the sexes differ in the season of their migrationso Whether 

 such a phencraenon can be seen throughout the whole sea area in 

 which these fishes occur and migrate is not yet knownj, but it 

 is certain that it bears a close relationship to their spamiingo 



Then there is the deeply interesting fact that the fish 

 differ in size by sexeso V^J in general in the Tetrapturinae 

 the sexual difference in size is not conspicuous, but in the 

 Marlinae it is extremely so. This fact was noted along with 

 the sex ratio in the course of the investigations carried on 

 by the Shonan Maru in the East Philippines Sea in 1937c The 

 results of this study are shown in table 4„ 



Table 4 



Sex Ratio and Body Weights of Black Marlin 

 (Shonan Maru, Sast Philippines Sea, June - Seotember^, 192?) 



/ 

 30 



301T3 



iff 



/ 

 70 



Body 

 Weight 



/ 

 40 



/ 

 50 



50 



/ 

 60 



70180 



/ / 



80 90 



90 



/ 

 100 



100 



/ 



110 



Hot 120| 1301140(150! 160 p7/0 1 



/! / / / 



/ / 



120 | 150 140j 150 160 170 j 



Total 



% 



Male 

 Femal e 



17 

 2 



57 







39 







21 

 



1 

 2 



150 

 15 



91 

 9 



As the table shows s the males were all under 90 kgo and 

 the majority of them were between 40 and 60 kgo There were few 

 femaleSs tut the majority of them were over 90 kgo For a number 

 of years thereafter the sex ratios and size differences of the 

 fish landed at Takao and Suo were studied writh the following 

 general results\^>8 



ao For the black marlin the largest male was about 110 kgo 

 and there were none larger than thato Most of them were between 

 40 and 60 kgo Hardly any were taken under 20 kgo The females 

 ranged from 20 kgo to a maximum of 500 kgo j, but the greatest 

 number were between 100 and 120 kgo Consequently^ if a frequency 

 curve is drawn according to sizej, the mode for the males will 

 appear between 40 and 60 kgo and above and below this point the 



(7) As has already been described in the section on the tunas, 

 the sexes are known to differ in size among the tunas alsOj 

 but it is interesting that in the spearfishes this dif- 

 ference is exactly oppositeo 



(8) Nakamura^ Hiroshi, (1945) Studies on the Istiophoridae of 

 Formosan Waters, 7, Sexual Differences in Size of Fish, 

 Proco Formosan Nat, Hist„ Soco , Volo 35^ Aug, 



51 



