Figure 3. The condition factor of carp, Cyprinus carpio , in the Illinois 



River in 1963 was much better downstream from river mile 80 — a 

 reach of the river where fish food organisms such as fingernail 

 clams, snails, and mayflies occurred. Channel catfish were also 

 more abundant in the lower Illinois River (Sparks, 1975b: Table 21). 

 The condition factor of carp was poor above mile 80, where the 

 fingernail clams had died out in the 1950' s. The condition factor 

 of carp in 1967 showed the same pattern, but an overall decline had 

 occurred, with more pronounced declines at river miles 95-105, 160- 

 170, and 200-240. By 1975, the overall condition of the carp in 

 the river had further declined, and localized declines had become 

 more severe. The general decline in carp condition between the 

 1960 's and 1970' s was associated with a decline in the abundance 

 of some food organisms, such as snails, fingernail clams, and 

 mayflies in the lower river. The causes for the localized 

 declines in carp condition are not known. 



Source: unpublished data in the files of the Illinois Natural 

 History Survey. 



o 

 i— 



u_ 



:s 

 O 



2.7-1 

 2.9- 



3.1- 

 3,3- 

 3.5- 

 3.7- 

 3.9 



1963 



15 



30 



/ 



A 



V 



60 



, s\ , f 



/1975 \ V / 



"I 1 1 1 1 1 I 



90 120 150 180 210 240 270 



MILES UPSTREAM FROM THE MISSISSIPPI RIVER 



60 



