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Contribution to the Biology of the Whitetip Reef Shark (Triaenodon obesus)

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Title:Contribution to the Biology of the Whitetip Reef Shark (Triaenodon obesus)
Authors:Randall, John E.
Date Issued:Apr 1977
Publisher:University of Hawaii Press
Citation:Randall JE. 1977. Contribution to the biology of the whitetip reef shark (Triaenodon obesus). Pac Sci 31(2): 143-164.
Abstract:The whitetip reef shark, Triaenodon obesus (Ruppell), is broadly
distributed in t4e tropical and subtropical Indian and Pacific oceans from the
Red Sea (type locality) and east coast of Africa to the eastern Pacific. Formerly
classified in the Triakidae, it is now regarded as a carcharhinid. It is distinctive
in its slender body (depth about 7 in precaudal length), obtuse snout, 43 to 50
teeth in each jaw in at least two functional rows, the teeth with one or two
small cusps on each side of the large central cusp, and white tips on at least
the first dorsal fin and upper lobe of the caudal fin. It is closely associated with
coral reefs and is often seen at rest in caves. There is evidence that this shark
has a home cave to which it may return after foraging for food. Although
reported to attain a total length of 7 feet (213 em) or more, the largest of 231
individuals measured by the author and associates was 168 em total length
(135 cm precaudal length). Seven recoveries were made of 124 whitetips tagged
at Johnston Island (time at liberty with tags 16 days to 2 years). Two of the
tagged sharks were caught in the same area as that in which they were released
and the others were taken .3 to 2.9 km from the tagging sites. The growth rate
of the tagged sharks, which ranged from 81 to 105 em precaudal length, varied
from 2.1 to 4.2 em/year. Two captive sharks, 73 and 88 em precaudal length,
grew at the rate of 4 and 2.3 cm, respectively, in the Gulf of Aqaba, Red Sea
over a period of 3 years. A whitetip born in captivity in July at a precaudal
length of 43.2 cm at Enewetak, Marshall Islands, grew 2 em in 6 weeks. The
stomachs of 56 whitetips were opened; 33 were empty; 17 contained the remains
of fishes (those identified were all reef fishes such as scarids and acanthurids);
four had eaten octopuses, and two contained both fishes and octopuses. One
reference described a diet of xanthid crabs and spiny lobsters. A juvenile
whitetip was found in the stomach of a larger grouper (Epinephelus lanceolatus);
some of the larger sharks such as the tiger and Galapagos sharks are probably
more important predators than this grouper. The sex ratio does not deviate
significantly from 1 : I except for whitetips caught in traps; 65 of 107 trap-caught
sharks were males. The smallest mature female T. obesus of this study measured
101.2 cm precaudal length (but a smaller size might be expected), and the
smallest mature male was 82 cm. Litter size ranges from one to five. Compared
to other carcharhinids, T. obesus is a relatively placid species which need not
be feared by divers unless provoked or attracted by spearfishing (even then
aggressive behavior toward man is rare). This shark may cause ciguatera
poisoning, especially if the liver is eaten.
Appears in Collections: Pacific Science Volume 31, Number 2, 1977

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