Whitetip Reef Shark
This smaller, shy shark has a long, thin frame and a frowning, almost grumpy look on its face. It has distinct white tips on its dorsal and caudal (tail) fins, but otherwise is a dark gray-brown that fades to light on its underside. This is one of the few requiem sharks that doesn’t have to keep swimming to breathe, and during the day it rests still on the sandy reef bottom or in caves, usually in groups. At night, the whitetip reef shark comes out to hunt sleeping fish, easily picking them out of crevices. Although it is curious around humans, it is considered a low threat, only becoming aggressive when provoked or when feeding.
Order – Carcharhiniformes
Family – Carcharhinidae
Genus – Triaenodon
Species – obesus
English language common names include whitetip reef shark, blunthead shark, blunt-head shark, light-tip shark, reef whitetip, reef whitetip shark, white tip reef shark, white-tip reef shark, whitetip shark, and white-tip shark. Common names in other languages include aileron blanc de lagon (French), arava (Tuamotuan), cazón (Spanish), cazón coralero trompacorta (Spanish), daaha (Somali), endormi requin (French), eno-eno (Gela), faana miyaru (Maldivian), gursh (Arabic), ikan yu (Malay) libaax (Somali), maog (Niuean), malu (Samoan), mamaru (Tahitian), manô lâlâ kea (Hawaiian), marracho de covas (Portuguese), miyaru (Maldivian), mweshar (Carolinian), nemuribuka (Japanese), pako korak (Marshallese), papa (Swahili), papa sarawanzi (Swahili), pating (Tagalog), peu (Carolinian), requin à pointes blanches (French), requin corail (French), riffhai (German), stompkophaai (Afrikaans), te alabafrnua (Tuvaluan), te bakoa (Kirabati), tintorera punta aleta blanca (Spanish), valkoevähai (Finnish), weißspitzenhundshai (German), and witpuntrifhaai (Dutch).
Importance to Humans
The whitetip reef shark is fished in the waters off Pakistan, India, Sri Lanka, and Madagascar. Although data on the commercial fishery involving this shark are lacking, it is also probably fished in other waters throughout its range. It is caught with floating and bottom gillnets and longlines. The liver and flesh is marketed for human consumption, although it has been reported to cause ciguatera poisoning.
Danger to Humans
This shark is relatively harmless to humans due to its easygoing disposition and small teeth. It avoids close contact with humans, swimming off when approached by swimmers and divers. Often attracted to food, divers have been able to hand feed individual whitetip reef sharks. However, on occasion, a shark will become overly excited by spearfishing or when bait is present, resulting in a bite to a diver. This species is also known to bite if harassed.
In Hawaii, some families regarded this shark as ‘aumakua’, a guardian spirit. They would feed rather than hunt whitetip reef sharks.
The whitetip reef shark is currently listed by the World Conservation Union (IUCN) as “Near Threatened” at this time.
The IUCN is a global union of states, governmental agencies, and non-governmental organizations in a partnership that assesses the conservation status of species. Due to restricted habitat and depth range as well as small litter size and late age at maturity, this shark may become threatened with increasing fishing pressure.
The whitetip reef shark has a wide range in the Pacific Ocean, including South Africa and the Red Sea to Pakistan, Sri Lanka, Burma, Indonesia, Vietnam, Taiwan, Riu Kiu Islands, Philippines, Australia and New Guinea. It is common in Polynesia, Melanesia, and Micronesia, northward to the Hawaiian Islands, and southwest to the Pitcairns. In the eastern Pacific, the whitetip reef shark resides in waters off the Cocos and Galapagos Islands, and Panama north to Costa Rica. It is one of the most common reef sharks in the Pacific Ocean, along with the blacktip reef shark (Carcharhinus melanopterus) and the grey reef shark (Carcharhinus amblyrhynchos).
The whitetip reef shark typically lives along the bottom in clear, shallow waters surrounding coral reefs. It has been reported at depths to 1,083 feet (330 m). Rarely coming to the surface, this shark is capable of lying motionless on the bottom substrate for long periods of time. During daylight hours, whitetip reef sharks form aggregations in caves, sometimes appearing stacked up like a pile of logs. The same sharks often return repeatedly to the same cave for long periods of time, changing location only periodically. The whitetip reef shark is most active throughout the night. Site fidelity is strong with each shark maintaining a small home range for months or years at a time.
This small shark is relatively slender with a broad flattened head. The snout is broadly rounded and eyes are horizontally oval. Along with a down-slanted mouth, the prominent brow ridges give this shark a permanent “disgusted” expression to its face. The first dorsal fin originates well behind the free rear tips of the pectoral fins. The second dorsal fin is large, but smaller than the first dorsal. The pectoral fins are broad and triangular in shape. The anal fin is about as large as the second dorsal fin. There is no interdorsal ridge and lateral keels on the caudal penduncle are lacking.
The whitetip reef shark earns its common name for the distinct white tips on the first dorsal and upper caudal fins. The body is dark gray to brownish, fading to a light ventral surface. Small dark spots may be present over the entire body. The remaining fins may also have white tips, however this may not always hold true.
There may arise some confusion between the whitetip reef shark and the silvertip shark (C. albimarginatus). The silvertip shark is a much heavier species with a large first dorsal and a much smaller second dorsal fin. Also, its caudal fin is lined with white rather than tipped as in the whitetip reef shark.
The tricuspid teeth each have one large triangular cusp in the middle along with two smaller ones on either side.
Size, Age, and Growth
The whitetip reef shark grow to a maximum length of just under 7 feet (2.13 m), however individuals are rare at lengths over 1.6 m (5.25 feet). Males mature at about 3.4 feet (1.05 m) and generally reach 5.5 feet (1.68 m) in length. Females reach maturity at 3.4-3.57 feet (1.05-1.09 m) and grow to at least 5.18 feet (1.58 m). This species is known to reach a maximum age of at least 25 years.
This shark is a specialist in capturing bottom-dwelling prey in caves and crevices, feeding primarily on octopus, lobsters and crabs. It also feeds on bony fishes including eels, squirrelfishes, snappers, damselfishes, parrotfishes, surgeonfishes, and triggerfishes. During the night, this shark becomes very active, searching for prey items along the bottom substrate. When a prey item is located, the shark will pursue it into a crevice and jam itself in after it. The tough skin, slender build, blunt snout, and protective eye ridges make it possible for the whitetip reef shark to hunt successfully within these very small spaces.
During mating, the male whitetip reef shark lies next to the female, using his mouth to hold on to her pectoral fins. This is followed by the male inserting one of his claspers into her genital opening, releasing sperm. Fertilization occurs internally, resulting in 1-5 embryos. These embryos are nourished via a placenta-like attachment to the mother during gestation. After an approximately 5 month gestation period, a litter of 1-5 pups is born with each pup measuring 20.5-23.6 inches (52-60 cm) in length. Mating and birth occur during varying seasons and is dependent upon location. At Enewetak Atoll, birth occurs during autumn and winter while in French Polynesia it occurs during the summer months.
Predators of the whitetip reef shark include large piscivorous fishes such as the tiger shark (Galeocerdo cuvier) and giant grouper (Epinephelus lanceolatus).
The copepod Paralebion elongatus is a parasite reported from whitetip reef sharks caught in Hawaiian waters.
Rüppell originally described this shark as Carcharias obesus in 1837. This name was changed to the currently valid scientific name of Triaenodon obesus (Rüppell, 1837) later that same year. A synonym referring to this species that has appeared in previous scientific literature is Triaenodon apicalis Whitely 1939.
Prepared by: Cathleen Bester