Ganges stingray
Encyclopedia
The Ganges stingray or Gangetic stingray (Himantura fluviatilis) is a little-known species
of stingray
in the family
Dasyatidae, apparently endemic to the Ganges River
system and adjacent marine waters. With an oval pectoral fin disc and long projecting snout, it closely resembles, and may be the same species as, the giant freshwater stingray (H. chaophraya) of Southeast Asia
. Growing to 1.4 m (4.6 ft) across, it is a plain dark color above, and lighter below with wide dark bands on the lateral disc margins. The International Union for Conservation of Nature (IUCN) has listed this species as Endangered, as it faces overfishing
and habitat degradation within its heavily populated range.
, geographer
, and naturalist
Francis Buchanan-Hamilton
, in his 1822 account of Ganges River
fishes, made reference to a species of freshwater stingray he named Raia fluviatilis. However, he deferred making a description until an illustration could be made, an opportunity that never arose, and as a result his account only notes that the ray "has a strong resemblance to Raia lymma [=Taeniura lymma] [and] has nearly the same manners as Raia aquila [=Myliobatis aquila]". Subsequent authors have published accounts of this species under the name Trygon fluviatilis, and then Himantura fluviatilis, while noting that the name has questionable validity due to the paucity of Hamilton's description. The Ganges stingray belongs to the same species group as H. chaophraya; the two species may in fact be synonymous
, but this cannot yet be confirmed as no specimens are available for comparison.
to the area around Kanpur, some 1600 km (994.2 mi) from the furthest extent of the tide
. Later authors have also reported it from shallow bay
s in Bay of Bengal
, and at a depth of 37–55 m (121.4–180.4 ft) near Madras. This ray is likely completely isolated from other populations of freshwater stingrays in various parts of Southeast Asia.
.
within its range. The International Union for Conservation of Nature (IUCN) has assessed the Ganges stingray as Endangered: it has a restricted distribution in a heavily populated region, which renders it susceptible to overfishing
and habitat degradation. This species is also listed on Schedule I of the Indian Wildlife (Protection) Act of 1972.
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
Myliobatiformes
Myliobatiformes is one of the four orders of batoids, cartilaginous fishes related to sharks. They were formerly included in the order Rajiformes, but more recent phylogenetic studies have shown that the myliobatiforms are a monophyletic group, and that its more derived members evolved their...
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, apparently endemic to the Ganges River
Ganges River
The Ganges or Ganga, , is a trans-boundary river of India and Bangladesh. The river rises in the western Himalayas in the Indian state of Uttarakhand, and flows south and east through the Gangetic Plain of North India into Bangladesh, where it empties into the Bay of Bengal. By discharge it...
system and adjacent marine waters. With an oval pectoral fin disc and long projecting snout, it closely resembles, and may be the same species as, the giant freshwater stingray (H. chaophraya) of Southeast Asia
Southeast Asia
Southeast Asia, South-East Asia, South East Asia or Southeastern Asia is a subregion of Asia, consisting of the countries that are geographically south of China, east of India, west of New Guinea and north of Australia. The region lies on the intersection of geological plates, with heavy seismic...
. Growing to 1.4 m (4.6 ft) across, it is a plain dark color above, and lighter below with wide dark bands on the lateral disc margins. The International Union for Conservation of Nature (IUCN) has listed this species as Endangered, as it faces overfishing
Overfishing
Overfishing occurs when fishing activities reduce fish stocks below an acceptable level. This can occur in any body of water from a pond to the oceans....
and habitat degradation within its heavily populated range.
Taxonomy
Scottish physicianPhysician
A physician is a health care provider who practices the profession of medicine, which is concerned with promoting, maintaining or restoring human health through the study, diagnosis, and treatment of disease, injury and other physical and mental impairments...
, geographer
Geography
Geography is the science that studies the lands, features, inhabitants, and phenomena of Earth. A literal translation would be "to describe or write about the Earth". The first person to use the word "geography" was Eratosthenes...
, and naturalist
Naturalist
Naturalist may refer to:* Practitioner of natural history* Conservationist* Advocate of naturalism * Naturalist , autobiography-See also:* The American Naturalist, periodical* Naturalism...
Francis Buchanan-Hamilton
Francis Buchanan-Hamilton
Dr Francis Buchanan, later known as Francis Hamilton but often referred to as Francis Buchanan-Hamilton was a Scottish physician who made significant contributions as a geographer, zoologist, and botanist while living in India.The standard botanical author abbreviation Buch.-Ham. is applied to...
, in his 1822 account of Ganges River
Ganges River
The Ganges or Ganga, , is a trans-boundary river of India and Bangladesh. The river rises in the western Himalayas in the Indian state of Uttarakhand, and flows south and east through the Gangetic Plain of North India into Bangladesh, where it empties into the Bay of Bengal. By discharge it...
fishes, made reference to a species of freshwater stingray he named Raia fluviatilis. However, he deferred making a description until an illustration could be made, an opportunity that never arose, and as a result his account only notes that the ray "has a strong resemblance to Raia lymma [=Taeniura lymma] [and] has nearly the same manners as Raia aquila [=Myliobatis aquila]". Subsequent authors have published accounts of this species under the name Trygon fluviatilis, and then Himantura fluviatilis, while noting that the name has questionable validity due to the paucity of Hamilton's description. The Ganges stingray belongs to the same species group as H. chaophraya; the two species may in fact be synonymous
Synonym (taxonomy)
In scientific nomenclature, a synonym is a scientific name that is or was used for a taxon of organisms that also goes by a different scientific name. For example, Linnaeus was the first to give a scientific name to the Norway spruce, which he called Pinus abies...
, but this cannot yet be confirmed as no specimens are available for comparison.
Distribution and habitat
Hamilton noted that the Ganges stingray was common in the Ganges River system from the estuaryEstuary
An estuary is a partly enclosed coastal body of water with one or more rivers or streams flowing into it, and with a free connection to the open sea....
to the area around Kanpur, some 1600 km (994.2 mi) from the furthest extent of the tide
Tide
Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the moon and the sun and the rotation of the Earth....
. Later authors have also reported it from shallow bay
Bay
A bay is an area of water mostly surrounded by land. Bays generally have calmer waters than the surrounding sea, due to the surrounding land blocking some waves and often reducing winds. Bays also exist as an inlet in a lake or pond. A large bay may be called a gulf, a sea, a sound, or a bight...
s in Bay of Bengal
Bay of Bengal
The Bay of Bengal , the largest bay in the world, forms the northeastern part of the Indian Ocean. It resembles a triangle in shape, and is bordered mostly by the Eastern Coast of India, southern coast of Bangladesh and Sri Lanka to the west and Burma and the Andaman and Nicobar Islands to the...
, and at a depth of 37–55 m (121.4–180.4 ft) near Madras. This ray is likely completely isolated from other populations of freshwater stingrays in various parts of Southeast Asia.
Description
The Ganges stingray has a very thin, oval pectoral fin disc slightly wider than long, with broadly rounded lateral margins. The snout tapers to a narrow point and projects considerably beyond the disc, measuring over twice as long as the distance between the eyes, which are very small. The tail is whip-like, lacks fin folds, and is less than twice as long as the disc. The entire upper surface, except for the pelvic fins, is covered by dermal denticles that become larger on the head. Some of the denticles on the posterior half of the body are also enlarged, and bear sharp spines. Large areas of the underside are covered by minute denticles. The coloration is a plain purplish gray above, becoming darker towards the disc margins, and light below with broad, irregular dark bands bordering the lateral margins. This is a large species, reaching a width of at least 1.4 m (4.6 ft).Biology and ecology
Virtually nothing is known of the natural history of the Ganges stingray. It is presumably aplacental viviparous like other members of its orderOrder (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
.
Human interactions
Only a few specimens of Ganges stingray are recorded in literature, none of which remain to the present day. Hamilton noted that this ray was often sold at Kanpur markets, and that its tail spine can inflict "very dangerous wounds". It probably continues to be caught as bycatchBycatch
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...
within its range. The International Union for Conservation of Nature (IUCN) has assessed the Ganges stingray as Endangered: it has a restricted distribution in a heavily populated region, which renders it susceptible to overfishing
Overfishing
Overfishing occurs when fishing activities reduce fish stocks below an acceptable level. This can occur in any body of water from a pond to the oceans....
and habitat degradation. This species is also listed on Schedule I of the Indian Wildlife (Protection) Act of 1972.