ECOLOGY: INDIAN OCEAN SHARKS 575 



confusion with the recently described /. paucus has resulted in uncertainty 

 about the distribution of this genus in tropical seas. In the southwest Indian 

 Ocean /. oxyrinchus certainly occurs regularly if not commonly on the 

 Natal coast. Young specimens have been taken on numerous occasions along 

 the eastern Cape and Natal coasts, which may be a nursery area for this 

 shark. 



In the genus Odontaspis, O. taurus has already been shown to be a shallow- 

 water tropical species migrating southward to nursery grounds in the eastern 

 and southern Cape. Two other species have also been recorded in the south- 

 west Indian Ocean. O. herbsti is a large (up to 360 cm) inhabitant of the 

 continental slopes, only occasionally coming into shallow water. A few juve- 

 niles have been trawled in Natal on the outer edges of the continental shelf, 

 and Forster et al. (1970) took what appears to be a large female of this 

 species in deep water to the northeast of Madagascar. The third species, 

 O. kamoharai (often placed in a separate genus Pseudocarcharias), attains a 

 length of about 100 cm and is usually found in warm open ocean waters. It 

 is abundant in the Mozambique channel, and one sickly specimen was found 

 swimming feebly in shallow water near Cape Town. 



The Nongaleoid Sharks 



The distribution of the nongaleoid sharks occurring off the east coast of 

 southern Africa is briefly mentioned to complete the picture of the overall 

 distribution of sharks in the region. 



Heterodontidae— The one species found in the region, Heterodontus 

 ramalheira, differs from most other heterodontids in that it is found on the 

 continental shelf rather than close inshore. It has been recorded from 

 Mozambique to the Arabian Peninsula. 



Chlamydoselachidae— The only extant species, Chlamydoselachus 

 anguineus, has been taken off the southwest African coast and possibly 

 occurs in deep water off the east coast, where there has been one doubtful 

 record (J. L. B. Smith 1951). 



Hexanchidae— Four species have been recorded from the east coast of 

 southern Africa (Bass et al. 1975d). Notorynchus cepedianus is a relatively 

 large (up to almost 3 m) shark found in shallow water in temperate areas. It 

 is fairly common on the Cape coast but rarely if ever ranges as far north as 

 Natal. The other three sharks inhabit the continental shelves. Heptranchias 

 perlo is a small species, growing to about 135 cm, with a tropical distribu- 

 tion. It is fairly common off southern Mozambique, and two specimens have 

 been caught off central Natal while none has been recorded from further 

 south. There are two species of Hexanchus, H. vitulus and H. griseus. H. 

 griseus is a large shark, growing to nearly 5 m, while H. vitulus is mature at 

 120 to 140 cm and grows to no more than about 180 cm. A tropical species, 

 it is a common shark from East Africa to southern Mozambique and two 

 specimens have been taken in central Natal. In temperate waters this shark 



