the sea areas within this range have some direct relation, leaving 

 aside the question of quantity, to the tuna fisheryo In Japanese 

 waters one or smother species is found throughout the year in the 

 area south of 35° north latitude„ Farther to the north excellent 

 fishing grounds are found from autumn to early .vintert. Thus the 

 fishing grounds of the tuna fisheries, compared to those of other 

 fisheries s have a remarkable evenness of distributiono 



Of course it is a great deal more advantageous that fishing 

 grounds be extensive and evenly distributed than that they be 

 restricted in extent and spotty in occurrenceo Howeverj the sole 

 fact that they are extensively and evenly distributed does not 

 necessarily mean that they are superior fishing groundSo The 

 density of distribution of the fishes which are sought, and the 

 difficulty or ease of operation are important factors. 



The factors which determine the density of distribution of 

 fishes are extraordinarily complex and not easily learned, but 

 they probably boil down finally to the productive potential of 

 the sea area. In other words ^ they may be thought to be directly 

 related to solar energy and the distribution of nutrient salts 

 within the area. 



It is a known fact that, for various reasonsj, the amounts of 

 nutrient salts present in coastal waters and in the seas of high 

 latitudes are great, while in the open sea of low latitudes they 

 are scanty. Consequently, it is said that the productive potential 

 per unit of sea water in the seas of the low latitudes is much less 

 than it is in the high latitudes and in coastal areas, and the fish 

 population is therefore smallero 



The facts set forth above provide extremely disadvantageous 

 conditions for the tuna fishery, which has as its fishing grounds 

 the open seas of the low latitudes. The most advantageous situation 

 from the point of view of cJonvenience in catching fish is to have 

 the greatest possible number of fish concentrated within the 

 smallest possible area. From this point of view the fishing 

 grounds of the bottom fisheries and the coastal fisheries offer 

 much better conditions thatl do the tuna grounds. 



If, however, we advance a step further in our thinkingj, we 

 see that because they do offer such excellent conditions, these 

 fishing grounds have been exploited early, the fisheries carried 

 on in them have been developed to a remarkably high degree, and they 

 have either already reached the peak of their development or are 

 close to ito Consequently the question of how best to regulate 

 the catch and the maintenance and propagation of the resource has 

 become an important and pressing problanj various positive and 

 negative measures for the maintenance of the resource -- such as 

 limits on the size of fish to be taken, limitations on fishing 

 seasons and grounds and the number of vessels engaged, and the 

 establishment of facilities for the propagation and protection of 

 the resource — have become extremely vital matters o 



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