FOROTORD 



The position which the tuna fishery had come to hold among the 

 fisheries of Japan was a rather important one, but now after the defeat 

 that importance has increased markedly in comparison with the past. 



The tuna fisheries that are carried on in Japan are of several 

 kinds s but among them the most important^ whether from the point of 

 view of the scale of the enterprise or from that of the catch, is 

 probably the longline fisheryo In this book the author has recorded 

 all that has been learned hitherto^ mainly from the biological point 

 of view, about the tunas, which are the resource that supports this tuna 

 longline fishery^ Accordingly, ecological and general material has 

 been presented for the most part, and matters of fishing techniques and 

 the characteristics of various fishing grounds ha'ce hardly been touched 

 upono I have the intention of attempting to treat these in another 

 worko 



The title refers to the tunas, but in this book the spearfishes are 

 given equal weight. The reason for this is that the spearfishes are 

 sometimes referred to as "spearfish-tuna" and are treated in the same 

 way as the tunas. This, however, is not the only reasoni the chief 

 reasons are that the spearfishes are second in importance to the tunas 

 in the catch of the tuna longlines, and that in their habits they have 

 a great many points in common with the tunas,, In this sense one would 

 also have to discuss the sharksj, however, there is still a great deal 

 that remains to be understood about the sharks and so we must, unfortuna- 

 tely, omit such a discussiono 



The order of the work is to take up the biological aspects first 

 and to treat separately the morphology, ecology;, and systematics of the 

 tunas and the spearfishes,, and then to discuss the fisheries for both 

 together. However, as noted above, the fisheries are treated only in a 

 general way. 



Not a little of the material has been lost, and the data which I 

 obtained in Taiwan in recent years I was forced to leave behind when I 

 returned to Japan, so I regret very much that many parts of the book are 

 abstract in treatment, 



February 28, 1947 The Author 



