It would perhaps be hasty to oonolude that the spawning ground 

 of the migratory fishes such as skipjack and tuna, whose range of movement 

 is wide, is necessarily to be found wherever there are mature fish with 

 mature eggs, but we can surely think that the spawning grounds are not 

 far from the place these mature fish inhabit. If this is so, then we 

 can conclude that the spawning grounds are not necessarily limited to 

 the Sulu Sea or the Celebes Sea, but that they can also be found in 

 the seas around the South Sea Islands. 



Pvu-thermore, young (immature) tuna are sometimes caught on the 

 tuna longlines during tuna fishing ground surveys. From past ex- 

 perience (though the experiences are few) these young tuna are seldom 

 caught in deep water; they are generally caught near an island (land). 

 Since these young tuna, whose migratory power is comparatively weaker 

 than that of the mature truia, are caught near islands, we can assxjme 

 that the spawning ground of their species is found near islands. It 

 is recorded, also, that a few young yellowfin (immature yellowfin) 

 were caught by tuna longlines during the survey conducted by the 

 Zuiho Maru. 



In observing the above record, we cannot disregard the fact that 

 the young tuna were all caught in waters close to islands. It is 

 regrettable that the length measurements of the tuna were (anitted in 

 9 to 20. Hereafter, we will do our best to take accurate body measure- 

 ments of these immature fish eoid to collect material regarding this 

 phase* 



If this material is of any use as reference, it would be an 

 unexpected good fortune, I hope that you researchers will give me 

 your frank opinion regarding this manuscript. (June 10, 1941) 



13 



