Any one of several species of fishes belonging to Polynemus and allied genera. They have numerous long pectoral filaments.

mullet-like tropical marine fishes having pectoral fins with long threadlike rays

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 known as the Indian threadfish (family Carangidae).