400 



Illinois Natural History Survey Bulletin 



Vol. 23, Art. 3 



Table 28. — Hypothetical age-length distribution of the 347 yellow bullheads collected from 

 Onized Lake in the census of June 24-28, 1941. Ages have been assigned on the basis of length. 

 The census was made about I'/z months after the spawning season, and the lengths shown for 

 each age include the growth increment for the early part of the 1941 season. 



Length in Inches 



Age in Years 



4 



i 



5 



X 



2 



6 



2 



7 Desirable Size- 



\ 



2 



8 



1 



2 



9 



2 



10 



1. 



2 



11 



1 



2 



12 



1 



2 



13 



i 



2 



14 



Total 



22 

 53 

 98 

 58 



53 

 27 

 22 



333 



1 



2 

 5 

 2 

 9 



1 



2 



they suggest three age groups. Young 

 bullheads are spawned during May in 

 Onized Lake, and it is unlikely that any 

 of the 4-inch fish taken in the census be- 

 longed to the brood of the 1941 season. 

 Therefore, it is assumed that the 4- to 7- 

 inch group represented the 1940 brood; 

 the ^Yz- to lOi/2-inch group the 1939 

 brood; and the 12- to 14-inch group the 

 1938 brood (possibly the 14-inch fish be- 

 longed to the 1937 brood, although this 

 seems unlikely, as bullheads are readily 

 caught). The assumption of these various 

 age groups has a validity it would not pos- 

 sess if the ranges of length in this species 

 had overlapped. 



Table 28 shows the age-length frequen- 

 cies of yellow bullheads, sorted according 

 to their hypothetical ages determined on 

 the basis of their lengths. 



Onized Lake is probably a poor habitat 

 for bullheads, because of the steep slope 

 of its basin and its limited shoal water. 

 These characteristics, coupled with the 

 complete absence of oxygen in the deeper 

 waters in summer, result in a limited habi- 



tat for bottom-living species such as the 

 black and yellow bullheads. 



Golden Shiner 



Notcmigonus crysoleucas auratus (Rafinesque) 



Golden shiners are not usually consid- 

 ered hook-and-line fish, but Onized Lake 

 fishermen caught and kept them in 1940 

 and 1941. Certainly, desirable sizes of 

 these fish cannot be less than 7 inches. 

 The creel census records show 40 golden 

 shiners, weighing a total of 7.7 pounds, 

 table 5. In the 1941 final census, 90 

 shiners were collected, of which 37 were 7 

 or more inches long, tables 7 and 8. The 

 age-length distribution is given in table 29. 

 This table shows that these golden shiners 

 in Onized Lake made rapid growth and 

 reached comparatively large sizes for min- 

 nows. Only fishermen and the larger bass 

 could utilize the larger shiners. 



Calculated lengths based on scale meas- 

 urements of 87 golden shiners are given 

 in table 30. These lengths are plotted as 

 a growth curve in fig. 10. 



