Fish Population Adjustment 157 



commonly occurred as a natural cycle in many of the flood-plain lakes 

 along the Illinois River in Illinois. Professor Stephen A. Forbes ^~ de- 

 scribed tlie changes in water levels in the Havana region where in late 

 summer the lakes, which extended over thousands of acres in spring 

 when the river was high, covered only hundreds of acres; and many con- 

 necting channels were so low that it was often difficult to move a boat 

 from the river into these lakes. According to the average gauge readings 

 at Havana, water levels were usually highest in spring, gradually dimin- 

 ishing throughout the summer until they reached a low point in early 

 fall. Levels usually rose in fall and winter but floods seldom occurred 

 before spring. There were notable exceptions to this cycle, and floods 

 have occurred in summer, fall and winter. 



After World War I, most of the bottom land lakes of the Illinois River 

 valley were surrounded by earthen levees and pumped dry, and the lake 

 basins were used for farming. The few lakes that were left or reconverted 

 after agricultural use were more or less stabilized through the construc- 

 tion of levees and spillways that kept the river water out unless it rose 

 above the spillways' crests and held the lake water in when the river was 

 lower than the crests. 



During the pre-leveeing period of wide fluctuations of lake levels and 

 areas, the lakes in the Havana region were famous for their fishing, par- 

 ticularly for their largemouth bass fishing. Presidents of the United States 

 have fished there; fishing trains brought anglers from distances beyond the 

 range of the horse and wagon. Records show that it was not considered 

 unusual for fishermen to catch 100 bass in a day. 



There are still plenty of fish in the Illinois River and adjacent undrained 

 bottomland lakes,^^ but the populations are composed largely of crappies, 

 bluegills, yellow bass, sheepshead, buffalo, carp, bullheads, and channel 

 catfish, and where vegetation is abundant yellow perch may be common. 

 Although largemouth bass are sometimes caught by bass fishing experts, 

 the average angler does not go to the Illinois River for bass except in a 

 few special locations. 



Interest in the effects of fluctuating water levels upon fishes was stimu- 

 lated by the late Dr. R. W. Eschmeyer and his colleagues,^^' ^^' ^-' ^^ 

 through their investigations of TVA waters. In 1947, Dr. Eschmeyer stated 

 that several permanent-level pools on TVA impoundments had provided 

 poorer fishing than other reservoirs subjected to wide fluctuations of water 

 levels. He suggested that "the winter drawdown apparently limits the 

 abundance of rough fish (by limiting their food) without serious injury 

 to the game fish population." Drawdowns on TVA lakes followed no 

 definite schedule, but most of the drop in level occurred in winter follow- 

 ing needs for power. 



The sudden lowering of the water level of a lake with the accompanying 



