Illinois Natural History Survey Bulletin 



Vol. 23, Art. 3 



YEARS 



Fig. 3. — Average rate of growth of largemouth bass taken from Onized Lake, from Wiscon- 

 sin and from Louisiana. The Onized Lake bass averaged about the same size as the Wisconsin 

 bass in the first year and approached the size of the Louisiana bass during the second and third 

 years. 



their growth rate was slow. Once the 

 young bass became large enough to prey 

 on other fish, they began to grow rapidly. 



Black Grappie 



Pomoxis nigro-maculatus (Le Sueur) 



The black crappie population at the 

 time of the 1941 census had become re- 

 duced to 22 fish. Information gathered 

 from net fishing in 1938 and 1940, and 

 from the catch of black crappies made by 

 fishermen in 1939, 1940 and 1941, indi- 

 cates that the lake contained a large crap- 

 pie population at the beginning of the 1939 

 fishing season and a somewhat larger pop- 

 ulation in 1940 than was taken in the 1941 

 census. 



The lengths of the 22 crappies taken in 

 the 1941 census are recorded in table 13. 

 Only seven were large enough to interest 

 fishermen; the others were second sum- 

 mer fish of small size. Although a few 

 small fish undoubtedly belonging to the 



group (spawned in 1941) were seen when 

 the poison was applied, none were col- 

 lected, and it is probable that they were 

 eaten by fish, turtles and crayfish, or were 

 lost among the mats of vegetation. 



It is impossible to say whether the crap- 

 pies could have returned to their former 

 population level in Onized Lake in compe- 

 tition with the other species of fish pres- 

 ent. Certainly the number taken in the 

 final census was sufficient to replenish this 

 population with a single successful spawn, 

 if the young were able to survive predation 

 from a strong bass population. 



Studies of crappies in other lake census 

 work in Illinois (Bennett 1943) indicate 

 that the black crappie is rarely as numer- 

 ous as the white crappie, Po/noxis annula- 

 ris Rafinesque, in small artificial lakes. 

 Not only were there more stunted popula- 

 tions of white crappies than black in the 

 lakes censused, but in 14 lakes where both 

 species were present the white crappies. 

 were more abundant in all but 2. 



