Fisheries
(continued)
Forbes and Richardson pose the question in their 1919 report as to whether the increases in fish production are due to the increased organic material brought in with the opening of the canal or to the expansion of shallow water in which fish could breed. By 1919, it becomes clear that the latter is a limiting factor, as the bottomlands are drained and levees built.
Alvord and Burdick (1915) report that in 1899 the area of bottomlands under completed levees is around 9,100. Five years later this increases to 21,500 acres, and by 1908 the figure rises to 54,859 acres. In 1913, the acreage under levees is 130,830, and by 1914 this increases to 145,780.
The high water of 1904 floods 280,910 acres. When the 49,340 acres of bottomland lakes are added to this, we have a total of 330,350 acres aside from the river itself covered by water in time of flood. However, by 1914, with the levee construction, 44% of this area is no longer available as breeding grounds for fish, and another 16% is removed with completion of work on the existing drainage districts.
Fish harvests at Havana from 1908 to October 1913 reflect the changes due to the construction of levees and the activities in the drainage districts (Table 13).
Table 13: Total Fish Catch, Havana Market
| Year | Pounds | % of Total Catch on River | Authority |
| 1896 | 1,573,298 | 21.7 | Ill Fishermen's Association |
| 1897 | 1,600,183 | 16.5 | Ill Fishermen's Association |
| 1899 | 1,830,291 | 16.3 | Ill Fishermen's Association |
| 1900 | 1,368,010 | 11.4 | Ill Fishermen's Association |
| 1907 | 2,700,000 | 18.4 | Illinois Fish Commission |
| 1908 | 3,800,000 | 19.7 | Illinois Fish Commission |
| 1908 | 3,066,658 | - | R.E. Richardson |
| 1909 | 2,223,794 | - | R.E. Richardson |
| 1910 | 2,221,930 | - | R.E. Richardson |
| 1911 | 1,803,724 | - | R.E. Richardson |
| 1912 | 1,181,151 | - | R.E. Richardson |
| 1913 | 1,292,563 | - | R.E. Richardson |
Two factors are at play in the reduction in the fisheries in the river, both related to the reduction of plankton. All young fish in the Illinois River require plankton for food; plankton is produced almost exclusively in the backwaters. As Alvord and Burdick (1915) note:
“Although flowing streams often carry enormous quantity of it, this mainly perishes presently in our great silt laden rivers. When, as in very low water in midsummer, the contributions from the backwaters are reduced to a minimum, or perhaps wholly cut off, plankton of the streams also falls off to little or nothing. Left to itself, indeed, even so slow a river as the Illinois, would virtually empty itself of plankton in a little while. The fish producing capacity of the stream is thus proportionate, other things being equal, to the extent and fertility of the backwaters accessible from it and contributing to it at the hatching time of fishes.”
So the restriction of the floodplain and its lakes and swamps, in conjunction with increased sedimentation, leads to a reduced food supply and therefore reduces fisheries (Alvord and Burdick 1915). Forbes and Richardson also note that the larger, more voracious game fish, such as the walleye (Figure 26) and the pickerel, which by 1919 disappear above Peoria, were never likely to have been abundant in the Illinois River. They further note that the sheepshead or drum (Figure 27), the shovel-nose or spoonbill cat (also called paddlefish), and the buffalo-fish (Figure 28) are the most notable species whose numbers decline in recent years from Pekin to Meredosia.
Another factor associated with the decline in fisheries is construction of high dams in the 1930s, which creates navigational pools and changes the riverine environment to more lake-like habitat. A further factor is the “lack of practicable fish-ways in the dams at La Grange and Kampsville” (Alvord and Burdick 1915) except at high flows. As fish migrate upstream for breeding, any barrier to their movement diminishes their numbers.
