Author: (Quoy and Gaimard, 1824)
Field Marks:
A moderate-sized, brownish 'grey shark' with a short, bluntly rounded snout, horizontally oval eyes, no interdorsal ridge, a moderately large second dorsal with a short rear tip, and brilliant black blotches on the first dorsal apex, lower caudal lobe, and black tips on other fins.
Diagnostic Features:
A fairly stocky species (most adults less than 1.6 m). Snout short and bluntly rounded; internarial width 0.9 to 1.1 times in preoral length; eyes usually horizontally oval and fairly large, their length 2 to 3% of total length; anterior nasal flaps moderately elongated and expanded as nipple-shaped lobes; upper labial furrows short and inconspicuous; hyomandibular line of pores just behind mouth corners not conspicuously enlarged; gill slits moderate-sized, the third 2.6 to 4.2% of total length and less than a third of first dorsal base; usually 12/11 rows of anteroposterior teeth in each jaw half but varying from 11 to 13/10 to 12; upper teeth with narrow, strongly serrated, erect to oblique, high cusps, and crown feet with coarser serrations and cusplets; lower teeth with erect to oblique, narrow serrated cusps and transverse roots. No interdorsal ridge. First dorsal fin large and falcate, with a rounded apex and posterior margin curving ventrally from fin apex; origin of first dorsal fin usually over pectoral free rear tips; inner margin of first dorsal moderately long, slightly more or less than half dorsal base; second dorsal fin large and high, its height 3.4 to 4.1% of total length, its inner margin short and 0.8 to 1.1 times its height; origin of second dorsal over anal origin; pectoral fins moderately large, narrow and falcate, with narrowly rounded or pointed apices, length of anterior margins about 17 to 19% of total length; 193 to 214 total vertebral centra, 111 to 122 precaudal centra. Colour usually light brown above, white below; first dorsal and ventral caudal lobe with a conspicuous black apical blotch, brilliantly highlighted proximally with white; other fins, generally with less prominent black fin tips; a conspicuous white band on flank.
Geographical Distribution:
Eastern Mediterranean Sea (apparently as an invader through the 7 Suez Canal from the Red Sea). Indian Ocean: South Africa, Mauritius, Scychelles, and Madagascar to Red Sea, the "Gulf", Pakistan, India, Sri Lanka, Andaman and Maldive Islands. Western Pacific:. Thailand (Gulf of Thailand) to China (including, Taiwan Province), Japan, The Philippines, Australia (Queensland, Northern Territory and Western Australia), and New Caledonia. Wide-ranging in the island groups of the western central Pacific, from the Hawaiian and Marshall Islands south to the Tuamotu Archipelago. Apparently rare or absent in more easterly groups including the Marquesas, Pitcairn, Tubuai (Rapa) Islands, Austral Ridge, Johnston, Marcus and Easter Islands.
Habitat and Biology:
This small, common, wide-ranging tropical Indo-Pacific shark prefers shallow water close inshore on coral reefs, at depths of only a few metres and commonly in the intertidal zone, often on reef flats in water 30 cm deep or less; also found near reef dropoffs and occasionally close offshore. This is one of the three commonest sharks on coral reefs in tropical Oceania (the other two being the whitetip reef shark, Triaenodon obesus, and the grey reef shark, C. amblerhynchos. It apparently now inhabits warmer parts of the Mediterranean Sea, having invaded it through the Suez Canal. It is thought to penetrate into at least brackish lakes and estuaries in Madagascar and into fully fresh water in Malaysia, but its ability to tolerate fresh water for any length of time is uncertain; whatever the case, it apparently is not able to utilize fresh water to the extent that Carcharhinus leucas does. At the northern and southern extremes of its range the blacktip may be a migrant, but this is uncertain.
The blacktip reef shark is an active, strong-swimming shark, found near the bottom and at midwater in deeper water, and with its dorsal fins protruding in the shallows. It occurs singly or in small groups or aggregation, but is not strongly schooling.
Viviparous, with a yolk sac placenta; number of young 2 to 4, usually 4. Gestation period possibly 16 months, with birth season from late winter to early summer.
Eats small fish and invertebrates, including mullet, groupers, theraponids, jacks, mojarras, slipjaws, wrasses, surgeonfish, sillaginids, cuttlefish, squid, octopi, shrimp, and manis shrimp. Not an extremely dangerous species because of its small size and general timidity when approached by divers in unbaited situations, but definitely a hazard to spearfishers and to people wading in the water. It is often quite inquisitive when divers enter the water, but can be usually driven off. It often becomes aggressive when speared fish are about, which may be exacerbated by the presence of competing sharks, and will rush in to take wounded fish or baits, although in general it is less aggressive in this sort of activity than the grey reef shark (Carcharhinus amblyrhynchos). It must be ranked as a dangerous species because it is the shark most commonly encountered by people in the tropical Indo-Pacific, and has definitely been responsible for several unprovoked and provoked attacks on people (none fatal and most without major injury to people). Its danger is somewhat qualified by the nature of its attacks, primarily on people wading in shallow water. Most blacktip attacks appear to be 'mistaken identity' attacks, made on the legs of people the shark may be mistaken for its ordinary small, non-mammalian prey. Randall and Helfman (1973) mote that Marshall Islanders swim rather than wade across shallow island passes to avoid blacktip attacks on their legs, and suggest that people who see an approaching blacktip while wading in shallow water and have nothing to defend themselves with should consider submerging as much of their body as possible to scare off the shark.
Enemies of this species include large groupers and probably other sharks.
Size:
Maximum less than 200 cm, one specimen reported as 180 cm (an unusually large adult male), but most adults less than 160 cm; males maturing at 91 to about 100 cm and reaching 180 cm (most adult males up to 134 cm), females maturing between 96 and 112 cm and reaching 131 cm; size at birth between 33 to 52 cm.
Interest to Fisheries:
Apparently regularly caught in fisheries where this common inshore shark occurs, including off of India and Thailand; but details of its utilization and gear used are lacking.
Remarks:
Carcharias playfairi is synonymized with this species following Bass, D'Aubrey and Kistnasamy (1973). See Boeseman (1960) and Garrick (1982) for the nomenclatural history of Squalus commersoni.
Type material:
Holotype: Museum National d'Histoire Naturelle, Paris, MNHN 1129, 590 mm immature male. Type Locality: Waigeo Islands.