Fish (continued)

In 1957, the Illinois Natural History Survey begins an annual electrofishing survey of the Illinois River in order to monitor fish populations. The purpose of the study is to examine the effects of changing environmental conditions on fish populations.

Richard Sparks and William Starrett use electrofishing to document the fish species that exist in the Illinois River in a 1959-1974 study. Locations are identified by navigational pools: Alton, LaGrange, Peoria (three downstream pools), and Starved Rock, Marseilles, and Dresden (upstream pools). Attention is focused on the three downstream pools (see Figure 38).

Figure 38: Map Showing the Location of Three Downstream Navigational Pools: Alton, La Grange, and Peoria

The following (Table 22) is a list of fish species identified and their status, including whether they are a game or commercial species.

Table 22: Fish Species and Their Status (Sparks and Starrett 1975)

Fish species taken only in small numbers during the electrofishing include:

• Yellow Bullhead (Ictalurus natalis) taken only from the three downstream pools.
• Shorthead Redhorse (Moxostoma macrolepidotum) found throughout the river.
• Spotted Gar (Lepisosteus oculatus) female taken at Havana in 1973.
• Mooneye (Hiodon tergisus) found only in the Alton Pool until 1974 when it was collected in the Peoria Pool.
• Goldeye (Hiodon alosoides) is related to the Mooneye; found farther upstream.
• American Eel (Anguilla rostrata) is very uncommon; one specimen taken in the Alton Pool.
• White Catfish (Ictalurus catus) was introduced and has been taken at Havana.
• Skipjack Herring (Alosa chrysochloris) taken sporadically throughout the river.
• Longear Sunfish (Lepomis megalotis) was thought to be extirpated in the state but was taken at the La Grange Pool in 1973.
• Northern Pike (Esox lucius) were common prior to 1906 but are now rare. Sport fishermen report taking them in 1973 near the Marseilles Dam.

Catfish may be more abundant than indicated from this electrofishing for several reasons. First, bottom-dwelling species do not always surface to be netted after shocking. Second, turbid waters make it more difficult to see fish to net. Fish must be within 10-15 cm of the surface to be netted. It is estimated that only 10% of the total catfish population was represented by the electrofishing samples, compared to 52% of the sunfishes.

Table 23 lists the number of fish taken in 30 minutes by electrofishing in the three downstate pools from 1959 to 1974, at two-year intervals. The carp (Cyprinus carpio) is the only species found in abundance, with the yellow bullhead (Ictalurus natalis) and black bullhead (Ictalurus melas) being uncommon.

Table 23: Average Number of Five Species Captured Electrofishing per 30 Minutes of Fishing, 1959-1974 (Sparks 1975)