Figure 6.— Surface temperatures and salinities off South Africa, January 1961 (from Shannon, 1966). A. Temperature. B. 



Salinity. 



cal miles west of the Cape of Good Hope. Typical 

 Agulhas Bank mixed water is present as a small 

 patch of high salinity water (35.5"/oo). The upwelling 

 component of the Benguela Current system is pres- 

 ent to shoreward of a well-defined front. 



As westward penetration of the Agulhas Current 

 is pronounced. Indo-Pacific billfishes could be en- 

 countered as far west as long. 15°Eanduptolat. 32°S. 

 Close inshore, on the west and south Cape coast, the 

 abundance of pelagic fish in the 14-16°C upwelled- 

 origin water may be some inducement to feeding. No 

 South East Atlantic Surface water approaches the 

 coast. 



Autumn, April 1961 



(Fig. 7a,b) 



The Agulhas Current Extension is well marked, 

 extending as an intrusion of 22-24°C and 34.4''/oo water 

 to lat. 36°S, in a northerly direction. The Agulhas 

 Bank mixed water is continuous from east of the 

 Bank, round the Cape of Good Hope and into the 

 South East Atlantic. The South East Atlantic Surface 

 water is, for the most part, west of long. 17°E. The 

 frontal system between the ocean and the upwelling 

 area is not well defined, although the low tempera- 

 tures indicate that upwelling is occurring (13°C and 

 34.8*'/oo). The continuous low temperature and salin- 

 ity area (15°C and 34.9%o), extending around the 



Cape of Good Hope eastwards towards Cape 

 Agulhas, indicates that either upwelling has been 

 occurring or a southeasterly drift has occurred. 



At 20 m the isopleths tend to follow the coastline, 

 except that the influence of the Agulhas intrusion, 

 21°C and 34.45%o, and South East Atlantic Surface 

 water, 19°C and 35.6"/o(i, can be observed. At 100 m 

 the isopleths tend to follow the coastlme. 



The possibility of billfishes approaching the coast 

 at this time is not high. The extension of the Agulhas 

 Current exists 120 nautical miles south of the Cape 

 of Good Hope and the South East Atlantic Surface 

 water about 100 nautical miles west of the Cape. If 

 Indo-Pacific billfishes have moved into the Agulhas 

 mixed water, the continuous westward extending 

 area offers a route to the west passing close along the 

 south and west Cape coasts, although the tempera- 

 ture and salinity of this area may be uncomfortably 

 low, and therefore unsuitable for billfishes. As in 

 high summer, little opportunity is extended for the 

 movement of southeast Atlantic billfishes eastwards 

 around the Cape. 



Winter, July 1961 



(Fig. 8a,b) 



The survey area is dominated by the South East 

 Atlantic Surface water, which extends to the east of 

 Cape Agulhas. There is only slight evidence of the 



183 



