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BULLETIN OF THE BUREAU OF FISHERIES 



Table 10. — Body-scale ratio (K/V) for each age group of Bay City herring, based on diameter (F) of 

 special (X) and of unselected (non-X) scales. The body-scale ratios based on anterior radii {ac) 

 of X scales are given only for fish collected October 29, 1921 ' 



' The number of specimens employed is given in parentheses. 



' Ratios based on X and non-X scales combined. 



From this table it may be seen that the K/'V ratio based on X scales is highest 

 for fish in the third year in all collections but the one of November 12, 1923; that 

 the variability in the averages does not occur consistently in one direction; and that 

 the direction of the fluctuation in the averages is not the same in the different collec- 

 tions for corresponding years. The differences between the extreme averages of a 

 collection, based on a sufficient niunber of specimens, vaiy from 0.31 for the 1923 fish 

 to 1.56 for the 1921 fish. The average of the three differences is 0.93. The Z/F 

 ratios based on non-X scales show similar characteristics. The ratio is not always 

 higher for fish in the third than for those in later years, the fluctuations in the ratios 

 do not occur in one direction, nor is this direction the same in all collections. The 

 differences betv/een the extreme averages based on non-X scales vary from 0.84 in the 

 1922 fish to 1.38 in the 1921 fish of October 29. The average of the three difl'erences 

 is 1.09. The direction of variation in the ratios based on non-X scales does not 

 always follow that of the ratios based on X scales. The ratios based on X scales 

 vary less with the age groups than those based on non-X scales. 



Wlien we arrange the ratios on the basis of year classes instead of age groups 

 only, as shown in Table 11, we again find that the Z^/F ratio is not consistently high 

 or low in the fish of the same age group, and that the fluctuations in KjV are fortui- 

 tous, occurring in all directions. The differences between the extreme averages 

 based on X scales of a year class vary from 0.63 for the 1919 to 2.53 for the 1918 

 year class. The average of the three difl'erences is 1.54. The range for these differ- 

 ences for the non-X scales extends from 0.23 in the 1920 to 1.07 in the 1919 year class. 

 The average of the four differences is 0.76. In this table the ratios based on non-X 

 scales vary less with the age groups than those based on X scales. 



