About Polydactylus quadrifilis (Cuvier, 1829)
The giant African threadfin (Polydactylus quadrifilis) is a large species of threadfin that matches its common name, reaching a maximum total length of 200 centimetres (79 in), while more commonly growing to 150 centimetres (59 in). This fish has a pointed snout and an almost straight dorsal profile on its head. It has two separate dorsal fins: the first dorsal fin has eight spines, with the second spine thicker than the other spines, and the second dorsal fin has one spine and thirteen soft rays. The anal fin has three spines and eleven soft rays, and its base is approximately the same length as the base of the second dorsal fin. The pectoral fin has twelve or thirteen unbranched rays, and its length measures 20 to 24% of the fish’s standard length; its tip does not reach as far as the tip of the pelvic fin. There are four pectoral filaments, with the first being the shortest. The first three filaments extend past the origin of the pelvic fin, but do not reach as far as its tip. The fourth pectoral filament is the longest, at 27 to 39% of the fish’s standard length, and reaches at least the tip of the pelvic fin. The caudal fin is deeply forked and has long, non-filamentous lobes. The simple lateral line has 70 to 71 pored scales, and runs from the upper end of the gill slit to the upper end of the lower lobe of the caudal fin. The head and upper flanks are silver with a blackish tint, lower flanks are paler, and the breast and belly are white. The snout is semi-transparent. The dorsal fins and caudal fin are pale with blackish rear margins. The pectoral fin is bright yellow, and the pectoral filaments are white. The pelvic and anal fins are dusky, with white coloring on their front edges and at their bases. The giant African threadfin was first formally described by Georges Cuvier in the volume Histoire naturelle des poissons. Tome troisième. Suite du Livre troisième. Des percoïdes à dorsale unique à sept rayons branchiaux et à dents en velours ou en cardes, co-authored with Achille Valenciennes. Cuvier originally named the species Polynemus quadrifilis, and the given type locality is Senegal. The giant African threadfin is distributed in the tropical eastern Atlantic Ocean, along the coast of western Africa from Senegal to the Congo. There is only one recorded sighting from Mauritania. This fish lives in shallow coastal waters with sandy and muddy bottoms, and is occasionally found in brackish waters. It can enter estuaries, and is rarely caught in fresh water; only the largest individuals are recorded exclusively from marine waters. This carnivorous fish eats crustaceans and fishes.
