Common Blacktip Shark

The blacktip shark has a robust, streamlined body with a long, pointed snout and relatively small eyes. The five pairs of gill slits are longer than those of similar requiem shark species. The jaws contain 15 tooth rows on either side, with two symphysial teeth (at the jaw midline) in the upper jaw and one symphysial tooth in the lower jaw. The teeth are broad-based with a high, narrow cusp and serrated edges. The first dorsal fin is tall and falcate (sickle-shaped) with a short, free rear tip; no ridge runs between the first and second dorsal fins. The large pectoral fins are falcate and pointed. The coloration is gray to brown above and white below, with a conspicuous white stripe running along the sides. The pectoral fins, second dorsal fin, and the lower lobe of the caudal fin usually have black tips. The pelvic fins and rarely the anal fin may also be black-tipped. The first dorsal fin and the upper lobe of the caudal fin typically have black edges. Some larger individuals have unmarked or nearly unmarked fins. Blacktip sharks can temporarily lose almost all their colors during blooms, or "whitings", of coccolithophores. This species attains a maximum known length of 2.8 m (9.2 ft), though a length of 1.5 m (4.9 ft) is more typical, and a maximum known weight of 123 kg (271 lb).

The blacktip shark has a worldwide distribution in tropical and subtropical waters. In the Atlantic, it is found from Massachusetts to Brazil, including the Gulf of Mexico and the Caribbean Sea, and from the Mediterranean Sea, Madeira, and the Canary Islands to the Democratic Republic of the Congo. It occurs all around the periphery of the Indian Ocean, from South Africa and Madagascar to the Arabian Peninsula and the Indian subcontinent, to Southeast Asia. In the western Pacific, it is found from the Ryukyu Islands of Japan to northern Australia, including southern China, the Philippines, and Indonesia. In the eastern Pacific, it occurs from Southern California to Peru. It has also been reported at a number of Pacific islands, including New Caledonia, Tahiti, the Marquesas, Hawaii, Revillagigedo, and the Galápagos. Most blacktip sharks are found in water less than 30 m (98 ft) deep over continental and insular shelves, though they may dive to 64 m (210 ft). Favored habitats are muddy bays, island lagoons, and the drop-offs near coral reefs; they are also tolerant of low salinity and enter estuaries and mangrove swamps. Although an individual may be found some distance offshore, blacktip sharks do not inhabit oceanic waters. …

The blacktip shark is an extremely fast, energetic predator that is usually found in groups of varying size. Segregation by sex and age does not occur; adult males and nonpregnant females are found apart from pregnant females, and both are separated from juveniles. In Terra Ceia Bay, Florida, a nursery area for this species, juvenile blacktips form aggregations during the day and disperse at night. They aggregate most strongly in the early summer when the sharks are youngest, suggesting that they are seeking refuge from predators (mostly larger sharks) in numbers. Predator avoidance may also be the reason why juvenile blacktips do not congregate in the areas of highest prey density in the bay. Adults have no known predators. Known parasites of the blacktip shark include the copepods Pandarus sinuatus and P. smithii, and the monogeneans Dermophthirius penneri and Dionchus spp., which attach the shark's skin. This species is also parasitized by nematodes in the family Philometridae (genus Philometra), which infest the ovaries.

Behaviour. Like the spinner shark, the blacktip shark is known to leap out of the water and spin three or four times about its axis before returning. Some of these jumps are the end product of feeding runs, in which the shark corkscrews vertically through schools of small fish, and its momentum launches it into the air. …