extremely broad and these fishes perform migrations on a large scale, not only can the essential 

 nature of the resource not be easily grasped, but the investigation of the paths of the migra- 

 tions and the factors controlling them are accompanied by remarkable difficulties and require 

 great expenditures: for which reason we can hardly be said to have any knowledge concerning 

 these phenomena. 



Up to the end of the war the writer spent over 10 years in Formosa, where he was 

 mainly occupied in the study of the ecology of these fishes. After the war he was ordered to 

 undertake the study of the resources of the tuna fishery at this research station, in which work 

 he is presently employed. In order to determine research policies corresponding to the new 

 conditions, the author has attempted to bring together data from tuna fishing experiments and 

 fishing ground surveys carried on by fishery research agencies throughout the whole country 

 during more than 10 years past. The object has been to see if it were possible by means of 

 these data to get some knowledge concerning the migrational patterns and the stock and thereby 

 to make son-ie contribution to the stabilization of the tuna fishery. What has been accomplished 

 in regard to these problenns is, however, very little. 



In the beginning the intention was only to write concerning the data referred to 

 above, but the decision was nnade to cover in outline fishing gear, fishing methods, and other 

 general matters concerning the tuna fishery. Consequently, the work is in part a repetition of 

 some of the material in the author's book. The Tuna and Their Fisheries, published by the 

 Tcikeuchi Book Store. 



The tuna fishery is at present in a somewhat congested condition, but unlike other 

 fisheries its fishing grounds are extraordinarily broad and are for the most part on the high seas 

 away from territorial waters. What sort of treatment Japan's tuna fishery will receive in the 

 future when the peace treaty is concluded, I do not know in the least. However, if the general 

 international concept of the high seas continues to be guaranteed in the future, the time will 

 surely come when this fishery will be permitted to operate freely. Until that day I hope to con- 

 tinue studying the essential character of the resource insofar as I am able, and attempting to 

 contribute to the establishment of a planned, stabilized tuna fishery without any diminution of 

 the resource. Corrections and contributions of data from the readers are requested. 



I have dared to undertake the writing of this report, despite my lack of talent, in 

 the hopes that my little knowledge and feeble effort might be of some use. A direct motive has 

 been the urging of the director of this station, Dr. Morisaburo Tauchi, fronn whom I have re- 

 ceived various assistance. I wish here to express my deep thanks to him. (January 2, 1948) 



P.S. 



During the writing of this manuscript a great revolution in fisheries research 

 agencies has taken place, the former Fisheries Experiment Station of the Ministry of 

 Agriculture and Forestry has been abolished, and the regional fisheries laboratories have been 

 established. The writer has been appointed director of the Nankai Regional Fisheries Research 

 Laboratory. Consequently, this report, which was to have been published by the Fisheries 

 Experiment Station of the Ministry of Agriculture and Forestry, has been changed to a report of 

 the Southern Regional Fisheries Research Laboratory. 



March 30, 1950) 



I. Types of Fisheries and Their General Description 



There are three nnajor types of fisheries for the tunas amd spearfishes. The first is 

 the net fishery, the second the hook and line fishery, and the third is the harpoon fishery. 



