o 



O 



z 

 o 

 u 



X 



UJ 

 Q 



z 



MAR 



APR 



MAY 



JUN 



JUL 

 1939 



AUG 



SEP 



OCT 



NOV 



FIG. 2. — ^Average indices of condition of bass and bluegills taken at Fork Lake 

 throughout the collecting season of 1939. 



1 



The fluctuations in the indices of condition listed in table 5 are diagramed in fig.. 

 2. The bluegills were heaviest jvist before spawning, but lost weight rapidly during the 

 prolonged spawning period, from early June to late August. It may be of some significance 

 that the bass, which did not spawn, had about the same index of condition throughout the 

 year , .|1 



Dr. Donald F. Hansen (vinpublished manuscript) has followed the change of condition of 

 Lake Decatvir crappies for a number of years. Among sexually mature fish, he has found 

 condition highest during December and Janimry. In spring the condition decreases rapidly 

 and is lowest in June and July, when the fish spawn. 



Although Fork Lake bluegills showed a decline in condition dviring the spawning season, 

 this decline did not begin until June, and ther« is no indication from the November col- 

 lection that the greatest plumpness is in the winter. These differences in the time of 

 change in condition may be characteristic of the two species. 



FISH PARASITES 



I 



Dr. Lyle J. Thomas of the Department of Zoology, University of Illinois, found that 

 both bass and bluegills from Fork Lake contained large numbers of cysts of the tapeworm 

 Ophiotaenia sp. Other stages in the development of this parasite are found in copepods and 

 in the water snake, Natrix sipedon. 



The nematode, Spineteotus sp., was also found in these fish. It is probable that 

 other stages of this parasite are borne by some aquatic Insect (Mayfly or stonef ly) . 



We believe that these parasites have had little effect on the growth of the fish in 

 Fork Lake. 



6 





