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Full text of "Recent trends in the Illinois River indicated by fish populations"

Recent Trend's In the Illinois River Indicated 
by Fish Populations 



Prepared by 

nichard E. Sparks 

and 
Thomas V. Lerczak 



114 



February 28, 1993 



DISCLAIMER 

The findings, conclusions, and views expressed herein 
are those of the researchers and should not be considered as 
the official position of the United States Fish and Wildlife 
Service, the Illinois Department of Energy and Natural 
Resources, or the Illinois Department of Conservation. 

ACKNOWLEDGMENT OF SUPPORT 

The results presented in this report were derived from 
research supported by: the Illinois Department of 
Conservation and United States Fish and Wildlife Service 
under the Federal Aid in Sport Fish Restoration Act 
(Dingell-Johnson/Wallop-Breaux) , projects F-101-R and F-94- 
R; the Illinois Department of Energy and Natural Resources, 
project 89/215;, the Illinois Environmental Protection Trust 
Fund; and the Critical Trends Assessment Project CTA1. 



11 



Recent Trends in the Illinois River Indicated by Fish Populations 

Prepared by 

Richard E. Sparks 

and 
Thomas V. Lerczak 

February 28, 1993 



BACKGROUND 

The Illinois River belongs to a world class of large 
river-floodplain ecosystems, where biological productivity 
(including fish yield) is enhanced by annual floodpulses that 
advance and retreat over the floodplain and temporarily expand 
backwaters and floodplain lakes (Junk et al . 1989; Sparks et al . 
1990; Sparks 1992). The expanded aquatic habitats are utilized 
as feeding areas by migratory birds and as breeding areas and 
nurseries by fish and other aquatic life. The Illinois River 
today is the largest river (in terms of water flow) contained 
mostly within the state, and its fish populations reflect urban 
influences from the state's largest metropolitan area (the 
Chicago-Joliet area) as well as effects of land use practices in 
the corn belt that runs across the middle of the state. 

The river is divided into 5 reaches by navigation dams, including 
the Alton Dam (Dam 26) on the Upper Mississippi River which 
influences the lower 80 miles of the Illinois River (Fig. 1) . 
These five reaches in turn fall into three major sections, 
defined by the natural physiography of the river and by the 
degree and nature of human alterations. The Dresden, Marseilles, 
and Starved Rock reaches together form the upper Illinois River, 
characterized by a geologically young channel with a relatively 
narrow floodplain between rocky bluffs. This section has been 
heavily influenced historically by effluents from the Chicago- 
Joliet area. The La Grange and Peoria reaches comprise the 
middle river. Here the river occupies a broad floodplain (2 to 5 
miles wide) created by the ancestral Mississippi and Ohio rivers. 
Approximately half of the floodplain and the natural backwaters 
and lakes remain along this section. In contrast, most of the 
floodplain and backwaters have been drained in the lower river 
(the Alton reach) , and the river channel runs between two levees 
until it nears the confluence with the Upper Mississippi River. 






Digitized by the Internet Archive 

in 2010 with funding from 

CARLI: Consortium of Academic and Research Libraries in Illinois 



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Illinois River fish populations February 28, 1993 

STRESSES 

Major historical stresses on the ecosystem include: (1) drainage 
of wetlands and channelization of tributaries in the drainage 
basin, mostly in the late 1800s, but continuing to the present; 
(2) the diversion of Chicago sewage and industrial effluent from 
Lake Michigan to the Illinois River, via a system of waterways, 
starting in a major way in 1900; (3) leveeing and draining of 
half the floodplain in the 1920s, primarily for agriculture; (4) 
completion of the federal 9-foot navigation project in the 1930s; 
(5) intensification of agriculture in the 1950s, resulting from 
the shift from small grains, orchards and pastures to row crops, 
and introduction of practices such as fall plowing and use of 
pesticides and chemical fertilizers; and (6) development of an 
industrial corridor (chemical manufacturing, petroleum refining, 
and storage of agricultural chemicals) in the 1950s along the 
upper river and its Des Plaines tributary in the vicinity of 
Joliet. Upland drainage and channelization of tributaries 
probably increased the rate of delivery of water, sediment, and 
pollutants to the main river. Diversion of sewage and Lake 
Michigan water raised mean water levels, caused the less flood 
tolerant trees to die back on the floodplain, and eventually 
degraded water and sediment quality (Mills et al. 1966) . 
Drainage projects on the floodplain reduced fish and wildlife 
habitat and the capacity of the floodplain to convey or store 
flood water and concentrated sedimentation in the areas that 
remained open to the river. The navigation dams permanently 
inundated portions of the floodplain, so the soils do not dry and 
compact as they once did during low river stages in midsummer 
(Bayley 1991) . Also, the wind fetch was greater on the expanded 
lakes and backwaters, so the heights of wind-driven waves 
increased and thereby increased resuspension of the 
unconsolidated sediments. The improved navigation system 
stimulated boat traffic, that also generated waves which 
resuspended sediments and contributed to bank erosion. 
Intensification of agriculture, coupled with stream 
channelization and removal of riparian vegetation, increased the 
rate at which water and sediments, and chemicals associated with 
them, were delivered to the river. The expansion of chemical 
handling and manufacturing on the upper river increased the risk 
of both chronic pollution and spills. 

RESPONSE OP FISH POPULATIONS TO RECENT STRESSES 

The Long Term Electrof ishincr Survey. The fish populations of the 
Illinois River have been surveyed annually since 1957, except for 
a few years when no funding was available or sampling could not 
be conducted because the river was in flood. The sampling is 
conducted at 28 permanent locations in the fall, using an 
electrof ishing boat, when water levels are maintained at stable, 
low elevations by the navigation dams (Fig. 1) . Two stations are 
located in the Upper Mississippi River, near the confluence with 



Illinois River fish populations February 28, 1993 

the Illinois, for comparison (Fig. 1) . The entire data set has 
only recently been transcribed to computer disks, and is still 
being verified against the original field data sheets. Although 
comparisons of the occurrence and general abundance of fishes can 
be made reliably across all the years (Tables 1-3) , other 
comparisons are based on two years, 1963 and 1992, for which data 
are fully verified. We believe these two years are broadly 
representative of the condition of fish populations in the 
Illinois River at the beginning of the survey and in the most 
recent 5 years. 

Species Composition and Abundance. A total of 91 species of 
fishes from 18 families, and five hybrids, have been collected 
during the electrof ishing survey from 1957 to 1992. Over the 
entire period, just five species dominated the upper river, with 
the introduced goldfish and carp ranking first and second in 
abundance (Table 1 and Fig. 2) . In recent years however, native 
species have returned to the upper river, and the electrof ishing 
catch is dominated by native minnows, green sunfish, and gizzard 
shad (Fig. 2). Carp now rank seventh in abundance (5.3% of the 
catch) , and native fishes such as smallmouth and largemouth bass 
and bluegill sunfish comprise 3 to 4.6% of the catch (Fig. 2). 
Carp and goldfish are more tolerant than most native species of 
the low oxygen levels and toxic materials associated with heavy 
pollution loads, and their populations often expand in the 
absence of pollution-intolerant predators (e.g., the basses) 
(Lubinski and Sparks 1981) . The change to a more balanced fish 
community dominated by native species reflects improvements in 
water guality, as corroborated by a decline since 1975 in the 
toxicity attributable to ammonia, which is associated with sewage 
effluents (Fig. 3) . Another indication of improvement was the 
collection, independent of the electrof ishing survey, of three 
state endangered fishes in the upper river in the period 1987-89: 
the pallid shiner, river redhorse, and greater redhorse (Page et 
al. 1992) . In contrast to dominance by only five species in the 
upper river, 12 species were regularly abundant in the middle 
river and 10 in the lower river during most of the 35-year period 
covered by the electrof ishing (Tables 2 and 3) . The common carp 
ranked first in abundance in the lower river and second in the 
middle river in 1963, but was superseded by the bluegill by 1992 
(Figs. 4 and 5) . In the lower river, largemouth bass ranked 
fourth in abundance, after gizzard shad and carp, and comprised 
9% of the catch (Fig. 5) . 

Some species that were once common are now virtually absent 
(Starrett 1971; Sparks 1977; INHS unpublished data). The yellow 
bass, northern pike, and black buffalo use flooded terrestrial or 
aquatic vegetation for spawning and may have declined because of 
alterations in the floodpulse or because of the loss of aquatic 
plants and general deterioration of shallow backwaters due to 
excessive sedimentation. 



Illinois River fish populations February 28, 1993 

External Abnormalities. The incidence of external abnormalities 
(eroded fins, sores) in the fish has declined markedly between 
1963 and 1992, indicating a general improvement in water quality. 
However, abnormalities occur more frequently in fishes that 
contact bottom sediments (catfish, carp) than in fish that occupy 
the water column (bass, bluegill) , indicating that there are 
pollutants or pathogens associated with the sediments (Fig. 6) . 
Also, the incidence of abnormalities increased in the upstream 
direction in both 1963 and 1992, implicating the Chicago-Joliet 
area as the source of whatever causes the abnormalities. 

Body Condition. Fish biologists use a relative weight index (Wr) 
to indicate the general condition of fish. A value of one 
indicates that the weight of the fish in relation to its length 
is comparable to the top quartile of the fish that have been 
sampled in the same geographic region. A value below one 
indicates that the fish is underweight, and may not be growing 
well. In general, fish in the Illinois River that feed in the 
water column, such as bluegill, appear to be in good body 
condition, whereas fish that feed on the bottom, such as carp, 
are in relatively poor condition (Table 4) . Sparks (1984) and 
Starrett (1971) related the poor condition of bottom-feeding 
fishes to the lack of invertebrates (fingernail clams, aquatic 
worms and insects) on the bottom of the river. The paucity of 
bottom-dwelling invertebrates was in turn linked to the 
occurrence of toxic levels of ammonia in the sediments (Fig. 7) . 
Sediment toxicity increased upstream, implicating the Chicago 
area as the likely source. 

Summary of Trends and Current Status. The relatively poor body 
condition of bottom-feeding fishes and the relatively high 
incidence of sores and eroded fins in fish that contact the 
bottom of the river indicates lingering problem with sediments. 
A shift from dominance by goldfish and carp to a mixed community 
with substantial representation of native species, including 
sport fishes, indicates a general improvement in the water 
quality of the Illinois River. In addition to the intrinsic 
value of conserving and restoring native aquatic species in the 
Illinois River, there are recreational and economic benefits as 
well. As a result of improvements in water quality and fish 
populations, the river currently provides 2 million angling-days 
per year, valued at $40 million annually, based on 1989 figures 
(Conlin 1991) . Sauger populations in the upper river and bass 
populations in the middle and lower river now support 
nationally-ranked tournaments that are important to local and 
regional economies. Peoria, for example, will host a 1993 
Bassmaster Superstars tournament, with the option to host it 
again in 1994 and 1995. Marketing studies indicate the 
Superstars tournament brings $6-8 million to the host city in 
expenditures by competing anglers, spectators, and news media, 
and the publicity boosts interest in outdoor recreation at the 
host site even after the tournament (Conlin 1991; Mr. Jack 



Illinois River fish populations February 28, 1993 

Ayersman, outdoor writer for the Peoria Journal Star, personal 
communication) . 

PROGNOSIS 

Despite the change to a better balanced fish community in the 
Illinois River over the last 30 years, with native species 
gaining in dominance over introduced species, problems remain. 
In addition to sediment quality, these include introduction of 
additional non-native species, chemical contamination of fish, 
lack of critical information on fish and fisheries, general 
habitat deterioration and diminishment of the floodpulse, and 
lack of a concept of what a river-floodplain ecosystem is, as a 
basis and guide for management and restoration. 

Non-native species. It is ironic that improvements in waste 
treatment in the Chicago area lower the pollution barrier that 
once kept non-native species introduced to the Great Lakes from 
invading the entire Mississippi drainage via the man-made link to 
the Illinois River. The latest introduction is the European 
zebra mussel, first reported in the Illinois River in June 1991, 
now found throughout the Illinois River and at scattered 
locations in the Upper Mississippi, Ohio, and Tennessee rivers 
(Sparks and Marsden 1991; Sparks 1991). This mussel is capable 
of reaching densities of thousands per square yard and could have 
indirect effects on fish populations by altering the base of the 
food chain and smothering native mussel beds that some fishes use 
as spawning substrates. The white perch (originally from the 
Atlantic coast) has invaded the Illinois River from the Great 
Lakes within the last two years and the European river ruffe (a 
small fish) is likely to follow soon. Invaders from the 
Mississippi include the Asiatic clam, Corbicula , which is likely 
to be followed by the grass carp and the bighead carp, also from 
Asia. The Asiatic clam arrived in 1971. 

Chemical Contamination of Fish. While fish community changes 
provide indirect evidence that water quality has improved, 
sediments in some areas, especially on the upper river, contain 
elevated levels of toxic substances such as heavy metals and 
synthetic organic chemicals (Essig 1991; Illinois Environmental 
Protection Agency 1992) , which can accumulate in fish tissues 
from direct contact with sediments or be magnified in 
concentration through the food chain from sediments to benthic 
invertebrates to invertebrate-feeding fishes. Fish consumption 
advisories are in effect for the upper river and the middle river 
to the Peoria Dam for bottom-feeding fishes such as freshwater 
drum, channel catfish, smallmouth buffalo, and carp over 15 
inches (38 cm) (Illinois Department of Conservation 1993) . The 
persistent nature of the toxicants makes this problem 
particularly intractable. 



Illinois River fish populations February 28, 1993 

Lack of Critical Information on Fish and Fisheries. As 
encouraging as the redevelopment of the Illinois River sport 
fishery is, there is too little information available to manage 
and regulate this fishery. No creel surveys have been done to 
determine how many fish are being harvested. The effects of 
moving several hundred of the largest bass in the La Grange reach 
of the river upstream, through the lock and dam into the Peoria 
reach is not known, yet this is what happens with each major bass 
fishing tournament held at Peoria, because most of the fish are 
caught in the La Grange reach and released, after weighing, in 
the Peoria reach. The nationally-ranked tournaments and local 
fishing may be based on just a few year-classes of bass and 
sauger, and the number of large fish may dwindle soon, unless the 
critical spawning and wintering habitats and conditions can be 
identified and preserved. Also, the population of large fish may 
be quite small, but the fish are concentrated and easily caught 
during low water levels because they are forced out of backwaters 
made shallow by excessive sedimentation. If this is the case, 
then length restrictions and catch-and-release regulations would 
help maintain the supply of large fish, and restoration of 
backwaters would help increase the supply. 

Even less is known about the non-game species and endangered 
species, so the most prudent course here is to restore, to the 
extent possible, the natural habitats and floodpulse that 
maintained these species prior to disturbance. More will be said 
about this approach below. 

Habitat Deterioration. Although the black basses, sunfishes, and 
crappies (Family Centrarchidae) are responding favorably to 
improvements in chemical water quality, particularly in the upper 
river, further improvements in the middle river and lower river 
may be limited by continuing heavy sediment loads and 
deterioration of backwater habitats. Suspended sediment 
concentrations have decreased over the past 15 to 2 years (late 
1970 's to late 1980' s) in the Upper Mississippi River but have 
not changed significantly in the Illinois River (Gaugush 1993; 
Gaugush 1992) . Suspended sediment not only reduces the 
visibility sight predators need to find their food (and 
fishermen's lures), it reduces the amount of food as well 
(Vinyard and O'Brien 1976; Buck 1956). The centrarchids also 
have complex reproductive and social behaviors that depend on 
visual cues, and their eggs and larvae are susceptible to 
smothering with sediment or predation if the guardian male cannot 
see and defend them. The recovery of many other species (e.g., 
yellow bass, northern pike, black buffalo, and several species of 
minnows and darters) likewise is limited by excessive turbidity, 
unstable bottoms, and absence of aquatic vegetation. 

Lack of an Organizing Concept for Management and Restoration. 
Unfortunately, the current remedies for habitat deterioration may 
be ineffective and may create other problems for aquatic 



Illinois River fish populations February 28, 1993 

organisms because the remedies are not founded on a holistic 
understanding of the river-floodplain ecosystem. There currently 
are nine multimillion-dollar Habitat Rehabilitation and 
Enhancement Projects in various stages of design or construction 
on the Illinois River, all part of the Environmental Management 
Program for the Upper Mississippi River and Illinois River 
conducted by the U.S. Army Corps of Engineers, U.S. Fish and 
Wildlife Service, and the five states of the Upper Mississippi 
River Basin, including Illinois. There are many aspects to these 
large, complex projects, but most involve keeping sediment-laden 
river water out of floodplain impoundments to the maximum extent 
possible. These techniques are expected to encourage the growth 
of aquatic plants in the clear water behind levees or moist soil 
plants in impoundments that are drawn down to expose mudflats. 
While these measures will probably benefit ducks and geese, and 
fish that are stocked in the impoundments, the ecosystem 
functions of flood storage and conveyance and use by migratory 
fishes will not be restored. There are considerable economic 
costs associated with replacing the functions once provided by 
the natural floodpulse of the river with human control 
(construction and maintenance of levees, operation of pumps and 
gates, production of fish in hatcheries for stocking in 
floodplain impoundments) . Also, it is unlikely that the 
artificially-maintained impoundments will provide the conditions 
necessary for maintenance of all the species of plants and 
animals that occurred in the natural river-floodplain ecosystem. 

An ecosystem-based perspective would lead to several alternative 
approaches. First, the river would be recognized as a product of 
its drainage basin. The tributary basins that currently 
contribute the most sediments to the river would be identified 
and prioritized for erosion control and bank stabilization, with 
most attention going to tributary segments and subbasins that in 
turn yield the most sediment. Erosion control would focus on the 
near-stream environment. Second, the floodpulse would be 
recognized as the primary driving force responsible for the past 
biological productivity of the river. This recognition would 
lead to a long-term plan to restore both the floodplain and the 
floodpulse, although existing levees might be used in the interim 
to keep river water out until the erosion control measures in the 
basin were effective in reducing sediment loads. The function of 
the low-water part of the floodpulse in drying and compacting 
floodplain soils would be recognized and allowed to occur. 
Adoption of such an ecosystem-based approach is likely to more 
effective and less costly in the long run than the current 
approach of compartmentalizing the floodplain and excluding the 
river. 



Illinois River fish populations February 28, 1993 Page 1 



LITERATURE CITED 

Bavlev, P.B. 1991. The flood pulse advantage and the 

restoration of river-f loodplain systems. Regulated Rivers: 
Research and Management 6:75-86. 

Buck, D. H. 1956. Effects of turbidity on fish and fishing. 
Oklahoma Fisheries Research Laboratory. Report No. 56. 
Norman, Oklahoma. 

«„«-n« m 1991 Illinois River fisheries and wildlife 

resources Pages IT-2 6 in Holly Korab, ed. Proceedings of 
5S 199? Governor's Conference on the Management of the 
Illinois River System. Third Biennial conference, October 
22-23, Peoria, IL. 166 p. 

Essia H W. 1991. Chemical and biological monitoring of the 
Essig, «•«• +;~7; River pages 68-77 in Holly Korab, ed. 

Conference, October 22-23, Peoria, IL. 166 p. 
Gaugush, R.F. 1993. Kriging and cokriging applied to water 

Reprint No. 93-R027. 18 p. 
Gaucmsh R.F. 1992. Recent trends in water quality of the 

Inc. Volume 24. 76 p. 

~ -o ,«^ m t vpiiv 1981. Summary resource 
Gilbertson, D.E., and T.J. Keiiy. ±*° q v «,fcam upper 
description Upper Mississippi River System. upp 
Mississippi River Basin Commission. Biology vox 

Springfield, IL. 
Illinois Environmental Protection Agency. 1976. Water Quality 
network 1975 summary of data Volume 2. Illj no ^ s 
Environmental Protection Agency, Springfield, IL. 245 p. 

■i . *~* -o v cnarlcs 1989. The flood pulse 

Junk, W.J./ P.B. Bayley, and R.E. Spar*-. ^' . D ^ p 
concept in river-f loodplain systems. Pages 110 7 in J.P. 
Dodge, ed. Proceedings of the International Large River 
^mposium! Canadian Special Publication Fisheries and 
Aquatic Science 106. 



Illinois River fish populations February 28, 1993 Page 2 

Lubinski, K.S., and R.E. Sparks. 1981. Use of bluegill toxicity 
indexes in Illinois. Pages 324-337 in D.R. Branson, and K.L. 
Dickson, eds. Aquatic Toxicology and Hazard Assessment. 
American Society for Testing and Materials, Philadelphia, PA. 
471 p. 

Lubinski, K.S., R.E. Sparks, and L.A. Jahn. 1974. The 

development of toxicity indices for assessing the quality of 
the Illinois River. Water Resources Center, University of 
Illinois, Urbana-Champaign, IL. 

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 No. 57, Urbana, IL. 
24 p. 

Murphy, B.R., D.W. Willis, and T.A. Springer. 1991. The 

relative weight index in fisheries management: status and 
needs. Fisheries 16:30-38. 

Page, L.M. , K.S. Cummings, C.A. Mayer, S.L. Post, and M.E. 

Retzer. 1992. An evaluation of the streams of Illinois 
based on aquatic biodiversity. Pages 402-417 in Biologically 
Significant Illinois Streams. Illinois Department of 
Conservation and Illinois Department of Energy and Natural 
Resources, Springfield, IL. 

Patterson Schafer, Inc. 1991. Report No. 91-37 comprehensive 
evaluation of water quality in the Chicago man-made waterway 
system 1990. Metropolitan Water Reclamation District of 
Greater Chicago, Chicago, IL. 

Polls, I., S.J. Sedita , D.R. Zenz, and C. Lue-Hing. 1991a. 
Report No. 91-21 comprehensive evaluation of water quality 
along the Illinois Waterway at Lockport, Morris, Starved 
Rock, Henry, and Peoria during 1990. Metropolitan Water 
Reclamation District of Greater Chicago, Chicago, IL. 

Polls, I., S.J. Sedita , D.R. Zenz, and C. Lue-Hing. 1991b. 
Report No. 91-24 comprehensive evaluation of water quality 
along the Illinois Waterway at 49 sampling stations from the 
Lockport Lock and Dam to the Peoria Lock and Dam during 1990. 
Metropolitan Water Reclamation district of Greater Chicago, 
Chicago, IL. 

Richards, T.E., P.D. Hayes, and D.J. Sullivan. 1991. Water 

resources data Illinois water year 1990 Volume 2. Illinois 
River Basin. U.S. Geological Survey, Urbana, IL. 

Sparks, R.E., P.E. Ross, and F.S. Dillon. 1992. Identification 
of toxic substances in the Upper Illinois River. Final 
Report. Illinois Department of Energy and Natural Resources. 
Contract No. WR3 6. 60 p. 



Illinois River fish populations February 28, 1993 Page 3 

Sparks, R.E. 1992. Risks of altering the hydrologic regime of 
large rivers. Pages 119-152 in J. Cairns, Jr., B.R. 
Niederlehner, and D.R. Orvos, eds. Predicting Ecosystem 
Risk. Advances in Modern Environmental Toxicology. Volume 
20. Princeton Scientific Publishing Company, Inc. 
Princeton, N.J. 347 p. 

Sparks, R.E., and E. Marsden. 1991. Zebra mussel alert. Illinois 
Natural History Survey Reports, No. 310. Champaign, IL. 

Sparks, R.E. 1991. Zebra mussel update. Illinois Natural History 
Survey Reports, No. 311. Champaign, IL. 

Sparks, R.E., P.B. Bayley, S.L. Kohler, and L.L. Osborne. 1990. 
Disturbance and recovery of large floodplain rivers. 
Environmental Management 14 (5) : 699-709 . 

Sparks, R.E. 1984. The role of contaminants in the decline of 
the Illinois river: Implications for the Upper Mississippi. 
Pages 25-66 in J.G. Wiener, R.V. Anderson, and D.R. 
McConville, eds. Contaminants in the Upper Mississippi 
River. Proceedings of the 15th Annual Meeting of the 
Mississippi River Research Consortium. Butterworth 
Publishers, Stoneham, MA. 368 p. 

Sparks, R.E., M.J. Sandusky, and A. A. Paparo. 1981. 

Identification of the water quality factors which prevent 
fingernail clams from recolonizing the Illinois River, Phase 
II. University of Illinois Water Resources Center Research 
Report No. 157. 52 p. 

Sparks, R.E. 1977. Environmental inventory and assessment of 
navigation pools 24, 25, and 26, Upper Mississippi and lower 
Illinois rivers. An electrof ishing survey of the Illinois 
River. University of Illinois Water Resources Center, 
Champaign, IL. UILU-WRC-77-0005. Special Report No. 5. 

Starrett, W.C. 1971. A survey of the mussels (Unionacea) of the 
Illinois River. A polluted stream. Illinois Natural History 
Survey Bulletin 30:267-403. Illinois State Natural History 
Survey, Urbana. 

Vinyard, G. L. , and W. J. O'Brien. 1976. Effects of light and 
turbidity on the reactive distance of bluegill (Lepomis 
macrochirus) . Journal of the Fisheries Research Board of 
Canada 33:2,845-2,849. 



Figures and Tables 



Figure 1. Locations of 28 electrof ishing stations along the 
Illinois Waterway and Mississippi River. Stations 27 and 28 are 
on the Mississippi River, just below the confluence with the 
Illinois River. (Data from stations 27 and 28 are not used in 
the following analyses because data have been gathered for only a 
few most recent years. Future analyses will, however, use data 
from these stations as representing control sites [i.e., being 
least impacted by pollution from the Chicago-Joliet area] , for 
comparison with Illinois Waterway data.) Stations 1 and 2 are on 
the Des Plaines River. The rest of the stations are on the 
Illinois River. The Illinois Waterway is divided into reaches 
defined by navigation dams. The Alton Dam on the Mississippi 
River also maintains water depths for navigation on the lower 80 
miles of the Illinois River. In upstream order, the other dams 
and the reaches they control are: La Grange, Peoria, Starved 
Rock, Marseilles, and Dresden. The reaches can be grouped based 
upon the amount of aquatic habitat (side channels, backwaters, 
and floodplain lakes) available per unit length of river as 
follows (data from Gilbertson and Kelly 1981) : 

Aquatic Habitat 
Reach (ha/km) (acres/mi) 



Upper River 



Dresden 


39 


153 


Marseilles 


12 


46 


Starved Rock 


38 


152 



Middle River 



Peoria 


108 


425 


La Grange 


85 


334 


iwer River 






Alton 


40 


157 



The upper river flows through a much narrower valley than the 
other sections and has the least amount of aquatic habitat, due 
to a different geologic history than the rest of the river. The 
middle river has the most aquatic habitat, while the lower river 
has had most of its floodplain aquatic habitat converted to 
agriculture, and is now more similar to the upper river in terms 
of available floodplain habitat. The gradient in the upper river 
is 1 to 2 feet per mile (200 to 400 cm/km) , while the gradient in 
the middle and lower sections is only 0.1 to 0.2 foot per mile 
(20 to 40 cm/km) . 



Mississippi 
River 




Lake 
Michigan 



Chicago 



Brandon 
Roads 



Kankakee 
River 



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River 



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Figure 3. Mean Bluegill toxicity index (BTI) calculated for 1975 
(16 stations) and 1990 (66 stations) . The BTI was developed by 
Lubinski et al. (1974) and can be used to compare the relative 
toxicities of different substances to a reference organism, the 
bluegill. Calculation of the BTI requires values for pH, water 
temperature, dissolved oxygen concentration, fish weight, and 
concentration of the toxicant (data from Illinois Environmental 
Protection Agency 1976; Richards et al. 1991; Patterson Schafer, 
Inc. 1991; Polls et al. 1991a; Polls et al. 1991b). A BTI of 1.0 
is defined as lethal to 50% of the bluegills exposed for 96 hr. 
Furthermore, experience has shown a BTI of 0.2 marks a transition 
state above which bluegill-largemouth bass communities change to 
a carp-dominated community (BTI > 0.2) (Lubinski and Sparks 
1981) . Although there was a substantial decline in ammonia 
toxicity between 1975 and 1990, the trend of increased toxicity 
toward the Chicago area was still evident in 1990. 



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Table 4. Mean relative weight (Wr) for bluegill and carp for 
1963, 1975, and 1991. Wr is determined by dividing an individual 
fish's weight by a length-specific standard weight (Ws) , where Ws 
represents the top quartile of fish from a specific region 
(Murphy et al. 1991). A Wr equal to or greater than 1.0 
indicates a healthy fish and, therefore, favorable ecological 
conditions, while a Wr less than 1.0 may indicate a food supply 
problem or some other factor (pollution stress) which is 
unhealthful to fish. Bluegill, which mainly inhabit the water 
column rather than foraging on the bottom, had a mean Wr close to 
1.0 for 1963, 1975, and 1991, indicating that food supply may not 
be a problem for these species. In contrast, mean Wr's for carp, 
a bottom-feeding omnivore, were consistently less than 1.0 for 
all three years, indicating their environment may be less than 
conducive to healthy growth or that the food supply is limited in 
quantity or quality. Sparks (1984) and Starrett (1971) related 
the poor condition of bottom-feeding fishes to the lack of 
invertebrates (fingernail clams, aquatic worms and insects) on 
the bottom of the river. The lack of invertebrates is in turn 
linked to the occurrence of toxic levels of ammonia in the 
sediments (see Fig. 7) . 



Bluegill Carp 



Year N Mean Wr N Mean Wr 



1963 50 0.914 995 0.877 

1975 123 0.984 449 0.781 

1991 347 1.06 114 0.795