LIFE HISTORY OF LAKE HERRING OF LAKE HURON 



375 



The grand averages of Table 43 show that the herring grows very rapidly during 

 the first two years of Ufe. The first sharp break in the curve of total growth (figs. 

 39 and 40) occurs in the third year — the year during which sexual maturity is first 

 attained by many individuals. If tlie length at the end of the seventh year is taken 

 as 100 per cent, then at the end of the first year 46.4 per cent, at the end of the second 

 year 67.5 per cent, at the end of the third year 79.6 per cent, at the end of the fourth 

 year 85.8 per cent, at the end of the fifth year 89.1 per cent, and at the end of the 

 sixth year 94.2 per cent of the total growth in length is completed (fig. 40). Other- 

 wise stated, the increment in length of the second year equals 45.7 per cent, of the 

 third year 26 per cent, of tlie fourth year 13.3 per cent, of the fifth year 7.1 per cent, 

 of the sLxtli year 11 per cent, of the seventh year 12.6 per cent, and of the eighth 



Fig. 40.— Percentage of total growth in length and weight completed at the end of each year 

 of life. The percentages of length are shown on pages 375 to 376 and are derived from the 

 grand averages of Table 43. The percentages of weight are shown on page 376 and are derived 



from the grand averages of Table 34. , curve based on the average length reached 



at the end of the seventh year. , curve based on the average length reached 



at the end of the sixth year. . , curve based on the average weight attained at the 



end of the sixth year 



year 14.2 per cent that of the first year. After the third year the average yearly 

 increments remain fairly constant, varying from 14 (9) to 18 millimeters in 

 amounts (Table 43). 



^^hights. — Table 34 furnishes growth data of the herring in terms of weight. 

 The general average weight for each sex is given near the bottom of each column. 

 Curves based on these values are shown in Figure 41. If the total weiglit at the end 

 of the sixth year is taken as 100 per cent, then at the end of the second year 50.3 

 per cent, at the end of the third year 64.2 per cent, at the end of the fourth year 73.9 

 per cent, and at the end of the fifth year 83.9 per cent of the average total weight 

 is attained by the males, while in the females the corresponding values are 46.7, 63.4, 

 69, and 77 per cent. When the weights of the males and females are combined 

 99760—29 8 



