550 ECOLOGY AND BEHAVIOR 



generally cooler than those of the northern Indian Ocean, at depths of 200 

 meters or more the water temperatures are generally higher in the south- 

 western part than in the north, particularly from 500 m downward. The 

 oxygen content of the subsurface waters also changes significantly along the 

 length of the east African coast, the northern parts being deficient compared 

 to the southern regions (see Wyrtki 1971). 



Basic Biogeography of Southern African Seas 



Most of our knowledge of the distribution of animals and plants along the 

 southern African coasts is based on Stephenson's (1939, 1944, 1947) work 

 on the intertidal fauna and flora. Further significant contributions have been 

 made by J. L. B. Smith (1949), Day (1967, 1969), and Penrith (1969), 

 among others. An excellent summary of the present state of knowledge is 

 contained in Briggs (1974). The fauna of the southern Cape coast is clearly 

 a warm temperate one derived from the tropical region to the northeast 

 and is distinct in containing a high proportion of tropical species. Briggs 

 suggests the name Agulhas Province for this region and distinguishes it from 

 what he calls the Southwestern Africa Province, which ranges from approxi- 

 mately Cape Point to the tropical boundary in Angola. Water temperatures 

 are cooler in this region than along the southern Cape coasts but not enough 

 to be considered cold temperate. Until more data become available it is pro- 

 bably best to consider this area warm temperate but somewhat cooler and 

 distinct from that to the east of Cape Point. 



In this paper the following terms are used, sometimes quite arbitrarily, to 

 refer to different regions: 



Southwestern Cape— the western Cape coast to the west and north of the 

 Cape Peninsula 



Southern Cape— the southern Cape coast from the Cape Peninsula to 

 Knysna 



Eastern Cape— the eastern Cape coast from Knysna to Port St. Johns 



Southern Natal— Port St. Johns up to the Umkomaas River 



Central Natal— Umkomaas River to Umvoti River 



Northern Natal— Umvoti River to St. Lucia Estuary 



Tongaland— North of the St. Lucia Estuary to Inhaca Island 



Mozambique— Delagoa Bay and northwards 



East coast— Knysna to Beira. 



DISTRIBUTION OF SHARKS ON THE 

 SOUTHEAST AFRICAN COAST 



Until very recently, information on the distribution of sharks along the east 

 coast of southern Africa was at best fragmentary and at worst highly in- 

 accurate. In most cases inadequate knowledge of the taxonomy precluded 

 definition of the ranges of the various species. The present state of knowl- 

 edge is much improved but still far from complete. In particular, data on 

 sharks occurring on the continental slope and in deeper waters are lacking 



