oxygen, specific conductance, temperature, surface velocity) were taken at the 

 upstream end of each site. Sampling at each site typically lasted one hour, with all 

 obvious structure (e.g. downed trees, woody debris, rock rip-rap) intensively sampled 

 for fishes. 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 (total length and weight), inspected for externally 

 visible abnormalities (sores, fin erosion, etc.), and returned to the water. A detailed 

 description of the electrofishing method and equipment are provided by Lerczak et 

 al. (1994, Appendix A). 



A. Criteria for Sampling 



Fish collection by the Long-term Illinois River Fish Population Monitoring Program 

 occurs during the last week in August and September each year to increase the 

 probability of collecting young-of-year fishes with a 1/4 inch mesh dip net. Sampling 

 at each site is only conducted if river water levels are low and stable, as determined 

 by the U.S. Army Corps of Engineers, who maintain gage sites along the length of 

 the Illinois River waterway. Also, sampling for this project does not occur if water 

 temperatures have fallen unseasonably low (below 58 C), which are not typically 

 reached on the Illinois River until mid-October (Kofoid 1903, LTRMP unpublished 

 data 1999). 



