Index 



In figure 1 the rise and decline 

 of this fishing ground are shown by- 

 index figures. In the figure, the aver- 

 age monthly catch rates within segments 

 of 2 of latitude by 5 of longitude are 

 assembled for each longitude division, 

 the values are averaged for the period 

 of November to April, and these aver- 

 ages are further averaged to get a value 

 which is taken as 1.0 on the index scale. 

 As the figure shows, for each division 

 of the area the peak of the season is 

 either in January or thereabouts. If 

 we compare the rise and decline of the 

 fishing conditions in the whole area by 

 months, we find that the best fishing 

 season is between December and Feb- 

 ruary, with January having somewhat 

 higher values than the preceding or 

 following months. East of 165^E. the 

 peak of the season appears in December 

 and then is maintained with little change 

 until February. West of 165 E. the 

 pealc is either in January or February, 

 except for its appearance in December at 145 E. to 150 E. At 150 E. to 

 160 E. the peak fishing season is in February, whereas at 145 E. to 150 E, 

 the fishing is rather slack in January and February. This condition is 

 thought to arise from the shift of the intermediate zone. In any case, the 

 period when fishing is most active is around January. 



Month M 12 



Figure 1. --Indices of seasonal 

 changes in catch rates. 



15 >i 



U 10 - 



^^ 



U 10 

 s 



'^.j^ 



vv: 



32 - 33 N 



30-31 N 



29 - 30 N 



140 ISO leo ITO 180(E) 



Figure 2. --Catch rates by latitude. 



57 



In figure 2 it 

 appears that south of 

 30°N. , along the south- 

 ern edge of the area, 

 the geographical dis- 

 tribution of catch rates 

 of 3. to 5. is con- 

 tinuous and there is no 

 great variation from 

 area to area. Between 

 30°N. and 31°N. the 

 catch rates vary around 

 3. to 5. 0, but they show 

 a tendency to become 

 higher to the eastward 



