with the tuna fishery^ our knowledge concerning these fishes is 

 extremely poor and has not been brought to the point where it 

 can make any real contribution to the operation of the fisheryo 

 It is believed that m order that this fishery may have a 

 healthy development^ there is a great necessity for surveys 

 and studies which will consider all of these species togethero 



As has been previously stated^ the distribution of the 

 tuims is thought to differ markedly in different current systemsc 

 Hot only does the catch rate change sharply when a current 

 boundary is crossedp but in extreme cases the kinds of fish 

 making up the catch also differ completelyo The carrying on 

 of detailed oceanographical observations by an operating fishing 

 boatj considered as an actual problenij can hardly be thought 

 feasiblec. At present almost all of the boats are taking surface 

 w^ater temperatures,, however^, in the warm seas of the south it 

 is difficult to detect the differences between water systems 

 accurately by observations of this sorto 



Such evidences of "active waters'* as an abundance of birds 

 or flyingfish are serving some purpose as indicators of fishing 

 grounds s but they can hardly be said to sufficoo What is 

 wanted is some kind of indicator by means of which a simple 

 operation will make it possible to find easily the water systems 

 in which tuna are abundantly presento Such an indicator would 

 not necessarily have to be any of the fishes discussed in the 

 foregoingo A physical factor would dOj, or plankton might well 

 be used,, as it is in the North Sea herring fisheryo 



In the foregoing we have presented the outline of some of 

 the basic factors related to the tuna fisheryp but it is hard 

 to think that each of them bears an individual relationship to 

 the fisheryo Bather are they probably mutually interrelated in 

 a complex fashiono This sort of complexity is an essential 

 characteristic of fishings which has living organisms as its 

 direct object^, and it is the reason for the extraordinary 

 difficulty of fishery investigationso 



To sum upi, the tuna longline fishery must be said to be 

 one of the most primitive in character of all fisherieso We 

 do notp however^, mean to say that because of its primitive 

 nature^ the fishery itself has little prospect of future develop- 

 mento In view of the characteristics of the tuna resources;, we 

 should be led to quite the opposite conclusionc 



For Japan^, which through her defeat lost so many other 

 important fisheries resources ^ this may turn out to be an 

 essential resource^ However^, the fishery can never be satisfac= 

 tory in its present forrao It must be given a higher degree of 

 planability and stability through a more thorough study of the 

 essential nature of the resourceo 



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