Long Term Resource Monitoring Program

 Technical Report 

2006-T002

July 2006

Temporal and Spatial Trends in the Frequency 

of Occurrence, Length-frequency Distributions, 

Length-weight Relationships, and Relative Abundance 

of Upper Mississippi River Fish
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: Shovelnose sturgeon (Scaphirhynchus platorynchus) by Kevin Mauel, Wisconsin Department of Natural Resouces

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.
Temporal and Spatial Trends in the Frequency of Occurrence, 

Length‐frequency Distributions, Length‐weight Relationships, and 

Relative Abundance of Upper Mississippi River Fish

by

Daniel J. Kirby

Iowa Department of Natural Resources

206 Rose Street

Bellevue, Iowa 52031

and

Brian S. Ickes

U.S. Geological Survey

Upper Midwest Environmental Sciences Center

2630 Fanta Reed Road

La Crosse, Wisconsin 54603

July 2006

U.S. Geological Survey

Upper Midwest Environmental Sciences Center

2630 Fanta Reed Road

La Crosse, Wisconsin 54603
Suggested citation:

Kirby, D. J. and B. S. Ickes. 2006. Temporal and Spatial Trends in the Frequency of Occurrence, Length‐frequency 

Distributions, Length‐weight Relationships, and Relative Abundance of Upper Mississippi River Fish. U.S. Geological 

Survey, Upper Midwest Environmental Sciences Center, La Crosse, Wisconsin. July 2006. LTRMP 2006-T002 68 pp. 

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

Springfield, VA 22161 (1-800-553-6847 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 (1-800-225-3842 or 

703‐767-9050).
iii

Executive Summary

This report focuses on fisheries information colleted by the Long Term Resource 

Monitoring Program (LTRMP) in 1993–2002. In 10 years of sampling, more than 24,000 fish 

community samples from six study areas in the Upper Mississippi River System (UMRS) 

were collected for the LTRMP. More than three million individual fish composing 136 species 

were collected. Data gathered from this extensive effort were used to address the following 

four questions: (1) What fish species are present in the UMRS and how are species distributed 

within the basin? (2) What is the size structure of commercially and recreationally important 

species and does size structure vary within the system? (3) How does the physical condition 

of species vary from year to year and spatially within the system? and (4) In what way does 

the abundance of species within the system vary temporally and spatially? These topics were 

chosen because they take advantage of the extensive temporal and spatial characteristics of 

the LTRMP fisheries database and address important management-oriented questions not 

easily answered with short-term or local-scale research. Most of the findings in the report are 

not revolutionary, but rather provide quantified proof or support for existing ideas regarding 

population ecology within the UMRS. The following is a summary of key findings:

1. From 1993 to 2002, the LTRMP collected 136 of the 163 species (83%) found in the 

UMR since the late 19th century. 

a. Of these 136 species, 47 species were collected in all six LTRMP study areas, 

32 species were collected in 4 or 5 study areas, 33 species were collected in 2 or 

3 study areas, and 24 species were collected in 1 study area.

b. Fifty-six species always occurred or frequently occurred within sampling years 

(1993–2002), 47 species commonly occurred or occasionally occurred within 

sampling years, and 33 species uncommonly occurred or rarely occurred within 

sampling years.

c. Cyprinidae was the dominant family in terms of species richness and composed 

30% of the species collected from the UMRS. Five families (Catostomidae, 

Centrarchidae, Cyprinidae, Ictaluridae, and Percidae) composed 72% of the 

species collected from the UMRS. 

2. Spatial differences in length-frequency distributions were more pronounced 

for commercially exploited species (e.g., channel catfish [Ictalurus punctatus] 

and smallmouth buffalo [Ictiobus bubalus]) than for species exploited solely by 

recreational angling (e.g., black crappie [Pomoxis nigromaculatus] and sauger 

[Sander canadensis]).

a. In Pool 4, all 12 species investigated exhibited a relative length frequency 

composed of a high proportion of long fish when compared to average length 

frequencies for LTRMP study areas.

3. Rate of gain (i.e., increase in log10 weight per unit increase in log10 length) was 

significantly different among LTRMP study areas for all five of the species 

investigated (i.e., black crappie, channel catfish, common carp [Cyprinus carpio], 

sauger, and walleye [Sander vitreus]) and was significantly different among years 

for four of the five species (i.e., black crappie, channel catfish, common carp, and 

walleye).

a. La Grange Pool of the Illinois River was the only study area that contained 

species (black crappie, channel catfish, and sauger) exhibiting a rate of gain 

significantly greater than the overall UMRS rate of gain trend.
iv

4. The relative abundance of 75 study groups (50 fish species, 25 of which were split 

into 2 length groups) varied significantly among LTRMP study areas, 72 of 75 study 

groups exhibited significant variation in relative abundance among 3 types of aquatic 

areas (contiguous backwater shorelines, main channel border, and side channel 

border), and 59 of 75 study groups exhibited significant interannual variation in 

relative abundance.

a. Spatial variation proved more important than temporal variation for separating 

species based upon relative abundance patterns.

b. Centrarchid species exhibited high levels of variation in relative abundance 

among contiguous backwater shoreline, main channel border, and side channel 

border areas.

c. For substock-length fish, temporal variation in relative abundance was, in 

general, most pronounced for species in channel habitats that exhibit low parental 

care (e.g., common carp, sauger, smallmouth buffalo, walleye, and white bass 

[Morone chrysops]) and was least pronounced for species exhibiting high 

parental care (e.g., bluegill [Lepomis macrochirus], channel catfish, flathead 

catfish [Pylodictis olivaris], green sunfish [Lepomis cyanellus], longnose gar 

[Lepisosteus osseus], and white crappie [Pomoxis annularis]).

d. Analysis of variance suggests that centrarchid species, bowfin (Amia calva), 

emerald shiners (Notropis atherinoides), flathead catfish, golden shiners 

(Notemigonus crysoleucas), longnose gar, river shiners (Notropis blennius), 

and yellow perch (Perca flavescens) are most likely to respond to habitat 

rehabilitation and enhancement projects applied to macrohabitats.
Contents

Page

Executive Summary ..................................................................................................................iii

Tables........................................................................................................................................vi

Figures......................................................................................................................................vii

Preface.......................................................................................................................................ix

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

Chapter 1. Introduction, Study Area, and Fish Sampling Methods

Introduction ......................................................................................................................... 2

Study Area........................................................................................................................... 3

Fish Sampling Methods....................................................................................................... 3

Chapter 2. Species Distribution and Frequency Of Occurrence

Introduction ......................................................................................................................... 6

Methods............................................................................................................................... 6

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

Discussion .......................................................................................................................... 7

Chapter 3. Spatial Patterns In Length-frequency Distributions

Introduction ....................................................................................................................... 16

Methods............................................................................................................................. 16

Results .............................................................................................................................. 17

Discussion ........................................................................................................................ 18

Chapter 4. Temporal and Spatial Trends In Length-weight Relationships

Introduction ....................................................................................................................... 46

Methods............................................................................................................................. 46

Results .............................................................................................................................. 47

Discussion ........................................................................................................................ 47

Chapter 5. Temporal and Spatial Trends In Relative Abundance

Introduction ....................................................................................................................... 52

Methods............................................................................................................................. 52

Results .............................................................................................................................. 54

Discussion ........................................................................................................................ 59

Acknowledgements.................................................................................................................. 66

References................................................................................................................................ 66
vi

Tables

Number Page

1.1. Floodplain and aquatic area compositions of the Long Term Resource Monitoring 

Program (LTRMP) study areas in the Mississippi River (Pools 4, 8, 13, and 26, and 

Open River) and Illinois River (La Grange Pool) ............................................................... 4

1.2. Number of fish collections made by year, study area, and gear in the Long Term 

Resource Monitoring Program study areas in the Upper Mississippi River System in 

1993–2002........................................................................................................................... 5

2.1. Total years of occurrence (i.e., the number of sampling years where at least one 

specimen of a species was caught), by study area, for fish species collected by the 

Long Term Resource Monitoring Program as part of standard monitoring in the Upper 

Mississippi River System in 1993–2002. ........................................................................... 9

2.2. Species counts within distribution and frequency of occurrence categories for fish 

species collected by the Long Term Resource Monitoring Program in the Upper 

Mississippi River System during 1993–2002.................................................................... 14

2.3. Total species richness by study area and family, for fishes collected by the Long Term 

Resource Monitoring Program in the Upper Mississippi River System in 1993–2002. .. 15

3.1. Kolmogorov-Smirnov (KS) statistics for differences in length-frequency distributions 

of stock-length fish among study areas of the Long Term Resource Monitoring Program 

(LTRMP) in 1993–2002. ................................................................................................... 32

3.2. Areawide mean catch-per–unit-effort (fish/15 min) and standard error estimates by 

length group for bigmouth buffalo (Ictiobus cyprinellus) collected by day electrofishing 

in Long Term Resource Monitoring Program study areas in 1993–2002. ........................ 34

3.3. Areawide mean catch per unit effort (fish/net day) and standard error estimates by length 

group for black crappie (Pomoxis nigromaculatus) collected by fyke nets in Long Term 

Resource Monitoring Program study areas in 1993–2002. ............................................... 35

3.4. Areawide mean catch per unit effort (fish/15 min) and standard error estimates by length 

group for bluegill (Lepomis macrochirus) collected by day electrofishing in Long Term 

Resource Monitoring Program study areas in 1993–2002. ............................................... 36

3.5. Areawide mean catch-per-unit-effort (fish/net day) and standard error estimates by 

length group for channel catfish (Ictalurus punctatus) collected by small hoop nets in 

Long Term Resource Monitoring Program study areas in 1993–2002. ............................ 37

3.6. Areawide mean catch-per-unit-effort (fish/15 min) and standard error estimates by 

length group for common carp (Cyprinus carpio) collected by day electrofishing in Long 

Term Resource Monitoring Program study areas in 1993–2002....................................... 38

3.7. Areawide mean catch-per–unit-effort (fish/net day) and standard error estimates by 

length group for flathead catfish (Pylodictis olivaris) collected by large hoop nets in 

Long Term Resource Monitoring Program study areas in 1993–2002. ............................ 39

3.8. Areawide mean catch-per-unit-effort (fish/15 min) and standard error estimates 

by length group for freshwater drum (Aplodinotus grunniens) collected by day 

electrofishing in Long Term Resource Monitoring study areas in 1993–2002. ................ 40

3.9. Areawide mean catch-per-unit-effort (fish/15 min) and standard error estimates 

by length group for largemouth bass (Micropterus salmoides) collected by day 

electrofishing in Long Term Resource Monitoring Program study areas in 1993–2002. . 41
vii

3.10. Areawide mean catch-per-unit-effort (fish/15 min) and standard error estimates by 

length group for sauger (Sander canadensis) collected by day electrofishing in Long 

Term Resource Monitoring Program study areas in 1993–2002....................................... 42

3.11. Areawide mean catch-per-unit-effort (fish/net day) and standard error estimates by 

length group for smallmouth buffalo (Ictiobus bubalus) collected by large hoop nets 

in Long Term Resource Monitoring Program study areas in 1993–2002 ......................... 43

3.12. Areawide mean catch-per-unit-effort (fish/15 min) and standard error estimates by 

length group for white bass (Morone chrysops) collected by day electrofishing in 

Long Term Resource Monitoring Program study areas in 1993–2002. ............................ 44

3.13. Areawide mean catch-per-unit-effort (fish/net day) and standard error estimates by 

length group for white crappie (Pomoxis annularis) collected by fyke nets in Long 

Term Resource Monitoring Program study areas in 1993–2002....................................... 45

4.1. Results of tests for parallel slopes and equal Y-intercepts for length-weight 

regressions of fish collected from September 16–October 31 in 1993–2002 from 

the six Long Term Resource Monitoring Program study areas within the Upper 

Mississippi River System. ................................................................................................. 48

4.2. Length-weight regression statistics by study area for fish collected from the Upper 

Mississippi River System by the Long Term Resource Program in 1993–2002............... 49

4.3. Length-weight regression statistics by year for fish collected from the Upper 

Mississippi River System by the Long Term Resource Program in 1993–2002............... 50

5.1. Study group codes in alphabetical order. .......................................................................... 63

5.2. Eigenanalysis results for substock-length study groups principal components analysis . 65

5.3. Eigenanalysis results for stock-length study groups principal components analysis. ...... 65

5.4. Eigenanalysis results for study groups without size designations principal 

components analysis.......................................................................................................... 65

Figures

Number Page

1.1 The Upper Mississippi River System and the six study areas that comprise the Long 

Term Resource Monitoring Program. ................................................................................. 3

3.1. Relative length-frequency distributions of bigmouth buffalo (Ictiobus cyprinellus) 

collected by day electrofishing in the Long Term Resource Monitoring Program 

study areas in 1993–2002.................................................................................................. 20

3.2. Relative length-frequency distributions of black crappie (Pomoxis nigromaculatus) 

collected by fyke nets in the Long Term Resource Monitoring Program study areas 

in 1993–2002..................................................................................................................... 21

3.3. Relative length-frequency distributions of bluegill (Lepomis macrochirus) collected 

by day electrofishing in the Long Term Resource Monitoring Program study areas in 

1993–2002......................................................................................................................... 22

3.4. Relative length-frequency distributions of channel catfish (Ictalurus punctatus) 

collected by small hoop nets in the Long Term Resource Monitoring Program study 

areas in 1993–2002............................................................................................................ 23

3.5. Relative length-frequency distributions of common carp (Cyprinus carpio) collected 

by day electrofishing in the Long Term Resource Monitoring Program study areas in 

1993–2002......................................................................................................................... 24
viii

3.6. Relative length-frequency distributions of flathead catfish (Pylodictis olivaris) collected 

by large hoop nets in the Long Term Resource Monitoring Program study areas in 

1993–2002......................................................................................................................... 25

3.7. Relative length-frequency distributions of freshwater drum (Aplodinotus grunniens) 

collected by day electrofishing in the Long Term Resource Monitoring Program study 

areas in 1993–2002............................................................................................................ 26

3.8. Relative length-frequency distributions of largemouth bass (Micropterus salmoides) 

collected by day electrofishing in the Long Term Resource Monitoring Program study 

areas in 1993–2002............................................................................................................ 27

3.9. Relative length-frequency distributions of sauger (Sander canadensis) collected 

by day electrofishing in the Long Term Resource Monitoring Program study areas in 

1993–2002......................................................................................................................... 28

3.10. Relative length-frequency distributions of smallmouth buffalo (Ictiobus bubalus) 

collected by large hoop nets in the Long Term Resource Monitoring Program study 

areas in 1993–2002............................................................................................................ 29

3.11. Relative length-frequency distributions of white bass (Morone chrysops) collected 

by day electrofishing in the Long Term Resource Monitoring Program study areas 

in 1993–2002..................................................................................................................... 30

3.12. Relative length-frequency distributions of white crappie (Pomoxis annularis) 

collected by fyke nets in the Long Term Resource Monitoring Program study areas in 

1993–2002......................................................................................................................... 31

5.1. Pie charts representing the results of variance decomposition for the relative 

abundance (proportion of positive electrofishing runs) of stock-length longnose gar 

(Lepisosteus osseus) and shovelnose sturgeon (Scaphirhynchus platorynchus) collected 

by electrofishing from five study areas in the Upper Mississippi River System............... 55

5.2. Proportion of total variation in abundance explained by year and aquatic area factors 

for 75 fish study groups collected with day electrofishing from the Upper Mississippi 

River System in 1993–2002. ............................................................................................. 56

5.3. Proportion of total variation in abundance explained by study area and aquatic area 

factors for 75 fish study groups collected with day electrofishing from the Upper 

Mississippi River System in 1993–2002. .......................................................................... 57

5.4. Proportion of total variation in abundance explained by year and study area factors 

for 75 fish study groups collected with day electrofishing from the Upper Mississippi 

River System in 1993–2002. ............................................................................................. 58

5.5. Biplot showing the first two principal component axes and demonstrating the 

loadings of each species on the seven analysis of variance (ANOVA) factors for 

substock-length fish........................................................................................................... 60

5.6. Biplot showing the first two principal component axes and demonstrating the 

loadings of each species on the seven analysis of variance (ANOVA) factors for 

stock‐length fish. ............................................................................................................... 60

5.7. Biplot showing the first two principal component axes and demonstrating the loadings 

of each species on the seven analysis of variance (ANOVA) factors for fish species 

without length designations............................................................................................... 61
ix

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 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 as 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 supports Strategy 2.2.8 as specified in Goal 2, Monitor Resource Change, of 

the LTRMP Operating Plan (U.S. Fish and Wildlife Service 1993). This report was developed 

with funding provided by the LTRMP.

Temporal and Spatial Trends in the Frequency of Occurrence, LengthFrequency Distributions, Length-Weight Relations, and Relative 

Abundance of Upper Mississippi River Fish

Daniel J. Kirby1 and Brian S. Ickes2

1

Iowa Department of Natural Resources

206 Rose Street

Bellevue, Iowa 52031

2

U.S. Geological Survey

Upper Midwest Environmental Sciences Center

2630 Fanta Reed Road

La Crosse, Wisconsin 54603

Abstract: The Long Term Resource Monitoring Program (LTRMP) collected more than 

24,000 fish community samples from six study areas on the Upper Mississippi River System 

in 1993–2002. More than three million fish composed of 136 fish species were collected. 

These data were used to assess length‐weight relationships and size structure of commercial 

(i.e., commercially harvested) and recreational (i.e., recreationally harvested) species, and 

the distribution, frequency of occurrence, and abundance patterns of commercial, nongame 

(i.e., not commercially or recreationally harvested), and recreational species. Forty‐seven 

species were collected in all 6 LTRMP study areas, 32 species were collected in 4 or 5 study 

areas, 33 species were collected in 2 or 3 study areas, and 24 species were collected in 

1 study area. Spatial differences (i.e., differences among study areas) in size structure were 

more pronounced for commercial species than for recreational species. Rate of gain (increase 

in log10 weight per unit increase in log10 length) was assessed for five species, and was 

significantly different among study areas for all five species and significantly different among 

years for four species. Assessment of longitudinal‐spatial (among study area), lateral‐spatial 

(among aquatic area types) and temporal (among 10 years) patterns in abundance showed 

that species were most similar with respect to temporal variation in abundance, and least 

similar with respect to longitudinal‐spatial variation in abundance. These fisheries population 

assessments, derived from the spatially and temporally expansive LTRMP dataset, will 

provide river resource managers with decision support tools for managing UMRS fisheries.

Key words: Abundance patterns, fish populations, Illinois River, length‐weight relationships, 

size structure, species richness, Upper Mississippi River.


Chapter 1. Introduction, Study Area, 

and Fish Sampling Methods

Introduction

The Upper Mississippi River (UMR) is an 

important aquatic resource supporting a variety 

of uses including recreational and commercial 

fishing (Rasmussen 1979; U.S. Geological 

Survey 1999). In a 1990 recreational‐use survey, 

fishing accounted for 29% of reported activity 

on the UMR and recreational users (e.g., anglers, 

boaters, sightseers) spent approximately 

$340 million on durable goods and trip‐related 

expenses (Carlson et al. 1995). The UMR 

commercial fishery harvest averages about 

11 million pounds annually with a wholesale 

value of about $2 million dollars (Upper 

Mississippi River Conservation Committee 

1998, 1999, 2000). The UMR supports a rich 

fish assemblage, with more than 150 species 

reported in collections from the UMR during the 

past century (Pitlo et al. 1995). The ecological, 

social, and economic importance of UMR fishes 

provides support for monitoring UMR fish 

population trends. 

The Water Resource Development Act of 

1986 (Public Law 99‐662) established the Upper 

Mississippi River System (UMRS) as the only 

river system in the United States to be formally 

recognized as a nationally significant ecosystem 

and commercial navigation system. As part of 

this recognition, the U.S. Congress authorized 

the Environmental Management Program in 

1986, which includes the Long Term Resource 

Monitoring Program (LTRMP). The LTRMP 

is implemented by the U.S. Geological Survey 

Upper Midwest Environmental Sciences Center 

in cooperation with the five Upper Mississippi 

River System states of Illinois, Iowa, Minnesota, 

Missouri, and Wisconsin. The U.S. Army 

Corp of Engineers has overall responsibility 

for the LTRMP and provides guidance to the 

program. The mode of operation and the roles 

of agencies are outlined in a 1988 Memorandum 

of Agreement. The LTRMP fisheries component 

is charged with monitoring and reporting trends 

of selected fish populations and communities 

in the UMRS (U.S. Fish and Wildlife Service 

1993). In 1993–2002, the LTRMP collected fish 

community samples at sites in five UMR study 

areas (Pools 4, 8, 13, and 26, and Open River) 

and one Illinois River study area (La Grange 

Pool). Fisheries data collected as part of the 

LTRMP are used to quantify the status and 

trends of fish populations and communities, and 

to address fisheries management concerns in 

a multiuse large‐river resource (Gutreuter and 

Theiling 1999).

This report focuses on the population 

ecology of fishes in the Upper Mississippi and 

Illinois Rivers. The data analyses presented 

address several fisheries management questions. 

Chapter 2 defines the “commonness” and spatial 

distribution of the 136 fish species collected 

by the LTRMP. Chapter 3 focuses on the 

length‐frequency distribution of 12 common 

and widespread species (i.e., species collected 

from all 6 LTRMP study areas in 1993–2002) 

with importance to recreational or commercial 

fisheries. Chapter 4 investigates the length‐weight 

relationships of five species with importance to 

recreational and commercial fisheries. Chapter 5 

defines the spatial and temporal variation of 

50 widespread species (i.e., collected from all 

LTRMP study areas, excluding the Open River 

study area, in at least 1 year of sampling). The 

central theme linking these four chapters is the 

quantification of trends in population indices 

both within study areas and across the UMRS. 

The topics and theme of this report were chosen 

because they use the extensive temporal and 

spatial characteristics of the LTRMP fisheries 

database to address management questions not 

easily answered with short‐term and local‐scale 

research. 

Chapters 3 through 5 used standardized 

length categories to define size classes of fish 

before analyses. Length categories were used 

to identify size classes of populations that may 

exhibit unique temporal or spatial variation. 

Length categories were used for common 

recreational and commercial species. Incremental 

length categories (Gabelhouse 1984), provided 

by Anderson and Neumann (1996) and Bister 

et al. (2000), were used in Chapters 3 and 4. 

Incremental length categories place fish into 

substock, stock‐quality, quality‐preferred, 


preferred‐memorable, memorable‐trophy, and 

trophy length categories based on percentages of 

world record length for each species (Anderson 

and Neumann 1996). Minimum lengths for stock, 

quality, preferred, memorable, and trophy length 

categories correspond to near 20–26%, 36–41%, 

45–55%, 59–64%, and 74–80% of world record 

lengths, respectively (Anderson and Neumann 

1996). Traditional length categories (Gabelhouse 

1984) were used in Chapter 5 to place fish 

into substock (i.e., less than stock length) and 

stock length (i.e., greater than or equal to stock 

length) categories. Stock length, as defined 

above, equates roughly to the size where fish 

reach maturity and the minimum length of fish 

that provide recreational value (Anderson and 

Neumann 1996).

Study Area

The LTRMP study areas include six river 

sections within the UMRS. Five of the study 

areas are on the Mississippi River and one is 

on the Illinois River (Figure 1.1). Study areas 

are referred to by navigation pool designations 

(e.g., Pool 4 is the area between Lock and 

Dam 4 and Lock and Dam 3), or by river mile 

(river mile 0 is at the confluence of the Ohio 

and Mississippi Rivers). Mississippi River study 

areas include Pools 4 (river mile 752–797; 

excluding Lake Pepin), 8 (river mile 679–703), 

13 (river mile 523–557), and 26 (river mile 

202–242) and the Open River study area (river 

mile 29–80, hereafter referred to as Open River). 

The Illinois River study area is La Grange 

Pool (river mile 80–158). These study areas 

were chosen, in part, to reflect differences in 

geomorphology, floodplain land‐use practices, 

and navigation management practices within the 

UMRS (Burkhardt et al. 2001). Pools 4, 8, and 

13 are characterized by high percentages of open 

water and aquatic vegetation and low agricultural 

use within the floodplain (Table 1.1). Pools 4, 

8, and 13 are geomorphically complex with a 

high percentage of total aquatic area composed 

of backwater and side channels. Pool 26 and 

Open River contain a relatively high percentage 

of agricultural land use within the floodplain, 

and a comparatively high percentage of the total 

aquatic area is main channel 

(Table 1.1). The floodplain 

composition of La Grange 

Pool is similar to Pool 26 and 

Open River, but aquatic area 

composition within La Grange 

Pool is similar to Pools 4, 8, and 

13 (Burkhardt et al. 2001).

Fish Sampling Methods

Standardized LTRMP 

sampling procedures (Gutreuter 

et al. 1995) were used to 

collect community fish 

samples from LTRMP study 

areas in 1993–2002. Fisheries 

sampling was conducted using 

a stratified random sampling 

regime. The strata were based 

on enduring geomorphic 

and physical features, called 

aquatic areas, that help define 

aquatic habitats (Gutreuter 

et al. 1995). The following 

nine strata types were used: Figure 1.1. The Upper Mississippi River System and the six study areas that compose the 

Long Term Resource Monitoring Program.


backwater contiguous‐offshore, backwater 

contiguous‐shoreline, side channel borders, main 

channel border‐unstructured area, tailwater zone, 

impounded‐offshore, impounded‐shoreline, 

tributary mouth, and tributary delta lake. Within 

each study area, sampling effort was equally 

allocated in three periods: June 15–July 31, 

August 1–September 15, and September 16–

October 31. Realized effort within each year 

(i.e., the number of completed collections) 

was contingent upon river conditions and was 

reduced in 2002 when three gear types (seines, 

tandem fyke nets, tandem mini‐fyke nets) were 

eliminated from standard sampling allocations 

(Table 1.2).

The following sampling gears, in 

standardized dimensions and effort, were used to 

collect community samples: day electrofishing, 

night electrofishing, fyke nets, mini‐fyke nets, 

seines, trawls, gill nets, tandem fyke nets, and 

tandem mini‐fyke nets (Gutreuter et al. 1995; 

Table 1.2). Not all strata were represented in 

each study area and not all gears were deployed 

in each stratum. Sampling sites (50‐ x 50‐m 

cells) were randomly selected from a database 

of accessible sampling sites and referenced by 

Universal Transverse Mercator coordinates. 

Randomly selected alternate sites were also 

generated to provide collection teams with 

alternates to primary sites that were deemed 

inaccessible (e.g., too shallow). Fisheries 

sampling was augmented with limited sampling 

at a few permanently fixed sites. Fixed‐site 

samples were included in analyses for 

Chapters 2–4, but were not included in analyses 

for Chapter 5.

Collected fish were identified to species 

to the extent reasonably possible and counted. 

Individual fish were measured for total length 

to the nearest millimeter. However, when large 

catches were encountered, fish were placed 

into 1- or 2‐cm length groups. Observations 

of hybrids and fish identified only to genus 

were excluded from analysis for this report. 

Weight measurements to the nearest gram 

were recorded for subsamples of black crappie 

(Pomoxis nigromaculatus), channel catfish 

(Ictalurus punctatus), common carp (Cyprinus 

carpio), highfin carpsucker (Carpiodes velifer), 

sauger (Sander canadensis), and walleye 

(Sander vitreus) collected from September 16 to 

October 31 of each monitoring year.

Table 1.1. Floodplain and aquatic area compositions of the Long Term Resource Monitoring Program (LTRMP) study areas in the 

Mississippi (Pools 4, 8, 13, and 26 and Open River) and Illinois Rivers (La Grange Pool). 

Floodplain composition (%) a

Aquatic area composition 

(%) b

Study area

Floodplain 

area (ha)

Open 

water

Aquatic 

vegetation c Agriculture

Contiguous 

backwater

Main 

channel d

Pool 4 25,155 47.1 15.9 5.7 21.3 10.5

Pool 8 15,408 36.4 25.7 0.7 30.6 14.2

Pool 13 23,965 25.7 23.6 7.3 28.5 24.7

Pool 26 48,467 13.4 1.6 33.5 17.3 54.4

Open River 107,142 9.8 0.6 70.4 1.8 79.0

La Grange Pool 89,529 15.7 2.2 59.6 52.2 21.3 a Data on floodplain composition were from Theiling et al. (2000). Open River floodplain composition was for river 

mile 0 to 80 (Ohio River confluence to Grand Tower).

b Data on the composition of aquatic areas were from the LTRMP aquatic areas spatial database. Aquatic area 

composition was for river mile 29 to 80 (Open River).

c Aquatic vegetation included submersed aquatic beds, floating-leaved aquatic beds, permanently flooded emergent 

annuals, and permanently flooded emergent perennials.

d Main channel included navigation channel and main channel border areas.


Table 1.2. Number of fish collections made by year, study area, and gear in the Long Term Resource Monitoring Program study areas in 

the Upper Mississippi River System in 1993–2002. 

Gear a Completed 

collectionsb

Allocated 

collectionsc Year D F G HL HS M N S T TA TF TM

Pool 4

1993 71 22 30 54 55 48 12 40 8 NCd 23 24 387 390

1994 84 30 12 61 60 59 12 58 12 12 24 24 448 474

1995 82 32 12 65 66 62 12 55 12 12 24 24 458 474

1996 84 36 12 66 66 64 12 58 12 12 24 24 470 474

1997 82 36 11 48 46 65 12 70 8 12 30 30 450 462

1998 82 35 12 47 48 66 11 72 10 12 30 30 455 462

1999 84 36 12 48 48 66 12 72 12 12 30 30 462 462

2000 84 24 NC 36 36 53 12 72 12 NC 24 24 377 378

2001 80 24 NC 36 36 54 12 72 12 NC 24 24 374 378

2002 82 24 NC 36 36 54 NC NC 4 NC NC NC 236 246

Pool 8

1993 86 52 20 66 66 84 54 116 12 NC 12 12 580 580

1994 93 60 14 66 66 79 54 118 12 NC 12 12 586 592

1995 96 60 7 66 66 84 54 72 12 5 12 12 546 546

1996 96 60 NC 66 66 84 54 72 12 NC 18 18 546 546

1997 102 60 NC 66 66 84 54 72 12 NC 18 18 552 552

1998 102 60 NC 65 66 84 54 72 12 NC 18 18 551 552

1999 102 60 NC 66 66 84 54 70 12 NC 18 18 550 550

2000 72 42 NC 30 30 66 48 60 12 NC 18 12 390 390

2001 84 48 NC 41 42 66 48 60 12 NC 18 12 431 432

2002 84 48 NC 30 30 66 NC NC 12 NC NC NC 270 270

Pool 13

1993 52 39 NC 39 40 55 14 80 4 NC 18 19 360 486

1994 60 42 NC 49 49 70 22 108 16 NC 21 21 458 486

1995 59 42 NC 54 54 75 24 108 24 NC 21 21 482 486

1996 63 42 NC 54 54 75 24 108 24 NC 21 21 486 486

1997 61 42 NC 54 54 75 19 108 24 NC 21 21 479 486

1998 63 42 NC 54 54 75 24 108 24 NC 21 21 486 486

1999 63 42 NC 54 54 75 24 108 24 NC 21 21 486 486

2000 63 42 NC 54 54 75 24 108 24 NC 21 21 486 486

2001 63 42 NC 54 54 75 24 108 24 NC 21 21 486 486

2002 63 42 NC 48 48 75 NC NC 24 NC NC NC 300 300

Pool 26

1993 33 12 NC 22 22 13 NC 4 NC NC 5 5 116 387

1994 78 24 NC 53 55 47 6 84 12 NC 12 12 383 387

1995 77 24 NC 56 55 45 6 84 12 NC 12 12 383 387

1996 78 24 NC 57 57 45 6 84 12 NC 12 12 387 387

1997 77 24 NC 56 57 45 6 84 12 6 12 12 391 387

1998 76 23 NC 54 51 42 6 76 12 6 12 12 370 387

1999 76 24 NC 52 54 45 6 78 12 NC 12 12 371 387

2000 78 24 NC 56 57 43 6 84 8 6 12 12 386 387

2001 77 24 NC 56 57 43 6 84 12 NC 12 12 383 387

2002 77 25 NC 56 57 45 NC NC 12 NC NC NC 272 273

Open River

1993 14 10 1 13 13 27 NC NC 1 NC NC NC 79 336

1994 37 18 7 53 55 60 NC 24 6 NC NC NC 260 336

1995 47 16 7 51 52 57 NC 22 4 NC NC NC 256 336

1996 46 17 NC 49 49 61 NC 32 49 NC NC NC 303 336

1997 50 17 11 54 55 64 NC 44 57 NC NC NC 352 336

1998 33 12 9 50 51 58 NC 9 4 NC NC NC 226 354

1999 45 11 NC 52 55 54 NC 32 NC NC NC NC 249 318

2000 47 14 17 47 47 48 NC 63 1 NC NC NC 284 318

2001 51 15 24 51 50 51 NC 56 NC NC NC NC 298 318

2002 51 15 NC 50 50 51 NC NC NC NC NC NC 217 219

La Grange Pool

1993 66 23 53 54 54 65 42 60 10 NC 12 12 451 426

1994 66 24 NC 59 59 64 67 84 14 30 12 12 491 384

1995 127 42 NC 71 72 92 17 96 24 NC 12 12 565 564

1996 126 41 NC 69 72 90 18 94 24 NC 12 12 558 564

1997 122 42 NC 59 59 89 18 94 24 NC 18 18 543 552

1998 124 42 NC 60 60 90 16 96 24 NC 18 18 548 552

1999 123 42 NC 60 60 89 13 96 24 NC 18 18 543 552

2000 125 41 NC 60 60 88 18 92 24 NC 18 18 544 552

2001 126 42 NC 60 60 90 18 96 24 NC 18 18 552 552

2002 126 42 NC 60 60 90 NC NC 24 NC NC NC 402 402

a

Gear types are abbreviated as follows: D = day electrofishing, F = fyke nets, G = gill nets, HL = large hoop nets, 

HS = small hoop nets, M = mini-fyke nets, N = night electrofishing, S = seines, T = trawling, TA = trammel nets, 

TF = tandem fyke nets, and TM = tandem mini-fyke nets. b

Completed collections are the number of successfully completed fish collections in each study area and year.

c

Allocated collections are the number of collections that were allocated in each study area and year using the LTRMP 

study design.

d

NC = no collections made.
Chapter 2. Species Distribution and 

Frequency of Occurrence

Introduction

The Upper Mississippi River (UMR) is a 

diverse assemblage of aquatic habitats (e.g., 

secondary channels, backwaters, and main 

channel) subject to environmental conditions that 

can vary substantially over time (e.g., drought, 

flood, and ice). This spatial and temporal habitat 

diversity supports a fish community with high 

species richness (Smith et al. 1971; Rasmussen 

1979; Fremling et al. 1989, Pitlo et al. 1995). 

Rasmussen (1979), Fremling et al. (1989), and 

Pitlo et al. (1995) subjectively assessed the 

relative abundance of UMR species based upon 

collection data from field biologists, defined 

species distributions, and placed species into rare, 

uncommon, occasional, common, or abundant 

categories. As acknowledged by Pitlo et al. 

(1995), the amount and type of data available 

about individual species may depend upon the 

ease of collecting a species and the importance 

of the species to commercial and recreational 

fisheries. 

In this chapter, the “commonness” of fish 

species is assessed using the number of years 

each species was found in each study area during 

1993–2002. Species distribution and frequency 

of occurrence data provide insight into systemic 

processes that shape fish communities. Fish 

communities are a reflection of the habitat 

available and the habitat requirements of 

individual species. The presence of a species 

in a study area suggests that the species habitat 

requirements are being met and the absence 

of a species in a study area suggests that the 

species habitat requirements are not being 

met. Sometimes, habitat management and 

rehabilitation can modify available habitat to 

influence the distribution or relative abundance of 

a species.

Methods

We analyzed fish community data collected 

from the Long Term Resource Monitoring 

Program (LTRMP) in 1993–2002 from Pools 4, 

8, 13 and 26 and Open River study area (Open 

River; river mile 29–80) of the Mississippi River, 

and La Grange Pool of the Illinois River. Within 

each study area and for each study year, a species 

was considered present if it was captured with 

any gear (Table 2.1). Species were assigned 

to distribution categories and frequency of 

occurrence categories based upon the number 

of study areas the species was collected in and 

the average frequency (percentage of years) 

the species was collected within study areas of 

occurrence (Table 2.1). The scientific names 

(genus and species), common names, and 

phylogenic sequence of families that we used 

were provided by Nelson et al. (2004). 

Results

One hundred thirty-six species from 

27 families were collected for the LTRMP as 

part of standard monitoring (Table 2.1). Of 

these 136 species, 47 species were collected 

in all study areas, 32 species were collected in 

4 or 5 study areas, 33 species were collected 

in 2 or 3 study areas, and 24 species were 

collected in 1 study area (Table 2.2). Fifty‐six 

species always occurred or frequently occurred 

within sampling years (1993–2002), 47 

species commonly occurred or occasionally 

occurred within sampling years, and 33 species 

uncommonly occurred or rarely occurred within 

sampling years (Table 2.2). In general, species 

with the most widespread distributions had the 

highest frequency of occurrence, and species 

with the smallest distributions had the lowest 

frequency of occurrence (Table 2.2). Eighteen 

fish species were collected in all study areas and 

in all years, and included 2 lepisosteids (gar), 

1 amiid (bowfin), 1 clupeid (herring), 3 cyprinids 

(carp or minnows), 2 catostomids (suckers), 

2 ictalurids (catfish), 1 percichthyid (temperate 

bass), 4 centrarchids (sunfish), 1 percid (perch) 

and 1 sciaenid (drum). Fifteen species rarely 

occurred within sampling years, and included 

5 cyprinids, 1 esocid (pike), 1 osmerid (smelt), 

1 cyprinodontid (killfish), 1 centrarchid, and 

3 percids (Table 2.1). 

Species richness for 1993–2002 was 

highest in Open River (101 species), and was 

similar in Pools 8 and 26 (89 species), Pool 4 

(86 species), La Grange Pool (85 species) and 


Pool 13 (83 species). The high species richness 

in Open River was largely attributable to the 

collection of 5 cyprinids (bigeye chub, blacktail 

shiner, bleeding shiner, plains minnow, sicklefin 

chub), 3 centrarchids (flier, spotted bass, spotted 

sunfish), and 3 percids (dusky darter, greenside 

darter, slough darter) with primary distributions 

in the Lower Mississippi River, Missouri Ozarks, 

Missouri River Basin, or Ohio River Basin (Table 

2.1). Cyprinidae was the dominant family in 

terms of species richness and composed 30% of 

the species collected from the UMRS (Table 2.3). 

Five families (Catostomidae, Centrarchidae, 

Cyprinidae, Ictaluridae, and Percidae) composed 

72% of the species collected from the UMRS 

(Table 2.3). Open River and Pool 26 had a 

high richness of cyprinids when compared to 

La Grange Pool and the three upriver study areas 

(Pools 4, 8, and 13), whereas Open River and 

Pool 26 had a low richness of catostomids when 

compared to La Grange Pool and upriver study 

areas (Table 2.3). 

Two species, brook stickleback (Culaea 

inconstans) and central mudminnow (Umbra 

limi), were collected in all three upriver study 

areas (Pools 4, 8, and 13), but were absent in 

the lower three study areas (Pool 26, Open 

River, La Grange Pool). Ten species were 

collected in all three of the lower study areas, 

but were absent from samples in the three 

upriver study areas. These species included 

bighead carp (Hypopthalmichthys nobilis), 

blackstripe topminnow (Fundulus olivaceus), 

blue catfish (Ictalurus furcatus), goldfish 

(Carassius auratus), red shiner (Cyprinella 

lutrensis), redear sunfish (Lepomis microlophus), 

silverband shiner (Notropis shumardi), silver carp 

(Hypophthalmichthys molitrix), threadfin shad 

(Dorsoma petenense), and western mosquitofish 

(Gambusia affinis). 

The LTRMP collected seven species of fish 

that are not native to North America in 1993–

2002. Common carp (Cyprinus carpio) was the 

only invasive exotic species captured in all study 

areas, whereas goldfish, silver carp, and bighead 

carp were collected exclusively in the lower 

three study areas. Grass carp (Ctenopharyngodon 

idella) were frequently collected in the lower 

three study areas, but only a single collection was 

made from the upper three study areas. Brown 

trout (Salmo trutta) were collected in Pools 8 

and 13, where they most likely occur as tributary 

strays from coldwater stream stockings. A single 

specimen of rudd (Scardinius erythrophthalmus) 

was collected in Pool 13, and was most likely 

introduced from a baitfish bucket.

Discussion

Pitlo et al. (1995) documented the presence 

of 155 species in the UMR since recordkeeping 

commenced in the late 19th century. Since the 

publication of Pitlo et al (1995) the LTRMP 

collected eight additional species, resulting in 

163 species observations for the UMR. The 

following species caught in the UMR by the 

LTRMP were not listed by Pitlo et al. (1995): 

bigeye chub (Notropis amblops), bleeding shiner 

(Luxilus zonatus), greenside darter (Etheostoma 

blennioides), rudd, spotted sunfish (Lepomis 

punctatus), silver carp, slough darter (Etheostoma 

spectabile), and white perch (Morone 

americana). Twenty‐seven of the species listed 

by Pitlo et al. (1995) were not collected through 

standard LTRMP sampling in 1993–2002, but 

these species were primarily tributary strays 

or species that existed in the UMR based on 

historical records, but may no longer be present. 

Exceptions (i.e., known species found since 1985, 

not considered tributary strays, and not caught 

by the LTRMP) included Alabama shad (Alosa 

alabamae), flathead chub (Platygobio gracilis), 

greater redhorse (Moxostoma valenciennesi), 

pallid sturgeon (Scaphirhynchus albus), sturgeon 

chub (Macrhybopsis gelida), and western silvery 

minnow (Hybognathus argyritis). 

The 18 species collected from all LTRMP 

study areas in all years represent taxa with the 

ability to survive in a wide variety of habitat 

conditions. The loss of any of these species 

from a reach of the UMR would be indicative 

of major habitat alteration or degradation. Most 

ubiquitous species in the Mississippi River are 

representatives of “old” ichthyofauna such as 

sturgeon, gar, bowfin, goldeye, a few cyprinids, a 

few ictiobine suckers, bullhead, crappie, and two 

larger percids, whereas less widely distributed 

species represent “new” adaptively‐radiating 

faunas including the shiners, moxostomine 
suckers, madtoms, topminnows, sculpins, small 

darters, and lepomine sunfishes (Fremling et al. 

1989). Common carp was the only exotic invasive 

species found to be ubiquitous within the system, 

but bighead carp, grass carp, and silver carp 

were commonly collected in lower study areas 

and are widely considered to have an expanding 

distribution within the UMRS. 

The continuation of the LTRMP will ensure 

that shifts in species composition and relative 

abundance can be detected—providing an 

opportunity to address and mitigate for species 

losses. The LTRMP data set also provides the 

ability to identify changes in the distribution 

and relative abundance of species exhibiting a 

limited range within the basin and to detect the 

occurrence of new species (e.g., silver carp). 

Before the LTRMP, it was difficult to discern 

how the distribution of a species has changed 

over time because effort within river reaches was 

sporadic and unequal. As the UMRS continues to 

change, the value of LTRMP species distribution 

and frequency of occurrence information will 

increase. For example, it is believed that the 

distributions of species, such as blue catfish 

(Ictalurus furcatus), lake sturgeon (Acipenser 

fulvescens), and skipjack herring (Alosa 

chrysochloris), has been reduced in the basin 

since the completion of the lock and dams, but it 

is difficult to quantify this change using historical 

data. Tracking changes in species distribution and 

frequency of occurrence provides a means for 

assessing present and future ecosystem health.
Table 2.1. Total years of occurrence (i.e., the number of sampling years where at least one specimen of a species was caught), by study 

area, for fish species collected for the Long Term Resource Monitoring Program in the Upper Mississippi River System in 1993–2002 a. 

Study area

Species Pool 4 Pool 8 Pool 13 Pool 26

LG 

Pool

Open 

River Dist.b Occur.c

Family Petromyzontidae—lampreys

American brook lamprey

(Lampetra appendix) 2 6 0 0 0 0 R O

Chestnut lamprey

(Ichthyomyzon castaneus) 8 10 3 3 3 10 A C

Silver lamprey

(Ichthyomyzon unicuspis) 10 10 9 2 0 0 W C

Family Acipenseridae—sturgeons

Lake sturgeon

(Acipenser fulvescens) 6 1 1 5 0 0 W U

Shovelnose sturgeon

(Scaphirhynchus platorynchus) 10 10 10 9 1 10 A F

Family Polyodontidae—paddlefishes

Paddlefish

(Polyodon spathula) 4 0 0 6 4 8 W O

Family Lepisosteidae—gars

Longnose gar

(Lepisosteus osseus) 10 10 10 10 10 10 A A

Shortnose gar

(Lepisosteus platostomus) 10 10 10 10 10 10 A A

Spotted gar

(Lepisosteus oculatus) 0 0 1 10 10 10 W C

Family Amiidae—bowfins

Bowfin

(Amia calva) 10 10 10 10 10 10 A A

Family Hiodontidae—mooneyes

Goldeye

(Hiodon alosoides) 5 4 2 10 9 10 A C

Mooneye

(Hiodon tergisus) 10 10 10 10 2 6 A F

Family Anguillidae—freshwater eels

American eel

(Anguilla rostrata) 10 2 0 7 5 10 W C

Family Clupeidae—herrings

Gizzard shad

(Dorosoma cepedianum) 10 10 10 10 10 10 A A

Skipjack herring

(Alosa chrysochloris) 1 1 0 10 10 10 W C

Threadfin shad

(Dorosoma petenense) 0 0 0 10 10 9 R F

Family Cyprinidae—carps and minnows

Bigeye chub

(Notropis amblops) 0 0 0 0 0 1 L R

Bigeye shiner

(Notropis boops) 0 0 0 3 0 3 R U

Bighead carp

(Hypopthalmichthys nobilis) 0 0 0 10 7 9 R F

Bigmouth shiner

(Notropis dorsalis) 4 0 1 3 0 0 R U

Blacknose dace

(Rhinichthys atratulus) 1 0 0 0 4 0 R U

Blacktail shiner

(Cyprinella venusta) 0 0 0 0 0 9 L F
10

Table 2.1. (continued) Study area

Species Pool 4 Pool 8 Pool 13 Pool 26

LG 

Pool

Open 

River Dist.

b Occur.c

Bleeding shiner (Luxilus zonatus

)000001LR

Bluntnose minnow (Pimephales notatus

)8757 108AC

Brassy minnow (Hybognathus hankinsoni

)020000LU

Bullhead minnow (Pimephales vigilax

) 10 10 10 10 10 10AA

Central stoneroller (Campostoma anomalum

)101586WO

Channel shiner (Notropis wickliffi

)008 100 10WF

Common carp (Cyprinus carpio

) 10 10 10 10 10 10AA

Creek chub (Semotilus atromaculatus

)013342WU

Emerald shiner (Notropis atherinoides

) 10 10 10 10 10 10AA

Fathead minnow (Pimephales promelas

)5 109291AC

Ghost shiner (Notropis buchanani

)000100LR

Golden shiner (Notemigonus crysoleucas

)9 10 108 103AF

Goldfish (Carassius auratus

)0006 102RC

Grass carp (Ctenopharyngodon idella

)10099 10WC

Hornyhead chub (Nocomis biguttatus

)100000LR

Mimic shiner (Notropis volucellus

) 10 104002WC

Mississippi silvery minnow (Hybognathus nuchalis)

068709WC

Pallid shiner (Notropis amnis

)120000RR

Plains minnow (Hybognathus placitus

)000003LU

Pugnose minnow (Opsopoeodus emiliae

) 10 10 10005WF

Red shiner (Cyprinella lutrensis

)000 10 10 10RA

River shiner (Notropis blennius

) 10 10 10 107 10AF

Rudd (Scardinius erythrophthalmus

)001000LR

Sand shiner (Notropis stramineus

)894 1063AC

Sicklefin chub (Macrhybopsis meeki

)000003LU

Silver carp (Hypophthalmichtyhs molitrix

)000543RO

Silver chub (Macrhybopsis storeriana

) 10 10 10 10 109AF

Silverband shiner (Notropis shumardi

)0009 10 10RF

Southern redbelly dace (Phoxinus erythrogaster

)002000LU

Speckled chub (Macrhybopsis aestivalis

) 104 1080 10WF

Spotfin shiner (Cyprinella spiloptera

) 10 10 10 1006WF
11

Table 2.1. (continued) Study area

Species Pool 4 Pool 8 Pool 13 Pool 26

LG 

Pool

Open 

River Dist.b Occur.c

Spottail shiner

(Notropis hudsonius) 10 10 10 8 10 3 A F

Striped shiner

(Luxilus chrysocephalus) 0 0 0 1 0 1 R R

Suckermouth minnow

(Phenacobius mirabilis) 0 0 5 5 4 0 R O

Weed shiner

(Notropis texanus) 8 10 0 0 0 0 R F

Family Catostomidae—suckers

Bigmouth buffalo

(Ictiobus cyprinellus) 10 10 10 10 10 10 A A

Black buffalo

(Ictiobus niger) 6 2 8 10 10 10 A C

Blue sucker

(Cycleptus elongatus) 10 8 6 8 1 10 A C

Golden redhorse

(Moxostoma erythrurum) 10 10 10 6 10 3 A F

Highfin carpsucker

(Carpiodes velifer) 4 10 10 0 10 0 W F

Northern hog sucker

(Hypentelium nigricans) 6 7 1 0 3 0 W O

Quillback

(Carpiodes cyprinus) 10 10 10 8 10 4 A F

River carpsucker

(Carpiodes carpio) 10 9 10 10 10 10 A F

River redhorse

(Moxostoma carinatum) 10 10 0 0 0 1 R C

Shorthead redhorse

(Moxostoma macrolepidotum) 10 10 10 10 10 9 A F

Silver redhorse

(Moxostoma anisurum) 10 10 9 0 9 0 W F

Smallmouth buffalo

(Ictiobus bubalus) 10 10 10 10 10 10 A A

Spotted sucker

(Minytrema melanops) 10 10 10 1 0 0 W C

White sucker

(Catostomus commersoni) 10 10 8 1 5 0 W C

Family Ictaluridae—bullhead catfishes

Black bullhead

(Ameiurus melas) 7 10 10 7 10 5 A F

Blue catfish

(Ictalurus furcatus) 0 0 0 10 2 10 R C

Brown bullhead

(Ameiurus nebulosus) 3 9 0 7 10 0 W C

Channel catfish

(Ictalurus punctatus) 10 10 10 10 10 10 A A

Flathead catfish

(Pylodictis olivaris) 10 10 10 10 10 10 A A

Freckled madtom

(Noturus nocturnus) 0 0 1 5 3 10 W O

Stonecat

(Noturus flavus) 2 6 8 3 5 6 A O

Tadpole madtom

(Noturus gyrinus) 10 10 10 4 7 2 A C

Yellow bullhead

(Ameiurus natalis) 10 9 10 7 10 3 A F
12

Table 2.1. (continued) Study area

Species Pool 4 Pool 8 Pool 13 Pool 26

LG 

Pool

Open 

River Dist.b Occur.c

Family Esocidae—pikes

Grass pickerel

(Esox americanus vermiculatus) 0 0 1 3 9 0 R O

Muskellunge

(Esox masquinongy) 0 0 0 0 0 1 L R

Northern pike

(Esox lucius) 10 10 10 2 7 0 W C

Family Umbridae—mudminnows

Central mudminnow

(Umbra limi) 2 9 2 0 0 0 R O

Family Osmeridae—smelts

Rainbow smelt

(Osmerus mordax) 0 1 0 0 0 0 L R

Family Salmonidae—trouts

Brown trout

(Salmo trutta) 0 5 1 0 0 0 R U

Family Percopsidae—trout-perches

Trout perch

(Percopsis omiscomaycus) 9 8 0 0 0 1 R C

Family Aphredoderidae—pirate perches

Pirate perch

(Aphredoderus sayanus) 2 4 0 2 8 3 W U

Family Gadidae—cods

Burbot

(Lota lota) 8 9 0 0 0 0 R F

Family Cyprinodontidae—killifishes

Blackspotted topminnow

(Fundulus olivaceus) 0 0 0 0 0 4 L O

Blackstripe topminnow

(Fundulus notatus) 0 0 0 3 10 10 R C

Starhead topminnow

(Fundulus dispar) 0 0 0 1 0 0 L R

Family Poeciliidae—livebearers

Western mosquitofish

(Gambusia affinis) 0 0 0 10 10 10 R A

Family Atherinidae—silversides

Brook silverside

(Labidesthes sicculus) 9 10 10 10 10 9 A F

Inland silverside

(Menidia beryllina) 0 0 0 0 0 3 L U

Family Gasterosteidae—sticklebacks

Brook stickleback

(Culaea inconstans) 3 4 2 0 0 0 R U

Family Percichthyidae—temperate basses

Striped bass

(Morone saxatilis) 0 0 0 0 7 7 R C

White bass

(Morone chrysops) 10 10 10 10 10 10 A A

White perch

(Morone americana) 0 0 0 1 10 0 R O

Yellow bass

(Morone mississippiensis) 0 7 10 9 10 6 W F
1

3

Table 2.1. (continued) Study area

Species Pool 4 Pool 8 Pool 13 Pool 26

LG 

Pool

Open 

River Dist.

b Occur.c

Family Centrarchidae—sunfishes

Black crappie (Pomoxis nigromaculatus

) 10 10 10 10 10 10AA

Bluegill (Lepomis macrochirus

) 10 10 10 10 10 10AA

Flier (Centrarchus macropterus

)000002LU

Green sunfish (Lepomis cyanellus

) 10 108 10 10 10AF

Largemouth bass (Micropterus salmoides

) 10 10 10 10 10 10AA

Longear sunfish (Lepomis megalotis

)000028RO

Orangespotted sunfish (Lepomis humilis)

7 10 10 10 10 10AF

Pumpkinseed (Lepomis gibbosus

) 10 10 10020WF

Redear sunfish (Lepomis microlophus

)000483RO

Rock bass (Ambloplites rupestris

) 10 10 10010WC

Smallmouth bass (Micropterus dolomieu

) 10 10 10482AC

Spotted bass (Micropterus punctulatus

)00000 10LA

Spotted sunfish (Lepomis punctatus

)000001LR

Warmouth (Lepomis gulosus

)0 10 10 10 10 10WA

White crappie (Pomoxis annularis

) 10 10 10 10 10 10AA

Family Percidae—perches

Banded darter (Etheostoma zonale

)330000RU

Blackside darter (Percina maculata

)250021WU

Bluntnose darter (Etheostoma chlorosomum

)004004RO

Crystal darter (Ammocrypta asprella

)330000RU

Dusky darter (Percina sciera

)000006LC

Fantail darter (Etheostoma flabellare

)031000RU

Greenside darter (Etheostoma blennioides

)000001LR

Iowa darter (Etheostoma exile

)070000LC

Johnny darter (Etheostoma nigrum

) 10 10 10073WC

Logperch (Percina caprodes

) 10 10 10 10 109AF

Mud darter (Etheostoma asprigene

)8 109796AF

Orangethroat darter (Etheostoma spectabile

)000001LR

River darter (Percina shumardi

) 10 10 10906WF

Sauger (Sander canadensis

) 10 10 10 10 10 10AA

Slenderhead darter (Percina phoxocephala

)9 109562AC
14

Table 2.1. (continued) Study area

Species Pool 4 Pool 8 Pool 13 Pool 26

LG 

Pool

Open 

River Dist.b Occur.c

Slough darter

(Etheostoma gracile) 0 0 0 0 0 1 L R

Walleye

(Sander vitreus) 10 10 10 8 10 2 A F

Western sand darter

(Ammocrypta clara) 8 10 6 3 0 2 W O

Yellow perch

(Perca flavescens) 10 10 10 1 2 0 W C

Family Sciaenidae—drums

Freshwater drum

(Aplodinotus grunniens) 10 10 10 10 10 10 A A

Family Mugilidae—mullets

Striped mullet

(Mugil cephalus) 0 0 0 0 0 1 L R

a Species were assigned to distribution categories (Dist.) and frequency of occurrence categories (Occur.) based upon the 

number of study areas in which collected and the average frequency (percentage of years) collected within study areas of 

occurrence. The table shows a phylogenic sequence of families of fishes, with species listed alphabetically by common 

name within family groups. The phylogenic sequence, scientific names (family, genus, and species), and common names 

followed that of Nelson et al. (2004).

b

 Distribution categories

A— Collected in all LTRMP study areas during 1993–2002.

W— Widespread distribution, collected in 4 or 5 LTRMP study areas during 1993–2002.

R— Regional distribution, collected in 2 or 3 LTRMP study areas during 1993–2002.

L— Local distribution, collected in 1 LTRMP study area during 1993–2002. c

 Frequency of occurrence categories

A— always collected within a sampling year, collected in all years within study areas of occurrence.

F— frequently collected within a sampling year, collected on average in 80–99% of years within study areas of 

occurrence.

C— commonly collected within a sampling year, collected on average in 60–79% of years within study areas of 

occurrence.

O— occasionally collected within a sampling year, collected on average in 40–59% of years within study areas of 

occurrence.

U— uncommonly collected, collected on average in 20–39% of years within study areas of occurrence.

R— rarely collected, collected on average in 1–19% of years within study areas of occurrence.

Table 2.2. Species counts within distribution and frequency of occurrence categories for fish species collected for the Long Term 

Resource Monitoring Program in the Upper Mississippi River System in 1993–2002. 

Frequency of occurrenceb

Distributiona Always Frequent Common Occasional Uncommon Rare

All study areas 18 18 10 1 0 0

Widespread 1 9 13 5 4 0

Regional 2 6 6 9 8 2

Local 1 1 2 1 6 13

a

Distribution categories were as follows:

all study areas = collected in all six Long Term Resource Monitoring Program study areas,

widespread = collected in four or five study areas,

regional = collected in two or three study areas, and

local = collected in one study area. b

Frequency of occurrence categories were as follows:

always = collected in all years within study areas of occurrence,

frequent = collected on average in 80–99% of years within study areas of occurrence,

common = collected on average in 60–79% of years within study areas of occurrence,

occasional = collected on average in 40–59% of years within study areas of occurrence,

uncommon = collected on average in 20–39% of years within study areas of occurrence, and

rare = collected on average in 1–19% of years within study areas of occurrence.

(For example, 13 species of fish commonly occurred within a widespread distribution in the UMRS.)
15

Table 2.3. Total species richness by study area and family, for fishes collected for the Long Term Resource Monitoring Program in the 

Upper Mississippi River System in 1993–2002. 

Study area

Familya Pool 4 Pool 8 Pool 13 Pool 26 LG Poolb

Open 

River

All 

Areas

Family Petromyzontidae

(lampreys) 3 3 2 2 1 1 3

Family Acipenseridae

(sturgeons) 2 2 2 2 1 1 2

Family Polyodontidae

(paddlefishes) 1 0 0 1 1 1 1

Family Lepisosteidae

(gars) 2 2 3 3 3 3 3

Family Amiidae

(bowfins) 1 1 1 1 1 1 1

Family Hiodontidae

(mooneyes) 2 2 2 2 2 2 2

Family Anguillidae

(freshwater eels) 1 1 0 1 1 1 1

Family Clupeidae 

(herrings) 2 2 1 3 3 3 3

Family Cyprinidae

(carps and minnows) 21 19 22 27 20 31 41

Family Catostomidae

(suckers) 14 14 13 10 12 9 14

Family Ictaluridae

(bullhead catfishes) 7 7 7 9 9 8 9

Family Esocidae

(pikes) 1 1 2 2 2 1 3

Family Umbridae

(mudminnows) 1 1 1 0 0 0 1

Family Osmeridae

(smelts) 0 1 0 0 0 0 1

Family Salmonidae

(trouts) 0 1 1 0 0 0 1

Family Percopsidae

(trout-perches) 1 1 0 0 0 1 1

Family Aphredoderidae

(pirate perches) 1 1 0 1 1 1 1

Family Gadidae

(cods) 1 1 0 0 0 0 1

Family Cyprinodontidae

(killifishes) 0 0 0 2 1 2 3

Family Poeciliidae

(livebearers) 0 0 0 1 1 1 1

Family Atherinidae

(silversides) 1 1 1 1 1 2 2

Family Gasterosteidae

(sticklebacks) 1 1 1 0 0 0 1

Family Percichthyidae

(temperate basses) 1 2 2 3 4 3 4

Family Centrarchidae

(sunfishes) 9 10 10 9 12 13 15

Family Percidae

(perches) 12 14 11 8 8 14 19

Family Sciaenidae

(drums) 1 1 1 1 1 1 1

Family Mugilidae

(mullets) 0 0 0 0 0 1 1

All Families

(total species richness) 86 89 83 89 85 101 136

a

The phylogenic sequence, scientific names, and common names followed that of Nelson et al. (2004). 

b

LG pool is La Grange Pool.
16

Chapter 3. Spatial Patterns in 

Length‐frequency Distributions

Introduction

Length‐frequency distributions are 

commonly used by fisheries managers to assess 

the size structure of fish populations and can 

identify problems such as low recruitment, slow 

growth, or excessive annual mortality (Anderson 

and Neumann 1996). The length‐frequency 

distributions of 12 species with recreational 

or commercial importance are displayed 

and evaluated in this chapter. Categorical 

(length‐based) catch‐per–unit‐effort (CPUE) is 

also provided for each species to supplement 

the information provided by length‐frequency 

distributions. The objective of this evaluation 

was to visually and quantitatively assess spatial 

differences in length frequencies among Long 

Term Resource Monitoring Program (LTRMP) 

study areas.

Methods

Twelve fish species with direct commercial 

or recreational importance were identified as 

being common and widespread in LTRMP 

study areas (i.e., collected in all study areas 

in all years 1993–2002) and were chosen for 

length‐frequency distribution analysis. The 

commercially harvested species were bigmouth 

buffalo (Ictiobus cyprinellus), common carp 

(Cyprinus carpio), channel catfish (Ictalurus 

punctatus), flathead catfish (Pylodictis olivaris), 

freshwater drum (Aplodinotus grunniens), 

and smallmouth buffalo (Ictiobus bubalus), 

and the noncommercially harvested species 

were black crappie (Pomoxis nigromaculatus), 

bluegill (Lepomis macrochirus), largemouth 

bass (Micropterus salmoides), sauger (Sander 

canadensis), white bass (Morone chrysops), and 

white crappie (Pomoxis annularis). For each 

species, the sampling gear having the highest 

total catch of stock‐length fish among study areas 

was used for analysis (stock‐length designations, 

Anderson and Neumann 1996; Bister et al. 2000). 

Analysis was limited to the single gear with the 

highest total catch to maximize sample size and 

to avoid bias associated with combining multiple 

gears.

For each species and study area, a five‐cell 

relative length frequency was calculated for data 

from 1993 to 2002 combined—where the value 

in each cell was the proportion of the total catch 

falling within the length category represented 

by the cell. Only species with a sample size of 

>40 from each study area for selected gears 

were included in analyses. The length categories 

used for the five cells were determined by 

the following criteria: (1) Gabelhouse (1984) 

incremental length categories (i.e., stock‐quality, 

quality‐preferred, preferred‐memorable, 

memorable‐trophy, and greater than or equal to 

trophy) were used if at least one specimen of 

trophy length had been captured and (2) if no 

trophy‐length specimens had been captured, five 

categories of equal increment were constructed 

beginning with stock length and ending with 

a category including the length of the largest 

individual captured.

The relative length‐frequency technique 

(Bonar 2002) was used to visually evaluate 

the length‐frequency distribution of selected 

species in study areas. This technique uses 

the average length frequency (ALF) as a 

reference distribution that can be compared to 

length‐frequency distributions of interest. For 

each species, the ALF is the average of the 

relative length‐frequency distribution in the six 

LTRMP study areas.

A Kolmogorov‐Smirnov statistic (KS; 

NPAR1WAY procedure, empirical distribution 

function [EDF] option; SAS Institute 1999) 

was used to quantify differences among the 

length‐frequency distributions of study areas. 

Continuous length data for stock‐length fish, 

rather than categorical data were applied to the 

Kolmogorov‐Smirnov test (i.e., data sets were 

composed of “raw” length values for each fish 

collected). The additive inverse of the maximum 

deviation between the pooled EDF and the 

EDF from study areas was used to quantify 

the magnitude of the difference between the 

pooled and study area distributions. Positive 

values for the maximum deviation between 

the pooled EDF and the EDF from a study 

area represent length‐frequency distributions 

composed of a higher than average proportion 

of long fish. Negative values for the maximum 
17

deviation between the pooled EDF and the EDF 

from a study area represent length‐frequency 

distributions composed of a higher than average 

proportion of short fish.

For each study area, estimates of pooled 

(all sampling strata) areawide mean CPUE were 

calculated for each length category of each of 

the selected species for 1993–2002. Mean CPUE 

data supplements relative frequency information 

as an index of categorical abundance, within each 

length group and study area, that is independent 

of the total catch in other length groups and study 

areas (i.e., relative frequency within a category 

is dependent upon total catch within other length 

categories, and mean CPUE is not dependent 

upon total catch in other categories). This 

analysis was limited to the same sampling gears 

used in length‐frequency analyses from random 

stratified monitoring. Statistical methods for 

estimates of areawide mean CPUE and associated 

standard error followed that of Gutreuter et al. 

(1995). Inferential statistics were not used to test 

the significance of differences among study area 

CPUE.

Results

Length frequency histograms are displayed 

for each study area in the following figures: 

Figure 3.1, bigmouth buffalo; Figure 3.2, black 

crappie; Figure 3.3, bluegill; Figure 3.4, channel 

catfish; Figure 3.5, common carp; Figure 3.6, 

flathead catfish; Figure 3.7, freshwater drum; 

Figure 3.8, largemouth bass; Figure 3.9, sauger; 

Figure 3.10, smallmouth buffalo; Figure 3.11, 

white bass; Figure 3.12, white crappie. Spatial 

differences in length‐frequency distributions 

were most pronounced (KS > 0.200, Table 3.1) 

for common carp (Figure 3.5), flathead catfish 

(Figure 3.6), and smallmouth buffalo ( Figure 

3.10), and least pronounced (KS < 0.100, Table 

3.1) for black crappie (Figure 3.2), bluegill 

(Figure 3.3), largemouth bass (Figure 3.8), sauger 

(Figure 3.9), and white bass (Figure 3.11). No 

commercially harvested species exhibited a KS 

value of <0.100, and only one noncommercially 

harvested species (i.e., white crappie) exhibited a 

KS value of >0.100 (Table 3.1).

In Pool 4, all species exhibited a 

length‐frequency distribution composed of a high 

proportion of long fish when compared to the 

pooled distributions (Table 3.1). In Pool 8, all 

commercially harvested species, black crappie, 

and white crappie exhibited a length‐frequency 

distribution composed of a high proportion 

of long fish when compared to the pooled 

distributions. In Pool 13, 6 out of 12 species 

exhibited a length‐frequency composed of a 

high proportion of long fish when compared to 

the pooled distributions. In Pool 26, only white 

crappie exhibited a length‐frequency distribution 

composed of a high proportion of long fish 

when compared to the pooled distribution. In 

the Open River study area (Open River; river 

mile 29 to 80), 9 out of 12 species exhibited a 

length‐frequency distribution composed of a 

high proportion of long fish when compared 

to the pooled distributions. In La Grange Pool, 

4 out of 12 species exhibited a length‐frequency 

distribution composed of a high proportion 

of long fish when compared to the pooled 

distributions.

Pooled areawide CPUE point estimates 

(hereafter referred to as CPUE estimates or catch 

rates) generally reflected size‐structure patterns 

revealed through the analysis of relative length 

frequency (Tables 3.2–3.13). Catch rates were 

low (<0.15 fish/unit effort) for the longest length 

groups (fifth category) of all species in all years 

and study areas and are not presented. La Grange 

Pool was the only study area to catch long (580–

679 mm) bigmouth buffalo in all 10 sampling 

years and exhibited the highest catch rates for 

shorter (280–579 mm) bigmouth buffalo in most 

years (Table 3.2). Pool 4 had the highest CPUE 

estimates for long (300–379 mm) black crappie 

in 6 of 10 sampling years, and Open River 

consistently exhibited the lowest catch rates for 

all intermediate size classes (130–299 mm) of 

black crappie (Table 3.3). Pool 13 had the highest 

CPUE estimates for long (185–219 mm) bluegill 

in 7 out of 10 sampling years. The highest 

CPUE estimates for intermediate‐sized bluegill 

(115–184 mm) were exclusively within upriver 

study areas (Pools 4, 8, and 13) or La Grange 

Pool (Table 3.4). Channel catfish CPUE estimates 

were low (<0.5 fish/net night) for long fish (> 

480 mm) in all study areas, were highest in 

upriver study areas for intermediate‐sized fish 
18

(380–479 mm), and were highest for short fish 

(280–379 mm) in Pools 8 and 26 (Table 3.5). 

The highest CPUE estimates for long common 

carp (> 530 mm) were in upriver study areas in 

all years, whereas the highest CPUE estimates 

for short (280–409 mm) common carp were in 

Pool 26 or La Grange Pool in all years (Table 

3.6). Flathead catfish CPUE estimates were 

low (≤0.3 fish/net night) for all size categories 

in all study areas and all years (Table 10). 

Catch‐per‐unit‐effort estimates for long (510–629 

mm) freshwater drum were low (≤0.2 fish/net 

night) in all study areas and years, were highest 

for intermediate‐sized (380–509 mm) fish in 

Pool 26 for 7 out of 10 years, and were highest 

for short (200–299 mm) fish in lower study areas 

(Pool 26, Open River, La Grange Pool) in all 

years (Table 3.8). Pool 13 had the highest CPUE 

estimates for long (350–424 mm) largemouth 

bass in 7 out of 10 years, and the highest CPUE 

estimates for shorter (200–349 mm) largemouth 

bass were in Pools 8 and 13 or La Grange Pool 

in 9 out of 10 years (Table 3.9). Sauger CPUE 

estimates were low (≤0.9 fish/15 min) for all 

size categories in all study areas and years 

(Table 3.10). Pools 4 or 26 had the highest CPUE 

estimates for intermediate‐sized (500–609 mm) 

smallmouth buffalo in all years, and Pool 26 or 

La Grange Pool had the highest CPUE point 

estimates for short (280–499 mm) smallmouth 

buffalo in all years (Table 3.11). Pool 4 or 

La Grange Pool had the highest CPUE estimates 

for intermediate‐sized (300–379 mm) white bass 

in 9 out of 10 years, and La Grange Pool had 

the highest CPUE estimates for short (150–229 

mm) white bass in 7 out of 10 years (Table 3.12). 

Pool 13 had CPUE estimates for long (300–379 

mm) white crappie greater than or equal to 

all other pools in all years, and Pool 13 or 

La Grange Pool had the highest CPUE estimates 

for shorter (130–299 mm) white crappie in all 

years (Table 3.13).

Discussion

Observed length‐frequency distributions of 

fish populations are a product of the populations 

dynamic rate functions (i.e., reproduction, 

recruitment, growth, and mortality), gear bias, 

and sampling bias (Anderson and Neumann 

1996). The LTRMP uses standardized gears and 

sampling procedures to help ensure that biases 

are similar when comparing indices among study 

areas. Therefore, we assumed that among study 

area differences in length‐frequency distributions 

reflect differences in dynamic rate functions. The 

factors determining reproduction, recruitment, 

and growth of fish stocks in rivers are generally 

related to physical habitat, hydrology, or climate 

(Meals and Miranda 1991; Maceina and Betolli 

1998; Sheehan and Rasmussen 1999; Pitlo 2002). 

Mortality of stock‐length fish is also influenced 

by environmental factors, but exploitation can 

contribute significantly to total annual mortality, 

particularly in commercial fisheries (Pitlo 1997; 

Maceina et al. 1998; Mestl 1999; Timmons and 

Hughbanks 2000).

Spatial differences in length‐frequency 

distributions were more pronounced for 

commercially exploited fish species than for 

species exploited solely by recreational angling. 

The following two mechanisms could explain 

the observed differences between commercial 

and recreational species: (1) the commercial 

species generally obtain a larger maximum 

length and maximum age when compared 

to recreational species, which magnifies the 

effects of subtle environmental differences that 

effect reproduction, recruitment, growth, and 

mortality among study areas and (2) commercial 

exploitation rates are different among study 

areas, which influences the length‐frequency 

distribution of populations, but recreational 

exploitation either has comparatively little 

influence on size structure or is relatively 

similar among study areas. One or both of these 

mechanisms could explain the observed spatial 

differences in size structure. Previous studies 

suggest that commercial fishing can truncate size 

structures in large river populations (Mestl 1999; 

Timmons and Hughbanks 2000; Travnichek 

and Clemons 2001). Reach‐specific growth 

rates can also contribute to spatial differences 

in size structure within a river system (Kirby 

2001). Additional research into the reproduction, 

recruitment, growth, mortality, and exploitation 

of species exhibiting significant spatial variability 

in size structure will help provide answers.
19

It is important to consider abundance when 

comparing relative length‐frequency distributions 

among areas because the abundance of long 

fish may be low even in situations where 

length‐frequency distributions are composed of 

a high proportion of long fish (or vice versa). 

For example, bigmouth buffalo in La Grange 

Pool had a relative length frequency composed 

of a low proportion of long fish when compared 

to other study areas, but also had highest 

CPUE estimates for long fish in most years. 

Furthermore, the recreational or commercial 

value of a fishery is dependent upon size 

structure, as well as abundance.

This observational investigation identified 

spatial patterns in the length‐frequency 

distributions and categorical (length‐based) 

relative abundance of recreational and 

commercial fishes, but does not provide factors 

responsible for patterns. Future research should 

strive to identify factors driving spatial patterns 

to supply resource managers with mechanisms 

for improving the abundance and size structure 

of fish stocks. Factors driving UMR spatial 

patterns in fish abundance and size structure 

are most likely tied to habitat dynamics. For 

example, centrarchid species (black crappie, 

bluegill, largemouth bass) in Pools 4, 8, and 

13, and La Grange Pool exhibited high CPUE 

estimates and length frequencies composed of 

proportionally more long fish when compared to 

Pool 26 and Open River. This trend is probably 

caused by the increased availability of suitable 

backwater habitat in Pools 4, 8, and 13, and 

La Grange Pool when compared to Open River 

and Pool 26. Chapter 5 provides a detailed 

analysis of fish species abundance variation and 

identifies the relative importance and spatial scale 

of factors affecting abundance.
20

0

20

40

60

80

100

280-379 380-479 480-579 580-679 680-779

Total Length (mm)

Relative Frequency (%)

ALF Pool 4

N = 68

 

0

20

40

60

80

100

280-379 380-479 480-579 580-679 680-779

Total Length (mm)

Relative Frequency (%)

ALF Pool 8

N = 50

0

20

40

60

80

100

280-379 380-479 480-579 580-679 680-779

Total Length (mm)

Relative Frequency (%)

ALF Pool 13

N = 170

0

20

40

60

80

100

280-379 380-479 480-579 580-679 680-779

Total Length (mm)

Relative Frequency (%)

ALF Pool 26

N = 286

0

20

40

60

80

100

280-379 380-479 480-579 580-679 680-779

Total Length (mm)

Relative Frequency (%)

ALF La Grange Pool

N = 4,621

0

20

40

60

80

100

280-379 380-479 480-579 580-679 680-779

Total Length (mm)

Relative Frequency (%)

ALF Open River

N = 199

Figure 3.1. Relative length-frequency distributions of bigmouth buffalo (Ictiobus cyprinellus) collected by day electrofishing in the Long 

Term Resource Monitoring Program study areas in 1993–2002. The average length frequency (ALF; Bonar 2002) is the average of relative 

length frequencies for the six study areas in 1993–2002. 

Bigmouth buffalo (Ictiobus cyprinellus) 
21

0

20

40

60

80

100

130−199 200−249 250−299 300−379 ≥380

Total Length (mm)

Relative Frequency (%)

ALF Pool 4

N = 1,789

0

20

40

60

80

100

130−199 200−249 250−299 300−379 ≥380

Total Length (mm)

Relative Frequency (%)

ALF Pool 8

N = 7,504

0

20

40

60

80

100

130−199 200−249 250−299 300−379 ≥380

Total Length (mm)

Relative Frequency (%)

ALF Pool 13

N = 3,390

0

20

40

60

80

100

130−199 200−249 250−299 300−379 ≥380

Total Length (mm)

Relative Frequency (%)

ALF Pool 26

N = 1,075

0

20

40

60

80

100

130−199 200−249 250−299 300−379 ≥380

Total Length (mm)

Relative Frequency (%)

ALF La Grange Pool

N = 6,676

0

20

40

60

80

100

130−199 200−249 250−299 300−379 ≥380

Total Length (mm)

Relative Frequency (%)

ALF Open River

N = 129

Figure 3.2. Relative length-frequency distributions of black crappie (Pomoxis nigromaculatus) collected by fyke nets (1.8-cm bar measure 

mesh, 0.9-m x 1.8-m frame) in the Long Term Resource Monitoring Program study areas in 1993–2002. The average length frequency 

(ALF; Bonar 2002) is the average of relative length frequencies for the six study areas in 1993–2002. 

Black crappie (Pomoxis nigromaculatus)
22

0

20

40

60

80

100

80-114 115-149 150-184 185-219 220-254

Total Length (mm)

Relative Frequency (%)

ALF Pool 4

N = 2,417

0

20

40

60

80

100

80-114 115-149 150-184 185-219 220-254

Total Length (mm)

Relative Frequency (%)

ALF Pool 8

N = 7,020

0

20

40

60

80

100

80-114 115-149 150-184 185-219 220-254

Total Length (mm)

Relative Frequency (%)

ALF Pool 13

N = 4,371

0

20

40

60

80

100

80-114 115-149 150-184 185-219 220-254

Total Length (mm)

Relative Frequency (%)

ALF Pool 26

N = 2,217

0

20

40

60

80

100

80-114 115-149 150-184 185-219 220-254

Total Length (mm)

Relative Frequency (%)

ALF La Grange Pool

N = 9,369

0

20

40

60

80

100

80-114 115-149 150-184 185-219 220-254

Total Length (mm)

Relative Frequency (%)

ALF Open River

N = 393

Figure 3.3. Relative length-frequency distributions of bluegill (Lepomis macrochirus) collected by day electrofishing in the Long Term 

Resource Monitoring Program study areas in 1993–2002. The average length frequency (ALF; Bonar 2002) is the average of relative length 

frequencies for the six study areas in 1993–2002. 

 

Bluegill (Lepomis macrochirus)
23

0

20

40

60

80

100

280-379 380-479 480-579 580-679 680-779

Total Length (mm)

Relative Frequency (%)

ALF Pool 4

N = 471

 

0

20

40

60

80

100

280-379 380-479 480-579 580-679 680-779

Total Length (mm)

Relative Frequency (%)

ALF Pool 8

N = 1,643

0

20

40

60

80

100

280-379 380-479 480-579 580-679 680-779

Total Length (mm)

Relative Frequency (%)

ALF Pool 13

N = 418

 

0

20

40

60

80

100

280-379 380-479 480-579 580-679 680-779

Total Length (mm)

Relative Frequency (%)

ALF Pool 26

N = 1,032

0

20

40

60

80

100

280-379 380-479 480-579 580-679 680-779

Total Length (mm)

Relative Frequency (%)

ALF La Grange Pool

N = 498

0

20

40

60

80

100

280-379 380-479 480-579 580-679 680-779

Total Length (mm)

Relative Frequency (%)

ALF Open River

N = 981

Figure 3.4. Relative length-frequency distributions of channel catfish (Ictalurus punctatus) collected by small hoop nets (1.8-cm bar 

measure mesh, 0.6-m hoop diameter) in the Long Term Resource Monitoring Program study areas in 1993–2002. The average length 

frequency (ALF; Bonar 2002) is the average of relative length frequencies for the six study areas in 1993–2002. 

Channel catfish (Ictalurus punctatus)
24

0

20

40

60

80

100

280−409 410−529 530−659 660−839 ≥840

Total Length (mm)

Relative Frequency (%)

ALF Pool 4

N = 4,567

0

20

40

60

80

100

280−409 410−529 530−659 660−839 ≥840

Total Length (mm)

Relative Frequency (%)

ALF Pool 8

N = 4,180

0

20

40

60

80

100

280−409 410−529 530−659 660−839 ≥840

Total Length (mm)

Relative Frequency (%)

ALF Pool 13

N = 4,452

0

20

40

60

80

100

280−409 410−529 530−659 660−839 ≥840

Total Length (mm)

Relative Frequency (%)

ALF Pool 26

N = 8,525

0

20

40

60

80

100

280−409 410−529 530−659 660−839 ≥840

Total Length (mm)

Relative Frequency (%)

ALF La Grange Pool

N = 17,686

0

20

40

60

80

100

280−409 410−529 530−659 660−839 ≥840

Total Length (mm)

Relative Frequency (%)

ALF Open River

N = 2,279

Figure 3.5. Relative length-frequency distributions of common carp (Cyprinus carpio) collected by day electrofishing in the Long Term 

Resource Monitoring Program study areas in 1993–2002. The average length frequency (ALF; Bonar 2002) is the average of relative length 

frequencies for the six study areas in 1993–2002. 

 

Common carp (Cyprinus carpio)
25

0

20

40

60

80

100

350-509 510-709 710-859 860-1019 > 1020

Total Length (mm)

Relative Frequency (%)

ALF Pool 4

N = 133

0

20

40

60

80

100

350-509 510-709 710-859 860-1019 > 1020

Total Length (mm)

Relative Frequency (%)

ALF Pool 8

N = 187

0

20

40

60

80

100

350-509 510-709 710-859 860-1019 > 1020

Total Length (mm)

Relative Frequency (%)

ALF Pool 13

N = 83

0

20

40

60

80

100

350-509 510-709 710-859 860-1019 > 1020

Total Length (mm)

Relative Frequency (%)

ALF Pool 26

N = 114

0

20

40

60

80

100

350-509 510-709 710-859 860-1019 > 1020

Total Length (mm)

Relative Frequency (%)

ALF La Grange Pool

N = 123

0

20

40

60

80

100

350-509 510-709 710-859 860-1019 > 1020

Total Length (mm)

Relative Frequency (%)

ALF Open River

N = 235

Figure 3.6. Relative length-frequency distributions of flathead catfish (Pylodictis olivaris) collected by large hoop nets (3.7-cm bar 

measure mesh, 1.2-m hoop diameter) in the Long Term Resource Monitoring Program study areas in 1993–2002. The average length 

frequency (ALF; Bonar 2002) is the average of relative length frequencies for the six study areas in 1993–2002.

 

Flathead catfish (Pylodictis olivaris) 
26

0

20

40

60

80

100

200−299 300−379 380−509 510−629 ≥630

Total Length (mm)

Relative Frequency (%)

ALF Pool 4

N = 816

 

0

20

40

60

80

100

200−299 300−379 380−509 510−629 ≥630

Total Length (mm)

Relative Frequency (%)

ALF Pool 8

N = 407

0

20

40

60

80

100

200−299 300−379 380−509 510−629 ≥630

Total Length (mm)

Relative Frequency (%)

ALF Pool 13

N = 214

0

20

40

60

80

100

200−299 300−379 380−509 510−629 ≥630

Total Length (mm)

Relative Frequency (%)

ALF Pool 26

N = 776

0

20

40

60

80

100

200−299 300−379 380−509 510−629 ≥630

Total Length (mm)

Relative Frequency (%)

ALF La Grange Pool

N = 1,631

0

20

40

60

80

100

200−299 300−379 380−509 510−629 ≥630

Total Length (mm)

Relative Frequency (%)

ALF Open River

N = 515

Figure 3.7. Relative length-frequency distributions of freshwater drum (Aplodinotus grunniens) collected by day electrofishing in the Long 

Term Resource Monitoring Program study areas in 1993–2002. The average length frequency (ALF; Bonar 2002) is the average of relative 

length frequencies for the six study areas in 1993–2002. 

Freshwater drum (Aplodinotus grunniens)
27

0

20

40

60

80

100

200-274 275-349 350-424 425-499 500-574

Total Length (mm)

Relative Frequency (%)

ALF Pool 4

N = 572

 

0

20

40

60

80

100

200-274 275-349 350-424 425-499 500-574

Total Length (mm)

Relative Frequency (%)

ALF Pool 8

N = 1,628

0

20

40

60

80

100

200-274 275-349 350-424 425-499 500-574

Total Length (mm)

Relative Frequency (%)

ALF Pool 13

N = 1,525

0

20

40

60

80

100

200-274 275-349 350-424 425-499 500-574

Total Length (mm)

Relative Frequency (%)

ALF Pool 26

N = 398

0

20

40

60

80

100

200-274 275-349 350-424 425-499 500-574

Total Length (mm)

Relative Frequency (%)

ALF La Grange Pool

N = 2,832

0

20

40

60

80

100

200-274 275-349 350-424 425-499 500-574

Total Length (mm)

Relative Frequency (%)

ALF Open River

N = 48

Figure 3.8. Relative length-frequency distributions of largemouth bass (Micropterus salmoides) collected by day electrofishing in the 

Long Term Resource Monitoring Program study areas in 1993–2002. The average length frequency (ALF; Bonar 2002) is the average of 

relative length frequencies for the six study areas in 1993–2002.

Largemouth bass (Micropterus salmoides)
28

0

20

40

60

80

100

200-269 270-339 340-409 410-479 480-549

Total Length (mm)

Relative Frequency (%)

ALF Pool 4

N = 376

 

0

20

40

60

80

100

200-269 270-339 340-409 410-479 480-549

Total Length (mm)

Relative Frequency (%)

ALF Pool 8

N = 512

 

0

20

40

60

80

100

200-269 270-339 340-409 410-479 480-549

Total Length (mm)

Relative Frequency (%)

ALF Pool 13

N = 257

0

20

40

60

80

100

200-269 270-339 340-409 410-479 480-549

Total Length (mm)

Relative Frequency (%)

ALF Pool 26

N = 140

0

20

40

60

80

100

200-269 270-339 340-409 410-479 480-549

Total Length (mm)

Relative Frequency (%)

ALF La Grange Pool

N = 266

0

20

40

60

80

100

200-269 270-339 340-409 410-479 480-549

Total Length (mm)

Relative Frequency (%)

ALF Open River Reach

N = 44

Figure 3.9. Relative length-frequency distributions of sauger (Sander canadensis) collected by day electrofishing in the Long Term 

Resource Monitoring Program study areas in 1993–2002. The average length frequency (ALF; Bonar 2002) is the average of relative 

length frequencies for the six study areas in 1993–2002.

Sauger (Sander canadensis)
29

0

20

40

60

80

100

280-389 390-499 500-609 610-729 730-849

Total Length (mm)

Relative Frequency (%)

ALF Pool 4

N = 1,183

0

20

40

60

80

100

280-389 390-499 500-609 610-729 730-849

Total Length (mm)

Relative Frequency (%)

ALF Pool 8

N = 1,070

0

20

40

60

80

100

280-389 390-499 500-609 610-729 730-849

Total Length (mm)

Relative Frequency (%)

ALF Pool 13

N = 2,255

0

20

40

60

80

100

280-389 390-499 500-609 610-729 730-849

Total Length (mm)

Relative Frequency (%)

ALF Pool 26

N = 3,115

0

20

40

60

80

100

280-389 390-499 500-609 610-729 730-849

Total Length (mm)

Relative Frequency (%)

ALF La Grange Pool

N = 4,797

0

20

40

60

80

100

280-389 390-499 500-609 610-729 730-849

Total Length (mm)

Relative Frequency (%)

ALF Open River

N = 1,525

Figure 3.10. Relative length-frequency distributions of smallmouth buffalo (Ictiobus bubalus) collected by large hoop nets (3.7-cm bar 

measure mesh, 1.2-m hoop diameter) in the Long Term Resource Monitoring Program study areas in 1993–2002. The average length 

frequency (ALF; Bonar 2002) is the average of relative length frequencies for the six study areas in 1993–2002.

Smallmouth buffalo (Ictiobus bubalus) 
30

0

20

40

60

80

100

150−229 230−299 300−379 380−459 ≥460

Total Length (mm)

Relative Frequency (%)

ALF Pool 4

N = 850

 

0

20

40

60

80

100

150−229 230−299 300−379 380−459 ≥460

Total Length (mm)

Relative Frequency (%)

ALF Pool 8

N = 302

 

0

20

40

60

80

100

150−229 230−299 300−379 380−459 ≥460

Total Length (mm)

Relative Frequency (%)

ALF Pool 13

N = 230

0

20

40

60

80

100

150−229 230−299 300−379 380−459 ≥460

Total Length (mm)

Relative Frequency (%)

ALF Pool 26

N = 787

0

20

40

60

80

100

150−229 230−299 300−379 380−459 ≥460

Total Length (mm)

Relative Frequency (%)

ALF La Grange Pool

N = 5,851

0

20

40

60

80

100

150−229 230−299 300−379 380−459 ≥460

Total Length (mm)

Relative Frequency (%)

ALF Open River

N = 491

Figure 3.11. Relative length-frequency distributions of white bass (Morone chrysops) collected by day electrofishing in the Long Term 

Resource Monitoring Program study areas in 1993–2002. The average length frequency (ALF; Bonar 2002) is the average of relative length 

frequencies for the six study areas in 1993–2002.

White bass (Morone chrysops)
31

0

20

40

60

80

100

130−199 200−249 250−299 300−379 ≥380

Total Length (mm)

Relative Frequency (%)

ALF Pool 4

N = 81

0

20

40

60

80

100

130−199 200−249 250−299 300−379 ≥380

Total Length (mm)

Relative Frequency (%)

ALF Pool 8

N = 161

0

20

40

60

80

100

130−199 200−249 250−299 300−379 ≥380

Total Length (mm)

Relative Frequency (%)

ALF Pool 13

N = 1,107

0

20

40

60

80

100

130−199 200−249 250−299 300−379 ≥380

Total Length (mm)

Relative Frequency (%)

ALF Pool 26

N = 260

0

20

40

60

80

100

130−199 200−249 250−299 300−379 ≥380

Total Length (mm)

Relative Frequency (%)

ALF La Grange Pool

N = 2,141

0

20

40

60

80

100

130−199 200−249 250−299 300−379 ≥380

Total Length (mm)

Relative Frequency (%)

ALF Open River

N = 220

Figure 3.12. Relative length-frequency distributions of white crappie (Pomoxis annularis) collected by fyke nets (1.8-cm bar measure 

mesh, 0.9-m x 1.8-m frame) in the Long Term Resource Monitoring Program study areas in 1993–2002. The average length frequency (ALF; 

Bonar 2002) is the average of relative length frequencies for the six study areas in 1993–2002.

White crappie (Pomoxis annularis)
32

Table 3.1. Kolmogorov-Smirnov (KS) statistics for differences in length-frequency distributions of 

stock-length fish among study areas of the Long Term Resource Monitoring Program in 1993–2002. 

Study 

areaa Gearb N

EDF at 

maximumc

Additive inverse of the 

deviation from the mean at 

maximumd KSe

Bigmouth buffalo (Ictiobus cyprinellus)

4 D 68 0.176 5.045

8 D 50 0.440 2.463

13 D 170 0.529 3.375

26 D 286 0.855 -1.156

LG D 4,621 0.818 -2.020

OR D 199 0.520 3.819

Pooled D 55,394 0.788 0.108

Black crappie (Pomoxis nigromaculatus)

4 F 1,789 0.477 4.398

8 F 7,504 0.526 4.795

13 F 3,390 0.475 6.213

26 F 1,075 0.707 -4.119

LG F 6,676 0.705 -10.097

OR F 129 0.605 -0.265

Pooled F 20,563 0.581 0.099

Bluegill (Lepomis macrochirus)

4 D 2,417 0.223 1.360

8 D 7,020 0.333 -6.926

13 D 4,371 0.272 -1.396

26 D 2,217 0.311 -2.830

LG D 9,369 0.174 7.454

OR D 393 0.206 0.883

Pooled D 25,787 0.251 0.067

Channel catfish (Ictalurus punctatus)

4 HS 471 0.251 7.198

8 HS 1,643 0.524 2.357

13 HS 418 0.718 -2.771

26 HS 1,032 0.813 -7.414

LG HS 498 0.671 -1.975

OR HS 981 0.493 2.782

Pooled HS 5,043 0.582 . 0.162

Common carp (Cyprinus carpio)

4 D 4,567 0.124 29.834

8 D 4,180 0.094 30.461

13 D 4,452 0.137 28.613

26 D 8,525 0.612 -4.310

LG D 17,686 0.883 -42.186

OR D 2,279 0.516 2.379

Pooled D 41,689 0.565 0.327

Flathead catfish (Pylodictis olivaris)

4 HL 133 0.188 5.239

8 HL 187 0.460 2.494

13 HL 83 0.952 -2.820

26 HL 114 0.842 -2.133

LG HL 123 0.634 0.090

OR HL 235 0.843 -3.070

Pooled HL 875 0.642 0.252

Freshwater drum (Aplodinotus grunniens)

4 D 816 0.208 5.635

8 D 407 0.251 3.127

13 D 214 0.252 2.242

26 D 776 0.464 -1.625

LG D 1,631 0.527 -4.890

OR D 515 0.433 -0.622

Pooled D 4,359 0.406 0.131
33

Table 3.1. (continued)

Study 

areaa Gearb N

EDF at 

maximumc

Additive inverse of the 

deviation from the mean at 

maximumd KSe

Largemouth bass (Micropterus salmoides)

4 D 572 0.456 1.235

8 D 1,628 0.584 -3.076

13 D 1,525 0.450 2.243

26 D 398 0.651 -2.849

LG D 2,832 0.486 1.173

OR D 48 0.479 0.199

Pooled D 7003 0.508 0.060

Sauger (Sander canadensis)

4 D 376 0.710 0.819

8 D 512 0.842 -2.024

13 D 257 0.774 -0.352

26 D 140 0.786 -0.395

LG D 266 0.673 1.295

OR D 44 0.318 2.880

Pooled D 1,595 0.752 0.097

Smallmouth buffalo (Ictiobus bubalus)

4 HL 1,183 0.089 21.498

8 HL 1,070 0.505 6.841

13 HL 2,255 0.814 -4.767

26 HL 3,115 0.790 -4.237

LG HL 4,797 0.867 -10.639

OR HL 1,525 0.559 6.057

Pooled HL 13,945 0.713 . 0.224

White bass (Morone chrysops)

4 D 850 0.558 7.166

8 D 302 0.874 -1.229

13 D 230 0.813 -0.146

26 D 787 0.844 -1.130

LG D 5,851 0.834 -2.329

OR D 491 0.754 1.105

Pooled D 8,511 0.803 0.085

White crappie (Pomoxis annularis)

4 F 81 0.494 1.200

8 F 161 0.342 3.624

13 F 1,107 0.529 3.255

26 F 260 0.596 0.501

LG F 2,141 0.716 -4.110

OR F 220 0.550 1.145

Pooled F 3,970 0.627 0.105

a

Study areas are abbreviated as 4 = Pool 4, 8 = Pool 8, 13 = Pool 13, 26 = Pool 26, 

LG = La Grange Pool, and OR = Open River. b

Gear types are abbreviated as D = day electrofishing, F = fyke nets, HL = large hoop nets, and 

HS = small hoop nets. c

The KS test measures the maximum difference between the pooled empirical distribution 

function (EDF) and empirical distribution functions from each study area. 

d

Positive values for the additive inverse of the deviation from the mean indicate a distribution 

comprised of proportionally longer fish when compared to the pooled distribution, and negative 

values are indicative of a distribution comprised of proportionally shorter fish. The value for the 

deviation from the mean indicates the magnitude of the difference between the study area and the 

pooled length-frequency distributions. e

A KS statistic <0.1 indicates little difference in length-frequency distributions, whereas values 

>0.2 indicate substantial difference among study areas. 
34

Length category

(mm)

Year

Study 

area 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002

Bigmouth buffalo (Ictiobus cyprinellus)

280–379 Pool 4

0

–a

0

–

0.1 

(0.0)

0

–

0

–

0

–

0

–

0

–

0

–

0

–

Pool 8

0

–

0

–

0.0 

(0.0)

0.0 

(0.0)

0

–

0.0 

(0.0)

0

–

0

–

0

–

0

–

Pool 13

0.0 

(0.0)

0.0 

(0.0)

0.0 

(0.0)

0.3 

(0.1)

0.2 

(0.2)

0

–

0

–

0.0 

(0.0)

0

–

0.0 

(0.0)

Pool 26

0.1 

(0.1)

0

–

0.1 

(0.0)

0.1 

(0.0)

0.1 

(0.1)

0.1 

(0.0)

0.0 

(0.0)

0.0 

(0.0)

0.0 

(0.0)

0.0 

(0.0)

LGb

0.1 

(0.1)

0.5 

(0.1)

0.6 

(0.1)

0.3 

(0.1)

1.6 

(0.5)

1.1 

(0.3)

0.7 

(0.1)

1.7 

(0.5)

1.3 

(0.3)

0.5 

(0.0)

ORc

0.0 

(0.0)

0

–

0

–

0

–

0

–

0

–

0

–

0.1 

(0.1)

0.0 

(0.0)

0

–

380–479 Pool 4

0

–

0.0

(0.0)

0

–

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0

–

0

–

0

–

0

–

Pool 8

0

–

0

–

0

–

0.1

(0.1)

0.0

(0.0)

0

–

0.0

(0.0)

0

–

0

–

0

–

Pool 13

0.2 

(0.1)

0.2

(0.2)

0.0

(0.0)

0.1

(0.1)

0.6

(0.3)

0.2

(0.1)

0.0

(0.0)

0.2

(0.1)

0.0

(0.0)

0.0

(0.0)

Pool 26

.4

(.3)

0.0

(0.0)

0.1

(0.0)

0.1

(0.0)

0.1

(0.1)

0.0

(0.0)

0.1

(0.0)

0.1

(0.1)

0.1

(0.0)

0.0

(0.0)

LG

0.3

(.1)

3.5

(1.0)

0.8

(0.2)

1.5

(0.3)

1.3

(.4)

1.0

(0.2)

0.9

(0.2)

0.9

(0.3)

1.7

(0.4)

1.4

(0.5)

OR

0

–

0.0

(0.0)

0.0

(0.0)

0

–

0

–

0

–

0

–

0.1

(0.1)

0

–

0.1

(0.1)

480–579 Pool 4

0

–

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.1

(0.0)

0.1

(0.0)

0.1

(0.0)

0.1

(0.0)

0

–

Pool 8

0

–

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0

–

0.0

(0.0)

0.0

(0.0)

0

–

0

–

0

–

Pool 13

0.2

(0.2)

0.1

(0.1)

0

–

0.0

(0.0)

0.2

(0.2)

0.0

(0.0)

0.0

(0.0)

0.2

(0.2)

0.1

(0.1)

0.0

(0.0)

Pool 26

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0

–

0.0

(0.0)

0

–

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0

–

LG

0.0

(0.0)

0.7

(0.3)

0.2

(0.1)

0.5

(0.1)

0.4

(0.1)

0.2

(0.1)

0.2

(0.1)

0.2

(0.1

0.3

(0.1)

0.4

(0.3)

OR

0.2

(0.2)

0.1

(0.1)

0

–

0

–

0

–

0

–

0.1

(0.1)

0.0

(0.0)

0

–

0.0

(0.0)

580–679 Pool 4

0

–

0.0

(0.0)

0.0

(0.0)

0

–

0.0

(0.0)

0

–

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

Pool 8

0

–

0

–

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0

–

0

–

0

–

0

–

0

–

Pool 13

0.1

(0.1)

0

–

0

–

0

–

0

–

0.0

(0.0)

0

–

0.0

(0.0)

0.0

(0.0)

0

–

Pool 26

0

–

0

–

0.0

(0.0)

0

–

0.0

(0.0)

0

–

0

–

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

LG

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

OR

0

–

0

–

0.1

(0.1)

0

–

0

–

0

–

0

–

0

–

0

–

0

–

a

– = no fish collected, no estimate b

LG = La Grange Pool c

OR = Open River

Table 3.2. Areawide mean catch-per–unit-effort (fish/15 min) and standard error (in parentheses) estimates by length group for bigmouth 

buffalo (Ictiobus cyprinellus) collected by day electrofishing in Long Term Resource Monitoring Program study areas in 1993–2002.
35

Table 3.3. Areawide mean catch per unit effort (fish/net day) and standard error (in parentheses) estimates by length group for black 

crappie (Pomoxis nigromaculatus) collected by fyke nets in Long Term Resource Monitoring Program study areas in 1993–2002. 

Length category

(mm)

Year

Study 

area 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002

Black crappie (Pomoxis nigromaculatus)

130–199 Pool 4

2.1

(1.0)

1.1

(0.6)

6.6

(2.4)

0.3

(0.2)

2.0

(0.6)

1.9

(0.7)

5.0

(1.4)

8.2

(4.2)

3.9

(1.2)

1.3

(0.8)

Pool 8

16.0

(3.7)

5.9

(1.6)

6.5

(2.0)

15.1

(4.2)

5.0

(1.0)

4.7

(1.0)

8.1

(1.9)

2.5

(0.9)

4.6

(1.5)

2.6

(0.7)

Pool 13

8.3

(2.1)

1.1

(0.4)

4.5

(1.1)

14.6

(3.8)

3.3

(1.1)

1.7

(0.4)

3.8

(1.9)

4.6

(2.6)

7.3

(2.1)

4.0

(1.0)

Pool 26

0.2

(0.2)

3.9

(2.2)

2.1

(0.5)

0.5

(0.2)

0.5

(0.4)

0.4

(0.2)

0.4

(0.2)

0.2

(0.1)

2.2

(0.9)

2.5

(0.7)

LG a

0.3

(0.2)

9.9

(2.4)

15.3

(4.2)

14.3

(4.4)

22.5

(7.0)

3.3

(0.8)

28.3

(7.2)

0.8

(0.3)

4.0

(2.6)

10.2

(3.9)

ORb

0

– c

0

–

2.5

(2.5)

0

–

0

–

0

–

0

–

0

–

0

–

0

–

200–249 Pool 4

1.1

(0.4)

2.7

(1.2)

1.4

(0.9)

1.7

(0.7)

7.9

(0.7)

1.5

(0.7)

2.5

(0.7)

5.4

(1.6)

1.6

(0.5)

0.5

(0.4)

Pool 8

4.3

(1.2)

3.9

(0.8)

2.7

(1.4)

4.8

(1.2)

6.8

(1.5)

4.1

(0.7)

3.5

(0.8)

3.4

(0.6)

2.8

(0.7)

1.3

(0.3)

Pool 13

10.3

(4.0)

6.2

(2.2)

1.5

(0.4)

2.8

(0.9)

4.5

(1.3)

2.2

(0.6)

1.3

(0.5)

3.7

(1.3)

4.0

(1.2)

2.0

(0.5)

Pool 26

0.2

(0.1)

0.2

(0.1)

1.4

(0.5)

0.4

(0.2)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.2

(0.1)

0.8

(0.2)

0.7

(0.3)

LG

1.6

(1.0)

8.1

(3.4)

10.1

(2.7)

6.4

(1.6)

3.3

(1.2)

8.8

(2.8)

4.0

(1.4)

2.0

(0.6)

1.7

(0.5)

2.4

(0.7)

OR

0

–

0

–

0.1

(0.1)

0

–

0

–

0

–

0

–

0

–

0

–

0

–

250–299 Pool 4

0.8

(0.3)

1.3

(0.5)

0.6

(0.2)

0.2

(0.1)

1.2

(0.3)

1.5

(0.7)

1.1

(0.4)

1.2

(0.4)

2.0

(0.9)

0.7

(0.3)

Pool 8

1.8

(0.4)

1.0

(0.4)

0.7

(0.3)

0.6

(0.1)

1.2

(0.3)

1.3

(0.2)

0.7

(0.2)

0.3

(0.1)

1.0

(0.3)

0.8

(0.2)

Pool 13

1.6

(0.7)

2.8

(1.3)

2.0

(0.6)

0.9

(0.5)

0.6

(0.2)

0.6

(0.2)

0.4

(0.2)

0.8

(0.2)

0.8

(0.3)

0.7

(0.3)

Pool 26

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.1

(0.0)

0

–

0.0

(0.0)

0.0

(0.0)

0

–

0.4

(0.1)

0.2

(0.2)

LG

0.4

(0.2)

5.1

(1.9)

0.7

(0.2)

2.6

(0.8)

2.2

(1.0)

0.9

(0.2)

2.5

(0.8)

0.2

(0.1)

0.8

(0.2)

0.5

(0.2)

OR

0

–

0

–

0

–

0

–

0

–

0

–

0

–

0

–

0

–

0

–

300–379 Pool 4

0.1

(0.1)

0.2

(0.1)

0.5

(0.2)

0.5

(0.2)

0

–

0.4

(0.3)

0.3

(0.1)

0.1

(0.1)

0.4

(0.2)

0.1

(0.1)

Pool 8

0.1

(0.1)

0.1

(0.0)

0.1

(0.1)

0.1

(0.1)

0.0

(0.0)

0.1

(0.0)

0.0

(0.0)

0

–

0.1

(0.1)

0

–

Pool 13

0.0

(0.0)

0.1

(0.1)

0.2

(0.1)

0.1

(0.1)

0

–

0

–

0.1

(0.1)

0.1

(0.1)

0.1

(0.0)

0.0

(0.0)

Pool 26

0

–

0

–

0

–

0

–

0.0

(0.0)

0

–

0

–

0

–

0.1

(0.1)

0

–

LG

0

– 

0

–

0

–

0

–

0.0

(0.0)

0.0

(0.0)

0.3

(0.1)

0.0

(0.0)

0.1

(0.0)

0

–

OR

0

–

0

–

0

–

0

–

0

–

0

–

0

–

0

–

0

–

0

–

a

LG = La Grange Pool b

OR = Open River c

 – = no fish collected, no estimate
36

Table 3.4. Areawide mean catch per unit effort (fish/15 min) and standard error (in parentheses) estimates by length group for bluegill 

(Lepomis macrochirus) collected by day electrofishing in Long Term Resource Monitoring Program study areas in 1993–2002. 

Length category

(mm)

Year

Study area 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002

Bluegill (Lepomis macrochirus)

80–114 Pool 4

0.6

(0.3)

0.7

(0.3)

1.4

(0.6)

0.6

(0.2)

1.5

(0.5)

1.5

(0.4)

3.7

(0.9)

2.6

(0.8)

1.2

(0.7)

1.1

(0.3)

Pool 8

0.3

(0.2)

0.4

(0.2)

3.5

(1.0)

7.0

(3.3)

4.3

(1.3)

5.4

(1.2)

4.3

(0.8)

5.5

(0.9)

5.9

(1.2)

1.5

(0.6)

Pool 13

0.7

(0.2)

0.2

(0.1)

3.1

(0.9)

6.8

(2.0)

4.2

(1.0)

6.8

(1.6)

5.9

(3.0)

1.4

(.04)

0.6

(0.2)

1.1

(0.30

Pool 26

0.3

(0.2)

1.1

(0.3)

0.3

(0.1)

0.2

(0.1)

0.3

(0.1)

0.7

(0.2)

0.9

(0.5)

0.5

(0.3)

1.2

(0.6)

0.3

(0.2)

LGa

0.3

(0.1)

2.8

(0.6)

2.4

(0.5)

3.4

(0.8)

2.6

(0.6)

5.1

(1.3)

2.4

(0.5)

1.5

(0.4)

1.3

(0.3)

1.5

(0.3)

ORb

0.9

(0.9)

0.0

(0.0)

0

– c

0.0

(0.0)

0

–

0

–

0

–

0.0

(0.0)

0.1

(0.1)

0.0

(0.0)

115–149 Pool 4

0.1

(0.1)

0.7

(0.3)

0.7

(0.3)

0.4

(0.1)

0.5

(0.2)

1.2

(0.4)

3.2

(1.0)

1.8

(0.5)

0.6

(0.1)

0.3

(0.1)

Pool 8

0.6

(0.3)

0.1

(0.1)

1.1

(0.4)

2.8

(0.8)

1.7

(0.4)

2.4

(0.4)

2.7

(0.6)

2.9

(0.6)

2.2

(0.4)

0.6

(0.4)

Pool 13

1.2

(0.3)

0.4

(0.2)

1.1

(0.4)

2.6

(0.9)

2.6

(0.7)

2.0

(0.4)

5.9

(2.6)

0.8

(0.2)

0.7

(0.3)

0.5

(0.1)

Pool 26

0.2

(0.1)

1.4

(0.4)

0.3

(0.2)

0.1

(0.1)

0.1

(0.1)

0.2

(0.1)

0.5

(0.3)

0.3

(0.2)

1.6

(0.6)

0.2

(0.1)

LG

0.1

(0.1)

2.4

(0.5)

2.0

(0.5)

1.2

(0.3)

2.8

(0.6)

2.7

(0.7)

3.0

(0.5)

1.7

(0.5)

0.9

(0.3)

0.5

(0.2)

OR

0.4

(0.4)

0.0

(0.0)

0

–

0.0

(0.0)

0

–

0

–

0

–

0.0

(0.0)

0.3

(0.2)

0

–

150–184 Pool 4

0.7

(0.2)

0.6

(0.3)

0.2

(0.1)

0.4

(0.1)

0.8

(0.3)

0.7

(0.2)

2.3

(0.5)

1.8

(0.4)

0.7

(0.1)

0.5

(0.1)

Pool 8

0.7

(0.3)

0.4

(0.1)

0.1

(0.1)

1.5

(0.6)

1.0

(0.3)

1.1

(0.2)

2.1

(0.3)

3.2

(0.5)

1.7

(0.4)

0.4

(0.2)

Pool 13

1.2

(0.3)

0.8

(0.2)

0.3

(0.1)

0.8

(0.2)

1.0

(0.3)

2.0

(0.5)

4.8

(3.0)

0.9

(0.2)

0.5

(0.2)

0.3

(0.1)

Pool 26

0.1

(0.10

0.6

(0.2)

0.2

(0.1)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.1

(0.0)

0.1

(0.1)

0.5

(0.2)

0.0

(0.0)

LG

0.1

(0.1)

0.9

(0.2)

1.1

(0.2)

1.0

(0.3)

1.0

(0.4)

2.4

(0.6)

1.5

(0.3)

1.4

(0.3)

0.7

(0.2)

0.4

(0.1)

OR

0

–

0.0

(0.0)

0

–

0

–

0.0

(0.0)

0

–

0

–

0

–

0.1

(0.1)

0.0

(0.0)

185–219 Pool 4

0.1

(0.0)

0.0

(0.0)

0.1

(0.0)

0.0

(0.0)

0.1

(0.0)

0.2

(0.1)

0.1

(0.1)

0.1

(0.0)

0.1

(0.0)

0.0

(0.0)

Pool 8

0.1

(0.0)

0.1

(0.0)

0.0

(0.0)

0.0

(0.0)

0.1

(0.1)

0.2

(0.1)

0.1

(0.0)

0.1

(0.0)

0.3

(0.1)

0.1

(0.1)

Pool 13

0.2

(0.1)

0.3

(0.1)

0.1

(0.0)

0.1

(0.0)

0.1

(0.1)

0.4

(0.1)

0.2

(0.1)

0.2

(0.1)

0.1

(0.0

0.3

(0.1)

Pool 26

0.0

(0.0)

0.0

(0.0)

0

–

0

–

0

–

0

–

0

–

0

–

0

–

0.0

(0.0)

LG

0.1

(0.0)

0.1

(0.0)

0.0

(0.0)

0.0

(0.0)

0.1

(0.1)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

OR

0

–

0

–

0

–

0

–

0

–

0

–

0

–

0

–

0

–

0

–

a

LG = La Grange Pool. b

OR = Open River. c – = no fish collected, no estimate
37

Table 3.5. Areawide mean catch-per-unit-effort (fish/net day) and standard error (in parentheses) estimates by length group for channel 

catfish (Ictalurus punctatus) collected by small hoop nets in Long Term Resource Monitoring Program study areas in 1993–2002. 

Length category

(mm)

Year

Study area 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002

Channel catfish (Ictalurus punctatus)

280–379 Pool 4

0.3

(0.2)

0.1

(0.0)

0.1

(0.0)

0.1

(0.1)

0.2

(0.1)

0.1

(0.1)

0.2

(0.1)

0.1

(0.0)

0.2

(0.1)

0.2

(0.1)

Pool 8

0.4

(0.4)

1.0

(0.4)

1.7

(0.5)

1.1

(0.3)

0.7

(0.2)

0.1

(0.0)

0.2

(0.1)

0.4

(0.2)

0.1

(0.1)

0.1

(0.1)

Pool 13

0.0

(0.0)

0.1

(0.0)

0.4

(0.2)

0.2

(0.1)

0.3

(0.2)

0.1

(0.1)

0.1

(0.0)

0.3

(0.1)

0.5

(0.3)

0.1

(0.0)

Pool 26

0.4

(0.2)

1.6

(0.6)

1.0

(0.3)

0.9

(0.7)

1.4

(0.4)

1.0

(0.7)

0.4

(0.1)

0.6

(0.2)

1.8

(0.4)

0.4

(0.1)

LGa

0.2

(0.1)

0.8

(0.4)

0.3

(0.1)

0.1

(0.1)

0.1

(0.0)

0.8

(0.4)

0.2

(0.1)

0.3

(0.1)

0.3

(0.1)

0.5

(0.3)

ORb

0.1

(0.1)

0.3

(0.1)

0.1

(0.1)

0.2

(0.2)

0.4

(0.2)

0.2

(0.1)

0.0

(0.0)

0.4

(0.2)

0.1

(0.1)

0.3

(0.2)

380–479 Pool 4

0.2

(0.1)

0.1

(0.0)

0.1

(0.0)

0.1

(0.1)

1.2

(0.6)

0.5

(0.2)

0.2

(0.1)

0.1

(0.0)

0.1

(0.1)

0.1

(0.0)

Pool 8

0.1

(0.1)

0.3

(0.1)

0.3

(0.1)

0.3

(0.1)

0.6

(0.2)

0.6

(0.2)

0.1

(0.0)

0.4

(0.1)

0.2

(0.1)

0.3

(0.1)

Pool 13

0.0

(0.0)

0

–c

0

–

0.1

(0.0)

0.1

(0.0)

0.1

(0.0)

0.0

(0.0)

0.0

(0.0)

0.3

(0.2)

0.0

(0.0)

Pool 26

0.0

(0.0)

0.1

(0.0)

0.1

(0.0)

0.1

(0.1)

0.2

(0.1)

0.2

(0.1)

0.0

(0.0)

0.0

(0.0)

0.1

(0.0)

0.2

(0.1)

LG

0.1

(0.0)

0.1

(0.1)

0.1

(0.1)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.1

(0.0)

0.0

(0.0)

0.0

(0.0)

0.2

(0.1)

OR

0.3

(0.2)

0.3

(0.2)

0.0

(0.0)

0.2

(0.1)

0.3

(0.1)

0.3

(0.1)

0.0

(0.0)

0.2

(0.2)

0.1

(0.1)

0.1

(0.1)

480–579 Pool 4

0.0

(0.0)

0.1

(0.1)

0.1

(0.0)

0.0

(0.0)

0.4

(0.2)

0.2

(0.1)

0.2

(0.0)

0.0

(0.0)

0.1

(0.0)

0.0

(0.0)

Pool 8

0.0

(0.0)

0.1

(0.1)

0.1

(0.1)

0.0

(0.0)

0.1

(0.0)

0.1

(0.0)

0.1

(0.0)

0.1

(0.1)

0.1

(0.0)

0.2

(0.1)

Pool 13

0.0

(0.0)

0

–

0

–

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0

–

0.0

(0.0)

0

–

0

–

Pool 26

0

–

0.0

(0.0)

0.1

(0.0)

0

–

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

LG

0.0

(0.0)

0

–

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0

–

0.0

(0.0)

0

–

0.0

(0.0)

OR

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.1

(0.1)

0.0

(0.0)

0

–

0

–

0.1

(0.1)

0.1

(0.1)

0.2

(0.1)

580–679 Pool 4

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.2

(0.1)

0.1

(0.1)

0.1

(0.0)

0.0

(0.0)

0

–

0.0

(0.0)

Pool 8

0

–

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.1

(0.0)

0.0

(0.0)

0.1

(0.0)

Pool 13

0

–

0.0

(0.0)

0

–

0

–

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0

–

0

–

0

–

Pool 26

0

–

0.0

(0.0)

0.0

(0.0)

0

–

0.0

(0.0)

0

–

0.0

(0.0)

0.0

(0.0)

0

–

0.0

(0.0)

LG

0

–

0

–

0

–

0.0

(0.0)

0

–

0

–

0.0

(0.0)

0

–

0

–

0

–

OR

0

–

0

–

0

–

0.0

(0.0)

0.1

(0.1)

0.0

(0.0)

0

–

0

–

0.1

(0.1)

0

–

a

LG = La Grange Pool. b

OR = Open River. c

– = no fish collected, no estimate
38

Table 3.6. Areawide mean catch-per-unit-effort (fish/15 min) and standard error (in parentheses) estimates by length group for common 

carp (Cyprinus carpio) collected by day electrofishing in Long Term Resource Monitoring Program study areas in 1993–2002. 

Length category

(mm)

Year

Study area 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002

Common carp (Cyprinus carpio)

280–409 Pool 4 0.5

(0.2)

0.2

(0.1)

0.1

(0.0)

0.4

(0.1)

0.1

(0.0)

0

– a

0.7

(0.2)

0.1

(0.0)

0.0

(0.0)

0.0

(0.0)

Pool 8 0.1

(0.0)

0.1

(0.0)

0.0

(0.0)

0.0

(0.0)

0

–

0.0

(0.0)

0.0

(0.0)

0

–

0.1

(0.0)

0

–

Pool 13 0.1

(0.1)

0.2

(0.1)

0.7

(0.3)

0.7

(0.3)

0.1

(0.0)

0.2

(0.1)

0.2

(0.0)

0.0

(0.0)

0.1

(0.0)

0.2

(0.1)

Pool 26 3.0

(1.2)

4.0

(0.8)

10.3

(1.7)

10.3

(1.7)

7.7

(1.5)

3.2

(0.9)

3.4

(0.7)

1.6

(0.4)

0.3

(0.1)

0.7

(0.2)

LGb 1.6

(0.4)

11.0

(1.6)

7.5

(1.3)

7.5

(1.3)

8.5

(1.5)

3.7

(0.6)

2.4

(0.3)

3.3

(0.5)

3.0

(0.4)

1.3

(0.2)

ORc 0.1

(0.1)

2.2

(0.6)

3.1

(1.2)

3.1

(1.2)

0.8

(0.3)

0.0

(0.0)

0.1

(0.1)

0.3

(0.1)

0.0

(0.0)

0.0

(0.0)

410–529 Pool 4 3.7

(0.6)

2.9

(0.4)

2.9

(0.3)

1.5

(0.3)

3.6

(0.6)

1.8

(0.3)

2.5

(0.5)

1.9

(0.3)

1.7

(0.4)

0.7

(0.1)

Pool 8 6.4

(1.4)

5.5

(0.9)

3.8

(0.6)

4.7

(0.9)

2.3

(0.4)

1.3

(0.3)

1.3

(0.3)

0.9

(0.3)

0.7

(0.2)

0.0

(0.0)

Pool 13 6.5

(1.4)

8.6

(2.0)

6.3

(1.0)

7.8

(1.3)

7.3

(1.5)

4.5

(0.8)

2.5

(0.5)

4.1

(1.0)

1.0

(0.3)

2.0

(0.6)

Pool 26 3.3

(1.0)

5.0

(1.1)

3.9

(0.6)

8.4

(1.6)

10.7

(2.0)

8.8

(2.5)

11.7

(2.0)

6.2

(1.3)

7.6

(1.6)

5.5

(1.5)

LG 1.4

(0.4)

4.8

(0.8)

3.5

(0.5)

4.4

(0.6)

6.2

(0.9)

5.0

(0.5)

3.4

(0.4)

5.4

(0.7)

6.5

(0.8)

3.6

(0.5)

OR 0.1

(0.1)

0.6

(0.4)

1.0

(0.4)

2.1

(0.8)

2.5

(0.8)

1.2

(0.2)

1.7

(0.7)

1.0

(0.3)

2.1

(1.0)

1.0

(0.4)

530–659 Pool 4 2.0

(0.4)

1.3

(0.2)

1.7 

(0.2)

1.5

(0.3)

3.2

(0.4)

3.4

(0.6)

4.7

(0.6)

4.3

(0.6)

3.3

(0.8)

1.9

(0.4)

Pool 8 2.4

(0.5)

3.1

(0.6)

2.3 

(0.3)

2.2

(0.5)

2.5

(0.5)

4.1

(0.7

2.7

(0.4)

2.2

(0.5)

1.4

(0.2)

0.1

(0.1)

Pool 13 3.5

(0.7)

5.9

(1.3)

4.1 

(0.7)

4.7

(1.1)

3.8

(0.8)

4.4

(0.9)

3.2

(0.5)

3.5

(0.8)

1.2

(0.3)

2.4

(0.7)

Pool 26 2.4

(0.8)

3.1

(0.6)

1.4 

(0.3)

2.7

(0.6)

2.0

(0.5)

1.6

(0.4)

2.8

(0.4)

1.1

(0.3)

2.3

(0.7)

1.2

(0.4)

LG 0.2

(0.1)

0.2

(0.1)

0.3 

(0.1)

0.3

(0.1)

0.3

(0.1)

0.3

(0.1)

0.2

(0.1)

0.3

(0.1)

0.3

(0.1)

0.4

(0.1)

OR 0.6

(0.3)

0.6

(0.3)

0.6 

(0.2)

1.9

(0.4)

0.5

(0.2)

0.8

(0.5)

0.5

(0.4)

2.2

(1.6)

2.2

(1.6)

0.8

(0.4)

660–839 Pool 4 0.2

(0.1)

0.2

(0.1)

0.2

(0.1)

0.1

(0.0)

0.3

(0.1)

0.3

(0.1)

0.4

(0.1)

0.4

(0.1)

0.6

(0.1)

0.2

(0.1)

Pool 8 0.1

(0.0)

0.2

(0.1)

0.2

(0.1)

0.1

(0.0)

0.2

(0.1)

0.4

(0.1)

0.2

(0.1)

0.2

(0.1)

0.1

(0.1)

0.1

(0.0)

Pool 13 0.2

(0.1)

1.0

(0.4)

0.5

(0.1)

0.4

(0.1)

0.2

(0.1)

0.3

(0.1)

0.4

(0.1)

0.4

(0.1)

0.2

(0.1)

0.3

(0.2)

Pool 26 0.1

(0.1)

0.3

(0.1)

0.1

(0.0)

0.1

(0.0)

0.1

(0.1)

0.1

(0.0)

0.2

(0.1)

0.1

(0.1)

0.1

(0.0)

0.1

(0.0)

LG 0

–

0

–

0

–

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0

–

0.0

(0.0)

0.0

(0.0)

OR 0

–

0.0

(0.0)

0.0

(0.0)

0.1

(0.1)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.2

(0.1)

0.3

(0.3)

0.0

(0.0)

a

– = no fish collected, no estimate b

LG = La Grange Pool. c

OR = Open River.
39

Table 3.7. Areawide mean catch-per–unit-effort (fish/net day) and standard error (in parentheses) estimates by length group for flathead 

catfish (Pylodictis olivaris) collected by large hoop nets in Long Term Resource Monitoring Program study areas in 1993–2002. 

Length category

(mm)

Year

Study area 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002

Flathead catfish (Pylodictis olivaris)

350–509 Pool 4 0

–a

0.0

(0.0)

0

–

0

–

0

–

0.0

(0.0)

0

–

0.0

(0.0)

0.0

(0.0)

0

–

Pool 8 0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.1

(0.0)

0.0

(0.0)

0.1

(0.1)

Pool 13 0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0

–

0.0

(0.0)

0.0

(0.0)

0.1

(0.1)

Pool 26 0.2

(0.1)

0.3

(0.1)

0.1

(0.1)

0.0

(0.0)

0.1

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.1

(0.0)

0.1

(0.0)

LGb 0.0

(0.0)

0.0

(0.0)

0.1

(0.0)

0.0

(0.0)

0.1

(0.0)

0.0

(0.0)

0.1

(0.0)

0.0

(0.0)

0.1

(0.0)

0

–

ORc 0.2

(0.1)

0.1

(0.1)

0.3

(0.1)

0.1

(0.1)

0.0

(0.0)

0.1

(0.1)

0.1

(0.1)

0.2

(0.1)

0.1

(0.1)

0.0

(0.0)

510–709 Pool 4 0.0

(0.0)

0.1

(0.0)

0.0

(0.0)

0

–

0.0

(0.0)

0

–

0

–

0.0

(0.0)

0.1

(0.0)

0.0

(0.0)

Pool 8 0.0

(0.0))

0.1

(NA)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.1

(0.0)

0.0

(0.0)

0.1

(0.1)

0.0

(0.0)

0.1

(0.1)

Pool 13 0.0

(NA

0

–

0

–

0

–

0.1

(0.1)

0

–

0

–

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

Pool 26 0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.1

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

LG 0.0

(0.0)

0

–

0.0

(0.0)

0

–

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

OR 0

–

0.0

(0.0)

0.1

(0.1)

0.1

(0.1)

0.0

(0.0)

0.0

(0.0)

0

–

0.0

(0.0)

0

–

0.0

(0.0)

710–859 Pool 4 0.0

(0.0)

0.0

(0.0)

0

–

0

–

0.1

(0.1)

0

–

0

–

0.0

(0.0)

0.0

(0.0)

0

–

Pool 8 0

–

0

–

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

Pool 13 0

–

0

–

0

–

0

–

0

–

0

–

0

–

0

–

0

–

0

–

Pool 26 0

–

0

–

0

–

0

–

0

–

0

–

0

–

0

–

0

–

0.0

(0.0)

LG 0.0

(0.0)

0

–

0

–

0.0

(0.0)

0

–

0

–

0

–

0.0

(0.0)

0

–

0

–

OR 0

–

0

–

0

–

0

–

0

–

0

–

0

–

0

–

0

–

0

–

860–1019 Pool 4 0.0

(0.0)

0

–

0

–

0

–

0.1

(0.1)

0.0

(0.0)

0

–

0.0

(0.0)

0.0

(0.0)

0

–

Pool 8 0.0

(0.0)

0

–

0

–

0.0

(0.0)

0.0

(0.0)

0

–

0

–

0

–

0

–

0

–

Pool 13 0

–

0

–

0

–

0

–

0

–

0

–

0

–

0

–

0

–

0

–

Pool 26 0

–

0

–

0

–

0

–

0

–

0

–

0

–

0

–

0

–

0

–

LG 0

–

0

–

0

–

0

–

0

–

0

–

0

–

0.0

(0.0)

0

–

0

–

OR 0

–

0

–

0

–

0

–

0

–

0

–

0

–

0

–

0.0

(0.0)

0.0

(0.0)

a

– = no fish collected, no estimate b

LG = La Grange Pool. c

OR = Open River.
40

Table 3.8. Areawide mean catch-per-unit-effort (fish/15 min) and standard error (in parentheses) estimates by length group for freshwater 

drum (Aplodinotus grunniens) collected by day electrofishing in Long Term Resource Monitoring study areas in 1993–2002. 

Length category

(mm) 

Year

Study area 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002

Freshwater drum (Aplodinotus grunniens)

200–299 Pool 4 0.3

(0.1)

0.4

(0.2)

0.2

(0.1)

1.0

(0.5)

0.4

(0.1)

0.2

(0.1)

0.3

(0.1)

0.2

(0.1)

0.3

(0.1)

0.1

(0.0)

Pool 8 0.0

(0.0)

0.2

(0.1)

0.1

(0.1)

0.1

(0.0)

0.1

(0.1)

0.0

(0.0)

0.1

(0.1)

0.2

(0.1)

0.2

(0.1)

0.0

(0.0)

Pool 13 0.1

(0.1)

0

–a

0.1

(0.0)

0.3

(0.1)

0.3

(0.1)

0.1

(0.0)

0.2

(0.2)

0.3

(0.1)

0.0

(0.0)

0.1

(0.1)

Pool 26 0.4

(0.2)

0.3

(0.1)

2.2

(1.1)

1.2

(0.7)

0.1

(0.1)

1.2

(0.5)

1.7

(0.6)

0.2

(0.1)

0.6

(0.3)

0.3

(0.1)

LGb 0.6

(0.4)

0.1

(0.1)

0.9

(0.2)

0.6

(0.2)

1.4

(0.1)

0.8

(0.2)

0.7

(0.3)

0.7

(0.2)

0.3

(0.1)

0.2

(0.1)

ORc 0.1

(0.1)

0.9

(0.4)

0.4

(0.3)

2.3

(1.1)

1.0

(0.6)

0.5

(0.3)

0.4

(0.2)

0.5

(0.3)

0.4

(0.4)

0

–

300–379 Pool 4 1.3

(0.2)

0.5

(0.2)

0.3

(0.1)

0.5

(0.1)

0.3

(0.1)

0.8

(0.2)

1.0

(0.2)

0.6

(0.2)

0.4

(0.1)

0.2

(0.1)

Pool 8 0.1

(0.0)

0.1

(0.0)

0.0

(0.0)

0.1

(0.0)

0.1

(0.0)

0.1

(0.1)

0.1

(0.0)

0.0

(0.0)

0.2

(0.1)

0.0

(0.0)

Pool 13 0.3

(0.2)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.1

(0.0)

0.3

(0.1)

0.1

(0.0)

0.2

(0.1)

0.1

(0.1)

0.1

(0.1)

Pool 26 0.6

(0.2)

0.3

(0.1)

0.3

(0.2)

0.6

(0.3)

0.2

(0.1)

0.4

(0.1)

1.2

(0.6)

0.1

(0.1)

0.3

(0.1)

0.1

(0.1)

LG 0.1

(0.1)

0.2

(0.1)

0.3

(0.1)

0.5

(0.1)

0.4

(0.1)

0.7

(0.2)

0.4

(0.1)

0.3

(0.1)

0.2

(0.1)

0.2

(0.1)

OR 0.4

(0.3)

0.8

(0.3)

0.5

(0.3)

0.4

(0.2)

0.9

(0.3)

0.3

(0.2)

0.6

(0.4)

0.6

(0.4)

0.1

(0.1)

0.0

(0.0)

380–509 Pool 4 0.3

(0.1)

0.1

(0.0)

0.2

(0.1)

0.0

(0.0)

0.2

(0.1)

0.1

(0.0)

0.2

(0.1)

0.1

(0.1)

0.1

(0.0)

0.3

(0.2)

Pool 8 0.2

(0.0)

0.1

(0.0)

0.1

(0.1)

0.1

(0.0)

0.1

(0.0)

0.6

(0.3)

0.1

(0.0)

0.1

(0.0)

0.1

(0.1)

0.0

(0.0)

Pool 13 0.2

(0.1)

0.1

(0.1)

0.1

(0.1)

0.1

(0.0)

0.0

(0.0)

0.1

(0.0)

0.2

(0.1)

0.3

(0.2)

0.0

(0.0)

0.1

(0.0)

Pool 26 0.3

(0.2)

0.2

(0.1)

0.3

(0.2)

0.5

(0.2)

0.2

(0.1)

0.3

(0.1)

0.4

(0.2)

0.1

(0.1)

0.5

(0.3)

0.2

(0.1)

LG 0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.1

(0.1)

0.2

(0.0)

0.1

(0.0)

0.1

(0.0)

0.1

(0.0)

0.2

(0.1)

OR 0.1

(0.1)

0.1

(0.1)

0.0

(0.0)

0.0

(0.0)

0.3

(0.1)

0

–

0.3

(0.2)

0.3

(0.2)

0.0

(0.0)

0

–

510–629 Pool 4 0.0

(0.0)

0.0

(0.0)

0

–

0

–

0

–

0

–

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

Pool 8 0

–

0.0

(0.0)

0

–

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0

–

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

Pool 13 0.0

(0.0)

0

–

0

–

0

–

0

–

0.0

(0.0)

0

–

0

–

0.0

(0.0)

0.0

(0.0)

Pool 26 0.1

(0.1)

0.0

(0.0)

0.0

(0.0)

0

–

0.0

(0.0)

0.0

(0.0)

0

–

0

–

0.0

(0.0)

0

–

LG 0

–

0

–

0

–

0

–

0.0

(0.0)

0

–

0

–

0

–

0

–

0.0

(0.0)

OR 0

–

0

–

0

–

0

–

0.1

(0.1)

0

–

0.2

(0.1)

0.2

(0.2)

0

–

0.0

(0.0)

a

– = no fish collected, no estimate b

LG = La Grange Pool. c

OR = Open River.
41

Table 3.9. Areawide mean catch-per-unit-effort (fish/15 min) and standard error (in parentheses) estimates by length group for 

largemouth bass (Micropterus salmoides) collected by day electrofishing in Long Term Resource Monitoring Program study areas in 

1993–2002. 

Length category

(mm)

Year

Study area 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002

Largemouth bass (Micropterus salmoides)

200–274 Pool 4 0.0

(0.0)

0.0

(0.0)

0.1

(0.1)

0.2

(0.1)

0.3

(0.1)

0.2

(0.1)

0.8

(0.2)

0.5

(0.1)

0.2

(0.1)

0.5

(0.1)

Pool 8 0.3

(0.2)

0.2

(0.1)

0.6

(0.2)

1.9

(1.3)

0.5

(0.1)

0.5

(0.1)

1.3

(0.3)

0.8

(0.1)

0.4

(0.1)

0.1

(0.1)

Pool 13 1.0

(0.2)

0.2

(0.1)

1.0

(0.3)

1.6

(0.3)

1.1

(0.2)

0.7

(0.2)

1.8

(0.5)

1.3

(0.5)

0.3

(0.1)

0.8

(0.3)

Pool 26 0.0

(0.0)

0.5

(0.1)

0.2

(0.1)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.2

(0.2)

0.0

(0.0)

1.0

(0.3)

0.3

(0.1)

LGa 0.0

(0.0)

0.3

(0.1)

0.7

(0.1)

0.4

(0.1)

0.5

(0.1)

0.8

(0.2)

2.7

(0.7)

0.6

(0.1)

0.3

(0.1)

0.4

(0.1)

ORb 0

–c

0

–

0

–

0.0

(0.0)

0.0

(0.0)

0

–

0

–

0

–

0.0

(0.0)

0.0

(0.0)

275–349 Pool 4 0.2

(0.1)

0.1

(0.1)

0.0

(0.0)

0.1

(0.1)

0.2

(0.1)

0.1

(0.0)

0.5

(0.2)

0.5

(0.1)

0.3

(0.1)

0.2

(0.1)

Pool 8 0.1

(0.1)

0.2

(0.0)

0.2

(0.1)

1.0

(0.5)

0.5

(0.1)

0.3

(0.1)

0.6

(0.1)

1.0

(0.2)

1.0

(0.2)

0.1

(0.0)

Pool 13 0.8

(0.2)

0.6

(0.1)

0.3

(0.1)

0.8

(0.2)

1.0

(0.2)

1.0

(0.2)

1.4

(0.3)

1.5

(0.5)

0.5

(0.2)

0.2

(0.1)

Pool 26 0.0

(0.0)

0.1

(0.1)

0.3

(0.1)

0.0

(0.0)

0.1

(0.0)

0.0

(0.0)

0.0

(0.0)

0.1

(0.0)

0.2

(0.1)

0

–

LG 0.1

(0.1)

0.7

(0.1)

0.3

(0.1)

0.4

(0.1)

0.3

(0.1)

0.7

(0.1)

0.9

(0.2)

0.9

(0.2)

0.3

(0.1)

0.1

(0.0)

OR 0

–

0

–

0

–

0

–

0.0

(0.0)

0

–

0

–

0

–

0

–

0

–

350–424 Pool 4 0.2

(0.1)

0.2

(0.1)

0.2

(0.1)

0.1

(0.1)

0.3

(0.1)

0.1

(0.0)

0.2

(0.1)

0.2

(0.1)

0.2

(0.1)

0.2

(0.1)

Pool 8 0.2

(0.1)

0.1

(0.0)

0.1

(0.1)

0.3

(0.1)

0.2

(0.1)

0.3

(0.1)

0.4

(0.2)

0.4

(0.1)

0.6

(0.1)

0.0

(0.0)

Pool 13 0.5

(0.1)

0.6

(0.2)

0.4

(0.1)

0.6

(0.2)

0.7

(0.1)

0.5

(0.1)

0.9

(0.3)

0.6

(0.2)

0.4

(0.1)

0.7

(0.2)

Pool 26 0.0

(0.0)

0.1

(0.1)

0.1

(0.0)

0.0

(0.0)

0.1

(0.0)

0

–

0.0

(0.0)

0.0

(0.0)

0.1

(0.1)

0.0

(0.0)

LG 0.0

(0.0)

1.1

(0.2)

0.5

(0.1)

0.3

(0.1)

0.3

(0.1)

0.5

(0.1)

0.4

(0.1)

0.4

(0.1)

0.2

(0.1)

0.2

(0.1)

OR 0

–

0

–

0.0

(0.0)

0

–

0.0

(0.0)

0

–

0

–

0

–

0

–

0

–

425–499 Pool 4 0.0

(0.0)

0

–

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0

–

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

Pool 8 0.0

(0.0)

0

–

0.0

(0.0)

0.1

(0.0)

0.0

(0.0)

0.0

(0.0)

0.1

(0.0)

0

–

0.0

(0.0)

0

–

Pool 13 0.0

(0.0)

0.1

(0.1)

0.0

(0.0)

0.1

(0.0)

0.1

(0.1)

0.0

(0.0)

0.1

(0.1)

0.2

(0.1)

0.1

(0.1)

0.0

(0.0)

Pool 26 0.0

(0.0)

0

–

0.0

(0.0)

0.0

(0.0)

0.1

(0.0)

0.0

(0.0)

0

–

0

–

0

–

0

–

LG 0

–

0.1

(0.0)

0.1

(0.0)

0.1

(0.0)

0.1

(0.0)

0.1

(0.1)

0.1

(0.0)

0.1

(0.0)

0.0

(0.0)

0.0

(0.0)

OR 0

–

0

–

0

–

0

–

0

–

0

–

0

–

0

–

0

–

0

–

a

LG = La Grange Pool. b

OR = Open River. c

– = no fish collected, no estimate
42

Table 3.10. Areawide mean catch-per-unit-effort (fish/15 min) and standard error (in parentheses) estimates by length group for sauger 

(Sander canadensis) collected by day electrofishing in Long Term Resource Monitoring Program study areas in 1993–2002. 

Length category

(mm)

Year

Study area 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002

Sauger (Sander canadensis)

200–269 Pool 4 0.1

(0.0)

0.0

(0.0)

0.3

(0.1)

0.1

(0.1)

0.3

(0.1)

0.3

(0.1)

0.9

(0.2)

0.2

(0.1)

0.0

(0.0)

0.3

(0.1)

Pool 8 0.4

(0.1)

0.2

(0.1)

0.3

(0.1)

0.3

(0.1)

0.1

(0.1)

0.9

(0.1)

0.5

(0.1)

0.5

(0.1)

0.0

(0.0)

0

–a

Pool 13 0.4

(0.2)

0.2

(0.1)

0.4

(0.2)

0.1

(0.0)

0.2

(0.1)

0.6

(0.2)

0.5

(0.1)

0.4

(0.1)

0.1

(0.0)

0.3

(0.1)

Pool 26 0

–

0.8

(0.2)

0.1

(0.1)

0.0

(0.0)

0.3

(0.1)

0.0

(0.0)

0.2

(0.1)

0.0

(0.0)

0.1

(0.1)

0.0

(0.0)

LGb 0.1

(0.1)

0.8

(0.2)

0.1

(0.0)

0.2

(0.1)

0.3

(0.1)

0.3

(0.1)

0.1

(0.0)

0.1

(0.1)

0.0

(0.0)

0.0

(0.0)

ORc 0

–

0.1

(0.1)

0.1

(0.1)

0

–

0

–

0.1

(0.1)

0

–

0

–

0.0

(0.0)

0.1

(0.1)

270–339 Pool 4 0.1

(0.0)

0.0

(0.0)

0.0

(0.0)

0.1

(0.1)

0.2

(0.1)

0.1

(0.0)

0.3

(0.1)

0.4

(0.1)

0.1

(0.0)

0.1

(0.0)

Pool 8 0.0

(0.0)

0.2

(0.1)

0.1

(0.0)

0.3

(0.1)

0.2

(0.0)

0.2

(0.0)

0.2

(0.0)

0.4

(0.1)

0.2

(0.1)

0

–

Pool 13 0.1

(0.1)

0.1

(0.1)

0.0

(0.0)

0.3

(0.1)

0.2

(0.1)

0.3

(0.1)

0.2

(0.1)

0.3

(0.1)

0.1

(0.1)

0.0

(0.0)

Pool 26 0

–

0.1

(0.0)

0.1

(0.1)

0.1

(0.0)

0

–

0.1

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

LG 0

–

0.1

(0.0)

0.1

(0.1)

0.0

(0.0)

0.1

(0.0)

0.0

(0.0)

0.0

(0.0)

0

–

0

–

0.0

(0.0)

OR 0

–

0.0

(0.0)

0.2

(0.1)

0.1

(0.1)

0

–

0

–

0.1

(0.1)

0.1

(0.1)

0

–

0

–

340–409 Pool 4 0.1

(0.0)

0.0

(0.0)

0.0

(0.0)

0.1

(0.0)

0.0

(0.0)

0.1

(0.0)

0.0

(0.0)

0

–

0.0

(0.0)

0.0

(0.0)

Pool 8 0

–

0

–

0

–

0

–

0

–

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.1

(0.0)

0

–

Pool 13 0

–

0

–

0.0

(0.0)

0.1

(0.0)

0.1

(0.0)

0.1

(0.0)

0

–

0.0

(0.0)

0.1

(0.1)

0

–

Pool 26 0

–

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0

–

0

–

0

–

LG 0

–

0

–

0.1

(0.0)

0.0

(0.0)

0

–

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

OR 0

–

0

–

0.1

(0.1)

0

–

0

–

0.0

(0.0)

0

–

0.1

(0.1)

0.1

(0.1)

0

–

410–479 Pool 4 0.1

(0.1)

0

–

0

–

0.0

(0.0) 

0.0

(0.0)

0.0

(0.0)

0

–

0

–

0.0

(0.0)

0.0

(0.0)

Pool 8 0

–

0

–

0.0

(0.0)

0

–

0

–

0

–

0

–

0

–

0

–

0

–

Pool 13 0

–

0

–

0

–

0.0

(0.0)

0

–

0

–

0.0

(0.0)

0

–

0

–

0

–

Pool 26 0

–

0.0

(0.0)

0

–

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0

–

0

–

0

–

0.0

(0.0)

LG 0

–

0

–

0

–

0.0

(0.0)

0

–

0.1

(0.0)

0

–

0.0

(0.0)

0

–

0.0

(0.0)

OR 0

–

0

–

0

–

0.0

(0.0)

0

–

0.2

(0.1)

0

–

0

–

0

–

0

–

a

– = no fish collected, no estimate b

LG = La Grange Pool. c

OR = Open River.
43

Table 3.11. Areawide mean catch-per-unit-effort (fish/net day) and standard error (in parentheses) estimates by length group for 

smallmouth buffalo (Ictiobus bubalus) collected by large hoop nets in Long Term Resource Monitoring Program study areas in 1993–2002. 

Length category

(mm)

Year

Study area 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002

Smallmouth buffalo (Ictiobus bubalus)

280–389 Pool 4 0

–a

0

–

0

–

0.2

(0.1)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0

–

Pool 8 0.1

(0.0)

0

–

0.1

(0.0)

0.6

(0.2)

0.6

(0.2)

0

–

0.0

(0.0)

0.0

(0.0)

0

–

0

–

Pool 13 0.0

(0.0)

0.1

(0.0)

0.3

(0.1)

0.5

(0.2)

3.0

(0.8)

0.5

(0.1)

0.6

(0.2)

0.6

(0.2)

0.4

(0.2)

0.0

(0.0)

Pool 26 0.4

(0.2)

0.2

(0.1)

2.1

(0.6)

5.3

(1.8)

5.0

(1.4)

1.5

(0.4)

1.2

(0.4)

1.2

(0.4)

0.7

(0.3)

0.4

(0.1)

LGb 2.5

(1.3)

0.3

(0.1)

1.3

(0.3)

0.9

(0.2)

2.8

(0.9)

3.5

(0.7)

1.8

(0.5)

1.8

(0.5)

5.6

(1.7)

2.4

(0.8)

ORc 0

–

0

–

0.0

(0.0)

2.5

(2.2)

1.0

(0.5)

1.3

(0.7)

0.1

(0.1)

0.1

(0.1)

0

–

0.1

(0.0)

390–499 Pool 4 0.6

(0.3)

0.3

(0.1)

0.5

(0.2)

0.2

(0.1)

0.4

(0.2)

0.9

(0.3)

0.5

(0.2)

0.9

(0.3)

0.6

(0.2)

0.1

(0.1)

Pool 8 0.5

(0.1)

0.1

(0.1)

0.3

(0.1)

0.3

(0.1)

1.1

(0.3)

0.1

(0.1)

0.1

(0.1)

0.0

(0.0)

0.1

(0.0)

0

–

Pool 13 0.0

(0.0)

0.3

(0.1)

0.3

(0.1)

0.1

(0.0)

0.9

(0.5)

0.2

(0.1)

0.6

(0.2)

0.4

(0.1)

0.6

(0.3)

0.1

(0.0)

Pool 26 1.0

(0.7)

1.1

(0.3)

1.1

(0.3)

1.0

(0.3)

1.3

(0.4)

0.7

(0.2)

1.0

(0.2)

1.9

(0.4)

1.2

(0.2)

0.9

(0.2)

LG 1.1

(0.5)

0.8

(0.2)

0.8

(0.2)

0.4

(0.2)

0.9

(0.3)

2.4

(0.6)

0.9

(0.2)

2.3

(0.6)

4.0

(1.0)

4.1

(1.2)

OR 0.1

(0.1)

0.0

(0.0)

0.7

(0.3)

1.2

(0.7)

0.8

(0.3)

1.4

(0.4)

0.9

(0.3)

1.7

(0.5)

0.6

(0.3)

0.6

(0.3)

500–609 Pool 4 0.1

(0.1)

0.1

(0.1)

0.3

(0.1)

0.1

(0.0)

0.4

(0.1)

0.9

(0.3)

0.8

(0.2)

1.2

(0.4)

0.9

(0.2)

0.5

(0.2)

Pool 8 0.2

(0.1)

0.1

(0.1)

0.1

(0.0)

0.2

(0.1)

0.6

(0.2)

0.1

(0.0)

0.1

(0.0)

0.2

(0.1)

0.2

(0.1)

0

–

Pool 13 0

–

0.1

(0.0)

0.1

(0.0)

0.0

(0.0)

0.2

(0.1)

0.1

(0.0)

0.1

(0.1)

0.1

(0.0)

0.1

(0.1)

0.0

(0.0)

Pool 26 0.3

(0.3)

0.2

(0.1)

0.3

(0.1)

0.5

(0.2)

0.2

(0.1)

0.2

(0.1)

0.3

(0.1)

0.2

(0.1)

0.1

(0.0)

0.3

(0.1)

LG 0.0

(0.0)

0

–

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.2

(0.1)

0.0

(0.0)

0.1

(0.0)

0.1

(0.1)

0.0

(0.0)

OR 0.1

(0.1)

0.1

(0.0)

0.6

(0.3)

0.2

(0.1)

0.3

(0.1)

0.4

(0.2)

0.6

(0.3)

0.9

(0.3)

0.0

(0.0)

0.1

(0.1)

610–729 Pool 4 0

–

0.0

(0.0)

0.0

(0.0)

0

–

0.1

(0.1)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0

–

0.1

(0.0)

Pool 8 0.1

(0.1)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0

–

Pool 13 0

–

0

–

0.0

(0.0)

0

–

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0

–

0

–

0

–

Pool 26 0

–

0.0

(0.0)

0.0

(0.0)

0

–

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0

–

0

–

0.0

(0.0)

LG 0

–

0

–

0

–

0

–

0

–

0

–

0

–

0

–

0

–

0

–

OR 0.2

(0.2)

0.0

(0.0)

0.0

(0.0)

0

–

0.0

(0.0)

0.0

(0.0)

0.1

(0.1)

0.0

(0.0)

0

–

0.0

(0.0)

a

– = no fish collected, no estimate b

LG = La Grange Pool. c

OR = Open River.
44

Table 3.12. Areawide mean catch-per-unit-effort (fish/15 min) and standard error (in parentheses) estimates by length group for white 

bass (Morone chrysops) collected by day electrofishing in Long Term Resource Monitoring Program study areas in 1993–2002. 

Length category

(mm)

Year

Study area 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002

White bass (Morone chrysops)

150–229 Pool 4 0.2

(0.1)

0.0

(0.0)

1.6

(0.8)

0.0

(0.0)

0.1

(0.0)

0.3

(0.2)

0.5

(0.2)

0.1

(0.0)

0.1

(0.0)

0.1

(0.1)

Pool 8 0.0

(0.0)

0.0

(0.0)

0.2

(0.1)

0.2

(0.1)

0.0

(0.0)

0.4

(0.3)

0.3

(0.1)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

Pool 13 0.2

(0.1)

0.7

(0.7)

0.5

(0.2)

0.1

(0.1)

0.1

(0.0)

0.2

(0.1)

0.3

(0.1)

0.4

(0.1)

0.4

(0.1)

0.1

(0.1)

Pool 26 6.9

(2.2)

3.0

(0.8)

0.4

(0.1)

0.1

(0.1)

0.8

(0.2)

0.7

(0.2)

0.5

(0.1)

0.1

(0.0)

0.1

(0.0)

0.2

(0.1)

LGa 0.8

(0.7)

4.4

(0.9)

0.8

(0.4)

1.7

(0.4)

0.7

(0.2)

2.5

(0.5)

0.5

(0.2)

1.2

(0.6)

1.2

(0.6)

0.4

(0.1)

ORb 2.5

(0.9)

1.5

(0.9)

0.4

(0.3)

0.4

(0.3)

0.3

(0.1)

0.4

(0.2)

0

–c

0.7

(0.3)

0.7

(0.3)

0.1

(0.1)

230–299 Pool 4 0.2

(0.1)

0.0

(0.0)

0.1

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.3

(0.2)

0.3

(0.1)

0.2

(0.0)

0.0

(0.0)

Pool 8 0.1

(0.0)

0.0

(0.0)

0.0

(0.0)

0.1

(0.0)

0

–

0.0

(0.0)

0.0

(0.0)

0.1

(0.0)

0.0

(0.0)

0

–

Pool 13 0.1

(0.1)

0.2

(0.1)

0.1

(0.1)

0.2

(0.1)

0.1

(0.1)

0.2

(0.1)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.3

(0.1)

Pool 26 0.0

(0.0)

0.3

(0.1)

0.9

(0.3)

0.1

(0.0)

0.0

(0.0)

0.4

(0.2)

0.6

(0.1)

0.1

(0.0)

0.1

(0.1)

0.0

(0.0)

LG 0.2

(0.1)

0.2

(0.1)

0.4

(0.2)

0.6

(0.2)

0.8

(0.2)

1.1

(0.3)

2.0

(0.6)

0.3

(0.1)

0.2

(0.1)

0.1

(0.1)

OR 0.3

(0.2)

0.4

(0.2)

0.6

(0.3)

0.2

(0.2)

0.1

(0.1)

0.1

(0.1)

0.1

(0.1)

0.0

(0.0)

0

–

0.1

(0.1)

300–379 Pool 4 0.5

(0.2)

0.1

(0.0)

0.1

(0.0)

0.0

(0.0)

0.4

(0.1)

0.3

(0.1)

0.3

(0.1)

0.3

(0.1)

0.7

(0.1)

0.3

(0.1)

Pool 8 0.1

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.3

(0.1)

0

–

0.0

(0.0)

0.1

(0.1)

0.0

(0.0)

Pool 13 0

–

0.1

(0.1)

0.0

(0.0)

0.1

(0.1)

0.1

(0.1)

0.0

(0.0)

0.1

(0.0)

0.2

(0.1)

0.0

(0.0)

0.1

(0.0)

Pool 26 0

–

0.1

(0.0)

0.0

(0.0)

0.3

(0.1)

0.2

(0.1)

0.2

(0.1)

0.4

(0.1)

0.2

(0.1)

0.1

(0.0)

0.2

(0.0)

LG 0.1

(0.1)

0.1

(0.1)

0.1

(0.1)

0.5

(0.1)

0.3

(0.1)

1.2

(0.4)

0.5

(0.1)

0.4

(0.1)

0.2

(0.1)

0.3

(0.1)

OR 0

–

0.1

(0.1)

0.0

(0.0)

0.3

(0.1)

0.2

(0.1)

0.0

(0.0)

0.2

(0.1)

0.1

(0.1)

0.0

(0.0)

0.0

(0.0)

380–459 Pool 4 0.0

(0.0)

0.0

(0.0)

0.1

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.1

(0.1)

0.1

(0.1)

0.1

(0.0)

0.2

(0.1)

Pool 8 0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0

–

0

–

0

–

0

–

0.0

(0.0)

0

–

0

–

Pool 13 0

–

0.1

(0.0)

0

–

0.0

(0.0)

0.0

(0.0)

0

–

0.0

(0.0)

0.0

(0.0)

0

–

0

–

Pool 26 0

–

0.0

(0.0)

0.0

(0.0)

0

–

0.0

(0.0)

0.1

(0.0)

0.0

(0.0)

0.0

(0.0)

0.1

(0.0)

0.1

(0.0)

LG 0

–

0

–

0

–

0.0

(0.0)

0

–

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0

–

OR 0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0

–

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0

–

a

LG = La Grange Pool. b

OR = Open River. c

– = no fish collected, no estimate
45

Table 3.13. Areawide mean catch-per-unit-effort (fish/net day) and standard error (in parentheses) estimates by length group for white 

crappie (Pomoxis annularis) collected by fyke nets in Long Term Resource Monitoring Program study areas in 1993–2002. 

Length category

(mm)

Year

Study area 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002

White Crappie (Pomoxis annularis)

130–199 Pool 4 0

–a

0

–

0.1

(0.1)

0

–

0.5

(0.4)

0

–

0.1

(0.1)

0.1

(0.1)

0.3

(0.2)

0

–

Pool 8 0.3

(0.2)

0.0

(0.0)

0.1

(0.0)

0.1

(0.1)

0.1

(0.1)

0.0

(0.0)

0.2

(0.1)

0

–

0.1

(0.1)

0.0

(0.0)

Pool 13 0.5

(0.2)

0.0

(0.0)

1.4

(0.4)

1.1

(0.3)

0.8

(0.4)

0.6

(0.2)

0.9

(0.4)

2.7

(1.2)

4.8

(1.8)

3.0

(1.2)

Pool 26 0.2

(0.1)

0.4

(0.2)

0.3

(0.2)

0.0

(0.0)

0.0

(0.0)

0.1

(0.0)

0.0

(0.0)

0.2

(0.1)

1.3

(0.6)

0.4

(0.2)

LGb 0.1

(0.1)

5.0

(1.5)

2.7

(1.2)

1.3

(0.4)

3.9

(0.9)

1.6

(0.9)

2.3

(0.9)

0.6

(0.2)

0.5

(0.2)

1.2

(0.4)

ORc 0

–

0

–

0

–

0

–

0

–

0

–

0.0

(0.0)

0

–

0

–

0

–

200–249 Pool 4 0.1

(0.1)

0

–

0.2

(0.1)

0

–

0.2

(0.1)

0

–

0

–

0.2

(0.1)

0.1

(0.1)

0

–

Pool 8 0.2

(0.1)

0.1

(0.1)

0.1

(0.1)

0.1

(0.1)

0.0

(0.0)

0.1

(0.1)

0.4

(0.3)

0.1

(0.1)

0.0

(0.0)

0.0

(0.0)

Pool 13 1.6

(0.6)

0.3

(0.1)

0.1

(0.1)

1.2

(0.6)

0.5

(0.2)

0.3

(0.1)

1.8

(1.5)

0.4

(0.2)

1.2

(0.5)

1.8

(0.8)

Pool 26 0.3

(0.1)

0.3

(0.1)

0.2

(0.1)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.0

(0.0)

0.6

(0.2)

0.3

(0.1)

LG 0.2

(0.1)

0.7

(0.3)

5.8

(2.0)

1.1

(0.4)

1.0

(0.4)

2.1

(0.1)

2.2

(0.7)

1.6

(0.6)

0.6

(0.3)

0.7

(0.2)

OR 0

–

0

–

0

–

0

–

0

–

0

–

0

–

0

–

0

–

0

–

250–299 Pool 4 0.1

(0.1)

0

–

0.1

(0.1)

0

–

0

–

0.3

(0.2)

0

–

0.3

(0.2)

0

–

0

–

Pool 8 0.1

(0.1)

0.2

(0.1)

0.0

(0.0)

0

–

0.1

(0.0)

0.1

(0.1)

0.1

(0.0)

0

–

0.1

(0.1)

0

–

Pool 13 0.5

(0.2)

1.0

(0.5)

0.6

(0.3)

0.2

(0.1)

0.2

(0.1)

0.5

(0.2)

0.7

(0.3)

1.1

(0.5)

0.8

(0.3)

1.3

(0.5)

Pool 26 0.0

(0.0)

0.1

(0.0)

0.1

(0.0)

0.0

(0.0)

0.0

(0.0)

0

–

0

–

0.0

(0.0)

0.4

(0.2)

0.1

(0.1)

LG 0.1

(0.1)

0.1

(0.0)

0.8

(0.3)

0.8

(0.3)

0.6

(0.2)

0.8

(0.2)

0.7

(0.3)

0.4

(0.2)

0.1

(0.0)

0.4

(0.1)

OR 0

–

0.0

(0.0)

0

–

0

–

0

–

0

–

0

–

0

–

0

–

0

–

300–379 Pool 4 0

–

0.1

(0.1)

0

–

0

–

0.0

(0.0)

0.1

(0.1)

0.1

(0.1)

0.1

(0.1)

0.1

(0.1)

0

–

Pool 8 0.1

(0.1)

0.0

(0.0)

0.1

(0.0)

0.1

(0.0)

0

–

0.1

(0.0)

0.1

(0.1)

0

–

0.0

(0.0)

0

–

Pool 13 0.1

(0.1)

0.3

(0.1)

0.5

(0.3)

0.1

(0.1)

0.1

(0.1)

0.1

(0.1)

0

–

0.1

(0.1)

0.1

(0.1)

0.4

(0.2)

Pool 26 0

–

0.0

(0.0)

0.1

(0.1)

0

–

0

–

0

–

0

–

0

–

0.1

(0.1)

0

–

LG 0

–

0.1

(0.1)

0.3

(0.1)

0.0

(0.0)

0.0

(0.0)

0.1

(0.1)

0.0

(0.0)

0.1

(0.0)

0

–

0.1

(0.1)

OR 0

–

0

–

0

–

0

–

0

–

0

–

0

–

0

–

0

–

0

–

a

– = no fish collected, no estimate b

LG = La Grange Pool. c

OR = Open River.
46

Chapter 4. Temporal and Spatial 

Trends in Length‐weight 

Relationships

Introduction

Length‐weight relationships of fish 

populations are helpful for determining body 

condition or general “well‐being” and can be 

a robust predictor of growth (Anderson and 

Neumann 1996). When length and weight 

data for a fish population are logarithmically 

transformed, the relation between length and 

weight is linear and can be viewed as the 

population rate of gain on the log scale (i.e., 

increase in log10 weight per unit increase in log10

length; hereafter referred to as rate of gain). 

Populations with a high rate of gain are adding 

weight at a faster rate than populations with a low 

rate of gain. Length‐weight regression parameters 

can be used to estimate the weight of fish at a 

given length for the population. Length‐weight 

regression provides a means for comparing fish 

plumpness or body condition among populations 

while controlling for length. Increased predicted 

weight for a population at a given length 

suggests increased fat reserves are available 

for somatic growth and gonad development. 

Factors affecting population length‐weight 

relationships include physiological stress, 

competition for resources, habitat suitability, 

and prey availability. This chapter compares 

length‐weight relationships among study areas 

and study years 1993–2002 for the Long Term 

Resource Monitoring Program (LTRMP). Spatial 

differences in length‐weight relationships may 

provide insight into mechanisms responsible for 

variability in population parameters among study 

areas. Temporal differences in length‐weight 

relationships may provide insight into how 

environmental conditions (e.g., water levels, 

climate) can affect fish growth and health. 

Methods

Total length (nearest millimeter) and weight 

(nearest gram) data were collected for individual 

black crappie (Pomoxis nigromaculatus), channel 

catfish (Ictalurus punctatus), common carp 

(Cyprinus carpio), highfin carpsucker (Carpiodes 

velifer), sauger (Sander canadensis), and walleye 

(Sander vitreus) in third period (September 16–

October 31) LTRMP fish collections. Annually, 

weight data were screened for outliers based 

on the percent deviation from LTRMP derived 

length‐weight regression models. Weight data 

were considered outliers if the observed weight 

differed from predicted weight (calculated using 

length‐weight regression models) by <‐70% or 

>150% for fish ≤125 mm, <‐60% or >120% for 

fish from 126 to 249 mm, and <‐50% or >100% 

for fish ≥250 mm. Weight data flagged as outliers 

were reviewed by field collection staff and 

removed if deemed unreliable. Length‐weight 

regression analyses were limited to fish of stock 

length through quality length (see Anderson and 

Neumann 1996 for length designations). Highfin 

carpsucker data were excluded from analyses 

because they were not collected in all study areas 

or years. There were no stock length to quality 

length walleye collected from the Open River 

study area (Open River; river mile 29–80) in 

1993–2002, so Open River was excluded from 

analysis for walleye. Length and weight data 

were log10 transformed before analyses to provide 

a linear relation between fish length and weight. 

Field‐collected weight data inherently have 

error associated with them that affect the ability 

to precisely define length‐weight relationships 

(Gutreuter and Krzoska 1994). Error associated 

with field‐collected weight measurements 

reduces the likelihood that significant trends 

in rate of gain will be detected, but should not 

increase the likelihood of Type I error.

For each species, linear regression was 

used to describe the relation between log10

weight (dependent variable) and log10 length 

(independent variable) for each year and study 

area. Regressions were tested for parallel 

slopes and equal Y‐intercepts using analysis 

of variance (GLM procedure; SAS Institute 

1999). To determine which years and study 

areas were significantly different, the slope from 

individual year and study area length‐weight 

regressions were tested for significant difference 

against a composite length‐weight regression 

(i.e., length‐weight regression constructed from 

all years and study areas) using a t‐test. Year 

regression slopes were considered significantly 
47

different than the composite regression slope at 

P < 0.005 (Bonferroni corrected for N = 10 year 

comparisons), and study area regression line 

slopes were considered significantly different 

than the composite regression line slope at 

P < 0.008 (Bonferroni corrected for N = six study 

areas).

For each species, length‐weight regressions 

were calculated for each study area and year. 

These regressions were used to predict weight 

upon entering stock length (PW1) and upon 

leaving quality length (PW2), using length 

designations from Anderson and Neumann 

(1996). Inferential statistics were not used to test 

the significance of differences among predicted 

weights—they are meant to serve as descriptive 

guides for interpreting rate of gain results.

Results

The rate of gain was significantly different 

among areas (test for parallel slopes, P < 0.05, 

Table 4.1) for all species tested (i.e., black 

crappie, channel catfish, common carp, sauger, 

and walleye). In La Grange Pool, the rate of gain 

for black crappie, channel catfish, and sauger was 

significantly higher (t‐tests, P < 0.005) than the 

overall rate of gain trend (Table 4.2). La Grange 

Pool was the only study area to contain 

populations with a rate of gain significantly 

higher than the overall rate of gain trend. High 

rate of gain for black crappie, channel catfish, 

and sauger in La Grange Pool was caused by 

a decreased plumpness of small fish and an 

increased plumpness of large fish (predicted 

weights, Table 4.2). Pools 4, 13, and 26, and 

La Grange Pool contained at least one species 

exhibiting a rate of gain significantly lower than 

the overall rate of gain trend.

The rate of gain was significantly different 

among years for black crappie, channel catfish, 

common carp, and walleye (test for parallel 

slopes, P < 0.05, Table 4.1), but was not 

significantly different among years for sauger 

(test for parallel slopes, P = 0.0791, Table 4.1). 

In 1993, the rate of gain for black crappie and 

common carp was significantly lower (t‐tests, 

P < 0.005) than the overall rate of gain trend 

(Table 4.3). Low rate of gain for black crappie 

and common carp in 1993 was caused by an 

increased plumpness of small fish (predicted 

weights, Table 4.3). In 1997, the rate of gain for 

black crappie and common carp was significantly 

higher (t‐test, P < 0.005) than the overall rate of 

gain trend (Table 4.3). High rate of gain for black 

crappie and common carp in 1997 was caused by 

an increased plumpness of large fish (predicted 

weights, Table 4.3). In 1993, channel catfish 

exhibited increased plumpness across all lengths, 

causing rate of gain to be near average despite 

an increased body condition for small and large 

fish (Table 4.3). In 1996 and 1998, no species 

exhibited a rate of gain significantly lower or 

higher than the overall rate of gain trend and in 

1994, 1995, 1999, 2000, 2001, and 2002 only a 

single species exhibited a significantly reduced or 

increased rate of gain.

Discussion

La Grange Pool of the Illinois River was the 

only study area containing species exhibiting an 

increased rate of gain when compared to overall 

rate of gain trends (for three out of five species). 

For these species, smaller fish were less plump 

and larger fish were more plump in the Illinois 

River than in main‐stem Upper Mississippi 

River (UMR) areas. This spatial trend suggests 

the presence of biological factors (e.g., food 

availability, competition, climate, hydrology) in 

La Grange Pool that differ from the main‐stem 

UMR. The Illinois River became degraded 

because of human effects (levees, pollution, 

sediment contamination) in the 1950s through 

the early 1970s, coinciding with a decreased 

condition factor in common carp (Theiling 1999). 

Our investigation indicates that the condition 

of common carp in the Illinois River remains 

below average. However, for the other species 

studied, condition compared favorably between 

La Grange Pool and main‐stem UMR sites. 

Further investigation into bioenergetics and 

growth of these species could identify specific 

causes for the observed spatial patterns in 

length‐weight relationships.

Black crappie and common carp were the 

only two species that exhibited a similar rate 

of gain response to temporal variability (down 

in 1993 and up in 1997). Black crappie and 

common carp are most closely associated with 
48

backwater and side channel habitats in the Upper 

Mississippi River System, whereas the other 

three study species are most closely associated 

with main channel and side channel habitats. 

The Mississippi and Illinois Rivers surpassed 

flood stage in all study areas in 1993 and 1997, 

but the timing of the flood events differed. The 

1993 flood event occurred in late June and early 

July (with a smaller flood in April), but the 1997 

flood event occurred primarily in April. This 

suggests that the timing of flood events may 

be as important to fish productivity as is the 

flood itself. Future conceptual models for fish 

productivity in large rivers may be improved 

by incorporating flood frequency and flood 

predictability (as done for community structure 

in smaller rivers by Poff and Ward [1989]), as 

well as a measure of flood timing.

Table 4.1. Results of tests for parallel slopes and equal Y-intercepts for length-weight regressions of fish collected in September 16–

October 31, 1993–2002, from the six Long Term Resource Monitoring Program study areas within the Upper Mississippi River System. 

Slope Intercept

Comparison df F P a df F P a

Black crappie (Pomoxis nigromaculatus)

Among years 9, 4461 10.76 <0.0001 9, 4461 10.69 <0.0001

Among areas 5, 4469 16.85 <0.0001 5, 4469 17.15 <0.0001

Channel catfish (Ictalurus punctatus)

Among years 9, 2789 2.95 0.0017 9, 2789 2.96 0.0017

Among areas 5, 2797 4.36 0.0006 5, 2797 4.19 0.0009

Common carp (Cyprinus carpio)

Among years 9, 7602 5.87 <0.0001 9, 7602 6.55 <0.0001

Among areas 5, 7610 8.74 <0.0001 5, 7610 8.74 <0.0001

Sauger (Sander canadensis)

Among years 9, 2123 1.72 0.0791 9, 2123 1.65 0.0968

Among areas 5, 2131 9.96 <0.0001 5, 2131 9.77 <0.0001

Walleye (Sander vitreus)

Among years 9, 1177 5.86 <0.0001 9, 1177 5.93 <0.0001

Among areas 4, 1187 14.88 <0.0001 4, 1187 15.47 <0.0001

a

Significant P values are in bold text. Significant P values indicate significantly different slopes for tests of parallel slopes 

and indicate significantly different intercepts for tests of equal intercepts. 
49

Table 4.2. Length-weight regression statistics by study area and species for fish collected from the Upper Mississippi River System for 

the Long Term Resource Program in 1993–2002 a. 

Study area b N 

Slope

(a)

Intercept 

(b) r

2

PW1

(g)

PW2

(g) t P c

Black crappie (Pomoxis nigromaculatus; 130–199 mm total length)

P4 1,393 3.236 -5.356 0.972 31 250 -2.06 0.0392

P8 466 3.277 -5.447 0.970 30 254 -0.00 0.9974

P13 1,352 3.240 -5.369 0.962 30 248 -1.90 0.0581

P26 306 3.258 -5.409 0.956 30 250 -0.49 0.6251

LG 916 3.505 -5.981 0.937 27 262 8.02 <0.0001

OR 48 3.340 -5.590 0.945 30 259 0.71 0.4785

 All 4,481 3.277 -5.452 0.963 30 251

Channel catfish (Ictalurus punctatus; 280–409 mm total length)

P4 242 3.466 -6.287 0.905 157 2,315 -0.28 0.7806

P8 478 3.518 -6.416 0.976 156 2,400 0.90 0.3679

P13 181 3.479 -6.305 0.963 162 2,414 -0.08 0.9360

P26 752 3.489 -6.334 0.938 160 2,407 0.17 0.8666

LG 518 3.616 -6.672 0.971 150 2,496 3.59 0.0003

OR 638 3.406 -6.137 0.938 158 2,225 -2.25 0.0243

 All 2,809 3.484 -6.328 0.953 158 2,364

Common carp (Cyprinus carpio; 280–409 mm total length)

P4 724 2.885 -4.557 0.848 318 1,996 -2.75 0.0060

P8 299 2.883 -4.514 0.902 348 2,176 -1.89 0.0588

P13 654 2.872 -4.514 0.873 327 2,031 -2.86 0.0043

P26 2,732 3.002 -4.858 0.954 308 2,079 0.01 0.9893

LG 2,307 2.898 -4.637 0.922 285 1,801 -4.47 <0.0001

OR 906 3.061 -5.010 0.920 303 2,121 2.04 0.0418

 All 7,622 3.002 -4.873 0.928 297 2,008

Sauger (Sander canadensis; 200–299 mm total length)

P4 754 3.460 -6.242 0.975 52 479 1.75 0.0795

P8 442 3.384 -6.060 0.950 53 464 -0.81 0.4196

P13 724 3.300 -5.855 0.957 55 451 -3.39 0.0007

P26 86 3.132 -5.435 0.876 59 438 -3.51 0.0004

LG 130 3.656 -6.709 0.960 50 523 3.90 <0.0001

OR 7 3.181 -5.529 0.982 61 472 -1.21 0.2282

 All 2,143 3.412 -6.123 0.963 53 473

Walleye (Sander vitreus; 250–379 mm total length)

P4 536 3.180 -5.499 0.964 134 1,283 -5.52 <0.0001

P8 470 3.396 -6.067 0.984 119 1,334 2.14 0.0326

P13 165 3.431 -6.159 0.984 117 1,342 2.39 0.0168

P26 10 3.593 -6.531 0.964 122 1,564 1.54 0.1244

LG 16 3.042 -5.119 0.954 150 1,302 -1.42 0.1571

OR

 All 1,197 3.338 -5.912 0.977 124 1,327

a Length-weight regression parameters include (a) slope, (b) intercept, and (r2

) coefficient of determination, as well 

as predicted weight upon entering stock length (PW1) and upon leaving quality length (PW2) based upon regression 

parameters. P-values and t statistics of comparisons between study area slopes and the slope of the overall length‐weight 

regression line are included. Slopes were considered significantly different at P < 0.008 (Bonferroni correction). Stock and 

quality length designations are from Anderson and Neumann (1996). 

b P4 = Pool 4, P8 = Pool 8, P13 = Pool 13, P26 = Pool 26, LG = La Grange Pool, and OR = Open River. c Significant P values are in bold. 
50

Table 4.3. Length-weight regression statistics by year and species for fish collected from the Upper Mississippi River System by the Long 

Term Resource Program in 1993–2002 a. 

Year N Slope (a)

Intercept 

(b) r

2 PW1

 (g) PW2 (g) t P b

Black crappie (Pomoxis nigromaculatus; 130-199 mm total length)

1993 292 3.097 -5.029 0.938 33 247 -4.97 <0.0001

1994 471 3.164 -5.212 0.969 30 234 -4.12 <0.0001

1995 690 3.403 -5.730 0.968 29 266 4.68 <0.0001

1996 377 3.384 -5.703 0.928 28 259 2.68 0.0074

1997 295 3.390 -5.709 0.962 29 259 2.96 0.0030

1998 374 3.218 -5.310 0.972 31 252 -1.78 0.0752

1999 567 3.303 -5.510 0.969 30 254 0.78 0.4362

2000 486 3.291 -5.487 0.974 30 251 0.51 0.6087

2001 553 3.322 -5.558 0.975 29 252 1.50 0.1347

2002 376 3.262 -5.421 0.953 30 249 -0.41 0.6794

 All 4,481 3.277 -5.452 0.963 30 251 . .

Channel catfish (Ictalurus punctatus; 280-409 mm total length)

1993 208 3.514 -6.370 0.971 170 2,601 0.59 0.5539

1994 285 3.582 -6.586 0.961 151 2,446 2.17 0.0303

1995 147 3.469 -6.302 0.915 154 2,279 -0.23 0.8157

1996 233 3.517 -6.413 0.966 156 2,402 0.65 0.5145

1997 559 3.540 -6.488 0.956 150 2,342 1.50 0.1334

1998 232 3.508 -6.397 0.968 154 2,352 0.45 0.6544

1999 210 3.493 -6.355 0.966 156 2,353 0.15 0.8777

2000 228 3.473 -6.289 0.955 162 2,410 -0.19 0.8465

2001 312 3.505 -6.382 0.947 157 2,388 0.47 0.6367

2002 395 3.332 -5.934 0.939 166 2,210 -3.83 0.0001

 All 2,809 3.484 -6.328 0.953 158 2,364 . .

Common carp (Cyprinus carpio; 280-409 mm total length)

1993 558 2.890 -4.543 0.921 338 2127 -3.37 0.0007

1994 1415 2.997 -4.852 0.965 303 2043 -0.23 0.8166

1995 661 3.035 -4.978 0.934 281 1939 0.91 0.3611

1996 462 2.993 -4.846 0.904 301 2020 -0.20 0.8441

1997 887 3.117 -5.160 0.924 294 2,133 3.48 0.0005

1998 712 2.984 -4.811 0.848 310 2,069 -0.40 0.6891

1999 780 3.031 -4.962 0.927 285 1,962 0.77 0.4386

2000 688 3.168 -5.310 0.855 277 2,079 3.62 0.0003

2001 795 3.140 -5.264 0.884 263 1,939 3.56 0.0004

2002 664 3.056 -5.038 0.913 276 1,927 1.34 0.1810

 All 7,622 3.002 -4.873 0.928 297 2,008 . .
51

Table 4.3. (Continued)

Year N Slope (a)

Intercept 

(b) r

2 PW1

 (g) PW2 (g) t P b

Sauger (Sander canadensis; 200-299 mm total length)

1993 233 3.356 -5.988 0.954 54 463 -1.20 0.2316

1994 194 3.332 -5.928 0.901 55 461 -1.39 0.1654

1995 239 3.483 -6.285 0.980 54 497 1.80 0.0724

1996 163 3.352 -5.976 0.911 55 465 -0.95 0.3423

1997 164 3.461 -6.228 0.969 54 497 0.84 0.4030

1998 276 3.392 -6.093 0.976 52 451 -0.45 0.6542

1999 387 3.353 -5.991 0.970 53 452 -1.47 0.1416

2000 214 3.435 -6.181 0.972 53 475 0.51 0.6125

2001 231 3.348 -5.944 0.968 58 489 -1.36 0.1741

2002 42 3.195 -5.602 0.972 56 433 -1.64 0.1002

 All 2,143 3.412 -6.123 0.963 53 474

Walleye (Sander vitreus; 250-379 mm total length)

1993 103 3.407 -6.096 0.982 119 1,336 1.51 0.1323

1994 91 3.535 -6.419 0.987 114 1,410 3.44 0.0006

1995 200 3.281 -5.745 0.958 133 1,367 -1.53 0.1265

1996 129 3.448 -6.189 0.978 120 1,392 2.06 0.0396

1997 72 3.446 -6.198 0.980 116 1,347 1.81 0.0701

1998 149 3.423 -6.146 0.987 115 1,316 2.09 0.0368

1999 148 3.189 -5.548 0.983 126 1,213 -3.27 0.0011

2000 126 3.247 -5.686 0.980 126 1,267 -1.56 0.1181

2001 166 3.257 -5.690 0.983 132 1,336 -1.72 0.0856

2002 12 3.209 -5.575 0.977 132 1,291 -0.79 0.4273

 All 1,197 3.338 -5.912 0.977 124 1,327

a

Length-weight regression parameters include (a) slope, (b) intercept, and (r2) coefficient of determination, as well as 

predicted weight upon entering stock length (PW1)and upon leaving quality length (PW2) based upon regression parameters. 

P values and t statistics of comparisons between year slopes and the slope of the overall length-weight regression line are 

included. Slopes were considered significantly different at P < 0.005 (Bonferroni correction). Length designations are from 

Anderson and Neumann (1996). 

b

 Significant P values are in bold.
52

Chapter 5. Temporal and Spatial 

Trends in Relative Abundance

Introduction

This chapter contains an investigation of 

variation in abundance of fish populations 

among years, study areas, and aquatic areas 

(e.g., backwater shorelines, main channel 

borders, and side channel borders) in the Upper 

Mississippi River (UMR). Relative abundance 

data (typically defined as catch‐per–unit‐effort) 

are routinely collected to index the density of 

fish populations in inland waters (Ney 1999). 

The Long Term Resource Monitoring Program 

(LTRMP) fish sampling design provides an 

opportunity to assess variation in the relative 

abundance of fish species among study areas 

(longitudinal‐spatial variation), aquatic areas 

(lateral‐spatial variation), and among years 

(temporal variation). Quantifying how fish 

populations vary across space and time can 

isolate factors responsible for observed patterns 

in fish abundance. Identifying the primary 

factors responsible for population abundance 

patterns will help fisheries managers determine 

species most likely to respond to local habitat 

modifications, climatic variability, or degradation 

of specific types of aquatic areas.

This investigation used analysis of variance 

(ANOVA) to identify trends in the relative 

abundance of 50 UMR species. Analysis of 

variance is based on the premise that an increase 

in the difference among factor level means 

is associated with an increase in variability 

when comparing among factor levels (Rao 

1998; Zar 1999). For example, if the mean 

abundance of bluegill (Lepomis macrochirus) 

is similar in backwaters and channel habitats, 

low levels of variance will be associated with 

samples from the two habitats. Conversely, if 

the mean abundance of bluegill is dissimilar in 

backwater and channel habitats, high levels of 

variance will be associated with samples from 

the two habitats. Analysis of variance is most 

commonly applied to determine if a response 

variable differs significantly among factor levels 

(as with fish abundance in channel habitats and 

backwater habitats in the above example). In 

this investigation, ANOVA was used to measure 

variability associated with spatial and temporal 

factors, then these measurements of variability 

were used to contrast and compare species 

relative abundance patterns. These variance 

partitioning techniques should be viewed as data 

exploration.

We present results as visual representations 

of how fish species relate to one another based on 

longitudinal‐spatial, lateral‐spatial, and temporal 

variance. This was an observational investigation 

because no specific a priori hypotheses are tested. 

The visual representations of variation in relative 

abundance represent a 10‐year period of field 

collection composed of 3,324 electrofishing 

samples. These figures can be used as guides 

by resource managers for applied habitat 

management or for formulating hypothesis 

concerning UMR fish abundance dynamics. The 

goal of this investigation was to classify groups 

of species that share similar spatial and temporal 

variance patterns, and are likely to respond in 

a similar manner to habitat modifications or 

habitat change. Our results provide a starting 

point for the development of statistical models 

for relating abundance patterns to environmental 

characteristics. 

Methods

In 1993–2002, standard LTRMP protocols 

were used to collect fish samples (N = 3,324) 

using day electrofishing at randomly selected 

shoreline sites in contiguous backwater, main 

channel, and side channel aquatic areas of Pools 

4, 8, 13, and 26 of the UMR and La Grange 

Pool of the Illinois River. Collection crews 

consisted of three persons (i.e., a pilot and two 

persons operating dip nets). Electrofishing 

runs were approximately 15 min and covered 

approximately 200 m of shoreline. Dip netters 

collected fish as they appeared, regardless of size 

and species. Voltage and amperage were adjusted 

to achieve a uniform base power of 3,000 watts 

after correcting for on‐site conductivity and 

temperature variation (Burkhardt and Gutreuter 

1995). A pulse frequency of 60 Hz and a 

duty‐cycle of 25% were used for all runs. 

Within each study area, nearly equal 

electrofishing effort was applied among three 
53

open‐water study periods (June 15–July 31, 

August 1–September 15, September 16–October 

31). The number of samples per aquatic area (i.e., 

contiguous backwater shorelines, main channel 

borders, and side channel borders) was based on 

the proportional contribution of each aquatic area 

type to the total aquatic area of each study area 

(Gutreuter et al. 1995). The Open River study 

area was excluded from analysis because it did 

not contain sites in backwater aquatic areas.

Fish abundance is not typically normally 

distributed, both spatially and temporally, 

resulting in non‐normally distributed and 

right‐skewed samples for low‐density fish 

populations (Bannerot and Austin 1983; Hubert 

1996; Counihan et al. 1999). The distribution of 

catch‐per‐unit‐effort (CPUE, catch/effort) data 

is affected by population density and, therefore, 

no single data transformation can be applied in 

all cases to generate a more normal distribution 

(Hubert 1996; Counihan et al. 1999). Previous 

researchers have suggested that for low‐density 

populations an index based on the presence 

or absence of organisms in samples may be 

superior to indexes based on the arithmetic mean 

(Bannerot and Austin 1983; Counihan et al. 

1999). In this study we used the proportion of 

electrofishing runs containing a given species, or 

size group of a species, to index abundance.

Analysis was limited to those species present 

in LTRMP samples from all five study areas 

in at least 1 year during 1993–2002 (N = 50). 

To assess relations between size‐classes within 

species, fish were grouped based upon stock 

and substock length designations for those 

species with proposed length designations 

in peer‐reviewed literature (N = 25, size 

designations from Anderson and Neumann 1996 

and Bister et al. 2000). This resulted in 75 study 

groups (50 species with 25 species split into 

stock and substock length).

For each sampling year, the proportion 

of positive electrofishing runs was calculated 

independently for each fish species and size 

class of interest for each study area, sampling 

period, and aquatic area type using the following 

formula: PPR = p/n; where PPR = the proportion 

of positive runs, p = the number of runs where 

the species and size group of interest was present, 

and n = the total number of electrofishing runs 

completed. This study design resulted in equal 

effort for each study area and aquatic area type 

within years. Proportion data have a binomial 

distribution; therefore, the proportion of positive 

electrofishing runs data was transformed 

using a modified Freeman and Tukey arcsine 

transformation (Zar 1999) before further analysis. 

We considered two primary spatial factors 

(aquatic area type and study area) and one 

temporal factor (year), as well as all higher 

order interactions, resulting in seven model 

factors. Among groups variation at the study 

area, aquatic area, year, and interaction factor 

levels was measured as Type III sums of squares 

using a three‐factor unbalanced ANOVA (GLM 

procedure; SAS Institute 1999). The ratio of 

factor sum of squares (factor SS) to total sum of 

squares (total SS) for each ANOVA factor was 

derived for each of the 75 study groups. Factor 

SS/total SS served as a measure of the relative 

importance of each factor to the total variation 

in relative abundance (e.g., the percentage 

of variation in bluegill abundance explained 

by variation among aquatic areas). Principal 

components analysis (PCA; CANOCO v.4.5; ter 

Braak and Smilauer 2002) and two‐dimensional 

plots were used to ordinate species based upon 

factor SS/total SS for the model factors. 

Visual representations of variation among 

study areas (longitudinal‐spatial variation), 

aquatic areas (lateral‐spatial varitation), and 

years (temporal variation) constructed through 

PCA and two‐dimensional plots were used to 

assess which species and size groups exhibited 

similar temporal and spatial abundance 

patterns. Principal components analysis was 

done separately for substock‐length groups, 

stock‐length groups, and species with no size 

designation to allow easier interpretation of 

figures. Two‐dimensional plots were divided 

into quadrants based upon median values for 

factor SS/total SS. For select species, pie charts 

were constructed to visually represent variance 

decomposition into factor SS/total SS for the 

seven model factors. F values (within factors 

mean square/error mean square) and P values 

derived from ANOVA were used to quantitatively 

describe the significance of factors.
54

Results

Three‐factor (study area, aquatic area, year) 

ANOVA models explained from 39% to 90% of 

the variation in study group relative abundance 

with a mean of 63% for the 75 study groups. The 

proportion of total SS accounted for by study 

area, aquatic area, year, and interaction factors 

varied among study groups, as did subsequent 

F values (Figure 5.1 provides examples of 

variance decomposition and among group 

variation in the proportion of total SS explained 

by model factors).

Ranges in factor SS/total SS were sufficient 

to ordinate fish species using two‐dimensional 

plots and PCA. The proportion of total SS 

accounted for by the study area factor ranged 

from a low of 5.4% (F = 12.737, df = 4,296, 

P < 0.0001) for substock‐length black crappie, 

to a high of 67.4% (F = 231.64, df = 4,296, 

P < 0.0001) for golden redhorse (i.e., relative to 

other factors, the abundance variation associated 

with differences among study areas was lowest 

for stock‐length black crappie and highest for 

golden redhorse). The proportion of total SS 

accounted for by the aquatic area factor ranged 

from a low of <0.1% (F = 0.002, df = 2,296, 

P = 0.9985) for substock‐length sauger, to a high 

of 32.9% (F = 142.568, df = 2,296, P < 0.0001) 

for substock‐length bluegill. The proportion of 

total SS accounted for by the year factor ranged 

from a low of 0.4% (F = 0.429, df = 9,296, 

P = 0.9188) for shortnose gar, to a high of 

20.3% (F = 18.728, df = 9,296, P < 0.0001) 

for substock‐length common carp. F‐values 

indicated significant differences among study 

areas (P < 0.05) for all study groups (i.e., all 

species and size groups), significant differences 

among aquatic areas (P < 0.05) for 72 of 75 study 

groups, and significant differences among years 

(P < 0.05) for 59 of 75 study groups. 

Significant interactions were present for 

many species and size groups. This suggests 

that UMR abundance patterns are spatially 

and temporally complex (i.e., year differences 

were dependent upon aquatic area and study 

area, aquatic area differences were dependent 

upon study area). Significant year ×study area 

interaction (P < 0.05) was present for 63 of 

75 study groups, significant year × aquatic 

area interaction was present for 8 of 75 study 

groups, and significant aquatic area × study 

area interaction was present for 63 of 75 study 

groups. Significant three‐way (year × aquatic 

area × study area) interaction was present for 8 of 

75 study groups. 

Two‐dimensional plots of factor SS/

total SS for aquatic area, study area, and year 

factors are shown in Figures 5.2–5.4. Table 5.1 

contains six‐letter codes used to identify fish 

species and length groups of species in figures. 

Stock‐length and substock‐length centrarchids 

(i.e., black crappie, bluegill, largemouth bass, 

orangespotted sunfish, smallmouth bass, and 

white crappie) exhibited high levels of variation 

in relative abundance when comparing among 

aquatic area types (Figures 5.2–5.3). Bowfin, 

emerald shiner, substock‐length flathead catfish, 

golden shiner, stock‐length longnose gar, river 

shiner, and yellow perch also varied considerably 

among aquatic area types. Broadcast and pelagic 

spawning species associated with main channel 

habitats (e.g., common carp, freshwater drum, 

sauger, smallmouth buffalo, walleye and white 

bass) exhibited high levels of temporal variability 

in substock‐length abundance (Figures 5.2 and 

5.4). Similarly, the abundance of stock‐length 

common carp, gizzard shad, smallmouth buffalo, 

and sauger showed high levels of temporal 

variability (Figures 5.2 and 5.4). Species 

exhibiting high levels of variation in abundance 

among study areas for both stock‐length 

and substock‐length fish included channel 

catfish, gizzard shad, northern pike, shorthead 

redhorse, smallmouth bass, smallmouth buffalo, 

yellow perch, and walleye (Figures 5.3–5.4). 

Additionally, bullhead minnow, golden redhorse, 

logperch, quillback, river shiner, shortnose gar, 

shovelnose sturgeon, and stonecat exhibited high 

variability when comparing among study areas 

(Figures 5.3–5.4).

Temporal abundance patterns were highly 

dependent upon study area (i.e., year × study 

area interaction) for substock‐length black 

buffalo, green sunfish, sauger, and white bass. 

Lateral‐spatial abundance patterns were highly 

dependent upon year (i.e., year × aquatic 

area interaction) for stock‐length channel 
55

Stock-Length Longnose Gar

Year

2%

Error Total

61%

Aquatic Area

10%

Study Area

8%

Aquatic

Area*Study Area

4%

Year*Aquatic 

Area*Study Area

9%

Year*Aquatic 

Area

2%

Year*Study Area

4%

Shovelnose Sturgeon

Year

5% Aquatic Area

8%

Study Area

38%

Year*Aquatic

Area*Study Area

3%

Error Total

10%

Aquatic 

Area*Study Area

30%

Year*Study Area

5%

Year*Aquatic

Area

1%

Figure 5.1. Pie charts representing the results of variance decomposition for the relative abundance (proportion of positive electrofishing 

runs) of stock-length longnose gar (Lepisosteus osseus) and shovelnose sturgeon (Scaphirhynchus platorynchus) collected by electrofishing 

from five study areas in the Upper Mississippi River System. The proportion of total sum of squares by model factors, as visually depicted 

in pie charts, was used to ordinate and group species based on lateral-spatial (aquatic area), longitudinal-spatial (study area), and 

temporal (year) variance patterns.
56

0.01

0.1

1

10

100

0.1 1 10 100

Year proportion sum of squares

Aquatic area proportion sum of squares

I II

III IV

4

10

16

0 1 2 3 4

Year proportion sum of squares

Aquatic area proportion sum of squares

FHCFST

LNGRST

WTCPST

BUSKAL SHRHST SHDRAL

SMBSSS

NTPKSS BKBFST FWDMST GNSFST

RVSNAL LMBSST

WTCPSS SMBSST WTBSST

FHCFSS

BKCPST

BWFNAL

GDSNAL

I

4

10

16

22

28

4 5 6 7 8 9 10 11 12 13 14

Year proportion sum of squares

Aquatic area proportion sum of squares

OSSFAL BKCPSS

YWPHST

BLGLSS

LMBSS

ERSNAL

SMBFSS BHMWAL CARPST

STCTAL SNSGAL

GDEYAL

SVCBAL

BLGLST

MNEYAL

WTSKSS

SNSNAL YWPHSS

II

0

1

2

3

4

0 1 2 3 4

Year proportion sum of squares

Aquatic area proportion sum of squares

CNCFSS

SNGRAL

TPMTAL

BMBFST

GNSFSS GDRHAL

LNGRSS

MDDRAL

WLYEST

WTSKST

BKBHST CNCFST

FHMWAL

NTPKST

RVCSST

YWBHST

CNLPAL III

0

1

2

3

4

4 6 8 10 12 14 16 18 20

Year proportion sum of squares

Aquatic area proportion sum of squares

FWDMSS

GZSDSS CARPSS

WLYESS

QLBKAL SMBFST GZSDST

LGPHAL

BKBFSS SGERSS

SHRHSS

WTBSSS RVCSSS

STSNAL

SGERST

BKBHSS

YWBHSS

BMBFSS BNMWAL

BKSSAL IV

Lepisosteidae Percidae Other Family

Catostomidae Centrarchidae Cyprinidae Ictaluridae 

Figure 5.2. Proportion of total variation in abundance explained by year and aquatic area factors for 75 fish study groups collected with 

day electrofishing from the Upper Mississippi River System in 1993–2002. The overall view (center) displays all 75 study groups with 

dashed lines representing medians for the axes. Median values were used to separate study groups into quadrants I (top left), II (top 

right), III (bottom left), and IV (bottom right). Six-letter codes represent species and length groups of study groups (Table 5.1). 
57

4

10

16

22

28

5 10 15 20

Study area proportion sum of squares

Aquatic area proportion sum of squares

SVCBAL BUSKAL

LNGRST

BWFNAL

SNSNAL

SHDRAL

GDSNAL

CARPST

FHCFSS

BLGLSS

MNEYAL

GDEYAL

WTCPSS

BLGLST

BKCPST

GNSFST FWDMST

BKCPSS

ERSNAL

FHCFST

WTCPST

I

4

10

16

22

21 31 41 51 61

Study area proportion sum of squares

Aquatic area proportion sum of squares

WTSKSS SMBSSS

SMBSST

SMBFSS SHRHST

YWPHST

BHMWAL

STCTAL

SNSGAL

BKBFST

RVSNAL

OSSFAL

NTPKSS YWPHSS

SS

LMBSST

WTBSST

LMBSSS

II

0.01

0.1

1

10

100

1 10 100

Study area proportion sum of squares

Aquatic area proportion sum of squares

I II

III IV

0

1

2

3

4

5 10 15 20

Study area proportion sum of squares

Aquatic area proportion sum of squares

WTBSSS

BKSSAL

FHMWAL

SGERSS

CARPSS

BMBFSS

SGERST

CNLPAL

RVCSST

YLBHSS

LNGRSS

BNMWAL

BKBFSS

BKBHST

GNSFSS

YHBHST

BKBHSS

III

0

1

2

3

4

20 30 40 50 60

Study area proportion sum of squares

Aquatic area proportion sum of squares

GZSDST

BMBFST

GZSDSS TPMTAL

CNCFST

SMBFSS

NTPKST

WLYEST

FWDMSS

LGPHAL QLBKAL

WLYESS

STSNAL

RVCSSS

WTSKST

SHRHSS

MDDRAL

GDRHAL

CNCFSS

SNGRAL

IV

Lepisosteidae Percidae Other Family

Catostomidae Centrarchidae Cyprinidae Ictaluridae 

Figure 5.3. Proportion of total variation in abundance explained by study area and aquatic area factors for 75 fish study groups collected 

with day electrofishing from the Upper Mississippi River System in 1993–2002. The overall view (center) displays all 75 study groups 

with dashed lines representing medians for the axes. Median values were used to separate study groups into quadrants I (top left), II (top 

right), III (bottom left), and IV (bottom right). Six-letter codes represent species and length groups of study groups (Table 5.1).
58

1

10

100

0.1 1 10 100

Year proportion sum of squares

Study area proportion sum of squares

I II

III IV

20

30

40

50

60

0 1 2 3 4

Year proportion sum of squares

Study area proportion sum of squares

GDRHAL

WTSKST

SMBSST SMBSSS

SHRHST

SNGRAL BMBFST

CNCFSS RVSNAL

CNCFST

WTBSST

WLYEST NTPKST

TPMTAL MDDRAL

NTPKSS

BKBFST

WTCPST

LMBSST

I

20

30

40

50

4 7 10 13

Year proportion sum of squares

Study area proportion sum of squares

GZSDSS

RVCSSS

SMBFSS

YWPHSS

YWPHST

SMBFST BHMWAL

FWDMSS SNSGAL

QLBKAL

WLYESS

WTSKSS

GZSDST

LGPHAL

SHRHSS

STCTAL

STSNAL

LMBSSS

OSSFAL

II

7

11

15

19

0 1 2 3 4

Year proportion sum of squares

Study area proportion sum of squares

BUSKAL

FHMWAL

BWFNAL FWDMST SHDRAL

CNLPAL GDSNAL

RVCSST BKBHST

GNSFSS FHCFSS

WTCPSS

YLBHST FHCFST BKCPST LNGRSS LNGRST GNSFST

III

5

9

13

17

4 9 14 19

Year proportion sum of squares

Study area proportion sum of squares

BKSSAL

BMBFSS

WTBSSS

SNSNAL SGERST

CARPST GDEYAL

BNMWAL CARPSS

BLGLST

SGERSS

BKBHSS

ERSNAL

BLGLSS

YLBHSS

BKBFSS

MNEYAL

BKCPSS

SVCBAL

IV

Lepisosteidae Percidae Other Family

Catostomidae Centrarchidae Cyprinidae Ictaluridae 

Figure 5.4. Proportion of total variation in abundance explained by year and study area factors for 75 fish study groups collected with day 

electrofishing from the Upper Mississippi River System in 1993–2002. The overall view (center) displays all 75 study groups with dashed 

lines representing medians for the axes. Median values were used to separate study groups into quadrants I (top left), II (top right), III 

(bottom left), and IV (bottom right). Six-letter codes represent species and length groups of study groups (Table 5.1). 
59

catfish, bluntnose minnows, substock‐length 

black crappie, and substock‐length bigmouth 

buffalo. Lateral‐spatial abundance patterns 

were dependent upon study area (i.e., aquatic 

area × study area interaction) for stock‐ and 

substock‐length black bullheads, yellow 

bullheads, and white suckers, as well as 

shovelnose sturgeon and stonecat.

Graphical PCA results for substock‐length 

fish, stock‐length fish, and species with no size 

designation are in Figures 5.5–5.7, respectively. 

The first two principal components axes captured 

80% of the total variance in the proportions of 

total SS for substock‐length fish (Table 5.2), 86% 

for stock‐length fish (Table 5.3), and 87% for 

species without size designations (Table 5.4). 

Species varied considerably with respect 

to the proportion of total variation in relative 

abundance explained by differences among 

study areas (long vector length in Figures 

5.5–5.7). That is, some species were distributed 

evenly throughout study areas whereas other 

species had a much higher or lower relative 

abundance in an individual study area or study 

areas. For example, smallmouth bass relative 

abundance varied considerably when comparing 

among study areas, but black crappie relative 

abundance was similar when comparing among 

study areas. Species varied comparatively little 

with respect to the proportion of total variation 

explained by differences among years (short 

vector length in Figures 5.5–5.7). In other 

words, all species varied in relative abundance 

on a year‐to‐year basis, but when comparing 

among species, differences in temporal variation 

were slight when compared to differences in 

longitudinal‐spatial variation. The proportion of 

total variation in relative abundance explained by 

differences among aquatic areas was important 

for separating substock‐length groups of species 

(Figure 5.5), but was comparatively unimportant 

for stock‐length groups and species without size 

designations. Species exhibiting high proportions 

of variation explained by year × aquatic area 

interaction generally had high proportions of 

variation explained by year × study area and 

year × study area × aquatic area interaction 

(similar vector directions in Figures 5.5–5.7). 

The proportion of variance explained by 

aquatic area × study area interaction was an 

important component for separating adult 

fishes (i.e., stock‐length and no size designation 

groups), but was comparatively unimportant for 

substock‐length fish.

Discussion

The abundance dynamics of fish populations 

inhabiting the UMRS are complex. In a large 

river system, species abundance varies temporally 

(i.e., from year to year), longitudinally (i.e., 

from upstream to downstream), and laterally 

(i.e., among aquatic areas at the same latitude). 

Risotto and Turner (1985) suggested that factors 

affecting fish catch on the UMR could be divided 

into two groups (i.e., short‐ and long‐term 

factors) on the basis of the type of influence 

imposed by the factor. Short‐term factors, such 

as rainfall and water temperature, affect fish 

catch on an annual basis, and long‐term factors, 

such as latitude and geomorphology, determine 

overall productivity, which influences long‐term 

trends in abundance (Risotto and Turner 1985). 

Our investigation quantified short‐term variation 

(i.e., year to year) and sought to distinguish 

differences among species in the relative 

importance of factors affecting long‐term 

abundance. Recognizing the responses of species 

to long‐term factors can help identify appropriate 

management actions and realistic goals.

Species differed markedly in the amount 

of relative abundance variation caused by 

longitudinal‐spatial factors, differed to a lesser 

extent in variation caused by lateral‐spatial 

factors, and were most similar with respect 

to temporal variation. Fish management on 

large rivers is often centered on improving the 

abundance of desirable fish populations by 

minimizing temporal variability (e.g., water 

level management and harvest regulations), 

enhancing lateral habitats (e.g., increasing 

connection between channel and off‐channel 

habitats, and improving backwater overwintering 

habitat), or addressing longitudinal‐spatial 

factors (e.g., optimizing hydrology and land‐use 

practices). Thus, the success of a management 

initiative is contingent on addressing factors 

responsible for variation in abundance. 

Longitudinal‐spatial variation is usually a 
60

Figure 5.5. Biplot showing the first two principal component axes and demonstrating the loadings of each species on the seven analysis 

of variance (ANOVA) factors for substock-length fish. The ordination was based on a species x ANOVA factor matrix where the proportion 

of total sum of squares accounted for by each model factor comprised the data. The first two axes explained 80% of the variation in the 

univariate ANOVA results. AA = Aquatic area, SA= Study area, and YR = Year on axes labels. Six-letter codes represent species and 

length groups of study groups (Table 5.1). 

Figure 5.6. Biplot showing the first two principal component axes and demonstrating the loadings of each species on the seven analysis 

of variance (ANOVA) factors for stock-length fish. The ordination was based on a species x ANOVA factor matrix where the proportion 

of total sum of squares accounted for by each model factor comprised the data. The first two axes explained 80% of the variation in the 

univariate ANOVA results. AA = Aquatic area, SA = Study area, and YR = Year on axes labels. Six-letter codes represent species and 

length groups of study groups (Table 5.1).
61

Figure 5.7. Biplot showing the first two principal component axes and demonstrating the loadings of each species on the seven analysis 

of variance (ANOVA) factors for fish species without length designations. The ordination was based on a species x ANOVA factor matrix 

where the proportion of total sum of squares accounted for by each model factor comprised the data. The first two axes explained 80% 

of the variation in the univariate ANOVA results. AA = Aquatic area, SA = Study area, and YR = Year on axes labels. Six-letter codes 

represent species and length groups of study groups (Table 5.1).

reflection of systemic factors (e.g., hydrology, 

water chemistry, floodplain morphology) that are 

not easily controlled through direct management 

intervention for the obvious reasons of scope 

and cost. For this reason, management actions 

typically focus on controlling year‐to‐year 

variation and lateral habitat improvements in 

an effort to mitigate for undesirable systemic 

factors. 

Species that exhibited the highest levels 

of variation among aquatic area types would 

be most likely to show a relative abundance 

response to habitat improvements focusing 

on specific types of macrohabitats. Not 

surprisingly, centrarchid species exhibited 

high levels of variation among aquatic areas. 

Centrarchids remain a primary target of many 

aquatic habitat rehabilitation and enhancement 

projects (HREPs) on the UMR and have shown 

positive abundance responses to HREPs focused 

on backwater habitat (Gent et al. 1995). This 

investigation suggests that bowfin, emerald 

shiners, substock‐length flathead catfish, golden 

shiners, stock‐length longnose gar, river shiners, 

and yellow perch would also respond positively 

to HREPs applied to key macrohabitats in river 

reaches at hospitable latitudes. Conversely, 

important recreational species—such as 

channel catfish, sauger, and walleye—exhibited 

comparatively low levels of variation among 

aquatic areas, which suggests that HREPs 

focused on single macrohabitats are less likely to 

initiate an abundance response for these species.

When considering substock‐length 

groups, temporal variation was in general 

most pronounced for species associated with 

channel habitats and low parental care (e.g., 

common carp, freshwater drum, sauger, 

smallmouth buffalo, walleye, white bass) and 

least pronounced for species associated with 

high parental care (e.g., channel catfish, flathead 

catfish, green sunfish, smallmouth bass). Those 

species exhibiting the highest levels of temporal 

variation generally exhibited low levels of 

variation among aquatic areas (black crappie is 

a notable exception). For this reason, species 
62

exhibiting high levels of temporal variation may 

pose difficulties for managers attempting to 

manipulate their abundance through local habitat 

modifications. 

 Longitudinal‐spatial variation (i.e., upstream 

to downstream) was an important factor for 

separating UMR fish species. Those species 

with low levels of variation among study areas 

(e.g., bluegill, black crappie, flathead catfish, 

green sunfish) can be viewed as having an even 

presence or absence throughout the UMRS. 

These species may or may not be in high 

abundance, but must be adaptable to a wide range 

of chemical and physical constituents. Marked 

long‐term declines or increases in the abundance 

of these species would be indicative of broad 

systemic change. 

Longitudinal‐spatial variation in relative 

abundance also provides insight into how the 

UMRS changes when traveling from upstream 

to downstream. Species with high levels of 

variation in relative abundance when comparing 

among study areas (e.g., bigmouth buffalo, 

golden redhorse, shorthead redhorse, smallmouth 

bass, smallmouth buffalo) can be viewed as 

more reach‐specific. Assuming that abundance 

is a reflection of success, these species found 

conditions more favorable in a particular study 

area or study areas. For redhorse species and 

smallmouth bass, relative abundance was greater 

in Pools 4 and 8, whereas the abundance of 

the buffalo species was greater in Pool 26 and 

La Grange Pool of the Illinois River. Buffalo 

species are well suited for turbid large river 

conditions, whereas redhorse and smallmouth 

bass are more suited to clear‐water and moderate 

size streams (Pflieger 1997). In this way, the life 

histories and adaptations of individual species 

can determine the fish community at a given 

latitude on the UMR, as well as the abundance of 

a given species.

Interaction among lateral‐spatial, 

longitudinal‐spatial, and temporal factors was 

common within study groups. Interaction 

terms identify species that exhibited different 

responses to levels of a factor dependent upon 

levels of another factor. This complexity in 

relative abundance patterns is not surprising 

given the size and dynamic nature of the UMR. 

It serves not only as a measure of complexity, but 

identifies species with unique relative abundance 

patterns warranting further study. For example, 

stock‐length channel catfish exhibited temporal 

(i.e., year to year) variation in aquatic area use. 

This suggests that channel and off‐channel 

habitat use by some species is dependent upon 

short‐term factors (e.g., rainfall), which makes 

it important to consider the affect of temporal 

variability in river conditions when assessing 

lateral‐spatial abundance patterns.

Longitudinal, lateral, and spatial processes 

serve as the cornerstone of current conceptual 

models regarding large river form, function, 

and community structure. The river continuum 

concept (Vannote et al. 1980) stresses the 

importance of longitudinal processes to 

community structure, whereas the flood pulse 

concept (Junk et al. 1989) centers around the 

importance of lateral (floodplain) processes 

to overall productivity. Temporal variability is 

considered a primary force behind population 

abundance and community structure in lotic 

systems (Grossman et al. 1982; Poff and Ward 

1989). Ward (1989) suggested a four‐dimensional 

(i.e., lateral, longitudinal, vertical, temporal) 

conceptual model of lotic ecosystems 

was necessary to achieve ecosystem‐level 

understanding of the dynamics in natural lotic 

systems. Likewise, it is necessary to quantify 

how the abundance of fish populations vary in 

lateral‐space, longitudinal‐space, and across 

time to achieve a holistic perspective of factors 

affecting fish abundance. When considering a 

river system as large as the UMR, the impact 

of systemic longitudinal change upon species 

abundance and community structure is large (as 

evidenced by high among study area abundance 

variability in this investigation). However, when 

viewed from a smaller, pool‐level scale (35–100 

river km), lateral‐spatial and temporal factors are 

primarily responsible for short‐term abundance 

patterns. Despite this, river managers must 

remain cognizant that the long‐term abundance 

of fish populations is ultimately confined 

by systemic processes and the longitudinal 

placement of a river reach. 
63

Table 5.1. Study group codes in alphabetical order. Listing includes the common name, scientific name, and length group represented by 

the study group code. Superscript letters indicate the source of length-based size designations.

Code Common name Scientific name Length group (mm) a

BHMWAL Bullhead minnow Pimephales vigilax All lengths

BKBFSS Black buffalo Ictiobus niger ≤ 279 b

BKBFST Black buffalo Ictiobus niger ≥ 280 b

BKBHSS Black bullhead Ameiurus melas ≤ 149 c

BKBHST Black bullhead Ameiurus melas ≥ 150 c

BKCPSS Black crappie Pomoxis nigromaculatus ≤ 129 c

BKCPST Black crappie Pomoxis nigromaculatus ≥ 130 c

BKSSAL Brook silverside Labidesthes sicculus All lengths

BLGLSS Bluegill Lepomis macrochirus ≤ 79 c

BLGLST Bluegill Lepomis macrochirus ≥ 80 c

BMBFSS Bigmouth buffalo Ictiobus cyprinellus ≤ 279 d

BMBFST Bigmouth buffalo Ictiobus cyprinellus ≥ 280 d

BNMWAL Bluntnose minnow Pimephales notatus All lengths

BUSKAL Blue sucker Cycleptus elongatus All lengths

BWFNAL Bowfin Amia calva All lengths

CARPSS Common carp Cyprinus carpio ≤ 279 c

CARPST Common carp Cyprinus carpio ≥ 280 c

CNCFSS Channel catfish Ictalurus punctatus ≤ 279 c

CNCFST Channel catfish Ictalurus punctatus ≥ 280 c

CNLPAL Chestnut lamprey Ichthyomyzon castaneus All lengths

ERSNAL Emerald shiner Notropis atherinoides All lengths

FHCFSS Flathead catfish Pylodictis olivaris ≤ 349 c

FHCFST Flathead catfish Pylodictis olivaris ≥ 350 c

FHMWAL Fathead minnow Pimephales promelas All lengths

FWDMSS Freshwater drum Aplodinotus grunniens ≤ 199 c

FWDMST Freshwater drum Aplodinotus grunniens ≥ 200 c

GDEYAL Goldeye Hiodon alosoides All lengths

GDRHAL Golden redhorse Moxostoma erythrurum All lengths

GDSNAL Golden shiner Notemigonus crysoleucas All lengths

GNSFSS Green sunfish Lepomis cyanellus ≤ 79 c

GNSFST Green sunfish Lepomis cyanellus ≥ 80 c

GZSDSS Gizzard shad Dorsoma cepedianum ≤ 179 c

GZSDST Gizzard shad Dorsoma cepedianum ≥ 180 c

LGPHAL Logperch Percina caprodes All lengths

LMBSSS Largemouth bass Micropterus salmoides ≤ 199 c

LMBSST Largemouth bass Micropterus salmoides ≥ 200 c

LNGRSS Longnose gar Lepisosteus osseus ≤ 409 c

LNGRST Longnose gar Lepisosteus osseus ≥ 410 c

MDDRAL Mud darter Etheostoma asprigene All lengths

MNEYAL Mooneye Hiodon tergisus All lengths

NTPKSS Northern pike Esox lucius ≤ 349 c

NTPKST Northern pike Esox lucius ≥ 350 c

OSSFAL Orangespotted sunfish Lepomis humilis All lengths

QLBKAL Quillback Carpiodes cyprinus All lengths
64

Table 5.1. (Continued)

Code Common name Scientific name Length group (mm) a

RVCSSS River carpsucker Carpiodes carpio ≤ 179 d

RVCSST River carpsucker Carpiodes carpio 180 d

RVSNAL River shiner Notropis blennius All lengths

SGERSS Sauger Sander canadensis ≤ 199 c

SGERST Sauger Sander canadensis 200 c

SHDRAL Slenderhead darter Percina phoxocephala All lengths

SHRHSS Shorthead redhorse Moxostoma macrolepidotum ≤ 149 d

SHRHST Shorthead redhorse Moxostoma macrolepidotum 150 d

SMBFSS Smallmouth buffalo Ictiobus bubalus ≤ 179 d

SMBFST Smallmouth buffalo Ictiobus bubalus 180 d

SMBSSS Smallmouth bass Micropterus dolomieu ≤ 179 c

SMBSST Smallmouth bass Micropterus dolomieu 180 c

SNGRAL Shortnose gar Lepisosteus platostomus All lengths

SNSGAL Shovelnose sturgeon Lepisosteus platostomus All lengths

SNSNAL Sand shiner Notropis stramineus All lengths

STCTAL Stonecat Noturus flavus All lengths

STSNAL Spottail shiner Notropis hudsonius All lengths

SVCBAL Silver chub Macrhybopsis storeriana All lengths

TPMTAL Tadpole madtom Noturus gyrinus All lengths

WLYESS Walleye Sander vitreus ≤ 249 c

WLYEST Walleye Sander vitreus 250 c

WTBSSS White bass Morone chrysops ≤ 149 c

WTBSST White bass Morone chrysops 150 c

WTCPSS White crappie Pomoxis annularis ≤ 129 c

WTCPST White crappie Pomoxis annularis 130 c

WTSKSS White sucker Catostomus commersoni ≤ 149 d

WTSKST White sucker Catostomus commersoni 150 d

YLBHSS Yellow bullhead Ameiurus natalis ≤ 99 c

YLBHST Yellow bullhead Ameiurus natalis 100 d

YWPHSS Yellow perch Perca flavescens ≤ 129 c

YWPHSS Yellow perch Perca flavescens 130 c

a

Superscript letters indicate the source of length-based size designations. b

Bister et al. (2000) does not include black buffalo, but does include the same designation for smallmouth buffalo and 

bigmouth buffalo. This designation was used for black buffalo.

c

Anderson and Neumann (1996)

d

Bister et al. (2000)
65

Table 5.2. Eigenanalysis results for substock-length study groups principal components analysis. 

Axes Eigenvalues

Cumulative percentage of 

study‐group variance explained

1 0.628 63

2 0.170 80

3 0.130 93

4 0.042 97

Table 5.3. Eigenanalysis results for stock-length study groups principal components analysis.

Axes Eigenvalues

Cumulative percentage of 

study‐group variance explained

1 0.688 69

2 0.167 86

3 0.091 95

4 0.034 98

Table 5.4. Eigenanalysis results for study groups without size designations principal components analysis.

Axes Eigenvalues

Cumulative percentage of 

study‐group variance explained

1 0.645 65

2 0.220 87

3 0.099 96

4 0.021 99
66

Acknowledgments

This study was funded by the U.S. Army 

Corp of Engineers as part of the Long Term 

Resource Monitoring Program (LTRMP) with 

program guidance and support provided by 

the U.S. Geological Survey, Upper Midwest 

Environmental Sciences Center (UMESC). The 

data used to prepare this report was collected 

by staff from the Iowa Department of Natural 

Resources, Illinois Natural History Survey, 

Minnesota Department of Natural Resources, 

Missouri Department of Conservation, and 

Wisconsin Department of Natural Resources. 

We thank LTRMP fisheries crews and UMESC 

database management staff, past and present, 

for the invaluable data used to prepare this 

report. We thank B. Gray, B. Johnson, R. Maher, 

C. Theiling, and anonymous reviewers who 

provided constructive criticisms that improved 

this report.

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River Conservation Committee, Rock Island, 

Illinois.

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Committee. 2000. Proceedings of the 

fifty‐sixth annual meeting of the Upper 

Mississippi River Conservation Committee. 

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Committee, Rock Island, Illinois.

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plan for the Upper Mississippi River System 

Long Term Resource Monitoring Program. 

Environmental Management Technical Center, 

Onalaska, Wisconsin, Revised September 

1993. EMTC 91‐P002R. 179 pp. (NTIS # 

PB94‐160199)

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status and trends of the Upper Mississippi 

River System 1998: A report of the Long 

Term Resource Monitoring Program. 

U.S. Geological Survey, Upper Midwest 

Environmental Sciences Center, La Crosse, 

Wisconsin, April 1999. LTRMP 99‐T001. 

236 pp.

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REPORT DOCUMENTATION PAGE Form Approved

OMB No. 0704-0188

Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data 

sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other 

aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and 

Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302, and to the Office of Management and Budget, Paperwork Reduction Project (0704-0188), 

Washington, D.C. 20503

1. AGENCY USE ONLY (Leave blank) 2. REPORT DATE

July 2006

3. REPORT TYPE AND DATES COVERED

4. TITLE AND SUBTITLE Temporal and Spatial Trends in the Frequency of Occurrence, Length-Frequency Distributions, 

Length-Weight Relations, and Relative Abundance of Upper Mississippi River Fish

5. FUNDING NUMBERS

6. AUTHOR(S) Daniel J. Kirby and Brian S. Ickes2

7. PERFORMING ORGANIZATION NAME AND ADDRESS

1

Iowa Department of Natural Resources, 206 Rose Street, Bellevue, Iowa 52031

2

U.S. Geological Survey, Upper Midwest Environmental Sciences Center, 2630 Fanta Reed Road, La Crosse, Wisconsin 54603

8. PERFORMING ORGANIZATION

 REPORT NUMBER

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)

 U.S. Geological Survey 

 Upper Midwest Environmental Sciences Center

 2630 Fanta Reed Road

 La Crosse, Wisconsin, 54603

10. SPONSORING/MONITORING

 AGENCY REPORT NUMBER

 LTRMP 2006-7002

11. SUPPLEMENTARY NOTES

12a. DISTRIBUTION/AVAILABILITY STATEMENT

Release unlimited. Available from National Technical Information Service, 5285 Port Royal Road, Springfield, VA 22161 (1-

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 (1-800-225-3842 or 703-767-9050).

12b. DISTRIBUTION CODE

13. ABSTRACT (Maximum 200 words) 

The Long Term Resource Monitoring Program (LTRMP) collected more than 24,000 fish community samples from six study areas on the Upper Mississippi River System in 

1993–2002. More than three million fish comprised of 136 fish species were collected. These data were used to assess length‐weight relations and size structure of commercial 

(i.e., commercially harvested) and recreational (i.e., recreationally harvested) species, and the distribution, frequency of occurrence, and abundance patterns of commercial, 

nongame (i.e., not commercially or recreationally harvested), and recreational species. Forty-seven species were collected in all six LTRMP study areas, 32 species were 

collected in 4 or 5 study areas, 33 species were collected in 2 or 3 study areas, and 24 species were collected in 1 study area. Spatial differences (i.e., differences among study 

areas) in size structure were more pronounced for commercial species than for recreational species. Rate of gain (increase in log10 weight per unit increase in log10 length) 

was assessed for five species, and was significantly different among study areas for all five species and significantly different among years for four species. Assessment of 

longitudinal-spatial (among study area), lateral-spatial (among aquatic area types) and temporal (among 10 years) patterns in abundance showed that species were most similar 

with respect to temporal variation in abundance, and least similar with respect to longitudinal‐spatial variation in abundance. These fisheries population assessments, derived 

from the spatially and temporally expansive LTRMP dataset, will provide river resource managers with decision support tools for managing UMRS fisheries.

.

14. SUBJECT TERMS

Abundance patterns, fish populations, Illinois River, length‐weight relations, size structure, species richness, Upper Mississippi 

River.

15. NUMBER OF PAGES

 68 pp. .

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.

Temporal and Spatial Trends in the Frequency of Occurrence, Length-frequency Distributions, Length-weight Relationships, and Relative Abundance of Upper Mississippi River Fish 2006-T002