Speculation suggests that the bulk of the Agulhas 

 fauna is carried into the Return Agulhas Current; 

 thus the number of billfishes following a northwest- 

 ward extension would be relatively few, and then 

 with a maximum occurrence in late summer. Cor- 

 respondingly, the bulk of the southeast Atlantic bill- 

 fish would follow the South Atlantic gyre. A few 

 could find their way into the intrusion off South 

 Africa, but this would occur in winter when they are 

 rare in the area. 



Why this possible movement between the two 

 ocean systems has been so little utilized by billfishes 

 (and other large oceanic fishes such as the tunas) is 

 not known. That it has been little used is certain; 

 until very recently it was not known to occur at all in 

 istiophorids (with the exception of the blue marlin). 

 We can only suggest, in the light of present knowl- 

 edge, that some innate behavior pattern, possibly as 

 a result of hydrographic conditions in the earlier 

 history of the area, is responsible, since there is no 

 obvious physical barrier. The Cape of Good Hope is 

 not unique in acting as an inexplicable barrier; the 

 Straits of Gibraltar are apparently not a marked 

 zoogeographical barrier (Ekman, 1953), but as far as 

 present knowledge goes, appear to act as a similar 

 barrier to the Mediterranean spearfish, T. helotw. 



ACKNOWLEDG MENTS 



We owe a debt of gratitude to many persons for 

 their help: to C.R. Robins, R.S. Shomura, F.H. 

 Talbot, and J. P. Wise, we are grateful for their 

 prompt and patient answers to our queries; to S. 

 Bruins, B.J. Pretorius and C.S. de V. Nepgen for 

 help in obtaining literature and to T. Blamire, who 

 was responsible for the extraction and plotting of the 

 hydrographic data from the log sheets. 



Our grateful thanks are due to F. Williams, not 

 only for agreeing to read the paper at the interna- 

 tional Billfish Symposium on our behalf, but also for 

 his help in providing information relating to the large 

 pelagic fishes to one of us (M.J. P.) over many years, 

 with little in return. 



This paper is published with the permission of the 

 Secretary for National Education and the Director 

 of Sea Fisheries. 



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