LIFE HISTORY OF LAKE HERRING OF LAKE HURON 



321 



AVERAGE LENGTH OF BODY AND SCALE COMPARED FOR CORRESPONDING YEARS 



The body-scalo length relationship of the adult herring may be shown more 

 clearlj" perhaps by plotting the average total length of the body and scale for each 

 year of life on the same graph (fig. 13) or by plotting the average size of the scale 

 against the average length of the body, as showii in Figure 14. In both figures the 

 curves are based on non-X scales. The averages employed for Figure 13 are given 

 in Table 14, those employed for Figure 14 are given in Table 15. 



Fable 14. — Average length of an age group, together with average length of its non-X scales for all 

 Saginaw Bay herring collected in 1931, 1922, 1923, and 1924 



Table 15. — Average length, in millimeters, of non-X scales at various lengths of body for all Saginaw 

 Bay herring collected in 1921, 1922, 1923, and 1924 



The curve of Figure 13 based on scale measurements (broken line) rises more 

 rapidly than that based on the length measurements of the body (continuous line) 

 in every year except the seventh. This means that the scale increases its length 

 relatively faster than does the body during every year of hfe considered except the 

 seventh, when the percentage of increase of the scale is less than that of the body. 

 In Figure 14 the solid line represents the actual relation of the length of the body 

 and scale, as shown in Table 15; the broken line shows what the relation of the length 

 of the body and scale should be if that existing at a body length of 190 millimeters 

 remained constant. It may be seen that the two curves stay close together until a 

 body length of 263 millimeters is reached, when the actual body-scale curve suddenly 

 drops below the theoretical curve and maintains this position. This seems to indicate 

 that after the herring attains a length of approximately 260 millimeters the scale begins 

 to increase in length proportionally more slowly than does the body. This conclusion 

 appears to be corroborated by the curves of Figure 13, where it was shown that after 



