Threadfins


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Threadfins or polynemids are the common names for the members of the Polynemidae family. They are found in the tropical and subtropical waters of all oceans. Most of the threadfins are important food fishes in many parts of the tropics. They are easily identified as a family due to their similarity in overall body appearance, condition of the eye and pectoral fin rays. The pectoral fins are divided into 2 sections, the upper fin with attached rays and the lower fin with 3 to 16 long unattached rays. The unattached pectoral rays have been considered to operate as a sense organ, enabling them to search for food in muddy water.

Most species occur in coastal waters and estuaries, although some live entirely in freshwater rivers. Threadfins generally occur on sandy and muddy bottoms in depths less than 150 meters. They feed on small fishes and crustaceans. A few small species feed on plankton.

There are 8 genera and about 42 species worldwide. Malaysia is represented by 5 genera and about 12 species.


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Scientific Name: Eleutheronema rhadinum  (Jordan & Evermann, 1902)
English Name: East Asian Fourfinger Threadfin
Mandarin Name | 鱼类中文名: 四指马鲅 (Sì zhǐ mǎ bà), 四指马友 (Sì zhǐ mǎ yǒu), 午鱼 (Wǔ yú), 午仔 (Wǔ zǐ)
Local Malay Name: Ikan Senangin, Senangin Rambu Empat
Local Hokkien: Ngor Hu, Pek Ngor, Ngor-ah
Main Identification Features: 4 pectoral filaments. Vomer with 2 deciduous tooth plates. 11 to 14 scale rows above lateral line; 15 to 17 below. Pectoral-fin membranes black when fresh. Posterior portion of maxilla deep.
Size: Maximum standard length at about 75 cm.
Habitat and Ecology: Mud and sand bottoms along coasts and probably in estuaries.
Remarks: Eleutheronema rhadinum are supposed to be endemic to China, Taiwan, Japan and Vietnam. This specimen is caught in Tanjung Leman, Malaysia.

Eleutheronema rhadinum




Scientific Name: Eleutheronema tetradactylum  (Shaw, 1804)
English Name: Fourfinger Threadfin
Mandarin Name | 鱼类中文名: 四指马鲅 (Sì zhǐ mǎ bà), 四指马友 (Sì zhǐ mǎ yǒu), 午鱼 (Wǔ yú), 午仔 (Wǔ zǐ)
Local Malay Name: Ikan Senangin, Senangin Rambu Empat
Thai Name | ชื่อสามัญภาษาไทย: ปลากุเราหนวดสี่เส้น (Plā kureā h̄nwd s̄ī̀ s̄ên)
Local Hokkien: Ngor Hu, Pek Ngor
Main Identification Features: 4 pectoral filaments. Vomer with 2 deciduous tooth plates. 9 to 12 scale rows above lateral line; 13 to 15 below. Pectoral-fin membranes vivid yellow when fresh.
Size: Maximum standard length at least 160 cm, commonly to 59 cm standard length.
Habitat and Ecology: Mud and sand bottoms along coasts and in estuaries, to 30 m depth. Juveniles feeds mainly on prawns, shrimps and mysids. Adults prey on other fishes, including mullets, sillagos and croakers.

Eleutheronema tetradactylum

Fourfinger Threadfin




Scientific Name: Eleutheronema tridactylum  (Bleeker, 1849)
English Name: Threefinger Threadfin
Mandarin Name | 鱼类中文名: 三趾四指马鲅 (Sān zhǐ sì zhǐ mǎ bà), 三指马鲅 (Sān zhǐ mǎ bà), 三指马友 (Sān zhǐ mǎ yǒu), 午鱼 (Wǔ yú), 午仔 (Wǔ zǐ)
Local Malay Name: Ikan Senangin, Senangin Rambu Tiga
Thai Name | ชื่อสามัญภาษาไทย: ปลากุเราสามเส้น (Plā kureā s̄ām s̄ên)
Local Hokkien: Ngor Hu, Pek Ngor, Soon Hong
Main Identification Features: 3 pectoral filaments. Vomer without tooth plates.
Size: A smaller species compared to the Fourfinger Threadfin. Maximum standard length at least 30 cm.
Habitat and Ecology: Occurs along coasts.

Threefinger Threadfin or Eleutheronema tridactylum




Scientific Name: Leptomelanosoma indicum  (Shaw, 1804)
English Name: Indian Threadfin
Mandarin Name | 鱼类中文名: 印度马鮁 (Yìndù mǎ bà), 顺风午 (Shùnfēng wǔ), 黑午 (Hēi wǔ)
Local Malay Name: Ikan Kurau, Senohong
Thai Name | ชื่อสามัญภาษาไทย: ปลากุเราหางยาว (Plā kureā h̄āngyāw)
Local Hokkien: Soon Hong, Or Ngor
Main Identification Features: 5 pectoral filaments. Back and head greyish green or purplish black. Tips of upper and lower caudal-fin lobes filamentous. Pectoral-fin membrane deep black.
Size: Maximum standard length at least 113 cm, commonly to 63 cm standard length.
Habitat and Ecology: Occurs mainly near estuaries, to 100 m depth. Occasionally entering rivers. Juveniles feed on small crustaceans, including shrimps and prawn larvae, but become piscivorous with increasing growth. Percentage of fishes eaten increases with size.

Indian Threadfin

Leptomelanosoma indicum




Scientific Name: Polydactylus sextarius  (Bloch & Schneider, 1801)
English Name: Blackspot Threadfin, Blackspot Tasselfish
Mandarin Name | 鱼类中文名: 六丝马鲅 (Liù sī mǎ bà), 午仔 (Wǔ zǐ)
Local Malay Name: Ikan Senangin Buih Tanda
Thai Name | ชื่อสามัญภาษาไทย: ปลากุเราปานดำ (Plā kureā pān dả)
Local Hokkien: Zhi Ngor
Main Identification Features: 6 pectoral filaments. Dark spot present near origin of lateral line covering about second through eighth lateral-line scale.
Size: Maximum standard length at least 22 cm, commonly to 14 cm standard length.
Habitat and Ecology: Occurs mainly near estuaries, over sand or sand-mud flats, 19 to 73 m depth. Feeds on crustaceans, sponges, and fishes.

Blackspot Threadfin or Polydactylus sextarius



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