Home


Fish Populations in the Illinois River


by
Thomas V. Lerczak
Illinois Natural History Survey
Richard E. Sparks
Illinois Natural History Survey
Fig. 1. The Illinois River with locations of navigation locks and dams. Locations of the Illinois Natural History Survey's upper Illinois Waterway electrofishing stations are also shown.
The Illinois River is formed by the confluence of the Des Plaines and Kankakee rivers, about 80 km (50 mi) southwest of Chicago, Illinois. It then flows 439 km (273 mi) to join with the Mississippi River about 50 km (31 mi) northwest of St. Louis, Missouri (Fig. 1). The Illinois River has been extensively modified and degraded by industrial and municipal pollution for most of this century (Mills et al. 1966). The upper river reaches above the Starved Rock Dam (Fig. 1) became the most degraded because most of this pollution originated in the densely populated and heavily industrialized Chicago metropolitan area. In fact, by the late 1920's, the upper river was thought devoid of fish (Thompson 1928). Soon after this period, as pollution-control efforts began to have an effect, fish gradually returned.
Changes in the composition of a fish community in a polluted environment can be a useful index for assessing environmental health and the effectiveness of pollution control because different fish species vary in their ability to tolerate effects of pollution. In 1957 the Illinois Natural History Survey (INHS) initiated an annual electrofishing survey of the Illinois River to monitor fish populations. A central purpose of the survey was to relate changes in fish populations to environmental conditions. This article summarizes trends in fish populations of the upper Illinois River as determined from electrofishing catches from 1959 to 1993.

Status and Trends
Fish sampling was conducted at five stations in the upper Illinois River and at two stations in the Des Plaines River (Fig. 1) from late August through October. Data from these seven fixed stations were combined for analyses. At each station, fish were sampled by electrofishing for 1 hr; thus, catches are expressed as number of fish obtained per hour of sampling. Fish were stunned in an electric field, gathered with a net, measured, checked for externally visible abnormalities (sores, eroded fins, etc.), and returned to the water. The same methods and similar equipment have been used for all years of the survey to allow comparability of data among years.
Fishes of the family Centrarchidae (e.g., largemouth bass [Micropterus salmoides], bluegill [Lepomis macrochirus]) were treated as a group to simplify data analysis because they have very similar habitat requirements and are generally considered intolerant of polluted conditions. (The green sunfish [Lepomis cyanellus], however, is usually indicative of a stressed environment [Karr et al. 1986].) Also, because many of these fishes are piscivorous, their presence or absence will have a direct impact on overall fish community composition. Catches of common carp (Cyprinus carpio) and goldfish (Carassius auratus), both non-natives to North America, and their hydrids were analyzed separately. These two species are omnivorous habitat generalists that are tolerant of polluted waters.
Sediments of the upper Illinois River contain varying amounts of toxic substances (IEPA 1992), which are thought to contribute to the incidence of abnormalities on fishes that forage in sediments while minimally affecting fishes that forage in the water column. To test this hypothesis, all fishes were assigned to one of two groups: benthic species that frequently forage in bottom sediments (e.g., common carp) and pelagic species that usually inhabit the water column (e.g., bluegill).
Fig. 2. Number of individual fish obtained per hour of electrofishing from the upper Illinois Waterway for fish species identified as pollution indicators. Dashed lines connect data points for years between which electrofishing was not conducted.
Substantial changes have occurred in catch rates from the seven upper Illinois Waterway stations between 1962 and 1993 (Fig. 2). Catches of centrarchids have increased (D = 327, P < 0.001) since the early 1960's, peaking at 52/hr in 1983. Catches of centrarchids appear to have stabilized during the last 5 years (Fig. 2), indicating their populations may have reached carrying capacity. Catches have decreased for carp (P < 0.001), goldfish (P < 0.001), and carp x goldfish hybrids (P < 0.001) since the early 1960's. Carp were able to maintain their numbers until the mid-1980's (Fig. 2), as larger, older individuals probably died off and smaller, younger individuals were more vulnerable to predation by piscivores. Catches of goldfish declined rather precipitously from 1963 to 1966 for an unknown reason before substantial increases in centrarchids.
Fig. 3. Composition of catches (%) for the upper Illinois Waterway for 1963 and 1992, based on number of individuals collected per hour of electrofishing.
Data from 1963 and 1992 were chosen for more detailed examination, those years being representative of catches from early and recent years of the electrofishing survey. In 1963, goldfish accounted for almost one-third of all fish collected per hour, followed by carp, emerald shiner (Notropis atherinoides), and gizzard shad (Dorosoma cepedianum); together these four species dominated the catch, accounting for 95.8% of all individuals collected per hour (Fig. 3). In 1992, 13 species accounted for 95.4% of all fish collected per hour: emerald shiners were most abundant followed by centrarchids; carp and goldfish were reduced to a minor component (Fig. 3). The increase in centrarchids and decrease in carp and goldfish since the early 1960's (Fig. 2) reflect a more diverse fish community in recent years (Fig. 3).
For all years when data were collected from 1959 to 1993, the percentages of fish with external abnormalities were higher on benthic fishes than on pelagic fishes, suggesting that sediments may contain significant amounts of con-taminants. In fact, the IEPA (1992) identified several locations near our electrofishing stations on the upper Illinois and Des Plaines rivers as having sediments that contained elevated levels of toxicants, including mercury, lead, and PCBs. Brown et al. (1973) reported, however, that benthic fishes had a higher frequency of tumors than pelagic fishes (1.7% and 1.0%, respectively) even when collected from a relatively unpolluted Canadian watershed. Both groups of fishes, though, had higher rates of tumors in the polluted Fox River of northeastern Illinois (benthic fishes, 7.0%; pelagic fishes, 3.0%) than in the Canadian system (Brown et al. 1973). Hughes and Gammon (1987) noted that increasing pollution seems correlated with an increase in the incidence of abnormalities on fishes of the Willamette River in Oregon. Likewise, Tyler and Everett (1993) reported that bottom-dwelling barbel (Barbus barbus) collected from polluted rivers in England had a higher incidence of abnormalities than those collected from a clean river. Therefore, the relationship between a high incidence of abnormalities on fish and polluted waters has been well established. On the upper Illinois River, there was a marginal trend of decreasing incidence of abnormalities against years for pelagic fishes since the early 1960's (D = 3,156; P < 0.05), coincident with known improvements in water quality over the same period (Butts 1987), but not for benthic fishes (D = 1,937; P = 0.23).

Conclusions
Long-term trends of fish populations in the upper Illinois River reflect improved water quality in recent years as compared with the early 1960's. This trend is consistent with data presented in other studies that showed improved water quality in the upper Illinois River (Butts 1987; Lerczak et al. 1992). The increased incidence of external abnormalities between bottom-foraging fishes compared with pelagic fishes suggests contaminated sediments (Essig 1991; IEPA 1992).
Because recovery of fish populations in the upper Illinois Waterway appears to be a response to pollution-control efforts, definite restoration goals should be identified to help guide further recovery and to determine expectations. In addition, the specific causes for the high incidence of abnormalities in benthic fishes need to be explicitly identified.
For further information:
Thomas V. Lerczak
Illinois Natural History Survey
River Research Laboratory
PO Box 590
Havana, IL 62644
References
Brown, E.R., J.J. Hazdra, L. Keith, I. Greenspan, and J.B.G. Kwapinski. 1973. Frequency of fish tumors found in a polluted watershed as compared to nonpolluted Canadian waters. Cancer Res. 33:189-197.

Butts, T.A. 1987. Illinois River water quality. Past, present, future. Pages 195-209 in H. Korab, ed. Proceedings Governor's Conference on the Management of the Illinois River System: the 1990's and Beyond. Special Rep. 16. Water Resources Center, University of Illinois, Urbana.

Essig, H.W. 1991. Chemical and biological monitoring of the upper Illinois River. Pages 68-77 in H. Korab, ed. Proceedings 1991 Governor's Conference on the Management of the Illinois River System: the 1990's and Beyond. Special Rep. 19. Water Resources Center, University of Illinois, Urbana.

Hughes, R.M., and J.R. Gammon. 1987. Longitudinal changes in fish assemblages and water quality in the Willamette River, Oregon. Transactions of the American Fisheries Society 116:196-209.

IEPA. 1992. Illinois water quality report, 1990-1991. Illinois Environmental Protection Agency, Springfield. 405 pp.

 Karr, J.R., K.D. Fausch, P.L. Angermeier, P.R. Yant, and I.J. Schlosser. 1986. Assessing biological integrity in running waters: a method and its rationale. Illinois Natural History Survey Special Publ. 5. 28 pp.

Lerczak, T.V., R E. Sparks, and K.D. Blodgett. 1992. The long-term Illinois River fish population monitoring program. Annual report to the Illinois Department of Conservation (F-101-R-3). Aquatic Ecology Tech. Rep. 92/9. Illinois Natural History Survey, Champaign. 51 pp.

Mills, H.B., W.C. Starrett, and F.C. Bellrose. 1966. Man's effect on the fish and wildlife of the Illinois River. Illinois Natural History Survey Biological Notes 57. 23 pp.

Thompson, D.H. 1928. The "knothead" carp of the Illinois River. Illinois Natural History Survey Bull. 17(8):285-320.

Tyler, C.R., and S. Everett. 1993. Incidences of gross morphological disorders in barbel (Barbus barbus) in three rivers in England. Journal of Fish Biology 43:739-748.


Home