''Brevitrygon walga'', the dwarf whipray or mangrove whipray, is a small stingray, a

cartilaginous fish Chondrichthyes (; ) is a class that contains the cartilaginous fishes that have skeletons primarily composed of cartilage. They can be contrasted with the Osteichthyes or ''bony fishes'', which have skeletons primarily composed of bone tissue ...

in the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Dasyatidae. It is a

demersal 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 of ...

fish and is found over the continental and insular shelf of the west central Pacific Ocean where it is heavily fished. The

IUCN The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natu ...

has assessed it as being "

near-threatened A near-threatened species is a species which has been categorized as "Near Threatened" (NT) by the International Union for Conservation of Nature as that may be vulnerable to endangerment in the near future, but it does not currently qualify fo ...

Description

The dwarf whipray has a maximum length of . The disc width is commonly about . In outline it is oval with a bluntly-pointed snout. The whip-like tail is longer than the body and lacks the skin fold found in some related species. Females have a shorter tail than males, with a bulbous tip, and both sexes have four to six erectile, venomous spines at the base of the tail. The dwarf whipray is a uniform pinkish or beige colour and has been mistaken for a

horseshoe crab Horseshoe crabs are marine and brackish water arthropods of the family Limulidae and the only living members of the order Xiphosura. Despite their name, they are not true crabs or crustaceans: they are chelicerates, most closely related to arachn ...

turbid Turbidity is the cloudiness or haziness of a fluid caused by large numbers of individual particles that are generally invisible to the naked eye, similar to smoke in air. The measurement of turbidity is a key test of water quality. Fluids can ...

water.

Distribution and habitat

The dwarf whipray is found in the western central Pacific Ocean. Its range extends from Thailand, Cambodia and Vietnam to Singapore, Malaysia, the Philippines and Indonesia. It has been recorded from India, but may have been confused there with the scaly whipray (''Brevitrygon imbricata''). It occurs close to the sandy seabed on the inner

continental shelf A continental shelf is a portion of a continent that is submerged under an area of relatively shallow water, known as a shelf sea. Much of these shelves were exposed by drops in sea level during glacial periods. The shelf surrounding an island ...

at depths usually less than .

Biology

The dwarf whipray reaches maturity at a length of about . Mating occurs when the male grasps the female with their ventral surfaces in contact. This fish is

viviparous Among animals, viviparity is development of the embryo inside the body of the parent. This is opposed to oviparity which is a reproductive mode in which females lay developing eggs that complete their development and hatch externally from the m ...

, giving birth to one or two young at a time. The

gestation period In mammals, pregnancy is the period of reproduction during which a female carries one or more live offspring from implantation in the uterus through gestation. It begins when a fertilized zygote implants in the female's uterus, and ends once it ...

is not known, but before birth, the pups are fed on secretions from the uterine wall, a process known as

histotrophy Histotrophy is a form of matrotrophy exhibited by some live-bearing sharks and rays, in which the developing embryo receives additional nutrition from its mother in the form of uterine secretions, known as histotroph (or "uterine milk"). It is one o ...

Use

The dwarf whipray is caught, largely as

bycatch Bycatch (or by-catch), in the fishing industry, is a fish or other marine species that is caught unintentionally while fishing for specific species or sizes of wildlife. Bycatch is either the wrong species, the wrong sex, or is undersized or juve ...

, over most of its wide range. Trawling for batoids is common in many places and trammel netting, in which the fish get entangled in the fine-meshed central net of a three-part net, is used over much of its range. The fish is used for human consumption, but is not specifically targeted, probably because of its small size.

Status

The

International Union for Conservation of Nature The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natu ...

has assessed the conservation status of the dwarf whipray as being "

". The organisation considers the fish is experiencing intense fishing pressure over much of its range and is being over-exploited. Its abundance appears to be falling and the size of the fish caught also seems to be declining.

References

{{Taxonbar, from=Q11925647 dwarf whipray Fish of the Indian Ocean Marine fauna of South Asia dwarf whipray