the other years. All fish were taken by longline west 

 of Cape Point; Smith's (1964) record "off Cape 

 Agulhas" is an obvious error. 



Makaira nigricans 



Blue marlin, although known from very few 

 specimens, appear to enter the fishery off the Cape 

 at a different time of the year from the other three 

 species. Of the three specimens for which any data 

 are available, one was taken in April, one in June, 

 and one in July. It is extremely interesting to note 

 that the blue marlin did not appear during the sum- 

 mer fishery. This could suggest an Atlantic origin 

 (compare T. pfluegeri) rather than an Indo-Pacific 

 origin. It is also interesting that the blue marlin, the 

 only circumtropical istiophorid, was one of the scar- 

 cest in the area. This may suggest that there is only 

 limited genetic exchange between the two popula- 

 tions. Smith (1964) has suggested an Indo-Pacific 

 origin for the blue marlins taken off Cape Town on 

 the basis of one fish taken in the same area as a 

 striped marlin. The fish referred to is apparently the 

 fish taken on 23 June 1961 by one of us (M.J. P.); in 

 other words, in the same geographic area as striped 

 marlin (as stated by Smith), but at a different time of 

 year and probably from a different water mass. From 

 temperature and salinity records taken during the 

 tuna cruise on which this fish was landed, it is be- 

 lieved that the fish was taken in water of Atlantic 

 surface origin. 



Tetrapturus pfluegeri 



The longbill spearfish was the rarest of the is- 

 tiophorids found during the longline fishery. Only 

 two were seen, an adult and a juvenile, both in mid- 

 winter. 



BILLFISHES NOT RECORDED FROM 

 THE AREA 



Istiophorus 



No specimens of the sailfish have been obtained 

 during the Cape longline fishery. There are, how- 

 ever, certain old records. Most can be discarded 

 owing to the wider geographical area covered by the 

 term Cape of Good Hope in 19th century biological 

 reports. De Castelnau (1861). however, described 

 H istiophorus granulifer from St. Sebastian Bay, to 

 the east of Cape Agulhas. only just outside the area 



discussed in this paper. This species has generally 

 been considered to represent a sailfish (Jones and 

 Silas, 1964; Smith, 1964; Nakamura, Iwai, and Mat- 

 subara, 1968; Morrow and Harbo, 1969). Reexami- 

 nation of the type (a rather battered skull and mandi- 

 ble), however, has shown it to be the skull of a 

 Makaira rather than an Istiophorus. The skull is 

 broad and heavy with a short stout bill. The bill is 799 

 mm in length, with a circumference of 169 mm at a 

 point level with the anterior tip of the mandible. It is 

 possibly M. nigricans but insufficient comparative 

 material was available for us to be certain. 



Tetrapturus angustirostris 



Although not found at the Cape there is little 

 reason why this species should not occur in the area, 

 at least in some years. It is probably common in the 

 southern Indian Ocean (Japanese fishery records), 

 and has been recorded off Durban (Penrith, 1964). 



RECORDS OF BILLFISHES BASED ON 

 JAPANESE CATCHES IN THE AREA 



A detailed analysis of the Japanese commercial 

 longline catches of billfishes in the Atlantic has re- 

 cently been completed (Wise and Davis, 1973). The 

 data given here are based on a shorter period, but 

 include data from the southwest Indian Ocean in 

 addition to the southeast Atlantic. There are prob- 

 lems in using these data, since the catches of spear- 

 fish and sailfish are not differentiated and likewise 

 the small marlins, white and striped, are also not 

 distinguished. It is only in the region here discussed, 

 where both small marlins can occur, that their non- 

 separation will cause any difficulty. 



The catch in the waters off southern Africa has 

 been plotted for the common istiophorids by 5° 

 squares on a quarterly basis for the years 1965-69. 

 The results are shown graphically in Figures 2-4. In 

 these figures the catch rates per 100 hooks have been 

 shown for each square by the conventional markings 

 as used on dice and are as following: 



1 = <0.001 



2= 0.001-0.004 



3= 0.005-0.009 



4= 0.01-0.04 



5= 0.04-0.1 



6=>0.1 



The distribution pattern of black marlin based on 

 these catches is shown in Figure 2. Several features 



178 



