ECOLOGY: INDIAN OCEAN SHARKS 



549 



In southern Natal (to the south of Durban) the continental shelf narrows 

 again and the inshore waters are even cooler, resulting in a marked increase 

 in the numbers of subtropical species. 



In the distribution of benthic animals along the east African coast, tem- 

 perature and oxygen content are probably the most important limiting 

 factors. Although the surface waters of the east coast of southern Africa are 



Tongaland 



Southern Natal 



Figure 2 The Natal coast, showing the major rivers entering the sea and 

 the arbitrary subdivisions of the area as outlined in the text. The 20- 

 fathom depth contour is shown as a dotted line, the 100-fathom contour 

 as a dashed line. 



