Fish community structure in some naturally acid Florida lakes

FISH COMMUNITY STRUCTURE
IN SOME NATURALLY ACID FLORIDA LAKES

Final Project Report Research Work Order No. 73

Prepared by

Cecil A. Jennings, Daniel E. Canfield, Jr., and Douglas E. Colle
Department of Fisheries and Aquaculture
University of Florida, Gainesville, Florida 32611

June 1990

,,

a-~~

, 10

FISH COMMUNITY STRUCTURE
IN SOME NATURALLY ACID FLORIDA LAKES

By

CECIL ANDRE JENNINGS

A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY

UNIVERSITY OF FLORIDA

MAY 1990

ACKNOWLEDGEMENTS

There are many individuals, among them faculty, staff

and fellow graduate students who provided guidance,

assistance, and comradery during my four years at the

University of Florida. I am extremely grateful to them and

extend many thanks.

Financial support from several sources made my tenure

at the University of Florida possible. Thanks are extended

to the sponsors and administrators of the Graduate Minority

Fellowship Program and the Delores A. Auzenne Fellowship for

Graduate Education for financial support through the first

three years and fourth year, respectively. Thanks are also

extended to the Florida Department of Environmental

Regulation and the U.S. Fish and Wildlife Service, both of

whom provided financial support for my research.

I am extending special thanks to the members of my

graduate advisor committee. Drs. Wiley Kitchens, Dan

Canfield, Carter Gilbert, Frank Nordlie, and Jerome Shireman

always had the time to listen, offer encouragement, advice,

comments, criticisms, and congratulations, as needed. I am

very grateful to Wiley, my graduate advisor, for providing

an environment at the Florida Cooperative Fish and Wildlife

Research Unit which exposed me to learning opportunities not

available in the classroom. My other committee members also

provided similar opportunities, and for that I am grateful.

The field and laboratory portions of this study were

labor intensive and required many hands to complete. In the

early stages of the field work, Judy (Lamia) Ludlow and Doug

Colle helped with finding, evaluating, and sampling

prospective study lakes. Doug also provided technical

advice for assessing age, growth and reproductive success.

Additionally, his timely advice on data management made the

volumes of data collected during the study less formidable.

Assistance provided by Ken Romie, Steve Fisher, and Dennis

Crumby were crucial to the successful completion of the

electrofishing, gillnetting, and limnological sampling.

Mark Hoyer directed the block-net and rotenone sampling, and

provided technical advise regarding aging techniques.

Christie Horsburgh, Mark Jennings, Cary Pickands, Rick

Spratt, and Ron Van Fleet provided assistance in all phases

of the field work. Christie was especially helpful with

computer data entry and verification. Mary Rutter analyzed

the water samples, sometimes with little or no advance

warning that they were forthcoming. Truman Perry, caretaker

of the Ordway Preserve, provided assistance in finding the

lakes on the preserve, and was always willing to lend a hand

as needed. Without the assistance rendered by these

individuals, the successful completion of this project would

iii

almost have been an impossible feat. I am very appreciative

of their efforts and offer them many thanks.

I would also like to express my gratitude to the

following individuals for assistance and advice which

contributed to the successful completion of my work. Dr.

Chuck Cichra of the Department of Fisheries and Aquaculture

offered the use of his microcomputer and modem and for

downloading data files from the NERDC mainframe. Chuck also

provided technical advice on many subjects, including

fisheries statistics, age and growth, and SAS software. Pam

Latham, Dr. Tom Smith, Dr. Carole McIvor, and Steven Linda

helped me through the maze of multivariate statistics. Pam

also helped me get started with SAS programming, and Carole

provided critical reviews of an early draft of this

manuscript. Leonard Pearlstine and John Richardson rendered

assistance with microcomputers. I usually provided the

questions; Leonard and John usually provided the answers. I

am thankful to all these individuals for their assistance.

There are many individuals whose contributions to my

graduate education are less tangible, but no less deserving

of gratitude and acknowledgement. These individuals include

faculty, staff, and students closely associated with the

Coop Unit. They were usually the first to listen, counsel,

encourage, critique, and assist, often without my asking.

They include Dr. H. Franklin Percival, Barbara Fesler, and

Petra Wood. Dr. W. Reid Goforth of the Cooperative Research

Unit Center, Washington, D. C., and-Sebrina Street, formerly

of the Student Records Office, School of Forest Resources

and Conservation, also functioned in much the same fashion.

I am also grateful to Sebrina for her skills in deciphering

the seemingly complex regulations governing the formation of

graduate advisory committees, preliminary exams, and the

ever-changing status of assistantship appointment letters

and fee waivers.

Finally, I would like to express deep appreciation to

my family for their continued encouragement and moral

support. They always told me I could if I wanted to,

regardless of the undertaking. I owe a great debt of

gratitude to my wife, Brenda, whose love, companionship and

moral support keep me going through the hardest times. She

was always there for me, beginning with the stresses of

coursework and preliminary exams, through the many late

nights electrofishing and three-day sampling trips to the

panhandle, to the countless hours spent preparing this

dissertation. Her belief in my abilities carried me through

the times when I was less sure. For this I will always be

grateful.

TABLE OF CONTENTS
Page

ACKNOWLEDGEMENTS ii

LIST OF TABLES ix

LIST OF FIGURES xii

ABSTRACT xv

CHAPTERS

I INTRODUCTION 1
Overview 1
Nomenclature 1
Anthropogenic Acidification .. 2
Biotic Response to Acidification 3
Non-Fish Biota 4
Fish. 8
Mechanisms for Fish Population Losses 10
Direct mortality 10
Reproductive and recruitment failure 11
Naturally Acid Waters 12

II ABUNDANCE, BIOMASS, GROWTH, AND CONDITION OF
SELECTED FISH SPECIES IN SOME NATURALLY
ACID FLORIDA LAKES 15

Introduction 15

Methods .. .16
Lake Selection 16
Fish Sampling 19
Age, Growth and Condition 23
Limnological Sampling .24
Aquatic Macrophyte Sampling .27
Fish Stocking 27
Data Analysis 28

Results 28
Lake Morphometry and Water Chemistry .28
Macrophytes 32
Fish Abundance--Electrofishing 34
Fish Abundance and
Biomass--Gillnetting 59

Page
Total Fish Abundance and
Biomass--Block-netting 59
Condition Factors 67
Age and Growth of Largemouth Bass 73
Fish Stocking 80

Discussion 82
Study Site .. 82
Fish Abundance--Electrofishing 83
Fish Abundance and
Biomass--Gillnetting 88
Fish Abundance and
Biomass--Block-netting 89
Condition Factors .91
Age and Growth of Largemouth Bass 94
Fish Stocking 98

Conclusions .98

III FISH SPECIES DIVERSITY AND ASSEMBLAGE PATTERNS
IN 12 NATURALLY ACID FLORIDA LAKES 100

Introduction 100

Methods 102
Community Analysis 102
Reproduction 103
Data Analysis .104

Results 106
Fish Species Diversity 106
Fish Assemblage Patterns .112
Environmental Water Chemistry 122
Reproduction .127

Discussions 133
Species Diversity 133
Fish Assemblage Patterns .136
Environmental Water Chemistry .140
Reproduction 141

Conclusions 143

IV SUMMARY AND CONCLUSIONS 145

Project Summary. 145
Conclusions 151
Future Research Needs 157
Florida .158
Other affected areas. 159

vii

Page

161

APPENDIX

LITERATURE CITED

BIOGRAPHICAL SKETCH

. 163

. 178

viii

LIST OF TABLES

Page

2-1. Location, surface area and mean depth of
study lakes .20

2-2. Means, standard errors, and sample size
of limnological parameters measured in the
study lakes 29

2-3. Abundance of aquatic macrophytes measured in
the study lakes 33

2-4. Total number of fish > 150 mm TL captured,
by species, with electrofishing gear from
the study lakes 35

2-5. Density and biomass estimates (in parenthesis)
and 95% confidence intervals, by species, for
fish > 150 mm TL sampled during the
mark-recapture procedure used on the
study lakes 50

2-6. Density and biomass estimates for largemouth
bass > 150 mm TL sampled during the
mark-recapture procedure, and total
abundance estimates including young-of-the-year
collected during rotenone samples from the
study lakes 53

2-7. Mean density and biomass of fish collected
per experimental gillnet from the study lakes .60

2-8. Total density and biomass estimates of fish
collected per hectare from the study lakes with
rotenone and block-nets 64

2-9. Mean condition factors (KTL) for subadult fish
collected from the study lakes with electrofishing
gear (standard errors in parenthesis) 68

2-10. Mean condition factors (KTL) for adult fish
collected from the study lakes with
electrofishing gear (standard errors in
parenthsis) 69

Pasge

2-11. Mean back calculated length at Age I and months
to adult recruitment (i.e., > 250 mm TL) for
largemouth bass collected from the study lakes 77

2-12. Mean daily growth rates (mm TL/day) tagged
largemouth bass collected from the study lakes 81

2-13. Mean daily growth rates (mm TL/day) of
largemouth bass, by size group, collected
from the study lakes and other Florida lakes .96

3-1. Fish species occurrence in the study lakes
based on electrofishing, experimental gillnets,
and rotenone sampling. Open circles represent
actual occurrence and dashed line represent
species distribution across pH levels 107

3-2. Species richness (number of species/lake)
and Shannon-Weaver index (H') of species
diversity for the study lakes 109

3-3. Species composition of the four fish assemblage
patterns as indicated by cluster analysis 119

3-4. Results of discriminant function analysis of
water chemistry data showing group means of
individual variables 123

3-5. Results of discriminant function analysis of
water chemistry data, listing multivariate
statistics and F approximations 124

3-6. Results of canonical discriminant analysis,
listing canonical correlation, eigenvalues,
and total canonical structure of the three
canonical variates derived from the analysis 125

3-7. Documented (D) and undocumented (ND) occurrence
of young-of-the-year fish collected by
electrofishing, experimental gillnets, and
rotenone sampling for all species in each lake 128

3-8. Minimum pH values in the 12 study lakes in which
adults and young-of the-year were collected. 130

Page
4.1. Summary of the major parameters measured
for fish populations in the study lakes and
the environmental factors) implicated as
strongly influencing each parameter 149

A-1. The physiographic districts and subdivisions
where the 12 study lake are located 162

LIST OF FIGURES
Page

2-1. Location of the three geographic regions
considered to be sensitive to further
acidification 18

2-2. Relative abundance of fish species collected with
electrofishing gear from Gobbler Lake, Florida 37

2-3. Relative abundance of fish species collected
with electrofishing gear from Lawbreaker Lake,
Florida 38

2-4. Relative abundance of fish species collected with
electrofishing gear from Lake Barco, Florida 39

2-5. Relative abundance of fish species collected with
electrofishing gear from Crooked Lake, Florida 40

2-6. Relative abundance of fish species collected with
electrofishing gear from Deep Lake, Florida. 41

2-7. Relative abundance of fish species collected with
electrofishing gear from Lake McCloud, Florida 42

2-8. Relative abundance of fish species collected
with electrofishing gear from Turkey Pen Pond,
Florida 43

2-9. Relative abundance of fish species collected with
electrofishing gear from Lofton Ponds, Florida 44

2-10. Relative abundance of fish species collected
with electrofishing gear from Lake Tomahawk,
Florida 45

2-11. Relative abundance of fish species collected
with electrofishing gear from Brock Lake,
Florida 46

2-12. Relative abundance of fish species collected
with electrofishing gear from Lake Suggs,
Florida 47

xii

Page

2-13. Relative abundance of fish species collected
with electrofishing gear from Moore Lake,
Florida 48

2-14. Mark-recapture estimates and 95% upper limits of
adult (> 250 mm TL) and subadult (150-249 mm TL)
largemouth bass densities in the 10 study lakes
where the species occurred 56

2-15. Relationship between mean density and biomass of
fish collected per experimental gillnet from the
study lakes and lake pH 61

2-16. Relationship between mean density and biomass of
fish collected per experimental gillnet from the
study lakes and lake total alkalinity 62

2-17. Relationship between mean density and biomass of
fish collected per experimental gillnet from
the study lakes and lake chlorophyll a
concentrations 63

2-18. Relationship between total density and biomass
estimates of fish collected per hectare from
the study lakes with rotenone and block-nets
and lake pH 65

2-19. Relationship between total density and biomass
estimates of fish collected per hectare from
the study lakes with rotenone and block-nets
and lake total alkalinity 66

2-20. Relationship between mean condition factors
(KTL) for adult largemouth bass collected from
the study lakes with electrofishing gear and
the width of lake littoral zone 74

2-21. Relationship between mean condition factors
(KTL) for adult largemouth bass collected from
the study lakes with electrofishing gear and lake
total nitrogen concentrations 75

2-22. Relationship between mean back calculated
length at Age I for largemouth bass collected
from the study lakes and lake pH and total
alkalinity 78

2-23. Relationship between months to adult
recruitment (i.e., > 250 mm TL) for largemouth
bass and lake pH and total alkalinity 79

xiii

Page

3-1. Fish species richness (number of species per
lake) in relation to mean lake pH for the 12
study lakes 110

3-2a. Fish species richness (number of species per
lake) in relation to lake area for the 12
study lakes 111

3-2b. Fish species richness (number of species per
lake) in relation to lake area for 11 study
lakes, excluding Lake Suggs 111

3-3. Fish species richness (number of species per
lake) in relation to lake total alkalinity for
the 12 study lakes. 113

3-4. Fish species richness (number of species per
lake) in relation to lake total nitrogen for
the 12 study lakes. 114

3-5. Shannon-Weaver index (H') of fish species
diversity in relation to lake pH and total
alkalinity in the nine study lakes sampled with
block-nets and rotenone. 115

3-6. Shannon-Weaver index (H') of fish species
diversity in relation to the areal coverage of
aquatic vegetation in the nine study lakes
sampled with block-nets and rotenone 116

3-7. Cluster dendrogram showing similarities in
fish assemblage patterns based on the
presence/absence data matrix of the 33 species
collected from the 12 study lakes. .117

3-8. Graphical representation of the distribution
of the four lake groups along the first and
second canonical variates derived from lake
water chemistry data 126

xiv

Abstract of Dissertation Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Doctor of Philosophy

FISH COMMUNITY STRUCTURE
IN SOME NATURALLY ACID LAKES

By

Cecil Andre Jennings

May 1990

Chairperson: Wiley M. Kitchens
Major Department: Forest Resources and Conservation
(Fisheries and Aquaculture)

This study investigated the status of fish communities

in 12 naturally acid Florida lakes. The small, shallow

lakes were located in the Ocala National Forest, the Trail

Ridge, and panhandle Florida; regions where lakes have low

acid neutralizing capacities and are considered sensitive to

further acidification from anthropogenic sources.

Fifteen species from seven families were captured

during mark-recapture sampling. Warmouth (Lepomis qulosus)

was the only cosmopolitan species in the study. Bluegill

(Lepomis macrochirus) and largemouth bass (Micropterus

salmoides), collected from 11 and 10 lakes, respectively,

were also widely distributed species. Total fish abundance

and biomass were not related to lake pH or total alkalinity.

Condition factors for fish in this study were

comparable to published values. Condition factors of the

sportfishes bluegill and largemouth bass were not related to

lake pH or total alkalinity. Daily growth rates of Age I

and older largemouth bass in all but one study lake were

equivalent to literature values for Florida systems with pH

values > 5. Back-calculated length at Age I and months to

adult recruitment were below published values for the

species.

Fish species richness and the Shannon-Weaver index (H')

of species diversity were not related to lake pH, but were

significantly correlated with total nitrogen concentrations

and to the areal coverage of aquatic macrophytes,

respectively.

Classification analysis suggested four fish

assemblages, with each having consistent patterns of species

composition. The four assemblages patterns ranged from

species poor to species rich, with a shared core-group of

species. Discriminant analyses of the limnological data

indicated that the differences among lake groups were not

significant. Fish assemblage patterns appear to be

influenced more by lake isolation (i.e., degree of

connectedness) than by lake pH.

Fish reproduction in the study lakes seems not to be

affected by lake pH. At least sixteen fish species

successfully reproduced in the acid conditions (i.e., 4.1 -

xvi

5.7) found in the study lakes. Mahy of these species,

including the sportfishes largemouth bass and bluegill

reproduced well below previously reported minimum values for

the species.

xvii

CHAPTER 1
INTRODUCTION

Overview

The research findings presented in this dissertation

are organized into two main chapters. Introductory and

summary chapters are also included. The introductory

chapter contains notes on the nomenclature used in the

manuscript, a brief literature review of the causes and

consequences of anthropogenic acidification, and general

project objectives. In chapter two, consideration is given

to measures of fish populations such as relative abundance,

density, biomass, and condition. This treatment is limited

to species > 150 millimeters Total Length (mm TL), the

minimum size used in the mark-recapture portion of the

study. In chapter three, emphasis is placed on fish

communities (i.e., all species collected), including fish

assemblage patterns, measures of species diversity, and an

assessment of fish reproductive success. The final chapter

contains a general summary of chapters two and three, a

discussion of research findings, and suggestions of other

avenues for further investigation.

Nomenclature

The freshwater fish fauna of peninsula Florida has a

relatively high percentage of endemism at the species,

subspecies, and racial levels (Gilbert 1987). Some species

1

CHAPTER 1
INTRODUCTION

Overview

The research findings presented in this dissertation

are organized into two main chapters. Introductory and

summary chapters are also included. The introductory

chapter contains notes on the nomenclature used in the

manuscript, a brief literature review of the causes and

consequences of anthropogenic acidification, and general

project objectives. In chapter two, consideration is given

to measures of fish populations such as relative abundance,

density, biomass, and condition. This treatment is limited

to species > 150 millimeters Total Length (mm TL), the

minimum size used in the mark-recapture portion of the

study. In chapter three, emphasis is placed on fish

communities (i.e., all species collected), including fish

assemblage patterns, measures of species diversity, and an

assessment of fish reproductive success. The final chapter

contains a general summary of chapters two and three, a

discussion of research findings, and suggestions of other

avenues for further investigation.

Nomenclature

The freshwater fish fauna of peninsula Florida has a

relatively high percentage of endemism at the species,

subspecies, and racial levels (Gilbert 1987). Some species

1

CHAPTER 1
INTRODUCTION

Overview

The research findings presented in this dissertation

are organized into two main chapters. Introductory and

summary chapters are also included. The introductory

chapter contains notes on the nomenclature used in the

manuscript, a brief literature review of the causes and

consequences of anthropogenic acidification, and general

project objectives. In chapter two, consideration is given

to measures of fish populations such as relative abundance,

density, biomass, and condition. This treatment is limited

to species > 150 millimeters Total Length (mm TL), the

minimum size used in the mark-recapture portion of the

study. In chapter three, emphasis is placed on fish

communities (i.e., all species collected), including fish

assemblage patterns, measures of species diversity, and an

assessment of fish reproductive success. The final chapter

contains a general summary of chapters two and three, a

discussion of research findings, and suggestions of other

avenues for further investigation.

Nomenclature

The freshwater fish fauna of peninsula Florida has a

relatively high percentage of endemism at the species,

subspecies, and racial levels (Gilbert 1987). Some species

1

such as largemouth bass (Micropterus salmoides), and

bluegill (Lepomis macrochirus) have distinctive subspecies

(i.e., M. s. floridanus and L. m. mystacalis) which are

restricted to peninsular Florida (Gilbert 1987).

Subspecific populations of these same species ( i.e., M. s.

salmoides and L. m. macrochirus) are known to occur in

panhandle Florida (C.R. Gilbert, pers. comm.). Intergrades

between two subspecies of pickerel; redfin pickerel (Esox

americanus americanus) and grass pickerel (E. a.

vermiculatus) are also known to occur in Florida (Crossman

1966). The lakes in this study were located in both

peninsula and panhandle Florida; therefore, fish collected

from the study lakes probably included different subspecies

of the same fish, and subspecific intergrades.

Consequently, taxonomic references in this dissertation will

be limited to species level identification. The subspecies

of mosquitofish (Gambusia affinis holbrooki) which occurs

east of the Mobile Bay, Alabama, has recently been

recognized as a distinct species, G. holbrooki; therefore,

mosquitofish collected from the study lakes are identified

as G. holbrooki (Wooten et al. 1988).

Anthropogenic Acidification

Acid rain is a catch-all term used to describe

precipitation that has a pH lower than 5.6 (distilled water,

equilibrated to atmospheric carbon dioxide, has a pH of 5.6)

(Haines 1981). Acid precipitation is primarily caused by

anthropogenic emission of nitrogen-and sulfur oxides, which

are byproducts of industrial processes, electrical power

generation, and the combustion of fossil fuels (Gorham

1976). In the atmosphere, nitrogen and sulfur oxides

combine with water vapor to form acid vapors. Condensation

of acid vapors results in acid precipitation (e.g., rain,

snow, and fog).

Anthropogenic acid precipitation has probably been

occurring on a small scale since the industrial revolution.

Industrial emissions were suspected of affecting human and

plant health in and around industrial centers in 17th

century England (Cowling 1982). However, it wasn't until

the mid 1960s that acid rain was recognized as a regional

phenomenon that reportedly had drastic affects in northern

Europe, Canada and the northeastern United States (Wright

and Gjessing 1976). More recently, acid precipitation has

also been reported from the southeastern United States

(Haines 1979; Brezonik et al. 1983). The reports of

cultural acidification from northern Europe, the

northeastern United States, and Canada were usually followed

by reports of drastic changes in the population structures

of lake biota.

Biotic Response to Acidification

In general terms, acid precipitation and the subsequent

acidification of aquatic ecosystems are viewed as harmful to

the biota in these systems. However, aquatic organisms

appear not to be uniformly affected by cultural

acidification. In some instances, both empirical and

experimental evidence suggest that certain species are more

affected than others. In other instances, the empirical and

experimental evidence offer differing accounts of species

response to low pH conditions. The following review

presents evidence for and against cultural acidification as

a process that adversely affects biotic communities.

Non-Fish Biota

Field and laboratory studies on the effects of

acidification on decomposers in Norwegian waters found a

shift in dominance from bacteria to fungi and a subsequent

reduction in the decomposition rates of detrital matter when

water pH was below 6.0 (Hendrey et al. 1976; Leivestad et

al. 1976). Similar results were also reported by Traaen

(1980). However, Schindler (1980) and Muller (1980) found

no evidence of reduced decomposition rates in a 27 hectare

Canadian lake that they intentionally acidified to a pH of

5.2. Other studies on the effects of acidification on

decomposers also show similar discrepancies (see review by

Haines 1981). Changes in microbial populations resulting

from differences in sample collection and analysis are

probably responsible for the conflicting results (Haines

1981).

Reports of the effects of lake pH on phytoplankton,

periphyton and macrophyte species composition also show

conflicting results. Many empirical and experimental

studies have reported that phytoplankton species richness

decreased as lake pH declined (Hendrey et al. 1976;

Leivestad et al. 1976; Almer et al. 1978; Yan and Stokes

1978; Muller 1980). However, while some species disappeared

with increased acidity, the biomass of the remaining species

often increased (Hendrey et al. 1976; Leivestad et al.

(1976). Reductions in microbial and invertebrate

heterotrophic activity probably accounts for the increased

biomass of the remaining species (Haines 1981). On the

other hand, there were no changes in the number of

phytoplankton species in an experimentally acidified

Canadian lake (Schindler 1980). Furthermore, despite the

tendency toward a reduction in species richness,

phytoplankton production and biomass in acidic lakes may be

similar in acid and non-acid lakes with similar phosphorus

levels (Hendrey et al. 1976; Leivestad et al. 1976; Almer et

al. 1978; Yan and Stokes 1978; Haines 1981). Similar

results were also reported by Shearer et al. (1987).

The response of planktonic and benthic invertebrates to

acidification appears to be similar to that of decomposers

and primary producers. The available evidence include

reports which found relationships between invertebrate

species richness and biomass with lake pH, and reports which

did not. Generally, the response of invertebrate

communities to acidification appear to be group related.

Roff and Kwiatkowski (1977), Almer et al. (1978), Yan

and Stokes (1978), and Haines (1981) all reported that

zooplankton biomass was lower in acid than in non-acid

lakes. Hendrey and Wright (1976), Almer et al. 1978, and

Yan and Stokes (1978) also reported that zooplankton species

richness decreased as lake acidity increased. Conversely,

there are studies which suggest that zooplankton biomass in

unrelated to lake pH. For example, Kettle et al. (1987)

reported that the vertical distribution of three zooplankter

species in a Canadian lake was influenced more by the

vertical distribution of the phytoplankton community (i.e.,

zooplankton prey base) than by lower pH of the epilimnetic

waters. Canfield (1983b) also reported that zooplankton

communities in 165 acid and non-acid Florida lakes seemed to

be influenced more by phosphorous and nitrogen

concentrations than by lake pH.

Haines (1981) suggested that mollusks do not do well in

acid environments because they have a high CaC03 requirement

for shell formation. Leivestad et al. (1976) and Almer et

al. (1978) noted that some crustacean species were not found

in Scandinavian lakes with a pH of 6.0 or below. Fryer

(1980) noted that on the Isle of Rhum, the number of

crustacean species decreased as lake acidity increased, but

suggested that other factors such as low calcium

concentrations may also play a part in the exclusion of

certain species.

Aquatic insects have shown differing responses to

acidification. Species of Ephemeroptera and Plecoptera

decline as lake pH declines, and 10 of 22 species of in

Norwegian lakes were highly correlated with lake pH (Hendrey

and Wright 1976). Similar results have been reported from

England (Sutcliffe and Carrick 1973), and Ontario, Canada

(Scheider and Dillon 1976). Under experimental laboratory

conditions, Ephemeroptera were intolerant of low pH, while

Plecoptera were moderately tolerant of the same conditions

(Bell 1971). Similar results were reported under

experimental field conditions in a New Hampshire stream

acidified from pH > 5.4 to pH 4.0 (Hall and Likens 1980).

While these two groups appear to be adversely affected by

low pH conditions, other groups of aquatic insects

apparently thrive. For example, Coleoptera, Hemiptera and

Megaloptera are more abundant in low pH lakes than in

circumneutral lakes (Raddum 1980). Similar findings have

been reported from Norwegian lakes (Haines 1981). Odonata,

Heteroptera, and some Dipteran also tend to be abundant in

lakes with pH levels between 4.2 to 5.0 (Haines 1981).

These studies imply that some species are more acid-tolerant

than others, and that the more acid-tolerant species benefit

from competitive release when the less acid-tolerant species

disappear. Competitive release may explain why some species

actually expand their numbers with the onset of cultural

acidification.

Fish

Acid precipitation has been suspected of altering

natural fish populations for at least 70 years. The

disappearance of Atlantic Salmon (Salmo salar) from a few

southern Norwegian rivers in the 1920s was attributed to the

low pH of those rivers (Jensen and Snekvik 1972). The

decline has continued to the point where the catch of

Atlantic salmon in those rivers is now nearly zero (Haines

1981). Populations of roach (Rutilus rutilus) were severely

reduced in some Swedish lakes in the 1930s, as were pike

(Esox lucius) in the 1940s, and perch (Perca fluviatilis)

and eel (Anquilla anquilla) in the 1950s (Harvey 1982).

These loses were blamed on cultural acidification (Harvey

1982). The disappearance of populations of lake trout

(Salvelinus namaycush), lake herring (Coreqomus artedii),

white suckers (Catostomus commersoni), and other fish

species from lakes in the La Cloche Mountains in Ontario,

Canada, was attributed to increasing anthropogenic acidity

(Beamish and Harvey 1972). Increased anthropogenic acidity

was also suspected of eliminating entire fish communities,

including brook trout (Salvelinus fontinalis), lake trout,

white sucker, brown bullhead (Ictalurus nebulosus), and

several cyprinids from lakes in the Adirondack Mountains of

New York, USA over a 40-year period (Schofield 1976).

The evidence of drastic reductions in fish populations

which are correlated with reductions in water pH comes

primarily from empirical evidence. Despite what seems like

clear evidence of anthropogenic acidification drastically

reducing fish population, this is apparently not always the

case. Many authors have acknowledged that population losses

are sometimes partial, and that the remaining species often

expand their numbers and show increased growth as other

species are lost.

For example, brown trout, roach, and perch from

acidified waters (pH 4.4 to 6.0) often showed larger size at

age than fish from neutral waters (pH 6.5 to 7.0) (Harvey

1982). In the La Cloche Mountain lakes of Ontario, Canada,

populations of yellow perch (Perca flavescens), pumpkinseed

(Lepomis gibbosus), lake herring, bluegill, lake whitefish

(Coregonus clupeaformis), and brown bullhead appear not to

be affected down to pH level 5.0 (Harvey 1980). In another

study, the abundance of lake trout and white sucker

increased in the early stage of the experimental

acidification of Lake 223, in the Experimental Lakes Area of

Ontario, Canada (Mills et al. 1987). During the same time,

lake trout growth remained constant, but white sucker growth

increased. Although the growth rates of these two species

were eventually reduced, the reductions were attributed to a

scarcity of food organisms and not to the experimental

acidification of the lake (Mills et al. 1987). Gunn et al.

(1988) also studied fish populations from 20 Canadian lakes

thought to be sensitive to acidification. They reported

that many of the lakes contained fish species considered to

be sensitive to low pH, and that species richness in these

lakes was related to lake area, and not to lake pH.

Estimated densities and biomass of all major species were

similar to reported values from other lakes in the same

area, and both lake trout and brown trout (Salmo trutta)

successfully spawned in these lakes, despite episodes of

acid runoff. Based on these findings, Gunn et al. (1988)

concluded that the fish populations in these lakes did not

exhibit anomalous population characteristics such as loss of

species, reduced densities or biomass, or recruitment

failure that could be related to acidification.

Mechanisms for Fish Population Losses

Direct mortality

The primary mechanisms responsible for the loss of fish

from culturally acidified waters seem to be sudden mortality

of adults over a short period of time, and gradual

recruitment failure over a longer period of time. Acute

mortality of fish in acid waters occurs primarily in

streams, usually in association with episodic events (i.e.,

heavy autumn rains or snow melt) which rapidly reduce stream

pH (Haines 1981). The physiological mechanisms involved in

acid-induced mortality appear to be ion-regulatory failure,

asphyxiation, or elevated heavy metal concentrations in

conjunction with low pH (Schofield 1976; Muniz and Leivestad

1980; Haines 1981).

Black bullheads (Ictalurus melas) exposed to low pH

waters exhibited swelling between outer gill lamellar and

remaining tissue, erosion of the lamellae, and swelling of

the gill filaments (McKenna and Duerr 1976). Such gill

damage impairs respiratory, excretory and liver functions,

which eventually causes death in the afflicted fish (Haines

1981). Brown trout exposed to toxic levels of aluminum (900

Ag/L) at varying pH levels (4.0 to 6.0), experienced the

maximum loss of plasma salts at pH 5.0 (Muniz and Leivestad

1980). In addition to ion loss (i.e. plasma salts), brown

trout also exhibited severe mucus clogging of the gills,

hyperventilation, and respiratory stress (Muniz and

Leivestad 1980). These physiological stresses are probably

the mechanisms by which fish succumb to high aluminum levels

in low pH waters.

Reproductive and recruitment failure

Adult fish are more resistant to the effects of low pH

than any of the other life history stages (Haines 1981).

Thus, it is likely that population losses in acid waters are

due to reproductive and recruitment failure rather than

direct mortality of adult fish (Beamish and Harvey 1972;

Beamish et al. 1975; Fritz 1980; Haines 1981; Harvey 1982).

Reproductive failure may be brought about by many

mechanisms, including a cessation of spawning behavior (Daye

and Garside 1975; Fritz 1980), avoidance of suitable

spawning areas because of low pH (Johnson and Webster 1977;

Fritz 1980), gamete development failure, suspension of

embryonic development, and deformed larvae (Fritz 1980).

Beamish et al. (1975) found 1-er than expected calcium

levels in the ovaries of maturing females in acid waters,

and suggested that the ova of the affected fish may not

develop properly. Fritz (1980) noted that developing fish

are influenced by environmental factors such as temperature

and salinity, and suggested that low pH and calcium levels

may have been responsible for deformities that Beamish

(1972) observed in some fish from acid waters.

If successful spawning occurs, populations may still be

lost through the failure of younger age classes to recruit

into the adult population. Haines (1981) suggested that

larval and juvenile fish are more susceptible to low pH than

any other life history stage. Beamish and Harvey (1972) and

Harvey (1980) reported that most of the fish populations

they surveyed in acid lakes contained mainly older

individuals, with few juveniles present. Such an age-class

structure suggests that fish populations would eventually be

lost as the older fish die and are not replaced by younger

individuals.

Naturally Acid Waters

Records at the Academy of Natural Sciences of

Philadelphia indicate that the existence of naturally

occurring acid (pH < 6.0) lakes in the U.S. has been known

at least since the late 1800s (Patrick et al. 1981). One

such lake, Lake Annie, in Highlands County, Florida has

probably been acidic for the past 40,000 years (Crisman

1984). Naturally occurring acid waters occur in several

areas of the United States, including Wisconsin (Rahel 1982;

Wiener 1983), Maine (Haines et al. 1986), Vermont (Haines et

al. 1986), New Jersey (Hastings 1979; Patrick et al. 1979)

and Florida (Meehean 1942; Crisman et al. 1980; Schulze

1980; Canfield 1983b; Canfield et al. 1983b; Crisman 1984;

Keller 1984; Canfield et al. 1985; Williams et al. 1985).

These lakes generally occur in regions with high rainfall

and unproductive bedrock (Patrick et al. 1981; McWilliams et

al. 1980) or in areas where the substrate is mostly sand

(Patrick et al. 1981). Typically, these lakes have no

external drainage, and many are associated with swamps and

marshes (Rahel 1982; Wiener 1983; Williams et al. 1985).

Literature describing life histories and community

dynamics of the biota in naturally occurring acid systems is

rare. However, many such lakes do support algae,

crustaceans, insects, and fish, suggesting that biota in

these lakes have probably adapted to the low pH conditions

(Patrick et al. 1981). Lake Annie, a 40,000-year-old acid

lake in Highlands County, Florida, contains subfossil

chironomids and cladocerans of the same genera that are

common components in today's naturally acid lakes (Crisman

1984). Surviving fish populations have also been reported

from isolated (i.e., seepage) acid pools in the Pine Barrens

of New Jersey Cope (1896). Biotic communities have also

been reported from acid waters in Wisconsin (Rahel 1982;

Wiener 1983), Maine (Haines et al. 1986), Vermont (Haines et

al. 1986), New Jersey (Hastings 1979; Patrick et al. 1979),

and Florida (Meehean 1942, Crisman et al. 1980; Schulze

1980; Canfield 1983b; Crisman 1984; Keller 1984; Canfield et

al. 1985; Williams et al. 1985).

The existence of naturally occurring acid waters which

support self-sustaining biotic communities suggests that

lake pH may not be adversely affecting the respective biotic

communities. There are many such lakes in Florida, many of

which may be sensitive to further acidification because of

low acid neutralizing capacities (Canfield 1983b). Some of

these poorly buffered, acid lakes in northcentral Florida

have already been influenced by acid precipitation, but the

impact has been slight, averaging 0.5 pH units over the past

20 years (Crisman et al. 1980).

In this dissertation, I present the results of an

investigation into fish community structure and population

dynamics in 12 naturally acid Florida lakes. The general

objectives of this research were to 1) quantify aspects of

the population dynamics of selected species, 2) characterize

species distribution and associations, and 3) quantify

relationships between species distribution, and population

dynamics to the morphoedaphic factors in the study lakes.

~- CHAPTER 2--
ABUNDANCE, BIOMASS, GROWTH, AND CONDITION
OF SELECTED FISH SPECIES
IN SOME NATURALLY ACID FLORIDA LAKES

Introduction

Florida has the highest percentage of acid lakes in the

eastern United States (Linthurst et al. 1986). Many of

these lakes may be sensitive to further acidification

(Canfield 1983b), and may be threatened due to increased

acidity of Florida's rainwater (Brezonik et al. 1983).

Public concerns about the sensitivity of Florida's softwater

lakes to further acidification are based in part on the

potential for losses in fishery resources. There are many

reports of significant reductions in, or complete losses of

fish populations from areas in the northeastern United

States, Canada, and Northern Europe where cultural

acidification has occurred (Haines 1981). Currently, there

are no published accounts of major losses of fish

populations from Florida's acid lakes, and published

accounts of fish population dynamics in Florida's most

sensitive waters are rare.

The available fisheries literature from Florida's acid

lakes documents the existence of reproducing fish

populations. The early studies surveyed species

assemblages, and the abundance and biomass of the fish

~- CHAPTER 2--
ABUNDANCE, BIOMASS, GROWTH, AND CONDITION
OF SELECTED FISH SPECIES
IN SOME NATURALLY ACID FLORIDA LAKES

Introduction

Florida has the highest percentage of acid lakes in the

eastern United States (Linthurst et al. 1986). Many of

these lakes may be sensitive to further acidification

(Canfield 1983b), and may be threatened due to increased

acidity of Florida's rainwater (Brezonik et al. 1983).

Public concerns about the sensitivity of Florida's softwater

lakes to further acidification are based in part on the

potential for losses in fishery resources. There are many

reports of significant reductions in, or complete losses of

fish populations from areas in the northeastern United

States, Canada, and Northern Europe where cultural

acidification has occurred (Haines 1981). Currently, there

are no published accounts of major losses of fish

populations from Florida's acid lakes, and published

accounts of fish population dynamics in Florida's most

sensitive waters are rare.

The available fisheries literature from Florida's acid

lakes documents the existence of reproducing fish

populations. The early studies surveyed species

assemblages, and the abundance and biomass of the fish

communities in these lakes (Meehean 1942; Dickinson 1948).

More recently, several authors investigated selected aspects

of fish biology (Schulze 1980; Keller 1984; Canfield et al.

1985; Lamia 1987) and population ecology (Keller 1984; Lamia

1987) in low pH conditions. This sparse literature suggests

that factors other than lake pH, such as lake productivity,

may be influencing fish population dynamics in Florida's

naturally acid lakes.

This chapter presents results of an investigation into

the population dynamics of selected fish species, primarily

the sportfishes, largemouth bass and bluegill, from 12

naturally acid Florida lakes. The primary objective of this

inquiry was to test the hypothesis that sportfish abundance

and biomass in the study lakes were not related to lake pH.

Other objectives were to 1) determine the relative

abundance, density, biomass, and condition of selected

species in the study lakes, 2) determine the growth of

largemouth bass in the study lakes and 3) quantify any

relationships that may exist between the abundance, density,

biomass, condition, and growth of selected species and lake

morphoedaphic factors.

Methods

Lake Selection

Many factors contributed to the selection of the 12

study lakes. Initially, personnel from the Florida

Department of Environmental Regulation, the U.S.

communities in these lakes (Meehean 1942; Dickinson 1948).

More recently, several authors investigated selected aspects

of fish biology (Schulze 1980; Keller 1984; Canfield et al.

1985; Lamia 1987) and population ecology (Keller 1984; Lamia

1987) in low pH conditions. This sparse literature suggests

that factors other than lake pH, such as lake productivity,

may be influencing fish population dynamics in Florida's

naturally acid lakes.

This chapter presents results of an investigation into

the population dynamics of selected fish species, primarily

the sportfishes, largemouth bass and bluegill, from 12

naturally acid Florida lakes. The primary objective of this

inquiry was to test the hypothesis that sportfish abundance

and biomass in the study lakes were not related to lake pH.

Other objectives were to 1) determine the relative

abundance, density, biomass, and condition of selected

species in the study lakes, 2) determine the growth of

largemouth bass in the study lakes and 3) quantify any

relationships that may exist between the abundance, density,

biomass, condition, and growth of selected species and lake

morphoedaphic factors.

Methods

Lake Selection

Many factors contributed to the selection of the 12

study lakes. Initially, personnel from the Florida

Department of Environmental Regulation, the U.S.

Environmental Protection Agency, and KNB Engineering and

Applied Sciences of Gainesville, Florida, selected potential

study lakes from the population of lakes sampled by the U.S.

Environmental Protection Agency during Phase I (Eastern

Lakes Survey) of the National Surface Water Survey

(Linthurst et al. 1986). Four lakes from each of three

geographic regions considered to be sensitive to

acidification comprised the original population of study

lakes. Lakes in these regions are considered sensitive to

further acidification because they typically have low acid

neutralizing capacities. The general geographic regions of

interest were the Florida panhandle, the Trail Ridge of

north Florida, and the Ocala National Forest in northcentral

Florida (Figure 2-1). A more precise listing of the

physiographic regions where the study lakes occurred is

presented in Table A-1.

Onsite inspection of prospective study lakes indicated

that many could not be sampled. Some of the lakes were

located on the Camp Blanding Military Reserve and could not

be sampled due to scheduled military exercises. Other lakes

were either on private property whose owners would not grant

permission to sample the lake, were inaccessible by truck,

or had dried up due to drought conditions. Crooked Lake and

Lake Tomahawk in the Ocala National Forest, and Lofton

Ponds, Moore Lake, and Turkey Pen Pond in the Florida

panhandle were the only lakes from the original list of

potential study lakes that could be sampled. Personnel from

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the Department of Fisheries and Aquaculture recommended

several substitute study lakes from the geographic regions

of interest. The lake selection committee accepted Gobbler

and Lawbreaker lakes in the Ocala National Forest, and lakes

Deep, McCloud, Barco and Suggs in the Trail Ridge. Curtis

E. Watkins of the Florida Department of Environmental

Regulation selected Brock Lake in Washington County as the

final study lake (Table 2-1).

Fish Sampling

Intensive fisheries sampling on the study lakes began

in March 1987 and continued through December 1988. Fish

were collected by use of electrofishing gear, experimental

gillnets, and fish toxicants. The electrofishing boat was

equipped with a 5 kilowatt portable generator and Coffelt

VVP-15 or Coffelt VVP-20-4000 electrofishing unit. The

experimental gillnets were 50 m long, with each net having

five 10 m panels with different sized mesh (i.e., 19, 25,

38, 51, and 76 mm stretched mesh). The fish toxicant

rotenone, at 5% active concentration, was used in

conjunction with 0.08 hectare block-nets (1 cm stretched

mesh) during the summers of 1987 and 1988.

Pulsed alternating current was used to collect fish

samples from the littoral areas of the study lakes during

daytime and nighttime sampling periods. Each fish collected

was identified to species, measured, weighed, marked, and

released. Fish > 150 millimeter total length (mm TL), were

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measured to the nearest mm TL, weighed to nearest gram (g),

and marked with a pelvic fin clip or pectoral spine clip.

Largemouth bass were also marked with a numbered Floy tag.

Population size was estimated for selected species (i.e.,

species large enough to be marked, with enough marked

individuals to allow subsequent recaptures) with Chapman's

modification of the Schnabel formula for population

estimation using multiple censuses (Ricker 1975). This

formula follows the form

N = E (Ci M) / R + 1

where Ci is the catch at the ith interval, MK is the number

marked at large during the ith interval, and R is the total

number of recaptures. Confidence intervals were calculated

according to Ricker (1975). Population density and biomass

estimates were calculated using equations A and B,

respectively.

A. D = / A

B. B = (R MW) / A

where D is the estimated density of individuals per hectare, N

is estimated population size, A is the area of the lake in

hectares, B is the estimated biomass of individuals per

hectare, and MW is the mean weight per individual of the

species. Confidence intervals for density and biomass were

calculated by replacing the value of N in equations A and B

above with the value of the upper and lower confidence limit

of the populations of interest, as calculated using the

Modified Schnabel formula.

Experimental gillnets were also used to assess relative

fish abundance in the study lakes. Four experimental

gillnets were fished along the bottom of each lake once

during each quarter for the duration of the study. One

gillnet set was made perpendicular to the north, south, east

and west shores of each study lake, and fished along the

bottom for approximately 24 hours. All fish caught were

separated by species, divided into successively larger 40 mm

TL size groups, enumerated, and weighed by species and size

group. Length-weight relationships calculated from the

electrofishing data provided reliable weight estimates for

all decomposed or partially eaten fish found in the

gillnets.

Nine of the 12 study lakes were sampled with rotenone.

Other considerations prohibited the use of this sampling

method in the three remaining lakes. Gobbler Lake was

inaccessible to the large boats used to carry the block-

nets, Lake McCloud was the site of ongoing experiments that

would be jeopardized by the use of rotenone, and Brock Lake

supported a fee-fishery that would be damaged with the

introduction of rotenone to the lake. Two 0.08 hectare

block-nets were set in both the littoral and limnetic zones

of each lake, and were sampled according to Shireman et al.

(1981). Briefly, this process included setting out the

block-nets, applying rotenone, and dipnetting fish as they

come to the surface. Dead fish were collected inside the

block-nets for an additional two days after the initial

rotenone application. Density and biomass estimates were

calculated for each fish species in each net, and weighted

by the extent of the habitat (i.e., percentage of total) to

obtain whole-lake estimates.

Age, Growth and Condition

Growth rates of largemouth bass were calculated from

recaptured tagged specimens and from otoliths removed from

largemouth bass killed during gillnetting or rotenone

sampling. Whole otoliths, measured according to Hoyer et

al. (1985), were used to back-calculate lengths at age.

Lengths at age were calculated using the Bagenal and Tesch

(1978) modification of the direct proportion method of back-

calculating lengths at age. The modified formula follows

the form

Log LI = Log L + b (Log S, Log S)

where Ln is the total length of the fish when the annulus

was formed, L is the total length of the fish at the time

the otolith was taken, S, is radius of the annulus n, S is

the total radius of the otolith, b is the slope of the

otolith radius-body length regression line, and Log refers

to base 10 logarithm (Bagenal and Tesch 1978). Coefficients

of condition (K) for selected species were calculated using

the formula

K = W 100,000 / L3

where K is the coefficient of condition, W is the weight of

the fish in grams, and L is the total length of the fish in

millimeters (Anderson and Gutreuter 1983).

Limnological Sampling

Lake surface areas and shoreline lengths were

calculated using Florida Department of Transportation aerial

photographs (1:24,000 scale), and a planimeter and

cartometer, respectively. A boat-mounted Raytheon recording

fathometer was used to make representative bottom tracings

of all lakes except Brock. The tracings were made by

running four to ten transects across each lake, depending on

the size of the lake. Mean depth and coverage of submerged

aquatic macrophytes were calculated from the fathometer

tracings using the methods of Maceina and Shireman (1980).

Water samples were collected from three open water

stations in each of the study lakes. One station in each

lake was located at the deepest point in the lake. The

Trail Ridge and the Ocala National Forest lakes were sampled

10 to 13 times, and the panhandle lakes, except Brock, were

sampled at least six times. Brock Lake was sampled five

times. Water temperature and dissolved oxygen concentration

were measured at the surface (0.5 m) of each station, and at

one meter intervals at the deep station with a Yellow

Springs Instruments (YSI) Model 51a dissolved

oxygen/temperature meter. Water clarity was measured at the

deep station using a 20 cm Secchi disc. Surface (0.5 m)

water samples were collected in acid-washed, triple-rinsed,

1-Liter Nalgene bottles. The water samples were placed on

ice and transported back to the water chemistry laboratory

for analyses by Department of Fisheries and Aquaculture

personnel. The collected water samples were analyzed to

determine pH, total alkalinity, total acidity, specific

conductance, color, and aluminum, chloride, magnesium,

sodium, potassium, sulfate, total nitrogen, total

phosphorus, and chlorophyll a concentrations.

PH was determined within 24 hours of collection with an

Orion Model 601A pH meter calibrated with buffers of pH 4.0,

7.0, and 10.0. Total alkalinity was determined by titration

with 0.02 N H2SO4. To avoid interference from silicates,

phosphorus, and other materials, all titrations were taken

to an endpoint of pH 4.5 (APHA 1985). In low alkalinity

samples, the equivalence point occurs at pH greater than

4.5; therefore, the reported alkalinities may be slightly

higher than the true alkalinities in the study lakes. Total

acidity was determined by titration with 0.02 N NaOH to an

endpoint of pH 8.3 (APHA 1985). Titration endpoints for

total alkalinity and total acidity were determined with the

Orion Model 601A pH meter.

Specific conductance was measured with a YSI Model 31

conductivity bridge. Aluminum concentrations were measured

colorimetrically with Hach AluVer III aluminum reagent (Hach

Chemical Company 1975), and a Perkin Elmer Model 552

spectrophotometer. Chloride concentrations were measured by

titration with 0.0141 N mercuric nitrate. The endpoints

were determined with diphenylcarbazone (Hach Chemical

Company 1975). Total phosphorus concentrations were

determined following the methods of Murphy and Riley (1962),

after a persulfate digestion in a boiling water bath (Menzel

and Corwin 1965). Total nitrogen was determined with a

modification of the Kjeldahl method (Nelson and Sommers

1975).

Water samples were analyzed for color, sulfate, sodium,

calcium, magnesium, and potassium, after filtration through

a Gelman type A-E glass fiber filter. Color was determined

with the platinum-cobalt method and matched Nessler tubes

(APHA 1985). Sulfate concentrations were determined with a

turbidimetric method and SulfaVer IV sulfate reagent (Hach

Chemical Company 1975). Sodium, calcium, magnesium, and

potassium were determined with atomic absorption

spectrophotometry.

The concentration of planktonic algae in each lake was

estimated by measuring chlorophyll a concentrations. A

measured portion of lake water was filtered through a Gelman

type A-E glass fiber filter. The filter was blotted dry,

placed on silica gel desiccant, and frozen for no longer

than two months. Chlorophyll a concentrations were

determined by the methods of Richards and Thompson (1952)

and Yentsch and Menzel (1963). Chlorophyll a values were

calculated using the equations of Parsons and Strickland

(1963). Values were not corrected for pheophytin.

Aquatic Macrophyte Sampling

Aquatic macrophyte abundance was measured on all study

lakes except Brock. Measurement were made following the

methods of Maceina and Shireman (1980). Briefly, this

process includes using a boat mounted fathometer to estimate

the percent of areal coverage, and percent of lake volume

occupied by aquatic vegetation. Ten randomly selected

sampling transects were established around the perimeter of

each lake. The width of the emergent plant zone at each

transect was measured with a calibrated range finder.

Macrophyte biomass was determined from plant samples

collected from within 0.25 m2 quadrats placed in the

submerged, floating-leaved, and emergent plant zones (30

stations per lake). Excess water was removed from the plant

samples, which were then weighed to the nearest 0.10

kilogram fresh weight.

Fish Stocking

Largemouth bass were not present in electrofishing

samples from Lake Gobbler (pH 4.1) and Lawbreaker Lake (pH

type A-E glass fiber filter. The filter was blotted dry,

placed on silica gel desiccant, and frozen for no longer

than two months. Chlorophyll a concentrations were

determined by the methods of Richards and Thompson (1952)

and Yentsch and Menzel (1963). Chlorophyll a values were

calculated using the equations of Parsons and Strickland

(1963). Values were not corrected for pheophytin.

Aquatic Macrophyte Sampling

Aquatic macrophyte abundance was measured on all study

lakes except Brock. Measurement were made following the

methods of Maceina and Shireman (1980). Briefly, this

process includes using a boat mounted fathometer to estimate

the percent of areal coverage, and percent of lake volume

occupied by aquatic vegetation. Ten randomly selected

sampling transects were established around the perimeter of

each lake. The width of the emergent plant zone at each

transect was measured with a calibrated range finder.

Macrophyte biomass was determined from plant samples

collected from within 0.25 m2 quadrats placed in the

submerged, floating-leaved, and emergent plant zones (30

stations per lake). Excess water was removed from the plant

samples, which were then weighed to the nearest 0.10

kilogram fresh weight.

Fish Stocking

Largemouth bass were not present in electrofishing

samples from Lake Gobbler (pH 4.1) and Lawbreaker Lake (pH

4.4), the two most acid study lakes. To determine if this

species could survive and reproduce in these lakes,

specimens > 250 mm TL were taken from nearby Crooked Lake

(pH 4.6) and stocked into Lawbreaker Lake (pH 4.4) and Lake

Gobbler (pH 4.1).

Data Analysis

Equations used to calculate estimates of fish

population, density, biomass, and back calculate lengths at

age are presented in the respective sections. Simple linear

correlation and partial linear correlation procedures were

used to quantify relationships between fish abundance

parameters and lake morphoedaphic parameters. Correlation

coefficients and partial correlation coefficients were

determined using Statistical Analysis System procedures (SAS

1988).

Results

Lake Morphometry and Water Chemistry

The 12 study lakes were small and shallow, ranging in

size from 4 to 73 hectares, and mean depth ranging from 1.9

to 5.0 meters (Table 2-1). Mean pH values in the study

lakes ranged from 4.1 to 5.7 (Table 2-2). Ten of these

lakes had mean pH values below 5.0, and seven had mean pH

values below 4.8. Moore Lake and Lake Suggs were the two

lakes with mean pH values of 5.0 or above. Mean total

alkalinity ranged from 0.0 to 2.3 mg/L as CaC03, and mean

total acidity ranged from 3.4 to 15.0 mg/L as CaC03 (Table

4.4), the two most acid study lakes. To determine if this

species could survive and reproduce in these lakes,

specimens > 250 mm TL were taken from nearby Crooked Lake

(pH 4.6) and stocked into Lawbreaker Lake (pH 4.4) and Lake

Gobbler (pH 4.1).

Data Analysis

Equations used to calculate estimates of fish

population, density, biomass, and back calculate lengths at

age are presented in the respective sections. Simple linear

correlation and partial linear correlation procedures were

used to quantify relationships between fish abundance

parameters and lake morphoedaphic parameters. Correlation

coefficients and partial correlation coefficients were

determined using Statistical Analysis System procedures (SAS

1988).

Results

Lake Morphometry and Water Chemistry

The 12 study lakes were small and shallow, ranging in

size from 4 to 73 hectares, and mean depth ranging from 1.9

to 5.0 meters (Table 2-1). Mean pH values in the study

lakes ranged from 4.1 to 5.7 (Table 2-2). Ten of these

lakes had mean pH values below 5.0, and seven had mean pH

values below 4.8. Moore Lake and Lake Suggs were the two

lakes with mean pH values of 5.0 or above. Mean total

alkalinity ranged from 0.0 to 2.3 mg/L as CaC03, and mean

total acidity ranged from 3.4 to 15.0 mg/L as CaC03 (Table

4.4), the two most acid study lakes. To determine if this

species could survive and reproduce in these lakes,

specimens > 250 mm TL were taken from nearby Crooked Lake

(pH 4.6) and stocked into Lawbreaker Lake (pH 4.4) and Lake

Gobbler (pH 4.1).

Data Analysis

Equations used to calculate estimates of fish

population, density, biomass, and back calculate lengths at

age are presented in the respective sections. Simple linear

correlation and partial linear correlation procedures were

used to quantify relationships between fish abundance

parameters and lake morphoedaphic parameters. Correlation

coefficients and partial correlation coefficients were

determined using Statistical Analysis System procedures (SAS

1988).

Results

Lake Morphometry and Water Chemistry

The 12 study lakes were small and shallow, ranging in

size from 4 to 73 hectares, and mean depth ranging from 1.9

to 5.0 meters (Table 2-1). Mean pH values in the study

lakes ranged from 4.1 to 5.7 (Table 2-2). Ten of these

lakes had mean pH values below 5.0, and seven had mean pH

values below 4.8. Moore Lake and Lake Suggs were the two

lakes with mean pH values of 5.0 or above. Mean total

alkalinity ranged from 0.0 to 2.3 mg/L as CaC03, and mean

total acidity ranged from 3.4 to 15.0 mg/L as CaC03 (Table

*-4

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2-2). Seven of the study lakes had mean color values below

5.0 Pt-Co units. Lake Suggs and Gobbler Lake were highly (>

250 Pt-Co) colored units (Table 2-2). Mean specific

conductance of the study lakes ranged from 16 to 69 pS/cm at

25C. Mean calcium and magnesium concentrations ranged from

0.3 to 1.4 and 0.2 to 1.4 mg/L, respectively (Table 2-2).

Mean potassium concentrations ranged from 0.1 to 2.4 mg/L,

but most were below 0.4 mg/L (Table 2-2). Mean sodium and

chloride concentrations ranged from 1.2 to 5.2, and 2.5 to

14 mg/L, respectively. Mean sulfate concentrations ranged

from 2.0 to 11 mg/L. Mean aluminum concentrations ranged

from 32 to 260 mg/m3, with 10 lakes having averages below

100 mg/m3 (Table 2-2). Mean total nitrogen concentrations

ranged from 100 to 840 mg/m3 and mean total phosphorus

concentrations ranged from 2 to 99 mg/m3. Mean water

transparency ranged from 0.6 to 5.5 m, and mean chlorophyll

a concentrations ranged from 0.7 to 11 mg/m3 (Table 2-2).

Macrophytes

The areal coverage of aquatic macrophytes in the study

lakes ranged from 1% in Lawbreaker Lake to 97% in Deep Lake

(Table 2-3). The portion of lake volume occupied with

aquatic macrophytes ranged from <1% in Lake Gobbler to 22%

in Lofton Ponds, and the width of the littoral zone in the

study lakes ranged from 8 m in Turkey Pen Pond, Deep Lake

and Lake Gobbler to 32 m in Moore Lake (Table 2-3). Standing

crop (fresh weight) of emergent, floating, and submerged

o 4 N
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3.8, and <0.1 to 12 kg/m2, respectively (Table 2-3).

Fish Abundance--Electrofishing

During electrofishing sampling on the 12 study lakes,

6,923 fish, representing fifteen species from seven

families, were caught, marked and released (Table 2-4). The

families represented in the mark-recapture estimates were

Centrarchidae, Catostomidae, Ictaluridae, Esocidae, Amiidae,

Lepisosteidae, and Cyprinidae. The number of fish marked

and released per lake ranged from 36 fish in Gobbler Lake to

1175 fish in Crooked Lake (Table 2-4). The relative

abundance of each marked species varied among the study

lakes (Figures 2-2 to 2-13).

In descending order, warmouth (Lepomis gulosus),

bluegill, and largemouth bass were the most widely

distributed species in the 12 study lakes. Of the 15

species collected during mark-recapture sampling, only one

species, warmouth, was collected from all study lakes (Table

2-4). The relative abundance of warmouth ranged from 0.9%

in Lake McCloud to 20% in Lawbreaker Lake (Figures 2-7 and

2-3, respectively). Generally, warmouth represented less

than 7% of the fish greater than 150 mm TL collected by

electrofishing. Brock Lake was the only lake where

sufficient numbers of warmouth were marked to obtain a

population estimate. The estimated density and biomass of

warmouth in Brock Lake was 5 fish/hectare and 1.2

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kg/hectare, respectively (Table 2-5). The observed relative

abundance of warmouth was significantly (P < 0.10) related

to mean lake aluminum concentrations (r = 0.87). Warmouth

abundance was not significantly related to mean lake pH (r =

-0.09), mean lake total alkalinity (r = -0.08), or any of

the other morphoedaphic parameters measured.

Bluegill were collected from 11 of the 12 study lakes

(Table 2-5). The relative abundance of bluegill ranged from

4.6% in Turkey Pen Pond to 78% in Lake Barco (Figures 2-8

and 2-4, respectively). Bluegill was the most abundant

species in Lake Barco (78%), Lake McCloud (47%), and Lake

Gobbler (42%), and the second or third most abundant species

in Crooked Lake, Deep Lake, Turkey Pen Pond, Lake Tomahawk,

Brock Lake, Lake Suggs, and Moore Lake (Figures 2-2 to 2-

13). Density estimates of bluegill ranged from 2 fish/ha in

Turkey Pen Pond to 154 fish/ha in Lake Barco and biomass

estimates of bluegill ranged from 0.2 kg/ha in Turkey Pen

Pond to 16 kg/ha in Brock Lake (Table 2-5). The observed

abundance of bluegill was significantly (P < 0.10) related

to mean lake aluminum concentrations (r = 0.60), but was not

significantly (P > 0.10) related to mean lake pH (r = -

0.35), mean lake total alkalinity (r = -0.26), or any of the

other morphoedaphic parameters measured. Estimated

densities and biomasses of bluegill from the study lakes

were not significantly (P > 0.10) related to mean lake pH (r

= -0.38 and r = 0.17, respectively), mean lake total

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alkalinity (r = -0.32 and r = 0.11, respectively), or any of

the other morphoedaphic parameters measured.

Largemouth bass was collected from 10 of the study

lakes (Table 2-4). Their relative abundance ranged from 4%

in Lake Suggs to 52% in Lake McCloud (Figures 2-12 and 2-7,

respectively). Largemouth bass was the most abundant

species in Lake McCloud (52%), Moore Lake (43%), and Brock

Lake (31%), and the second most abundant species in Lake

Barco, Crooked Lake, Deep Lake, Turkey Pen Pond, Lofton

Ponds, and Lake Tomahawk (Figures 2-2 to 2-13). The 1988

estimated densities of adult largemouth bass ( > 250 mm TL)

ranged from 2 fish/ha in Lake Suggs to 45 fish/ha in Crooked

Lake and biomasses ranged from 1.8 kg/ha in Lake Barco to 25

kg/ha Lake Tomahawk (Table 2-6). The estimated densities

and biomasses of subadult (150 to 249 mm TL) largemouth bass

during the same period ranged from 0.5 fish/hectare in Lake

Suggs to 133 fish/ha in Lake Tomahawk, and from 0.05 kg/ha

in Lake Suggs to 14 kg/ha in Lake Tomahawk, respectively

(Table 2-6). There was a significant (P < 0.10) inverse

relationship between the observed relative abundance of

largemouth bass and mean lake aluminum levels (r = -0.58),

but the relationship between the observed relative abundance

of largemouth bass and mean lake pH (r = 0.24), mean lake

total alkalinity (r = 0.02), or any of the other

morphoedaphic parameters measured were not significant (P >

0.10). There was also no significant (P > 0.10)

relationship between the estimated density and biomass of

dt

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adult largemouth bass and mean lake pH (density: r = 0.12

and biomass: r = 0.33) and lake total alkalinity (density: r

= -0.07 and biomass: r = 0.15 ).

Three of the nine lakes for which there were density

estimates for both adult and subadult largemouth bass had

significant (P < 0.05) differences between the two groups.

Comparisons of 95% confidence intervals indicated that Lake

Barco and Tomahawk Lake had higher densities of subadults

than adults, and Moore Lake had higher densities of adults

than subadults (Figure 2-14).

Lake chubsucker (Erimyzon sucetta), also a widely

distributed species, was collected from nine of the 12 study

lakes (Table 2-4). The relative abundance of lake

chubsucker ranged from 9% in Lake Suggs to 80% in Lawbreaker

Lake (Figures 2-12 and 2-3, respectively). This species was

the most abundant in electrofishing samples from Lawbreaker

Lake (80%), Turkey Pen Pond (76%), Crooked Lake (51%), Lake

Tomahawk (48%), Lofton Ponds (41%), and Deep Lake (37%).

Lake chubsucker was also the second or third most abundant

species in Brock Lake, Lake Gobbler, and Lake Suggs (Figures

2-2 to 2-13). The relative abundance of lake chubsucker was

not significantly (P > 0.10) related to mean lake pH (r = -

0.25) or total alkalinity (r = -0.57). There was, however,

a significant (P < 0.10) inverse relationship between lake

chubsucker relative abundance and lake mean depth (r = -

0.78). Estimated densities and biomasses of lake chubsucker

ranged from 3 fish/hectare in Lake Suggs to 277 fish/ha in

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Brock Lake, respectively (Table 2-5), and were not

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= -0.56 and biomass: r = -0.25). Lake chubsucker biomass

was significantly (P < 0.10) related to the biomass (i.e.,

fresh weight) of emergent aquatic macrophytes (r = 0.74).

Three species of ictalurid catfishes were collected

with electrofishing gear. They were yellow bullhead

(Ictalurus natalis), brown bullhead, and tadpole madtom

(Noturus qyrinus) (Table 2-4). The relative abundance of

yellow bullhead, the most common of the three species,

ranged from 0.7% in Lake Tomahawk to 7% in Brock Lake

(Figures 2-10 and 2-11, respectively). Density and Biomass

estimates of yellow bullhead, available for only two study

lakes were 2 fish/ha and 0.4 kg/ha in Lake Suggs and 25

fish/ha and 9 kg/ha in Brock Lake (Table 2-5). Brown

bullhead and tadpole madtom were rare, occurring in one and

three lakes, respectively (Table 2-4).

Two species of Esocidae, redfin pickerel and chain

pickerel (Esox niger), were collected from six and four

study lakes, respectively (Table 2-4). The relative

abundance of redfin pickerel ranged from 1.7% in Lake Suggs

to 9% in Lofton Ponds (Figures 2-12 and 2-9, respectively).

None of the marked redfin pickerel were recaptured;

therefore, density and biomass estimates could not be

calculated for this species. The relative abundance of

chain pickerel ranged from 2% in Brock Lake to 29% in Moore

Lake (Figures 2-11 and 2-13, respectively). Chain pickerel

density and biomass estimates ranged from 0.9 fish/ha in

Lake Suggs to 42 fish/ha in Lofton Ponds, and 0.3 kg/ha in

Lake Suggs to 8.6 kg/ha in Moore Lake, respectively (Table

2-5).

Two other important species, bowfin (Amia calva, from

the family Amiidae), and Florida spotted gar (Lepisosteus

platyrhincus, from the family Lepisosteidae), were collected

from three study lakes (Table 2-4). The relative abundance

of bowfin ranged from 0.2% in Deep Lake to 11% in Gobbler

Lake (Figures 2-6 and 2-2, respectively). Bowfin density

and biomass estimates, available only for Lake Suggs, were 3

fish/ha and 3.2 kg/ha, respectively (Table 2-5). The

relative abundance of Florida spotted gar ranged from 7% in

Deep Lake to 10% in Lake Suggs (Figures 2-6 and 2-12,

respectively). The estimated densities of Florida spotted

gar were 14 fish/ha and 5 fish/ha in Deep Lake and Lake

Suggs, respectively. Estimated biomasses were 3.9 kg/ha and

1.2 kg/ha, respectively. Density and biomass estimates were

not calculated for Florida spotted gar in Lake Gobbler due

to insufficient sample size (Table 2-5).

Golden shiner (Notemigonus crysoleucas), the only

cyprinid present in electrofishing samples, was very rare.

The species was only collected from Crooked Lake and Lake

Suggs, and comprised less than 1% of the fish collected from

both lakes (Figures 2-5 and 2-12, respectively). Density

and biomass estimates for golden shiner were not calculated

because none of the marked fish were recaptured.

Fish Abundance and Biomass--Gillnetting

The mean number and weight of fish (i.e., of all

species) caught per gillnet set in the study lakes ranged

from 1 to 16 fish per net set, and 0.1 to 8.8 kg per net

set, respectively (Table 2-7). The mean number and weight

of fish caught per gillnet set were not significantly (P >

0.10) related to mean lake pH (r = 0.03 and r = 0.21) or

total alkalinity (r = -0.04, and r = 0.25) (Figures 2-15 and

2-16, respectively). The mean number (r = 0.51) and weight

(r = 0.89) of fish caught per gillnet set were significantly

(P < 0.10) related to chlorophyll a concentrations (Figure

2-17).

Total Fish Abundance and Biomass--Block-netting

Nine of the 12 study lakes were sampled with rotenone

and block-nets. The estimates of total fish (i.e., all

species) in these nine lakes ranged from 53 fish/ha in

Lawbreaker Lake to 13,000 fish/ha in Lake Tomahawk.

Estimates of total fish biomass ranged from 3.4 kg/ha in

Lawbreaker Lake to 95 kg/ha in Crooked Lake (Table 2-8).

Estimates of total fish density and total biomass were not

significantly (P > 0.10) related to mean lake pH (r = 0.55

and r = 0.30) or mean total alkalinity (r = 0.45 and r = -

0.07) (Figures 2-18 and 2-19, respectively).

and biomass estimates for golden shiner were not calculated

because none of the marked fish were recaptured.

Fish Abundance and Biomass--Gillnetting

The mean number and weight of fish (i.e., of all

species) caught per gillnet set in the study lakes ranged

from 1 to 16 fish per net set, and 0.1 to 8.8 kg per net

set, respectively (Table 2-7). The mean number and weight

of fish caught per gillnet set were not significantly (P >

0.10) related to mean lake pH (r = 0.03 and r = 0.21) or

total alkalinity (r = -0.04, and r = 0.25) (Figures 2-15 and

2-16, respectively). The mean number (r = 0.51) and weight

(r = 0.89) of fish caught per gillnet set were significantly

(P < 0.10) related to chlorophyll a concentrations (Figure

2-17).

Total Fish Abundance and Biomass--Block-netting

Nine of the 12 study lakes were sampled with rotenone

and block-nets. The estimates of total fish (i.e., all

species) in these nine lakes ranged from 53 fish/ha in

Lawbreaker Lake to 13,000 fish/ha in Lake Tomahawk.

Estimates of total fish biomass ranged from 3.4 kg/ha in

Lawbreaker Lake to 95 kg/ha in Crooked Lake (Table 2-8).

Estimates of total fish density and total biomass were not

significantly (P > 0.10) related to mean lake pH (r = 0.55

and r = 0.30) or mean total alkalinity (r = 0.45 and r = -

0.07) (Figures 2-18 and 2-19, respectively).

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Lake pH

Figure 2-15. Relationship between mean density and biomass
of fish collected per experimental gillnet from the study
lakes and lake pH.

20

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1 03 07 11 15 19 23 27

Total Alkalinity (mg/L.as CaCO3)

Figure 2-16. Relationship between mean density and biomass
of fish collected per experimental gillnet from the study
lakes and lake total alkalinity.

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- m

m mm

mmm
-- m, rI
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Chlorophyll a (mg/mr)

Figure 2-17. Relationship between mean density and biomass
of fish collected per experimental gillnet from the study
lakes and lake chlorophyll a concentrations.
9 --------,--------------------

Y"5> 6-

^1 --

0 2 4 6 8 10 12

Chlorophyll a (mg/m1)

Figure 2-17. Relationship between mean density and biomass
of fish collected per experimental gillnet from the study
lakes and lake chlorophyll a concentrations.

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Lake pH

Figure 2-18. Relationship between total density and biomass
estimates of fish collected per hectare from the study lakes
with rotenone and block-nets and lake pH.

20

18-

16-

14-

12-

100
90 m
8

6-

4-

2

0
4.2 4.4 4.6 4.8 5 5.2 54 56 5.8 6

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70

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03 07 11 1.5 1.9 23 2.7

03 07 11 15 19 23 27

Total Alkalinity (mg/L as CaCO,)

Figure 2-19. Relationship between total density and biomass
estimates of fish collected per hectare from the study lakes
with rotenone and block-nets and lake total alkalinity.

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70
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40
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20-
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01
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Condition Factors

The average condition factors (KTL) for subadult and

adult fish collected from the study lakes are presented in

Tables 2-9 and 2-10, respectively. Adult Florida spotted

gar, longnose gar (Lepisosteus osseus), and bowfin had

equivalent mean condition factors across the lakes where

they were collected, but the available data were

insufficient to determine if the coefficients of condition

for either species were related to pH or total alkalinity

(Table 2-10).

Condition factors for adult chain pickerel (> 300 mm

TL) and redfin pickerel (> 100 mm TL) ranged from 0.52 to

0.55 and from 0.46 to 0.58, respectively (Table 2-10). The

available data were insufficient to determine if the

coefficients of condition were related to either pH or total

alkalinity for chain pickerel, but condition factors for

redfin pickerel were not significantly (p > 0.05) related to

either pH (r = 0.60) or total alkalinity (r = 0.64).

Subadult chain pickerel (< 300 mm TL) condition factors

ranged from 0.49 in Lofton Ponds to 0.53 in Brock Lake

(Table 2-9). Condition factors for subadult (< 150 mm TL)

and adult (> 150 mm TL) lake chubsucker ranged from 1.02 to

1.35 and from 1.00 to 1.36 (Tables 2-9 and 2-10),

respectively. Although condition factor values for this

species were significantly different among lakes. Neither

subadult or adult condition factors values were

significantly related to pH subadultt: r = 0.14 and adult: r

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= 0.33) or total alkalinity subadultt: r = 0.14 and adult: r

= 0.56).

Condition factors for adult yellow bullhead ranged from

1.32 in Brock Lake to 1.56 in Moore Lake (Table 2-10).

These values were significantly related to pH (r = 0.79),

but the statistical relationship was heavily influenced by

Moore Lake. When Moore Lake was omitted from the data set,

and the data reanalyzed, there was no significant

relationship between lake pH and yellow bullhead condition

factor. There also was no significant relationship between

yellow bullhead condition factor and total alkalinity (r =

0.56; p > 0.05). The average condition factor of brown

bullhead, collected only in Lake Suggs, was 1.36 (Table 10).

The average condition factor for adult black crappie

(Pomoxis niqromaculatus) was 1.23 in Crooked Lake and 1.28

in Lake Suggs, the only systems in which they were collected

(Table 2-10).

Condition factors for subadult (< 150 mm TL) and adult

(> 150 mm TL) warmouth, the only cosmopolitan species in

this study, ranged from 1.65 to 2.04 and from 1.70 to 2.18

(Tables 2-9 and 2-10), respectively. Condition factors

differed significantly among lakes, but the relationship

between mean condition factors and mean lake pH subadultt: r

= 0.36 and adult: r = 0.55) or total alkalinity subadultt: r

= 0.50 and adult: r = 0.57) was not significant.

Condition factors for subadult (<150 mm TL) bluegill

ranged from 1.29 in Turkey Pen Pond to 1.91 in Moore Lake

(Table 2-9). Subadult bluegill condition factors were

significantly (P < 0.05) related to mean lake pH (r = 0.81),

mean lake total alkalinity (r = 0.79), total nitrogen (r =

0.63), and the width of the littoral zone (r = 0.84). There

was also a significant (P < 0.10) inverse relationship

between subadult bluegill condition factors and lake mean

depth (r = -0.62). Total alkalinity and lake pH were highly

related to each other (r = 0.93; P < 0.01); therefore,

partial correlation analysis were performed when both of

these parameters were significantly related to fish

condition. Partial correlation analysis, accounting for

total alkalinity, showed that the relationship between mean

lake pH and the condition factors of subadult bluegill was

not significant (partial r = 0.36; P > 0.05).

Adult bluegill condition factors ranged from 1.30 in

Turkey Pen Pond to 1.99 in Moore Lake (Table 2-10). Adult

bluegill condition factors were significantly (P < 0.05)

related to mean lake pH (r = 0.72), mean lake total

alkalinity (r = 0.78), the width of the littoral zone (r =

0.74), and mean lake total nitrogen (r = 0.54). There was

also a significant (P < 0.10) inverse relationship between

adult bluegill condition factors and study lake mean depth

(r = -0.63). Partial correlation analysis, accounting for

total alkalinity, indicated that relationship between mean

lake pH and the condition factor of adult bluegill was not

significant (partial r = -0.02; P > 0.05).

Mean condition factors for subadult largemouth bass

(150 249 mm TL) sampled during this study ranged from 0.98

in Lake Barco to 1.27 in Moore Lake (Table 2-9). Subadult

largemouth bass condition factors were significantly (P <

0.10) related to mean lake pH (r = 0.66) and total

alkalinity (r = 0.61), but the exclusion of Moore Lake, a

statistical outlier, from the data set resulted in

nonsignificant relationships. Mean condition factors for

subadult largemouth bass were also significantly related to

lake littoral zone width (r = 0.65). Mean condition factors

of adult largemouth bass (. 250 mm TL) ranged from 1.00 in

Lake Barco to 1.36 in Lofton Ponds and Lake Suggs (Table 2-

10) and were significantly (P < 0.10) related to mean lake

pH (r = 0.59), total alkalinity (r = 0.70), lake littoral

zone width (r = 0.57; Figure 2-20), and total nitrogen (r =

0.79; Figure 2-21). Partial correlation analysis,

accounting for total alkalinity, indicated that the

relationship between lake pH and the average condition

factor of adult largemouth bass was not significant (partial

r = -0.22; P > 0.05).

Age and Growth of Largemouth Bass

The age of largemouth bass collected from the study

lakes ranged from Age 0 (i.e, young of the year) to at least

Age IV. The whole otolith method of determining the age

largemouth bass is not reliable for aging fish older than

Age IV (Hoyer et al. 1985); therefore, otoliths were read

74

1.6

1.4
0

1.2

1- *

0.8
5 10 15 20 25 30 35

Width (m) of littoral zone

Figure 2-20. Relationship between mean condition factors
(KTL) for adult largemouth bass collected from the study
lakes with electrofishing gear and the width of lake
littoral zone.

MILLISECOND	CLASS.METHOD	MESSAGE
0	sobekcm_page_globals.constructor
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0	sobekcm_database.verify_item_lookup_object
0	sobekcm_page_globals.constructor	Navigation Object created from URI query string
0	sobekcm_database.verify_item_lookup_object
0	sobekcm_page_globals.display_item	Retrieving item or group information
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0	sobekcm_assistant.get_entire_collection_hierarchy
0	cached_data_manager.retrieve_item_aggregation
0	cached_data_manager.retrieve_item_aggregation	Found item aggregation on local cache
0	item_aggregation_builder.get_item_aggregation	Found 'all' item aggregation in cache
0	system.web.ui.page.page_load (ufdc.page_load)
0	sobekcm_page_globals.constructor.on_page_load
0	html_echo_mainwriter.add_style_references	Adding style references to HTML
0	html_echo_mainwriter.add_text_to_page	Reading the text from the file and echoing back to the output stream
63	html_echo_mainwriter.add_text_to_page	Finished reading and writing the file