120 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY- 



Estimation of age by scale examination. 



Scales were taken from each fish, cleaned and mounted 

 dry on a glass slide. 



The original intention was to count the winter rings only, 

 but later on it was decided to record the width of the respective 

 summer zones on the scales as percentages of the measured 

 part of the scale — i.e., the total distance between the " base 

 line " and the outer edge of the striated portion of the scale. 

 This distance was measured by a micrometer eye-piece in 

 conjunction with a low magnification. In actual practice it 

 was found that the personal error might amount to ± 1 %, 

 so that this error should be kept in mind when examining the 

 summaries. The results of these measurements show that in 

 separate year-groups the completed summer areas show a 

 considerable variation. For example, the two-ring scales of 

 the June sample show a variation in the first summer growth 

 from 38 % to 74 % of the measured part of the scale. By 

 examining the tables the other variations will be seen. 



Whenever a doubtful scale occurred it was stained in silver 

 nitrate, and examined under polarised light. This materially 

 assisted in the elimination of false rings. 



Explanation of the Tables. 



One typical scale belonging to each herring has been 

 measured, and these scales are grouped as " two-rings," 

 " three-rings," and so on. The "/ " columns show the numbers 

 of scales measured. 



Thus, for the group of 2-ringed scales (June) we have one 

 scale in which d v is between 36 and 40 % of the distance T 

 (fig. 1) ; 3 in which di is between 40 and 44 % of T ; 3 scales 



