A threadfin is a type of fish that primarily lives in shallow waters and is found in regions with a range of salt concentrations. The fish typically grow to between 8 inches (20 cm) and 80 inches (200 cm) in length and have a grey color. There are a number of species of the Polynemidae family which are called threadfins, so there is some variation in size and color. The fish’s distinguishing feature is its pectoral fins, which are split into two separate parts.
Threadfin fish are usually found in subtropical oceans. The fish’s ability to survive in water with a range of different salt concentrations means that it is also found in rivers and lakes. They usually live in shallow waters with sand or mud bottoms.The threadfin is able to find prey in the sand or mud using its split pectoral fin.
Typically, threadfin fish are silvery grey in color. The length of the fish depends on the exact species. For example, the four-fingered species can grow up to 80 inches (200 cm), although not all specimens reach this size.
In total, there are around 40 species of threadfin. Some species include the Australian, Eightfinger and Persian blackspot threadfin. The giant African threadfin, as the name suggests, is one of the largest species, and can live in both fresh and salt water. The Atlantic species is much smaller and typically grows to around 9 inches (23 cm) in length.
The species usually eats other small fish. Many species will also consume crustaceans. There is some variety in diet between species, however. For example, the King threadfin lives mainly off prawns and other fish.
Unlike most other fish, their pectoral fins are split into two parts. Pectoral fins are small and located on both sides of the fish. The bottom section of the fins are split further into long, thin rays, which is where the fish get their name. These rays can often be long enough to pass behind their tail and, as noted, are thought to be used by threadfins to find food among sand and other types of sediment.
The fish are known to form large schools. This means that they are popular targets for commercial fishermen, as it is easy to catch them in large numbers. Threadfins are used as food for other fish in fisheries, but certain species can be eaten by humans. The fish are also popular among anglers.