conclusion is enhanced by the availability of 

 comparatively large samples from both regions 

 and by demonstration of greater average calcu- 

 lated lengths of age groups III, IV, and V of 

 fish from areas A and B than of average lengths 

 at capture of fish in cor responding age groups 

 from the Illinois-Missouri section. Growth of 

 the white crappie In the Fountain City backwaters 

 also exceeded that reported by Hansen (20) at 

 three stations in the Illinois -Iowa waters of the 

 Mississippi River. Of the two species, the 

 white crappie grew faster in both the Fountain 

 City area and the Illinois-Missourl-Iowa section 

 (Bamickol and Starrett, 3). 



The freshwater drum also exhibited faster 

 growth in areas A and B than it did in the Illinois - 

 Missouri section of the river. Reasonable 

 agreement between the growth data in the present 

 study and those of Butler and Smith (8) tends to 

 support this conclusion. Average calculated 

 lengths of advanced age groups of fish from the 

 Fountain City areas exceeded the average lengths 

 at capture of corresponding age groups in the 

 lower part of the river. 



On the basis of annual length increments 

 and on calculated lengths of the oldest age group 

 common to samples from both sections of the 

 river, growth of the bluegill and largemouth 

 bass appeared to be faster in the Fountain City 

 areas when it is compared to that in Illinois - 

 Missouri waters; however, because collections 

 of older-age fish of both species were limited, 

 this evidence is considered to be weak. 



Growth of the sauger appeared to be 

 slower in areas A and B than in the lower 

 section of the river. 



Appelget and Smith (1) reported a growth 

 rate of the channel catfish in Iowa -Wisconsin 

 waters which apparently was slower than that 

 in the Illinois -Missouri section (Upper Missis- 

 sippi River Conservation Committee, 62). 

 Bamickol and Starrett (3) reported the growth 

 of this species to be faster in the Illinois- 

 Missouri section than in Illinois -Iowa waters 

 of the river. 



The foregoing comparisons tend to confirm 

 the ratings given by Hatner (41) concerning watei 



quality in relation to fish production in the upper 

 Mississippi River. He found that in comparison 

 with waters producing good fish fauna, the 

 Mississippi River would be rated good in the 

 upper section and only fair in the lower section. 

 However, recent findings, which indicate faster 

 growth of the channel catfish and sauger in the 

 lower section than in the upper portion, demon- 

 strate that the fish species themselves must be 

 given primary consideration in any evaluation 

 of fish-growth potential of a water. 



General consideration of growth 



Without exception the growth rate of each 

 species examined in the present study exceeded-' 

 those previously cited as averages of two or more 

 waters in Minnesota, Wisconsin, southern Wis- 

 consin, Illinois, Michigan, northern Indiana, 

 and Ohio. The growth of certain species also 

 exceeded or approximated that reported for 

 individual waters in Illinois, Indiana, Iowa, and 

 Minnesota, with the following exceptions: 

 1) carp in Clear Lake, Iowa; 2) largemouth 

 bass in Onized Lake, Illinois; and 3) black 

 crappies in Onized Lake, Illinois, and Red 

 Haw Lake, Iowa. It is evident, considering 

 the geographic region and the latitude, that the 

 growth of the fish species studied from areas 

 A and B was comparatively fast . 



FACTORS INFLUENCING PRODUCTIVITY 

 AND PORJLATION DEVELOMENT 



Detailed investigation of conditions which 

 influence fish production was not attempted in 

 the present study. The rather limited data from 

 other areas, however, which compare environ- 

 mental factors with standing crops of fish justify 

 a short discussion of observed conditions and 

 related data from other sources. Among the 

 elements most likely to affect population levels 

 are water and soil fertility, food availability, 

 species composition, and water-level fluctuation. 



8/Average total lengths of the younger age 

 ~ groups were less than those shown from 

 other studies in certain cases but those 

 of the older age groups were consistently 

 greater in the present study. 



41 



