The silky shark (Carcharhinus falciformis) is a species of requiem shark, family Carcharhinidae, named for the smooth texture of its skin. It is one of the most abundant sharks in the pelagic zone, and can be found around the world in tropical waters. Highly mobile and migratory, this shark is most often found over the edge of the continental shelf down to a depth of 50 m (164 ft). The silky shark has a slender, streamlined body and typically grows to a length of 2.5 m (8 ft 2 in). It can be distinguished from other large requiem sharks by its relatively small first dorsal fin with a curving rear margin, its tiny second dorsal fin with a long free rear tip, and its long, sickle-shaped pectoral fins. It is a deep, metallic bronze-gray above and white below.

With prey often scarce in its oceanic environment, the silky shark is a swift, inquisitive, and persistent hunter. It feeds mainly on bony fishes and cephalopods, and has been known to drive them into compacted schools before launching open-mouthed, slashing attacks. This species often trails schools of tuna, a favored prey. Its sense of hearing is extremely acute, allowing it to localize the low-frequency noises generated by other feeding animals, and, by extension, sources of food. The silky shark is viviparous, meaning that the developing embryos are sustained by a placental connection to their mother. There is significant geographical variation in its life history details. Reproduction occurs year-round except in the Gulf of Mexico, where it follows a seasonal cycle. Females give birth to litters of up to 16 pups annually or biennially. The newborn sharks spend their first months in relatively sheltered reef nurseries on the outer continental shelf, growing substantially before moving into the open ocean.

The large size and cutting teeth of the silky shark make it potentially dangerous, and it has behaved aggressively towards divers. However, attacks are rare as few humans enter its oceanic habitat. Silky sharks are valued for their fins, and to a lesser extent their meat, hide, liver oil, and jaws. Because of their abundance, they form a major component ofcommercial and artisanal shark fisheries in many countries. Furthermore, their association with tuna results in many sharks being taken as bycatch in tuna fisheries. Although slow-reproducing like most other sharks, the wide distribution and large population size of the silky shark was once thought to buffer the species against these fishing pressures. However, data now suggest that silky shark numbers are declining around the world, which prompted the International Union for Conservation of Nature (IUCN) to reassess itsconservation status from Least Concern to Near Threatened in 2007.

Amany Esmail