Lerczaket al. 1994:9). 



Following water quality measurements (e.g., dissolved oxygen) at each site, 

 fish populations were sampled by electrofishing from a 16-ft (5-m) aluminum boat 

 using a 3000-watt, three-phase AC generator. Sampling at each site typically lasted 

 one hour. Stunned fish were gathered with a dip net (1/4-in [0.64-cm] mesh) and 

 stored in an oxygenated livewell until sampling was completed Fish were then 

 identified to species, measured, inspected for externally visible abnormalities, and 

 returned to the water. More details on the electrofishing method and equipment are 

 given by Lerczak et al. (1994). 



DATA ANALYSIS 



For each sample, numbers of individual fish and total weights (pounds) were 

 tallied for each species. Fish catch rates v/ere calculated as the number of 

 individuals collected per hour of electrofishing (CPUE,J and as weight in pounds 

 collected per hour of electrofishing (CPUE^v). Catch data, both numbers of 

 individuals and pounds collected per sample and hour, were summarized and 

 reported by collection site. Data from sites also were grouped into reaches defined 

 by navigation dams (Figure 1) as follows: Alton Reach, river mile (RM) 0-80; La 

 Grange Reach, RM 80-158; Peoria Reach, RM 158-231, Starved Rock Reach, RM 

 231-247; Marseilles Reach, RM 247-271.5; and Dresden Reach, RM 271.5-286 on 

 the Des Plaines River. Data from reaches were combined further into three groups 

 (lower and middle Illinois River segments, and the upper Illinois Waterv/ay segment) 

 defined by their location along the river and by the amount of off-channel habitat 



