Threadfin
Encyclopedia
Threadfins are silvery grey perciform marine fish
of the family
Polynemidae. Found in tropical to subtropical waters throughout the world, the threadfin family contains nine genera
and 33 species
. An unrelated species sometimes known by the name threadfin, Alectis indicus, is properly the Indian threadfish
(family Carangidae
).
Ranging in length from 20 centimetres (7.9 in) in the black-finned threadfin (Polydactylus nigripinnis) to 200 centimetres (78.7 in) in fourfinger threadfins (Eleutheronema tetradactylum
) and giant African threadfin
s (Polydactylus quadrifilis), threadfins are both important to commercial fisheries
as a food fish, and popular among angler
s. Their habit of forming large schools makes the threadfins a reliable and economic catch.
s widely separate. Their tail fins are large and deeply forked; indicating speed and agility. The mouth is large and inferior; a blunt snout projects far ahead. The jaws and palate possess bands of villiform (fibrous) teeth. Their most distinguishing feature is their pectoral fins: they are composed of two distinct sections, the lower of which consists of between 3-7 long, thread-like independent rays. In Polynemus species there may be up to 15 of these modified rays.
In some species, such as the royal threadfin (Pentanemus quinquarius), the thread-like rays may extend well past the tail fin. This feature explains both the common name threadfin and the family name Polynemidae, from the Greek
poly meaning "many" and nema meaning "filament." Similar species, such as the mullets
(family Mugilidae) and milkfish
(family Chanidae) can be easily distinguished from threadfins by their lack of filamentous pectoral rays.
s. Their pectoral rays are thought to serve as tactile structures, helping to find prey within the sediment
s. Noted for being euryhaline
, threadfins are able to tolerate a wide range of salinity
levels. This attribute allows threadfins to enter estuaries
and even river
s. They feed primarily on crustaceans and smaller fish.
. The eggs float freely with the currents until hatching.
, sixfinger threadfins (Polydactylus sexfilis) are the subject of commercial open-ocean cage mariculture
.
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
of 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...
Polynemidae. Found in tropical to subtropical waters throughout the world, the threadfin family contains nine genera
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
and 33 species
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...
. An unrelated species sometimes known by the name threadfin, Alectis indicus, is properly the Indian threadfish
Indian threadfish
The Indian threadfish, Alectis indicus, is a large species of coastal marine fish of the jack family, Carangidae. The species is widespread in the waters of the tropical Indo-West Pacific Ocean, ranging from east Africa to India, Asia, Indonesia and Australia...
(family Carangidae
Carangidae
Carangidae is a family of fish which includes the jacks, pompanos, jack mackerels, and scads.They are marine fish found in the Atlantic, Indian and Pacific Oceans...
).
Ranging in length from 20 centimetres (7.9 in) in the black-finned threadfin (Polydactylus nigripinnis) to 200 centimetres (78.7 in) in fourfinger threadfins (Eleutheronema tetradactylum
Eleutheronema tetradactylum
Eleutheronema tetradactylum, also known as Indian Salmon, is a threadfin fish of the Polynemidae family. This highly commercial fish known for uses in aquaculture occur mainly over shallow muddy bottoms in coastal waters forming loose schools. Adults of this highly vulnerable species enter rivers...
) and giant African threadfin
Giant African threadfin
Giant African threadfin is a fish species in the family Polynemidae. There are two varieties: one freshwater and one saltwater. Both have white flesh and are cooked similarly to European seabass.-Biography:...
s (Polydactylus quadrifilis), threadfins are both important to commercial fisheries
Fishery
Generally, a fishery is an entity engaged in raising or harvesting fish which is determined by some authority to be a fishery. According to the FAO, a fishery is typically defined in terms of the "people involved, species or type of fish, area of water or seabed, method of fishing, class of boats,...
as a food fish, and popular among angler
Fishing
Fishing is the activity of trying to catch wild fish. Fish are normally caught in the wild. Techniques for catching fish include hand gathering, spearing, netting, angling and trapping....
s. Their habit of forming large schools makes the threadfins a reliable and economic catch.
Physical description
Their bodies are elongate and fusiform, with spinous and soft dorsal finDorsal fin
A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...
s widely separate. Their tail fins are large and deeply forked; indicating speed and agility. The mouth is large and inferior; a blunt snout projects far ahead. The jaws and palate possess bands of villiform (fibrous) teeth. Their most distinguishing feature is their pectoral fins: they are composed of two distinct sections, the lower of which consists of between 3-7 long, thread-like independent rays. In Polynemus species there may be up to 15 of these modified rays.
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
poly meaning "many" and nema meaning "filament." Similar species, such as the mullets
Mullet (fish)
The mullets or grey mullets are a family and order of ray-finned fish found worldwide in coastal temperate and tropical waters, and in some species in fresh water. Mullets have served as an important source of food in Mediterranean Europe since Roman times...
(family Mugilidae) and milkfish
Milkfish
The milkfish is the sole living species in the family Chanidae. - Description and biology :...
(family Chanidae) can be easily distinguished from threadfins by their lack of filamentous pectoral rays.
Range and habitat
Threadfins frequent open, shallow water in areas with muddy, sandy or silty bottoms; they are rarely glimpsed at reefReef
In nautical terminology, a reef is a rock, sandbar, or other feature lying beneath the surface of the water ....
s. Their pectoral rays are thought to serve as tactile structures, helping to find prey within the sediment
Sediment
Sediment is naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of fluids such as wind, water, or ice, and/or by the force of gravity acting on the particle itself....
s. Noted for being euryhaline
Euryhaline
Euryhaline organisms are able to adapt to a wide range of salinities. An example of a euryhaline fish is the molly which can live in fresh, brackish, or salt water. The European shore crab is an example of a euryhaline invertebrate that can live in salt and brackish water...
, threadfins are able to tolerate a wide range of salinity
Salinity
Salinity is the saltiness or dissolved salt content of a body of water. It is a general term used to describe the levels of different salts such as sodium chloride, magnesium and calcium sulfates, and bicarbonates...
levels. This attribute allows threadfins to enter estuaries
Estuary
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....
and even 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. They feed primarily on crustaceans and smaller fish.
Reproduction
Presumed to be pelagic spawners, threadfins probably release many tiny buoyant eggs into the water column which then become part of the planktonPlankton
Plankton are any drifting organisms that inhabit the pelagic zone of oceans, seas, or bodies of fresh water. That is, plankton are defined by their ecological niche rather than phylogenetic or taxonomic classification...
. The eggs float freely with the currents until hatching.
Mariculture
In HawaiiHawaii
Hawaii is the newest of the 50 U.S. states , and is the only U.S. state made up entirely of islands. It is the northernmost island group in Polynesia, occupying most of an archipelago in the central Pacific Ocean, southwest of the continental United States, southeast of Japan, and northeast of...
, sixfinger threadfins (Polydactylus sexfilis) are the subject of commercial open-ocean cage mariculture
Mariculture
Mariculture is a specialized branch of aquaculture involving the cultivation of marine organisms for food and other products in the open ocean, an enclosed section of the ocean, or in tanks, ponds or raceways which are filled with seawater. An example of the latter is the farming of marine fish,...
.
Species
There are about forty species in eight genera:- Genus Eleutheronema
- Indian Salmon or East Asian Fourfinger threadfin, Eleutheronema tetradactylumEleutheronema tetradactylumEleutheronema tetradactylum, also known as Indian Salmon, is a threadfin fish of the Polynemidae family. This highly commercial fish known for uses in aquaculture occur mainly over shallow muddy bottoms in coastal waters forming loose schools. Adults of this highly vulnerable species enter rivers...
(Shaw, 1804)(replaced by Eleutheronema rhadinum (JordanDavid Starr JordanDavid Starr Jordan, Ph.D., LL.D. was a leading eugenicist, ichthyologist, educator and peace activist. He was president of Indiana University and Stanford University.-Early life and education:...
& Evermann, 1902)). - Threefinger threadfin, Eleutheronema tridactylum (BleekerPieter BleekerPieter Bleeker was a Dutch medical doctor and ichthyologist, famous for his work on the fishes of East Asia – Atlas Ichthyologique des Orientales Neerlandaises – which was published 1862–1877....
, 1849).
- Indian Salmon or East Asian Fourfinger threadfin, Eleutheronema tetradactylum
- Genus Filimanus
- Sevenfinger threadfin, Filimanus heptadactyla (CuvierGeorges CuvierGeorges Chrétien Léopold Dagobert Cuvier or Jean Léopold Nicolas Frédéric Cuvier , known as Georges Cuvier, was a French naturalist and zoologist...
, 1829). - Javanese threadfin, Filimanus hexanema (CuvierGeorges CuvierGeorges Chrétien Léopold Dagobert Cuvier or Jean Léopold Nicolas Frédéric Cuvier , known as Georges Cuvier, was a French naturalist and zoologist...
, 1829). - Splendid threadfin, Filimanus perplexa Feltes, 1991.
- Eightfinger threadfin, Filimanus sealei (JordanDavid Starr JordanDavid Starr Jordan, Ph.D., LL.D. was a leading eugenicist, ichthyologist, educator and peace activist. He was president of Indiana University and Stanford University.-Early life and education:...
& RichardsonJohn Richardson (naturalist)Sir John Richardson was a Scottish naval surgeon, naturalist and arctic explorer.Richardson was born at Dumfries. He studied medicine at Edinburgh University, and became a surgeon in the navy in 1807. He traveled with John Franklin in search of the Northwest Passage on the Coppermine Expedition of...
, 1910). - Filimanus similis Feltes, 1991.
- Yellowthread threadfin, Filimanus xanthonema (ValenciennesAchille ValenciennesAchille Valenciennes was a French zoologist.Valenciennes was born in Paris, and studied under Georges Cuvier. Valenciennes' study of parasitic worms in humans made an important contribution to the study of parasitology...
, 1831).
- Sevenfinger threadfin, Filimanus heptadactyla (Cuvier
- Genus Galeoides
- Lesser African threadfin, Galeoides decadactylus (BlochMarcus Elieser BlochMarcus Elieser Bloch was a German medical doctor and naturalist. He is generally considered one of the most important ichthyologists of the 18th century.- Life :...
, 1795).
- Lesser African threadfin, Galeoides decadactylus (Bloch
- Genus Leptomelanosoma
- Indian threadfin, Leptomelanosoma indicum (Shaw, 1804).
- Genus Parapolynemus
- Dwarf paradise fish, Parapolynemus verekeri (Saville-Kent, 1889).
- Genus Pentanemus
- Royal threadfin, Pentanemus quinquarius (LinnaeusCarolus LinnaeusCarl Linnaeus , also known after his ennoblement as , was a Swedish botanist, physician, and zoologist, who laid the foundations for the modern scheme of binomial nomenclature. He is known as the father of modern taxonomy, and is also considered one of the fathers of modern ecology...
, 1758).
- Royal threadfin, Pentanemus quinquarius (Linnaeus
- Genus Polydactylus
- Blue bobo, Polydactylus approximans (Lay & Bennett, 1839).
- Slender fivefinger threadfin, Polydactylus bifurcus Motomura, Kimura & Iwatsuki, 2001.
- Long-limb threadfin, Polydactylus longipes Motomura, Okamoto & Iwatsuki, 2001.
- King threadfinKing threadfinThe King threadfin, Polydactylus macrochir, is a threadfin native to tropical waters of northern Australia and southern Papua New Guinea.Other common names include King Threadfin Salmon, King Salmon, Threadfin Salmon, Burnett River Salmon...
, Polydactylus macrochir (Günther, 1867). - River threadfin, Polydactylus macrophthalmus (BleekerPieter BleekerPieter Bleeker was a Dutch medical doctor and ichthyologist, famous for his work on the fishes of East Asia – Atlas Ichthyologique des Orientales Neerlandaises – which was published 1862–1877....
, 1858). - African blackspot threadfin, Polydactylus malagasyensis Motomura & Iwatsuki, 2001.
- Small-mouthed threadfin, Polydactylus microstomus (BleekerPieter BleekerPieter Bleeker was a Dutch medical doctor and ichthyologist, famous for his work on the fishes of East Asia – Atlas Ichthyologique des Orientales Neerlandaises – which was published 1862–1877....
, 1851). - Polydactylus mullani (Hora, 1926).
- Australian threadfin, Polydactylus multiradiatus (Günther, 1860).
- Black-finned threadfin, Polydactylus nigripinnis Munro, 1964.
- Atlantic threadfinAtlantic threadfinThe Atlantic threadfin, Polydactylus octonemus, is a threadfin native to subtropical and temperate waters of the western Atlantic Ocean and the Gulf of Mexico. It grows up to 23 cm in length....
, Polydactylus octonemus (GirardCharles Frédéric GirardCharles Frédéric Girard was a French biologist specializing in ichthyology and herpetology.Born in Mulhouse, France, he studied at the College of Neuchâtel, Switzerland as a student of Louis Agassiz. In 1847, he accompanied Agassiz as his assistant to Harvard...
, 1858). - Littlescale threadfin, Polydactylus oligodon (Günther, 1860).
- Yellow bobo, Polydactylus opercularis Seale & Bean, 1907.
- Persian blackspot threadfin, Polydactylus persicus Motomura & Iwatsuki, 2001.
- Striped threadfin, Polydactylus plebeius (Broussonet, 1782).
- Giant African threadfinGiant African threadfinGiant African threadfin is a fish species in the family Polynemidae. There are two varieties: one freshwater and one saltwater. Both have white flesh and are cooked similarly to European seabass.-Biography:...
, Polydactylus quadrifilis (CuvierGeorges CuvierGeorges Chrétien Léopold Dagobert Cuvier or Jean Léopold Nicolas Frédéric Cuvier , known as Georges Cuvier, was a French naturalist and zoologist...
, 1829). - Sixfinger threadfin, Polydactylus sexfilis (ValenciennesAchille ValenciennesAchille Valenciennes was a French zoologist.Valenciennes was born in Paris, and studied under Georges Cuvier. Valenciennes' study of parasitic worms in humans made an important contribution to the study of parasitology...
, 1831). - Blackspot threadfin, Polydactylus sextarius (BlochMarcus Elieser BlochMarcus Elieser Bloch was a German medical doctor and naturalist. He is generally considered one of the most important ichthyologists of the 18th century.- Life :...
& SchneiderJohann Gottlob SchneiderJohann Gottlob Theaenus Schneider was a German classicist and naturalist.-Biography:Schneider was born at Collm in Saxony...
, 1801). - Polydactylus siamensis Motomura, Iwatsuki & Yoshino, 2001.
- Barbu, Polydactylus virginicus (LinnaeusCarolus LinnaeusCarl Linnaeus , also known after his ennoblement as , was a Swedish botanist, physician, and zoologist, who laid the foundations for the modern scheme of binomial nomenclature. He is known as the father of modern taxonomy, and is also considered one of the fathers of modern ecology...
, 1758).
- Genus Polynemus
- Northern paradise fish, Polynemus aquilonaris Motomura, 2003.
- Polynemus bidentatus Motomura & Tsukawaki, 2006.
- Eastern paradise fish, Polynemus dubius BleekerPieter BleekerPieter Bleeker was a Dutch medical doctor and ichthyologist, famous for his work on the fishes of East Asia – Atlas Ichthyologique des Orientales Neerlandaises – which was published 1862–1877....
, 1854. - Hornaday's paradise fish, Polynemus hornadayi Myers, 1936.
- Elegant paradiseus fish, Polynemus multifilis TemminckCoenraad Jacob TemminckCoenraad Jacob Temminck was a Dutch aristocrat and zoologist.Temminck was the first director of the National Natural History Museum at Leiden from 1820 until his death. His Manuel d'ornithologie, ou Tableau systematique des oiseaux qui se trouvent en Europe was the standard work on European birds...
& SchlegelHermann SchlegelHermann Schlegel was a German ornithologist and herpetologist.-Early life and education:Schlegel was born at Altenburg, the son of a brassfounder. His father collected butterflies, which stimulated Schlegel's interest in natural history...
, 1843. - Paradise threadfin, Polynemus paradiseus LinnaeusCarolus LinnaeusCarl Linnaeus , also known after his ennoblement as , was a Swedish botanist, physician, and zoologist, who laid the foundations for the modern scheme of binomial nomenclature. He is known as the father of modern taxonomy, and is also considered one of the fathers of modern ecology...
, 1758.