''Polynemus multifilis'', the elegant paradise fish, is a species of

ray-finned fish Actinopterygii (; ), members of which are known as ray-finned fish or actinopterygians, is a class of bony fish that comprise over 50% of living vertebrate species. They are so called because of their lightly built fins made of webbings of sk ...

, a

threadfin Threadfins are silvery grey fish of the family Polynemidae, taxonomically considered a type of flatfish. Found in tropical to subtropical waters throughout the world, the threadfin family contains eight genera and about 40 species. An unrelated s ...

from the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Polynemidae which is found in rivers in

southeast Asia Southeast Asia is the geographical United Nations geoscheme for Asia#South-eastern Asia, southeastern region of Asia, consisting of the regions that are situated south of China, east of the Indian subcontinent, and northwest of the Mainland Au ...

Description

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

standard length Fish measurement is the measuring of individual fish and various parts of fish anatomy, their anatomies, for data used in many areas of ichthyology, including Taxonomy (biology), taxonomy and fishery biology. Overall length Standard length (SL) is ...

of . It has a pointed snout and the dorsal profile of the head is almost straight, There are two separate

dorsal fin A dorsal fin is a fin on the back of most marine and freshwater vertebrates. Dorsal fins have evolved independently several times through convergent evolution adapting to marine environments, so the fins are not all homologous. They are found ...

s, the first dorsal fin contains 8 spines which are all of a similar thickness at their bases and the second dorsal fin has a single spine and 14-16 soft rats. The

anal fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported o ...

contains 3 spines and 11 to 13 soft rays and its base is shorter than that of the second dorsal fin. The

pectoral fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish aquatic locomotion, swim. Apart from the tail or caudal fin, fish fins have no direct connection with the vertebral column ...

has 14-16 unbranched soft rays and its tip reaches the origin of the anal fin. There are normally fourteen, rarely thirteen or fifteen, pectoral filaments on each side of the body and the count on each side is not necessarily symmetrical. The longest of these are longer than the

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

of the fish. 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 epithelia ...

contains 83-99 pored scales and is simple, it starts at the upper margin of the gill slit and extends to the middle of the

caudal fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported only ...

. The caudal fin is deeply forked but neither lobe bears any filaments. The upper head and upper body are dark purplish-blue and below this the fish is silver in colour. The bases of the dorsal, anal and caudal fins are greyish white while the forward margin of the pelvic fin white. The remaining parts of these fins are semi-transparent as is the pectoral fin.The pectoral filaments are white.

Distribution

''Polynemus multifilis'' has been recorded from the

Chao Phraya The Chao Phraya River 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. Etymology Written evidence of the river being referred to by the ...

River system in Thailand, the Musi and Batanghari rivers in southeastern Sumatra, Indonesia, and on

Borneo Borneo () is the List of islands by area, third-largest island in the world, with an area of , and population of 23,053,723 (2020 national censuses). Situated at the geographic centre of Maritime Southeast Asia, it is one of the Greater Sunda ...

in the

Sampit Sampit is a large town located in East Kotawaringin Regency, Central Kalimantan. Previously a timber port town, it has grown to be a medium-sized community with a population of 166,773 according to Statistics Indonesia in 2019, with the economy ha ...

and Barito rivers in southern

Kalimantan Kalimantan (; ) is the Indonesian portion of the island of Borneo. It constitutes 73% of the island's area, and consists of the provinces of Central Kalimantan, East Kalimantan, North Kalimantan, South Kalimantan, and West Kalimantan. The non-Ind ...

, Indonesia. This species is absent from the

Kapuas River The Kapuas River ( Old Indonesian spelling: Kapoeas River) is a river in the Indonesian part of Borneo island, at the geographic center of Maritime Southeast Asia. At in length, it is the longest river on the island of Borneo, the longest ri ...

where the endemic '' Polynemus kapuasensis'' appears to replace it.

Habitat and biology

''Polynemus multifilis'' is found in freshwater rivers where there is a sandy or muddy substrate. It is a carnivorous species which preys on crustaceans, small fishes and benthic invertebrates.

Fisheries

''Polynemus multifilis'' is highly regarded as a food fish, especially in Thailand. It is also caught for export to Japan as an ornamental fish.

Species description

''Polynemus multifilis'' was first formally described in 1843 by Coenraad Jacob Temminck and Hermann Schlegel with the type locality being given as near

Banjarmasin Banjarmasin is the largest city in South Kalimantan, Indonesia. It was the capital of the province until 15 February 2022. The city is located on a delta island near the junction of the Barito and Martapura rivers. Historically the centre of t ...

on Borneo.

References

{{Taxonbar, from=Q958308 multifilis Taxa named by Coenraad Jacob Temminck - 1846 Taxa named by Hermann Schlegel Fish described in 1843 Fish of Indonesia Fish of Thailand