declined from 32.5 in 1934 to 3.12-7.06 in 1942, and to 2.02 in 1967 

 (Table 30). At Hardin (river miles 23.0-25.5) the catch declined 

 from 15.31 game fish per net-day in 1942 to 7.55 in 1964 and 1.51 

 in 1967 (Table 31). In the channels and side channels near the mouth, 

 the decline was from 11.16-15.31 in 1942 to 3.01 in 1967 (Table 32) . 



Sparks (1975) reported the results of an electrofishing survey of 

 the Illinois River, conducted annually from 1959 to 1974. Electro- 

 fishing methods had not been developed at the time the navigation dams 

 were being constructed. Hence, there are no pre- impoundment electro- 

 fishing data. Hoop-netting and electrofishing differ markedly in their 

 efficiency of capture of different species of fish and in efficiency of 

 capture of different sizes of the same species, so the hoop-netting 

 results should not be compared with the electrofishing results. However, 

 the electrofishing results can be used to assess changes in the game fish 

 in side channels (no electrofishing was done in lakes) of the lower 

 Illinois River between 1959 and the present. 



Sparks (1975: 38) reported that white bass in the Illinois River 

 showed a trend of increasing abundance in the downstream direction, with 

 the largest number occurring in Alton Pool. The largest numbers of other 

 game species, such as bluegill, largemouth bass, white crappie and 

 black crappie, occurred in the upstream pools, La Grange and Peoria, 

 which have the most connecting lake acreage. The catch of game 

 fish increased in 1973 and 1974 when water levels were high (Sparks, 1975: 

 36-37), but the increases were greatest in the pools upstream from the 

 Alton Pool. 



Increased flow of water in the Illinois has several beneficial 

 effects on fishes. Flooded areas often provide good spawning sites, with 

 firm bottoms, whereas the bottom in much of the river and its bottomland 

 lakes is covered with flocculent mud. Several people reported that sun- 

 fishes were spawning on flooded gravel roads and areas of firm mud or 

 sand in the spring of 1973. Flooded areas also provide good nursery 

 areas for juvenile fish, provided the water does not retreat too soon. 

 An increased current velocity in the river stimulates spawning migrations 

 of species such as white bass. An increased rate of water flow (discharge) 



