Large, slim shark with moderately large eyes. Long rounded snout. Origin of first dorsal fin behind the free rear tips of the pectoral fins. Interdorsal ridge present.
Coloration
Dark grey, grey brown or bronze brown upper body, sometimes nearly blackish, white ventral surface. The tip of the first dorsal fin is dusky but not black-tipped. Inconspicuous white band on flank.
Distribution
Probably world-wide in oceanic and coastal areas (prefers temperatures between 23 and 24° Celsius). Western Atlantic: Massachusetts to southern Brazil, including Gulf of Mexico and the Caribbean. Eastern Atlantic: Madeira, Senegal to northern Angola. Indian Ocean: Madagascar, Mozambique, Tanzania, Comores, Maldives, Sri Lanka, and the Red Sea. Western Pacific: Thailand, the Philippines, New Caledonia, New Zealand, Australia and China. Central and eastern Pacific: Hawaiian Islands, southern Baja California to Peru.
Biology
An abundant offshore species. It is occasionally found inshore where the water is as shallow as 18 m,; in the open ocean it occurs from the surface down to at least 500 m depth. It is an active, quick-moving, often aggressive shark, but is subordinate to the more sluggish but stubbornly persistent Oceanic whitetip shark. Together with the Blue shark they are probably the three most abundant sharks in oceanic waters. Population dynamics and structure are poorly known but there is a size segregation, with young occurring on offshore nursery areas and adults seaward from them.
Diet
Feeds preferably on pelagic fish species (mullets, mackerels, yellowfin tunas, albacore). Due to the damage it does to fishing nets, the spinner shark is often called the "net-eater shark".
Size
Average size between 200 and 240 cm, maximum about 330 cm.
Reproduction
Viviparous species, with yolksac-placenta. 2 to 14 pups per litter. Size at birth about 70 to 85 cm. Pups show a fast growth rate, and are born in open waters. Males mature with a size between 185 cm and 215 cm, females between 215 and 230 cm.
Similar Species
Similar species are known, making them difficult to identify but a distinguishable feature is the origin of the first dorsal fin that is behind the free rear tips of the pectoral fins.
Vulnerability
Category:Vulnerable (VU) Criteria:A2bd Last evaluated:2021 Trend:
Silkies are generally regarded as dangerous or potentially dangerous to people, mainly due to the their size and abundance offshore, although no attacks have been attributed to them. When approached by divers, individuals have been seen to perform a "hunch" display, with back arched, head raised and caudal fin lowered, possibly as a defensive threat display.
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