102 



ILLINOIS BIOLOGICAL MONOGRAPHS 



[102 



The results of these examinations are summarized in table 25 which shows 

 age, length and weight measurements. This table gives the number of 

 fish of different ages examined during the last week of January and the 

 first week of February 1923 and 1924, together with their weight in grams 

 and their length in centimeters. In compiling the table the sexes were not 

 separated as the compilation was made nearly two months after the 



Table 25 



THE WEIGHT AND LENGTH OF CISCOS OF DIFFERENT AGES IN 

 OCONOMOWOC AND PINE LAKES 



spawning period and hence the error inevitable in the case of ripe females 

 is not introduced. Furthermore, growth curves for the sexes coincide so 

 exactly that no conclusions can be drawn other than that the sexes develop 

 at essentially the same rate. 



The comparison between the cisco of Oconomowoc lake and that from 

 Pine lake is exceedingly interesting, and the relationship is well brought 

 out in figure 21, where the growth in grams has been plotted against 

 the age in years of fish from the two lakes. Oconomowoc lake contains 

 the type of cisco most commonly found in the southern Wisconsin lakes, 

 while the Pine lake fish are on the average much smaller in size and weight 

 than those of any other lake in the county, yet entirely typical of the 

 species from a morphological and ecological point of view. Figure 22 shows 

 the length in centimeters plotted against the age in years for the two lakes. 

 From these figures it is seen that, while the fish do not differ greatly in 

 their relative lengths at the different ages, their weights do not agree at all 

 closely. An explanation of this condition is to be found in the physical 

 factors involved. The cisco is more abundant in Pine lake than in any other 

 lake in the county, probably many times more numerous. I have sat in a 

 fish house on the ice during the winter and watched the fish through a 



