ECOLOGY: INDIAN OCEAN SHARKS 569 



Table 5. Fifteen species of Carcharhinus recorded from the southwest 



Indian Ocean.* 



*In descending order of size as estimated from lengths at maturity given by Bass et al. 

 (1973) in Table 5C. 



seabed on the deeper parts of the continental shelf. Two other species, C. 

 obscurus and C. falciformis, are also normally found over the outer con- 

 tinental shelf but usually in open water rather than near the bottom. Both 

 of these are large sharks, with C. falciformis having a more strictly tropical 

 distribution. This shark rarely ranges into Natal waters and presumably has 

 its nursery grounds in deep water off the southern Mozambique coast. 

 Nursery grounds of this species have been identified only in the northwest 

 Atlantic, where the newborn young are found near the bottom along the 

 outer edge of the continental shelf (Springer 1967). C. obscurus, on the 

 other hand, uses shallow water off the Natal and southeastern Cape coasts as 

 nursery areas. Adult C. obscurus, chiefly pregnant females, are common off 

 Natal and range as far southwest as Cape Point. 



The 10 remaining species can be classified as inshore-dwelling sharks. 

 These are C. albimarginatus, C. amboinensis, C. brevipinna, C. leucas, C. 

 limbatus, C. melanopterus, C. plumbeus, C. sealei, C. sorrah, and C. 

 spallanzani. The ecological separation of these sharks is difficult to define in 

 some cases and appears to involve depth, feeding, and the use of different 

 nursery areas. They can be divided into three groups according to size: 



