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 fresh-water 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.