Pacific oceanso And the amount of fish that is actually taken^''-"^ 

 can bs thought to be only a part of that brancho It is probably 

 impossible to grasp the absolute quantity of the resources and even 

 if it were possible to do so, the magnitude of -'•■ his quantity and 

 such things as the difficulty or ease of capturing the fish and 

 the possibility of loss in the operation of the fishery remain quite 

 separate problems o The discussion has strayed from the questioii of 

 the universality of distribution of the fishing grounds, but in any 

 case there is no basis upon which to gainsay the fact that the tuna 

 grounds have such universality to a much greater extent than do the 

 bottom-fishing grounds and the coastal fishing grounds. 



I will now present some opinions on the matter which may be 

 thought to have deep relationship to the foregoing, that is, the way 

 in which the tuna resource is propagated, or in other words, the 

 spawning of the tunas. 



As has already been set forth in the sections on spawning and 

 growth, it is thought that the spawning of these fishes takes place 

 throughout an extremely wide area and over a long period of timeo 

 This type of spawning habit is not limited to the tunas, but is 

 thought to be generally shared by all the pelagic fishes of warm 

 seas. To cite an example, in the case of the milkfish Chanos chanos 

 the larvae appear throughout the year in the waters of the Java area, 

 but the periods of greatest abundance are said to be May and November, 

 The larvae of the same species appear in Phillipine and Formosan 

 waters from April to October, with the period of greatest abundance 

 extending from June to Augusto It is not clear whether or not these 

 larvae are produced by the spawning of schools belonging to separate 

 independent stocks, but as far as the period of greatest spawning 

 activity is concernedj at any rate, the northern and southern hemi- 

 spheres present quite different situationso 



With regard to the tunas and spearfishes we do not yet have 

 as reliable data as in the case of the milkfish^, however, if we 

 assemble and consider certain data, it appears that the same sort 

 of phenomenon can be disoernedo A tendency can be detected for the 

 spawning season to differ somewhat and for different year-classes 

 to appear in different sea areaso However, as their interrelation- 

 ships are completely unknown, no conclusions can be drawn as to 

 whether they belong to the sajne or different stocks. Furthermore^ 

 with regard to the temporal differences „ it cannot be hastily 

 determined whether it is a case of different schools spawning at 

 different seasons, or whether it arises through the same school's 

 spawning while on the move. In any case, it is a fact that spawning 



\^^) Morisaburo Tauchi (l940) has given the following catch rates 

 for tuna migrating into Japanese waters g yellowfin, 29?2s 

 black tuna, 55% when young/meji/ and 10^ when mature/maguro/| 

 albacore 18%o 



76 



