2 

 the bottom sediments (up to 86.08 grams of oxygen/m /day, when the 



sediment was disturbed). Butts (unpublished report, 1975: 8) felt 

 that the sediment oxygen demand was high enough, so that without photo- 

 synthetic oxygen production during the warm summer months the dis- 

 solved oxygen levels in the lake would be severely depleted. Butts 



(1975: 4-5) found some organisms living on the bottom: phantom 



2 

 midges ( Chaoborus sp.) occurred at densities ranging from 129-344/m , 



and the fingernail clams (Sphaerium striatinum and Sphaerium simile ) 



2 

 occurred at densities ranging from 86-172/m . For comparison, Table 3 



shows that the average number of fingernail clams per square meter in 



the lower 80 miles of the Illinois River channel ranged from 10 in 



1915 to 52 in 1964. Paloumpis and Starrett (1960) reported densities 



of over 24,000 fingernail clams per square meter in Quiver Lake (mile 



123) on the Illinois River in 1952. Gale (1969: v) reported that the 



average number of the fingernail clam, Musculium transversum , at his 



2 

 sampling stations in Pool 19 was 40,000/m and the maximum number was 



over 100,000/m . 



In August, 1974, Sparks (1975: 53) found that dissolved oxygen 

 levels in Meredosia Lake were 3 mg/1, while oxygen levels in the 

 river on the same date were 6 mg/1. The readings were taken in the 

 middle of the afternoon on an overcast day, and waves produced by a 

 strong wind were resusp ending bottom sediments in the lake. In the 

 lake, a die-off of gizzard shad was occurring, and almost all the 

 fingernail clams maintained in plastic cages on the bottom of the lake 

 had died since they had last been checked in mid-July. On August 7-8, 

 Butts (unpublished report, 1975: 1) also observed dead fish around the 

 lake. Most of the fish were gizzard shad, but some carp and crappie 

 were seen. No submergent or emergent vascular aquatic vegetation has 

 been evident in the lake in recent years. 



Eoopnetting surveys of fish populations in the lower Illinois River 

 show that gamefish declined markedly in the main channel and side 

 channels between 1934 and 1942 (Table 30) and declined further between 

 1942 and 1967 (Tables 30, 31, and 32). In a side channel at Meredosia 

 Island (river mile 69.0), the number of game fish caught per net-day 



97 



