Fish
Status (continued)
Navigation dams are also affecting fish populations in terms of dissolved oxygen and waste assimilative capacity:
The dams are significant reaeration sources for waters overflowing them...However, the dams should not be considered wholly beneficial. On the contrary, their existence lessens the capability of the waterway to assimilate organic waste by: 1. Increasing the time-of-travel and thus lengthening incubation periods in each pool, 2. Increasing the depth of flow and decreasing stream velocities thus lowering the reaeration capability of the pooled water, 3. Encouraging deposition and accumulation of solids on the pool bottom thereby creating benthic biochemical oxygen demands (Sparks 1975).
Management of the navigation system also causes erratic flows in the river. Releases from upstream areas lead to increased flows downstream, flooding moist-soil areas in the middle of the summer when the vegetation is most vulnerable to flooding. This loss of vegetation affects fish habitat as well as migrating waterfowl. The river is also not allowed to reach levels as low as it would under natural conditions, which prevents drying, and compaction of lake bottom sediments.
Table 33: 1973 Fishery Survey Results of the Illinois River and Backwater Areas (Stinauer 1974)
| Number of Fish | Station Occurrence | |||
| Species | Total | Percent | Total | Percent |
| American eel | 2 | 0.01 | 2 | 7 |
| Bigmouth buffalo | 96 | 0.80 | 19 | 68 |
| Black buffalo | 2 | 0.01 | 2 | 7 |
| Black bullhead | 18 | 0.20 | 12 | 43 |
| Black Crappie | 724 | 6.10 | 25 | 90 |
| Bluegill | 616 | 5.20 | 26 | 93 |
| Bowfin | 31 | 0.30 | 7 | 25 |
| Carp | 1,425 | 12.00 | 28 | 100 |
| Carp x goldfish | 231 | 1.90 | 9 | 32 |
| Carpsucker sp. | 1 | 0.01 | 1 | 4 |
| Channel catfish | 139 | 1.20 | 17 | 60 |
| Flathead catfish | 11 | 0.10 | 5 | 18 |
| Freshwater drum | 195 | 1.60 | 23 | 82 |
| Gizzard shad | 4,093 | 34.30 | 28 | 100 |
| Golden redhorse | 11 | 0.10 | 7 | 25 |
| Goldeye | 2 | 0.01 | 2 | 7 |
| Goldfish | 91 | 0.80 | 11 | 40 |
| Green sunfish | 453 | 3.80 | 17 | 25 |
| Largemouth bass | 1,846 | 15.50 | 28 | 100 |
| Longnose gar | 9 | 0.06 | 5 | 18 |
| Highfin carpsucker | 1 | 0.01 | 1 | 4 |
| Hybrid sunfish | 19 | 0.20 | 9 | 32 |
| Misc. minnows** | 323 | 2.70 | 22 | 79 |
| Mooneye | 8 | 0.06 | 4 | 14 |
| Northern hogsucker | 3 | 0.02 | 2 | 7 |
| Northern pike | 3 | 0.03 | 3 | 11 |
| Orangespotted sunfish | 48 | 0.40 | 8 | 29 |
| Paddlefish | 6 | 0.05 | 2 | 7 |
| Pumpkinseed sunfish | 1 | 0.01 | 1 | 4 |
| Quillback | 56 | 0.50 | 11 | 40 |
| Redear sunfish | 1 | 0.01 | 1 | 4 |
| River carpsucker | 105 | 0.90 | 16 | 57 |
| Rock bass | 15 | 0.10 | 1 | 4 |
| Sauger | 18 | 0.20 | 6 | 21 |
| Shortnose redhorse | 40 | 0.30 | 13 | 50 |
| Shortnose gar | 71 | 0.60 | 10 | 36 |
| Skipjack herring | 374 | 3.10 | 18 | 64 |
| Smallmouth bass | 126 | 1.05 | 10 | 36 |
| Smallmouth buffalo | 55 | 0.50 | 19 | 68 |
| Walleye | 5 | 0.04 | 4 | 14 |
| Warmouth | 12 | 0.10 | 7 | 25 |
| White bass | 183 | 1.50 | 18 | 64 |
| White crappie | 336 | 2.80 | 19 | 68 |
| White sucker | 35 | 0.30 | 8 | 29 |
| Yellow bass | 1 | 0.01 | 1 | 4 |
| Yellow bullhead | 76 | 0.60 | 5 | 18 |
