May, 1945 



Bennett: Overfishing^ Onized Lake 



399 



Table 27. — Average calculated total lengths in inches of two yellow bass collected from Onized 

 ^ake in 1938, one in 1940 and three in the final census of June 24-28, 1941. 



Brood 



Number 



OF 



Fish 



Average Calculated Lengths by 

 Years of Life 



Average Total 



Length at Time 



OF Collection 



i935... 

 ;936... 

 Total. . . 

 Average. 



[936... 



.936... 



1 

 1 



2 



10.95 



10.75 



11.15 



9.80 

 10.80 



11.40 



11.50 



3.90 and 0.83 pound, respectively. All 

 the scales collected from the smallest fish 

 ^vere regenerated ; ages determined for the 

 3ther three fish indicate that they belonged 

 to the 1936 brood, and it is probable that 

 the fourth fish in the collection was of the 

 same age. The total number of yellow 

 bass taken by fishermen in the creel census 

 of 1938-1941 was seven, table 5. Scales 

 from two yellow bass caught in hoopnets 

 in the 1938 fishing period and from one in 

 the hoopnet catch of 1940 are available for 

 study. One of the two fish caught in nets 

 in 1938 was spawned in 1935, and the 

 3ther belonged to a brood that was spawned 

 in 1936. The one yellow bass taken in a 

 net in 1940 also belonged to the 1936 

 brood. Calculated total lengths of yellow 

 bass from Onized Lake are shown in table 

 27. 



Table 27 indicates that the growth rate 

 of yellow bass in Onized Lake was uni- 

 form. Stocking records show that fish 

 were put in Onized Lake in 1934 and 

 1935, and a few yellow bass may have 

 been spawned in the lake in 1936. There 

 is no evidence of a successful spawn since 

 that date. In a study of the fish popula- 

 tions of 22 artificial lakes (Bennett 1943), 

 yellow bass were present in 7, including 

 Onized Lake, but young fish of this species 

 Iwere found in only 1, indicating that the 

 yellow bass is unable to maintain its num- 

 jbers in most small waters in Illinois. 



The growth of yellow bass in Onized 

 Lake was slow during the first season, very 

 rapid during the second and less rapid in 

 jsubsequent seasons; as increase in length 



represented a progressively greater increase 

 in weight of these fish. 



Bullheads 



Ameiurus mclas mclas (Rafinesque) 

 Ameiurus natalis natalis (Le Sueur) 



Only two black bullheads were taken in 

 the final census of the fish of Onized Lake ; 

 one of these was a small fish of 0.56 pound 

 and the other weighed 2.21 pounds. In 

 the hoopnet catches of 1938 and 1940, one 

 black bullhead was recorded for each sea- 

 son. Each of these fish weighed 2 pounds 

 (or perhaps the same fish may have been 

 caught in each year). 



In recording the hook-and-line catch, no 

 distinction was made between black and 

 yellow bullheads. A total of 89 bullheads 

 were caught, weighing 63.4 pounds, table 

 5. These represented 2.2 per cent of the 

 number and 5.5 per cent of the weight of 

 all fish caught. In view of the apparent 

 scarcity of black bullheads, it is probable 

 that nearly all of these fish were yellow 

 bullheads. 



In the final census of 1941, 347 yellow 

 bullheads were collected, table 7. Age 

 determinations on bullheads can be made 

 by studying sections of bones and spines, 

 but the process is so slow as to be imprac- 

 ticable in handling a large number of fish. 

 When the numbers of bullheads of various 

 lengths were tallied, all of the fish fell in- 

 to three general length groups: the small- 

 est from 4 to 7 inches, the next from 8i/^ 

 to lOi^ inches and the largest from 12 to 

 14 inches. As these groups were distinct, 



