Whitetip reef shark  (Triaenodon obesus)

The whitetip reef shark earns its common name from the conspicuous white tips found on the first dorsal and upper caudal fins, occasionally found also on the second dorsal and lower caudal fins (4) (5). Small dark spots are scattered across the body, which is grey-brown in colour, fading to white on the underside (4). This small shark is moderately slender with a broad and flattened head, rounded snout, down-slanted mouth and large eyes (3) (4). The whitetip reef shark can be distinguished from the similar silvertip (Carcharhinus albimarginatus) and oceanic whitetip (Carcharhinus longimanus) sharks by being much smaller and more slender, by lacking the white tips these two sharks have on the pectoral fins, and by possessing a second dorsal fin that is significantly larger than in these two species (3) (5).

The whitetip reef shark is found widely throughout the Indian and Pacific Oceans. It occurs as far west as the coast of South Africa in the Indian Ocean and as far east as the coast of Costa Rica and Panama in the Pacific Ocean (3). Now found in Mexican waters as well (5).

As its name indicates, this shark is a reef shark that typically lives along the bottom of clear tropical waters near coral reefs, where it rests in aggregations in caves during the day and feeds at night (3) (4). It prefers shallow waters but has been reported at depths of 330 meters, although this has not been confirmed (4) (5).

Despite its docile nature during the day this nocturnal shark can become aggressive when hunting at night, thrashing through coral reefs looking for potential prey. The whitetip reef shark usually hunts alone, but is non-territorial and will occasionally work in cooperation with others in the pursuit of prey (3). Feeding primarily on bottom-dwelling octopus, lobsters, crabs and bony fish, it often chases its prey into a crevice before jamming its body in after it, sealing the exit (4). The extremely posterior location of the first dorsal fin compared to those of other sharks is an adaptation to this feeding habit, which allows them to get their heads and mouths much further into the gaps and holes in the coral (5).

The whitetip reef shark's mating season varies with location (4). Reproduction is viviparous and after a gestation period of around a year (5) the female will give birth to one to five live pups, which are completely independent at birth (3). Both sexes reach sexual maturity at approximately 5 years old, and it is estimated that this species can live to an age of 25 years (2).

The whitetip reef shark is fished in the waters off Pakistan, India, Sri Lanka and Madagascar (4). It is also believed to be fished in other waters across its range, but data is limited. The meat and liver are sold for human consumption, despite the liver being reported as toxic (6). Although this reef shark is widely distributed, its restricted habitat, depth range, small litter size, and moderately late age at maturity mean that its rebound potential is low and it may become increasingly threatened with rising fishing pressure (1).

The whitetip reef shark is widespread and relatively abundant and there is no legislation against fishing this animal (3). The whitetip reef shark project of Hawaii is currently researching this shark's life history, movement patterns and habitat utilisation in the hope that this will help in the future management of populations (7). The Food and Agriculture Organisation of the United Nations (FAO) have been working for years on an International Plan of Action for the conservation and management of sharks throughout the world (IPOA-SHARKS) (8). However, the vast size of the oceans where the whitetip reef shark resides and the difficulty of law enforcement in many areas make the task of managing the conservation of this beautiful shark extremely difficult (9).

For further information on the whitetip reef shark see:

• Shark Foundation:
  http://www.shark.ch/index.html
• IUCN/SSC Shark Specialist Group:
  http://www.flmnh.ufl.edu/fish/Organizations/SSG/SSG.htm

For further information on the conservation of sharks and rays see:

• Save Our Seas Foundation:
  http://www.saveourseas.com
• Project Aware:
  http://www.projectaware.org/

Authenticated (01/11/2005) by Nick Whitney, Graduate Researcher, University of Hawaii
http://whitetip.hawaii.edu