PART II: METHODS 

 Sampling Stations and Schedules 



Twenty-four sampling stations were selected in 1959 and a twenty- 

 fifth, Big Blue Island Chute, was fished once, in 1974. A listing and 

 description of the stations is given in Table 1. In considering loca- 

 tions for sampling, those that provide a desirable habitat for adult 

 fish and a good distribution along the river were chosen. There are 

 fewer stations in the upstream pools because those pools are shorter 

 than downstream ones. 



The stations are located most accurately by river mile. The river 

 mile designation indicates the approximate area fished: for example, 

 at the first station listed, that part of Mortland Island Chute ex- 

 tending from mile 18.7 to 19.4 was fished (Table 1). 



Most of the stations were in chutes (i.e. side channels of the 

 river), and contained habitats (brushpiles, undercut banks, and holes) 

 where a variety of fish were expected to congregate. The four stations 

 not in chutes were: (1) the station above Pekin, where both sides of 

 the main channel were fished; (2) the station along the shore of lower 

 Peoria Lake; (3) the station in middle Peoria Lake, where docks and rip- 

 rapping in various marinas were fished in the 1960's and where riprap- 

 ping at a State conservation landing in Detweiller Park was fished in 

 the 1970' s; and (4) a station in the Des Plaines River, where the wide 

 mouth of the DuPage River and a boat yard were fished. 



The Des Plaines River station was fished only in 1959, 1962, 1973, 

 and 1974. Since it is not part of the Illinois River proper, the sta- 

 tion was omitted whenever sampling time was limited. Results from the 

 Des Plaines station were excluded when computing averages for the whole 

 Illinois River. 



In order to sample under similar environmental conditions each 

 year, electrof ishing was conducted from late August to mid-October, but 

 only when the river was at pool stage behind the navigation dams. The 

 dams help to maintain a 9-ft-deep navigation channel by impounding water 



1 5 



