the tunasj, have characteristics that make it possible for tuna 

 to inhabit their waters^ and which, in fact., do afford a 

 habitat for tuna^ it is sometimes s een that v/hen one crosses 

 the boundary between the two currents p the distribution of the 

 tuna is remarkably differentc In other wordsp there are cases 

 where the boundary between two currents marks a conspicuous 

 difference in the value and significance of the waters as fishing 

 grounds., This phenomenon has already been treated to some extent 

 in the section on '*Di stribution and Migrations", but it will be 

 further gone into in this sectiono 



The following table shows a comparisons based on data from 

 surveys in the fomier «J^apanese mandated South Sea islands 

 (CP - 10° N„, 130° - 160° Eo), of the fishing conditions north 

 and south of the line of 5° N„ , leaving out all consideration 

 of longitude, year, or season. The data employed are all from 

 reports of research vessels j, no results of commercial fishing 

 operations being includedo 



Table 14 



Fishing Conditions by Areas 

 (former South Seas Mandate) 



The reason for dividing this area along the line of 5° N„ 

 is as follows 8 



In this area there are two conspicuous ocean currents o 

 One is the North Equatorial Current, which runs west, the other 

 is the Equatorial Count ercurrentj which runs easto The boundary 

 between these two currents varies in different years, in different 

 areas, and at different seasonso Furthermore, this boundary is 

 not a straight line, but lies generally within a range of 50-8ON0 

 For our purposes it would be desirable to draw a sharp delimita-" 

 tion by means of a current boundary, but as an actual problem 

 this is impossibloo Therefore, if the line of 5° No is used, 

 the region to the south of it will at least be completely within 

 the Equatorial Count ereurrento To the north a portion of the 

 Counter current will also be included, but the greater part of 

 the area will be w.dthin the influence of the North Equatorial 

 Current o 



97 



