YELLOW PERCH IN SAGINAW BAY 



395 



Table 37. — Calculated weights at the end of the different years of life for female yellow perch collected during the spawning 



seasons of 1943-55 



[Increments in parentheses] 



Table 38. — Calculated weights (ounces) and weight incre- 

 ments of male and female yellow perch of Saginaiv Bay 

 in different years of life 



(Data from tables 36 and 37] 



1 2 3 4 5 6 7 



YEAR OF UFE 



Figure 16. — General growth in weight for Saginaw Bay 

 yellow perch of the 1943-55 spawning-run samples. 

 Male, broken line ; female, solid line. 



ments. The calculated weights of the females 

 were higher than those of the males in all years 

 of life except the first. At the end of their 

 second year the females were only a little heavier 

 than the males (a difference of 0.02 ounce) but 



in subsequent years the weights of the sexes were 

 widely separated. The growth advantage of fe- 

 males can be clearly shown from the ratios of 

 weights of females to those of males (table 38). 

 These ratios increased steadily from the second 

 to later years of life (slight decrease in seventh 

 year) . At the end of the sixth and seventh years 

 the weights of the females were nearly double 

 those of the males (ratios 1.95 and 1.91 for the 

 sixth and seventh years, respectively). 



The annual increments of weight for both 

 sexes increased almost continuously after the first 

 year of life (only exception, eighth year of life 

 of females). The females attained their greatest 

 advantage in annual increase over the males in 

 the sixth year when they had added more than 

 2,y 2 times the weight gained by the males (ratio 

 2.66). The sharp drop in growth increment in 

 the eighth year of life might be due to the inade- 

 quacy of the sample. 



