing margins. The whip-like tail measures about twice the length of the disc and bears on the upper surface 1–2 long stinging spines with up to 88 serrations. A narrow fin fold runs beneath the tail and ends well before the tail tip. Large juveniles and adults have a row of large, sharp thorns running along the midline of the back from behind the eyes to the tail spine, and thorns of various sizes are also scattered about the dorsal surface of the disc. The tail behind the spine is densely covered by stout thorns. This species is a uniform dark brown or gray to black above and whitish below. The longer tail, presence of thorns, and absence of white dots atop the disc differentiate this species from the short-tail stingray
(D. brevicaudata), another giant stingray that shares its range.
s, mantis shrimp
, bivalves, polychaete worms, and conger eels
. Off New Zealand, both it and the short-tail stingray regularly fall prey to local killer whales (Orcinus orca). A known parasite of this species is the nematode
Echinocephalus overstreeti. Thorntail stingrays have been reported to congregate in warm, shallow waters during the summer, possibly for reproductive purposes. This species is aplacental viviparous like other stingrays.
, Western Australia
, many thorntail stingrays, short-tail stingrays, and Australian bull ray
s (Myliobatis australis) regularly gather to be hand-fed fish scraps; the number of visitors has steadily increased in recent years, and there is interest in developing the site as a permanent tourist attraction.
Thorntail stingrays are caught as bycatch
in nets and on line gear, probably in low numbers. Most individuals landed are discarded, though the rate of post-capture survival is unknown as this species may be subject to persecution by fishery workers. Recreational anglers
sometimes hook this ray, which may be difficult to bring in due to its size. At present, the International Union for Conservation of Nature (IUCN) lacks sufficient information to assess the thorntail stingray beyond Data Deficient
. From 1986 to 1997, New Zealand reported an average annual catch of 15 tons for this species and the short-tail stingray combined, though this figure may underestimate the total fishery impact.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of stingray
Stingray
The stingrays are a group of rays, which are cartilaginous fishes related to sharks. They are classified in the suborder Myliobatoidei of the order Myliobatiformes, and consist of eight families: Hexatrygonidae , Plesiobatidae , Urolophidae , Urotrygonidae , Dasyatidae , Potamotrygonidae The...
in the family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Dasyatidae. It is found off southern Africa
Southern Africa
Southern Africa is the southernmost region of the African continent, variably defined by geography or geopolitics. Within the region are numerous territories, including the Republic of South Africa ; nowadays, the simpler term South Africa is generally reserved for the country in English.-UN...
, Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
, and New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
from the intertidal zone
Intertidal zone
The intertidal zone is the area that is above water at low tide and under water at high tide . This area can include many different types of habitats, with many types of animals like starfish, sea urchins, and some species of coral...
to a depth of 440 m (1,443.6 ft). This bottom-dweller inhabits soft-bottomed habitat
Habitat
* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...
s such as lagoon
Lagoon
A lagoon is a body of shallow sea water or brackish water separated from the sea by some form of barrier. The EU's habitat directive defines lagoons as "expanses of shallow coastal salt water, of varying salinity or water volume, wholly or partially separated from the sea by sand banks or shingle,...
s, estuaries, and reef
Reef
In nautical terminology, a reef is a rock, sandbar, or other feature lying beneath the surface of the water ....
s. Growing to 1.8 m (5.9 ft) across and over 200 kg (440.9 lb) in weight, the thorntail stingray is among the largest stingrays in the world. Uniformly dark above and light below, it has a diamond-shaped pectoral fin disc and a very long, whip-like tail with a fin fold underneath. The upper surface of the disc and the tail bear numerous stout, sharp thorns.
The diet of the thorntail stingray consists of benthic invertebrate
Invertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...
s and bony fishes. It has been known to gather in large groups during summertime. Like other stingrays, it is aplacental viviparous, with the developing embryo
Embryo
An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...
s sustained to term by histotroph ("uterine milk") produced by the mother. The venom
Venom
Venom is the general term referring to any variety of toxins used by certain types of animals that inject it into their victims by the means of a bite or a sting...
ous stinging spine of the thorntail stingray can inflict a painful injury, though it is not aggressive towards humans. It is caught by commercial
Commercial fishing
Commercial fishing is the activity of catching fish and other seafood for commercial profit, mostly from wild fisheries. It provides a large quantity of food to many countries around the world, but those who practice it as an industry must often pursue fish far into the ocean under adverse conditions...
and recreational fishers
Recreational fishing
Recreational fishing, also called sport fishing, is fishing for pleasure or competition. It can be contrasted with commercial fishing, which is fishing for profit, or subsistence fishing, which is fishing for survival....
, though the impact of such activities on its population is unknown. As a result, the International Union for Conservation of Nature (IUCN) has listed this species as Data Deficient
Data Deficient
Data Deficient is a category applied by the IUCN, other agencies, and individuals to a species when the available information is not sufficient for a proper assessment of conservation status to be made...
.
Taxonomy
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
n ichthyologist James Douglas Ogilby originally described the thorntail stingray from four specimens collected off New South Wales
New South Wales
New South Wales is a state of :Australia, located in the east of the country. It is bordered by Queensland, Victoria and South Australia to the north, south and west respectively. To the east, the state is bordered by the Tasman Sea, which forms part of the Pacific Ocean. New South Wales...
during the 1898 scientific expedition of the trawler HMCS Thetis, after which the species was named. His account was published a year later in the scientific journal
Scientific journal
In academic publishing, a scientific journal is a periodical publication intended to further the progress of science, usually by reporting new research. There are thousands of scientific journals in publication, and many more have been published at various points in the past...
Memoirs of the Australian Museum. Other common name
Common name
A common name of a taxon or organism is a name in general use within a community; it is often contrasted with the scientific name for the same organism...
s for this species include black skate, black stingaree, long-tailed stingaree, longtail black stingray, thorn stingray, and thorntail ray.
Distribution and habitat
The thorntail stingray is found off southern AfricaSouthern Africa
Southern Africa is the southernmost region of the African continent, variably defined by geography or geopolitics. Within the region are numerous territories, including the Republic of South Africa ; nowadays, the simpler term South Africa is generally reserved for the country in English.-UN...
from Algoa Bay
Algoa Bay
Algoa Bay is a wide inlet along the South African east coast, some 425 miles east of the Cape of Good Hope. It is bounded in the west by Cape Recife and in the east by Cape Padrone. The bay is up to 436 m deep...
, South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
to Barra da Falsa, Mozambique
Mozambique
Mozambique, officially the Republic of Mozambique , is a country in southeastern Africa bordered by the Indian Ocean to the east, Tanzania to the north, Malawi and Zambia to the northwest, Zimbabwe to the west and Swaziland and South Africa to the southwest...
and Réunion
Réunion
Réunion is a French island with a population of about 800,000 located in the Indian Ocean, east of Madagascar, about south west of Mauritius, the nearest island.Administratively, Réunion is one of the overseas departments of France...
, as well as off Australia from Shark Bay
Shark Bay
Shark Bay is a World Heritage listed bay in Western Australia. The term may also refer to:* the locality of Shark Bay, now known as Denham* Shark Bay Marine Park* Shark Bay , a shark exhibit at Sea World, Gold Coast, Australia* Shire of Shark Bay...
to northern New South Wales
New South Wales
New South Wales is a state of :Australia, located in the east of the country. It is bordered by Queensland, Victoria and South Australia to the north, south and west respectively. To the east, the state is bordered by the Tasman Sea, which forms part of the Pacific Ocean. New South Wales...
, Lord Howe Island
Lord Howe Island
Lord Howe Island is an irregularly crescent-shaped volcanic remnant in the Tasman Sea between Australia and New Zealand, directly east of mainland Port Macquarie, and about from Norfolk Island. The island is about 11 km long and between 2.8 km and 0.6 km wide with an area of...
, Norfolk Island
Norfolk Island
Norfolk Island is a small island in the Pacific Ocean located between Australia, New Zealand and New Caledonia. The island is part of the Commonwealth of Australia, but it enjoys a large degree of self-governance...
, and New Zealand. It is fairly common off Australia and New Zealand and less so elsewhere. Favoring inshore habitats with soft bottoms, this benthic species is commonly encountered in estuaries and lagoon
Lagoon
A lagoon is a body of shallow sea water or brackish water separated from the sea by some form of barrier. The EU's habitat directive defines lagoons as "expanses of shallow coastal salt water, of varying salinity or water volume, wholly or partially separated from the sea by sand banks or shingle,...
s, around rocky and coral reef
Coral reef
Coral reefs are underwater structures made from calcium carbonate secreted by corals. Coral reefs are colonies of tiny living animals found in marine waters that contain few nutrients. Most coral reefs are built from stony corals, which in turn consist of polyps that cluster in groups. The polyps...
s, and over reef flats. In Australia, it has been known to swim up river
River
A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...
s. Off New Zealand, large groups of thorntail stingrays have been seen inside caves and beneath rocky arches. This species is known to occur as deep as 440 m (1,443.6 ft).
Description
One of the largest members of its family, the thorntail stingray reaches at least 4 m (13.1 ft) long, 1.8 m (5.9 ft) across, and 214 kg (471.8 lb) in weight. This species has a diamond-shaped pectoral fin disc about one-fourth wider than long, with sinuous leading margins converging to a slightly protruding snout tip and rounded outer and trailing margins. The mouth is slightly arched; there are five papillaPapilla (fish mouth structure)
The papilla, in certain kinds of fish, particularly rays, sharks, and catfish, are small lumps of dermal tissue found in the mouth, where they are "distributed uniformly on the tongue, palate, and pharynx"...
e across the floor with the outermost pair smaller and set apart from the others. The tooth rows number 25–43 in the upper jaw and 29–48 in the lower jaw, and are arranged with a quincunx
Quincunx
A quincunx is a geometric pattern consisting of five points arranged in a cross, that is five coplanar points, four of them forming a square or rectangle and a fifth at its center...
pattern into pavement-like surfaces.
The pelvic fins have rounded tips and gently curved trailing margins. The whip-like tail measures about twice the length of the disc and bears on the upper surface 1–2 long stinging spines with up to 88 serrations. A narrow fin fold runs beneath the tail and ends well before the tail tip. Large juveniles and adults have a row of large, sharp thorns running along the midline of the back from behind the eyes to the tail spine, and thorns of various sizes are also scattered about the dorsal surface of the disc. The tail behind the spine is densely covered by stout thorns. This species is a uniform dark brown or gray to black above and whitish below. The longer tail, presence of thorns, and absence of white dots atop the disc differentiate this species from the short-tail stingray
Short-tail stingray
The short-tail stingray or smooth stingray is a common species of stingray in the family Dasyatidae. It occurs off southern Africa, typically offshore at a depth of , and off southern Australia and New Zealand, from the intertidal zone to a depth of...
(D. brevicaudata), another giant stingray that shares its range.
Biology and ecology
During the day, thorntail stingrays are often seen resting on patches of sand. This species preys mainly upon crabCrab
True crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" , or where the reduced abdomen is entirely hidden under the thorax...
s, mantis shrimp
Mantis shrimp
Mantis shrimp or stomatopods are marine crustaceans, the members of the order Stomatopoda. They are neither shrimp nor mantids, but receive their name purely from the physical resemblance to both the terrestrial praying mantis and the shrimp. They may reach in length, although exceptional cases of...
, bivalves, polychaete worms, and conger eels
Congridae
Congridae is the family of conger and garden eels. Congers are valuable and often large food fishes, while garden eels live in colonies, all protruding from the sea floor after the manner of plants in a garden...
. Off New Zealand, both it and the short-tail stingray regularly fall prey to local killer whales (Orcinus orca). A known parasite of this species is the nematode
Nematode
The nematodes or roundworms are the most diverse phylum of pseudocoelomates, and one of the most diverse of all animals. Nematode species are very difficult to distinguish; over 28,000 have been described, of which over 16,000 are parasitic. It has been estimated that the total number of nematode...
Echinocephalus overstreeti. Thorntail stingrays have been reported to congregate in warm, shallow waters during the summer, possibly for reproductive purposes. This species is aplacental viviparous like other stingrays.
Human interactions
The tail spine of the thorntail stingray is potentially injurious to humans. It is reportedly unaggressive and approachable, and can be conditioned to accept being "ridden" by divers. At Hamelin BayHamelin Bay, Western Australia
Hamelin Bay is a bay and a locality on the south west coast of Western Australia between Cape Leeuwin and Cape Naturaliste. It is named after French explorer Jacques Félix Emmanuel Hamelin who sailed through the area in about 1801...
, Western Australia
Western Australia
Western Australia is a state of Australia, occupying the entire western third of the Australian continent. It is bounded by the Indian Ocean to the north and west, the Great Australian Bight and Indian Ocean to the south, the Northern Territory to the north-east and South Australia to the south-east...
, many thorntail stingrays, short-tail stingrays, and Australian bull ray
Australian bull ray
The Australian bull ray or southern eagle ray is a large eagle ray of temperate waters of Australia. It is possible that it is the same species as the New Zealand eagle ray ....
s (Myliobatis australis) regularly gather to be hand-fed fish scraps; the number of visitors has steadily increased in recent years, and there is interest in developing the site as a permanent tourist attraction.
Thorntail stingrays are caught as bycatch
Bycatch
The term “bycatch” is usually used for fish caught unintentionally in a fishery while intending to catch other fish. It may however also indicate untargeted catch in other forms of animal harvesting or collecting...
in nets and on line gear, probably in low numbers. Most individuals landed are discarded, though the rate of post-capture survival is unknown as this species may be subject to persecution by fishery workers. Recreational anglers
Recreational fishing
Recreational fishing, also called sport fishing, is fishing for pleasure or competition. It can be contrasted with commercial fishing, which is fishing for profit, or subsistence fishing, which is fishing for survival....
sometimes hook this ray, which may be difficult to bring in due to its size. At present, the International Union for Conservation of Nature (IUCN) lacks sufficient information to assess the thorntail stingray beyond Data Deficient
Data Deficient
Data Deficient is a category applied by the IUCN, other agencies, and individuals to a species when the available information is not sufficient for a proper assessment of conservation status to be made...
. From 1986 to 1997, New Zealand reported an average annual catch of 15 tons for this species and the short-tail stingray combined, though this figure may underestimate the total fishery impact.