SHARK GALLERY

Silky Shark(Carcharhinus falciformis)

Silky Shark - Carcharhinus falciformis

Ian K Fergusson

(Bibron, 1839).

Fr: Requin soyeux
Sp: Tiburon jaqueton
It: N/A
Ma: N/A

Diagnosis

A large, somewhat slender shark with a moderately long and slightly pointed snout; narrow interdorsal ridge.  Eyes round and quite large.  First dorsal fin small (height ca. 5.2-10% of TL) with a curved apex, origin posterior to the rear corner of the pectoral fins; second dorsal fin noticeably small and low, with its origin slightly ahead of the anal fin, and a long free rear tip over twice as long as the fin height.  Pectoral fins quite large but slender, with their anterior margins measuring ca. 14.2 to 22% of TL and narrowly-rounded or pointed apices.  Upper-teeth essentially triangular, becoming more oblique rearwards, strongly serrated and deep indentations on the rearward edges; crown feet with coarser serrations.  Colour dark bronzy-grey or mid-grey dorsally, fading to white ventrally with a poorly-defined white band on the belly-flanks; fin-tips (with exception of 1st dorsal) rather dusky.

Size

To 330 cm TL; usually to 300 cm;  size at birth ca. 70 to 87 cm.

Status and Distribution

Mediterranean Sea: Rare or occasional; apparently as an Atlantric vagrant into the Western Mediterranean, where it occurs in the zone from Gibraltar immediately eastwards.  Infrequently taken at Gulf of Chafarinas (Morocco) and neighbouring sites (to Algeria?); possibly more cosmopolitan, at least in the Alboran Sea, than current records infer (preserved jaws of this species examined by I.K. Fergusson at Favignana, Sicily).  Not yet definitively recorded from Sicilian Channel but a likely addition, given the presence of other oceanic Atlantic vagrants such as C. obscurus  and Alopias superciliosus, and quite likely to be recorded throughout the deeper, warmer zones of the Mediterranean basins.

Biology

Poorly-known within the Mediterranean.  An epipelagic or semipelagic, oceanic and littoral shark found in warm-temperate and tropical seas within the influence of land masses or islands, from the surface to at least 500m; usually far from the coast over continental or insular shelves; also at offshore banks, but sometimes occurring nearer to shore over deep blue waters and even over depths as little as 18 m.  This species is apparently more prone to making inshore excursions than its pelagic relatives, Carcharhinus longimanus and Prionace glauca, and may be less well adapted to a truly oceanic lifestyle.  Silky sharks are active, fast-moving predators  of a variety of bony fish, including tunas (with which they are commonly associated) and other scombroids; also mullet and other coastal species; squid, pelagic crabs and octopi.  Segregation by size occurs, with younger sharks nearer to shore.   In the Western Atlantic, pupping-zones occur over depths of 80-100 m.  Litter size is 2 to 14 pups (average litter varies geographically), with no defined breeding-season.  Males mature at 187-217 cm,  females at 213-230 cm.

The Shark Trust, 36 Kingfisher Court, Hambridge Road, Newbury, Berkshire, RG14 5SJ, UK.
Tel(+44) 01635 551150, Fax(+44) 01635 550230



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