May, 1945 



Bennett: Overfishing, Onized Lake 



403 



Table 32. — Age composition of the fish population of Onized Lake; census of June 24-28, 194L 



Age in Years 



Species 







Largemouth bass 33 



Black crappie 



Bluegill 236 



Warmouth bass 



Green sunfish 



rellow bass 



Black bullhead 



i'ellow bullhead 



Carp 



Common sucker 



Golden shiner 8 



Blunt-nosed minnow 



Total 277 



1 



Total 



195 



15 



3,369 



1,165 



187 



333 



1 



38 



I 



5,304 



24 



7 



2,857 



466 



49 



1 



12 



83 



7 



1 



2 



38 6 



3,454 115 



lis 



22 



6,545 



1,638 



245 



4 



2 



347 



1 



1 



90 



1 



9,171 



approximate length of time that was re- 

 quired for them to reach desirable sizes. 

 These sizes were attained by most species 

 during the latter part of the second grow- 

 ing season. Some fish escaped being caught 

 during the third season, but only a few 

 remained to begin the fourth or fifth. Of 

 these, the largemouth bass is the most nota- 

 ble and its survival is believed to hinge 

 upon the probability that, of all species 



represented, it is the most wary and best 

 able to learn from experience. Moreover, 

 the life span of the largemouth is normally 

 somewhat longer than that of other Illi- 

 nois lake fishes. 



Lines representing a pyramid of num- 

 bers of Onized Lake fish have been super- 

 imposed upon lines representing a similar 

 pyramid for a theoretical fish population 

 (Bennett 1943), fig. 11. This figure 



MOSTLY 



1941 BROOD 

 LOST IN THE 

 JUNE 24, 1941 



CENSUS 



OF 



\ 



Fig. IL — Diagram representing the age-frequency distribution of Onized lake fish, final 

 1941 census, superimposed upon a pyramid of numbers representing a theoretical fish popula- 

 tion. This diagram suggests that overfishing tends to remove most of the older and larger fish, 

 Dut has little effect upon the production of adequate broods of young. 



