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Reef sharks
- Blacktip, Grey and Whitetip
The blacktip reef shark, grey reef shark
and whitetip reef shark are all sharks that are found on or
in the vicinity of coral reefs. They are all quite common and are
the sharks most likely to be encountered by divers and waders in the
shallow waters of the tropical Indo-Pacific.
Experiments carried out at Eniwetok, an atoll in the Pacific Ocean, show that the different reef sharks inhabit different niches and different depths. The blacktip is found on sand flats from the surface down to 15 meters, while the grey lives in the clearer but deeper water from 0 meter to 150 meters, occasionally to 1000 meters. The whitetip inhabits the crevices and caverns of the coral heads to about 30 meters.
Reef sharks swimming around divers (©
K. Jost / jostimages.com).
The blacktip reef shark, Carcharhinus melanopterus,
is probably the most encountered of the reef sharks. It occurs singly
or in small schools and is easily recognized by the bright blacktiped
fins, especially the first dorsal fin which has a contrasting white
band beneath the black top. The blacktip might be small in size compared
to other sharks, but should not be taken for timid or harmless. At
the presence of food, bait or when fishermen are clearing their catch
the shark will show its aggressiveness and not hesitate to attack.
The blacktip is widely distributed in the tropical and subtropical oceans, from the central Pacific westwards to the Indian Ocean, the Red Sea and the eastern Mediterranean. It feeds on small fishes, squid, octopus and shrimp, and are like the two other reef sharks viviparous. Mature blacktip reef sharks reaches the length of 1.7-1.8 meters (ca 6 feet).
The grey reef shark, Carcharhinus amblyrhynchos, is
of the same size as the blacktip, and is thought to live as long as
25 years. The grey reef shark should just like the blacktip, be approached
with precaution. When startled or approached too fast the shark will
display a series of threat postures that consists of exaggerated and
jerky movements. With arched back, raised snout and lowered pectoral
fins the shark shows the intruder that he better stand back.
The whitetip reef shark, Triaenodon obesus, is unlike
the two other sharks on this page of a more unaggressive nature. It
is a species that is most active at night, when it roams the reef
searching for fishes and octopuses, usually close to the bottom. During
the day the whitetip reef shark rests in coral caves, sometime in
small aggregations. Even though found in company with others whitetips
while resting, these sharks do not swim together at night.
Whitetip reef shark, Triaenodon obesus
(Photo Lasse).
Ref: Springer VG and Gold JP (1989),
Sharks in quetion: the Smithsonian answear book, Smithsonian
Institution Press, Washington, D.C. London
 Further reading
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