''Polynemus aquilonaris'', commonly known as the northern paradise fish, is a fish of the

threadfin Threadfins are silvery grey perciform fish of the family Polynemidae. Found in tropical to subtropical waters throughout the world, the threadfin family contains eight genera and about 40 species. An unrelated species sometimes known by the name ...

family Polynemidae. It is native to the large rivers of

mainland Southeast Asia Mainland Southeast Asia, also known as the Indochinese Peninsula or Indochina, is the continental portion of Southeast Asia. It lies east of the Indian subcontinent and south of Mainland China and is bordered by the Indian Ocean to the west an ...

Description

''Polynemus aquilonaris'' is a medium-sized species of threadfin which attains a maximum

total length Fish measurement is the measuring of individual fish and various parts of their anatomies. These data are used in many areas of ichthyology, including taxonomy and fisheries biology. Overall length * Standard length (SL) is the length of a fish ...

of . It has a pointed snout and a dorsal profile which is nearly straight. There are two separate

dorsal fin A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom. Many species of animals possessing dorsal fins are not particularly closely related to each other, though through conv ...

s, the first dorsal fin with 8 spines in which the bases of the spines have a similar thickness and the second dorsal fin has a single spine and 15 to 19 soft rays. The

anal fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as se ...

has 3 spines and 11 to 13 soft rays and it has a base that is shorter than the base of the second dorsal-fin base. The pectoral fin has 15 to 17 unbranched rays and has a length equivalent to 34 to 41% of the

standard length Fish measurement is the measuring of individual fish and various parts of their anatomies. These data are used in many areas of ichthyology, including taxonomy and fisheries biology. Overall length * Standard length (SL) is the length of a fish m ...

with its tip falling just short of or reaching slightly beyond the origin of the anal fin. It has 7 pectoral filaments the shortest being the first which does not reach the tip of the

pelvic fin Pelvic fins or ventral fins are paired fins located on the ventral surface of fish. The paired pelvic fins are homologous to the hindlimbs of tetrapods. Structure and function Structure In actinopterygians, the pelvic fin consists of two en ...

and the longest extends well past the tips of the tail. The

caudal fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as se ...

is deeply forked, with long lobes neither of them being filamentous. The

lateral line The lateral line, also called the lateral line organ (LLO), is a system of sensory organs found in fish, used to detect movement, vibration, and pressure gradients in the surrounding water. The sensory ability is achieved via modified epithelial ...

is simple, extends from the upper part of the gill slit to the tail. The head and body are greyish silver on the back and silver below. The front margin of the first dorsal fin and the rear margin of the second dorsal fin are blackish, they are otherwise translucent. The pectoral fins are also translucent. The bases of the pectoral filaments are white, becoming blackish on their tips, The pelvic fin is translucent with its base and its rear edge being white. The white anal fin has a translucent posterior margin with a similar pattern on the tail.

Distribution

''Polynemus aquilonaris'' is found in south-east Asia in the countries of Thailand, Cambodia, Laos and Vietnam where it is found in the drainage basins of the

Chao Phraya The Chao Phraya ( or ; th, แม่น้ำเจ้าพระยา, , or ) is the major river in Thailand, with its low alluvial plain forming the centre of the country. It flows through Bangkok and then into the Gulf of Thailand. Et ...

and

Mekong The Mekong or Mekong River is a trans-boundary river in East Asia and Southeast Asia. It is the world's List of rivers by length, twelfth longest river and List of longest rivers of Asia, the third longest in Asia. Its estimated length is , ...

including Tonle Sap and its associated rivers.

Habitat and biology

''Polynemus aquilonaris'' occurs where there are sandy or muddy bottoms in freshwater rivers and estuaries where it feeds on small crustaceans, small fishes, and benthic organisms. This species has not been found to have any hermaphroditic phases and it is thought that it has separate sexes.

Fisheries

''Polynemus aquilonaris'' is esteemed as a food fish within its range. It is exported to Japan as an ornamental species.

Species description and taxonomy

''Polynemus aquilonaris'' was first formally described in 2003 by Hiroyuku Motomura from a

specimen Specimen may refer to: Science and technology * Sample (material), a limited quantity of something which is intended to be similar to and represent a larger amount * Biological specimen or biospecimen, an organic specimen held by a biorepository ...

purchased at Samyan Fish Market which had been caught in the Chao Phraya. It had previously been considered that the paradise fish in north of Malaya were populations of the ''

Polynemus dubius ''Polynemus'' is a genus of threadfins (family Polynemidae). They are native to South and Southeast Asia and, depending on the species, occur in freshwater, brackish, and/or marine environments. The family Polynemidae is characterized by the pec ...

'' but Motomura showed that they were a separate species.

References

{{Taxonbar, from=Q2678479 Fish of the Mekong Basin Fish of Cambodia Fish of Laos Fish of Thailand Fish of Vietnam Taxa named by Hiroyuki Motomura Fish described in 2003 aquilonaris