Table 3. --Dissimilarity of size component by locality. As the standard of the comparison, 

 the mean value of four localities in the North Pacific Current area was used 



we have the most data and we can see the 

 internal changes in the size composition more 

 clearly than in other current areas. The dis- 

 crepancies were shown in the following manner . 



5 (m„ - M„)2 



For each current we found 2 , 



n=l Mn 



and where this value was less than 50 we 

 marked it Q, when 50-100 O , and when over 

 100 X . Mji is the percentage of Group n in 

 the average size group composition for the 

 North Pacific Current, and m^ is the percent- 

 age of Group n for each of the localities. On 

 the basis of table 3 it can be said that (1) the 

 differences in the size composition as between 

 different currents is far more conspicuous 

 than the regional differences within the North 

 Pacific Current, and (2) the differences be- 

 tween currents are also more outstanding than 

 the seasonal differences in the size composi- 

 tion within the North Pacific Current. 

 Consequently, for the North Pacific Current, 

 at least, the differences from other currents 

 are much greater than the varlationa within 

 the current. 



Conclusions 



the Equatorial Countercurrent have differing 

 size compositions (fig. 1). 



(2) The differences in size composition 

 between the North Pacific Current and the other 

 two currents are much greater than the various 

 kinds of internal differences seen within the 

 North Pacific Current (table 3). 



(3) It is thought that there is a connection 

 between such differences in size composition 

 and the fact that the possibilities of spawning 

 and the sex ratios differ as between currents. 



The foregoing facts clearly confirm what 

 Nakamura (1954) has indicated about different 

 currents being different biological environments 

 (conclusion 2) and the differences in the eco- 

 logical significance of the schools which are 

 distributed in different currents (conclusion 3). 



In conclusion the author wishes to thank 

 those members of the staff of the Nankai 

 Regional Fisheries Research Laboratory who 

 collected the data, and also Director Naka- 

 mura and High Seas Resources Section Chief 

 Yabe for their assistance. 



(1) The albacore of the North Pacific 

 Current, the North Equatorial Current, and 



47 



