Australia has two species of threadfin salmon, the blue threadfin (Eleutheronema tetradactylum) and king threadfin (Polydactylus macrochir), also known as blue salmon and king salmon, respectively. They are fast-growing predatory fishes that feed on small fishes, prawns and other crustaceans and are found in waters ranging from Brisbane on the east coast, north all along the coastline and extending down the West Australian coast.

Both species of threadfin are members of the family Polynemidae, a group of fishes adapted to life in muddy water. They have small eyes but have also evolved specialised long, thread-like “free sensory filaments” at the base of each pectoral fin, from which the name “threadfin” arises. There are two separate pale brown dorsal fins, vivid yellow pectoral and pelvic fins and a large, forked tail.

Threadfins, although tolerant of salinity changes, are essentially marine fish. They can be caught throughout the year in river mouths and inshore habitats and will move into the uppermost tidal sections of rivers.

Whilst the king threadfin can live for 22 years and reach 170cm and a maximum published weight of 45 kilograms, the blue threadfin lives for approximately eight years and can reach 100 cm.

Rods, reels and flies suitable for barramundi fishing are recommended and threadfin salmon are usually caught when barra fishing rather than as a targeted species. However should you catch a threadfin take note of the location and the state of the tide as it is likely that they will return to that spot when similar conditions occur.

Threadfin – and their prey – are influenced by the tide. As the tide starts to drop threadfin patrol the drop-offs, gutters and holes ready to ambush bait forced back off the flats. The best time of year is during the dry season when there is little flow in the rivers of tropical Australia as threadfin and other predators are often more concentrated around the lower reaches. The best tides are those with the greatest movement, which are known as the spring tides.

“Threadies” are famous for frustrating fishermen when they are seen feeding on jelly prawns in the shallows and refuse any offerings cast their way. Don’t waste precious fishing time when this occurs, ignore them and pursue another species.

Both the blue and the king threadfin salmon are great sportfish. That large powerful tail means they can be very hard to stop and are capable of long blistering runs when hooked.