exceeds the number taken from any of the upstream pools (Figure 5) . The 

 number of carp taken by electrof ishing is generally equal to, or less 

 than the number taken in upstream pools (Figure 6) . As mentioned above 

 (see Table 10), carp has been a low-priced fish in recent times (10c per 

 pound wholesale, for undressed fish, in 1977 dollars), while channel 

 catfish have been relatively high-priced (48c per pound wholesale for 

 undressed fish, in 1977 dollars). 



Effects of the Navigation System on the Commercial Fishery . The 

 commercial fishery in the study reach of the Illinois River is not as 

 productive as it was at the turn of the century, but is in considerably 

 better condition than the fishery in the middle and upper reaches of 

 the Illinois River. Draining and leveeing of the flood plain in the 

 1920 's removed many backwaters and lakes which once produced the bulk of 

 both commercial and sport species of fish. The only lakes remaining 

 in the study reach are Meredosia Lake, and a few backwaters between 

 river mile 66 and 78, and a few other lakes and backwaters between 

 the mouth and river mile 15. Dam 26 at Alton increased the backwater 

 acreage in the lower portion of the Illinois River, thereby increasing 

 fish habitat, but we do not have quantitative data on the amount of 

 increase. 



The reduction in the quality and quantity of aquatic habitat due 

 to sedimentation in Lake Meredosia, a U.S. Fish and Wildlife Service Refuge, 

 has been discussed in the sedimentation section. It is possible that resus- 

 pension of bottom sediments by barge traffic in the main channel has contri- 

 buted to sedimentation in the remaining lakes and backwaters in the study 

 reach. In the reach of the river immediately above the study reach, commer- 

 cially important species of fish have been affected by a die-off of the 

 benthic organisms they feed upon. The die-off is apparently related to an 

 upstream source of toxicity (and not to the nine-foot channel project), 

 which is sufficiently diluted or otherwise removed from the river so 

 that fish food organisms can survive in the study reach. Boat traffic and 

 dredging and spoil operations may affect commercial species of fish and the 

 organisms upon which they feed. Some commercial fishermen report that they 

 do not fish in the main channel borders, because the currents and 

 wave wash associated with passage of barges collapses their nets. 



6A 



