Silvertip Shark, Carcharhinus Albimarginatus
Carcharhinus albimarginatus (Rüppell, 1837) CARCH Carch 17
Carcharias albimarginatus Rüppell, 1837, Neues Wirbel.Fauna Abyssinien, Fische Rothen Meeres, (11):64, pl. 18, fig. 1.
Lectotype: Naturmuseum Senckenberg, SMF 3582, 1025 mm stuffed immature male, designated by Klausewitz (1960:293).
Type Locality: Ras Mehomet, Red Sea.
Synonymy: Eulamia (Platypodon) platyrhynchus Gilbert, 1892.
Other Scientific Names Recently in Use: Carcharhinus platyrhynchus (Gilbert, 1892).
FAO Names: En – Silvertip shark; Fr – Requin pointe blanche; Sp – Tiburón de puntas blancas.
Field Marks: A large, dark grey shark with strikingly conspicuous white tips and posterior margins on all fins, pectoral fins narrow tipped, first dorsal apex narrowly rounded or pointed.
Diagnostic Features: A large, fairly slender species (up to about 2.7 m). Snout moderately long and broadly rounded; internarial width 1 to 1.4 times in preoral length; eyes circular and moderately large, the length 1.8 to 3% of total length; anterior nasal flaps low and poorly developed; upper labial furrows short and inconspicuous; hyomandibular line of pores just behind mouth corners not conspicuously enlarged; gill slits short, the third 2.5 to 3.5% of total length and less than a third of first dorsal base; usually 13/12 rows of anteroposterior teeth in each jaw half, but varying from 12 to 14/12 to 14; upper teeth with moderately, broad, strongly serrated, erect to moderately oblique, triangular, high cusps, and crown feet with slightly coarser serrations or low cusplets; lower teeth with erect, fairly broad serrated cusps and transverse roots. An interdorsal ridge present. First underside of head upper and lower dorsal fin moderately large and se semifalcate, with pointed tooth or narrowly rounded apex and posterior margin curving ventrally from fin apex; origin of first dorsal fin usually over or slightly anterior to pectoral rear tips; inner margin of first dorsal moderately short, 2/5 dorsal base or less; second dorsal fin moderately large and high, its height 1.5 to 2.3% of total length, its inner margin moderately long and 1.5 to 2.1 times height; origin of second dorsal over or slightly behind anal origin; pectoral fins large and semifalcate, with narrowly rounded or pointed apices, length of anterior margins about 16 to 22% of total length; 216 to 231 total vertebral centra, 115 to 125 precaudal centra. Colour dark grey above, sometimes with a bronze tinge, white below; all fins with conspicuous white tips and posterior margins; an inconspicuous white band on flank.
Geographical Distribution: Western Indian Ocean: Red Sea, South Africa, Mozambique, Kenya, Madagascar, Aldabra group, Mauritius, Seychelles, Chagos Archipelago. Western central Pacific: Indonesia, (Macassar Straits), Taiwan Island, Guam New Caledonia, The Philippines, Palau, Marshall, Solomon and Phoenix Islands, Tahiti. Eastern Pacific: Southern Baja California, Revillagigedo, Clipperton, Cocos and Galapagos Islands south to Guatemala and Colombia. ? Western North Atlantic: ? Mexico, Gulf of Mexico and Caribbean Sea.
Habitat and Biology: A common to abundant, coastal-pelagic tropical, inshore and offshore shark, over or adjacent to continental and insular shelves and offshore banks, from the surface to 600 to 800m depth. The silvertip shark has a strong preference for offshore islands, coral reefs and banks although it is not limited to them. It occurs from inside lagoons and near dropoffs to well offshore, but is not truely oceanic. It occurs along the water column from the surface to the bottom, and will often follow boats at the surface. Young silvertip sharks are restricted to shallower water closer to the shore while adults are more wide ranging, with little overlap with the young.
Viviparous, with a yolk-sac placenta; number of young 1 to 11 per litter, often 5 or 6. Young are born in the summer after a gestation period of about a year.
Feeds on a variety of midwater and bottom fishes, including lanternfish, flyingfish, gempylids, tuna, bonito, wahoo, bananafish, wrasses, soles, eagle rays, and octopi. At baits it is described as being more aggressive than Carcharhinus galapagensis and C. limbatus, with equal-sized silvertips dominating the Galapagos and blacktip sharks. It may swim at the periphery of a group of feeding sharks of other species, but suddenly dashes in to take some food. Individuals of this species are said to be very aggressive to one another, and individuals often have evidence of combat scars. This species is regarded as dangerous to people, although few if any attacks can be attributed to it. Its large size, abundance around reefs and offshore islands, and boldness should invite respect and caution. A baited experiment in which a dummy dressed as a SCUBA diver had its leg removed by a large silvertip (Costeau & Costeau, 1970) suggests that it might be capable of fatally injuring a diver, especially when a food stimulus is in the water.
Size: Maximum about 300 cm, males maturing between 160 and 180 cm, females maturing between 160 and 199 cm; size at birth about 63 to 68 cm.
Interest to Fisheries: Specific information on fisheries for this species are lacking, but it is presumably taken in areas where it occurs (especially off the islands of the western Indian Ocean where it is abundant).
Literature: Beebe & Tee-Van (1941); Fourmanoir (1961); Wheeler (1962); Garrick & Schultz (1963); Limbaugh (1963); Gohar & Mazhar (1964); Kato, Springer & Wagner (1967); Kato & Carvallo (1967); Garrick (1967, 1982); Costeau & Costeau (1970); Bass, D’Aubrey & Kistnasamy (1973); Johnson (1978).
From FAO SPECIES CATALOGUE
Vol.4. Sharks of the world
An annotated and illustrated catalogue of shark species known to date