was partly because the fishes sought after are abundant in waters having this topography, but it 

 was also due to the impossibility of operating in the open sea without landmarks when the capa- 

 bilities of the fishing vessels and the navigational arts of the fishermen were so inadequate. 



The abundance of fish in the vicinity of oceanic islands and shoals is explained prin- 

 cipally from the point of view of the food supply as the sea waters are stirred up in the vicinity 

 of such places enriching the surface layers with nutrient salts from the rich, deep layers and 

 promoting the growth of plankton while gyrals concentrate the small animals which serve as 

 food for the tunas. There is still room for doubt as to whether or not this sort of explanation 

 exhausts the subject, but at any rate the tunas are observed to remain during certain periods of 

 time in the vicinity of such topographical features. This phenomenon is called " setsuki" ^j^j 

 such fishing grounds are called setsuki or shoal fishing grounds. On such fishing grounds fish 

 are Jilways comparatively abundant, offering superior conditions for fishing. 



Formerly there was a time when it was believed that such topography was probably 

 essential to the development of tuna fishing grounds and at that time explorations for new fishing 

 grounds meant a search for islands and shoals. In recent years with the progress of the ship- 

 building art and the improvement of navigational techniques, fishing grounds have been very 

 rapidly extended and the foregoing concept has been completely abandoned as it has come to be 

 realized that any place in the ocean can become a fishing ground if one succeeds in intercepting 

 the route of migration of the schools. The mid-Pacific albacore grounds are a good example. 



Under the heading "General Outline of Fishing Grounds and Fishing Seasons" a brief 

 account was given of the fishing grounds in Japainese waters. In the present section the Indian 

 Ocean and the Pacific Ocean will be divided into a number of areas each of which will be des- 

 cribed in terms of its characteristics and significance as a fishing ground. 



The data used here are all the results of the work of research vessels. The data 

 gathered by ordinary commercial fishing vessels have many shortcomings and there are grave 

 doubts concerning their reliability. For this reason, I have decided to use none of them. I 

 understand to some extent the feeling of the commercial fishermen in not wanting to inform others 

 of their good fishing grounds, but it goes without saying that this attitude is extremely disadvan- 

 tageous as an obstacle to the mutual interchange of knowledge and experience. The interchange 

 of accurate data is desirable both for the present mutual profit of persons engaged in the fishery 

 and for the healthy development of the industry. 



Some of the data gathered by research vessels have been lost. In others there are 

 imperfections Jind doubtful points, which in most cases have not been corrected despite the pas- 

 sage of tinne since they were gathered, and from these points of view I have found not a few occa- 

 sions for dissatisfaction. Furthermore, because the distribution of the data by area cind by sea- 

 son has been extremely uneven, it has been almost impossible to find out the changes in the 

 fishing seasons and the movements of the schools throughout the year for all the fishing grounds. 

 It is believed that the reason for this is to be found in the defects in the systemi which has opera- 

 ted hitherto. That is, each research vessel has, in addition to the duty of providing guidance for 

 the fishing vessels from its locality, had to bear the burden of a very heavy income budget. For 

 this reason, they have carried out their obligations to the income budget rather than try to attain 

 the basic purposes of a research vessel, and have all striven to fish on the same grounds at the 

 season when they could auiticipate sure catches. 



It is highly regrettable that this situation has not only not been completely corrected 

 at present, but in fact has rather been aggravated. This fact should give an important sugges- 

 tion concerning the proper management of fisheries research activities. The objectives of the 

 study of ocecinic resources cannot be attained by having each research vessel operate in accord- 

 ance with its own particular opinions and with the main objective of catching fish. However, the 

 execution of a research program based on a coordinated plan for the disposition of the vessels 

 and ignoring the question of income would require a great deal of money and would be completely 

 impossible to a weak economy. 



41 



