I). West of 150 E . 



o 

 For convenience this ground is referred to as west of 150 E. , 



but it is not a nnatter of mechanical division along the line of that longi- 

 tude, for the area of low catch rates between 150 E. and 160 E. appears 



o o 



to run obliquely from the vicinity of 40 N. , 155 E. , to the vicinity of 



30 N. , 150°E. , so the area discussed is actually that west of a line 

 connecting these two points. However, there are considerable changes 

 from year to year in the way in which this area of low catch rates appears, 

 as is shown in table la, b, and c, so a rigorous delinriitation is difficult. 



In the overall view the catch rate is somewhat higher than it was 

 in November, and there aire a large number of unit areas with catch rates 

 above 5. 0. Unit areas with high catch rates are mostly distributed along 

 the southern and northern edges of this fishing ground, and the rates are 

 generally lower in the central portion. If we examine the catch rates in 

 detail, however, there are rather large variations between neighboring 

 unit sea areas, and there are also rather large variations in the amount 

 of fishing done within the different unit areas. Although this variation is 

 large, if the periods of time and the geographical extent of the areas are 

 not increased above a certain level, it is thought that the variations closely 

 resemble each other in character. In other words, between grounds where 

 the same groups of schools are fished at positions not too widely separated 

 there will probably be a close resemblajice in the fluctuations in the fishing 

 conditions, and hereafter this type of fluctuation will be referred to as vari- 

 ation within the fishing ground. 



Table 2 gives two or three examples of variations in the fishing 

 conditions in unit areas west of 150 E. 



Table 2, --Deviation of catch rates in certain unit areas 

 west of 150 E. in Decennber 



a. Area of 31°N. -33°N., 147°E. - 149°E. 



34 



