Threadfin Salmon

The term “threadfin salmon” can apply to two species: the king threadfin (Polydactylus macrochir), and the slightly smaller blue threadfin (Polydactylus tetradactylum). Both species are locally important in sport angling. They are silver-grey with elongated bodies, sharp snouts and there are four or five filamentous rays extending from the pectoral fins. These fin extensions apparently help them locate food. These fish are carnivorous, feeding mostly on invertebrates and small fish near the sea or riverbed. They engulf their prey whole, as their large mouths have no teeth. The king threadfin can attain 170 cm (67 in.) in length, with a mass of up to 45 kg. (99 lbs.), while the blue threadfin rarely reaches 100 cm (39 in.). Threadfin salmon are protandrous hermaphrodites, meaning they are all firstly active males then grow into functional females. Both species form loose groups in suitable areas and, if possible, there is a general movement upstream in winter.

Threadfin salmon are favoured by sport anglers as they fight well, are said to taste excellent, and are often around and feeding when other, often more obvious or even preferred, species are not active. In addition, they often congregate in schools, so if one threadfin salmon bites, chances are more will follow. In the sheltered inshore and estuarine environments, boat or shore fishing can often work well. In terms of equipment, most anglers employ a medium to strong spinning gig with a good fixed-spool reel and medium strength braid. Fly fishing can be hard, as the threadfin salmon prefers turbid water and feeds mostly by “feel”. This species can be caught with equal success both at daytime and at night. In many areas lure fishing, using plastics or hard lures, is popular, easy and productive. Recovery of the lure should be at medium to slow speeds so that the lure is close to, or on, the bottom. When boat fishing, the lure should be worked slowly and strongly very close to the seabed. Threadfin are strong fighters, and can also be large, so strong equipment will assist in holding a good fish away from cover and improve your chances of landing it. A wire leader is not essential, as their mouths are soft. As the threadfin salmon usually gulps its food whole, the angler should be always on the alert for a sudden strike.