Manta Survey at Komodo National Park
Whitetip Reef Shark
The whitetip reef shark (Triaenodon obesus) is a species of requiem shark, family Carcharhinidae, and the only member of its genus. A small shark usually not exceeding 1.6 m (5.2 ft) in length, this species is easily recognizable by its slender body and short but broad head, as well as tubular skin flaps beside the nostrils, oval eyes with vertical pupils, and white-tipped dorsal and caudal fins. One of the most common sharks found on Indo-Pacific coral reefs, the whitetip reef shark occurs as far west as South Africa and as far east as Central America. It is typically found on or near the bottom in clear water, at a depth of 8–40 m (26–131 ft). During the day, whitetip reef sharks spend much of their time resting inside caves. Unlike other requiem sharks, which rely on ram ventilation and must constantly swim to breathe, this shark can pump water over its gills and lie still on the bottom. At night, whitetip reef sharks emerge to hunt bony fishes, crustaceans, and octopus in groups, their elongate bodies allowing them to force their way into crevices and holes to extract hidden prey. Individuals may stay within a particular area of the reef for months to years, time and again returning to the same shelter. This species is viviparous, in which the developing embryos are sustained by a placental connection to their mother. One of the few sharks in which mating has been observed in the wild, receptive female whitetip reef sharks are followed by prospective males, which attempt to grasp her pectoral fin and maneuver the two of them into positions suitable for copulation. Females give birth to one to six pups every other year, after a gestation period of 10–13 months. Whitetip reef sharks are rarely aggressive towards humans, though they may investigate swimmers closely. However, spear fishers are at risk of being bitten by one attempting to steal their catch. This species is caught for food, though ciguatera poisoning resulting from its consumption has been reported. The IUCN has assessed the whitetip reef shark as Near Threatened, noting its numbers are dwindling due to increasing levels of unregulated fishing activity across its range. The slow reproductive rate and limited habitat preferences of this species renders its populations vulnerable to overfishing.
Blacktip Reef Shark
Not to be confused with the blacktip shark, Carcharhinus limbatus. The blacktip reef shark (Carcharhinus melanopterus) is a species of requiem shark, family Carcharhinidae, easily identified by the prominent black tips on its fins (especially on the first dorsal fin and the caudal fin). Among the most abundant sharks inhabiting the tropical coral reefs of the Indian and Pacific Oceans, this species prefers shallow, inshore waters, and its exposed first dorsal fin is a common sight in the region. Most blacktip reef sharks are found over reef ledges and sandy flats, though they have also been known to enter brackish and freshwater environments. This species typically attains a length of 1.6 m (5.2 ft). Blacktip reef sharks have extremely small home ranges and exhibit strong site fidelity, remaining within same local area for up to several years at a time. They are active predators of small bony fishes, cephalopods, and crustaceans, and have also been known to feed on sea snakes and seabirds. Accounts of the blacktip reef shark's life history have been variable and sometimes contradictory, in part reflecting geographical differences within the species. Like other members of its family, this shark is viviparous with females giving birth to two to five young on a biennial, annual, or possibly biannual cycle. Reports of the gestation period range from 7–9, to 10–11, to possibly 16 months. Mating is preceded by the male following closely behind the female, likely attracted by her chemical signals. Newborn sharks are found further inshore and in shallower water than adults, frequently roaming in large groups over areas flooded by high tide. Timid and skittish, the blacktip reef shark is difficult to approach and seldom poses a danger to humans unless roused by food. However, people wading through shallow water are at risk of having their legs mistakenly bitten. This shark is used for its meat, fins, and liver oil, but is not considered to be a commercially significant species. The International Union for Conservation of Nature has assessed the blacktip reef shark as Near Threatened. Although the species as a whole remains widespread and relatively common, overfishing of this slow-reproducing shark has led to its decline at a number of locales.