YELLOW PERCH OF LAKE ERIE 



225 



YEAR OF LIFE 



Figure 4. — General growth curves showing average length and average annual increments in length 

 of Lake Erie yellow perch at end of each year of life. 



catches by trap nets, had an average weight of 

 just over 4 ounces. The only group with an 

 average weight of over 8 ounces (V) was repre- 

 sented by only four fish in the late fall samples 

 and, therefore, the reliability of the average is 

 open to question. Although there was consider- 

 able annual variation, the values in table 5 are 

 believed to represent rather well the average 

 weights of yellow perch taken by trap nets from 

 Lake Erie during the later season. 



The average weights of the age groups captured 

 late in the autumn differed considerably from the 



corresponding calculated weights (tables 5 and 8). 

 The empirical weights were greater for the younger 

 fish and smaller for the older individuals. Net 

 selectivity, whereby only the heavier of the shorter 

 fish were retained, no doubt accounted for the 

 greater empirical weights of the younger fish. 

 Perhaps the decrease in condition during October 

 and November (p. 255) was enough to bring about 

 the discrepancies noted among the older ages. 



In order to have strictly comparable data for 

 general growth in length and in weight, the equa- 

 tion for the length-weight relation of the Lake 



