Table 1. --Modal length of each length group 



Table 2. --Direct difference between successive length groups 



Table 3. --Lagged difference between successive length groups 



2. No conspicuous difference can be seen 

 between the 5-year average values for the two 

 differences and the standard deviation. 



3. The intervals for each group for both 

 the direct difference and the lagged difference 

 are 10.5 cm. to 11.5 cm., and the several 

 size groups are spaced at intervals of a little 

 more than 10 cm. The intervals are approxi- 

 mately the same for each size group regard- 

 less of whether it consists of large or small 

 fish. 



The ranges of body length in each group 

 are as shown in table 4a, b, and c. The 



breadth of distribution of all groups is rather 

 large, and the two extremes overlap with the 

 adjoining groups. For groups III to V the 

 breadth of the distribution is far greater than 

 the interval between modal lengths, being more 

 than 20 cm. in most cases. However, there is 

 hardly any overlapping between the length 

 ranges which include 80 percent of each group. 

 The average values from 1948 to 1952 of the 

 boundaries of the ranges within which the vari- 

 ous length groups are dominant are as follows: 

 groups I-II, 59. 8 cm. ; groups II-III, 70. 7 cm. ; 

 groups m-IV, 83.3 cm.; groups IV-V, 96.3 

 cm. ; groups V-VI, 107. 7 cm. 



