LIFE HISTORY OF LAKE HERRING OF LAKE HURON 



381 



66 per cent of the sample. In the 1924 sample, however, a sharp and complete 

 reversal in this relative abimdance of males occurs. In it 36.2 per cent were males 

 and 63.8 per cent females. This striking change is probably due to the fact that the 

 samples of 1924 were taken later in the season (November 21 to December 4) than 

 those of the years 1921 to 1923 (October 26 to November 12). It is possible that the 

 relative abundance varies, as in the salmon, during the course of the spawning sea- 

 son, the males preceding the females to the breeding grounds. In that case samples 

 taken late in the season would perhaps consist more largely of females. 



Table 48 



S. — Percentage of males and females present at various dates during the course of the spawning 

 , shown for each individual sample of Saginaw Bay herring taken in the years 1921 to 1934 



In this connection the data of Table 48 are of some interest. Table 48 shows 

 the relative abundance of males and females in each of tlie individual samples taken 

 in the years 1921 to 1924 on various dates between October 26 and December 4 

 during the course of the spawning season. It is realized that the percentages of the 

 different years may be only roughly comparable, as the spawning rim of different 

 years may not commence or end on the same dates nor continue at the same rate 

 throughout the season and that the percentages may also vary v/ith the localities 

 in the bay. In the Tobico samples (Table 48) the males show a progressive increase 

 in number early in the season but a progressive decrease late in the season. In the 

 Nayanquing and Gravelly Point samples, however, the males show an increase in 

 number as the late season advances. In this respect the data of the 1924 samples 

 conflict. However, the data of Table 48 do seem to show rather consistently that 

 the relative abundance of males and females varies during the course of the spawn- 

 ing run and that the males are more numerous than the females early in the season 

 but less numerous late in the season. (The Oscoda sample, page 388, Table 55, taken 

 early in the season, November 1, 1922, seems to contradict the latter conclusion. 

 In this sample the females were conspicuously preponderant. This was due in part, 

 however, to the large number of immature fish, 70.8 per cent of which were females.) 



The percentages of Table 47 show that the relative abundance of males and 

 females also varies with the age groups. The grand averages at the bottom of the 



