Long Term Resource Monitoring Program

 Technical Report 

2008-T001

March 2008

Effect of a Recently Completed Habitat Rehabilitation 

and Enhancement Project on Fish Abundances in 

La Grange Pool of the Illinois River using Long Term 

Resource Monitoring Program Data
Long Term Resource Monitoring Program Technical Reports

provide Long Term Resource Monitoring Program 

partners with scientific and technical support.

All reports in this series receive anonymous peer review.

Cover photo: Aerial photograph of Lake Chautauqua and Illinois River. 

Photo taken by William Starrett, October 27, 1970 

Mention of trade names or commercial products does not constitute endorsement

or recommendation for use by the U.S. Department of the Interior, U.S. Geological Survey.
Effect of a Recently Completed Habitat Rehabilitation and 

Enhancement Project on Fish Abundances in La Grange Pool 

of the Illinois River using Long Term Resource Monitoring 

Program Data

by

Timothy M. O’Hara, Michael A. McClelland, Kevin S. Irons, Thad R. Cook, 

and Greg G. Sass

Report submitted to

U.S. Army Corps of Engineers 

Rock Island District, Clock Tower Building

P.O. Box 2004

Rock Island, Illinois 61204-2004

March 2008

U.S. Geological Survey

Upper Midwest Environmental Sciences Center

2630 Fanta Reed Road

La Crosse, Wisconsin 54603
Suggested citation:

O’Hara, T. M., M. A. McClelland, K. S. Irons, T. R. Cook, and G. G. Sass. 2008. Effect of a recently completed Habitat Rehabilitation and Enhancement Project on fish abundances in La Grange Pool of the Illinois River using Long Term Resource 

Monitoring Program data. U.S. Geological Survey, Upper Midwest Environmental Sciences Center, La Crosse, Wisconsin. 

LTRMP Technical Report 2008-T001. 16 pp. (Reference 2006APE17b.)

Additional copies of this report may be obtained from the National Technical Information Service, 5285 Port Royal Road, 

Springfield, VA 22161 (800-553-6847 or 703-487-4650). Also available to registered users from the Defense Technical 

Information Center, Attn: Help Desk, 8725 Kingman Road, Suite 0944, Fort Belvoir, VA 22060-6218 (800-225-3842 or 703-767-

9050).
iii

Contents

Page

Abstract........................................................................................................................................................1

Introduction..................................................................................................................................................1

Methods........................................................................................................................................................2

La Grange Pool Study Area...................................................................................................................2

Lake Cautauqua Study Area..................................................................................................................2

Long Term Resource Monitoring Program Fish Sampling ...................................................................3

Local, Regional, and Pool Scale Habitat Rehabilitation and Enhancement Project Effects.................5

Habitat Rehabilitation and Enhancement Project Fish Escapement Sampling .....................................5

Results..........................................................................................................................................................6

Local Scale (1 RM) Habitat Rehabilitation and Enhancement Project Effects.....................................6

Regional Scale (~10 RM) Habitat Rehabilitation and Enhancement Project Effects ...........................8

Pool Scale Habitat Rehabilitation and Enhancement Project Effects .................................................11

Habitat Rehabilitation and Enhancement Project Fish Escapement ..................................................11

Discussion..................................................................................................................................................11

Management Implications..........................................................................................................................15

Acknowledgments......................................................................................................................................15

References..................................................................................................................................................15

Figures

Number Page

1. Map of the Chautauqua National Wildlife Refuge illustrating the south cell water-control 

structure...............................................................................................................................................3

2. Day electrofishing mean catch per run for the pre- and post-Habitat Rehabilitation and 

Enhancement Project periods by Illinois River mile...........................................................................6

3. Mini-fyke net mean catch per net for the pre- and post-Habitat Rehabilitation and Enhancement 

Project periods by Illinois River mile..................................................................................................7

4. Ratio of pre- to post-Habitat Rehabilitation and Enhancement Project day electrofishing 

mean catch per run by Illinois River mile and the control and impacted river miles used 

in the Before-After Control-Impact design .........................................................................................7

5. Ratio of pre- to post-Habitat Rehabilitation and Enhancement Project mini-fyke net mean catch 

per net by Illinois River mile and the control and impacted river miles used in the Before-After 

Control-Impact design.........................................................................................................................8

6. Ratio of pre- to post-Habitat Rehabilitation and Enhancement Project day electrofishing 

mean catch per run by the La Grange Pool regional area (~10 River Miles)......................................9

7. Ratio of pre- to post-Habitat Rehabilitation and Enhancement Project mini-fyke net mean catch 

per net by the La Grange Pool regional area (~10 River Miles) .........................................................9

8. Ratio of pre- to post-Habitat Rehabilitation and Enhancement Project day electrofishing 

mean catch per run in backwaters of La Grange Pool.......................................................................10

9. Ratio of pre- to post-Habitat Rehabilitation and Enhancement Project mini-fyke net mean catch 

per net in backwaters of La Grange Pool..........................................................................................10

10. Day electrofishing and mini-fyke net mean catches in La Grange Pool from 1993 to 2005 ............12

11. Non-metric multidimensional-scaling ordination of abundance data from day electrofishing 

(data were square-root transformed and ecological similarity was measured using the Bray-
iv

Curtis Similarity metric [Bray and Curtis 1957]) ............................................................................13

12. Non-metric multidimensional-scaling ordination of abundance data from mini-fyke nets (data 

were square-root transformed and ecological similarity was measured using the Bray-Curtis 

Similarity metric [Bray and Curtis 1957]) ........................................................................................13

13. Estimates (fish in millions) from Lake Chautauqua escapement sampling ......................................14

14. Percent fish-species composition caught during Lake Chautauqua escapement sampling in 

1996, 1997, and 2000........................................................................................................................14
v

Preface

The Long Term Resource Monitoring Program (LTRMP) was authorized under the Water Resources 

Development Act of 1986 (Public Law 99-662) as an element of the U.S. Army Corps of Engineers’ 

Environmental Management Program. The LTRMP is being implemented by the Upper Midwest 

Environmental Sciences Center, a U.S. Geological Survey science center, in cooperation with the five 

Upper Mississippi River System (UMRS) States of Illinois, Iowa, Minnesota, Missouri, and Wisconsin. 

The U.S. Army Corps of Engineers provides guidance and has overall Program responsibility. The mode 

of operation and respective roles of the agencies are outlined in a 1988 Memorandum of Agreement.

The UMRS encompasses the commercially navigable reaches of the Upper Mississippi River, as 

well as the Illinois River and navigable portions of the Kaskaskia, Black, St. Croix, and Minnesota 

Rivers. Congress has declared the UMRS to be both a nationally significant ecosystem and a nationally 

significant commercial navigation system. The mission of the LTRMP is to provide decision makers 

with information for maintaining the UMRS as a sustainable large river ecosystem given its multiple-use 

character. The long-term goals of the Program are to understand the system, determine resource trends 

and effects, develop management alternatives, manage information, and develop useful products.

This report was prepared under Strategy 3.3.2, Test and Assess the Effectiveness of Prototype 

Management, as specified in Goal 3, Develop Alternatives to Better Manage the Upper Mississippi River 

System of the Operating Plan (U.S. Fish and Wildlife Service 1993). This report was developed with full 

funding provided by the LTRMP.

Effect of a Recently Completed Habitat Rehabilitation and Enhancement 

Project on Fish Abundances in La Grange Pool of the Illinois River using 

Long Term Resource Monitoring Program Data

by

Timothy M. O’Hara, Michael A. McClelland, Kevin S. Irons, Thad R. Cook, and Greg G. Sass

Illinois Natural History Survey

Illinois River Biological Station

704 N. Schrader Avenue

Havana, Illinois 62644

Abstract: The Long Term Resource Monitoring Program (LTRMP) fish component monitors fish 

communities to test for changes in abundances and species composition in six regional trend areas 

of the Upper Mississippi River System. Using these data, we evaluated the ability of the LTRMP to 

detect changes in the fish community as a consequence of a habitat-enhancement project in La Grange 

Pool of the Illinois River. In 1996, initial phases of the Chautauqua National Wildlife Refuge Habitat 

Rehabilitation and Enhancement Project (HREP) south cell construction were completed with the goal 

of improving fish habitat in the pool. That year, an estimated 46 million fish representing 34 species 

were produced and discharged from the south cell of Lake Chautauqua. Whereas this response may 

indicate that the south cell serves as a spawning and nursery area for many fish species, no studies have 

tested for recruitment to the river fish community. We used geographic information system coverage at 

three spatial scales in the main-channel and side-channel strata to illustrate potential fish-community 

responses. At these spatial scales (local 1 river mile [RM], regional ~10 RMs, and pool wide 80 RMs), 

we assessed fish catch-per-unit-effort (CPUE) data collected from mini-fyke net and day electrofishing 

among pre- (1993–1995) and post-HREP (1996–2005) periods of the Chautauqua National Wildlife 

Refuge HREP. Analysis of Similarity results demonstrated no significant differences among periods in 

fish CPUE (P > 0.05). Our results may indicate that (1) the LTRMP sampling design lacked sufficient 

statistical power to detect effects of the HREP, (2) the LTRMP sampling design lacked the spatial and 

temporal resolution to detect effects, (3) the Lake Chautauqua HREP has not been established long 

enough to detect long-term trends in fish production, or (4) the HREP had no effect on fish recruitment 

to the Illinois River. Nevertheless, our results clearly show that backwaters are major fish producing 

areas in La Grange Pool and future HREPs to enhance backwater fish habitat may be critical to the 

long-term sustainability of the Illinois River fish community. As a result of our findings, we suggest 

that an intensive study at defined temporal and spatial scales may be required to detect changes in the 

fish community in La Grange Pool as a consequence of HREPs.

Key words: fish communities, Habitat Rehabilitation and Enhancement Project, Illinois River, Lake 

Chautauqua, Long Term Resource Monitoring Program

Introduction

In 1986, the Water Resources Development 

Act authorized the implementation of a Long Term 

Resource Monitoring Program (LTRMP) and 

Habitat Rehabilitation and Enhancement Projects 

(HREPs) for the Upper Mississippi River System 

(UMRS) as elements of the U.S. Army Corps of 

Engineers Environmental Management Program. 

Although the LTRMP (monitoring of biological 

and water resources) and HREPs (restoration and 

protection of critical fish and wildlife habitat) were 

developed separately, opportunities exist to use 

LTRMP data to assess the effectiveness of HREPs 

in achieving habitat restoration and conservation 

goals.
2

Since 1990, the LTRMP and two HREPs have 

been implemented in La Grange Pool of the Illinois 

River. The LTRMP fish component has conducted 

5,637 collections capturing about 1.25 million 

fish (89 species) since 1993, representing one of 

the most comprehensive data sets on the Illinois 

River. The primary objectives of the LTRMP are 

to detect long-term trends in the key regional trend 

areas and to test for correlations among trends 

and environmental variables to gain insight into 

possible cause-and-effect relations.

In 1992, the Chautauqua National Wildlife 

Refuge (U.S. Fish and Wildlife Service) was 

chosen for a HREP. Prior to HREP construction, 

Lake Chautauqua was separated from the main 

stem of the Illinois River by a levee and, before 

1992, was shallow and turbid with resuspension 

of sediments dominating the limnology of the 

ecosystem (Irons et al. 1997). The major features 

of the project were to repair a cross dike, which 

effectively divided the lake into two separate cells 

(north and south), and add a stop-log water-control 

structure on the south cell. The management plan 

for the north cell was to maintain stable water 

levels in an effort to promote the establishment 

of submersed aquatic vegetation and to provide 

aquatic habitat for fish, migratory waterfowl, and 

shorebirds. The south cell was to be managed 

for moist-soil conditions to enhance habitat and 

food plants for migratory waterfowl. In 1996, 

initial phases of the south cell construction 

were completed with the stop-log water-control 

structure, spillways, and levee repair. While 

constructing the south cell, it was recognized 

that this area could serve multiple functions by 

providing spawning and nursery habitats to fish in 

the spring and early summer season and moist-soil 

seed production in fall for migrating waterfowl. 

Fish access from the Illinois River to Lake 

Chautauqua is provided by flood events that top the 

levee and water-control structure. Therefore, the 

south cell of Lake Chautauqua may be considered 

a semi-natural backwater lake that mimics the 

hydrologic regime of the Illinois River during some 

years and seasons.

The goal of our research was to use LTRMP 

fish-component data to test for changes in the 

La Grange Pool fish community (i.e., relative 

abundance) as a result of the Lake Chautauqua 

HREP. More specifically, we used LTRMP data 

to test for fish-community responses to the HREP 

at three spatial scales across pre- and post-periods 

of project implementation. In addition, we present 

fish-escapement and community-composition 

data from the Lake Chautauqua HREP to test for 

the presence or absence of fish production in the 

post-period.

Methods

La Grange Pool Study Area

La Grange Pool, with its extensive mosaic 

of aquatic habitats, is among the most diverse 

reaches of the UMRS. La Grange Pool spans 

approximately 80 miles of the Illinois River and 

is positioned between the Peoria Lock and Dam 

(River Mile [RM] 157.0) near Peoria, Illinois, and 

the La Grange Lock and Dam (RM 80.0) south 

of Beardstown, Illinois. La Grange Pool can be 

divided into three macrohabitats: main channel 

(2,441 ha), side channel (163 ha), and backwaters 

(11,762 ha).

Lake Chautauqua Study Area

Lake Chautauqua has been an integral 

component of the Illinois River National System 

since its purchase by the U.S. Fish and Wildlife 

Service in 1936. Prior to Lake Chautauqua’s 

acquisition, the area was comprised of a mosaic 

of floodplain forest and wetted habitats ranging 

from deep-water side channels to shallow pools 

and exposed soil areas (Starrett and Fritz 1965). 

However, by the early 1900s, major efforts 

had taken place to use this area for row-crop 

agriculture. In 1916, the Chautauqua drainage and 

levee district was created to facilitate agricultural 

practices. Several attempts were made to farm 

the drained land; however, in the mid-1920s, the 

land was abandoned because of high rate of crop 

failures from recurrent flooding. Following the 

purchase of the Lake Chautauqua area, the levees 

were maintained to allow minimum water-level 

management, but the lake generally was connected 

to the Illinois River (Irons et. al. 1997). Lake 

Chautauqua is between RMs 124 and 129.5 on La 

Grange Pool near Havana, Illinois (Figure 1). 
3

In the late 1960s, the 1,450 ha lake was 

divided into two basins (a 480 ha north cell 

and a 970 ha south cell) by a 1.6 km-long cross 

dike. The cross dike failed in 1970, and ensuing 

attempts to repair it were unsuccessful. In 1992, 

Lake Chautauqua was selected for a HREP in 

the Environmental Management Program for the 

UMRS. Project construction began in 1992 and 

was to be completed in four stages. During each 

construction stage, significant flooding delayed 

project completion. 

A major feature of the project was the repair 

of the cross dike, which effectively divided the 

lake into north and south cells again. In addition, 

a spillway and a stop-log water-control structure 

were constructed to facilitate more thorough 

dewatering of the south cell for moist-soil plant 

production. The primary purpose of the watercontrol structure was to incrementally control lake 

water levels. The control structure also is used to 

gravity drain the lower lake, which is why the sill 

is lower than the bottom of the lake. During an 

impending levee overtop, stop logs can be removed 

to expedite filling of the lower lake. Refuge 

personnel can remove stop logs with up to 3 ft of 

over-topping water. 

Before HREP construction, Lake Chautauqua 

was characterized as shallow and turbid, with 

high rates of sediment resuspension (Irons et al. 

1997). However, Havera (Irons et al. 1997) noted 

that the lake was an important resting area for 

migrating waterfowl in the Illinois River Valley 

portion of the Mississippi River Flyway and 

probably the most important waterfowl refuge in 

the Illinois River Flyway. Management actions 

for the south cell included manipulation of water 

Figure 1. Map of the Chautauqua National Wildlife Refuge illustrating the south cell water-control structure (inset). Map of La Grange Pool 

with selected backwaters enumerated (1-14). (1=Big Lake; 2=Duck Island; 3=Clear Lake; 4=Meyers Ditch; 5=Quiver Lake; 6=Matanzas Lake; 

7=Crane Lake; 8=Chain Lake; 9=Bach Slough; 10=Snicarte Slough; 11=Treadway Lake; 12=Wood Slough; 13=Muscooten Bay; 14=Lilly Lake.)

Clear Lake

Quiver Lake

South Cell

North Cell

La Grange Reach

Chautauqua National Wildlife Refuge

Control Structure

Lake Chautauqua

Illinois River

(1) (2)

(3) (4)

(5)

(6)

(7) (8)

(9)

(10)

(11)

(12)

1 mile

5 mile

(13)

(14)

(3)

(5)
4

levels to mimic a natural flood cycle similar to that 

described by the flood-pulse concept (Junk et al. 

1989). Coincidentally, normal spring flooding that 

generally occurs in the months of March through 

late June provided fish access to the south cell for 

feeding, spawning, and nursing. After spawning, 

seasonally managed July through September 

drawdowns via the stop-log structure could allow 

young-of-year, juvenile, and adult fish to escape 

from the cell into the main stem of the Illinois 

River and allow moist-soil plants to germinate on 

the newly exposed sediments. Precise management 

records of timing and rates of drawdown are not 

available as a consequence of lack of recording and 

high refuge-manager turnover.

Long Term Resource Monitoring Program 

Fish Sampling

Since 1989, the LTRMP has sampled fish in La 

Grange Pool. In the initial years of the LTRMP, a 

fixed-site sampling design was used throughout the 

pool. Therefore, inferences were site-specific and 

lack of randomization in the site-selection process 

allowed potential sampling bias into monitoring 

(Ickes and Burkhardt 2002). As a consequence, the 

LTRMP adopted a probabilistic design for annual 

site selection recognized as stratified random 

sampling to remove potential site-selection bias. 

This change, coupled with refined standardized 

protocols and sampling methods, significantly 

improved the scientific merit of the program 

(Gutreuter 1993). A complete outline of the 

LTRMP fish-sampling protocols can be found in 

Gutreuter et al. (1995). For our analyses, we used 

day electrofishing and mini-fyke net catch-perunit-effort (CPUE) from 1993 to 2005. Lubinski 

et al. (2001) noted that day electrofishing CPUE 

has the statistical power to detect changes for 

the greatest number of species relative to all the 

collection methods used in the LTRMP. Because 

the focus of our analysis was to use LTRMP 

data to test for the effects of HREPs, we also 

used mini-fyke net CPUE because it is the most 

effective gear for collecting young-of-year fish that 

may be recruiting to the main stem of the Illinois 

River. Also, to reduce bias associated with the 

influences of additional backwater fish production, 

we specifically analyzed main- and side-channel 

catches.

The LTRMP fish sites sampled from 1993 

to 2005 were classified to the nearest Illinois 

RM using ArcView 3.3 (Environmental Systems 

Research Institute 2002). Our classifications ranged 

from RM 80 at the La Grange Lock and Dam (the 

downstream end of the sample pool) to RM 158 at 

the Peoria Lock and Dam (the upstream end of the 

sample pool). We then separated fish-collection 

sites into three distinct spatial areas for analysis 

(local 1 RM, regional ~10 RMs, and pool wide ~77 

RMs). These spatial scales were selected because 

1-RM increments were the minimum sampling 

distance required to provide adequate sample sizes 

for statistical analyses.

We tested for temporal variation in fish 

responses to the Lake Chautauqua HREP at 

three spatial scales using abundance data from 

existing randomized LTRMP La Grange Pool 

day electrofishing and mini-fyke net catches. We 

conducted analyses at local (77 individual river 

mile classifications from HREP location), regional 

(eight, 10-RM circumference classifications 

of HREP location), and pool (~77 total river 

miles) spatial scales. Data were pooled from the 

pre- (1993–1995) and post-HREP (1996–2005) 

periods for the three spatial scales in an effort 

to gain adequate sample size for analyses, as an 

insufficient collection occurrence was evident 

with decreasing spatial resolution. We evaluated 

temporal variation at the pool scale and differences 

were tested over all years to determine potential 

fish-community changes at pre- and postconstruction periods of the Lake Chautauqua 

HREP. We used the Lake Chautauqua HREP 

fish-escapement data collected as part of the project 

monitoring to corroborate potential findings at both 

spatial and temporal scales. LTRMP collections 

were normally conducted in three standardized 

periods (with the exception of 2005; where early 

summer was omitted and only late summer and fall 

periods were sampled due to budget constraints).

LTRMP fish sampling is conducted in three 

general habitats (strata): main-channel borders, side 

channels, and contiguous backwaters. In an effort 

to alleviate potential discrepancies from backwater 

contributions, we only used side-channel and 

main-channel-border collections. Other backwaters 

probably exhibit some level of fish production 

within themselves, similar to Lake Chautauqua, 

making contributions to the fish population from 
5

outside areas difficult to evaluate because of 

differences in connectivity with the Illinois River.

Local, Regional, and Pool Scale Habitat 

Rehabilitation and Enhancement Project 

Effects

We tested for differences in total catches 

at local and regional intervals using a one-way 

Analysis of Variance (ANOVA). We made post hoc 

comparisons among local and regional intervals 

using a Tukey’s multiple-comparison procedure to 

identify potential specific significant differences 

at given intervals. We used linear regression to test 

for pool-scale changes in mean catches by gear 

type (dependent variable) over time (independent 

variable) with the null hypothesis of no change in 

mean catches across years (α = 0.05). We examined 

temporal fish-community differences of total 

catches using Analysis of Similarity (ANOSIM) 

to test for community-structure changes at preversus post-HREP intervals. Further validation of 

ANOSIM results were made via non-parametric 

multidimensional scaling (NMDS) plots. We used 

a Before-After Control-Impact (BACI; StewartOaten et al. 1986) design to test for changes in 

fish catches following the construction of the Lake 

Chautauqua HREP. We defined the control portion 

of La Grange Pool as RM 81 through 112 and RM 

134 through 157. The impacted site was defined as 

RM 113 through 133; the Lake Chautauqua HREP 

water-control structure is at RM 124. The impacted 

area was defined post hoc as ±10 RMs because 

this spatial resolution was determined to be the 

largest interval able to detect effects of the HREP. 

We conducted a series of two-sample paired t-tests 

assuming unequal variances between all river miles 

with a sample size greater than or equal to three 

before and after HREP construction in both the 

control and impacted portions of La Grange Pool. 

A minimum sample size of three is required to 

calculate a valid mean and variance for statistical 

tests. We assumed unequal variances among groups 

due to large deviations present in catches associated 

with the gears used. Day-electrofishing catches 

and mini-fyke net catches were both assessed 

independently in the BACI design. Adequate data 

were available to compare a total of 11 RMs for 

day-electrofishing runs before and after HREP 

construction (n = 7 control sites; n = 4 impacted 

sites). Ten sites were compared for mini-fyke net 

catches (n = 6 control sites; n = 4 impacted sites). 

We also tested for differences in day-electrofishing 

and mini-fyke net catches within the control and 

impacted regions among pre- and post-HREP 

periods using a one-way ANOVA. In all parametric 

statistical tests, we used the null hypothesis of 

no difference in catches by gear among periods 

or regions at the α = 0.05 level. In addition to 

the main- and side-channel fish data, we also 

analyzed backwater data from day-electrofishing 

and mini-fyke nets to demonstrate the flexibility of 

the LTRMP fish data and to search for differences 

among the HREP and local backwaters. This 

comparison was made to determine the level of fish 

production from adjacent backwaters. No statistical 

tests were conducted because pre-escapement 

data from the Lake Chautauqua HREP were not 

available.

Habitat Rehabilitation and Enhancement 

Project Fish Escapement Sampling

In 1996, initial phases of the HREP 

construction were complete and post-HREP 

fish monitoring was conducted intermittently 

to evaluate the success of the project. We made 

fish collections from the south cell in three postproject years (1996, 1997, and 2000). Due to the 

unpredictable nature of the Illinois River, each 

study year was distinctly unique in its hydrology 

and management; therefore, sampling episodes 

were not conducted during a set time frame. For 

example, timing of our samples were constrained 

due to the management goals of the south cell in 

that distinctive moist-soil plant communities will 

grow at various times of the summer drawdown 

period. As mentioned previously, management 

records of drawdown timing and rates were not 

available during our sample years. To evaluate fish 

production occurring in the south cell, we initiated 

a fish-escapement monitoring program during 

dewatering (Irons et al. 1997). Although sample 

periods varied among the monitoring years, our 

specific objective was to estimate the number of 

actively swimming and drifting young-of-year fish 

released into the Illinois River from the south cell 

of Lake Chautauqua. The water-control structure at 

the south cell consists of four gates approximately 

1.5 m wide. We collected escaping fish with small 
6

mesh-hoop nets (standard LTRMP hoop net [1.2 

m diameter] lined with 3-mm “Ace”-type nylon 

netting) and an ichthyoplankton net (500-μm 

mesh). We fished nets in the effluent of the 

structure for 1 to 15 min; sample time was based 

on the amount of fish collected during the initial 

net sets. All fish caught were counted, measured, 

and identified to family and species, if feasible. We 

used General Oceanics flow meters to determine 

the amount of water sampled by each net. We 

calculated estimates of the total numbers of fish 

escaping from the south cell separately for hoop 

and ichthyoplankton nets during each escapement 

period. The number of samples varied in each of 

the years that escapement data were collected. 

Sample sizes for escapement collections were not 

standardized among years because we were simply 

testing for presence or absence of fish production 

from Lake Chautauqua.

Results

Local Scale (1 RM) Habitat Rehabilitation and 

Enhancement Project Effects

Post-HREP day electrofishing mean catches 

per run were higher in 64% of the individual river 

miles where data were available for each sample 

period (Figure 2). The largest variation in catch 

was RM 123, which had pre-HREP mean catches 

of 157 fish and post-HREP mean catches of 6,892 

fish per run. River mile 123 is 1 RM downstream of 

the Lake Chautauqua control structure.

Post-HREP mini-fyke net mean catches per net 

were higher in 86% of the individual river miles 

where data were available for each sample period 

(Figure 3). The largest variation in catch was RM 

135, which had a pre-HREP mean catch of 19 fish 

and post-HREP mean catch of 7,106 fish per net. 

River mile 135 is 13 RMs upstream of the Lake 

Chautauqua control structure.

Using the BACI design, significantly higher 

catches were observed in day-electrofishing runs 

and mini-fyke net sets in the HREP impacted 

area following construction. No statistically 

significant differences in catches for both gears 

were observed in control portions of La Grange 

Pool among periods (P > 0.05). On average, 

catches for day-electrofishing runs in control 

portions of the pool were 142 and 150 fish per run 

before and after HREP construction, respectively 

(Figure 4). Catches in mini-fyke nets averaged 

85 and 418 fish per set among periods; however, 

catches did not vary significantly among individual 

control river miles (Figure 5). In the impacted 

Figure 2. Day electrofishing mean catch per run for the pre- and post-Habitat Rehabilitation and Enhancement Project periods by Illinois River 

mile (pre-HREP mean catch = -55.564+1.878* river mile, n = 59; df = 1,57; f = 2.328; P = 0.133; r2 = 0.022, 

post-HREP mean catch = -17.305+2.856*river mile, n = 59; df = 1,57; f = 0.305; P = 0.583; r2 = 0).

River miles

Mean catch per run

PRE POST

Lake Chautauqua

control structure

Control Impact Control

0

10 0 0

2000

3000

4000

5000

6000

7000

8000

River miles

Mean catch per run

PRE POST

Control Impact Control

Lake Chautauqua control structure

81

8385

87

89

91

93

95

97

99

101

103

105

107

109111

113

115

117119121

123

125127

129

131

133

135

137

139

141

143

145

147

149

151

153

155

157
7

Figure 3. Mini-fyke net mean catch per net for the pre- and post-Habitat Rehabilitation and Enhancement Project periods by Illinois River 

mile (pre-HREP mean catch = -886.631+9.77* river mile, n = 43; df = 1,41; f = 3.596; P = 0.065; r2 = 0.058, post-HREP mean catch = -1020.833 

+ 15.513*river mile, n = 41; df = 1,94; f = 1.94; P = 0.17; r2 = 0.022).

Figure 4. Ratio of pre- to post-Habitat Rehabilitation and Enhancement Project day electrofishing mean catch per run by Illinois River mile and 

the control and impacted river miles used in the Before-After Control-Impact design.

0

10 0 0

2000

3000

4000

50 0 0

6000

70 0 0

8000

River Miles

Mean catch per net

PRE POST

River Miles

Mean catch per net

PRE POST

8181

83838585

8787

8989

9191

9393

9595

9797

9999

101 101

103 103

105 105

107 107 107 107

109 109 109 109111 111 111 111

113 113 113 113

115 115 115 115

117 117119 119121 121

123 123

125 125127 127

129 129

131 131

133 133

135 135

137 137

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141 141

143 143

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151 151

153 153

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Lake Chautauqua control structure

River Miles

log pre:post mean catch per run

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0.001

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81

8385

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103105

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Control Impact Control

log pre:post mean catch per run

Control Impact Control
8

region, mean catch rates in day-electrofishing runs 

increased from 173 to 215 per run among periods. 

Statistically significant differences in electrofishing 

catches were observed for RM 113 (117 fish 

pre-HREP, 190 fish post-HREP; n = 135; df = 129; 

t = 2.3; P = 0.02), RM 121 (40 fish pre-HREP, 

179 fish post-HREP; n = 43; df = 39; t = 2.33; 

P = 0.02), and RM 122 (67 fish pre-HREP, 122 fish 

post-HREP; n = 30; df = 26; t = 2.05; P = 0.05). 

Average mini-fyke net catches increased from 

48 to 1,960 fish per set before and after HREP 

construction in the impacted site. Statistically 

significant differences in mini-fyke net catches 

were observed for RM 121 (26 fish pre-HREP, 

166 fish post-HREP; n = 30; df = 27; t = 3.12; 

P = 0.004) and RM 126 (32 fish pre-HREP, 115 

fish post-HREP; n = 7; df = 5; t = 3.59; P = 0.02). 

Most increases in catches in the impacted site were 

observed downstream of the HREP; however, 1 

upstream RM showed a significant increase in 

catch.

Regional Scale (~10 RM) Habitat Rehabilitation 

and Enhancement Project Effects

With the high variability of sample sizes 

in the local-scale analysis, we combined data 

from approximately 10 individual river miles 

creating eight regional areas. Results from day 

electrofishing at this scale revealed six regional 

areas where mean catches were higher in the 

post-HREP period (Figure 6). Regional area (RM 

119 to 128) demonstrated the most variation in 

catch between periods. Mean electrofishing catches 

ranged from 57.2 fish per run during the pre-HREP 

period to 524.1 in the post-HREP period. Mini-fyke 

net mean catches showed similar increases in the 

post-HREP period (Figure 7). Regional area (RM 

119 to 128), which showed the most variation in 

day electrofishing, also revealed increases in the 

mini-fyke mean catches.

Day electrofishing mean catches from selected 

backwaters in the pre- and post-HREP periods 

were highly variable among the two periods with 

over half of the backwater lakes demonstrating 

decreases in catches between periods (Figure 8). 

Figure 5. Ratio of pre- to post-Habitat Rehabilitation and Enhancement Project mini-fyke net mean catch per net by Illinois River mile and the 

control and impacted river miles used in the Before-After Control-Impact design.

River miles

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River Miles
9

Figure 6. Ratio of pre- to post-Habitat Rehabilitation and Enhancement Project day electrofishing mean catch per run by the La Grange Pool 

regional area (~10 River Miles). Lake Chautauqua is at River Mile 124.

Figure 7. Ratio of pre- to post-Habitat Rehabilitation and Enhancement Project mini-fyke net mean catch per net by the La Grange Pool regional 

area (~10 River Miles). Lake Chautauqua is at River Mile 124.

0.01

0.1

1

10

100

1000

Regional areas in River Miles

log pre:post HREP mean catch per run

81-89 90-99 100-112 113-118 119-128 129-136 137-148 149-157

0.01

0.1

1

10

100

1000

Regional areas in River Miles

log pre:post HREP mean catch per run

81-89 90-99 100-112 113-118 119-128 129-136 137-148 149-157

0.01

0.1

1

10

100

1000

Regional areas in River Miles

log pre:post HREP mean catch per net

81-89 90-99 100-112 113-118 119-128 129-136 137-148 149-157

0.01

0.1

1

10

100

1000

Regional areas in River Miles

log pre:post HREP mean catch per net

81-89 90-99 100-112 113-118 119-128 129-136 137-148 149-157
10

Figure 8. Ratio of pre- to post-Habitat Rehabilitation and Enhancement Project day electrofishing mean catch per run in backwaters of La 

Grange Pool. Numbers in parentheses correspond with Figure 1 map.

Figure 9. Ratio of pre- to post-Habitat Rehabilitation and Enhancement Project mini-fyke net mean catch per net in backwaters of La Grange 

Pool. Numbers in parentheses correspond with Figure 1 map.

0.01

0.1

1

10

100

(1) Big Lake

(2) Duck Island

(3) Clear Lake

(4) Meyers Lake

(5) Quiver Lake

(6) Matanzas Lake

(7) Crane Lake

(8) Chain Lake

(9) Bach Slough

(10) Snicarte Slough

(11)Treadway Lake

(12) Wood Slough

(13) Muscooten Bay

(14) Lilly Lake

Backwater Lakes

log pre:post HREP mean catch per run

0.01

0.1

1

10

100

(1) Big Lake

(2) Duck Island

(3) Clear Lake

(4) Meyers Ditch

(5) Quiver Lake

(6) Matanzas Lake

(7) Crane Lake

(8) Chain Lake

(9) Bach Slough

(10) Snicarte Slough

(11)Treadway Lake

(12) Wood Slough

(13) Muscooten Bay

(14) Lilly Lake

Backwater Lakes

log pre:post HREP mean catch per run

0.01

0.1

1

10

100

Backwater Lakes

log pre:post HREP mean catch per net

(1) Big Lake

(2) Duck Island

(3) Clear Lake

(4) Meyers Ditch

(5) Quiver Lake

(6) Matanzas Lake

(7) Crane Lake

(8) Chain Lake

(9) Bach Slough

(10) Snicarte Slough

(11) Treadway Lake

(12) Wood Slough

(13) Muscooten Bay

(14) Lilly Lake
11

Quiver Lake, a neighboring backwater to the 

HREP, revealed a decrease in mean catch for 

day electrofishing for the post-HREP period in 

contrast to the highest catches observed in Lake 

Chautauqua. Mini-fyke net catches illustrated the 

reverse relation with 57% of the lakes mean catches 

increasing in the post-HREP period (Figure 9). 

Quiver Lake mini-fyke net mean catches exhibited 

increases in the post-HREP period.

Pool Scale Habitat Rehabilitation and 

Enhancement Project Effects

Day electrofishing and mini-fyke net mean 

catches did not vary significantly among years 

and pool wide (Figure 10). The years 1997 and 

2002 showed the highest catches for each of the 

gears. Overall, NMDS plots provided a visual 

representation for the pre- and post-HREP 

periods, revealing no distinct separation for day 

electrofishing (Figure 11) and mini-fyke net 

(Figure 12) LTRMP abundance data. Stress values 

were high indicating a less than desirable model.

Habitat Rehabilitation and Enhancement 

Project Fish Escapement

Previous studies have estimated the abundance 

of young-of-year, juvenile, and adult fish escaping 

from the south pool of the Lake Chautauqua HREP 

into the Illinois River (Irons et al. 1997; Stoekel 

et al. 1999a,b; Lemke and Pegg 2001). These 

studies took place post-HREP completion; baseline 

escapement data were not collected prior to HREP 

construction. Years in which fish escapement 

sampling was conducted and calculated were 

1996, 1997, and 2000. Escapement estimates were 

variable among years sampled ranging from 46 

million fish in 1996 to 180 million fish in 2000 

(Figure 13). Numerically dominant fish families 

caught during sampling were the Clupeidae and 

Cyprinidae, typically comprising about 90% of the 

total catch (Figure 14). A total of 35 species were 

caught from Lake Chautauqua during the years 

sampled.

Discussion

Fish data collected by the LTRMP have 

been critical for detecting variation in annual 

abundances and community structure in La 

Grange Pool. In addition, HREP monitoring has 

demonstrated the ability to estimate the relative 

abundances and release of fish into the Illinois 

River. While our analyses did not detect the Lake 

Chautauqua HREPs influence on the Illinois River 

fish community at the pool-wide scale, our results 

did detect some differences at the local scale of 

individual river miles within the impacted area. 

Still, abnormally high sampling events, such as 

those observed at RM 123 using day electrofishing 

(mean two of five samples = 16,969 fish) and at 

RM 135 using mini-fyke netting (mean one of 

five samples = 34,242 fish), may indicate that the 

spatial and temporal sampling frequencies of the 

LTRMP may be insufficient to detect the effects of 

individual HREPs.

Previous studies have noted that LTRMP fish 

sampling can detect differences in fish community 

structure and composition among habitat strata, 

but it may not be sufficient to reveal local 

contributions such as those from individual HREPs 

(Chick et al. 2005). Although an increase in fish 

relative abundance from the Lake Chautauqua 

HREP could not be accounted for at the pool 

scale, our results indicated that (1) the Lake 

Chautauqua HREP produced millions of fish for 

the Illinois River following construction and (2) 

connected backwaters may be local hotspots for 

fish production in the Illinois River. Therefore, 

connected backwaters may be critical to sustaining 

fish populations in the river. Because mini-fyke 

net catches (proxy for young-of-year production) 

were consistently high in many backwater areas 

of La Grange Pool, our results may indicate 

that any efforts to improve backwater habitats, 

through HREPs or other methods, may bolster fish 

production to the main stem of the Illinois River. 

Our study indicates some possible explanations 

as to why the effect of the HREP could not be 

observed at the pool scale using LTRMP data.

La Grange Pool is the longest (80 RMs) and 

most habitat diverse regional trend area the LTRMP 

monitors on the UMRS; therefore, the number 

of sites sampled may be insufficient to observe 

effects. For example, only one to three samples 
12

Figure 10. Day electrofishing and mini-fyke net mean catches in La Grange Pool from 1993 to 2005. *Only the late summer and fall were 

sampled due to budget constraints (day electrofishing mean catch = 23,090.011 - 11.441*River Mile, n = 13; df = 1,11; f = 1.02; P = 0.334; 

r

2 = 0.002 and mini-fyke net mean catch = 121,569.964 - 61.178*River Mile, n = 13; df = 1,11; f = 0.578; P = 0.463; r2 = 0). (HREP, Habitat 

Rehabilitation and Enhancement Project)

Day Electrofishing

0

100

200

300

400

500

600

700

1993199419951996199719981999200020012002200320042005

Year

Mean catch per run

Mini Fyke Net

0

500

1000

1500

2000

2500

3000

3500

4000

4500

1993199419951996199719981999200020012002200320042005

Year

Mean catch per net

Day Electrofishing

1993199419951996199719981999200020012002200320042005

Year

Mini Fyke Net

1993199419951996199719981999200020012002200320042005

Year

*

*

Pre-HREP Post-HREP 

* only 2 periods sampled

Pre-HREP Post-HREP 

were taken annually per river mile. Insufficient 

sample sizes may have limited our statistical power 

to detect effects of the HREP.

Potential additional reasons for our lack of 

detection of the HREP influence may be attributed 

to the dilution effects of alternative backwaters. 

La Grange Pool has several backwater areas 
13

Figure 11. Non-metric multidimensional-scaling ordination of abundance data from day electrofishing (data were square-root 

transformed and ecological similarity was measured using the Bray-Curtis Similarity metric [Bray and Curtis 1957]). Each point 

represents fish-species abundances for a given year during the pre- or post-Habitat Rehabilitation and Enhancement Project period.

Figure 12. Non-metric multidimensional-scaling ordination of abundance data from mini-fyke nets (data were square-root 

transformed and ecological similarity was measured using the Bray-Curtis Similarity metric [Bray and Curtis 1957]). Each point 

represents fish-species abundances for a given year during the pre- or post-Habitat Rehabilitation and Enhancement Project period.

Post -HREP

Pre -HREP

Stress: 0.23

Post -HREP

Pre -HREP

Stress: 0.23

Stress: 0.24

Post -HREP

Pre -HREP

Stress: 0.24

Post -HREP

Pre -HREP
14

Figure 13. Estimates (fish in millions) from Lake Chautauqua escapement sampling.

Figure 14. Percent fish-species composition caught during Lake Chautauqua escapement sampling in 1996, 1997, and 2000. Less-abundant 

species and the percentage of total catch listed below respective charts.

0

20

40

60

80

100

120

140

160

180

200

1996 1997 1998 1999 2000 2001 2002 2003 2004 2005

Years

Fish in Millions

Skipjack Herring 2%

Freshwater Drum 2%

White Bass 1%

Other 1%

River Shiner 6%

Skipjack Herring 1%

Other 1%

Grass Carp 5%

Bighead Carp 3%

Other 2%

1996 1997 2000

Emerald Shiner

8%

Gizzard Shad

48%

Freshwater Drum

17%

Common Carp

16%

Gizzard Shad

53%

Emerald Shiner

41%

Emerald Shiner

16%

Gizzard Shad 76%

throughout its entirety. Although all are highly 

degraded, they are functional and capable of 

producing millions of fish that recruit to the 

river. For example, the 20 RM area adjacent to 

Lake Chautauqua encompasses five connected 

backwaters that may be diluting the effect of the 

HREP. Influences of these backwaters and localhabitat complexity may have constrained our 

ability to determine if the Lake Chautauqua HREP 

catches contributed above the range of normal 

variability observed in the LTRMP sampling.

Although the HREP has been in place for 

10 years, we may have lacked a data set that is 
15

temporally sufficient to yield determinations of the 

HREP influence. With the absence of pre-HREP 

escapement data, we cannot determine the effect 

of the HREP on the Illinois River. In general, all 

system manipulations or rehabilitation efforts 

should be preceded by baseline sampling of preHREP ecosystem conditions.

A parsimonious explanation for our findings 

may be that Lake Chautauqua is not contributing 

any surplus fish production to the Illinois River fish 

community compared to other regional backwaters. 

Perhaps, the fish being evacuated from the HREP 

are subjected to high exploitation and mortality 

rates immediately after their escape to the river. 

Despite main-stem river conditions influencing 

overall recruitment, Lake Chautauqua does produce 

millions of fish annually, and HREP efforts to 

improve backwater fish habitat appear to increase 

fish-production capacities.

Management Implications

Our results indicate that the Lake Chautauqua 

HREP has improved the fish-producing habitat 

of La Grange Pool. Prior to the project, the lake 

was shallow, turbid, and lacked any moist-soil 

production. After HREP construction, Lake 

Chautauqua’s south cell is now allowed to mimic 

the hydrologic regime of the Illinois River, which 

permits a spring flood and a summer drawdown 

period. The HREP is producing fish and moistsoil plants, which indicates it is providing a dual 

purpose for the Illinois River ecosystem. A major 

challenge in assessing the efficacy and effects 

of these restoration techniques is centered on 

determining how biotic communities respond to the 

physical changes (Pegg et. al. 2005). Therefore, it 

is critical to establish a scientifically rigorous and 

explicit monitoring design to ensure future HREP 

contributions can be measured not only within the 

project area, but also beyond the project boundaries 

and pool wide.

Acknowledgments

This study was supported by the U.S. Army 

Corps of Engineers Environmental Management 

Program in conjunction with the Illinois Natural 

History Survey and the U.S. Geological Survey 

Upper Midwest Environmental Sciences Center.

References

Bray, J. R., and J. T. Curtis. 1957. An ordination 

of the upland forest communities of southern 

Wisconsin. Ecological Monographs 27:325-

349.

Chick, J. H., B. S. Ickes, M. A. Pegg, V. A. 

Barko, R. A. Hrabik, and D. P. Herzog. 2005. 

Spatial structure and temporal variation of 

fish communities in the Upper Mississippi 

River System. U.S. Geological Survey, Upper 

Midwest Environmental Sciences Center, 

La Crosse, Wisconsin, May 2005. LTRMP 

Technical Report 2005-T004. 15 pp.

Environmental Systems Research Institute, 

Inc. 2002. ArcView GIS © Version 3.3. 

Environmental Systems Research Institute, Inc. 

Copyright © 1995-2005 ESRI.

Gutreuter, S. 1993. A statistical review of sampling 

fishes in the Long Term Resource Monitoring 

Program. National Biological Survey, 

Environmental Management Technical Center, 

Onalaska, Wisconsin, December 1993. EMTC 

93–T004. 15 pp. (NTIS #PB94-150828).

Gutreuter, S., R. Burkhardt, and K. Lubinski. 

1995. Long Term Resource Monitoring 

Program procedures: Fish monitoring. 

National Biological Service, Environmental 

Management Technical Center, Onalaska, 

Wisconsin. LTRMP 95-P002-1. 42 pp. + 

Appendixes A-J.

Ickes, B. S., and R. W. Burkhardt. 2002. Evaluation 

and proposed refinement of the sampling 

design for the Long Term Resource Monitoring 

Program’s fish component. U.S. Geological 

Survey, Upper Midwest Environmental 

Sciences Center, La Crosse, Wisconsin, 

October 2002. LTRMP Technical Report 2002-

T001. 17 pp. + Appendixes A-E. CD-ROM 

included. NTIS # PB2003-500042.

Irons, K. S., P. T. Raibley, K. D. Blodgett, and 

R. E. Sparks. 1997. Progress report: Lake 

Chautauqua Fish Production Study, 1996. 

Illinois Natural History Survey, Center of 

Aquatic Ecology, Champaign, Illinois, October 
16

1997. Illinois Natural History Survey Technical 

Report 97/13. 59 pp.

Junk, W. J., P. B. Bailey, and R. E. Sparks. 1989. 

The flood pulse concept in river-floodplain 

systems. Special Publication of the Canadian 

Journal of Fisheries and Aquatic Sciences 

106:110-127.

Lemke, A. M., and M. A. Pegg, editors. 

2001. Progress Report: Lake Chautauqua 

Bioresponse Study, 2000. Illinois Natural 

History Survey, Center of Aquatic Ecology, 

Champaign, Illinois, August 2001. Illinois 

Natural History Survey Technical Report 

01/09. 68 pp.

Lubinski, K. R., R. Burkhardt, J. Sauer, D. Soballe, 

and Y. Yin. 2001. Initial analyses of change 

detection capabilities and data redundancies 

in the Long Term Resource Monitoring 

Program. U.S. Geological Survey, Upper 

Midwest Environmental Sciences Center, La 

Crosse, Wisconsin, September 2001. LTRMP 

2001-T001.23 pp. + Appendixes A-E (NTIS # 

PB2002-100123).

Pegg, M. A., K. S. Irons, T. M. O’Hara, and M. A. 

McClelland. 2005. Lake Chautauqua Habitat 

Rehabilitation and Enhancement Project 

fisheries response. Contract report submitted 

to the U.S. Army Corps of Engineers, Rock 

Island, Illinois, by the U.S. Geological Survey, 

Upper Midwest Sciences Center, La Crosse, 

Wisconsin, August 2005. 27 pp.

Starrett, W. C., and A. W. Fritz. 1965. A biological 

investigation of the fish of Lake Chautauqua, 

Illinois. Illinois Natural History Survey 

Bulletin 29.

Stewart-Oaten, A., W. W., Murdoch, and K. 

R. Parker. 1986. Environmental impact 

assessment: pseudo–replication in time? 

Ecology 67:929-940.

Stoekel, J. A., K. S. Irons, K. C. Boggs, and 

B. Cross. 1999a. Progress Report: Lake 

Chautauqua Fish Production Study, 1998. 

Illinois Natural History Survey, Center 

of Aquatic Ecology, Champaign, Illinois, 

December 1999. Illinois Natural History 

Survey Technical Report 99/17. 41 pp.

Stoekel, J. A., K. S. Irons, and T. E. Snider. 

1999b. Progress Report: Lake Chautauqua 

Fish Production Study, 1997. Illinois Natural 

History Survey, Center of Aquatic Ecology, 

Champaign, Illinois, February 1999. U.S. 

Army Corps of Engineers Technical Report. 41 

pp.

U.S. Fish and Wildlife Service. 1993. Operating 

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Onalaska, Wisconsin, Revised September 

1993. EMTC 91-P002R. 179 pp. (NTIS 

#PB94-160199)
REPORT DOCUMENTATION PAGE Form Approved

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March 2008

3. REPORT TYPE AND DATES COVERED

4. TITLE AND SUBTITLE Effect of a Recently Completed Habitat Rehabilitation and Enhancement 

Project on Fish Abundances in La Grange Pool of the Illinois River using Long Term Resource 

Monitoring Program Data

5. FUNDING NUMBERS

6. AUTHOR(S) 

Timothy M. O’Hara, Michael A. McClelland, Kevin S. Irons, Thad R. Cook, and Greg G. Sass

7. PERFORMING ORGANIZATION NAME AND ADDRESS

Illinois Natural History Survey, Illinois River Biological Station, 704 North Schrader, Havana, Illinois, 62644

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 U.S. Geological Survey 

 Upper Midwest Environmental Sciences Center

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 La Crosse, Wisconsin, 54603

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12b. DISTRIBUTION CODE

13. ABSTRACT The Long Term Resource Monitoring Program (LTRMP) fish component monitors fish communities to test for changes in abundances and species 

composition in six regional trend areas of the Upper Mississippi River System. Using these data, we evaluated the ability of the LTRMP to detect changes in the 

fish community as a consequence of a habitat-enhancement project in La Grange Pool of the Illinois River. In 1996, initial phases of the Chautauqua National 

Wildlife Refuge Habitat Rehabilitation and Enhancement Project (HREP) south cell construction were completed with the goal of improving fish habitat in the 

pool. That year, an estimated 46 million fish representing 34 species were produced and discharged from the south cell of Lake Chautauqua. Whereas this response 

may indicate that the south cell serves as a spawning and nursery area for many fish species, no studies have tested for recruitment to the river fish community. We 

used geographic information system coverage at three spatial scales in the main-channel and side-channel strata to illustrate potential fish-community responses. 

At these spatial scales (local 1 river mile [RM], regional ~10 RMs, and pool wide 80 RMs), we assessed fish catch-per-unit-effort (CPUE) data collected from 

mini-fyke net and day electrofishing among pre- (1993–1995) and post-HREP (1996–2005) periods of the Chautauqua National Wildlife Refuge HREP. Analysis 

of Similarity results demonstrated no significant differences among periods in fish CPUE (P > 0.05). Our results may indicate that (1) the LTRMP sampling design 

lacked sufficient statistical power to detect effects of the HREP, (2) the LTRMP sampling design lacked the spatial and temporal resolution to detect effects, (3) the 

Lake Chautauqua HREP has not been established long enough to detect long-term trends in fish production, or (4) the HREP had no effect on fish recruitment to the 

Illinois River. Nevertheless, our results clearly show that backwaters are major fish producing areas in La Grange Pool and future HREPs to enhance backwater fish 

habitat may be critical to the long-term sustainability of the Illinois River fish community. As a result of our findings, we suggest that an intensive study at defined 

temporal and spatial scales may be required to detect changes in the fish community in La Grange Pool as a consequence of HREPs.

14. SUBJECT TERMS

Fish communities, Habitat Rehabilitation and Enhancement Project, Illinois River, Lake Chautauqua, Long Term 

Resource Monitoring Program

15. NUMBER OF PAGES

 16 pages

16. PRICE CODE

17. SECURITY CLASSIFICATION

 OF REPORT

Unclassified

18. SECURITY CLASSIFICATION

 OF THIS PAGE

Unclassified

19. SECURITY CLASSIFICATION

 OF ABSTRACT

Unclassified

20. LIMITATION OF ABSTRACT


The Long Term Resource Monitoring Program (LTRMP) for the Upper Mississippi

River System was authorized under the Water Resources Development Act of 1986 as 

an element of the Environmental Management Program. The mission of the LTRMP

is to provide river managers with information for maintaining the Upper Mississippi 

River System as a sustainable large river ecosystem given its multiple-use character.

The LTRMP is a cooperative effort by the U.S. Geological Survey, the U.S. Army Corps

of Engineers, and the States of Illinois, Iowa, Minnesota, Missouri, and Wisconsin.

2008-T001 Effect of a Recently Completed Habitat Rehabilitation and Enhancement Project on Fish Abundances in La Grange Pool of the Illinois River using 

Long Term Resource Monitoring Program Data