394 



Illinois Natural History Survey Bulletin 



Vol. 23, Art. 1 



Measurements of 1938 brood bluegills 

 taken from Fork Lake during 1939 (Ben- 

 nett, Thompson k Parr 1940) indicate 

 that under uncrowded conditions this 

 species may grow rapidly to useful sizes. 

 Table 21 gives the numbers and average 



Table 21. — Numbers and average total 

 lengths in inches of 1938 brood bluegills col- 

 lected, March through November, 1939, from 

 Fork Lake near Mount Zion, Illinois. 



Month 



March 



April 



May 



June 



July 



August 



September 



October 



November 



Total 773 



total lengths of 1938 brood bluegills col- 

 lected from Fork Lake throughout thet 

 1939 growing season. 



Schloemer (1939) included in his study 

 of bluegill growth the uncorrected calcu- 

 lated lengths of bluegills taken in hoopnet t 

 collections from five Illinois lakes. Most t 

 of these collections were furnished, 1930- 

 1938, by Dr. Donald F. Hansen of thee 

 Natural History Survey. The collections 

 were from Grass and Pistakee lakes (gla- 

 cial), in northern Illinois, Senachwinc' 

 and Chautauqua lakes (bottomland lakes 

 adjacent to the Illinois River) in the cen- 

 tral part of the state, and Horse Shoe Lake i 

 (old Mississippi River oxbow) in thei 

 extreme southern end. The calculated 

 lengths of bluegills from each of these c 

 lakes were averaged to give the growth i 

 rate shown in table 22. 



The average growth of bluegills in i 

 Onized Lake (1941 census) and in Fork* 

 Lake is compared in fig. 7 with the average i 

 growth in the five Illinois lakes studied by i 



YEARS OF LIFE 



Fig. 6 — Average growth rate of bluegills in Onized Lake collections, 1938, 1940 and 1941. 



