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SPATIAL AND TEMPORAL DISTRIBUTION AND ABUNDANCE
OF LARVAL FISHES IN PENTWATER MARSH,
A COASTAL WETLAND ON LAKE MICHIGAN

By

Sara Lee Chubb

A THESIS

Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

MASTERS OF SCIENCE

Department of Fisheries and Wildlife

1985

 

2.)
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”)

ABSTRACT

SPATIAL AND TEMPORAL DISTRIBUTION AND ABUNDANCE
OF LARVAL FISHES IN PENTWATER MARSH,
A COASTAL WETLAND ON LAKE MICHIGAN
By

Sara Lee Chubb

Pentwater Marsh, located 25 km south of Ludington,
hfichigan, was studied as a spawning and nursery habitat for
fishes. Objectives included: 1) development of sampling
techniques appropriate to the marsh habitat; 2) quanti-
fication of larval fish abundance and distribution; and,

3) identification of habitat parameters related to larval
fish occurrence and distribution. A total of 562 samples
were collected by day and night, bi-weekly, March through
August, 1982. Marsh channels and bayou—mouths were sampled
with conventional push-nets. A drop-net technique was
developed for sampling in the shallow-water bayous.

A total of 3,926 larval fish were collected and 18
Species were identified. Carp comprised over 75% of the
catch. Other major species included gizzard shad, cyprinids,
YEIIOw perch and pumpkinseed sunfish. Larval fish densities
in the shallow-water bayous were approximately ten—times
Breater than densities in marsh channels and fifty-times
Breater than densities in nearby Lake Michigan. Larval fish
distribution and abundance were related to vegetation4types,

dissolved oxygen levels, water temperature, and water depth.

ACKNOWLEDGMENTS

I wish to thank all who assisted me through this
program. Funding was provided by Michigan Sea Grant and the
Michigan State Agricultural Experimental Station. Research
facilities and equipment were provided by Michigan State
University, Department of Fisheries and Wildlife. Dr.
Charles Liston, my major professor, was most gracious in
allowing me to participate in all phases of research and
development. Under his guidance, and with the encouragement
of Michigan Sea Grant, I learned much more than a text-book
approach to research. I wish to also thank Drs. William
Taylor and Patrick Muzzall for their patience and genuine
interest in my endeavors.

Special thanks must go to the dedicated personnel of
the Michigan State University Fisheries Laboratory of
Ludington, Michigan. In particular, Dan Brazo was
instrumental in my initiation into the field of larval fish
ecology. Dan Brazo, Guy Fleisher, Rick Ligman, Greg
Peterson, Pat Carlson, Barb Pompema, and Leo Yeck were
invaluable sources of expertise throughout my study. Both
Dan Brazo and Diane Ashton provided assistance with larval
fish identification. Thanks to Diane for the use of her
push-net as developed for the St. Mary's River project. Joe
Bohr taught me not to fear computers or statistics; I
appreciate his consultations. Thanks to Dr. Burton and Jim

Kelley for the additonal information on wetland ecology and

ii

their cooperative effort with the Michigan State University
Remote Sensing Laboratory in obtaining the aerial
photography.

This project could not have succeeded without the
enthusiasm and diligence of the undergraduate interns;
Robert Day, Mary Fasano, and Janet Jokerst. Thanks to Kelly
Duis, Don Hanson, and Larry Gigliotti for their volunteer
efforts. I am indebted to the diligence of my many work
study students, particularly for their fine job at larval
fish picking. I am most grateful for the professional and
personal support of my field technicians, Amy Peterson and
Karen Braun.

I particularly cherish those who supported me
emotionally through this stressful period of my life.
Thanks to my parents, Michael and Holly Chubb, for their
unfailing confidence in my abilities-— even when I may have
had my doubts. Copy services were facilitated through
Michael Chubb. Special thanks to Holly for her expert
proof-reading, manuscript guidance, and overall
encouragement. Thanks to Larry Gigliotti for his love and

support when I needed it most.

iii

TABLE OF CONTENTS

LIST OF TABLES O O O O O O O O O O O O Vii-i
LIST OF FIGURES . . . . . . . . . . . Xi

LIST OF ABBREVIATIONS AND SYMBOLS. . . . . . xiv

INTRODUCTION . . . . . . . . . . . . 1

DESCRIPTION OF THE STUDY SITE . . . . . . '. 6

METHODS AND MATERIALS . . . . . . . . . 12

Adult fish collections . . . . . . . 12

Larval fish-- field sampling . . . . . 14

Larval fish--laboratory . . . . . . . 19
Physical, chemical, and vegetative

measurements . . . . . . . . . . 20

Data analysis--statistical procedures . . 22

RESULTS . . . . . . . . . . . . . . 26

Physical, chemical and habitat parameters . 26

Rainfall, water levels, water depths . 26

Water temperature . . . . . . . 28

Dissolved Oxygen . . . . . . . 32

Turbidity and pH . . . . . . . 34

Vegetative cover . . . . . . . 38

Fishes . . . . . . . . . . . . . 39

Gear and laboratory efficiency tests . 39

iv

TABLE OF CONTENTS (cont'd)

Fish spawning activity . . . . . .
Larval fish abundance and distribution.
Carp . . . . . . . . .' . . .
Gizzard shad . . . . . . . . .
Cyprinids . . . . . . . . . .
Pumpkinseed sunfish . . . . . . .
Yellow perch . . . . . . . . .
Northern pike . . . . . . . . .
Black crappie . . . . . . . . .
Johnny darter . . . . . . . . .
Alewife . . . . . . . . . . .
Brook silverside . . . . . . . .
Other species . . . . . . . . .
Community patterns . . . . . . .
Standing crop estimates . . . . .
Larval fish drift. . . . . . . .

Larval fish abundance in adjoining
habitats O I O O O O O O O 0

Environmental parameters and larval fish
abundance . . . . . . . . .

DISCUSSION . . . . . . . . . . . . .
Gear evaluation . . . . . . . . . .
Total larval fish abundance . . . . . .
Monthly occurrence and diversity . . . .

Diel patterns of diversity, abundance,
and distribution . . . . . . . . .

41
45
55
69
75
81
85
88
9O
91
92
93
94
95
101
101

103

106

109

109

114
116

119

 

TABLE OF CONTENTS (cont'd)

Regional patterns of diversity and

distribution . . . . . . . . . . 124
Larval fish distribution and vegetative

patterns. . . . . . . . . . . . 126
Community interactions . . . . . . . 131
Environmental factors . . . . . . . 135
Pentwater Marsh as a nursery area for fishes 144

Conclusions . . . . . . . . . . . 155

SUMMARY . . . . . . . . . . . . . . 159
LITERATURE CITED . . . . . . . . . . . 168
APPENDICES o o o o o o o o o o o o o 186

APPENDIX A. Environmental parameters (mean+ SE)
as measured across major regions, bayousT
vegetation types, and channel stations of the
Pentwater Marsh during the 1982 sample season. 186

APPENDIX B. Mean larval fish densities (mean #/m3
i SE) as measured across major regions, bayous,
vegetation types, and channel stations of the
Pentwater Marsh during the 1982 sample season. . 192

APPENDIX C. Mann-Whitney-U and Xruskal-Wallis
test statistics as calculated for differences
in larval fish densities across regions and
stations of the Pentwater Marsh. . . . . . 203

APPENDIX D. Larval fish coefficients of
variation as calculated for major regions

and vegetation types of the Pentwater Marsh
during 1982. o o o o o o o o o o o 208

APPENDIX E. Larval fish total lengths (mean:
SE in mm) across major regions, bayous, vegetation
types, and channel stations of the Pentwater Marsh
during the 1982 sample season. . . . . . 214

vi

 

TABLE OF CONTENTS (cont'd)

APPENDIX F. Student-t values and significance
levels (one-tailed) of larval fish total lengths
(mm) across major regions, bayous, vegetation
types, and channel stations of the Pentwater
Marsh during the 1982 sample season. . . . 216

APPENDIX G. Larval fish diversity indices
(H', D, and J) as calculated for various regions
and stations of the Pentwater Marsh during
the 1982 sample season. . . . . . . . 225

APPENDIX H. Mean sample Shannon-Weaver diversity
indices (H') across stations and regions of
the Pentwater Marsh during the 1982 sample
season. . . . . . . . . . . 228

APPENDIX I. Standing crop estimates (#lHA)
for larval carp,cyprinids, Lgpnmis spp., northern
pike, and yellow perch as calculated for major
vegetation types of the Pentwater Marsh during
the 1982 sample season. . . . . . . . . 229

APPENDIX J. Estimated larval fish drift
(thousands/hour) between Pentwater Lake and
Pentwater Marsh during 1982. . . . . . . 230

APPENDIX K. Spearman-rank correlation coefficients
and associated significance levels among
parameters and larval fish densities in the
Pentwater Marsh during the 1982 sample season. . 231

vii

TABLE

10

LIST OF TABLES
PAGE

Channel and bayou vegetative‘area (mean mi: SE;
n-3) emergent edge, and shoreline development

as calculated from aerial photography taken

on July 11, 1982 . . . . . . . . . 9

Larval fish sampling schedule including

numerical effort of pull-nets and drop-nets

in the shallow-water bayous, push-nets in bayou-
mouths, and push-nets in the river channels

of the Pentwater Marsh. . . . . . . . . 13

Spearman-rank correlation of depth (m) with
other physical/chemical parameters as measured
at drop-net stations during 1982 (n-120). . . 29

Spearman-rank correlation of temperature (0C)

with other physical/chemical parameters as

measured at drop—net stations during 1982

(II-120). o o o o o o o o o o o o o 29

Spearman-rank correlation of dissolved oxygen
(mg/1) with other physical/chemical parameters

as measured at drop-net stations during 1982
(n-120). . . . . . . . . . . . . . 35

Summary of drop-net efficiency testing conducted
on eggs, larvae, and juvenile fishes of the
Pentwater Marsh during June and August of 1982. 40

Summary of egg and larval fish picking efficiency
based on 52 repicks of 1982 ichthyoplankton
sampleSQ O O I O O O O O O O O O O 42

Numerical catch and effort of trap—net and
gill-net sets in the Pentwater Marsh from
April through July, 1982. . . . . . . . 43

Numbers and species of post-juvenile fishes
captured in drop-net sampling in the bayous of
Pentwater Marsh during 1982. . . . . . . .46

The numerical catch, species composition

(2 frequency of catch),and list of common and
scientific names of larval fish species

encountered in the Pentwater Marsh during

the 1982 sample season. . . . . . . . .48

viii

11

12

13

14

15

16

17

18

LIST OF TABLES (cont'd)

Mean coefficients of variation (SD/mean)
and estimated sample size by day and night,
and across marsh regions and vegetation types. . 54

Mann-Whitney-U statistical differences in larval
fish densities of major marsh species between
shallow-water bayous (U), bayou-mouths (L), and
channel stations (0C) of Pentwater Marsh during
1982. All stations not unscored by the same

line were found to be significantly different
(p<O.10). . . . . . . . . . . . . ..57

Statistical differences in nighttime larval fish
densities between north branch (N), south branch
(S), and main channel (M) stations of Pentwater
Marsh as determined by the Mann-Whitney-U test.

All stations not underscored by the same line

were found to be significantly different

(p<O.10). . . . . . . . . . . . . . 59

Statistical differences in nighttime larval fish
densities between emergent (E), floating-leaf (N),
and submergent (S) vegetation of Pentwater Marsh

as determined by the Mann-Whitney-U test. All
stations not underlined by the same line were

found to be significantly different (p<O.10;
one-tailed). . . . . . . . . . . . .62

Day and night coefficients of variation
(CV-SD/mean) for various marsh species at

peak larval abundance, and as averaged across

the 1982 sample dates (n). . . . . . . . .63

Coefficients of variation (SD./mean) for

various larval fish species and vegetation

types, as averaged across the 1982 sample

season. . . . . . . . . . . . . . 64

Nighttime associations among larval fish species
of the Pentwater Marsh, as measured by Forbe's
coefficient (cf). Cf values of 0 indicate

chance association, whereas values of 1 and -1
indicate complete association and disassociation
respectively. . . . . . . . . . . . f

Daytime association among larval fish species

of the Pentwater Marsh, as measured by Forbe's
coefficient (Cf). Cf values of 0 indicate

chance association, whereas values of 1 and -1
indicate complete association and disassociation
respectively. . . . . . . . . . . . 100

ix

19

20

21

22

LIST OF TABLES (cont'd)

Standing crop (#/HA wetland) of major larval fish
species as encountered in the bayous of the
Pentwater Marsh during 1982. Standard errors,
although not included for each figure, represent
approximately 501 of the mean. . . . . . 102

Estimates of larval fish drift (#lday) at the
Pentwater Marsh outlet on select sample dates

of 1982. Positive values represent net daily
numerical drift from marsh to Pentwater Lake,
whereas negative values indicate a net daily

flux of larvae into the marsh due to seiche
activity. . . . . . . .. . . . . . 105

Comparisog of peak nighttime larval fish densities
(mean #/m +SE) as measured in Pentwater Marsh,
Pentwater Lake, the lake outlet, and Lake

Michigan. . . . . . . . . . . . . 105

Spearman-rank correlations (r coefficient and
t-value) of larval fish densities and

environmental parameters, as measured at

the 1982 drop-net stations in the shallow-water
bayous of Pentwater Marsh. . . . . . . . 107

FIGURE

1

10

11

LIST OF FIGURES

PAGE
Map of the Pentwater Marsh showing
push-net (H ), drop-net (I), and trap-
net and gill-net(A.) sample sites. . . . . . 7

Diagram of the larval fish half-meter (363u mesh)
push-net as operated from the bow of a small

boat in the channels and bayou-mouths of

Pentwater Marsh. . . . . . . . . . . .15

Diagram of the drop-net sampler (363u mesh sides)
as used in conjunction with a meter dip-net
in the shallow-water bayous of Pentwater Marsh. .15

Meteorological and hydrological conditions of
the Pentwater Marsh during 1982. . . . . . 27

Temperature profiles for each of the major
vegetation types (n-3) as recorded in bayou
W on September 9, 1983. . . . . . . . . 31

Dissolved oxygen levels across sample stations
of bayou W, as recorded over 24 hours on
September 9, 1983. . . . . . . . . . . 33

Dissolved oxygen levels across marsh vegetation
types and water depth, as recorded over 24
hours on September 9, 1983. . . . . . . . 36

Relative abundance and seasonal occurrence of
larval fish species in the shallow-water
bayous of Pentwater Marsh. . . . . . . . 49

Total nighttime larval fish densities as

measured by push-nets in the channels and
bayou-mouths, and drop-nets in the shallow-

water bayous of the Pentwater Marsh. . . . . 50

Total nighttime larval fish densities as

measured by drop-net and push-net sampling

in the major bayous (X,Y,W, and Z) of the

Pentwater Marsh. . . . . . . . . . . .51

Total nighttime larval fish densities as
measured by push-net sampling in the north

xi

 

 

12

13

14

15

l6

17

18

19

20

21

LIST OF FIGURES (cont'd)

and south branch and main channel of the
Pentwater Marsh. . . . . . . . . . . .53

Day and night larval carp densities as measured
across the major regions (shallow-water bayous,
bayou-mouths, and side and mid channels) of

the Pentwater Marsh. . . . . . . . . . 56

Day and night larval carp densities as measured
across the major bayous (X, Y, W, and Z) and
channel stations (north, south, and main

channels) of the Pentwater Marsh. . . . . . 58

Day and night larval carp densities across
vegetation types of the shallow-water bayous
of the Pentwater Marsh. . . . . . . . . 61

Comparison of nighttime larval carp length-
frequencies between shallow-water bayou,
bayou—mouth, and channel stations of the

Pentwater Marsh. . . . . . . . . . . . 67

Comparison of nighttime larval carp length-
frequencies between the major bayous
(W,Y, and Z) of the Pentwater Marsh. . . . . 68

Comparison of nighttime larval carp length-
frequencies between the channel stations
of the Pentwater Marsh. . . . . . . . . 70

Comparison of nighttime larval carp length-
frequencies between vegetation types of the
shallow-water bayous of the Pentwater Marsh. . .71

Day and night larval gizzard shad densities

as measured across the major regions

(shallow-water bayous, bayou-mouths, and

side and mid channels) Of the Pentwater Marsh. .73

Day and night larval gizzard shad densities

as measured across the major bayous

(X,Y,W, and Z) and channel stations

(north, south, and main channels) of the

Pentwater Marsh. . . . . . . . . . . . 74

Day and night larval cyprinid densities

as measured across major regions (shallow-

water bayous, bayou-mouths, and side and

mid channels) of the Pentwater Marsh. . . . .77

xii

 

1.

Id

122

213

Zli

255

2(5

227

238

LIST OF FIGURES (cont'd)

Day and night larval cyprinid densities

as measured across the major bayous

(X, Y, W, and Z) and channel stations

(north, south, and main channels) of

the Pentwater Marsh. . . . . . . . . . 78

Comparison of nighttime larval cyprinid
length-frequencies between shallow-water

bayou, bayou-mouth, and channel stations

of the Pentwater Marsh. . . . . . . . . 80

Day and night larval Lepomis spp. densities

as measured across major regions (shallow-water
bayous, bayou-mouths, and side and mid channels)

of the Pentwater Marsh. . . . . . . . . 82

Day and night larval Lepomis spp. densities

as measured across the major bayous (X,Y,W,

and Z) and channel stations (north, south,

and main channels) of the Pentwater Marsh. . .84

Day and night larval yellow perch densities

as measured across the major regions (shallow-
water bayous, bayou-mouths, and side and

mid channels) of the Pentwater Marsh. . . . .86

Day and night larval yellow-perch densities

as measured across the major bayous (X,Y,W,

and Z) and channel stations (north, south,

and main channels) of the Pentwater Marsh. . . 87

Day and night larval fish species density

indices for shallow-water bayou, bayou-mouth,

and side and mid channel stations of the

Pentwater Marsh. . . . . . . . . . . .97

Day and night larval fish diversity indices

for major vegetation types in the shallow-
water bayous of the Pentwater Marsh. . . . . 98

xiii

U

‘1'

a

A

DWI

ln/s
Inm

NTU

pH

ESLD
‘3PP-

LIST OF ABBREVIATIONS AND SYMBOLS

celcius, degrees

Forbe's coefficient of association

coefficient of variation - SD/mean

centimeter

species evenness index

Shannon—Weaver index of diversity

hectare

hour

species richness index

kilometer

larval fish

meter

milliliters

square meter

cubic meter

meter per second

millimeter

sample size

nephelometric turbidity unit

probability or level of significance

log of the reciprocal of the concentration of
free hydrogen ions

correlation coefficient

shoreline length

shoreline development value

species

standard deviation

standard error

student's t values

total length

variance

multiplication, or reference to dimensions
plus or minus

foot

inches

percent

micrometer or micron

p<0.01
p<0.05
p<0.10
p>0.10

xiv

INTRODUCTION

Historically, the Great Lakes were once endowed with an
estimated 142,000 hectares of coastal wetlands. Human
settlement and associated activities have reduced these
habitats to approximately 301 of their original acreage
(Jaworski and Raphael 1978). Major areas of wetland loss
include the "Black Swamp" of Lake Erie (Xaatz 1955), Saginaw
Bay of Lake Huron (Berst and Splanger 1973), and Green Bay
of Lake Michigan (Harris et a1. 1978). Many of these
marshes and their adjoining coastal waters were once prime
fishing grounds for such species as walleye, whitefish,
Yellow perch, and northern pike (Hartman 1973). The
collapse of the Great Lake fishery around the turn of the
Century was partially attributed to the drainage of coastal
Wetlands for agricultural production (Trautman 1957; Hartman
1973; Wells and McLain 1973) .

Recently, the threat of agricultural expansion has been
replaced by that of urbanization and industrial development
(Regier and Hartman 1973). Present losses are estimated at
8 ,097 hectares of prime coastal wetland per year (Jaworski
and Raphael 1978). Moreover, continued environmental
degradation of the remaining wetlands has shifted the Great
Iaakes fishery to less desirable, but more tolerant species
Such as carp, redhorse, suckers, and gizzard shad (Trautman

1

1957; Hartman 1973). Within the next twenty years,
remaining coastal wetlands may undergo further and
increasing impacts related to power generation, commercial
navigation, and water diversion (Edsall 1976; Liston et al.
1981b; O'Gorman 1983).

The historical connection between wetlands and

fisheries production is quite evident. Wetlands have long

been popularly acknowledged as spawning, nursery, and
feeding habitats for a number of Great Lakes fish species.
Fish mortality is highest in the early life stages, and
8tlbsequent year class strength is often dependent on
environmental conditions during the first year of life (Marr
1956). Factors such as temperature (Walburg 1972),
tnI‘bidity (Auld and Schubel 1978), dissolved oxygen (Spoor
1977), water level (Franklin and Smith 1963), wind (Kramer
and Smith 1962), food availability (Hassler 1970),
competition (Weinstein 1979), and predation (Beck and Orth
198()) may be instrumental in determining year class success.
The numerical abundance and biomass for these early life
Stag es may represent as much as 40 to 801 of the total
production of a species (Mathews 1971; Craig 1980).
Moreover, processes of energetic transfer both within and
bet‘I'een communities are undoubtedly influenced by the
seaBanal pulse of larval and juvenile fishes.

Much has been gained from previous advances in marine

There are a number of similarities

In

est uarine research .

between marine estuaries and Great Lakes wetlands.

_

 

 

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:-

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fact, coastal wetlands of the Great Lakes have also been
termed "estuaries " in regard to the environmental gradient
from a large body of water to a riverine habitat (Brant and
Herdendorf 1972). Marine estuaries and their associated
marshes contribute significant numbers of recruits (75 to
90% of total) to a number of offshore commercial fisheries
(McHugh 1966; Carr and Adams 1973) and export immense
quantities of fish biomass of importance to local energy
flow (Day et al. 1973; Nixon and Oviatt 1973; Pendleton and
Copeland 1979). Odum (1971) stated that marine estuaries
exPort the energy which drives coastal zone productivity,
1311‘: this hypothesis has since been modified. As more
estuaries are studied, it becomes increasingly apparent that
93c}: system is unique and many questions remain unanswered.
Nevertheless, the insights and techniques gained from
estuarine investigations have prompted and encouraged
freshwater research efforts. In the past, freshwater
1chthyoplankton surveys have been confined to limnetic areas
(Faber 1963; Taber 1969; Werner 1967), perhaps due to the
extt‘eme difficulty of sampling in littoral inshore habitats
(Amandrud et al. 1974). Those researchers that have dealt
with littoral zones have been repeatedly impressed by the
great abundance and diversity of larval fishes utilizing
these areas (Backiel 1958; Faber 1967; Kindschi 1979;
L18":on et al. 1981b) and have commented on the protective

and supportive function of dense vegetative structure

(Werner et al. 1977; Mittelbach 1980). What little

SUS:

COES

4

information is available has dealt primarily with inland
marshes, particularly those vigorously managed for game
species such as northern pike (Hunt and Carbine 1951;
Franklin and Smith 1963; Kleinert 1970; Beyerle 1980) or
walleye (Priegel 1970). Only recently have researchers
begun to directly investigate the coastal wetland as a
spawning and nursery area for fishes (Jude et al. 1980;
Liston et al. 1981b; Cosentino 1983; Brazo 1985; Mansfield
1984). These researchers agree that coastal wetlands of the
Great Lakes are highly productive systems, capable of
Snataining high fish production. However, there is no
cOnsensus as to the significance of the coastal wetland to
the Great Lakes fish community.

This project was initiated in 1982 with funding from
"ileligan Sea Grant and the Michigan Agricultural Experiment
Station to evaluate the role of Pentwater Marsh as a nursery
habILtat for larval and juvenile fishes. Pentwater Marsh was
c11<>£3en since it was already the site of ongoing coordinated
sttltlies on hydrology, nutrient dynamics, vegetation, and
avian communities. Major objectives included the
development of appropriate methods for sampling in the
wetland habitat and the quantification of larval fish
distribution and abundance. Secondarily, patterns of
apeQies abundance and distribution were to be related to
marsh habitat parameters. Gear efficiencies will be
discussed only as relevant to the reliability of estimates.

A more detailed discussion of gear developments can be found

 

5

in technical reports to Sea Grant (Liston and Chubb 1983;

Chubb and Liston 1984).

"9

uni

\ 7W

DESCRIPTION OF THE STUDY SITE

Pentwater Marsh is located in Oceana County, on the
eastern shore of Lake Michigan approximately 25 km south of
Ludington, Michigan. The marsh may be classified as a
Palustrine persistent emergent wetland (Cowardin et a1.
1979), or as a drowned river-mouth estuary (Brant and
Herdendorf 1972). Although the marsh is situated 2.9 km
inland from Lake Michigan, it can be considered a coastal
wetland as it is contiguous with Pentwater Lake which is
laI‘gely influenced by Lake Michigan water levels (Figure 1).

The marsh is formed at the junction of the north and
south branches of the Pentwater River. Water entering the
marsh has traversed a 425 km2 watershed of approximately 60%
agricultural and 402 forested lands. A small low-head
reservoir is located 10 km up the south branch of the
PeIltwater River. Other water sources are thought to be

millzimal (personal communication, James Kelley) although
spr:lng seepage along the north branch may influence local
water temperatures and chemistry. An earthen dike and
county road restrict water outflow to a 30 m channel (48 m2
cross-sectional area at mid summer flow) at Long Bridge

Road. Marsh discharge ranged between 9.4 m3/s and 4.0 m3/s

6

.nmufim vanamm AD vuoalajflw ecu uoalmmuu can .Alv um:
Inouv .AIV umnlaman wcwzoam amumz “ouosucom on”. no an: .H 6.23.;

... Jun
.. .4. ...l .W
o 0-0 01 a.

 

thk’hzmm

5.2.5 .3 a

x

in April and August, respectively (personal communication,
James Kelley). Seiche activity follows a predictable cycle

wi th a slight reduction or reversal in current flow
Water

approximately every 20 minutes at the marsh outlet.

levels at the bridge may fluctuate by as much as 10 mm
bet: ween cycles (Seelig and Sorensen 1976). Lake Pentwater

18 an elongate lake of considerable fetch so that

not- thwesterly winds may further accentuate current reversal

in t o the marsh.
Pentwater Marsh provided an ideal study site not only

due to its restricted and identifiable inflow/outflow, but

31 a 0 because of its limited size. The marsh was bounded by

B“ & iness Route US 31 to the north, Long Bridge Road to the
we a t, upland shrubs to the south, and an arbitrary line

500 m upstream from the river branch junction. The

ef t ective area of the marsh was further defined as areas

gr § ater than 10 cm in water depth, and thus covered

ap Droximately 45 HA of the total 96 HA area (Table 1).

R1 v erine channels and associated riparian vegetation
c()ltnposed less than half of the effective marsh area. The
r

g “gaining 25 HA were shallow-water bayous containing an

it‘- t erspersion of open-water, emergents, floating-leaf, and
an Emergent vegetation in a ratio of 5:24:13:58. Giant

but-tweed (Sparmium eurycarpum) dominated the emergent zone

‘1 1:11 occasional stands of cattail (Typha latifolia) and

bnlrush (Scirpus spp.). Floating-leaf plants were primarily
V"a.t.er lilies (Nuphar spp. and Nymphaea spp.) with local

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mq.m mafl.m mmm.saq omm.ooH Nem.fim me~.o- -o.om "Hence
mm.~ nms.m mmmawmm.fio~ mafiaema.mo 1 Nomaoom.- HNmHmHo.o~ ”mamaaano
we.~ mmm.e OBLHAAH.SSN em amom.oH om «Nem.am om Hams.mefi omfiaqco.oc "maoamm
AL.H a H~o~.~ konaaee.mo awHHoSo.mm 1 Hfifiammm.a~ aw «Neo.m "amen new:
me.H N u~o~.H NmLHMOm.~e aw Hamo.- 1 Nagaaaa.sa mm «amc.o "auamam.m
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azmommzm a<m41.aa azmummzmam pzmommzm
ezmummzm A as <mx<
a: .i i 2%
. l 3:0 E3 asses N a i a :5
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10

concentrations of duckweed (Lemna minor). Spirogyra spp., a

 

 

filamentous blue-green algae, was often collected in
conjunction with vascular submergent plants particularly in

1a te summer. Common submergents included Myriophyllum

 

.§2 icatum , Ceratophyllum spp., Elodea canadensis,
Rarer vegetative

_QP tamogeton filiformis, and P. crispu .
8I-7’<_ecies included Utricularia spp. and Chara spp. All bayous

CO ntained soft organic substrates with unconsolidated layers
to depths of 5 to 20 cm. The dominant soil types were

fi brous Houghton muck and fine-particulate Kerston muck as

cotnmonly found in old lake bottoms and aluvial plains

(H erdendorf et a1. 1981).

Four major bayou regions were identified; bayous X, Y,

W and Z (Figure 1) represented 10%, 35%, 45%, and 10% of

th e shallow water habitat, respectively (Table 1). Bayous X

an G Y were characterized by much interspersion of vegetation

ty Des and extensive emergent shoreline development. Bayou W

wa- g dominated by submergent vegetation, while emergents

Db Qvailed in bayou Z. Bayous W and Z had very low

VQ getative interspersion and diversity. Of all the bayous,

ha you W had the greatest interaction with channel water and
“a $ thus most likely to be influenced by seiche activity of
th e lower marsh.

The marsh lies within the Pentwater State Game Area and

is host to a great variety of recreational activities. Fall

and spring offer opportunities for salmon and trout fishing.

Major exploited species include rainbow trout (Salmo

U‘

I???

a:
i

11

gairdneri), Brown trout (S. trutta), coho salmon
(Oncorhmchus kisutch), and Chinook salmon (Q. tshawytscha).

 

Winter ice fishing occurs mainly on Lake Pentwater where the

 

ma jor catch is black crappie (Pomoxis nigromaculatus) and

no rthern pike (Esox lucius). In summer, anglers enjoy high

 

su ccess in their pursuit of yellow perch (Perca flavescens),

no :rthern pike, and largemouth bass (Micropterus salmoides).

R0 mgh fish such as the white sucker (Catostomus commersoni),

 

Ca- :rp (Cyprinius carJio), and bowfin (Amia calva) support a
3‘1 ‘bstantial local fishery particularly in early spring.

No m—human fish consumers include great blue heron (Ardea

W), black tern (Childonias niger), belted kingfisher

(\Meraceryle alcyon), osprey (Panchion haliaetus), snapping

 

 

tn rtle (Chelydra serpentine), painted turtle (Chrysemys

M), and river otter (Lutra canadensis). The marsh is
al so host to a wide variety of nesting and staging waterfowl

 

1“ spring and fall, respectively. Fall waterfowl hunting

ha- :y adversely affect local fish populations by disrupting

“Q :rmal foraging patterns. Non-consumptive activities such

a Q bird watching and canoeing are likely of insufficient

“a snitude to impact the aquatic community.

METHODS AND MATERIALS

A number of authors have cited the difficulties

1rill-aerent in sampling fish populations of wetland habitats

(K Jelson and Colby 1977; Pendleton and Copeland 1979;

Kn shied 1981). Pilot studies in 1980 and 1981 dealt

pr :tmarily with field and laboratory testing of the various

8e are types (Liston and Chubb 1983). Full scale sampling

"a s initiated in the spring of 1982 and continues to date

"1 th increasing emphasis on juvenile fish of the marsh

(Q hubb and Liston 1984). For this analysis, larval fish

Ba~lxapling from March through August of 1982 will be

em bhasized (Table 2).

\Aq n11: Fish Collections

Fish spawning activity was qualitatively measured with

tb ep—net and gill-net collections from April through July of

1982. On April 1, April 13, and July 14, a 15.2 m (50')

Variable-meshed gill net (with seven 2.1x1.8m panels of
23(1"), 51(2"), 63(2.5"), 76 (3"), 102(4"). 114(4.5") and

178 (7") mm mesh) was deployed parallel to current flow in

the main channel of the Pentwater River.
12

Gill-net sets

 

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13

 

 

 

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.N van N macho: :H moan Na w.o van
me=H0> ma N.m was .N was 3 macho; :H ovum eN«.m can oaaHo> ma o.H mo Azmmv muoaInmsm m
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.moum Na «.m cam wasHo> ma No.0 mo wmwummm am no AHHamv muOGIHHam H
Nmm moH on omN mN me «HH «« omH «N «MN «m Nm «HH « HmuOB
aN NH m m I I I I I I mN NH w o I NmImNIm
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«« NH m NH 0 «« NH w mH o I I I I I Nwlwlo
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wN «N NH N« I «m NH « mH I «« NH m «N I «mImNIm
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mm «N I o I NH NH I I I HN NH I o I NmeNI«
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NH NH I I I I I I I I NH NH I I I NmIoNIm
o o I I I o o I I I I I I I I NmINIm
Hence teem see at: Haze Hence stem ems eta Haas Hence stem nee eta Haas deem

 

 

AMZZ<=D DDH<P
mOanmm Hmuoh mOHaamm u

IIlllhmcccmfiVlllkfitcmrll.

emfiz

 

 

 

 

cH muac1£a=a wee . u4flsca1=caai ¢4H aw msoa1¢m=s .m=OHaJ Houa31:OHHaem we» eH a

2; 1327:: 2 “Home H8225; ”532: 2:3: $335 fin 3.3

.nmumz “unusuamm may we «

mHocaoau umpHu on»

mumcINoue

H :3

14

extended over 9 hours beginning at dusk. On April 13,

April 26, May 16, June 14, July 14, and July 30, small-mesh
trapnets (6.35mm or 0.25 " mesh) with depth of 1 m and a

lead length of 15.2 m (50') were deployed across bayou

mo tithe (Beamish 1972). Trap-nets were set at dusk and

P11 Illed at dawn; the length of deployment ranged between 9

an d 15 hours depending on weather conditions and other

On April 13, and May 16, only two trap-nets

C O matraints.
On all

we re set , one each in bayous X and Y (Figure 1)-.

0t her dates, duplicate trap-nets were set at all bayou

8“: etions.

Ml Fish -- Field sampling

A total of 562 larval fish samples were collected

at.» ring the 1982 field season (Table 2). Sampling occurred

"g ekly May through June, and twice-monthly during March,

AD 2:11, July, and August. Sampling effort was concentrated

in the marsh bayous with a total of 354 samples as opposed
ht) 198 channel samples. Larval fish were sampled in

(:11 annals with a portable push-net device (Figure 2) as
he. dified from previous pilot studies (Liston and Chubb
19 83). Dual bow-mounted conical half-meter (363 11 mesh)

pl ankton nets were pushed upstream at speeds approximating

General Oceanic current meters (model no. 2030)

Q ‘ S m /80
‘1 th high-speed rotors were offset by one-third in the net

aDertures for measurements of water volume. Larval

eseapement was minimized by maintaining moderate speeds

15

 

LII ' ./
collection‘f’vIISHKQa
bucket “J.

 

 

 

 

 

Figure 2. Diagram of the larval fish half-meter (363 u mesh)
push-net as operated from the bow of a small boat
in the channels and bayou-mouths of the Pentwater
Marsh.

100 m

 

 

 

 

 

Figure 3. Diagram of the.drop-net sampler (363 u mesh sides)
as used in conjunction with a meter dip-net in the
shallowdwater bayous of the Pentwater Marsh.

l6

(Alhstrom et a1. 1973) and sampling abbreviated distances

(Clutter and Anraku 1968). Full 50 m push samples were

taken at the side and middle of the north, south, and main

channels and over distances of 10 to 20 m in each of the

four major bayous (Figure 1). Based on the distance of net
6. eployment, ideal filtered water volumes were 11.34 and

3 .2 m3 in channels and bayous, respectively. However,

a ctual volumes were often much less (averaging 5.7 m and

2 .4 m3) due to vegetative interference and net clogging.

A 1though larval densities were usually based on actual

In easured water volumes, when direct estimates were not

a. vailable ideal water volumes or averages of duplicate tows

were substituted. Full day and night series were taken on

11: cat sampling dates, representing a total of twenty-four

& amples per date. However, on April 13, June 1, June 7, and

A ugust 23, channel samples were taken only at night (Table

2).
Although push—nets were utilized to sample at the

b ayou-mouths, the shallow-water bayous were sampled using a

q :rop-net device as modelled after Kushlan (1981). The

R alvanized metal frame meter-box with 363u mesh sides

( Figure 3) was thrown by two operators into targeted areas

( Liston and Chubb 1983). Each sample thus enclosed an 1 111

area and varied in water volume depending on water level at

During 1982, drop-net volumes

the time of sampling.
A sharp

averaged 0.44 m3and varied from 0.10 to 0.66 m .

metal cutting edge along the bottom rim of the net proved of

 

I”!

17

ample weight to cut through dense vegetation and lodge in
soft substrates. The enclosed vegetation was clipped,
washed, and removed. The contents of the drop—net were then
strained with a single horizontal pass of a meter square
conical (363u mesh) dip net. The strained materials were
concentrated and rinsed into liter sample jars with 100 to
150 nfil of formalin preservative. Sampling logistics made
complxetely random sampling unreasonable and inefficient
(King et al. 1981). A stratified sampling heirarchy was
developed with triplicate fixed stations (1,2,3) in each of
the fcnir major bayous (X,Y,W,Z). At each station, single
subsamples were taken in emergent, submergent, and
floatiJJg-leaf vegetation. In this way, a total of nine
(3X3) (drop-net samples were normally taken in any one bayou
and two bayous were completed each week. Any one bayou was
thus sampled by drop-nets at least twice monthly. In April,
drolib-net samples were predominantly taken by day, although a
nigh4; series was also included on April 13. Night samples
were taken on all sampling dates from May 12 through August
3' “Nith day series taken on May 12, May 25, June 1, June 22,
and ~Ju1y 20 for comparison (Table 2). Pull-nets (Liston et
31' 31981b) were also used in the shallow-water bayous.
HOVQVBI‘. this gear was not particularly successful in the
dehSEIY vegetated muck-bottom areas of the upper marsh and
"as not included in final larval fish density estimates.
Preliminary larval drift samples were taken at the

marsh outlet on May 25, June 10 and 23, and July 8 and 20.

18

Each series included 40 minute sets taken every 3 hours over
a 24-hour period. Sets involved simultaneous deployment of
three stationary half-meter (363 u mesh) conical plankton
nets suspended just below the water surface. Two nets faced
upstream and one net was mounted facing downstream to
measure reversed current flow. Sets spanned a complete
40 miJmute seiche cycle which were of regular duration but of
varyiJTg magnitude. Each net was equipped with an inverted
conical insert (363 u mesh) at the collection bucket
apertirre which decreased loss of materials due to back
flushirrg during current reversal. Nets doubled over during
reversed flow, and presumably were operative only during
periods; of current flow through the net aperture.
Theoretically, downstream nets fished only when upstream
nets were inoperative. However, there was often a period of
1038 (If flow at the time of current reversal when neither
“9t ‘vas in operation. Larval fish drift was expressed as
numbters of larvae/m2 cross-sectional area/hour. Export and
imPort values were approximated by addition of drift rates
over 1a 24-hour period and multiplication by the total
Cr°SEB--8ectional area (48 m2) of the channel. On June 30,
Ian'al drift from Pentwater Lake to Lake Michigan was
measured with stepped-oblique tows of conical meter (363u
mesh) Plankton nets (Liston et al. 1981a). Both day and
night series of four replicates each were taken across the
harbor outlet. In addition, Pentwater Lake densities were

eStimated based on duplicate two-minute (approximately 50 m)

19
push-net tows at lake middle and side. Lake samples were
taken only on the selected dates of June 23, July 7, and

July 20 and included both day and night series.

Larval Fish-- laboratory

Upon collection, samples were immediately preserved in

a 10% formalin solution. In the laboratory, entire samples
were sorted for fish larvae and eggs over both light and
dark backgrounds using a 10x power illuminated magnifier.
Occasixanally, subsamples were necessary for egg enumeration
and were taken with repeated divisions by a Folsum-plankton
splitter. However, fish larvae were always counted
directlyu Both larval fish and eggs were stored in
Davidson's solution to await enumeration and identification.
Most larvae were identified to species with the aid of a
Variety of taxonomic keys (Mansueti and Hardy 1967; Lippson
and lloran 1971; Dorr et a1. 1976; Auer 1982). Both
CYPITlnids and Lepomis spp. were not separated to species
due 1:0 difficulties in positive identification at certain
larvlll phases. Larval length was measured from snout to the
caudal fin tip , and was recorded to the nearest 0.1 mm
under‘ti binocular zoom microscope with occular micrometer.
F9? Species in high abundance, at least twenty individuals
were subsampled in proportions representative of the
distribution of size and developmental stages in the total

8a“P18. Larval lengths were later partitioned in 0.5 mm

increments for computer length-frequency analysis.

20

Developmental stages were categorized as protolarval
(lacking distinct median fin elements), mesolarval (with at
least one, but not full complements of principal rays in the
median fins), metalarval (with full complement of principal
rays in the median fins and pelvic fin buds apparent), and
juveniles (with the full complement of fins and fin
elements) (Snyder 1976). The term "yolk-sac" larvae is used
in reference to individuals with clearly definable
yolk-material. Yolk-sac larvae may or may not correspond to
the protolarval stage depending on the particualar

developmental patterns of the species.

Win

At the time of sampling, weather patterns were noted and
PrEdominant physical and chemical features were measured and
recorded according to standard methods (A.P.H.A 1976).
Weekly precipitation data were obtained from the nearest
Climatological NOAA station (no.3632) located in Hart,
Michligan. Great Lakes water levels were estimated from
rec(Hi‘ds at the Ludington NOAA station (no. 7023). Radiation
or ambiant light levels were roughly approximated as a
percent of the theoretical maximum. Factors such as the
angle 0f sun or moon (A- 2 maximum from horizon), moon phase
(1" coded; 1 for sun, 0.25 for full moon, 0.13 for
half-moon, and O for new moon), and cloud cover (C- 2 open

3k!) were combined into a single value (RAD) where:

21
RAD - (A)x(C)x(P)

Temperature measurements were taken with a calibrated
stick thermometer suspended midway in the water column.
Water was collected by VanDorn sampler for later chemical
analqysis of turbidity (Hach Turbidimeter #16800), pH (Hach
kit inadel 17-H) and dissolved oxygen. Water for dissolved
oxygen measurements was fixed in the field according to the
azide-modified Winkler method, refrigerated, and titrated in
the lash within 24 hours of collection (Lind 1974). Water
depth and vegetative structure were recorded at all drop-net
statixans. Vegetation was characterized by visual inspection
of the: relative species composition by volume and by surface
area. Measurements of the wet weight of emergent,
submergent, and floating-leaf vegetation were also included.

Remote sensing provided the basis for vegetation
mapping. On July 11, the Michigan State University Remote
SenSing Laboratory took air photos at a 427 m (1400')
ele\Vation over the Pentwater Marsh. Color film was used to
disthinguish between vegetation types due to its superior
qualdities of water penetration. The marsh boundary, as
defined at 10 cm water depths, coincided with emergent plant
denSities of 50 to 75 stems/m3 and was identifiable in color
infl'aredimagery. Both vegetation types and marsh
boundaries were checked by ground-truthing through July 20.

Although plant species, structure, and density may change

through the growing season, the major vegetation types as

II.

‘ 1
5

 

22

described did not fluctuate significantly in area or
locality.

A base map (scale 1cm- 19.8 m) was prepared from a 1980
Agricultural Stabilization and Soil Conservation Service air
photo»(Hart, MI). Major regions and vegetative types were
delineated and measured by triplicate dot-grid counts of the
mapped area (Seher and Tueller 1973). Emergent and
submergent interspersion was measured by the shoreline

develxapment formula (SLD) (Lind 1974) where:

SLD - S/J2 Na
8 - "shoreline" length along emergent edge
a - area of bayou or designated sample region

The shoreline development value would be unity for a perfect
circle. Values greater than one indicate increasing
irregularity of the emergent/submergent boundary. Values
1988 than one are possible where the emergent edge is
incOlnplete or broken by open water as in bayou W. Emergent

8hOfeline length was estimated from three trial passes of a

Post» mechanical cartometer.

WW

Larval fish catch and all corresponding
c-hemica1/physical data were coded for analysis on
microcomputer (Apple II+). Specialized programs in

Microsoft basic were developed to transform larval catch

23

into volumetric and areal density estimates. Areal density
estimates (#/m2) were used to calculate standing crop (#/HA)
as weighted by the present coverage of major vegetation
types in the marsh. Volumetric larval fish densities (#/m3)
were used in all statistical comparisons. Parametric
statistics (Students-t) were routine for larval fish
lengths, gear efficiency estimates, and environmental
parameter analysis (Gill 1978). Larval fish densities

followed a negative binomial pattern of distribution.

 

However, standard errors ( NAR7Sample size ) were
calculated as approximations of error bounds. Coefficients
of variation (SD/Mean) were utilized both for gear
Performance evaluations and for descriptions of larval fish
Patterns of distribution. Non—parametric statistics
included the Mann-Whitney-U test and the Kruskal-Wallis
mUltiple sample test and were used to evaluate differences
in larval fish densities between dates, stations, vegetation
tYpes, and day and night (Siegel 1956). Unless stated
°therwise, both parametric and non-parametric statistical
comParisons were considered significant at confidence levels
SrEater than 90%. At 90% confidence levels and at the given
Ba“‘Pling intensity I could discriminate differences in the
means of approximately 501 which seemed reasonable for
discussion of biological meaning.
Spearman-rank correlations were employed to define

relationships between larval fish densities and ambient

environmental conditions. Northern pike (Esox lucius) and

24

yellow perch (Pg;gg_flavescens) were in sufficient abundance
for analysis only during May 12 through May 25. Cyprinids
were included in correlations of May 25 through June 22, and
pumpkinseed sunfish (Lepomis gibbosus) were analyzed against
environmental parameters on June 8 through June 22.

Larval fish community patterns were described with the
Shannon-Weaver indices of diversity (H'), species richness
(D), and species evenness (J) where:

(pi) x 1n(pi)
)/1n (N)

H' -
D .1
J

I
in“!

Siven: pi . the proportion of individuals of the ith

species
S- the number of species in a sample unit
N- the total number of individuals

SPeCies richness measures the number of species, whereas
3PeCies evenness describes the degree of dominance among
Specx1es groups. Both species richness and species evenness
are :reflected in the overall value of species diversity; the
greater the numbers of species and the higher the evenness
all”“8 Species, the higher the diversity value. These values
“SIS! calculated for both individual samples and larval fish
data pooled across dates, regions, stations, and vegetation
tYpes.
Associations among larval fish species were described

“3138 Forbe's coefficient (cf) (Cole 1949) where for species

A and B:

25

cf- (ad-bc)/ ((a+b)x(b+d))

a a # samples where both species present

b - # samples where only species A present
c - # samples where only species B present
d - # samples where both species absent.

Forbe's coefficient values of 0 indicate chance association,
whereas values of 1 and -1 indicate complete association and
disassociation, respectively. Evidence of association and
disassociation may indicate direct species interactions such
as competition, predation, or avoidance. However, indirect
mechanisms of habitat preference or passive transport can

also account for these values.

RESULTS

PHYSICAL, CHEMICAL, AND HABITAT PARAMETERS

Rainfall, Water Levels, Water Depths

Weekly precipitation was high in April at over 23 cm
but rapidly declined to 0.3 cm by early May (Figure 4).
From May through August weekly rainfall fluctuated greatly,
while the monthly average steadily increased. As indicated
by measurements taken at the shallowest station (1) in bayou
W, marsh water levels rose by about 20 cm April through
mid—May and then declined by 10 cm during early June. From
June through July water levels gradually returned to the
spring highwater mark. August water levels declined by
about 5 cm. Lake Michigan mean daily water levels showed a
similar late summer increase as shown in Figure 4.

Water depths ranged from 2.0 m in the river channels to
10 cm at the effective marsh boundary as defined. Channel
stations were approximately 1.5 m at mid and 0.5 m at side
channel. Bayou station depths ranged from 10 to 66 cm
depending on water level fluctuations of the marsh

(Appendix A.1)). Bayou Z was the shallowest of the sample
26

27

 

=O><m 2E.

Fan in... .92
..... scam: 5E3

 

 

.0 4w a;
.80.

E 553 1|.
2. .3383 3 3033

(mm—2k tame-55.302 111
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Aw 9. nu
-
‘D““““‘ A
A-.. FFFFFF
U.
\\\\\
AM J

I, /f\d/‘\
II J
TIME (maths)

Meteorological and hydrological conditions

of the Pentwater Marsh during 1982.

Figure 4.

28

regions as reflected in average station depths (Appendix
A.2). Day stations tended to be slightly deeper than those
taken at night (p<0.10) perhaps reflecting some bias in
choice of sample sites within designated regions. Emergent
vegetation was significantly (p<0.10) shallower than
submergent and floating-leaf stations, often by 10 to 20 cm
on any sample date (Appendix A.3). In fact, station depth
was negatively correlated with percent emergent cover
(r--0.30; p<0.01) and positively correlated with
floating-leaf cover (r-O.20; p<0.01) (Table 3).

Water Temperature

In general, Pentwater Marsh water temperatures rose
steadily throughout the field season. However, a mid-May
warming trend was followed by a cold spell of several weeks
as measured by temperature averages at bayou drop-net
stations (Figure 4). Lowest temperatures of 2 0C were
encountered in early April in the shallow water bayous
(Appendix A.1). Warmest temperatures of 30 0C were measured
in August at the same locality. For most sample dates and
stations, night temperatures were greater than day
temperatures by as much as 2 oC. Night series were taken
soon after dusk when shallow water bayous still retained
much of the day's heat. Day samples were generally
completed before the midday sun. Maximum differences
between day and night temperatures were encountered in late

July, particularly in the shallow-water bayous. As

Table 3.

29

Spearman-rank correlation of depth (m) with other

physical/chemical parameters as measured at bayou drop-net

stations during 1982 (n-120).

 

 

CORRELATION

COEFFICIENT T—VALUE
PARAMETERS r t significance level1
time -0.02 -0.22 NS
light 0.14 1.61 NS
temperature 0.10 1.03 NS
turbidity 0.12 1.32 NS
D0 0.21 2.44 ***
Zveg. cover -0.07 -0.82 NS
Zemergents -0.30 -3.53 ***
Zfl. leaf 0.20 2.25 ***
Zsubmergents 0.06 0.62 NS

 

1 *** p<0.01

Table 4.

; ** p<0.05

p<0.10; NS p>0.10

Spearman-rank correlation of temperature C’C) with

other physical/chemical parameters as measured at bayou
drop-net stations during 1982 (n-120).

 

CORRELATION

COEFFICIENT T-VALUE 1
PARAMETERS r t significance level
time 0.12 1.35 *
light -0.05 -0.59 NS
turbidity -O.12 -1.36 *
D0 —0.20 -2.24 ***
depth 0.10 1.03 NS
Zveg. cover -0.07 -0.74 NS
Zemergents -0.14 —1.62 *
Zfl.leaf 0.01 0.10 NS
Zsubmergents 0.13 0.34 NS

 

1 *** p<0.01

: ** p<0.05

p<0.10 ; NS p>0.10

30

expected, Spearman-rank correlations were significant
(r-0.12; p<0.10) between water temperatures and the time of
sampling (Table 3). By both day and night, the
shallow-water bayous were usually warmer than both the
bayou-mouths and channels. On July 20, the bayous averaged
25.8 0C or nearly 6 oC greater than the channels
(Appendix.A.1). Comparisons between channel stations
indicated the north branch was generally 1 to 30 C cooler
than the south branch and main channels(Appendix A.4).
Channel temperatures differed little between day and night.
The mid channel stations were usually cooler than side
channel stations, particularly by day. This difference was
most pronounced by late July when the average water
temperature of side stations was 2.7 0C warmer than at mid
channel (Appendix A.5).

No significant relationships (p>0.10) were apparent
between water temperature and the major bayous
(Appendix.A.Z). Perhaps other factors, such as the time of
sampling and vegetative structure, were of greater
significance (Table 3). Daytime submergent samples tended
to be 1 oC warmer than samples of emergent and floating-leaf
areas (Appendix A.3). A 24-hour temperature profile taken
across depth and vegetation types on September 9, 1983,
illustrated the greater daytime temperatures of submergent
beds, and emphasized the need for complete depth profiles
even in water less than 1 m in depth (Figure 5). Dense

submerged vegetation may act as a solar collector heating

31

FLOATING-LEAF

 

 

20

 

 

10
900 1500 2100 300 3900
~~TOP TIEOIous)
-—BOTTOM

Figure 5. Temperature profiles for each of the major
vegetation types (n'3) as recorded in bayou
W, on September 9, 1983.

32

the upper water layers by day and radiating heat to the
lower depths by night. Floating-leaf vegetation was
generally cooler, suggesting a shading effect by day and
less heat retention by night (Appendix A.3). Emergent
vegetation experienced a relatively constant temperature
over 24 hours and even less variation across depths (Figure

5).

Dissolved Oxyggg

Unlike water temperature, dissolved oxygen showed no
marked seasonal patterns. Average marsh dissolved oxygen
levels remained between 5.0 and 10.0 mg/l throughout much of
the season (Appendix A.1). although individual measurements
ranged from 1.3 to 13.9 mg/l. In general, dissolved oxygen
levels were lower at night than by day, particularly in the
shallow-water bayous. A 24 hour dissolved oxygen profile of
September, 1983, showed bayou dissolved oxygen peaked around
1500 hours and reached a nighttime minimum around 300 hours
at night (Figure 6). During bayou sampling of 1982,
dissolved oxygen measurements ranged from 1.3 to 12.5 with
the lowest values obtained at night. Channel dissolved
oxygen varied less than bayou dissolved oxygen remaining
within the bounds of 5.0 to 11.8 mg/l by day and 6.0 to
13.9 mg/l by night (Appendix A.1). Channel dissolved oxygen
was often significantly greater (p<0.10) than bayou levels
at night. Dissolved oxygen levels were higher at mid versus

side channels by both day and night (Appendix A.5). North

33

 

............
...........
............
-----------
.....

     

[3 SURFACE ..
MID
I BOTTOM

15

  

 

1.0 loo... ..... scion. ..... 5 ""TJ_- .
E ocean’s-00'?” 0.00.2000. 00000 o ...... f.-

DEPfliflfll DEEMIJRIMOKYGENRMOAJ
0|

 

o
2 3 4 6
UPPER sAvou . LOWER BAYOU
lunKlJSTAIIJEB

Figure 6. gisgolvedwoxygen levels across sample stations
ayou , as recorded over 24 h
September 9, 1983. ours on

34
branch dissolved oxygen was somewhat higher than that of the
south branch and main channels by day but not by night
(Apendix A.4). Cooler north branch water temperatures may
have been responsible for this pattern.

Dissolved oxygen was related to a number of local
conditions including water temperature (r- -0.20; p<0.01),
depth (r-0.22; p<0.01), vegetation type (fasting-leaf:
r-0.14; p<0.20 and submergents:r--0.10; p<0.20), radiant
light levels (rs-0.30; p<0.01) and the time of sampling
(r--0.17; p<0.10) (Table 5). The major marsh bayous did not
differ significantly (p>0.10) in dissolved oxygen readings,
although bayou W appeared to have somewhat higher nighttime
levels (Appendix A.2). Emergent and floating-leaf
vegetation types had higher daytime dissolved oxygen levels
than submergents (Appendix A.3). Nighttime dissolved oxygen
was generally highest in floating-leaf vegetation. A
24-hour dissolved oxygen profile on September 9, 1982,
illustrated a trend of higher oxygen levels in surface
waters across all vegetation types and sampling periods
(Figure 7). Submergent vegetation obtained the greatest
dissolved oxygen differential across depths and between day

and night (Appendix A.3).

Iprbidity and pH
Turbidity as measured, showed no significant patterns
across day/night, depths, or bayou stations (Appendix A.1).

There was a general increase in turbidity through the

35

Table 5. Spearman-rank correlation of dissolved oxygen
(mg/l) with other physical/chemical parameters as measured
at bayou drop-net stations during 1982 (n-120).

 

 

CORRELATION

COEFFICIENT T-VALUE 1
PARAMETERS r t significance level
time -0.17 -1.92 *
light 0.30 3.56 ***
temperature -0.20 -2.24 ***
turbidity 0.06 0.69 NS
depth 0.21 2.44 ***
Zveg.cover 0.02 0.21 NS
Zemergents 0.05 0.55 NS
Zfl.leaf 0.14 1.59 NS
Zsubmergents —0.10 -1.12 NS

 

1 *** p<0.01 ; ** p<0.05 ; * p<0.10 ; NS p>0.10

36

.s
O

DISSOLVED OXYEN (mg/l)

 

Figure 7. Dissolved oxygen levels across marsh vegetation
types and water depth, as recorded over 24
hours on September 9,1983.

37

season, perhaps due to an accumulation of detrital materials
that were easily suspended during collection procedures.
Mean marsh turbidity varied between 2.0 and 10.0 NTU. Bayou
turbidities were quite variable, ranging from 0.3 to 36.0
NTU. On most sample dates, mean water turbidity within
submergent vegetation was significantly lower (p<0.10) than
that of emergent or floating-leaf vegetation (Appendix A.3).
Channel turbidity was more uniform and ranged from 0.9 to
9.5 NTU. The north branch water was stained a dark brown,
probably due to high levels of dissolved organics from
upstream bogs and swamps. The south branch was
characterized by sand and silt deposits with less water
coloration and higher water turbidity (Appendix A.4). Water
turbidity seemed to increase in conjunction with storm
events and water discharge from the reservoir 25 km upstream
from the marsh.

Ph values ranged from 6.0 to 8.8 NTU at sample stations
of the marsh. Water samples were most alkaline in May
through June, becoming increasingly acidic through summer
(Appendix A.1). Although regional, day/night, and
vegetational comparisons did not indicate statistically
significant differences (p>0.10), several patterns were
Observed. PH appeared to be highest by day, particularly in
the bayou-mouth samples. Of all the vegetation types,
submergent vegetation tended to be the most alkaline by day

and most acidic by night (Appendix A.3). Similarly, side

38

channel stations had higher pH values than the mid channels

by day (Appendix A.5).

Vegetative Cover

 

Total vegetative cover was measured by the 2 volume of
all vegetative types in drop-net samples of the shallow-
water bayous. Sample values ranged from 0 to 80% and the
bayou mean ranged from 32 to 50% over the sample season.
Total vegetative cover did not follow a seasonal trend;
rather, bayou vegetation repeatedly attained peak standing
crops in April, early June, and late July (Appendix A.1).
Although, as discussed earlier, sample depths were lower at
night than by day, vegetative cover did not vary greatly
between the two sample periods. Comparisons among bayous,
indicated that bayou Y typically had higher total vegetative
cover (Appendix A.2). Total vegetative cover was
significantly correlated (r=0.31; p<0.01) with percent
submergent cover but not other vegetative types
(Appendix.K.1). On most sample dates, total vegetative
cover was higher in samples designated as submergent beds
(Appendix.A.3). Total vegetative cover in emergent beds
declined over the sample season whereas the vegetative cover
of samples in floating-leaf and submergent beds did not peak
until late July. Field workers observed that emergent
growth peaked by late May, when floating-leaf vegetation was
only beginning to grow. Growth of submergent vegetation

began earlier in May and was observed to peak repeatedly in

39
early June and late July. An early spring pulse of

Potamogeton crispus was later replaced by luxuriant growth

of Elodea canadensis, Myrigphyllum sp., and Potamggeton

 

filiformis. Blue-green filimentous algae (Spyrogyra spp.)

 

also became a significant component of the shallow-water

bayous in late July through August.

FISHES

Gear and Laboratory Efficiency Tests
Drop-net efficiency tests run for eggs and larvae in
June, and post larvae in late August, were examined to
determine the utility of adjustments in density estimates
(Table 6). The efficiency of sampling fish eggs by drop-net
was estimated at 681 11%. Laboratory picking efficiency
(881292) differed significantly between individual pickers
(p<0.01) (Table 7). It is probable that eggs were routinely
overlooked when adhering to sample vegetation, and
consequently, numerical egg estimates were not included in
this analysis. Drop-net efficiency tests showed no
significant difference (p>0.10) in larval efficiencies
across vegetation types, day/night, species or larval phase
(Table 6). Average drop-net efficiencies were estimated at
851:22 retrieval. However, larval retrieval was
significantly lower (p<0.01) in shallow depths of less than

0.30 m. Larval fish picking efficiencies averaged 991- 4%

 

40

Table 6. Summary of drop-net efficiency testing conducted
on eggs, larvae, and juvenile fishes of the Pentwater Marsh
during June and August of 1982.

 

SAMPLE MEAN SIGNIFI TorF
TREATMENTS SIZE EFFICIENCY STD.ERROR LEVEL VALUE

 

EGG RETRIEVAL:
all 18 0.68 0.11

 

 

LARVAL RETRIEVAL:

 

 

all 52 0.85 0.02

day 16 0.85 0.04

night 18 0.80 0.05 NS 1.01
Vegetation-types:

emergent 9 0.87 0.04

submergent 9 0.92 0.04

float-leaf 9 0.96 0.02 NS 0.32
Station depth:2

shallow 6 0.78 0.02

deep 8 0.90 0.04 *** -3.39
Developmental stage:

mesolarvae 18 0.79 0.04

metalarvae 18 0.85 0.04 NS 0.89
Fish species:

Lepomis spp. 11 0.82 0.08

cyprinids 36 0.82 0.03 NS 0.10
JUVENILE RETRIEVAL;

Sampling technique:
pull-up 22 0.74 0.02
pull-across 30 0.60 0.03 *** -3.57
Species:

Large M.Bass 5 0.81 0.06

Yellow perch 5 0.80 0.12

Northern pike 5 0.67 0.15

 

l *** p<0.01; ** p<0.05; * p<0.10; NS p<0.10
2 shallow water less than 30 cm; deep water greater than 40
cm

41

and differed little (p>0.10) between drop and push samples
or between individual pickers (Table 7). Repicks
represented over 52 of the total samples taken during 1982.

A horizontal dip-net technique, as used through 1982,
was tested against a four-corner vertical pull on juvenile
fishes in August. Juvenile drop—net efficiencies improved
significantly from 60: 3% to 74: 2% with the new
modifications of method, and subsequent sampling in later
years included the improved technique. Retrieval
efficiencies differed significantly (p<0.10) between the
juvenile fish species sampled. For example, largemouth bass
(Micropterus salmoides) efficiency was estimated at 811_6Z
in contrast to brown bullheads (Ictalurus nebulosgs) at
371112. Drop-net sampling for post-larval fishes was
considered inadequate for detailed analysis of abundance or
distribution without additional sampling modifications or

increased field efforts.

Fish Spawning Activity

 

Trap-net and gill-nets set from April 1 through August
9, 1982, collected 475 juveniles and adult fish (Table 8).
Major adult fish species, in descending order of numerical
catch, included white suckers (Catostomus commersoni), brown

bullhead (Ictalurus nebulosus), yellow perch (Perca

 

flavescens), and various cyprinids. The cyprinid complex

 

included golden shiners (Notemigonus crysoleucas), spottail

 

shiners (Notropis hudsonius), bluntnose minnows (Pimephales

 

 

42

Table 7. Summary of egg and larval fish picking efficiency
based on 52 repicks of 1982 ichthyoplankton samples.

 

 

 

SAMPLE MEAN SICNIPI TorF
TREATMENTS SIZE EFFICIENCY STD.ERROR LEVEL VALUE
EGGS:
all samples 112 0.88 0.29
drop-net 50 0.91 0.26
push-net 62 0.86 0.30 NS 0.93
picker#1 39 0.98 0.03
2 18 0.83 0.37
3 17 0.68 0.44
4 11 0.76 0.39
5 21 0.92 0.23 *** 4.08
LARMAE;
all samples 112 0.98 0.04
drop-net 50 0.99 0.05
push-net 62 0.99 0.03 NS 0.96
picker#1 39 0.99 0.02
2 18 0.99 0.02
3 17 0.95 0.01
4 11 0.98 0.03
5 21 0.98 0.04 NS 0.95

 

1 *** p<0.01; ** p<0.05; * p<0.10; NS p>0.10

43

 

 

 

nwfim NOW HO mQHHcm>=H mmfifiHUGN h
:OHUNvGOU Havwdow QQNH HO nmfiw mmvflHUQN M
uwfllHHHw MO uflm hflonla mwv:HUGH N
hHEO uwm HOGIHHfiw OHanHfl> “OOH Om H§O£IG H
Nmm 0H N « m .m «H 0H NH 0H oN on mm no He ow mmH NON Hun—om.
mHH N I I I Hm Hm Hm I I I H,« HN HHH NN «Hm I Nm NonmIN
ooH I H I N m o m I N N NON HH 0N «N m NN cm NwI«HIN
we I I I I I I I mmH I H m« mmH mN I moH H H« NwI«HIo
«o I I m« I I I I I H I I N« «2 I NH mN NH NwIcHIm
m« H H I I I I H I mN NH I H N o « mmH mN NwIcNI«
No N I I I I I N I ~HmH « H I « I H mom mN NNmImHI«
HN c I I m I I I I H H H N H « I ~HN m HNmIHI«
J. &. uuomwm mums

209 one

2 0

a, some

 

 

.NmoH .HHaa tweets» Hsea< sate
swam: umumzusmm ecu cH mumm umcIHHHw was umqumuu Ho uuouuo was :uumu HmUHuoasz .m memB

44
notatus), mimic shiners (Notropis volucellus), and common
shiners (Notropis cornutus). Golden shiners were clearly
the dominant cyprinid throughout the season. Other species
such as the common carp (Qyprinus carpio), bowfin (Agig
£1ll§)1 northern pike (Esox lucius), central mudminnow

(Umbra limi), largemouth bass (Micropterus salmoides), black

 

crappie (Pomoxis plgpgmaculatus), and pumpkinseed sunfish
(Lepomis gibbosus) were likely present in greater numbers
than indicated by the catch. Passive gear such as trap—nets
and gill-nets appeared to be of decreased efficiency in the
densely vegetated shallow-water bayous of Pentwater Marsh.

The magnitude and duration of spawning activity was
estimated by the relative abundance and gonadal condition of
adult fish. Major spring spawners were identified as the
white sucker, northern pike, yellow perch, black crappie,
gizzard shad, and eastern mudminnow. White suckers were
first to congregate in the marsh when water temperatures
were approximately 4()C in early April. Northern pike were
also present in early April and two spawning pulses were
observed on April 13 and April 26. Ripe yellow perch were
present throughout April and the beginning of May. Spawning
activity and egg masses were observed only in bayou W. Ripe
black crappie were primarily caught in the trap-nets of
bayou W and gill-nets of the main channel from May to
mid-June. Adult gizzard shad were caught on the night of
May 16 near the main channel station. Based on the ripe

spawning condition of these fish and the appearance of

45
gizzard shad eggs in the ichthyoplankton collections,

spawning activity probably peaked in late May and extended
into mid-June. Eastern mudminnows were occasionally caught
in trap—nets but were more commonly observed in drop—net
samples of the shallow-water bayous (Table 9). A total of
44 mudminnows were caught by drop-net from April through
July with peak concentrations of ripe adults on May 12 and
May 25.

The observed summer spawners included cyprinids,
pumpkinseed sunfish, brown bullheads, and alewife.
Bluntnose minnows began spawning at the end of May, while
ripe golden shiners were not found until late June.
Pumpkinseed sunfish were rarely captured in nets but were
observed guarding young within the shallows of bayous W and
X in late June. At this time pumpkinseed sunfish nesting
activity was concentrated around the rip-rap of US Business
Route 31 and Long Bridge Road to the north and west of
bayou W. Brown bullheads were prevalent throughout the
summer with the greatest number caught at the end of July in
bayous X and Y. Bullhead spawning activity was observed
through much of July with an occasional guarding male

captured in drop-nets of the shallow—water bayous (Table 9).

_L§rval Fish Abundance and Distribution
From April 13 through August 23, a total of 3,926

larval and juvenile fishes were collected in drop, pull and

46

Table 9. Numbers and species of post-juvenile fishes
captured in bayou drop-net sampling in the Pentwater Marsh
during 1982.

 

 

 

Q Q Q)
go (Vt (3‘ . (ft
‘8 Q. g. Q Q
Sr % \> 1% Q
s o x» Q G: s
o Is ‘9 ‘9
Q s Q N} If? ‘9‘
1‘ 1? s- 9 ~p SP 1%
° \> 0 ‘N
9 ~13 0“} V <1 6" *2" (J 9
«v o <%' 49 (5» s. 69 (pg:
1% 3*%
Date 9
4-13-82 3 - — 1 - - - -
5-12-82 5 - 1 1 - - - -
5-25-82 21 5 - - — — 1 -
6-1-82 8 - — — 1 - - -
6—8-82 — — 2 - - - - 1
6-22—82 4 3 - 1 - _ _ _
7-7-82 - - 1 - - — - —
7-20-82 3 - - - 1 1 - -
8-3-82 — - 1 - - - - -
8-23-82 - - — - - - - -

 

Total 44 8 4 3 2 1 1 1

 

 

47

push nets in the bayous and channels of Pentwater Marsh
(Table 10). There was a succession of larval species from
the early spawners of white sucker, northern pike, yellow
perch, and black crappie, through a June maximum of gizzard
shad, pumpkinseed sunfish, cyprinids, and common carp
(Figure 8). These late-spawned larvae composed over 90% of
the season's total larval catch (Table 10). Although not
directly enumerated, an estimated 3,350 fish eggs were
collected primarily in the marsh channels. Protolarvae
represented approximately 43% of the larval catch with the
remainder composed of 42% mesolarval and 15% metalarval
fishes. Only 32 juvenile fish were captured by push and
drop-nets.

Throughout the sampling period, nighttime larval fish
densities generally far exceeded daytime densities. Night
larval fish densities ranged from three to six times the
corresponding day densities of the bayous (Appendix B.1).
Day and night larval fish densities in channels often
differed by a factor of ten. Peak seasonal larval fish
densities (meaniSE) of 3.5: 1.5 and 26.0: 7.6 larval fish/m3
occurred on June 8 in the channels and bayou-mouths,
respectively (Figure 9). On June 22, a peak density of
64:88 larvae/m3 was found at the upper bayou drop stations.
A secondary peak also occurred around May 25. The peak
seasonal density was highest in bayou Y at 203: 400 larvae/m3
followed by bayou W with 142+ 102 larvae/m (Figure 10;

Appendix B.2). Peak densities were substantially lower at

48

.nmums ecu Ho moHoosm HmHucmeHmmu mmuocme memmumm 6Q
“cme20Hz mme can zooms on» cmozumn mwcmu Nos :UH:3 moHuoom uconcmuu **
mome Loomsucmm and :mum: umumzucom cmoxumn omens Nms nuch moHomom *

 

No.0 H I
No.0 H I
No.0 H I
no.0 N N
N.o o H
m.o HH m
m.o OH m
o.o Hm I
N.o 0N I
o.o mm «m
H Nm mN
H m« m
N NN o«
N Nm Nm
« NoH ««
OH mmm H«
NN oHom mm«H

 

owes eases smz1mm=a

N

no umHH ecu .Azoumu Ho Nocoscoum NV :oHuHmoosoo moHooqm .coumo HmuHuoasc one

=UH<U

oN

cmN
NwH

Io—(v—iv-l

ow

cm
onH

HMZIHHDm PWZIQONQ

 

mscmcquv msHsvasm

 

msuumaoomHeo wwwddmmwm.

 

mcmumcoocH mmHsu
Lessee masses

 

 

mamOHsno: mauswmuoH

 

meHOEHmm mfiumunOHUHz

 

Hcomummmoo adsoummMfiq.

 

msHusH Room
mfiHmw.st<

 

msHsoon monumoanmH
ssumH: mwoumomaum

 

 

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mcmomm>me mdeM.

 

mzanoounomm1mHsommq

msmoanHm mHEONMH

 

mflufiflhou mHQOHUOZ

 

msHHoosHo> mHoouuoz

 

msHaomvsn mHmouuoz

 

msumuo: mOHmnommHm

 

mmosmHomNmo macomHaouoz

 

msucmumnoemsmo mm0H<

 

sscmHemowo msomouon

QNQHMW.m=:Hu

 

mz<z UHmHHzmHom

:mHmHHHHx amazon
comma usouu
xumanquum xooun
:HaHsum eOHuuoa
emmcHHsn aroma
moms cusosmwmmH
** umxosm muH:3
* mxHq sumnumo:
ceron
ovanm>HHm xooun
mousse Nuance
* mHoommu somHn
noses onHmN
HHdeeHe
emomconssa
“ROHQEOOIMMHMNMJ.
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umchm :oeHow

"mchHuoNo
** OHH3OHm
* emnm vumNNHw
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** ammo coasoo

 

mz<z zozzoo

.commmm OHosmm NmoH mam wchsv
:mumz mmumsuemm ecu cH umumucsouco moHomom :me Hm>umH Ho moss: OHHHucoHom cam coasou

.oH mHnt

........... NH

 

........ ..........

.....
......
CCCCCCCC

 

 

 

       

......
Con-"o". ccccccccccccccccc

.ux

MAY

Relative abundance and monthly occurrence of
larval fish species in the shallow-water

bayous of the Pentwater Marsh.

Figure 8.

50

 

 

................
oooooooooooooooooooooooooooooooooooooooooooo

 

 

\
a; 40 .......
E BAYOU
20
2
g BAYOU'MOUTH
O M WEI.

Figure 9. Total nighttime larval fish densities as
measured by push-nets in the channels and
bayou-mouths, and drop—nets in the shallow—
water bayous of the Pentwater Marsh.

51

night

§.

 

TOTAL u= newsrrv (M113)
8

 

FigurelO. Total nighttime larval fish densities as
measured by drop-net and push-net sampling
in the major bayous (X, Y, W, and Z) of the
Pentwater Marsh.

52
38: 29 and 14i 20 larvae/m3 in bayous Z and X, respectively.
On most sample dates, and by both day and night, higher
densities of larval fish were encountered in emergent rather
than submergent or floating-leaf vegetation types (p<0.01;
Appendix B.3). Channels attained peak densities of 8.51 2.2
larval fish/m3 in the main channel but only 1.8: 0.3 and
1.0:0.3 larvae/m3 in the south and north branches,
respectively (Figure 11; Appendix B.4). In general, total
larval fish density was greater at mid rather than side
channels (Appendix 8.5).

Examination of mean larval densities must also include
discussion of variance. As already indicated, standard
errors were substantial, sometimes exceeding the mean by as
much as 200%. Larval fish coefficients of variation (S.D/
mean) ranged from 0.6 to 6.1 with a general trend of
increasing values through the sample season (Appendix D.1).
Variance remained high, while mean larval densities declined
soon after June. Throughout the season, night drop-net
samples exhibited significantly (p<0.01) greater
coefficients of variation as compared to the push—nets of
the bayou-mouths and channels (Table 11; Appendix E.1).
However, greater (p<0.01) coefficients of variation occurred
in the bayou-mouths than both shallow-water and channel
regions by day. Although differences in gear efficiencies
may be reflected in coefficients of variation, the daytime
comparison of push-nets in channels and bayous indicates

these values may also represent real differences in the

53

ooooooooooooooooooooooooooooooooooooooooooooo

TOTAL LF DENSITY (111/1113)

 

Figure 11. Total nighttime larval fish densities as
measured by push-net sampling in the north
and south branch and main channel of the
Pentwater Marsh.

54

Table 11. Mean coefficients of variation (S.D/mean) and
estimated sample size to detect differences in larval fish
densities by day and night, and across marsh regions and
vegetation types.

 

 

 

 

 

SAMPLE SEASONAL 1 ESTIMATED
SIZE MEAN CV TorF SAMPLE2
TREATMENT (# dates) (mean CV +SE) VALUES SIZE
BAYOUS;
night 9 2.55 + 0.57 52
day 5 1.45 + 0.23 1.38 NS 17
BAYOUS-MOUTHS:
night 6 0.93 + 0.11 7
day 4 2.56 + 0.41 -3.04 *** 52
CHANNELS:
night 6 1.17 + 0.27 11
day 4 1.88 + 0031 -1070 * 28
Night:
emergents 8 1.08 + 0.42 ' 9
submergents 8 1.09 + 0.08 10
fl. leaf 7 1.08 + 0.12 1.01 NS 9
Day:
emergents 5 1.00 + 0.81 8
submergents 5 1.23 + 0.13 12
f1. leaf 5 2.94 + 1.92 4.81 *** 69

 

1 *** p<0.01 ; ** p<0.05 ; * p<0.10; NS p>0.10
2 to detect at least a 50% difference in mean densities with
90% confidence (p>0.10).

55

heterogeneity (or patchiness) of the larval fish
populations. If so, the bayou-mouths may have experienced
the greatest day and night differential, with increased
heterogeneity by day. Coefficients of variation differed
little across vegetation types, particularly by day
(Table.1l). However, night samples in floating-leaf
vegetation had the greatest (p<0.01) CV values indicating a
less uniform larval fish distribution than prevalent in

submergent and emergent areas.

CARP

A total of 3,010 carp larvae (Cyprinus carpio) were
collected between May 12 and July 7 (Table 10). Carp
comprised 77% of the 1982 larval catch and attained peak
densities in late June (Figure 12). In general, larval carp
were of significantly greater density (p<0.01) in the
drop—net samples of the shallow-water bayous (Table 12).
On June 22, peak carp density was 62.51 65.8 larvae/m3 in
the shallow—water bayous as compared to densities of 1.51
0.8 and 0.491 0.08 larvae/m3 in the bayou-mouths and river
channels, respectively (Appendix A.1; Figure 12). Carp
larvae of bayou Y were particularly prolific with peak
nighttime densities of 203.01 129.8 carp/m3 (Figure 13;
Appendix A.2). Differences between channel stations were
generally not significant (p>0.10) (Table 13). However,

on June 8 the main channel carp densities were 8.0: 6.8

56

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59

Table 13. Statistical differences in nighttime larval fish
densities between north branch (N), south branch (S), and
main channel (M) stations of Pentwater Marsh as determined
by the Mann-Whitney-U test. All stations not underscored by
the same line were found to be significantly different

 

 

 

(p<0.10).
GIZZARD

Date CARP SHAD CYPRINIDS LEPOMIS
5-25-82 N_s_1~_1 M_N_S NSM EM
6-8-82 _l_i_§M NSM NSM -
6-22-82 Ms SM — -
7-7-82 gm NSM - -
7-20-82 Ms NSM - NSM

 

 

6O

larvae/m3, or over eight times greater than those of the
north and south branch stations.

On all dates, and over most stations. estimated carp
densities were greater at night (p<0.01) often exceeding day
densities by as much as ten-fold (Appendix C.1). Daytime
patterns of distribution were similar to night except the
greatest carp densities occurred in the bayou—mouths rather
than shallow-water bayous (Figure 12). Both day and night
samples showed a trend of higher carp densities in emergent
vegetation as compared to floating-leaf and submergent
vegetation (Figure 14). However, the significance of this
relationship was difficult to determine given a low sample
size (n-6) per vegetation type (Table 14). Peak 1arva1
densities occurred first in floating-leaf (85.0: 37.9
larvae/m3) and submergent vegetation (81.81 30.9 larvae/m3)
and progressed to emergents (317.1+ 260.3 larvae/m3) later
in the season (Figure 14).

Of all marsh species, carp larvae exhibited the
greatest differential in coefficients of variation between
day and night. The distribution of carp by day was the most
uniform of all marsh species, although a coefficient of
variation of 4.61 indicated a highly contagious distribution
by night (Table 15). Examination of the coefficients of
variation grouped by vegetation type indicates an increase
in heterogeneity occurred primarily in emergents by night,
whereas coefficients of variation decreased in submergent

vegetation (Table 16). Carp coefficients of variation, and

61

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§

WT

 

CARP DENSITY (Jr/m3)
9
>
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G.
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>
(n

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100

  
 
 

FLOATING-LEAF
WENT

A M J J A 3
TIME (months)

Figure 14. Day and night larval carp densities across
vegetation types in the shallow-water bayous
of the Pentwater Marsh.

62

Table 14. Statistical differences in nighttime larval fish
densities between emergent (E), floating-leaf (N), and
submergent (S) vegetation of Pentwater Marsh as determined
by the Mann-Whitney U test. All stations not underlined by
the same line were found to be significantly different
(p<0.10; one-tailed).

 

 

 

GIZZARD NORTHERN
Date CARP SHAD CYPRINIDS LEPOMIS PIKE
4-13-82 - ’ — - — _§§§
5-25-82 ._§§ - .§§E - -
6-1-82 M_E u_§ - - _§ys
6-8-82 .§!§ - .§!§ .§fl§ .§!§
6-22-82 _1§§ - ._§§ jflfli_ -
7-7-82 ‘gL§ - - _§§§ —
7-20-82 NS E 3 NS ENS -

 

 

63

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Nm.o«No.m m n . omH . HH.e - anon zuaoaoNHmH
: - 1 : on . «N.N . can. uumuuHu
mm.ouHo.m e NN.o«NN.m N as so om.N es.m unautae .n
oo.o+NN.m e No.N H Nm em Ho.N Ne.N mUHaHuNHo
No.oHNm.m e NN.HHNN.N N 9N we mm.H em.N .aam mHaoNoH
Ne.oams.m o No.oHNm.m N NH as oe.H o<.N mxHN aumnuuoz
oN.H«wo.N N oo.N H m «N mo.o oo.N notma :oHHmN
om.o«mH.m c Nm.q«mo.H q oNH NH Ho.< om.H ayou
>0 2 an I: 12 11111 Hmuaz Nan Hmqu Nd: mMHcmnm
emon N<n

 

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moz<nz=m< M<mm H< >

 

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nouns msoaum> Mom Acmma\.n.ml>uv cofiumwum> mo mudeUHmmooo unmwc was hon .na mHamB

64

Table 16. Coefficients of variation (S.D./mean) for various
larval fish species and vegetation types, as averaged across
the 1982 sample season.

 

 

 

 

 

 

 

 

SAMPLE SEASONAL ESTIMA ED
SIZE MEAN CV TorFl SAMPL

TREATMENT (# dates) (mean CV :SE) VALUES SIZE
CARPvEY NLQHT:

emergents 6 1.66 i 0.25 22

submergents 6 1.08 i 0.14 9

fl.leaf 6 1.39 i 0.24 1.81 NS 11
CARP EY DAY:

emergents 3 0.96.1 0.67 7

submergents 4 1.33.1 0.28 14

fl.leaf 3 1.35 i 0.76 0.15 NS 14
NORTHERN PIKE BY NIGHT:

emergent 6 1.97 i 0.40 31

submergent 2 1.46 i_0.75 0.63 NS 18
LEPOMIS SPP.

emergents 3 2.43 i 0.00 50

submergents 2 1.43 + 0.24 5.59 *** 16

fl.leaf 1 1.85 - 28
CXERINIDS_BX_HISEIJ

emergents 2 1.66 1 0.07 22

submergents 3 1.99 1 0.33 32

fl.leaf 3 -1.93 i 0.51 0.16 NS 30
HCIERIHIDS_EI_DA15

emergents 2 2.93 i 0.10 68

submergents 3 2.22 i 0.32 1.69 * 40

fl.leaf 1 2.84 64

 

1 *** p<0.01; ** p<0.05; * p<0.10; NS p>0.10

2 to detect at least a 50% difference

at least

90% confidence (p<0.10) (8CV

fin mean densities with
).

65

presumably heterogeneity of distribution, were observed to
increase over the sample season (Appendices D.l and D.2).

Push-nets, pull-nets, and drop—nets captured totals of
1,484 yolk-sac larvae, 1,522 post larvae and 4 juveniles.
An estimated 3,350 eggs were easily distinguished by their
large size (1.8-2.0 mm) and the substrate of collection
(submerged vegetation). Eggs were present in samples from
June and July, although peak concentrations occurred on May
25 and on June 23. Yolk-sac larvae dominated carp
collections through the end of June, but thereafter became
less common than mesolarvae and metalarvae. The range of
total lengths for major developmental stages were:
protolarvae, 5.2 to 6.4 mm ; mesolarvae, 6.4 to7.9 mm; and
metalarvae, 7.9 to 14.0 mm.

0n numerous sample dates, carp larvae were
significantly (p<0.01) smaller by day than by night
(Appendix F.1) as observed in the shallow-water bayous
(Appendix E.1). However, on June 8 carp larvae from the
bayou-mouths were significantly larger (p<0.01) by day.
Carp larvae were rarely caught by day in the channels, but
on May 25 daytime carp were significantly (p<0.05) larger
than their nighttime counterparts. Sample size was not
sufficient to elaborate on day/night patterns across the
major bayous (Appendix B.2). In general, mean larval carp
lengths were greater by night than by day in emergent and
submergent vegetation, but not in floating—leaf vegetation

(Appendix E.3).

66

Regional comparisons showed similarities in
length-frequency distributions across shallow-water bayous,
bayou-mouths, and river channel stations (Figure 15). On
May 25, there was a single pulse of yolk—sac larvae at all
stations. By the following week, two size-groups
(protolarvae and metalarvae) were distinguishable in both
drop-net and push-net bayou stations. On June 8, it was
difficult to identify older cohorts and mean larval length
was reduced (Appendix B.1). By June 22, both bayous and
channels included a wide spread of larval carp length groups
ranging from newly hatched 5.2 mm individuals to 14.0 mm
metalarvae. Mean larval lengths were significantly (p<0.01)
smaller in the channels than the bayous (Appendix B.1). But
by July 8, length-frequency and mean length was once again
similar (p>0.10) in the bayou-mouths and river channels
(Figure 15). A greater range in size was apparent in the
drop—net samples, although larval carp were on the average
smaller (p<0.01) than those of the bayou-mouths
(Appendix.F.l).

Comparisons among bayous were tenuous since all four
major bayous were rarely sampled during the same week and
lacked sufficient sample size . In general, bayous W and Z
differed little (p>0.10) in the distribution and mean length
of carp larvae (Figure 16; Appendix E.2). Bayou Y appeared
to have the greatest diversity of size classes particularly
on June 22 when both protolarvae and mesolarvae were

present.

n=75
1 .
n=156 n=102 n=93

Figure 15.

67

BAYOU BAYOU-MOUTH CHANNEL

n=36 1 n=29 I n=75

n=47 n

EEBHSIFEF

0

13851‘9

Zlfiifi)

zm>432549

n=139 l n=0 n=33
| 11:18

n=13 1r

‘1

do

I9

7‘

n=42 n30 n=8 i
h}

1 18 12 18
'I‘OTALLENG‘n-l (mu)

Comparison of nighttime larval carp length
between shallow-water bayou, bayou-mouth,
and channel stations of the Pentwater Marsh.

68

BNWUUMI EMNOUY' BAYOUZ!

111%... ”ML...
n-16 n-62 n=56
11LF'FV-tL-vwi-wb-Fm
n=114 n-40 n=97
1:1Jk4hFflhw-v
n=55 n=107

1 n=15 n=26
: 12 18 12 1

TOTAL LENGTH (mm)

ZOiFD 384H9

n=12

84NFL iflktdl

2

Figure 16. Comparison of nighttime larval carp length—

frequencies between the major bayous (W, Y,
and Z) of the Pentwater Marsh.

69

Channel samples were less diverse in size classes.
Carp larvae were rarely greater than 7.0 mm even by late
July. However, mean larval carp lengths differed
significantly (p<0.01) between the north branch, south
branch, and main channels (Appendix B.4). North branch
larvae were generally smaller than those of both the north
branch and main channel (Figure 17). There was no
significant difference (p>0.10) between the mean larval
lengths at channel side and mid stations (Appendix E.5).

Visual inspection of carp length—frequencies uncovered
no striking patterns of length distribution according to
vegetation types (Figure 18). On June 1, carp larvae were
significantly larger in emergent rather than floating—leaf
and submergent vegetation (Appendix C.2). By the following
week, however, carp larvae of emergent vegetation were
smaller than in other vegetation types. Carp length
distributions were similar in all vegetation types through

the remainder of the season (Figure 18).

Gizzard Shad

 

A total of 372 gizzard shad larvae (Dorosoma
cepedianum) were identified in the 1982 ichthyoplankton
collections of Pentwater Marsh. Gizzard shad was the second
most abundant species, occasionally surpassing larval carp
densities at specific sampling stations. However, the
frequency of gizzard shad occurrence was low, and

distribution was extremely heterogeneous as evident in high

7O

38-8-9 28-93-9

n-12

i d
CHE-9

38-2-1

   

ZQ-OZ-L

12 1s 6' 12 1
TOTALLENG‘IHM

Figure 17. Comparison of nighttime larval carp length—
frequencies between the channel stations of the
Pentwater Marsh.

71

FLOATING-LEAF WT

m
1
n=36 n=10 n=26

% WY
d
l 31

n=58 n=53

“.50 n-45 n=45

FT-

1::l n=15 n=5 n=12
I

Figure 18.

F

n=6 n=4 n-19
12 1 12 18 12 1
113Tlfl.l£3'Gfl110fllfl9

Comparison of nighttime larval carp length-
frequencies between vegetation types in the
shallow-water bayous of the Pentwater Marsh.

38-83-9 88-8-8 384-9

Z8-l-L

28-08-2

72
coefficients of variation (Table 16). Gizzard shad were
encountered from May 25 through July 20 with peak densities
occurring during the first weeks of June (Figure 19). On
June 1, the highest density of 18.2: 10.9 larvae/m was
measured in marsh bayous at night (p<0.05) (Appendix B.1).
No larval gizzard shad were captured in the shallow-water
bayous by day. On June 8, larvae were caught only in the
channels and bayou-mouths at densities of 0.2: 0.1 and
0.08:0.08 larvae/m3. The shallow-water bayous once again
had higher gizzard shad densities (p<0.01) on July 20
(Table.12; Appendix C.2). Gizzard shad were caught in
greatest numbers by night across all marsh stations. June
22 proved the only exception when daytime larvae outnumbered
(p<0.01) nighttime larvae at channel stations.

Comparisons between channel stations showed no
significant (p>0.10) difference in larval abundance
(Table.13). However, generally fewer gizzard shad were
caught in the north channel (Figure 20). Gizzard shad were
never encountered in bayous X and were collected only by day
in bayou Z and by night in bayou W. Bayou Y attained peak
nighttime larval densities estimated at 27.3: 16.0 gizzard
shad/m3 (Appendix B.2). Both day and night larval densities
were higher (p<0.10) at mid channel than side channel
(Appendix E.5). Moreover, all gizzard shad taken by
drop-net were found in floating—leaf vegetation. 0n the
night of June 1, floating-leaf larval fish density was

estimated at 54.71 29.3 larvae/m3 (Appendix B.3).

73

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74

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75

A total of 269 gizzard shad eggs were identified on May
25, June 8, and June 23, with diameters ranging from 0.9 to
1.0 mm. Peak egg densities occurred on May 25, primarily in
the main channel and drift of the marsh outlet. All 372
gizzard shad larvae were protolarvae ranging in size from
3.5 to 3.8 mm . Average larval lengths were higher in the
channels than bayous (p<0.10) (Appendix E.1) and increased
from 3.63: 0.07 mm on May 25 to 3.76: 0.03 mm on June 22.
Few gizzard shad were collected after June 22, and no
post-larval fish were identified during the remaining field

season 0

Cyprinids

A total of 162 cyprinid larvae were collected in 1982
(Table 10). Larvae were present from May 25 through August
23 with peak densities observed between May and June
(Figure 21). Two separate major peaks were recorded within
the bayous of Pentwater Marsh; the first occurred on May 25
and the second on June 8. Highest densities were measured
at night on June 8 in the shallow-water bayous at 4.71.2.2
larvae/m3 (Appendix B.1). Bayou densities declined in late
June but regained a mean density of 0.19t_0.19 larvae/m3 by
the end of July. On most sample dates larval cyprinid
densities were less in the bayou-mouths, although the
difference was not significant (p>0.10) (Table 12;
Appendix.C.3). Larval densities within the river channels

were substantially lower than densities of either bayou

76

region. On the night of June 8 there was an estimated
0.01:0.01 larvae/m3 in the channels (Appendic B.1). A late
July peak in larval density was not observed as it was in
the bayous (Figure 21).

Larval cyprinid abundance did not differ significantly
(p>0.10) between the major bayous of the marsh (Appendix
C.3). However, peak abundance occurred first on June 1 in
bayous Y and 2, followed by a peak in bayou W on June 8
(Figure 22). Bayous W and Z appeared to have higher peak
cyprinid densities than the upstream bayous. However,
cyprinid sample size was insufficient to allow demonstration
of patterns across channel stations (Table 12). Larval
cyprinids were caught in the south branch and main channel
primarily on May 25 and June 8, respectively. Neither was
there a significant difference (p>0.10) in larval densities
between the mid and side channels (Appendix B.5). Cyprinid
abundance showed no consistent or significant (p>0.10)
patterns which could be related to vegetative types
(Table.12; Appendix B.3).

Day cyprinid densities were almost always less than
nighttime values (p<0.10) (Appendix C.3). For example, on
June 8, shallow-water bayou densities were 1.11 0.5 larvae/m3
by day as opposed to 4.71_2.2 larvae/m3, by night (Appendix
B.1). Daytime densities in the bayou-mouths were somewhat
higher at 2.31 1.4 larvae/m3 although the difference was not
significant (p>0.10)( Appendix C.3). Coefficients of

variation indicated cyprinids were more heterogeneous by day

77

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78

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79
than by night (Table 15), particularly in emergent
vegetation (Table 16). Larval cyprinid distributions
increased in heterogeneity over the sample season
(Appendices D.l and D.2).

Cyprinid larvae were not easily identified and thus
were treated as a complex of several genera and species.
Identification was complicated by extended spawning periods
and overlaps in species abundance within the marsh.
However, I could identify about 90% of the larval cyprinids
as either golden shiners (Notemigonus crysoleucas) or

bluntnose minnows (Pimephales notatus) (Table 10). Cyprinid

 

eggs and protolarvae were collected from May 10 through July
20. Eggs were typically 1.3 to 1.5 mm in diameter while
protolarvae ranged from 4.8 to 6.6 mm depending on age and
species. Mesolarvae and metalarvae were present May 25
through June 23. Most mesolarvae were between 7.0 and 10.0
mm while all metalarvae were greater than 9.0 mm in length.
Cyprinid length—frequency illustrates the influx of young,
newly hatched, protolarvae on May 25, June 8, and July 20
(Figure 23). On May 25, there were significant differences
(p<0.01) between day and night mean larval lengths of the
marsh bayous. Larval length was greater (p<0.01) in the
shallow-water bayous by night and greater (p<0.01) in the
bayou-mouths by day. Average cyprinid length was
significantly greater (p<0.01) in emergents by day but was
greater (p<0.01) in submergents by night (Appendix E.3;

Appendix F.2).

80

BAYOU BAYOU-MOUTH CHANNEL

n=6

38-93-9

 

38-8-9

 

38-33-9

E 1.
a? .
1.] n=2
1
n=2 n=2
:Eljgg'T'W'fi"F'1'fiilJL;'T'¥'H§H"FH
12 18 1 18

TOTAL LENGTH (mm)

38-2-2

I n=20
1
n=2] 1 n=12
l n=2

38-03-L

Figure 23. Comparison of nighttime larval cyprinid length—
frequencies between shallow-water bayou, bayou—
mouth, and channel stations of the Pentwater
Marsh.

81

Pumpkinseed Sunfish

Of the total larval catch, 87 individuals ( 2%) were
identified as of the Lepomis genus (Table 10). Since adult
pumpkinseed sunfish (Lepomis gibbosus) were abundant

throughout the marsh, whereas bluegills (L. macrochirus)

 

were rarely captured, the majority of specimens were assumed
to be pumpkinseed sunfish. These larvae were found in the
marsh from May 25 through August 23 with peak densities
occurring in early June (Figure 24). The highest Lepomis
spp. density of 7.4: 3.4 larvae/m3 was encountered in the
upper bayous on the night of June 8 (Appendix B.1). A
significantly lower (p<0.01) density of 0.9: 0.6 larvae/m3
was measured in the bayou-mouths on the same date (Table 12;
Appendix C.4). By June 22, bayou densities had dropped
below 1 larvae/m3 and remained at similar levels through
July.

Lepomis spp. larvae were encountered earlier in the
channels with low nighttime densities of 0.02: 0.01 larvae/m3
on May 25 (Figure 21; Appendix B.1). Channel larvae were
not captured again until mid—July when densities reached
0.08: 0.04 larvae/m3. Apparently, the earlier peak occurred
in the south branch while later-in—the-season larvae were
largely confined to the north branch and main channels
(Appendix B.4). Peak bayou densities were highest in bayous
W and Z, although differences were not significant (p>0.10)
(Appendix C.4). Patterns of distribution were not clearly

associated with vegetation type. Pumpkinseed sunfish were

82

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83

present in sufficient numbers to allow statistical analysis
only on June 8. At that time, nighttime densities of 1.71
1.7, 2.51 1.9, and 18.61 9.9 larvae/m3 were measured in
emergents, floating-leaf, and submergent vegetation,
respectively (Appendix B.3). However, a Mann-Whitney—U
comparison showed no significant differences (p>0.10) in
densities among vegetation types (Table 14; Appendix C.4).
Larval Lepomis spp. were significantly (p<0.01) more
heterogeneous within the emergent vegetation and of more
uniform distributions in submergent and floating—leaf areas
(Table 16).

Daytime distributions exhibited the greatest
heterogeneity (Table 15). By day, larval Lepomis spp.
densities were significantly (p<0.10) lower than by night
in bayous, channel sides, north branch and main channels
(Appendix C.4). Highest daytime densities occurred on June
22 and in the shallow—water bayous at densities of 1.31 1.0
larvae/m3. Most larvae were captured in bayou W at an
estimated density of S-Oi.5-2 larvae/m3 (Figure 25).

Approximately 700 eggs believed to be of Lepomis spp.
were collected from June 8 through June 23 . Eggs were
typically 1.1 to 1.3 mm in diameter and were principally
collected in the shallow-water bayous. Highest egg
densities were associated with the high densities of
protolarvae in bayou W on June 23. Protolarval Lepomis spp.
were caught from May 25 through July 20, although mesolarvae

were in greater abundance after June. Protolarvae were from

84

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85

4.7 to 5.8 mm in total length while mesolarvae ranged from
5.6 to 10.2 mm. Only a few metalarvae (10.6 to 12.2 mm) and
three juvenile pumpkinseed sunfish ( > 30 mm)) were
collected in July. No significant (p>0.10) patterns of size
distribution were apparent across stations or vegetation

types (Appendix E; Appendix F.2)..

Yellow Perch

 

A total of 72 larval yellow perch (Perca flavescens)
were captured in Pentwater Marsh during 1982. The majority
were obtained from sample dates in May, although some yellow
perch were present in samples taken on June 22 (Figure 26).
A peak density of 6.5: 2.2 larvae/m3 was measured at night
on May 12 in the shallow-water bayous (Appendix B.1).
Highest (p<0.10) densities occurred in bayou X at 5.6: 2.2
larvae/m3 by night (Appendix 3.2; Figure 27). Channel
densities were generally lower than bayou values with a May
25 peak of 0.18: 0.10 larvae/m3 (Appendix C.4; Figure 27).
Nighttime densities at channel sides (0.29:0.18 larvae/m3)
were not significantly (p>0.10) higher than densities at mid
channels (0.07: 0.02 larvae/m3) (Appendices B.5 and C.4).

No larvae were collected in the main channel and north
branch by night, although yellow perch were measured at
reduced densities (<0.1/m ) by day (Appendix B.4). Daytime
abundance followed patterns similar to night, but of
significantly lower densities (p<0.10) in bayous, and

somewhat lower densities in channels (Appendix C.4). Yellow

86

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88

perch larvae were much more uniform in distribution by night
with a coefficient of variation of 0.98 compared to 2.06 by
day (Table 15). No larvae were collected in floating-leaf
vegetation by either day or night. Larval yellow perch were
primarily collected in emergent vegetation with estimated
peak nighttime densities of 12.11 3.6 in emergent and
4.713.1 larvae/m3 in submergent vegetation (Appendix B.3).
Several yellow perch eggs were identified from May 10
channel samples with diameters between 1.0 and 1.2 mm. On
this date, yellow perch were spawning across the submerged
vegetation of bayou W. Only protolarvae (4.8-5.8 mm) were
collected on May 25, although by June 1, a number of
mesolarvae (5.4-10.2 mm) and metalarvae (10.6-12.2 mm ) were
also identified. Only one juvenile of 19.9 mm was collected
in August. Mean daytime larval lengths were significantly
(p<0.01) smaller in bayous than in the channels (Appendix
F.2). On May 25, mean larval length in the channels was
significantly (p<0.10) greater by night than by day

(Appendix E.l).

Northern Pike

 

Only 31 larval northern pike (Esox lucius) were
collected in 1982 (Table 10). All larvae were found in the
.shallow—water bayous and the majority were captured on April
13 and May 12. Highest (p<0.01) larval densities occurred
at night, particularly in the shallow-water bayous (Appendix

B.1). On the night of April 13, an estimated 2.5i_1.3

89

larvae/m3 were present in the marsh bayous (Appendix B.1).
Peak densities of 10.01 0.7 larvae/m3 and 1.81 1.1 larvae/m3
were measured in bayous Y and X (Appendix B.2). Daytime
collections contained northern pike only on May 12. On this
date, bayou W had an estimated 2.1i 1.7 larvae/m3 which was
not significantly different from values of the other bayous.
Northern pike distribution was more contagious by day than
by night (Table 15), although there was no significant
difference (p>0.10) in heterogeneity across vegetative
habitats (Table 16). On most dates, larval densities were
greater (p<0.10) in emergent than submergent vegetation
(Appendix F.2; Table 14). From May to June, northern pike
were found exclusively in emergent vegetation. Northern
pike larvae were never caught in floating-leaf vegetation
(Appendix B.3).

Only a few viable eggs were collected in bayou drop
samples. Identifiable northern pike eggs were approximately
2.4 mm in diameter. On April 13, numerous egg membranes
were observed in the shallows of bayou Y on April 13.
Protolarvae were also collected on April 13 as well as
May 10. Protolarvae ranged from 8.0 to 10.2 mm. Mesolarvae
of total lengths 10.8 to 13.4 mm were also taken on these
dates. Only one northern pike collected on May 10 was
classified as metalarval (15.0 mm TL). Five juvenile
northern pike were collected from June 7 through July 21
ranging in size from 45.2 to 99.5 mm TL. Length-frequency

tinalysis was only possible during the peak abundance of

90

April 13. On this date, northern pike lengths were greater
(p<0.05) in emergent (8.8:0.4 mm) than submergent vegetation

(6.7+0.7 mm). (Appendix E.3; Appendix F.2)

Black Crappie

 

A total of 48 black crappie (Pomoxis nigromaculatus)

 

 

were identified in the 1982 ichthyoplankton collections
(Table 10). Black crappie larvae were collected only in May
and primarily at night. Peak densities of 0.59: 0.54 and
0.28: 0.20 larvae/m3 occurred on the night of May 12 in the
shallow-water bayous of X and Z (Appendix B.2). On the
night of May 25, highest densities of 0.78: 0.47 larvae/m3
were captured in push—nets of the bayou-mouths (Appendix
B.1). Channel station densities were measured at 0.141 0.10
and 0.0241 0.017 larvae/m3 on May 12 and May 25,
respectively. Although black crappie were found in all
channel regions, highest densities occurred at the main
channel station. Black crappie larvae were collected on May
12 in the side channel samples, but on May 25, were only
found at lower density in the mid channel stations (Appendix
B.5). By day, black crappie larvae were not collected in
the channel or bayou-mouths and were only present in bayou W
at a density of 0.0610.06 larvae/m3 on May 25.

Protolarvae were present on both May sample dates with
total lengths ranging from 4.9 to 6.2 mm. Mesolarvae were
in greater abundance on May 25 and ranged in size from 7.2

to 8.3 mm in total length. No black crappie eggs were

91

identified. Small sample size was insufficient for

completion of length-frequency analysis.

Johnny Darter

A total of 37 johnny darter (Etheostgma nigrum) larvae
were collected in the marsh from May 12 to June 22
(Table 10). On May 25, a peak density of 1.21:0.06
larvae/m3 was recorded at night in the shallow-water bayous
(Appendix B.1). Significantly lower (p<0.10) peak densities
of 0.541 0.34 and 0.24; 0.11 larvae/m3 were measured in the
channels and bayou-mouths on May 25 and June 1, respectively
(Appendix C.4). Nighttime larval abundance was greater
(p<0.01) at channel sides than at mid channels
(Appendix B.5). Although main channel peak densities were
higher than either south branch or north branch densities,
the differences were not significant (p>0.10) (Appendix
B.4). Likewise, there was no significant difference
(p>0.10) in nighttime larval densities between the major
marsh bayous (Appendix B.2). In the daytime, johnny darters
were present only in the shallow—water of bayou X and were
not found in the channels or bayou-mouths. Both night and
day larval densities were greater (but not significantly;
p>0.10) in emergent rather than submergent vegetation
(Appendix B.3). Johnny darter larvae were present in

floating-leaf vegetation samples only on June 1.

92

Johnny darter eggs were not positively identified; Eggs
suspected to be from johnny darters were collected in the
north branch of the Pentwater River in early May.
Protolarvae were collected from May 13 through June 23 with
total lengths ranging from 4.6 to 5.6 mm. Mesolarvae were
present in samples from May 12 through May 25, and attained
total lengths of 8.9 mm. No juvenile johnny darters were
captured in drop-nets, push-nets, or trap-nets during 1982

sampling (Tables 8 and 9).

Alewife

A total of 57 larval alewife (Alosa pseudoharengus)

 

were identified, 46 of which were caught in drift, lake, or
outlet samples, and not in the marsh proper (Table 10).

Over 700 alewife eggs were tentatively identified from June
23 and July 7 Pentwater Marsh, Pentwater Lake, and drift
collections. Alewife larvae were encountered in marsh drift
only on June 10 when an estimated 20,000 protolarvae were
transported from lake to marsh. On June 23, no alewife eggs
or larvae were caught in marsh samples or in drift at the
marsh outlet. However, an estimated 3.1: 2.0 and 1.81 1.1
alewife eggs/m3 were found in day and night collections from
the Pentwater Lake. On June 30, although alewife were not
present in nighttime drift from the marsh, oblique
stationary tows at the harbor outlet caught over 400 alewife
eggs by day and 50 eggs by night. At this time, alewife

larvae from 4.1 to 5.7 mm in length were caught in night

93
lake samples at densities of 0°29i.0-20 larvae/m3. Lake
densities increased by July 20 to a nighttime density of
1.5¥ 0.7 and daytime density of 0.34: 0.12 larvae/m3. These
predominantly mesolarval and metalarval alewife ranged from
7.3 to 17.2 mm in total length. On the same date, alewife
eggs were found in the marsh main channel at a density of
0.06: 0.03 larvae/m3 by night. By August 23, only a few
mesolarval alewife were collected in densities of 0.05 i
0.04 larvae/m3 in the main channel of the Pentwater Marsh

(Appendix B.4).

.Brook Silversides

All 35 brook silverside larvae (Labidesthes sicculus)
were collected at night (Table 10). No larvae were found in
the shallow-water bayous and most larval brook silversides
were collected in the bayou mouths (Appendix B.1). Brook
silversides were found in bayou X on June 8, and in bayou Z
on July 20, at densities of 0.711 0.50 and 0.941 0.22
larvae/m3, respectively (Appendix B.2). Larvae were present
in channel samples from June 8 through July 20 with peak
larval density of O.71+ 0.64 larvae/m3 on July 7. There was
no significant difference (p>0.10) between densities at mid
and side channels although side densities appeared somewhat
higher (Appendix C.4; Appendix B.5). Larvae were collected
in the south branch and main channel samples, but were never
found in the north branch (Appendix B.4). Protolarvae and

mesolarvae from 5.1 to 10.3 mm in length predominated in

94
June through early July. Metalarval brook silversides

between 10.2 and 24.8 mm were collected in July.

Other Species

 

The catch of other, less abundant, larval species
included 26 bowfin (Amia calva), 20 white suckers

(Catostomus commersoni), 11 largemouth bass (Micropterus

 

salmoides), 9 brown bullheads (Ictalurus nebulosus), 2

sculpins (Cottus bairdi), 1 brook stickleback (Culea

 

inconstans), 1 trout perch (Percopsis omiscomaycus), and 1

 

banded killifish (Fundulus diaphanus) (Table 10). Bowfin
were collected only three times during the season but one
sample included a school of larvae. On May 25, twenty-five
bowfin of 13.0 mm mean total length were sampled in bayou W
emergent vegetation. At this time, field researchers
reported a number of adult males guarding young in water
less than 20 cm deep and in Open patches in the emergent
plants. Bowfin larvae were also collected in emergents by
day on June 1 and June 22 in bayou Y. White sucker larvae
were not collected until May 12 although eggs were
identified as early as April 22 (Appendix B.1). On May 12,
several 9.0 to 11.0 mm white sucker larvae were found at the
sides of the south channel by day and in bayou X by night
(Appendices B.5 and B.2). A 14.4 mm larval white sucker was

collected in bayou Y on the night of June 1. Largemouth

95

bass were collected from June 8 through August 3.
Largemouth bass larvae were observed in greatest abundance
(1.6iO.7 larvae/m3) in bayou Z on July 7, although larvae
were also collected in bayou X and the main channel
(Appendix B.2). Brown bullheads were collected in bayous X
and Y by night and day on July 7 and July 20. Like bowfin,
bullhead young were distributed unevenly in nest
congregations. Bowfin and brown bullheads had the highest
coefficients of variation of the marsh larval species at
5.11 and 4.12, respectively (Table 15). Seven metalarval
sculpins, between 7.2 and 9.8 mm in length, were collected
in the channel samples on the night of May 25. The single
metalarval brook stickleback was 10.8 mm in length and was
collected in the bayou-mouth of Z on the night of May 25.
(Appendices B.1 and B.2). Only one trout perch of 7.2 mm
was identified from push-net samples in the mouth of bayou W

on May 12.

Cgmmgnity Patterns

A total of 18 fish taxa were identified as marsh
inhabitants during the larval stages. From May through
July, the calculated Shannon-Weaver diversity index
fluctuated from 0 to 2.67 (Appendix 0.1). Diversity values
varied greatly between sample dates, often by as much as one
diversity unit. Clear seasonal trends were not readily
apparent. On any given date, diversity was usually greater

by night than by day, although Wilcoxon-Signed-rank tests

96

showed no significant difference (p>0.10). Marsh-wide
seasonally pooled diversity values of 1.08 and 0.76 were
obtained for night and day sampling, respectively. Species
richness (D) and species evenness (J) reflected diversity
values and likewise seasonal trends were difficult to
establish. Species richness ranged from 0.70 to 1.40, while
species evenness fluctuated between 0.20 and 1.0
(Appendix.C.Z; Appendix C.3).

Graphical comparisons of diversity across regions
suggests that while the bayous exhibited a minimal diversity
in early June, the channels supported high diversities of
larval fishes (Figure 28). Examination of species richness
shows a similar pattern with maximum and minimum species
numbers occurring in channels and bayous, respectively.
Comparisons across bayou vegetation types showed a clear
pattern of decreasing diversity from May through July in
emergents and submergents but not in floating-leaf
vegetation (Figure 29). Larval fish diversity associated
with floating-leaf vegetation peaked in late July at a much
higher value. Both species richness and evenness followed
similar patterns across dates and vegetation types. The low
larval fish catch of channels prevented as detailed an
analysis of diversity. There was a slight increase in
diversity over time in the main channel with a concomitant
decrease in diversity in the shallow-water bayous

(Figure.28). North and south branch species richness

97

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99

declined in late May through June while species richness was
observed to increase in the main channel (Appendix 0.2).

The Shannon-Weaver index was also calculated for
individual samples of the marsh. As expected, sample
diversity was smaller than that of pooled data and with less
variation across dates (Appendix H). Diversity was greater
for push-net samples than drop-net samples, particularly at
peak diversity measurements in early June. Bayou-mouth
push-net diversity was intermediate between the values for
channel push-nets and bayou drop-nets. But differences in
diversity were also apparent between stations of similar
sampling gear and effort. Comparisons across bayou
vegetation stations showed a definite pattern in diversity
not dissimilar to that of pooled community data. Emergent
sample diversity peaked early in May and then declined in
June as diversity increased in submergent and floating-leaf
vegetation .

Species associations were measured only during peak
abundance of the major larval species (Tables 17 and 18).
Forbes coefficients of association (Cole 1949) ranged from
-O.32 for johnny darters and Lepomis spp., to 0.69 between
Lepomis spp. and cyprinids indicating disassociation and
association, respectively. Carp and Lepomis spp. were the
only other case of species disassociation, with negative
coefficients by both day and night. Besides pumpkinseed
sunfish, cyprinids were associated with yellow perch and

carp by night, and with northern pike and carp by day.

100

Table 17. Nighttime associations among larval fish species
of the Pentwater Marsh, as measured by Forbe's coefficient
(cf). Cf values of 0 indicate chance association, whereas
values of 1 and -1 indicate complete association and
disassociation, respectively.

 

 

YELLOW NORTHERN JOHNNY BLACK

 

SPECIES CYPRINID LEPOMIS PERCH PIKE DARTER CRAPPIE
carp 0.38 -0.23 0.01 0.04 0.13 -
cyprinids 0.69 0.43 0.10 -0.03 -
Lepomis spp. 0.10 0.46 —
yellow perch 0.37 0.20 0.20
northern pike 0.13 -
johhny darter 0.13

 

 

Table 18. Daytime associations among larval fish species of
the Pentwater Marsh, as measured by Forbe's coefficient
(cf). Cf values of 0 indicate chance association whereas
values of 1 and -1 indicate complete association and
disassociation, respectively.

 

 

YELLOW NORTHERN JOHNNY BLACK—

 

SPECIES CYPRINID LEPOMIS PERCH PIKE DARTER CRAPPIE
carp 0.36 —0.19 0.43 — -

cyprinids - - 0.37 —
Mew. - - -O.32

yellow perch 0.10 0.38

northern pike 0.37

 

 

101
Yellow perch were associated with carp and johnny darters by

day, and cyprinids and northern pike by night.

Standing Crop Estimates

Standing crop estimates were derived from larval
densities stratified and weighted by the areas of vegetation
types (Appendix I). For example, peak densities of
3,017,000 carp, 299,000 cyprinids, 222,000 yellow perch,
54,000 northern pike, and 19,000 pumpkinseed sunfish were
estimated per hectare of shallow-water bayou habitat
(Table.19). Given the total bayou area of 25 HA, the
Pentwater Marsh supported an estimated 75 million carp, 7
million cyprinids, 5 million yellow perch, 1.4 million
northern pike, and 0.5 million pumpkinseed sunfish. Of
course, these estimates do not include the channels where
densities were best expressed volumetrically rather than by
area. Considering the exclusion of channel areas and other
upstream riparian habitats , the marsh as a whole likely
supports much higher populations than indicated. Error
bounds were approximately 502 of the standing crop values
based on the variability and error in estimates of both

vegetation area and larval densities.

Larval Fish Drift

 

Minimal drift sampling and the associated sampling
errors precluded a detailed analysis of larval drift. Also,

seiche activity complicated measurements of the water volume

Table 19.

during 1982.

102

Standing crop (#lHA wetland) of major larval fish
species as encountered in the bayous of Pentwater Marsh

Standard errors, although not included for

each figure, represent approximately 501 of the mean.

 

 

 

NORTHERN YELLOW
Date CARP CYPRINID PIKE LEPOMIS PERCH
4-13-82 - - 54,000 - -
5-12-82 - - 16,000 - 222,000
5-25-82 354,000 124,000 4,000 - -
6-1-82 712,000 - 3,000 - -
6-8-82 3,000,000 299,000 17,000 19,000 -
6-22-82 3,017,000 10,000 4,000 4,000 -
7-7-82 175,000 - - 4,000 -
7-20-82 445,000 2,000 - 5,000 -
8-3-82 - 4,000 - - -

 

 

103
and the direction of flow. However, it was clear that
larval drift occurred with some regularity, particularly at
night (Appendix J). Carp larvae and clupeid eggs dominated
the catch throughout the season. On numerous occasions, the
net flow of eggs and larvae was actually into, rather than
out of the marsh, presumably due to seiche transport. This
phenomena was observed on May 25, when an estimated 29
million clupeid eggs may have entered the marsh over 24
hours (Table 20). On July 8, an estimated drift of over 2
million larval carp occurred unidirectionally from lake to
marsh. But on June 28, an estimated net 646,000 carp
larvae drifted from marsh into lake. Cyprinids were
captured exiting the marsh on May 25. Both pumpkinseed
sunfish and clupeids were exported on June 10. Small eggs
(0.9-1.1 mm) drifting into the marsh in May were believed to
be primarily gizzard shad, whereas eggs drifting (1.0-1.1
mm) from the marsh in July were likely of alewife origin

based on the observed abundance of adult spawners (Table 8).

Larval Fish Abundance in AdjoiningfiHabitats

Alewife, pumpkinseed sunfish, and brook silversides
were the primary species captured in push-net samples within
Pentwater Lake (Table 21). In late June, pumpkinseed
sunfish were measured at densities of 0.521_O.31 larvae/m3
which declined to 0.15:_O.13 larvae/m3 by late July. Carp

and other cyprinids were present at June densities of

0.10:0.09 and 0.231’0.14/m3, respectively. Cyprinid

104

Table 20. Estimates of larval fish drift (#lday) at the
Pentwater Marsh outlet on selected sample dates of 1982.
Positive values represent net daily numerical drift from the
marsh to Pentwater Lake, whereas negative values indicate a
net daily flux of larvae into the marsh due to seiche
activity.

 

 

 

Date CARP CYPRINIDS LEPOMIS ALEWIFE EGGS
5-25-82 -310,600 44,400 29,368,800
6-10-82 402,400 -l9,900 -20,000 -489,000

6-23-82 645,900
7-8-82 -2,067,700 178,200
7-20-82 22,000

 

 

105

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106
densities dwindled to 0.041 0.03 larvae/m3 by late July.
Alewife and brook silversides were only observed in July
collections at densities of 1.521 0.62 and 0.471 0.24
larvae/m3, respectively. June 30 oblique tows taken at the
outlet to Lake Michigan, collected only larval alewife in

low densities of 0.033 larvae/m3 at night.

Environmental Parameters and Larval Abundance

Six physical/chemical parameters were significantly
correlated (p<0.10) with total larval fish abundance
(Table.22; Appendix K.1). Time of sampling (r-0.17;
p<0.01), turbidity (r-0.18; p<0.01), and submergent cover
(r-O.19; p<0.01) were all positively correlated with larval
fish densities. There was a negative relationship between
larval density and radiant light (r--0.31; p<0.01),
dissolved oxygen (r--0.16; p<0.05), and percent
floating-leaf cover (r--0.19; p<0.01).

Larval carp density was positively correlated with
temperature (r-0.60; p<0.01) , the time of sampling (r-0.30;
p<0.05), and submergent cover (r-O.22; p<0.10) (Table 22).
Carp densities were negatively correlated with dissolved
oxygen (r--0.22; p<0.10), radiant light (r--O.48;p<0.01),
and depth of sample (r--O.22; p<0.10) (Appendix K.2).
Turbidity was not significantly (p>0.10) related to carp
abundance, but was somewhat associated with the abundance of
other cyprinids (r-O.19; p<0.10) (Appendix K.3). Cyprinids

were not highly correlated with any particular factor,

107

 

 

 

 

 

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108

although temperature was negatively related to cyprinid
abundance with a correlation coefficient of -0.24 (p<0.10).
Larval Lepomis spp. were associated with habitats of dense
submergent cover (r--O.28; p<0.05) but were negatively
correlated with floating-leaf vegetation (r-—O.28; p<0.05)
(Appendix K.4). Yellow perch were strongly associated with
the incongruous parameters of emergent vegetation (r-O.66;
p<0.01) and deep water (r-0.54; p<0.01)( Appendix K.S).
Although emergent vegetation was negatively related to water
depths in the overall sample (Table 4; Appendix K.1), depth
and emergent vegetation were not significantly (p>0.10)
intercorrelated in the yellow perch subsample
(Appendix.L.5). Yellow perch were also related to the time
of sampling (r-0.26; p<0.01) and higher water turbidities
(r-O.27; p<0.10). Northern pike larvae were positively
correlated with dissolved oxygen (r-O.35; p<0.05) ,
turbidity (r-0.35; p<0.05,) and emergent cover (r-0.29;
p<0.10). There was a low but insignificant (p>0.10)
correlation of northern pike with habitats of sparse

floating-leaf vegetation (Appendix K.1).

DISCUSSION

Gear Evaluation

Several authors (Kjelson et al. 1975; Kjelson 1977;
Miller and Guillory 1980; Kushlan 1981; Cole and MacMillan
1984) have cited the difficulty of sampling in shallow
littoral habitats like Pentwater Marsh. When such
investigations have been completed, researchers have rarely
critically analyzed gear performance or evaluated the
reliability of estimates (Craig 1980). The low species
abundance and highly contagious distributions of larval fish
populations further complicates analysis often discouraging
rigorous statistical applications. Qualitative marsh
studies no longer meet the needs or the urgency of the Great
Lakes wetland situation. Wetland and fisheries regulatory
agencies require immediate, quantitative information to
carry out duties as educated managers of a complex and
waning resource.

Push-nets as deployed in open-water channels and
deep-water bayous were assumed to approach or surpass 80%
efficiency (Thayer et al. 1974; Barkley 1964). But
push-nets may also bias results by selecting for smaller and
younger individuals, or species less able to avoid the net

(Cole and MacMillan 1984; Alhstrom et a1 1973). In

109

110

particular, reduced net efficiencies and increased species
bias by day may result in underestimates of larval densities
and inaccurate descriptions of species composition.

Drop-net sampling was presumably subject to similar
biases and inefficiencies. Larval fish avoidance was
possible during both initial drop-net deployment and
subsequent sample retrieval with dip-net. Since larval and
juvenile fishes reportedly respond to disturbance with a
downward rather than horizontal movement (Hunter and Wisby
1964) initial net avoidance may be less crucial for drop-net
as compared to push-net sampling. However, this escape
behavior is species specific, and also may introduce bias
towards the capture of certain species and developmental
stages.

Although I could not directly assess initial net
avoidance, I did evaluate dip-net removal efficiencies.
Species behavior did not lead to differential retrieval
efficiencies for protolarval, mesolarval, and metalarval
stages. Juvenile fish, however, had species specific
efficiencies ranging from 371 112 to 811 6% (Table 6).
Low larval and juvenile catches of brown bullheads, johnny
darters, and mottled sculpins may partially reflect diving
behavior during net drop and dipping procedures. Schooling
juvenile carp may also prove illusive for dip-net retrieval
with their habits of hugging the substrate during
disturbance (Hunter and Wisby 1964). And indeed, Pentwater

Marsh carp were rarely captured after attaining 20 mm in

111

length (Appendix B.1). Kjelson (1977) while working on
juvenile fish in the Forida everglades, concluded that
drop-net devices are most appropriate for demersal fish
species. In Pentwater Marsh, however, drop-nets may
underestimate demersal fish densities perhaps due to the
soft, easily suspended detrital substrates .

Species bias was also introduced due to differences in
distributional patterns between species and across day and
night. As Kjelson et al. (1975) suggested, gear of small
sample size such as the 1 m drop-net is of limited utility
for fish of lesser abundance or extremely clumped
distributions. In general, most species of larval fish
exhibited far greater heterogeneity by day than by night
as reflected in higher coefficients of variation (Table 15).
Consequently, fewer samples and replicates were required by
night to achieve desired levels of confidence. Confidence
levels were greater for some species as reflected in
coefficients of variation ranging from 0.98 to 5.11.
Northern pike, Lepomis spp., and cyprinids were particularly
well suited to the drop-net techniques because of their
relatively even distribution within sample areas of the
marsh. However, for species such as carp and yellow perch,
which exhibit great heterogeneity, confidence levels were
relatively low. Species with extremely clumped
distributions, such as largemouth bass, bullheads, and

bowfin, should be only cautiously considered for

112

quantitative estimates unless drop-net sample size can be
greatly expanded.

Kjelson et al. (1975) also noted differences in species
vulnerability when using a stationary drop-trap in the
Florida Everglades. Drop-net coefficients of variation
ranged from 0.95 to 1.98. Kjelson et al. (1975) had lower
coefficients of variation than those of Pentwater Marsh
perhaps due to a more limited sample area, emphasis on
post-larval stages, or possible attraction of fish to the
trigger platform (Kjelson and Johnson 1973). The Pentwater
Marsh larval fish coefficient of variation decreased to 1.43
when drops-nets were taken within a contiguous 100 m3 area.

A number of other authors (Liston et al. 1981b; Kjelson and
Johnson 1973; Kushlan 1981) have cited the high variability
both between neighboring replicates and stations of the same
habitat. Such variability seems to be an integral part of
the wetland community.

Certainly, the drop-net cannot be expected to compete
with far-ranging trawls or seines which offer coefficients
of variation less than 1.50 (Kjelson 1977; Weinstein 1979).
However, with estimated catch efficiencies of 73% (Kushlan
1981) and dip-net removal efficiencies of 852 (Liston and
Chubb 1983) to 992 (Kushlan 1974), the drop-net proves a
most pleasing alternative for shallow water areas of dense
vegetation . By night, mean coefficients of variation were
significantly greater (p<0.01) for bayou drop-nets than for

bayou push-nets (Table 11). However, daytime push-nets had

113

much greater (p<0.10) variance than concurrent drop-net
samples. Other factors such as temporal and spatial larval
fish distributions may thus deserve greater attention than
differences in gear efficiencies. Larval fish abundance
between channel and bayous generally differs by several
orders of magnitude (Appendix 8.1) and differences are
unlikely to be entirely due to variations in gear
capabilities. Moreover, comparisons of bayou-mouth and
river channels avoids the potential problems of differing
gears and yet Often supports similar conclusions.

While comparisons between the channels and bayous are
feasible, comparisons across bayou stations should proceed
with caution. Drop-net efficiency was significantly reduced
in shallow water less than 30 cm in depth (Table 6).
However, sample depths were rarely less than 30 cm and a
marsh-wide correction of larval estimates may not be
necessary. Comparisons across marsh stations may be
complicated by differing sample depths, particulary early in
the season. For this analysis, bayou stations (3 per bayou)
were always pooled by vegetative type or bayous. The major
bayous of the marsh do not differ significantly in average
sample depth and thus can be directly compared without
considering depth relations. Pooling samples by vegetation,
however, may require additional qualifications of estimates.
Emergent vegetation was associated with shallower water,
while floating-leaf vegetation was positively correlated

with water depths (Table 4). Submergent plant beds were

114

more ubiquitous, growing at all depths. Floating-leaf and
submergent vegetation samples were usually taken at depths
greater than 30 cm. Emergent vegetation samples were taken
at significantly (p<0.10) shallower depths. On April 13,
June 1, and June 22, emergent vegetation samples averaged
less than 30 cm in depth (Appendix A.3). Larval fish
densities of the emergent beds may thus be underestimated in
this analysis. Further work on gear efficiencies is needed
before application of an actual correction factor is
possible.

Although vegetation was correlated (p<0.01) with water
depths (Table 5), vegetation type was not shown to be a
significant (p>0.10) factor influencing gear retrieval
(Table 6). Barnett (1973) has suggested escapement of
juvenile and adult forage fish may be negligible if plant
density is high enough to limit lateral movement. The
capture of highly mobile adult fish, suggests the weaker,
less developed, larval fishes may have difficulty in
avoiding the gear. Drop-nets were rarely used in open water
areas and there was insufficient evidence that a correction

factor was needed.

Total Larval Fish Abundance

 

Pentwater Marsh estimates are most likely conservative
approximations of actual larval abundance. And yet, peak
larval fish densities of 63.5i 90.7 and 28.41 7.6 larvae/m3

in the shallow-water and bayou-mouths (Appendix B.1) are

115

higher than most comparable values observed in the
literature. For example, Copeland et al. (1979) estimated
peak larval abundance of 7.5 larvae/m3 in the tidal creeks
of the Cape Fear Estuary of North Carolina. Higher density
estimates between 10 and 15 fish/m3 have been observed in
marine estuaries (Pearcy and Richards 1962) but often
included postlarval and forage fish densities in their
totals (Weinstein 1979; Kushlan 1981). Unfortunately, few
quantitative studies are presently available for comparisons
among the freshwater coastal wetlands. According to Jude
et al. (1980), peak densities between 6 and 57 larvae/m3
occurred among various littoral stations of Pigeon Lake, a
coastal wetland 100 km to the south of Pentwater Marsh. The
St. Mary's River, located between Lake Superior and Lake
Huron, is a much larger and more riverine habitat considered
of upmost importance as a fish spawning and nursery area
(Liston et al. 1981b). Peak larval densities were measured
at 3.2 larvae/m? in the densely vegetated littoral zones
bordering the St. Mary's River. Apparently, Pentwater Marsh
compares favorably to other freshwater estuarine systems,
and with further study, freshwater estuaries may be shown to
achieve higher peak larval densities than their marine
counterparts.

Pelagic larval fish densities are generally much lower
than those of littoral habitats. Open-water riverine and
lacustrine systems rarely attain peak larval densities over

1.0 larvae/m3 (Hess and Winger 1976; Krause and Van DenAvyle

116

1979; Keast 1980). A relatively high peak density of
3-53i1-52 larvae/m3 was measured in the channels of
Pentwater Marsh (Appendix B.1). Comparable values have been
recorded in the lower channels and bays of marine estuaries
(Pendleton and Copeland 1979). Marine estuarine systems
appear to rely to a greater extent on the lower marsh (Nixon
and Oviatt 1973), perhaps as "staging areas" prior to larval
and juvenile dispersal to sea. Comparisons between
Pentwater Marsh, Pentwater Lake, and Lake Michigan
illustrates the concentration of spawning and nursery
activity largely within the littoral shallow-water regions
of the upper marsh. Peak densities of larval fish were
similar between marsh channels and Pentwater Lake but
differed by an order of magnitude between the shallow-water
bayous and lake habitat (Table 21). Previous studies
conducted on nearshore Lake Michigan show total larval fish
densities rarely exceeded 1.0 larvae/m3 and were less than
Pentwater Marsh by several orders of magnitude (Wells 1973;

O'Gorman 1975; Liston et al. 1981a).

Monthly Occurrence and Diversity

 

Total larval fish density peaked twice in Pentwater
Marsh, first in late May and later in June. This pattern
was prevalent throughout the marsh, from bayous through mid
channels, with main peaks occurring in June (Figure 9).
Marine estuaries attain peak larval densities earlier in

spring probably as a consequence of latitudinal and climatic

117

differences (Pearcy and Richards 1962; Pendleton and
Copeland 1979; Pearcy and Myers 1974). A variety of inland
freshwater aquatic habitats, including lakes and rivers,
demonstrate peak larval abundance between May and June as in
the Pentwater Marsh (Keast 1980; Hess and Winger 1976).
However, separate bimodal peaks are not usually
distinguishable (Krause and Van Den Avyle 1979). Multiple
peaks of abundance are quite common and distinct in marine
estuaries where two separate waves of larvae can be
identified. Pendleton and Copeland (1979) identified a late
March spawning run of primarily estuarine residents followed
by prolonged influx of ocean-spawned larvae through late
August. Pearcy and Richards (1962) described a similar
pattern but characterized the bimodal peaks as
demersal—egged larvae followed by larvae of pelagic-egged
species later in the season.

The bimodal peaks of abundance in Pentwater Marsh were
not completely analogous to those of the marine estuary.
While the initial peak in larval density was composed
largely of marsh-spawned gizzard shad, cyprinids, and yellow
perch, the second peak represented primarily carp and
various centrarchids which were also littoral spawners
(Figure 8) (Scott and Crossman 1978). Of these major marsh
species, only gizzard shad could be classified as pelagic
spawners. Although gizzard shad eggs are adhesive and
demersal, adult spawning behavior and egg dispersal was

observed and documented (Miller 1960) in open-water.

118

Perhaps the analogy of marine estuary and fresh-water marsh
remains valid, considering the late July influx of the
pelagic-spawning alewife from Pentwater Lake (Table 21).
According to preliminary drift measurements, substantial
numbers of alewife eggs and larvae were transported from
lake to marsh through seiche activity (Table 20). Larval
drift in the Pentwater Marsh seems analogous to the tidal
transport of marine-spawned larvae and eggs in the marine
estuary.

Larval fish diversity, as measured by a Shannon-Weaver
index of 1.08 in Pentwater Marsh (Appendix 0.1), was lower
than most marine estuarine values which range from 1.0 to
2.0 (Shenker and Dean 1979; Dahlberg and Odum 1970). A
lower number of species and the dominance of a few selected
species minimizes freshwater larval fish diversity estimates
(Miller and Guillory 1980). For example, in Pentwater Marsh
carp predominated, composing nearly 75% of the total larval
catch. Furthermore, the total count of 18 species in
Pentwater Marsh is nearly half that of estuarine systems
(Pendleton and Copeland 1979; Pearcy and Richards 1962;
Pearcy and Myers 1974). This discrepancy may reflect a
latitudinal and climatic gradient (Heck and Orth 1980), or
perhaps a pattern of decreasing diversity from salt to fresh
waters (Harrel et al. 1967).

Few studies have employed diversity indices to describe
freshwater wetlands. Jude et al. (1980) described 10 taxa

(also without splitting cyprinids) in the Pigeon River

119

wetland. The St. Mary's River wetlands included 13 larval
fish taxa as opposed to 8 taxa found in the nearby river
channels (Liston et al. 1981b). A Shannon-Weaver index of
1.87 as calculated for the macrophyte beds of the St. Mary's
River, is substantially higher than the community diversity
index of 1.08 calculated for Pentwater Marsh (Appendix 0.1).
Part of the discrepancy may be due to the less even
community of Pentwater Marsh with a species evenness score
of 0.30 versus 0.73 for the St.Mary's River wetland
(Appendix G.3). Carp were a considerably less dominant

member of the St. Mary's River community .

Diel Patterns of Diversity, Abundance, and Distribution
Dahlberg and Odum (1970) cautioned that daily
variations in diversity values may exceed monthly
variations. And indeed, larval fish diversity values of
Pentwater Marsh varied greatly, particulary between day and
night sampling series (Appendix H.1). Separate calculations
of diversity over day and night showed higher marsh
diversity by day over most sample dates. This was somewhat
perplexing considering the higher nighttime larval fish
catch. There were some indications of higher nighttime
diversities in channels but not bayous suggesting the trend
was not simply related to the time of sampling and larval
catch. Certainly, channel diversity would be expected to
peak at night when larvae of many species congregate in

surface waters (Gale and Mohr 1978; Storck et al. 1978;

120

Dahlberg and Odum 1970; Cole and MacMillan 1984) and display
decreased avoidance of gear (Bridger 1956; Houde 1969). In
bayous diel vertical movements are less relevant to larval
capture, although net avoidance and differences in larval
behavior may influence net retrieval efficiencies. At
night, carp comprise a more substantial part of the bayou
larval fish community, decreasing species evenness
(Appendix.B.l). Low species evenness, and not low species
richness, creates the illusion of reduced diversity by
night.

With few exceptions, larval abundance was greatest by
night rather than by day (Appendix B.1). Carp larvae
although with the largest day/night differential were not
the only species exhibiting this pattern; cyprinids, yellow
perch, centrarchids, and northern pike were all collected
predominantly at night. Brook silversides were never
collected by day. This daytime reduction in total larval
fish abundance occurred across all marsh regions and
stations. Gear inefficiency and larval avoidance may be
partially responsible. However, there is also evidence of
fish movements into areas not readily sampled by day. The
daytime movement of larvae to deeper water has already been
mentioned (Gale and Mohr 1978). Furthermore, larvae tend to
congregate in feeding schools by day which create patchy
distributions not necessarily corresponding to the limited
sample stations (Major 1977). This "patch" theory may

apply to the channels and bayou-mouths, but was not

121
supported by larval fish collections of the shallow-water
bayous. Larval fish exhibited higher nighttime coefficients
of variation reflecting greater heterogeneity of
distribution (Table 11). Such a trend was not surprising
given the predominance of carp larvae within the bayous.
Juvenile carp, bullheads, and largemouth bass are known to
congregate in dense schools by night maintaining position
by tactile responses between schooling individuals (Elliot
1976; Hunter and Wisby 1964).

Alternatively, diel habitat preferences may not
correspond to sample sites. Pendleton and Copeland (1979)
observed that postlarval fishes tend to congregate along the
marsh edges by day with subsequent decreasing vulnerability
to capture. Drop-net samples were routinely taken within
clearly defined vegetation stands and rarely at the edge of
macrophyte beds. Open water and the associated edge
represent only a small component of the shallow-water bayou
system, but may be the area of greatest larval fish
congregation. Certainly, these protected pools harbor high
densities of zooplankton and macroinvertebrates (Voigts
1976) attractive to larval fish which feed by day (Blaxter
1975). This hypothesis was not fully assessed within the
present sampling program and deserves further attention in
the future.

Comparisons of day and night abundance across marsh
stations may reveal the occurrence of diel larval fish

movements. For example, carp were generally present in

122

equal or greater abundance by day than by night in the
bayou—mouths (Figure 9). This, when coupled with the
dramatic daytime reduction in bayou carp densities, suggests
a daytime shift in distribution towards the deep waters of
the bayou-mouths. On a smaller scale, carp appear to favor
shallow-water emergent vegetation by night with dispersal to
deep-water submergent and floating-leaf vegetation by day
(Figure 12). A similar diel distribution was observed for
the other cyprinid species late in the sample season
(Appendix B.1; Appendix B.3). On most sample dates, mean
cyprinid lengths were larger in the shallow-water bayous by
night and in the bayou-mouths by day (Figure 23) which may
indicate a diel migration of the larger, more mobile,
mesolarval and metalarval cyprinids. Unlike carp,
cyprinids appear to congregate in feeding schools by day
dispersing at night (Emery 1973). Schools of postlarval
cyprinids were often observed moving through the deeper
sections of the marsh bayous during daylight hours (personal
observation).

Yellow perch also exhibit diel shifts in distribution.
Larval densities were higher in the bayou-mouths and lower
in the marsh channels (Figure 26). A number of authors have
remarked on higher daytime yellow perch densities (Houde
1969; Jude et al. 1980; Liston et al. 1980); but these
studies have dealt predominantly with pelagic lacustrine
systems. Jude et al. (1981) studying littoral palustrine

systems similar to Pentwater Marsh, observed highest larval

123

yellow perch densities by night. Unlike other species,
yellow perch larvae may congregate in the upper water levels
by day (Noble 1970). However, in shallow vegetative areas,
this shift in vertical distribution may be less pronounced
than diel patterns of habitat preference.

In Pentwater Marsh, most larval fish appear to move to
shallower, more densely vegetated habitats at night.
However, a number of studies have shown young fish
congregate in macrophyte beds by day in order to avoid
predation (Faber 1967; Werner 1967; Brown and Colgan 1982).
Most larval fish are sight feeders, feeding primarily by day
(Blaxter 1975; Elliot 1976) when zooplankton often
concentrate in open waters (Voigts 1976). Larvae require an
inordinate amount of energy for growth and development and
failure to feed can lead to immediate or latent mortality
(Blaxter and Hempel 1963; Lawrence 1972). It is possible
that the risks of predation do not outweigh the risks of
starvation during this critical period of initial feeding.

A diel migration between shallow and deeper waters may also
be related to environmental parameters. As suggested by
Adams (1976) and McCauley (1982), adult fish move into
shallow waters primarily at night in order to avoid daytime
temperature extremes. However, conditions of the upper
marsh are potentially inhospitable by night when dissolved
oxygen levels may drop below the limits of larval fish
tolerance (Figure 6). Perhaps mobile larvae benefit from

dispersal to the deeper waters by night rather than day.

124

Reis (1977) observed marine postlarval fishes utilize the
upper estuary by day, returning to deep water channels at
night. He attributed this behavior to foraging strategies
and predation avoidance. Elliot (1976), however, observed a
pattern similar to that of Pentwater Marsh, where schooling

largemouth bass larvae migrated to shallow waters by night.

Regional Patterns of Diversity and Distribution

Trends in abundance were also encountered across the

 

 

major marsh regions of Pentwater Marsh. For example, yellow
perch larvae appeared in the upstream bayous (X,Y) a week
before reaching downstream bayous of W and Z. Upstream
bayous were significantly warmer by day perhaps due to
shallower water depths (Appendix A.2). Adult yellow perch
were first observed in spawning congregations in the
upstream bayous. Similarly, black crappie, northern pike,
and brook silversides may have spawned sooner in the
upstream areas resulting in a temporal succession of peak
species abundance across the marsh. Franklin and Smith
(1963) documented a similar trend for northern pike which
they also attributed to differential temperatures.

Temporal successions were less pronounced for larval
species spawned later in the season. By mid-June, there was
less of a temperature differential between the bayous
(Appendix A.2) and few temporal patterns of larval
distribution were evident (Appendix B.2). However, the

early Lepomis spp. larvae were largely confined to the south

125

branch of the upper Pentwater River (Figure 25) while
later-spawned larvae were found primarily in the downstream
bayous. Subsequent electroshocking in the south branch
recovered a number of adult bluegills which were uncommon to
other areas of the marsh. Bluegills initiate spawning prior
to pumpkinseed sunfish and at cooler water temperatures in
the late spring (Breder and Rosen 1966). Lepomis spp.
temporal and regional succession may thus reflect
differential species requirements as well as environmental
gradients.

Temporal successions may be based on active transport
of larvae as well as staggered spawning runs. A number of
authors have noted such a phenomena in marine estuaries.
Larval fish seem to reside in the upper reaches of tidal
creeks as protolarvae, gradually migrating downstream as
they grow (Herke 1971; Haven 1957; McHugh 1966; Hansen
1970). In freshwater systems, downstream migrations have
been documented for white suckers (Geen et al. 1966),
alewife (Brown 1972), and northern pike (Carbine 1943; Hunt
and Carbine 1951; Fago 1977). In Pentwater Marsh, although
there was a pronounced succession of larval abundance due to
initially staggered spawning activity, few species exhibited
clearly defined downstream movements. For example, carp and
other cyprinids were found across almost all stations
throughout much of the summer. However, small carp larvae
predominated in upstream channel collections. The smallest

larvae were usually found at mid channel (Appendix E.5) and

126

in larval drift at the marsh outlet (Table 15). The
presence of carp in channels and drift may be attributed to
the passive transport of weakly swimming protolarvae rather
than active downstream movements.

Similarly, alewife larvae appear to passively move
through the marsh. Alewife spawning was heaviest
immediately upstream from the marsh outlet. Many of the
eggs and protolarvae may wash from the marsh soon after
spawning. Few postlarval alewife were encountered in the
marsh. Active downstream movements of northern pike have
been documented at approximately 20 to 30 mm in length
(Hunt and Carbine 1951; Forney 1968). However, in Pentwater
Marsh, northern pike were collected only in small numbers,
primarily as protolarvae, and almost exclusively in emergent
vegetation of the shallow-water bayous.

Diversity estimates lend further support for the
existence of larval fish successions across the Pentwater
Marsh. Although upstream larval diversity did not decrease,
downstream diversity clearly increased suggesting a pooling
of species towards the marsh outlet (Appendix 0.1).
Downstream larval movements may partially explain this
pattern. However, an alternative hypothesis includes the
influx of Lake Pentwater and Lake Michigan faunas and the

intermixing of pelagic and demersal-spawned fishes.

127

Larval Fish Distribution and Vegetative Patterns

Many species of larval fish appear to move offshore
into pelagic waters only to return to littoral vegetative
cover several weeks later (Hokanson 1977; Kelso and Ward
1977; Amundrud et al. 1974; Faber 1967; Werner 1967;
Beard 1982). Such a migration may be necessary to supply
larvae with suitable prey items, particularly during the
critical period of yolk absorption and the onset of
exogenous feeding (Kelso and Ward 1977). At this stage, the
important criteria for food selection are prey size (Wong
and Ward 1972; Hansen and Wahl 1981), visibility (Braum
1967), and vulnerability to capture (Blaxter and Hempel
1963). Littoral zooplankton tend to be larger than their
pelagic counterparts (Ward and Whipple 1959) particularly
when adult fish exert a significant selective pressure
(Galbraith 1967; Helfrich 1976). Perhaps, larvae require
the smaller pelagic zooplanktors for successful first
feeding, and thus must migrate to deeper water during this
critical period of development. Siefert et al.(1973)
observed yellow perch feeding on small pelagic copepod
nauplii soon after yolk absorption but switching to larger
littoral cladocerans (Bosmina spp.) as metalarvae. Upon
attainment of 6 to 7 mm, the cyprinids, pumpkinseed sunfish
and yellow perch of Pentwater Marsh were observed to shift
from emergent to submergent vegetation and from
shallow-water bayous to the bayou-mouths (Appendix B.3;

Appendix B.1). Both yellow perch and black crappie were

128

collected as smaller protolarvae in the shallow—bayous
approximately two weeks before their appearance as
mesolarvae in bayou-mouths and channels (Figure 26; Appendix
B.1). Due to increasing gear avoidance past the 10 mm stage
(Noble 1970), it was impossible to determine if these
species also exhibit the return movements to shallow
vegetative beds at lengths of approximately 20 mm lengths as
suggested by Storck et al.(1978) and Werner (1967).

Northern pike did not follow the predicted patterns of
deep-water migrations. In fact, northern pike were larger
(>7mm) in the emergent collections than in the deep water
submergents (Appendix E.3; Appendix F.2) perhaps due to the
preference for submergent spawning sites and the shoreward
movements of larvae shortly after hatching (McCarraher and
Thomas 1972; Thomas and Howard 1970; Frost and Kipling
1967). Franklin and Smith (1963) stated that protolarvae do
not move far after hatching. However, as Thomas and Howard
(1970) observed, larvae may actively seek out emergent stems
where they attach and remain for approximately 6 to 10 days.
Preliminary stomach analysis indicated larval northern pike
fed on copepods and ostracods (Jokerst 1982), both of which
occur in high densities within the emergent zone (Fasano
1982). Pike quickly begin feeding on larger invertebrates
and fish (Hunt and Carbine 1951; Fago 1977), perhaps not
needing to migrate to deeper water for food. Those fish

which do move to open water, may suffer significant

129

mortality due to yellow perch and centrarchid predation
(Franklin and Smith 1963).

Like northern pike, carp larvae may experience intense
predation pressure in open-water areas (McCrimmon 1968).
Carp larvae were also larger in emergent than submergent
vegetation, particularly by day (Figure 18; Appendix E.3).
Carp initiate feeding soon after hatching and prior to
yolk-sac absorption (McCrimmon 1968). First feeding may
include rotifers and phytoplankton which are common
throughout the littoral zone of the marsh. Later, larval
carp feed on ostracods and chironomids (Jokerst 1982;
Lindquist et al. 1943) which are prevalent in emergent
vegetation (Fasano 1982; Voigt 1976). Unlike centrarchids
and yellow perch, carp larvae tend to select larger species
and individuals for prey items (Losos and Hetesa 1973)
perhaps in keeping with foraging strategies adapted to the
vegetated shallow-water marsh.

Deep-water migrations may be reflected in overall
diversity trends. As mentioned earlier, larval diversity
increased in the lower Pentwater Marsh, perhaps as a result
of larval movements downstream. However, there was also a
pattern of declining diversity in the shallow-water bayous
followed by a decline in diversity of bayou-mouths
(Figure.28). Declining bayou diversity may correspond to a
loss of species to deeper water, particularly during late
May when a number of spring-spawned species attain

mesolarval stages. During this time, both emergent and

130

submergent diversity decreased while floating-leaf diversity
and species richness increased (Figure 29). Peak diversity
occurred much later in July as fishes increasingly utilized
the more open-water floating-leaf vegetative stands.

Weinstein (1979) suggested estuarine species diversity
was greatest near a habitat interphase such as between marsh
and estuarine bay. This "edge-effect" occurred in Pentwater
Marsh at marsh outlet and bayou-mouths. According to
Johannes and Larkin (1961), an edge effect may also occur
on a much smaller scale between vegetation patches within
the littoral zone. Foraging fish tend to congregate along
vegetative edges where prey items are in high abundance
(Voigts 1976; Andrews and Hasler 1943; Dvorak 1978), of
appropriate size ranges, and of greater vulnerability to
capture (Savino and Stein 1982). Unfortunately, drop-net
sampling was biased towards the middle of vegetation
patches, where vegetative types were clearly distinguished.
However, emergent samples were often taken at the edge of
vegetative stands in order to avoid shallow-water and
cumbersome vegetation densities.

Larval fish densities were generally greater in
emergents than in submergent and floating-leaf vegetation
(Appendix B.3). However, towards the end of July, diversity
was low within the emergent vegetation, perhaps due to a
predominance of carp larvae (Figure 29). Total larval fish
density was significantly correlated with emergent cover

(Table 22). In particular, northern pike, carp, and yellow

131

perch were associated with the emergent edge. Emergent
shoreline development (Table 1) was highest in bayous X and
Y, as were seasonal larval fish diversities (Appendix G.1).
However, densities did not appear to be related to the
degree of vegetative interspersion (Table 1; Appendix B.2).
Vegetative structure and diversity may be important
environmental clues increasing chances of larval survival
(Miller and Dunn 1980) and dictating larval distribution and
abundance (Heck and Orth 1980). Johannes and Larkin (1961)
predicted prey species when not actively feeding should be
found in the higher density vegetation of mid—patch.
Submergents are particularly protective habitats and were
correlated with the abundance of pumpkinseed sunfish
(p<0.10) which are prime targets of predation (McCrimmon
1968; Timmons 1979) (Table 22). And indeed, pumpkinseed
sunfish abundance was highest in bayous W and 2 (Figure 25)
which were characterized by dense monospecific vegetative
stands with low emergent interspersion (Table 1). However,
as indicated by Marean (1976) in his study of Lake Erie
marshes, total vegetation cover was not a significant factor
in correlations with larval northern pike abundance. In
Pentwater Marsh few species were related to percent
vegetative cover (Table 22). Rather, vegetation type,
diversity, and structure were much more important in
determining larval fish abundance and distribution

(Appendix.B.3).

132

Community Interactions

Cannibalism and piscivory among larval and juvenile
fishes can be substantial mortality factors, ultimately
directing larval fish distribution (Chevalier 1973).

Keast(1978) observed young-of-the-year yellow perch
"gorging" on 20 to 30 mm centrarchids in the dense
macrophyte beds of Lake Opinicon, Ontario. Early and
fast-growing larvae such as the northern pike may attain
sufficient size (Appendix E.1) to effectively prey upon the
late-spawned larvae of carp, brook silversides, johnny
darters, cyprinids, and largemouth bass (McCrimmon 1968).
Frost (1954) observed northern pike between 35 and 200 mm
fed primarily on yellow perch fry.

Since extensive food habit analysis was not included in
this study, it is impossible to clearly define predator-prey
relationships. However, it is feasible to examine species
associations which may reflect predatory interactions.
Northern pike and yellow perch were found in positive
associations (cf-0.37) on May 12 (Table 17). However, on
this date, northern pike were less than 20 mm (Appendix E.1)
and not likely piscivorous (Frost 1954; Jokerst 1982).

Greatest association occurred at night rather than during
the daytime feeding period (Table 18). Northern pike and
yellow perch appear to be associated through similarities of
environmental requirements rather than direct piscivory.

A similar positive species association was apparent

between carp and cyprinids by both night (cf-0.38) and by

133

day (cf-0.36). Carp and other cyprinids may actively school
to decrease predation or to increase chances of food patch
encounter. However, aggregations may also indicate shared
requirements and responses to environmental gradients.
Hergenrader and Hasler (1968) observed daytime schooling
aggregations of young cyprinids and yellow perch in the
littoral zone Of lakes. Indeed, the larval cyprinids and
yellow perch of Pentwater Marsh were found in positive
associations by night (Table 17). However, day catches were
too small for analysis. Newly hatched cyprinids may also
be associated with centrarchids due to the nest sharing of
adult cyprinids and centrarchids (Kramer and Smith 1960;
Hunter and Hasler 1965). Cyprinids and Lepomis spp.
exhibited the strongest association among the larval fish
species of the marsh, with a Forbes coefficient of 0.69 by
night. Marean (1976) found northern pike fry densities were
correlated with fathead minnow densities in Lake Erie
marshes. But he suggested no direct associations only that
marsh conditions supporting northern pike larvae also
enhance minnow production. Pentwater Marsh cyprinids and
northern pike larvae were not strongly associated by night,
but increased in association by day (Table 17; Table 18).
Negative species associations may indicate differing
reactions to environmental gradients or actual predatory
depletion of one species by another. From an evolutionary
viewpoint, larval behavior and response to enviromental

gradients reflect an indirect mitigation of competition

134

among species. Estuarine studies indicate that food
supplies are potentially limiting (Ware 1975; Thayer et al.
1974; May 1974; Houde 1977) even to the point of local
resource depletion (Cushing 1973). Larval fish are
generalist feeders (Kenaga 1975; Miller and Dunn 1980),
at least prior to specialization of the digestive system
(Crawford 1973), and thus may compete for shared food
resources. Werner et al. (1977) suggested that while
predatory pressures restrict fish to littoral vegetation,
their spatial distribution within vegetation may be largely
determined by intra and inter specific competition.
However, in the marsh or estuarine habitat prey densities
are extremely patchy and of unreliable magnitude and
duration (Setzler et al. 1981). It is likely that encounter
with prey patches is the critical factor in larval fish
survival rather than on—site competition for those food
resources.

Indeed, few negative associations were detected in
Pentwater Marsh. Only carp and Lepomis spp. were
significantly, although weakly, disassociated with each
other as seen on June 22 by day and by night (Table 18 and
19). Further examination shows a strong separation of these
species by vegetation types, with carp in emergents and
Lepomis spp. largely confined to submergent vegetation
(Appendix B.3; Table 1). Carp begin to specialize earlier
than most larvae, feeding near the substrate on ostracods

and chironomids (Jokerst 1982; McCrimmon 1968), while

135

Lepomis spp. tend to feed on epiphytic and pelagic
cladocerans and copepods (Siefert et al.1973; Beard 1982).
Direct avoidance of competition or predatory depletion is
thus a less likely explanation for these species
distributions than differing environmental and forage

requirements.

Environmental Factors

According to Miller and Dunn (1980), larval movements
in response to environmental conditions are energetically
more expensive than physiological tolerance of adverse
conditions, especially if these movements displace larvae
from food abundance. However, there are certain limits to
the tolerance of larval fishes which have been documented
for temperature, dissolved oxygen, and turbidity (Hockanson
et al. 1973; Siefert et al. 1973; Auld and Schubel 1978).

Temperature is a fundamental factor determining the
timing and magnitude of spawning activity (Swee and
McCrimmon 1966; Kindschi 1979; Keast 1980; Beard 1982).
Many species of fish will delay spawning, spawn elsewhere,
or even forgo spawning entirely, if temperatures are not
within a suitable range (Priegel 1970; June 1970; Frost and
Kipling 1967). As suggested earlier, temperature gradients
may determine the locality of spawning and subsequently
influence larval fish distribution.

Temperature is also a major determinant of zooplankton

and invertebrate distribution (Hazelwood and Parker 1961).

136

It is crucial that larval fish begin feeding in synchrony
with the seasonal pulse of the appropriate prey species.
In Pentwater Marsh, peak zooplankton abundance was measured
at the end of May (Fasano 1982) when ambient water
temperatures ranged between 14 and 170 C day and night
(Appendix A.1). Indeed, peak larval density and diversity
seemed to coincide with the high zooplankton abundance of
late spring (Figure 9; Figure 28). Larval fish growth may
be indirectly influenced by food supplies or directly
controlled by ambient water temperatures (Fonds et a1.
1973).

Fluctuations in temperature may adversely affect larval
survival, growth and development (Edsall 1970; Fonds et al.
1973). It has been suggested that larvae are particulary
sensitive both in the early embryo period and as yolk-sac
fry soon after hatching (Franklin and Smith 1963; Hokanson
et al. 1973). Prolonged and precipitous drops in water
temperature may lead to structural abnormalities with
subsequent latent mortality expressed at the onset of
exogenous feeding (June and Chamberlain 1959). Johnson
(1957) observed 100% mortality of nothern pike eggs
subjected to sudden drops in temperature below 100 C.
In Pentwater Marsh, water temperatures were generally lower
than 100 C at the time of spawning, but were not measured
with enough frequency to observe fluctuations through early
development. However, records of air temperature indicate a

rapid decline in nighttime temperature to 10 C during the

137

second week of April. At this time, researchers observed
ice formation in the shallow-water bayous at night. In
retrospect, northern pike catch was lower in 1982 than in
subsequent years, perhaps reflecting temperature-related
mortality. As suggested by Frost and Kipling (1967) for
northern pike, and by Clady (1976) for yellow perch,
year-class strength may be at least partially associated
with first year ambient water temperatures.

Temperatures warmer than optimal can be equally
disadvantageous. Eggs and larvae incubated under elevated
temperatures hatch at less developed stages and may
extinguish yolk-sac supplies before initial exogenous
feeding (Lillelund 1967). Although larval growth may be
accelerated, metabolism and respiration are also elevated
leading to increased mortality and physiological stress
(Hokanson et al 1973).

In Pentwater Marsh, the rise in water temperature was
gradual and typical for most inland waters of the Great
Lakes region (Figure 4). In May, the shallow water bayous
maintained higher water temperatures (by 30to 50 C) than the
bayou-mouths and river channels, particularly at night
(Appendix A.1). Temperature modification through larval
movements may have been apparent at this time. It is
interesting to note that the predominant larval species
present during May were species with significant
correlations with ambient water temperature (Table 22). For

example, yellow perch and carp were positively related to

138
higher temperatures, whereas cyprinids were associated with
cooler water. The relationships were unclear since
temperature was inter-correlated with a number of other
factors including time of sampling and vegetative types
(Table 3). Cyprinid larvae were obtained in greater numbers
by night (Figure.21), and were significantly (p<0.10)
correlated with cooler water (Table 28). But the cyprinid
distribution primarily within the warmer emergent zone
(Figure 21) does not explain the cool water association.
Apparently, cyprinids either select temperatures within
vegetation types or were related to other factors indirectly
associated with water temperature.

Temperature and dissolved oxygen are closely related
(Table 4). Higher temperatures not only decrease the oxygen
available to respiring larvae, but also increase the lethal
effects of low oxygen levels (Siefert et al.1973). Reduced
oxygen may retard development (Gulidov and Popova 1982),
result in asphyxiation (Peterka and Kent 1976), or lead to
starvation, particularly at the onset of initial feeding
(Siefert et al. 1973). Greatest sensitivities occur in
larvae one week after hatching and prior to initiation of
opercular ventilation (Spoor 1977). According to Spoor
(1977), a lack of dissolved oxygen forces largemouth bass
larvae to swim close to the surface increasing chances of
predation and displacement from the protection of the nest.

In Pentwater Marsh, northern pike were the only species

significantly related to higher dissolved oxygen levels

139

(Table 28). However, these larvae were primarily found in
emergents where nighttime dissolved oxygen was particularly
low (Figure 6; Appendix A.3). This relationship may
represent the active distribution of larvae along dissolved
oxygen gradients within the emergent zone. Our observations
suggest northern pike were associated with the emergent edge
which may offer more suitable oxygen levels . On the night
of May 12, when peak northern pike densities were
encountered, dissolved oxygen measurements ranged from 5.3
to 6.3 mg/l in floating-leaf vegetation and 3.5 to 4.5
mg/l in emergents (at 190 C) (Appendix A.3). Although
northern pike eggs may suffer high mortality at 4.0 mg/l
(Peterka and Kent 1976), pike larvae can withstand levels
as low as 2.0 mg/l according to Fago (1977). However, even
moderately low dissolved oxygen levels may adversely affect
the growth and physical condition of larval fishes
(Doudoroff and Shumway 1970). Low dissolved oxygen levels
may be particularly critical when coupled with other adverse
environmental conditions such as high temperature or
hydrogen sulfide (Adelman and Smith 1970). Marean (1976),
in his study of coastal Lake Erie marshes, also noted that
northern pike fry density and survival were positively
correlated with dissolved oxygen measurements (Figure 23).
Unlike northern pike, carp were negatively related
(r--0.50; p<0.01) to dissolved oxygen (Table 22). Nighttime
carp abundance was high in emergent and submergent (Appendix

B.3) vegetation where dissolved oxygen was lowest

140
(Figure.6). As mentioned earlier, carp prefer the dense,
shallow water emergent beds, perhaps in avoidance of
predation or a response to the availability of appropriate
food items.

High levels of suspended sediments may reduce dissolved
oxygen levels (Morton 1977). However, turbidity and
dissolved oxygen were not significantly correlated in the
months sampled at the Pentwater Marsh. Suspended sediments
may directly affect larval fish by decreasing gill
efficiency (Auld and Schubel 1978) or clogging the gut
(Peddicord and McFarland 1978). Indirect effects include
interference in feeding and social behavior, or disruption
of normal distributional patterns. A number of authors have
observed that larvae concentrate in the surface layers of
very turbid waters (Swenson and Matson 1976); Gale and Mohr
1978) where they are more susceptible to predataion and
drift.

Although evidence suggests turbidity may be deleterious
to larval fish, northern pike, cyprinids, and yellow perch
were associated with higher water turbidity (Table 22).

Only pumpkinseed sunfish were negatively related to
turbidity. There was a pattern of increasing turbidity from
submergent to emergent to floating-leaf. Submerged
macrophytes tend to trap sediment and detritus actually
decreasing water turbidity (Heck and Orth 1980).

Pumpkinseed sunfish tended to congregate in submergents

whereas northern pike, cyprinids, and yellow perch were

141

collected primarily in emergent vegetation (Appendix B.3).
It would appear that larval fish are distributed primarily
according to vegetation type and turbidity is only a
secondary factor.

Depth was inter-correlated with turbidity as well as
dissolved oxygen and vegetative type (Table 4). Depth was
slightly correlated with the time of sampling reflecting a
bias towards deeper drop—net sites by night (Appendix A.1).
Deep water offers insulation from fluctuations in
temperature, dissolved oxygen, and related parameters.
Small zooplanktors may be in greater abundance and more
accessible than in the shallow marsh. However, larval
movements to deep water increase vulnerability to predation
and may subject larvae to increased turbidity and
turbulence. 0f the major marsh species, only yellow perch
were positively correlated with deep water. Carp, on the
other hand, were strongly associated with shallow water
habitats (Table 22). As suggested earlier, carp larvae may
be able to find adequate food supplies within the
shallow-water emergents; whereas, yellow perch must migrate
to deeper water for the smaller zooplankton prey. Carp are
relatively hardy and may be able to survive the low oxygen
and high temperatures of marsh shallows (Lomholt and
Johansen 1979). The relationship of northern pike to depth
was negative but insignificant. Marean (1976) found no

correlation of northern pike abundance with depth, but did

142

note the relationship of pike to vegetation types which grow
in waters less than 50 cm in depth.

Pentwater Marsh, and similar coastal wetlands, may
undergo substantial fluctuations in water level due to the
combined effects of seiche and rainfall. Naturally or
artificially lowered water levels would not only decrease
the inhabitable area of preferred habitats, but could also
adversely affect vegetation type, plant diversity, and other
marsh qualities necessary for successful spawning and early
life survival (Geis 1944). Lower water levels increase
larval mortality due to extreme fluctuations in temperature,
dissolved oxygen, and turbidity (Hunt and Carbine 1951), and
may lead to desiccation, fungal growth, and starvation (Hunt
and Carbine 1951). A number of authors have documented a
reduction of fish year-class strength with low spring water
level. Dropping water levels during egg incubation and
early larval development has been shown to adversely affect
the production of northern pike (Carbine 1943; Franklin and
Smith 1963; Johnson 1957; Hassler 1970), yellow perch
(Nelson and Walburg 1977), walleye (Preigel 1970),
largemouth bass (Pawaputanon 1979; Von Geldern 1971), and
carp (Walburg and Nelson 1966; Pawaputanon 1979).

In Pentwater Marsh, precipitation was high in early
April but decreased quite suddenly by the second week of the
month (Figure 4). Protolarval northern pike were abundant
at this time, primarily in the shallow water emergents

(Appendix B.1). Water levels dropped in early May

143

(Figure.4) displacing, or possibly stranding, larvae in the
upper reaches of the marsh. By late June, however, marsh
water levels began to rise again. Water levels increased by
about 10 cm from June through July, the period of peak carp
spawning activity.

It is unclear how larval carp deal with fluctuations in
water level. Water level draw-downs are commonly used to
control adult carp populations (Shields 1957). A number of
authors have suggested carp reproduction is optimal with
gradually increasing water levels (Walburg and Nelson 1966;
Storck et al. 1978; Sheilds 1957). In retrospect, carp
production in Pentwater Marsh was high relative to that of
subsequent years when water levels were stable or declining.
Larval carp of Pentwater Marsh were concentrated in the
shallows of the upper marsh and showed little inclination to
move to deeper water (Figure 11; Appendix E.1). Reductions
in water level during this period has been a useful
management strategy in the control of carp (Shields 1957;
Swee and McCrimmon 1966). However, the extended spawning
capabilities of carp decrease the effectiveness of such
one-time draw-downs. Widely fluctuating water levels may be
the most successful tactic for increasing egg and larval
mortality. However, such a measure is also likely to
interfere with the reproduction of other marsh inhabitants
including furbearers (Linde 1969), waterfowl (Weller 1978),
and a number of desirable spring-spawning fishes. Moreover,

carp larvae may be able to survive the low oxygen and high

144

temperatures of shallow pools (Sigler 1955). Draw—downs may
have the greatest effect by upsetting food availability and
increasing predation (Nelson and Walburg 1977; Pawaputanon
1979). As mentioned earlier, and supported by other studies
(Crivelli 1983), northern pike predation may be a prime
regulating mechanism of carp populations and would be
particularly effective when carp are displaced from the
protection of shallow-water vegetation.

Larval displacement may also be desirable for the
management of other marsh fishes. As with carp, decreasing
water levels may be implemented to concentrate centrarchids
and increase predatory controls. Summer draw-downs are
occasionally used to increase predation and decrease
stunting among reservoir fish populations (Liston and Chubb
1984). A gradual decrease in water levels is also opportune
for species which must return to the deeper water of
downstream habitats. Larval drift is a critical stage
similar to the stage at first feeding and failure to move at
the appropriate time may determine year-class strength .

For example, northern pike migrate downstream upon
attainment of approximately 20 mm, or about 2 months after
hatching (Hunt and Carbine 1951). According to Forney
(1968), movements may not occur, or may be reduced, if
there is insufficient current exiting the marsh. Northern
pike movements were anticipated in early June in Pentwater

Marsh. At that time, water levels were declining (Figure

145
4), perhaps facilitating the exodus of northern pike

fingerlings from the upper marsh.

Pentwater Marsh as a Nursery Area fgr Fishes
A number of authors (Wells 1973; Jude et al. 1982) have

suggested larval exports from the Great Lakes' coastal
marshes are substantial and of great significance to
neighboring lakes' habitats. Great Lakes species such as
yellow perch (Dorr 1982; Brazo 1984), walleye (Niemuth et
al. 1959; Wells and Mclain 1973), white sucker (Raney and
Webster 1942), burbot (Mansfield et al. 1983), cyprinids
(Mansfield 1984; Wells and House 1974; Cosentino 1983),
rainbow smelt (Jude et al. 1982), trout perch (House and
Wells 1973), gizzard shad (Miller 1956), and alewife (Brown
1972) may all utilize the warmer temperatures of inland
waters tO advance spawning and enhance survival. Many of
these species return to the Great Lakes as larvae or early
juveniles with a competitive edge over the smaller and less
developed, lake-spawned individuals (Mansfield 1984).

The significance of tributary spawning is perhaps best
documented for the yellow perch. In the Great Lakes, yellow
perch are observed in a bimodal peak of abundance comprised
of both inland and lake-spawned individuals (Jude et al.
1982; Perrone et al. 1983). Liston et al. (1981) documented
a bimodal peak of larval abundance in Lake Michigan, just

7 km to the north of Pentwater Marsh. Brazo (1984), in his

study of the Pere Marquette Marsh, estimated that 0.75

146

million larval yellow perch drifted from marsh to Lake
Michigan during 1981. He suggested this input accounted for
the magnitude of larval perch abundance found in nearby Lake
Michigan in early May. At the estimated population levels
of 5 million, Pentwater Marsh yellow perch could be of
extreme significance if entering the nearshore Great Lakes
system.

Unfortunately, full-scale drift sampling began too late
in the season to properly assess the transport of yellow
perch larvae from Pentwater Marsh into Lake Michigan.
However, circumstantial evidence suggests yellow perch
exports were not substantial. Although yellow perch
production was high in the shallow-water bayous, channel
densities were lower than peak abundance in nearby Lake
Michigan (Table 21). Pentwater Marsh supports a year-round
yellow perch population of sufficient magnitude to account
for the observed spawning and larval fish abundance. At
least some juvenile and yearling yellow perch appear to
remain in the system. Although it is possible some larval
yellow perch return to Lake Michigan, it is doubtful that
this export was numerically significant. Most
inland-spawned yellow perch, as apparent in nearby Lake
Michigan collections, may come from the larger Pere
Marquette Marsh, 20 km to the north.

Other Great Lakes species, believed to be major marsh
users, were not collected in high numbers as larval fish.

White sucker, for example, although the major species in

147

adult collections (personal communication, Dan Brazo), were
rarely caught as larvae in the marsh (Appendix B.4). These
larvae were around 10 mm in length, confined to the river
channels, and collected at night. As suggested by Geen et
al. (1966), 10 mm white suckers tend to migrate downstream
at night. It is likely, white suckers did not directly
utilize the marsh as spawning and nursery areas. Rather,
they were collected passing through the system as metalarvae
and adults. Drift sampling was not sufficient to determine
if larval white suckers were also exported from the marsh.
Juvenile suckers were not found in the marsh, suggesting the
area does not serve as a major staging area.

Alewife larvae were also found in smaller numbers than
anticipated, particularly considering the magnitude of
spawning activity observed throughout much of the summer.
However, as also observed by Mansfield (1984) in Little
Pigeon Creek Marsh, alewife were confined to a relatively
small area around the marsh outlet. Most eggs and larvae
may have been quickly swept out of the marsh into Pentwater
Lake before attaining post larval mobility (Table 20;
Appendix E.4). Brazo (1984) observed a similar phenomenon
in nearby Pere Marquette with much spawning activity but low
larval alewife densities. He attributed this incongruity to
high egg and larval mortality within the marsh. He observed
highest densities of larval alewife flowing from Lake
Michigan into the marsh and adjoining bay. Likewise,

Pentwater Marsh drift collections of June 30, suggest there

148

may also have been a net input of larvae into the marsh
(Table 20). Alewife densities were substantially greater in
Pentwater Lake (Table 20). Limited drift collections at the
lake outlet could not determine if reverse flow was also
occurring from Lake Michigan. Alewife may spawn most
successfully throughout Pentwater Lake with little
interaction with the Pentwater Marsh. Pentwater Lake had an
estimated peak density more than three times greater than
nearshore Lake Michigan (Table 21). However, it is somewhat
presumptuous to assume larval exports may be significant in
comparison to Lake Michigan populations. Alewife spawning
is extensive and ubiquitous along most of the Lake Michigan
shoreline.

Common carp are an obvious major component of the
Pentwater Marsh system, but only during spawning activity
and peak larval abundance. Although the evidence is largely
indirect, carp do not appear to be residential species as
previously assumed. Liston et al. (1981) documented the
congregation of adult carp in the reservoir of the Ludington
Pumped Power Storage Plant 7 km to the north of Pentwater
Marsh. Throughout the summer, large schools of adult carp
can be observed moving along the nearby Lake Michigan
shoreline. Carp, however, are rare components of the Lake
Michigan ichthyoplankton and likely rely on the Great Lakes
tributaries and marshes as spawning and nursery areas. In
Pentwater Marsh, carp were a substantial component of larval

drift at the marsh outlet (Table 21). Most of these

149

individuals were eggs and protolarvae which were likely
passively caught up in river currents exiting the marsh.
Peak larval output coincided with peak marsh densities
(Figure 12; Table 21). However, several weeks later,
approximately 2 million carp (net) were estimated entering
the marsh during seiche activity. Most of these larvae were
likely products of delayed spawning in the cooler waters of
Pentwater Lake. Carp exports appear to be balanced by
seiche imports later in the season. Carp are perhaps the
greatest mystery of the marsh. It is unlikely that larval
exports account for the virtual disappearance of carp after
attaining approximately 20 mm in length. Adult carp
certainly move into the Great Lakes habitat, however, there
is little information on the stages in between. It seems
likely that juvenile carp exit the marsh, perhaps moving to
the deeper waters of Pentwater Lake.

According to Mansfield (1984), other cyprinids,
particularly spottail shiners, may make similar use of
tributary marshes. However, there is no evidence that
cyprinids of Pentwater Marsh were also of Great Lakes
origin. The great majority of the cyprinid larvae were
identified as golden shiners or bluntnose minnows, both of
which were common to the marsh habitat throughout the sample
season and found at all stages of development. However, an
estimated 45,000 cyprinids may have drifted from the marsh
each day during peak export of late May (Table 19). This

value approaches the estimated peak export of 100,000

150
spottail shiner larvae per day from the Little Pigeon Creek

Marsh also on Lake Michigan (Mansfield 1984). Cyprinid
larvae may indeed exit the marsh to inhabit Pentwater Lake,
although it is impossible to determine if these larvae
eventually reach Lake Michigan.

Other species of possible non-residential status
include black crappie, gizzard shad, and northern pike.
Black crappie were observed to spawn in the downstream
portion of the marsh, and subsequent larval densities were
highest around the marsh outlet. Black crappie larvae soon
disappear from marsh samples implying movements to other
areas. Juvenile black crappie may take up residence in the
Pentwater Marsh, perhaps with some export to Lake Michigan.
Gizzard shad protolarvae were found in high abundance in the
shallow-water bayous as well as the bayou-mouths. As in the
case of black crappie, gizzard shad larvae soon disappear
from fish collections. At this time, gizzard shad were
collected in high numbers in the drift samples, indicating a
movement lakeward. According to Brazo (1984) these species
may remain in the system until attaining juvenile status in
late fall. If so, Lake Pentwater is probably the site of
juvenile retention.

Northern pike, althoughnot a typical Lake Michigan
species, may range as far as Lake Pentwater. Most northern
pike populations are observed to move upstream to spawn and
migrate downstream as fingerlings (Carbine 1943; Forney

1968; Fago 1977). Pentwater Marsh is probably not an

151

exception . Fingerling pike appeared to move into deeper
water through the season and high densities of juvenile
northern pike were observed around the marsh outlet in mid-
July. However, it would be unfair to classify northern pike
as a non-residential species considering the number of
northern pike which remain in the marsh through September.
Moreover, yearling and adult populations seem to rely on the
marsh throughout the year.

The Pentwater Marsh fish community thus includes seven
transient species which only utilize the marsh during part
of their life cycle (Table 10). However, according to the
evidence, only white suckers, carp, and alewife may be
considered to range between the marsh and Lake Michigan.
These Great Lakes transients account for only 172 of the
fish species utilizing the marsh as a spawning and nursery
area. In comparison, estuarine fish communities are
comprised of approximately 702 marine and 30% residential
species (Emery and Stevenson 1957; Weinstein 1979).

However, according to Cosentino (1983) and this study,
residential species compose over 602 of the fish species
utilizing freshwater coastal wetlands. This is not
suggesting we entirely discard the "out-welling" model as
proposed by Dahlberg and Odum (1970) for the Atlantic
estuaries. Carp, alewife, and white suckers, while only a
small component of the diversity, represent over 802 of the
numerical production and are likely a fair proportion of the

fish community biomass. In terms of productivity, larval

152

exports may be quite substantial, if not for downstream
habitats, then for the internal cycling of the marsh itself.

Pentwater Marsh compares favorably with other wetlands
in terms of fish abundance and standing crop. For example,
carp production was estimated at 23 larvae/HA in West Point
Reservoir, Alabama (Pawaputanon 1979) while Pentwater Marsh
had an estimated 350,000 larvae/HA at a comparable
developmental stage (Table 19). Pawaputanon's (1979)
estimates included large expanses of deepwater habitats
whereas our estimates do not include Pentwater Lake which
may interact with the marsh system. Such high densities are
commonplace in cultured ponds (Los and Hetesa 1973).
However, Grygierek et al. (1966) observed stocking rates
above 22,500 larvae/HA result in severe reduction in the
abundance and quality of pond zooplankton. One wonders if
the high abundance and extended dominance of carp larvae had
a detrimental effect on the other more "desirable" marsh
species (northern pike, yellow perch, pumpkinseed sunfish)
of the Pentwater Marsh.

Apparently, Pentwater Marsh was also a high producer of
pumpkinseed sunfish at densities of 7.4 larvae/m:3
(Appendix.A.l) which compares favorably to estimates of 3.1
larvae/m? from Pigeon Lake, Michigan (Jude et al. 1980), and
2.4 larvae/m? in Rough River Lake, Kentucky (Kindschi 1979)
and 1.5 larvae/mi3 from Lake Opinicon, Ontario (Keast 1980).
Similarly, cyprinid production was higher than most aquatic

systems at peak densities of 4.74 larvae/n13 as opposed to

153
2.6 larvae/m3 in the St. Mary's River wetlands (Liston et

al. 1981). However, Mansfield (1984) observed densities as
high as 21 larvae/m3 in the Little Pigeon Creek wetland.
Pentwater Marsh may not be as significant a producer of
largemouth bass, yellow perch, gizzard shad, alewife, and
black crappie as other wetland systems (Kindschi 1979;
Mansfield 1984). However, incoming data from subsequent
field seasons suggests production of these species may be
much higher in more favorable years (Chubb and Liston 1984).
Pentwater Marsh northern pike production may have been
lower in 1982, due to a cold spell and water level drop
during early development. Pentwater Marsh had an estimated
4,000 northern pike fingerlings per hectere at the end of
June, 1982 (Table 19). Most values in the literature were
between 500 and 1000 fingerlings/HA and dealt with small
inland lakes (Fago 1977; Royer 1971). McCarraher (1957)
estimated 1,215 fingerlings/HA for a small Nebraska lake
while Marlean (1976) estimated 87 northern pike fry/HA for a
series of coastal Lake Erie wetlands. Marean's estimates
are low by his own admission, perhaps due to inadequate
sampling intensity. Estimates of young-of-the-year standing
crop at the end of the season were close to 100 northern
pike/HA (Jaworski and Raphael 1978; Mann 1980). Pentwater
Marsh leads in northern pike production partially due to
measurements taken at an earlier developmental stage.
However, the methods of collection may have underestimated

larval abundance due to high gear avoidance and the

154

congregation of larvae within the less efficiently sampled
shallow—water emergents.

Most studies found in the literature involved inland
marshes at least double the size of the Pentwater Marsh.
Marean (1976) suggested smaller wetlands are proportionately
more productive. Small wetlands, such as Pentwater Marsh,
certainly offer a greater proportion of shallow-water
habitats and vegetative edge which seemed to be particularly
important to northern pike (Table 1; Table 22; Appendix
A.3). In fact, Pentwater Marsh may be an underutilized
resource operating below its full fisheries potential. For
example, the Michigan Department of Natural Resources
recommends northern pike stocking rates of 68 fingerlings/HA
of open-water lake habitat (Jaworski and Raphael 1978).
Assuming that the majority of northern pike eventually move
downstream, the marsh could thus support approximately 222
northern pike/HA, a level substantially higher than the
recommended stocking rate of the DNR. As mentioned earlier,
however, the interplay of numerous factors including food
availability, water levels, and temperature may conspire to
substantially reduce northern pike production by the end of
the season.

Northern pike mortality was estimated at 962 from April
hatching to fingerling stage in late June. Most values in
the literature approach 99% mortality for northern pike
(Royer 1971; Fago 1977) as do those for other species

(Pendleton and Copeland 1979). According to Dan Brazo

155

(personal communication) a number of adult fishes, including
larger northern pike, were consuming fingerlings in high
numbers. Also cannibalism may be a common occurrence,
particularly when fish densities are high and food resources
limiting (Chevalier 1973). However, it is important to
remember that larval mortality, although a loss to the
species, may represent a significant energy pathway between
the trophic levels of the marsh. Larval mortality is one of
the catalysts which drive the high production so

characteristic of the wetland system.

CONCLUSIONS

 

Pentwater Marsh compares favorably to other aquatic
habitats in terms of the abundance, diversity, and
survivorship of larval fishes. Pentwater Marsh supports
substantial densities of larval carp, gizzard shad, various
cyprinids, yellow perch, pumpkinseed sunfish, and northern
pike. As compared to other systems, Pentwater Marsh
excelled in carp and northern pike production. For most
species, highest densities occurred in the shallow-water,
densely vegetated, bayous of the marsh. However, there was
substantial evidence of both diel and seasonal movements
between the marsh shallows and the deep-water bayou-mouths.
Larval abundance and distribution appear to be related to a
number of inter—correlated factors including vegetation
quality, water depths, dissolved oxygen, and temperature.

Pentwater Marsh may be particularly supportive of high

156
larval fish production due to its small size, high

interspersion of vegetation types, and diversity of
habitats.

However, the marsh may not be as significant a nursery
area for Great Lakes fishes as anticipated. White suckers
may use the marsh as adults, but were not found in high
densities as larvae or juveniles. Alewife production,
although high, occurred primarily in Pentwater Lake and not
within the marsh itself. Cyprinid exports may be
substantial but more information is needed for complete
assessment. Carp larvae may be the most significant export
from the marsh, although imports from seiche activity could
balance drift output.

It is unclear why Pentwater Marsh should support mainly
residential or inland species. Perhaps, the configuration
of the marsh to Pentwater Lake and Lake Michigan is less
attractive to Great Lakes fishes than other coastal
wetlands. However, there are a number of Lake Michigan
drowned river-mouth marshes which resemble the configuration
of Lake Pentwater and the Pentwater Marsh. Comparable
studies in other systems are crucial as is a more integrated
approach among the various research groups.

Certainly, additional work with larval and particularly
juvenile drift is necessary to accurately define the
interrelationship Of marsh and lake. Further years of study
may uncover species compositions, abundance, and mortality

values differing from those observed during 1982. Fish

157

production and year-class strength may fluctuate greatly
from year to year (Franklin and Smith 1963; Jude et al.
1981). In fact, preliminary work in 1983 and 1984 suggest
largemouth bass, pumpkinseed sunfish, and northern pike may
be much more substantial components of the larval fish
community during more favorable years. Pentwater Marsh is a
truly coastal wetland in that it undergoes cycles associated
with Great Lakes water levels. Our observations only
represent the rising water-level phase and may not be a
complete representation of the long-term marsh community .
As suggested by Weller (1978) among others, vegetational
and nutrient response may differ greatly between regimes of
lowering and increasing water depths. As shown in this
study, vegetation structure and diversity can directly and
immediately impact larval fish distribution, abundance, and
species composition. Indirect effects of nutrient cycling
and vegetational response include alterations in the
zooplankton and invertebrate populations on which the fish
depend.

This study was designed under the Michigan Sea Grant
coastal subprogram and began with goals that included an
integrated and interdisciplinary approach with multiple
years of analysis. Unfortunately, budgetary considerations
within Michigan Sea Grant led to the premature demise of the
wetlands subprogram. Hopefully, this action does not
reflect an overall decrease in wetland interest and

research. As suggested in this analysis, much work is still

158

to be done. Exploration of fisheries values is timely
considering the loss of 8,097 HA of Great Lakes wetlands
per year. And if the remaining 42,530 HA of coastal
wetlands remotely resembles the Pentwater Marsh, the
potential loss of valuable fisheries habitat is indeed

sobering.

1)

SUMMARY

Pentwater Marsh, a coastal wetland on Lake
Michigan, was studied as a spawning and nursery area
for fishes. A total of 562 larval fish samples were
collected from March through August of 1982. Sampling
was weekly during May and June and bi—weekly during
the rest of the season. Marsh channels were sampled
with a total of 198 1 m conical (363 u) push-net tows
taken through the season. Sampling effort was
concentrated in the shallow—water bayous with a total
of 250 drop-net, 76 push-net, and 28 pull-net samples
completed. The drop—net was developed specifically for
the shallow-water, densely vegetated bayous and
consisted of a simple meter-box frame with 363 u mesh
sides of nitex material. The net was thrown into
targeted areas according to a stratified sampling
regime within bayous and vegetation types. All
vegetation was removed and rinsed to dislodge clinging
eggs and larvae. The contents of the net were strained
with a meter conical dip-net (363 u mesh),
concentrated, and preserved. The average drop-net

3

sampled only 0.4 m while channel push-nets covered an

average of 5.7 m3. Night sampling received

highest priority with day series included monthly

159

2)

3)

160

for diel comparisons.

Studies of larval fishes in wetland habitats are
scarce, largely due to the lack of appropriate sampling
techniques. The drop-net was developed and tested for
use in the densely vegetated shallow-water of the marsh
bayous. The drop-net was judged of adequate efficiency
for quantitative estimates of larval fish densities.
Average drop—net efficiencies were estimated at 851 2%
and 6OI'3Z retrieval for larval and juvenile stages,
respectively. Recommendations include judicious use of
the technique for species of demersal habitats,
extremely heterogeneous distribution, or high mobility.
In many respects, the drop-net may be less biased than
the more conventional technique of push-net sampling.
However, the drop-net may be less efficient, and
consequently, underestimate larval fish densities in

very shallow water (less than 30 cm in depth).

Gill-nets and trap-nets set in the marsh
bayou-mouths indicated that white suckers, northern
pike, and yellow perch were major marsh spawners from
April through May. cyprinids, black crappie, and
gizzard shad were identified as late-spring spawners.
Brown bullhead, carp, and alewife were observed in

spawning condition through late summer.

4)

5)

6)

161

A total of 3,926 larval fish were collected in the
marsh during the 1982 sample season. An additional
389 larvae were found in collections of drift and lake
samples. Carp dominated the ichthyoplankton with a
total of 3,010 larvae identified. Carp, gizzard shad,
other cyprinids, yellow perch, and pumpkinseed sunfish

comprised approximately 95% of the larval catch.

Peak larval fish densities were attained twice,
first in late May and later in June. Major early
spring larvae included yellow perch, gizzard shad, and
cyprinids at peak densities of 6.51 2.2, 3.81 0.03,
and 4.72 2.2 larvae/m3, respectively. The late spring
peak was represented by primarily carp and pumpkinseed
sunfish. Alewife larvae, although present throughout
the remainder of the summer, were not found in high

densities as expected.

Peak larval fish densities of 63.53 90.7 and 28.41
7.6 larvae/m3 were estimated in the shallow-water
bayous and bayou-mouths. These values were
substantially higher than the values in the literature
for the marine estuaries, but were comparable to values
for other freshwater coastal systems. Peak channel
densities of 3.531 1.52 larvae/m3 were also high
relative to most riverine or lacustrine systems.

Larval fish were present in the marsh at densities

7)

8)

9)

162

ten-times that of nearby Lake Michigan.

Larval diversity was lower in the Pentwater Marsh
than in most estuarine and freshwater marsh systems.
The predominance of carp, as well as latitudinal
differences, were offered as explanations for this

discrepancy.

In general, larval fish densities were greater by
night than by day. Although reduced gear efficiency
may be a contributing factor, larvae may exhibit diel
migrations across marsh habitats or regions. Carp and
other cyprinids appeared to favor shallow-water
emergent vegetation by night, with dispersal to
deep-water by day. Yellow perch densities increased
in the bayous and decreased in the channels by day,
perhaps suggesting the reversed diel movement between

habitats.

Temporal successions in distribution were also
apparent. Larvae of early-spawned species such as the
yellow perch, black crappie, northern pike, and brook
silverside were first collected in the upstream areas
with later peaks in abundance in the lower marsh.

Based on larval size distributions, these patterns were
largely the result of delayed spawning activity and/or

slower development in the cooler waters of the lower

10)

163
marsh. Active downstream movements, although
documented for a number of species, were not observed
but may have occurred at later stages in development.
Mesolarval cyprinids, pumpkinseed sunfish, and yellow
perch appeared to shift from emergent to submergent
vegetation and from shallow to deeper water within the
marsh bayous. These species were found in highest
densities within submergent vegetation. Larval carp
and northern pike were in greatest abundance in the
shallow-water emergents and no deep-water movements
were apparent. In general, deep-water movements may
have been reflected in the declining diversity of the
shallow-water bayous and increasing diversity of the

lower marsh.

Physical, chemical, and habitat parameters were
measured in conjunction with larval fish abundance and
occurrence. Both precipitation and marsh discharge
peaked in early April and rose again in August. Marsh
water levels peaked in late April, declined through
May, and rose again in late July. Marsh water
temperatures increased from 20 C in April to 300 C as
measured in early August. The shallow littoral bayous
were generally warmer than channel waters by several
degrees and experienced the greatest diel fluctuations.

Dissolved oxygen levels were partially related to

temperature and also exhibited the greatest

11)

164

fluctuations in the shallow-water bayous. Dissolved
oxygen levels ranged from 1.3 to 13.9 mg/l with lowest
values encountered at night and in submergent
vegetation. Measurements of turbidity and pH proved
inaccurate and of little value in this analysis. As
expected, pH appeared to be related to vegetation
photosynthesis and may thus be of potential importance

in the densely vegetated bayous of the Pentwater Marsh.

Spearman-rank correlations run on data sets
taken during peak larval abundance showed larval
density was significantly related to temperature,
dissolved oxygen, water depth, and vegetative
qualities. Water temperature was instrumental in
determining the timing and locality of initial spawning
as observed in adult behavior and resulting larval
distributions. A severe drop in temperature in mid-
April may have adversely affected northern pike
production and year-class strength. Yellow perch and
carp densities were correlated with water temperature
whereas other cyprinids were associated with cooler
water.

A general pattern of extreme variation in habitat
preferences and requirements of larval fish species was
observed. Northern pike larvae were associated with
high dissolved oxygen levels. However, carp larvae

were found in sites of particulary low dissolved

12)

165

oxygen. Although turbidity may be deleterious to
larval fishes, only pumpkinseed sunfish were negatively
correlated with turbidity measurements. Northern pike,
cyprinids, and yellow perch were associated with high
turbidity, perhaps as a secondary effect of their
preference for emergent vegetation. Likewise, yellow
perch were associated with deeper water, whereas carp
were negatively correlated with sample depths.
Vegetation type, diversity, and structure were
important in determining larval fish abundance and
distribution. Percent vegetative cover was not as
significant a factor as the type of vegetation.
Vegetative interspersion, particularly between
emergents and other vegetative types, was hypothesized

as of utmost importance.

A number of larval fish species were found in
association with each other. Cyprinids were
associated with carp, yellow perch, northern pike, and
pumkinseed sunfish. Yellow perch and cyprinids were
also associated but probably through similarities of
environmental requirements rather than direct
interactions. Only carp and pumkinseed sunfish were
disassociated with carp largely confined to the
emergent zone and pumpkinseed sunfish primarily in
submergent vegetation. In general, species

associations were indirect involving habitat

13)

14)

166

preferences rather than direct interactions.

Of the 18 fish species utilizing the Pentwater
Marsh as a spawning and nursery area, only seven
species were considered transients. Larval cyprinids,
black crappie, gizzard shad, and northern pike were
likely involved in local migrations between the marsh
and Pentwater Lake. However, evidence suggests only
carp, alewife, and white suckers were Great Lakes
migrants. White suckers were not major users of the
marsh habitat as larvae or juveniles. Alewife larvae
were concentrated at the marsh outlet and in Pentwater
Lake. Drift samples suggest alewife were transported
from lake to marsh through seiche activity. Carp
larvae were ubiquitous throughout the marsh, and
protolarvae were passively transported back and forth
in the marsh drift. Carp exports were substantial on
some days; however, carp inputs may balance the
drift outputs. Further drift sampling is necessary to

elaborate on these patterns.

When compared to other habitats and wetland
studies, Pentwater Marsh appears to be a highly
productive system particulary for carp, northern pike,
pumpkinseed sunfish, and various cyprinids. Peak
standing crops were estimated at 3 million carp and

54,000 northern pike larvae per hectare of bayou

15)

167

habitat. Largemouth bass, yellow perch, gizzard shad,
alewife, and black crappie were present in lower
abundance than expected. However, these species may be

much more successful during more favorable years.

The Pentwater Marsh, although with obvious unique
features, may illustrate some of the qualities common
to other freshwater wetlands of the Great Lakes. Not
surprisingly, freshwater coastal wetlands resemble
marine estuarine systems. 'They harbor high densities
of larval fish and may export a few species in high
numbers. Although the Pentwater Marsh configuration
may somewhat decrease interactions with Lake Michigan,
the marsh's potential as a spawning and nursery area is
immense. Further study is needed, particularly to
explore the connection of lake and marsh, to determine
the magnitude of year to year fluctuations, and to

compare the marsh with other freshwater wetlands.

LITERATURE CITED

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APPENDICES

APPENDIX A

Environmental parameters (meaniSE)
as measured across major regions, bayous, vegetation types,
and channel stations of
the Pentwater Marsh during the 1982 sample season

1536

 

 

 

 

 

 

 

 

 

 

N.H+o.n so.o+se.o H.o+N.N N.o+n.c o.N+o.N N.o+m.nN o.o+N.e No.o+oe.o H.owm.o H.Hmw.N N.Hmw.o H.omN.NN oN-N
H H. :H. H. H H H H 0.0Hh.s 0.0H0.0 0.0H0.o 0.0H0.c~ nus
N.o+o.n so.o+ne.o H.o+e.N N.o+H.o m.N+o.w mo.o+o.oH e.oHN.N so.owan.o H.cHN.N o.oHH.N n.NHm.o H.oHN.NH NNuo
. u u u u s <.o+o.n «c.o+sn.o N.onm.N H.mwo.e o.N+N.N n.o+n.nH N.@
In H In H H u H u o.owm.N o.owc.e o.o«N.HH o.ona.NH Hue
N.owm.n no.onxs.o N.owm.N c.nuk.o N.n+N.oH NH.oHH.sH o.o+o.n so.o+Hs.o N.o+n.m H.H+n.n o.NNw.cH e.oud.oH nNnn
«.H+e.s No.o+mn.o H.o+o.N c.o+o.n . n.o+n.oH u .n - u u - NH-n
. - u u n . o.o+o.m o.o+oH.o . u . o.o«o.s nHue
.NH H-H Hayzv HHHN-H Ho H .NH .20 Haazv HH\N-H Ho 0
sou.wo> lemon 2: HuHquush on mayP. >oo.mo> gamma :0 HquHpush 00 amok ouan
Han HHNHH I.
2 aoHen
o.o«o.n so.o«mn.o H.o«o.N n..«n.¢ H.n«w.o H.oaH.nN H.H«m.n no.o«Nn.o n.o«n.o o.H«o.o n.H«n.< N.o«o.cN oNuN
- u - u - - r r o.o«H.N o.owo.s o.o«n.o c.o.o.NN NIH.
A.H«o.n Ho.o«N<.o N.o«s.N N.o«H.c o.o«a.o o.o«o.oH s.o«2.n no.o«NN.o H.o«N.N N.N«o.HH c.N«o.n H.o«N.NH NN-o
- - u n . u u u u o.o«N.N c.o.o.N o.o«m.oH o.o«o.oH one
H.H+o.m Ho.o«NN.o N.o«H.N n.o«o.o u H.o«N..H m.o«n.o No.oNNN.o H.o«H.N N.H«o.n o.N«N.n N.o«o.nH H-»
o.o+a.N No.o«on.o H.o«m.N N.oNH.a n.N«m.oH o.o«o..H . u u .u u - nNun
c.H«o.n Ho.c«nN.o H.oNo.N c.HNo.n N.N«N.o N.oNN.2H . u u u u . NHum
. - u n n . o.o«o.N o.o«oH.o - u . o.o«o.n nHus
.NH Hue HHHzH HHHNac HooH HNH Hue Haazv HHHN-H HuoH
>00.no> Human =m Huuanush on aloe 2 poo.mo> sumo: mm Huuvaausa 0: much sump
Hon acqu
H =02<2
H.me.n no.oHNn.o m.oun.o o.HHo.o N.HHN.. m.owo.eN u u o.omH.N o.oMe.s o.oHH.n o.oMo.sN oN-N
n n o.oHH.N o.oHo.s o.oun.o o.owo.mN o.H+s.e No.o+He.o H.own.N «.Nwo.o o.NMN.n 2.owo.mN N-N
s.on.n no.oHNN.o H.oHN.N N.NH0.HH o.NHo.m H.oHN.NH n n o.oHo.N o.ouc.o n o.o+o.mH NNuo
m.c+n.o No.o+NN.o H.o+H.N N.H+e.n o.N+N.n N.o+o.mH o.HHN.N no.0Hmm.o H.oMH.N o.mHH.oH N.an.o o.owo.NH Hue
. u u u n . o.HHo.n so.owos.o 2.o+q.N N.N+o.a N.H+o.q n.o+o.oH NHun
- - - u - u e.H+n.n No.o+mn.o . u . o.c«o.. "H's
.NH .5 2:5 3...: 8.. H: H... 3:: 3...; Go.
.oo.wo> Hague 2H HuHsHstse on Hawk .oo.Nu> 2uaoa 2. HuHeHstss on asap uuua
Han HHNHz
N soNHN

 

 

 

.2. H0 N as.

.3 .H

.u n:o»mn :H Osman Hp can Hoe Ha eonsnmma no Hmmflemoav sumac-mum: Hmueoseouwsem

.eomoom onamm ~00H oz» wcwusv some: Noamxunom
.N.¢ uHucoNNH

1E37

 

 

 

 

 

 

 

 

 

 

 

I I no.o«n.N o.o«o.n G.N«o.N m.ofln.oN I u H.o«o.N o.oum.n N.NHN.N n.o«N.NN oNIN
I I I I I I I m H.o«o.N ¢.o«N.n N.n«n.o n.owo.NN NIH
I I N.o«n.H o.o«N.o H.2«N.oH e.oNN.NH I w H.o«N.N n.o«o.c o.s«o.nH ..o«s.oH NNIo
I I I I I I I u H.o«N.N n.o«n.N o.e«n.o H.oHN.NH oIo
I I H.o«N.N n.o«o.c s.s«o.o H.o«N..H I I I w I H.o«N.eH nNIn
I I H.o«2.N H.o«o.n 4.N«n.N N.o«o.oH I I H.o«o.N n.e«n.e s.q«o.o o.oun.oH NHIn
HNH Hue Haazv HHHN-H HooH HNH H-v Haszc .HHNAH Hoe.
>00.uo>. canon an HquHaumMF on name soo.uo> canon mm Huuvuaush 00 Aloe mama
Hon uauNz
mHu22<mo
I I N.o+n.N n.0nw.N N.o«N.o N.o«N.NN I I H.o«d.N n.H«H.o o.N«c.N N.owa.NN oNIN
I I n. I I I I I H63; «63:: his; 2.322 NIN
I I o.o+m.N o.o«a.e o..«~.oH o.o«a.NH I I H.o«N.N N.H«m.N o.s«N.o N.o«a.NH NNIo
I I I I I I I I flown; N.o«a.N 22.2.6 2.3.2 To
I I H H H u I I H.o+o.N N.nnN.HH o.nflq.o o.ome.NH HIo
I I n.o+N.m m.o+o.n N.n+2.nH o.o+o.nH I I I I I H.o+o.nH nNIn.
HNH H-H H2920 HHHN-H HooV HNH Hue Haazv HHHN-v Ho 0
.oo...» Hague as HquHataa on anus .oo.uos 2uaoa as HuHaHstaa on Hump ouon
Hun .22.:
mueaozIHoN<n
H H H H H I I «0.0H0<.0 I n.~flw.h 0.~flw.n. c.0fln.e~ nIm
H.H+n.n no.o+Hs.o H.o+o.N N.o+n.s o.N+H.N N.omu.NN No.oflo.n No.oflon.o N.H«N.o N.HNN.o n.HNH.n e.o«w.mN oNIN
H H H H I I s.0fl0.< ~0.0flmn.0 H.0MN.H n.HM0.0 s.HMw.n n.0fiq.mu sIh
H.o+o.n .o.o+ns.o H.o+n.N o.H+n.o H.nfla.o o.ofio.HH ..oNN.n no.ownn.o H.o+N.N H.N+n.o n.H+n.m H.o««.NH NNIo
u n u I I I n.o«o.m No.oasn.o N.oNn.N H.0«N.NN o.N«o.o H.o«..nH NIH
H.Hwo.n Ho.oHoN.o N.o+H.N o.ofla.o I N.ofiN.sH N.o«o.n No.oNoN.o H.o«o.N 4.H«o.a N.H«..n N.o«N.oH HIo
..owm.n no.oHNs.o H.omN.N N.HMN.N o..Mo.oH n.omN.nH o.ofle.n no.o«nm.o N.o«H.N H.H«N.o n.n«N.o n.oNo.nH “NIn
o.H+o.q eo.o+on.o H.o+N.N N.o+H.m n.H+H.o n.o+m.NH oN.omN.n Ho.om°..o H.o««.N o.N«o.a n.o«2.s H.oMo.aH NHIn
I I I I I I N.H+o.n oo.o+.N.o I I I N.o+o.c «HI.
HNH Hue Hsszv HHHN-H H000 HNV H-H Hsszv HHHN-H Hoov
sou.mob Human mm HunHoush on much soo.0o> Human mm HquHnush 00 snow cum:
on .2NH2 II

 

m00»<n mmh<3Iuoqq<zm

 

 

.conoou oHaaoa NmoH 0:» ucHusv some: nouwrucom on» no aHoecosu Lupus can .mcusoaIsonaa
.naonon nuum3I30HHmno eH uzwua H» can Hoe Ha couscous no Hum+euolv cacao-mum: Hmumoaeouasum

.H.< uHuaoHHH

1538

 

 

 

 

I I ,H H H H I No.o«do.o I n.N«w.N o.N«n.n 2.0«m.sN NIN
I I o.o+N.N o.o+s.N o.o+N.e o.o+o.sN I I o.oflH.N o.o«o.e o.o«w.m o.o«c.eN oNIN
I I H u n H o.HflH.n no.o«NN.o H.o«N.N n.o«H.o o.N«N.n e.o«n.eN NIN
I I o.o+2.N o.o+e.n o.o+o.oH o.o+o.NH I I o.o«c.m o.o«N.o o.o«N.oH o.o«a.NH NNIo
I I I I I I o.o«w.e No.oNNN.o H.0NN.N N.oNH.nH H.2«N.o N.o«w.oH oIo
u H II n I I I I o.oNa.N o.o«H.o o.o«o.oH o.o«c.NH HIo
oN.o+m.e No.o+HN.c H.o+m.N n.n+o.m n.nflN.oH n.oflo.oH N.oHN.m No.onN.o N.on.N <.H«o.o m.nwn.m o.o«d.nH nNIn
I I I I I I o.o«d.N o.o«oH.o I I I o.o«o.n «HI.

.NH Ha. Hasze HH\N-H Hoes HNH Ha. Haazv HH\N-H H000
.oo.uo> guano =2 HuHeHstaa on asap .oo.mo> 2uaon =2 HHHaHstsa on Haas anon

.ua “.NH:
N =oH<m

 

Hv.ueouv ~.< waveumm<

1E39

 

 

 

 

 

 

 

 

 

 

 

 

I u I I 66.6«N¢.6 I 6.H«6.N N.6«6.6 n.6«N.6N NIN
6. N+n.m 6. N+66. 6 H. 6+6. N 6. H+N. 6 6.6+n.6 n.666.mN 6.6NN.6 66.6N6N.6 H.6«N.6 6.H«6.N 6.N«6.6 N.6«w.6N 6NIN
H u u H.H«.N.N 66.6.6666 H.6«1N 1N3... Namnfi 16m66N NIN
n. Hm“. N 66. own“. 6 H. 6m“. N H. 6mH. 6 H.N+6.6H H6.6w6.NH 6.6mN.N 66.6mwn.6 N.6«N.N 6.6«N.N N. N+6. 6 N.6+N.NH NNI6
6. 6+I6. 6 8.326 66HN.N 66....66 H- 6.6.+I6.6H N.HH6.6 N66HNN6 H.6N.N.N 6.HN.N.N 6. $1... 6.63.3 6I6
6. 6+6. 6 66.6+e..6 H.6+6.N H.H+N.6 N.n+Hu6 n.6+n.nH H.H+N.6 “6.6+nm.6 n.6m6.N N.HmN.6 6. HHms. HH 6.6»N.NH 6NIN
1 H n. 6 66.6NNN.6 6H.6NN.N 6.666.n 6.N««.n n.6NN.NH N.6NN.6 6H.6NH6.6 H.6+N.N N.H+6.6 N. N+N.6 N.6»n.6H NHIn
I I I I I I 6.6+N.6 6.6+NN.6 I I I 6.6+N.n NHI6
HNH H66 H6926 HHNNIH H666 HNH H66 H6626 HHNN-H H666
popuuo> 0660: mm Huneunush mnI amok pou.um> £060: HuuvumuahI on mask can:
N66 62 H2
66266662666
.II I I I I I 6. 6«N. N 86316 .I. 66.3.6 N63. 6 6.6.3.2 NIN
N636 8.3.616 16.....1N N6HN.N 6.3.16 13.12 6. 66.16 66.6616 166.16 6.NNN.6 6.1.6. N 16......3 6NIN
H u I I I I 6. 66. N N66NNN6 16NN.N N.HNN.N 6.2.16 163.2 NIN
6.6+N.N 66.6+66.6 N.6««.N n.N«¢.N 6.N66.6H 6.6«6.NH N. cum .6 66.6«6n.6 1 6N6. N 6. nNN. NH 6. Nua. m N.6«n.NH NNIm
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APPENDIX B

Mean larval fish densities (mean #lmgl; SE)
as measured across major regions, bayous, vegetation types,
and channel stations of
the Pentwater Marsh during the 1982 sample season.

1592

 

 

 

 

 

 

 

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I I u I . I I 0.0 00.0 I 0.0 «0.0 0.0 m0.0 00I0
I I 0.00 +08 I 00.00 000.0 I m. Hmé I I 0.0 +m.0 «Tm
00000 0000000 000000 0000 00000 0000000 000000000 0000 0000 00000 0000
00000 022000 00000002 300000 0000000
000
00200000000
I I I I I I I I I 0.0 0I0
I w I I I 0.0 00.0 I I 0.0000.00 0.00flN.00 00I0
I 0.0 +0.0 I I n I I I 0.0 «0.0 0.0 «0.0 0I0
I I I u 0.0 +0.0 u 0.0 M0.0 I 0.0 00.00 0.0 «0.00 00I0
I I I 0.0 +0.0 I 0.0 +0.00 0.0 +0.00 I 0.00M0.00 00m0.000 0I0
I I I I n I I I 0.0 +0.00 0.0H0.00 0I0
I I I u 0.0 +0.0 I I I I 0.0 ”0.0 00I0
I I I 0.0 +0.0 I I I I I 0.0 +0.0 00I0
00000 0000000 000000 0000 00000 0000000 000200000 0000 0000 00000 0000
00000 022000 20000002 300000 0000000
00002
00200000000
I I I I I I I I n I0.0 0~I0
I I I I I I I I 0.0 ”0.0 0.0 ”0.0 00I0
I I I I I I n I 0.0 ”0.00 0.0 ”0.00 0I0
I I I I I I 0.0 +0.0 I 0.0 +0.0 0.0 +0.0 00I0
I I I I I I I I I 0.0 00I0
00000 0000000 000000 0000 00000 0000000 000200000 0000 0000 00000 0000
00000 002000 00000002 300000 0000000
000

m<mqlozuh<04m

 

“v.0:00v n.m uuvcoqn<

1599

 

 

 

 

 

 

I ‘ - - - - I - . o.o o~-~
no.owno.o . - n - - u u u no.0«no.o u-“
~.o +~.o - - - u - u . ~.o Ho.o N.c «w.o --o
no.oflno.o - - - - u . n.o «a.o ".o «o.c . n.o no." w-o
No.o«~o.o no.ofiso.o . . ~.o «n.o ~o.o«~o.o so.o«oo.o - n.o «o.o n.o um.” «Nun
no.ofino.c c.ofle.o . - ~.o «o.o - u u - ~.o «o.o «Mnn

«mayo mHmm<mo umpu<a muHm moamm mHzomug mnHszm»u a‘mm m~<o 4<eoa ouun
uu<gu »zz=on zamaamoz soJAN» a~<NNHo
amqu
=oz<~n zaaom

- u - - - u u - . o.o ow-“

- u u . no.ofino.o - u u . no.o«no.o -uo

. n u - no.o«no.o . - u - no.oano.o m~-n

- n - - - - u - . o.o Nfi-n

gumbo mumm<mo ~m-<a uaHm momma meommg maHzHam»u a<=w m~<o g<eoa opus
uu<4n uzzmow zgmmpmoz zoqqmy =a<NNHo
~<a
=Uz<¢n zygoz
- - - . oo.o«~o.o . Ho.o«~o.o - oo.o«mo.o an-“
- - - - - - - - no.o«mo.o co.o««o.o 5-5
- . «o.oflho.o - - - u - ~.o «m.o n.o «o.o --o
- - - - u - - n.o no." n.o «o._ m-o
. no.0fimo.o . - - - u - ~.o «n.o no.o «m.o n~-n
- - - - - n - - . o.o Ngnn
«mzho mHmm<zu =m~x<a muHm :Ummm mHzommg mnHzHum»u n<=m mu<u 4<eoa cyan
uo¢qm ~zz=ou zxmzexoz :oqqu» au‘NNHu
smon

:Uz<mm memo:

 

.zucoun :uuoc ecu :« unwac up was saw us vvusmwme no Amm + mux‘ cuuav nowuaucov gnaw Hupuou new:

.comcwa oaaamu ~mo~ as» wcuusv nauoz unuorucom ecu no mauccozu can: vac .zucuua nuaou

.e.m navaunn<

200

 

 

I I I I I I o~.oflo~.c o~.oflo~.o ole

 

 

 

 

I no.0nno.o I I I I I “.0 «h.c no.ouno.o ~.o «~.o «NIo
I I I I <o.o«<o.o I No.o«~o.o I ~o.o«~o. no.o «oo.o mNIn
I I I no.0«wo.o I I I I I no.o«no.o NfiIn
«mmeo ummm<uu ~m-<a muum momma mHzomuq maHzHumuu n<=m mu<u g<soa ouua
uu<qn uzzuon zumzpaoz soggmu n~<NNHo
”<9
guzz‘au z~<x
I ~o.oflfio.o I I I ~.o «N.o I I N~.o«n~.o H.o «n.o oNIu
I mo.o«oo.o I I I I I co.o«no.o n.o «n.o n.o «o.o “Is
no.omoo.o no.oMnc.o u I I I I ~.o m~.o -.o m..o ".o Ho.o -Io
mo.o+oo.o ~.o+~.o no.owmo.o I I I I no.o +~.o ~.~ +~.m ~.~ +0.» mIo
I I no.o+mo.o I I I I I I oo.oflno.o -In
mango u~mm<xo mmpm<n muHm momma meommq mnHzHumyo a<mm mu<u g<aoa can;
uo<an yzzzon zxmzeaoz noggu» a~<NNHo
aonz
guzz<=o zH<x
I I I I I I I oo.o+oo.o I oo.o+oo.o oNIs
I I I I I oo.o+no.o I I I oo.o+no.o NNIo
I I I I oo.o+o~.o I ~.o +~.o I I ~.o +n.o nNIn
I I I I eo.o+o_.o I I I I oo.o+o_.o N_Im
ammeo mHmm<xu mm?m<n mme momma mHzommg maHszm»u a<=m m~<u g<pop can:
uo<qm »zz=on zmmxexoz madam» au<NNHo
uco

=Uz<xm =H:Om

Av.u=ouV <.m uwvcoaa<

201

 

 

 

 

 

 

I I I I I wo.ofi-.o I I ~.o«~.o ~.o «n.o oNIn
H I u I I I I I No.ofl~o.o No.o«~o.o “I“
o~.oH~_.o I No.oH~o.o I I I u n _.o Ho.o ~.o «m.o NNIe
mo.o+h~.o I ~o.ow~o.o I u I No.o+~o.o mo.o+mo.o o.~ «e.~ ~._ «o.~ on
u u ".o +m.o I ~.o Hm.o go.oflfio.o _o.oHHo.o I ~.o H~._ m.o «o.~ mNIm
oo.o+~o.o w#.o+h_.o I I eo.o+oo.o I I I I «.0 «~.o NdIm
mmmpo mHmm<mo mmpm<n muHm momma meommq mnHszmyu a<=w mm<o q<aoa ouaa
uu<gm »zz=ow zmm=Fmoz soggm» am<NNHo
aonz
guzz<=o moum
I I I I I n I I so.o«no.o so.ofi~o.o cm.“
I I I I u eo.o+¢o.o n n.o Hm.o I m.o «m.o «NIo
I I I I ac.owoo.o I eo.o+<o.o I co.o«eo.o so.om¢~.o mNIn
I I I I «o.o+oo.o I I I I <o.o+oo.o NHIm
mazes wumm<mu mmpm<a mxum momma mHzommg maHszm»u a<=m mm<u 4<woa sumo
uo<4m >zz=on zxmzymoz :oggm» am<N~Hu
><e
qwzz<=u aHz
~o.ow~o.o I I I I «c.0qu.o I I Ho.o«~o.o «c.0aoo.o ONIN
mo.o+mo.o I u I I I I mo.ofimo.o ~.o Hm.o n.o «q.o NIN
I I No.0HNo.o I I I I ".o H~.o ~.o «q.o d.o «m.o -Io
I H No.oHNo.o I H u n I m.~ Ho.n 0." flo.n mIo
I «o.o+¢o.o mo.owmo.o II mo.owho.o No.o+mo.o mo.o+mo.o «o.oH~o.o «.o H~.o e.o «o.~ «NIn
I I ".0 +~.o «o.o+¢o.o mo.o+qo.o I I I I ~o.o«o_.o NflIn
mmmpo Mamm<mu mmpm<a mxum zommm mHzommg maHszm»u n<=m mm<o q<poe ouon
uu<4m »zz=oa 2mmzyuoz noggm» am<N~Hu
eonz

mfloccwzu

wvwm van was um ucwwc an van sat up amusmmme mm Amm fl

qmzz<zu aw:

.commwm vaqemm ~wo~ ecu wcwusv gaunt uuchucom ozu uo
.m.m xfivcoaa<

m

a\§ :moav mkuwmcmv swam Hw>umH can:

202

 

 

 

I I H I I I I do.ofldo.o I ~0.0fi§o.o owls

I No.o+No.o I No.0fluo.o I H I No.oHNo.o no.o+oo.o NNIc

I I I I no.0Hmo.o I ~o.o+~o.o I No.o+co.o no.0Ho~.o nNIn

I I I I No.o+No.o I I I I ~0.oH~o.o len

mmzho Mumm<mo mMH¢<a mama momma mHzommq maHszmwo n<=w mm<u A<HOH can:
uo<qn wzz=OH zmmmhmOZ 3044a» nm<NNHo

H<a
qwzz<=u mnmm

 

 

Au.u=ouV m.» auucogg<

APPENDIX C

Mann-Whitney-U and Kruskal-Wallis test statistics
as calculated for differences in larval fish densities
across regions and stations of the Pentwater Marsh.

203

 

 

 

 

 

o.~ C.NH o.n~ n.~ «.0 m.mn m.~ N.< o.an ONIN
I I I I I I n.N h.~ n.on hlh
m.n n.c o.~ m.e «.0 I o.~ GIN o.o NNIo
I I I I I I ~.n o.» o.~ mlo
o.~ n.- n." o.n I I o.n I o.nN filo
o.oN o.oN o.m~ o.n n.~ QIn n.u n.o n.c~ nNIn
n.w hon noN~ D D Lu I l I Nuln
Hzmummxmam m<NAquHh<oqm quummzm Am.z Az.m.zv AN.3.».uv Am.z.mv A:.m.2v AN.w.3.NV uh<a
our—uh .3: EEE EDIE—.8:
Prom: .05 ucn h<n Hmomz
mzomuu<mxoo Hmuh onH<Hw
0.0mm C.MN o.m- o.n~ o.mm o.oN m.n~ c.0n o.n ONIN
I I I I I I n.~n 0.0 o.» «In
C n.0H o.- m.¢n n.0N o o.wc o.on n.h~ NNIo
I I I I I I Q." o.N o.o on
I I o.~¢ I I I I I C.MQ “Io
n.@ o C.NON o.n~ o.wn o.o~ 0.0— 0.0» n.- mNIm
D.MHw I m.oc I m.oo I I I I NHIm
szz<=o Amzz<=o 29:0:Iaoucm qmzz<=u Amzz<=u ahaozlbow<m uh<n
mumzzn=p =HDDEIDD~Km mnbmnm =HDDEIDD_KM moo—Km mop—Kn EHDDEIDD_KM mob—Kn mob—Km
onHz .a» w<a w<n From:

mzomHm<mzoo Pmmh q<zouumu

.cmuo: uuuoxueom ago no naoauoun can woodman noouuo nowuuoeov
mono ~o>uo~ ea ooueooouuau you vouoasu~oo no moauouuuuo uoOu ouHHU3Iuoxn=uu can aIsoeuwn3Iceoz .—.o naveoun<

204

 

 

 

 

 

 

 

o.ma o.na o.ma I o.~ I o.~ I o.- QNIR
I I I I I I I o.~ I “In
I I I I e.e I I o.~ I -Io
I I I I I I I o.~ I mIo
I o I I I I 0.0 I I ”Io
has m.e m.~a o o I I e.e I mNIm
pzmummzmam a<m4quH~<osa ezmommzm Am.z.mo Arum.zv «Namd».~v Am.z.mv A:.m.zMI~N.».n.uv me<n
mma»p .oms mum»e .om> msmzz<=o m:o»<m. mmm»p.um> mqmzz<=u m=0c<m
ezqu .m. »<p ~<a emon
mzomH¢<mzoo emu» one<am
0.00 o.m~ o.mmn o.m~ o.~m o.w~ o.~n q.oo o.m~ ONIR
I I I I I I o.m~ o.~m o.mN NIB
o.mo o.n~ o.~e o.- o.h~ m.- o.em o.~o n.oe «NIo
I I I I I I o.o~ o.mo o.~n mIo
I I m.wn I I I I I o.o~ "Io
o.oo o.m o.~m~ o.m o.- o.m o.e D.Dm o.» mnIm
4mzz<xo qmzz<=o meaozIsoa<m guzz<zo amzz<=o mapozIaoy<m ua<a
mqmzz<=o zeaoxIsoy<m m=o~<m meeozI=o»<m mso»<m msoe<m mesozIao»<m m=o~<m maoe<m
exoaz .m. ~<a »<n pmon

m20mH¢<mxoo Hmmh q<on0m~

.znno: nouozueom 0:» mo ocofiuouo new occamou nuouuu aoauaueou vase
vnmnnwm Ho>an =« moococouufiv now vouoaaufloo on moaunauoum umou nqaaozIHoxoauu van aInoouan3I=eox .N.o naeeonq<

205

 

 

 

 

 

 

 

 
 

I o.m~ o.m~ I I m.oe o.~ I o.on oNIh

m.n I I o.~ I I o.~ I o.on NNIo

I I I I I I o.~ n.o o.e~ mIo

I I I I I I I I n.oe an

o.o~ o.n~ m.- m.o n.o o.n n.n o._ o.m~ nNIn

o.« I e.¢w mun I ~.n I I I ~_Im

pzuuzuznam a<u4Iesz<oqa azuuzmzu Am.z.uv Az.m.zv A~.:.».xv Am.z.uv A=.m.zv AN.».:.~V me<a

mumph .um> . mqmzz<=u m=ou<m mam»p.uu> mquzz<mo msou<n
among .a» ~¢n ~<n amon
mzomHu<mxoo ammo ona<sm

o.- o.m~ o.nma o.m~ o.- o.m~ o.mn o.ow n.on oNIs

I I I I I I o.mm o.~h o.~¢ “I”

o.- o.~_ m.e¢ o.o~ o.~e o.n~ “.Nn o.oo o.nn Nqu

I I I I I I o.~e n.Hq o.- oIo

I I o.mn I I I I I o.<s ”Io

o.mn o.e o.em~ o.ma o.me o.m~ o.o~ o.nn o.on n~In

muwmm I n.mn I I I I m.om I NaIn

guzz<zo guzz<=o masozI=o~<m guzz<mo ouzz<=o aaaozIaou<m me<a

IIImuuzencoumpbbrnbbpnnllmppwnm mpppznppwnnIIIIIIMbbwnnIIIIImppFKm . I < msou¢n maoy<n

amoaz .n» »<a ~<a aonz

wzomam<mxoo Hmmh 4<onUmu

 

.cnuo: nouonuaom «so no uaoauoua can neouuou acouoo nouuaaeov
vfieaunau Ho>uoH ca neocououufiv you wouoasoaou no nowuoauouo uaou oauaoaIHoxoauu no. DIsouuwsaIeeoz .n.u uwuaonn<

206

 

 

 

 

 

 

 

 

o.- o.m~ o.- o.~ I o.on n.¢ ~.~ o.oe o~I~
I I I I I I o.~ I o.on NIB
n.s n.< o.o n.» o.~ I o.~ I o.on. NNIo
I I I I I I o.~ I o.~n oIo
I Im.e m.n~ I I I I ~.~ I nNIn
azuuzuzmsm mcmaquHe<oom ezmuxmzm I~w42.uv ~:.mqmuI~N.:.~.uv Am.z.uv Az.m.zv an.»qaqwq ua<a
mumps .ump mum»a .um> mqmzz<=o msou<n mum»9.um> mqmzz<uo msou<n
emuuz .a» u<a »<a azqu
mzomHz<axoo amma zoma<am
o.¢n o.ma o.~ma o.n~ o.eo o.ma n.- o.«o c.~m oNIs
I I I I I I o.oe o.oo n.nn NIB
m.m~ o.n~ o.mn o.na o.¢q o.- . m.oa o.oo m.oe . NNIo
I I I I I I o.oe o.on o.- mIe
I I o.nm I I I I I o.qh ”Io
o.me o.o o.NoH o.~ o.- o.m n.o o.oo o.~a nNIn
gmzz<=o smzz<=o zeaozIso»<n guzz<=o guzz<=o zaaoxIao~<m ue<a
mqmzz<=o zpsozIaow<m mpoy<n .xeaoxI=o~<m maoycs maou<m .=e=me=c»<m maos<n maou<u
a=qu .u. ~¢a ~<a exam:

wzomHa<mrou Emma q<onumm

.guuuz nouoxueom ecu no occuuoun woo neoamou noouuo nouuuoeov .nno

nwsomoa Ho>uoH ca neoconouuuv you vouoaaoaoo no nuaunwuoua uoou aaaanzIHoxosuu ecu alsoauaaalceox .¢.c naveonn<

207

Appendix C.5. Mann Whitney-U statistics and significance
levels (one-tailed) as calculated at peak larval fish
densities of the less common species of Pentwater Marsh.

 

date of peak: 5-25 4-28 5-12 5-25 6-22

YELLOW NORTHERN BLACK JOHNNY BROOK

 

TEST M Jim; W RABIER §ILVER .
DAY/NIGHT:
bayou 66 61 126 36** 54
bayou-mouth 6 ~ - - -
channel 162* - 73*** 198 41**
NIGHT:
bayou/b.mouth O*** - — 4 24
bayou/channel 108 42 56 99 83
b.mouth/channe1 8*** - - 2 28
emerg/f1.leaf - - 3 21 15
emerg/submergent 4 5.5 3 25 -
fl.leaf/submergent 1.5 - - 21 15
DAY:
bayou/b.mouth 20 - - 2 18
bayou/channel 120 28 61*** 99*** 41
b.mouth/channel 8** - — 4 18
emerg/fl.1eaf 27 18 - 12 -
emerg/submergent 24 12 - l4 -
fl.leaf/submerg. 36 - - 15 -

 

1 *** p<0.01: ** p<0.05; * p<0.10

APPENDIX D.

Larval fish coefficients of variation
as calculated for major regions and vegetation types of
the Pentwater Marsh during 1982.

Coefficients of variation as calculated for major regions of the Pentwater Marsh

across sample dates of 1982.

Appendix D.l.

SHALLUW-VATER BAYOUS
NIGHT

 

CY PS YP NP JD LMB BS BC BO US BH MS TOTAL

GS

DATE CARP

 

"OWO'QHnQo‘O
soc-son...

o-a—c—a—IMID—IQNN

NH N
II I II I . II .
N‘Q n

I

I I I I I I I I I

F.

s-l —‘
I I I I I OI I I 0
In In
0 O
I OI I I I I I I 0
M M
M
I I I I I I I I I '
'3
NHo—a
I I I I o o o o
NQMF'I
O§~3 In 0
I ° 0 0| OI I I -
FINN ~Q M
'QONNV‘II'I In
0 s o o o 0' I I s
HMQQM M
o QN I\
I oI I I a II I o
H «QN N
”VINO '3
III 0 s o o o
H'QQF'I ('1
~36 v-I N

4.2
3.5

3.2

 

208

SHALLOH-VATER BAYOUS
DAY

 

CY PS Y? N? JD LHB BS BC BO VS BB MS TOTAL

GS

DATE CARP

 

Inc-ONMIIDIA
O O O O O O
HNOHHu-a

h r~
'I I I I 0
H v-a
In" N
I 0 O I I o
FIN M
I I I l l I
III I II
I I I I I I
~3 O N
0| l OI -
M M M
~¢ QM
OI I I o o
N Inn
—4 u-l
'I I I I 0
N N
QNM
III 0 0 0
N0”

‘0 VD

I 'I I I 0
N N

 

 

o.n I I o.~ I I I I e.N I ~.~ m.n I soon

 

2(39

o.n I I I I I I I I I I I I oNIa
I I I I I I I I I I I M." I NNIo
I I I I I I I I m.~ I I I I an
I I _ I o.~ I I I I o.~ I a.” I I nNIn
an m: on on mm are an a: a» we so we ax<o mp<a

~<a

mhsozIaow<m

 

 

I s.~ I N.~ n.~ I w.~ I o.~ ~.N m.N m.N N.~ emo-
I I I I w." I I I I m.~ h.N I w.N 6NIN
I I I I I I I I I q.~ —.n I "In BIN
I I I I I I I I I h.~ I I n.~ NNIo
I I I I ~.N I I I I 0.“ o.~ I N.6 on
I n.N I I I I m.~ I o.~ o.~ w.~ m.N 0.0 “I0
I I I N.“ I I I I I o.~ —.~ I c.o nNIn

mm m: 0m 0m mm mtg 95 A: m» mm uu mo mm<o ”949

H=qu
=H=OZI:Q»<Q

Av.ueouv ~.n uaveona<

eunfisun eoHuuos um: “vmozaasn etch; Inn “masons nude: um: "cannon Ion
“odaanuo Jonas Ion ”ovuauo>aun xoooa Imm momma nuaoeomuoa Imzq uuounmv season law
“exam euosuuoe Imz “canon roads» In» u.anu masons; Imp “vacuuonu two “vase uuonuum Imo

 

 

210

 

 

 

I I I I I I m.n I I e.~ m.n ©.~ ~.m m.~ coon
I I I I I I I I I I I I <.n h.~ ONIB
I I I I I I m.m I I n.n m.m I w.~ I NNIo
I I I I I I I I I o.H I O.N I m.N nNIm
I I I I I I I I I o.~ I I I I Nfiln
m: :m m: Om om mm at; oh m: m» mm >0 mu mm<o mh<n
~<n

qmzz<mo
N.~ m.~ I m.m I m.~ n.~ w.~ m.N I ~.N o.~ ~.n w.~ ~.~ zoos
~.N I I I I m.m I I I I o.~ o.n I mIM Owls
m.o I I I I ~.m I I I I I I n.n ~.~ NIN
5.0 I I I I m.~ ~.m I I m.n I I m.n 0.0 NNIQ
m.~ I I I I o.— m.~ <.N I I I s.n o.N a.” mlo
e.o m.~ I I I m.m I I c.~ I o.~ w.~ n.N m.~ m.o mmln
o.~ I m.m I m.m I I m.n I q.“ I I I I NHIm
4<FOF m: mm m: Om Um mm as; aw m: m» mm »o mo mm<u mh<n

HIGH:
4mzz<=o

 

Av.ucouv ~.: naveoaa<

211

 

 

 

 

 

o.— I I I I I ~.H I Q.N O." I Q.N n.~ I O." aco-
m.o I I I I I I I I I I a." I I n.N oulh
0.0 I I I I I I I h." I I I I I 0.0 Nulo
m.N I I I I I I I I I I I w.N I I on
«.0 I I I I I I I I I I I o.n I ~.ov ulo
a." I I I I I I I o.n o.~ N.H I I I I Nuln
AdHOH m: mm m: Om on mm at; :5 m: m» mm »o mu mu<o mace
u<n
Hzmommzm
~.~ I I I I I I m." o.~ o.N n.o ¢.N h.~ I h." cool
n.~ I I I I I I n.~ I I I I I I M.N ONIN
N.~ I I I I I I I I I I ¢.N I I c.~ NIN
N.o I I I I I I I e.N ¢.N I e.N I I o.N NNIO
~.~ I I I I I I I I Q.~ I e.N o.~ I ~.~ 0I0
0.0 I I I I I I I I n.N I I I I 0.0 "Io
m.n I I I I I I I o.“ h.~ I I B.“ I N.N nNIn
~.o I I I I I I I h.~ h.~ n.o I I I I N~In
~.O I I I I I I I I ~.o I I I I I mule
44809 m: mm m: Om on mm at; an mz m» mm »o mu mm<u mh<n
ymouz
Hzmommzm

 

.Nmo~ uo noumv nausea noouoo noun: nouorueom on» we
nonuu :owumuowo> names new vouc~=u~oo no eofiuoausp uo nueo«u«uuooo :muu ao>umg .N.n naveonn<

Appendix D.2 (cont'd)

 

FLOATING-LEAF

NIGHT

CY PS YP NP JD LHB BS BC 80 US BH MS TOTAL

GS

DATE CARP

 

NMO‘NOM
as. so.

HrdC)OIH—C

h
I OI I II
N
II I II I
I II I II
0
II OI II
—I
Q d
II OI I O
N N
Q ‘#
I OI I I O
v-d N

VfiwrdOQFHO

NCD—odru—o

W N o
NHNNNNM

vuo¢r0r~r~w

O‘v—l

00-!

1.4

mean

 

 

FLOATING-LEAF

DAY

212

Y? NP JD LMB BS BC BO HS BH HS TOTAL

PS

CY

GS

 

DATE CARP

 

eaaasun voauuol um: “voonaaaa one»; man “noxuen nude: um: “euwxoa Ion
nownmouo xosan Ion “ovuouopaun soon: Imm “noon nueosouusm Imzq “nouuev seenon low
“as“: euoguuoe In: “canon nouns» In» “.nnu nuance; Imp "vanqunuo luv «vane vuounuu Imo

 

 

21L3

 

 

 

N.” I I I I I I w.~ m.~ e." I n.~ ~.~ I n." coo-
N.~ I I I I I I m.~ w.~ m.~ I n.~ ~.~ I n.u n~Io
2.2 I I I I I I I I q.~ I I I I o.~ oNIh
N.” I I I I I I I I I I «.2 N." I a.o NNIo
o.o I I I I I I I I I I I ~.~ I 0.0 ”Io
n.~ I I I I I I I I I I I m.~ I o.~ “NI“
a." I I I I I I m.~ m.~ I I I I I I NEIn
q<eoe m: =m m: on on mm are an a: a» ma »u we amco ue<a
y<a
azmuxmxmam
a.“ I I I I I I I n.~ m.a m.~ «.2 o.~ I ".2 ago:
N." I I I I I I I I I I h._ I I h._ o~I~
o._ I I I I I I I I I I I I I o.o “In
h.o I I I I I I I I I «.N I n.~ I ~.o «NIo
e.” I I I I I I I I «.N I «.2 n._ I o.o «I»
~.~ I I I I I I I I I I I I I N." aIe
~.~ I I I I I I I n.~ I I I ~.~ I «.2 nmIn
N." I I I I I I I I I N." I I I I NaIn
o.~ I I I I I I I I ~.o I I I I I naIe
qaaoa m: z» m: on on mm at; an a: a» ma »u we am<o ma<a
Emma:
pzmoxmzmsm

 

Av.ueouV «.9 naveoan<

APPENDIX E

Larval fish total lengths (meaniSE in mm)
across major regions, bayous, vegetation types,
and channel stations of
the Pentwater Marsh during the 1982 sample season.

214

1
Appendix E.1. Student-t values and significance levels
(one-tailed) of larval carp total lengths across stations,
day/night, and vegetation types.

 

SAMPLE DATES

 

 

 

 

TEST 5—25 6—1 6-8 6-22 7-7
DAY/NIGHT:
bayou 2.3*** 4.0*** — 5.2*** —
bayou-mouth 0.7 1.0 2.4*** 0.2 -
channel 1.9* - — - -
NIGHT:
bayou/b.mouth 4.3*** 3.9*** 0.6 4.8*** 2.7***
bayou/channel 1.2 - 0.8 2.7*** 1.1
b.mouth/channel 4.1*** - 0.9 7.0*** 3.0***
emerg/fl.leaf 1.4 7.8*** 2.4*** 0.4 0.8
emerg/submergent 0.2 7.7*** 3.8*** 1.8* 1.2
fl.leaf/submerg. 1.7 1.5 0.9 1.9* 0.2

DAY:

bayou/b.mouth - — _ - _
bayou/channel 3.6*** - — — _
b.mouth/channel 1.6 - — _ _

emerg/f1.1eaf 1.6 — 1.4 — _
emerg/submergent - - 0.4 — _
fl.leaf/submerg. - - 1.5 - -

 

1 *** p<0.01; ** p<0.05; * p<0.10

215

Appendix E.2. Student-t values and significance levels1
(one-tailed) of larval fish total lengths across stations,
day/night, and vegetation types for major species of larval
fish in the Pentwater Marsh.

 

YELLOW NORTHERN

 

TEST .CXERINID._RERCH .EIKE__
DAY/NIGHT:
baYou 2.7*** 0.4 -
bayou/mouth 7.3*** _ _
channel 0.9 1.4 -
NIGHT:
bayou/b.mouth 0.8 - _
bayou/channel 0.04 - -
b.mouth/channel 0.5 - -
emerg/fl.leaf - 0.5 _
emerg/submergent 16.3*** - 2.5**
fl.leaf/submerg. - - _
DAY:
bayou/b.mouth 17.8*** _ _
bayou/channel 1.2 6.2*** _
b.mouth/channel 7.5*** - _
aware/fl.leaf 1.8 - _
emerg/submergent 0.3 0.4 -
fl.leaf/submerg. 1.8 - —

 

1 *** p<0.01; ** p<0.05; * p<0.10

APPENDIX F

Student-t values and significance levels (one-tailed)
of larval fish total lengths (mm)
across major regions, bayous, vegetation types,
and channel stations of
the Pentwater Marsh during the 1982 sample season.

216

 

 

 

 

 

 

 

 

I I I I I I I I I o.a«o.h oNIA
I I I I I I a.a«~.h I I o.q«o.o NIB
I I I I I I I I I o.q«n»o NNIo
I I I I I I ~.o.«n.n mafia I 336 I.
I I I I I mane; «536 «6.3.» I 93".... To
I m.q«o.n I I I I I a.N«~.o I e.q«n.o mmIn
udquusqam “Ham<xo mm<a muam<n moan momma manomqu maazHumuu q<=m m~<o when
ocean uo<qn =a=oxuo~<q yzzmoa zmumpuoz semen» na<NNHo
. amoaz
mp=o=I=OȢm
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I I I I I I I I I <.o«~.m an
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I I I I I s.o«o.n I I I I NaIn
Immwmnumnmm mummnmo mm«m nus..= u._a magma mwnauuaIIwanzHumuu q<=m au<o np<n
goo.» uo<an nepoxmox<a uzzmon zammpuoz. mouse» n~<~NHu
»<n
maou<n uua<aIaoss¢=m
I I o.o«n.on I I I I I I n nIo
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I I I ~.o4~.m I I I N.~«~.a~ I ~.n+o.m NNIO
I I I I I I «.oue.n o.~«n.o I n.~H~.o ”Io
I I I I I I I I a.oum.n c.2nn.h ”Is
I I I A.H«h.a I n I n.~Hm.s I c.ouo.n mNIn
I I I o.o«s.n s.o«o.m a.o+_.n I I I I Nanm
macuaaaacm meaa<uu mmam mmem<a uaaa zoxma mazoams mnHsza»o a<=m ax<o ua<n
.ooum uo<sm aeaozmo¢<s pzz=o~ zam=e~oz manna» au<~NHo
p=oaz

wee .m:o»on Loxoa .nsoamp Loan: 0:» :« unmue up can any up As. ea mm+cooev acumeoa anuOu gnaw Ho>uoa

wzow<n xmh<3I1044<=m

.eoooon cannon «wag ozu «cause noun: nouunueom mo uHoeeogo

.2.» unecoaa<

217

 

 

 

 

 

I I n I I I I I o.q«m.n I onIh
I I o.o+n.~n I I o.o«~.o I I o.o«m.n n «qu
I I I I I e.omo.o I n.o«e.o I o.o+m.o nNIn
I I I I I w 41$: I I I I :In
unumam>qum maaa<zo mmen amazes muaa momma wmzoauq maHzmaauo a<=m a¢<o na<a
noose uo<an aaaoxmuaeg pzzaoa zumzeuoz sedan» am<~NHo
~<a
au==<uo
I I I I I I I o.~«o.ha I I nIm
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I o.o«~.c o.o«~.- I I ~.o«~.- I I ~.q«m.n ~.o«~.n «NIo
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I ~.o+o.n I ~.o+~.n I o.o«~.- ~.o«~.n o.o«n.~ _.a«o.n ..c4~.o nuIn
I N. DH» .% I I I hone .P I I I I KHIn
unumxusaHm muaa<¢u mm<n umpm<n NEH“ momma meoama maHzHuauo a<mw am<o ma<n
“comm uo¢qn zeeozuom<q uzzuoa zgmzaaoz songs» nu<N~Hu
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I I I I I I I I I ~.o«o.o AIA
I I I I I I I I I a.o«n.o -Io
I I I I I I I I I s.o«o.o oIc
I I I I I I I n I ~.a«¢.o an
I I I I I I I m.o+m.o~ I o.q«~.o nNIn

nooum

uo<qn

=H=02mom<q

wzz=OH

zxuzhmoz
=9:

3044M»

~<n
ozlao»<m

nx<NNHu

Av.ueoov ~.m naveonn<

2118

 

 

 

 

 

 

I I I I H I I I I D.Mflw.n ONIs
I I I I o.oH~.cn I I I I m.ofln.s NIN
I I I I o.o+o.~n I I u. I ~.o««.o -Io
I I I .II II N I I .I. n.0fim.o mIo
I I I ~.~+n.c n.o+c.n o.o+N.ne I m.—fl4.o H.0flw.n c.~fiw.s “Im
I I I I I I I «.mfld.s I I maln
unumzu>qnm m~mm<~u mmcu mmsm<n mung momma anommq mnHzHMmNuI =<=m md<u mad:
noonn uu<qn uksozucx<4 wzzucn zmuzhuoz 3044M» nacuuuc
Faun:
» =o~<n
I I I I I I I I I m.~«n.o oNIa
I I I H I H I «.036 I I nNIn
I I I H.o+n.n o.omw.es e.o+o.n I I I I NaIn
I I I I ~.~+o.o I I I I I naIe
mnummm>4Hw mumm<mo mm<m «Nazca muHm zommm mHzomNA mnHzHumHu a<mm Adda mad:
“comm Hu<4n shaoxmom<a uzz=Oh zummhaoz sedan» nm<NNHo
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I I I I I I n.o+<.n I I o.eflo.w KIN
I I I I I I I I I o.o«n.o «NIo
I I I I I I I I I ~.ofln.o on
I H I I H H I nJflnJ. I n.o3.o To
I ~.o+~.n I I w.~+~.- m.o+o.o I I I I NuIn
maHmmm>4Hm mumm<x0 mm<m mmhm<o muum momma mmrommq mnHZmewo n<=m mm<u mad:
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Brouz
x =o~<m

 

noucsueom we

N wen .3 .» .x nachos

an new“: as van was as flea an mm

“downy acumeoa auuou gnaw uo>unq

.eoooun nausea «mom ozu weaken nuns:
.~.a unecoaa<

2119

 

 

 

 

 

 

I I I I I I I I I ~.~«m.~ ONIA
I I I I I I ~.a«a.m I I N.A«m.n NNIo
I I I I u I I A.H«u.o I e.o«o.o nNIn
I I I I m.a+m.o I I I I I NaIn
monamssHm “Haa<¢o mm<m ~m~m<a mane momma mozoamo maHznmauo a<=m a~<o ua<a
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a souam
I I I I I I c.2«c.h I I ~.~«q.a oNIs
I I I I I I o._«n.a I I I NIN
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I I I I o.o«o.os I n.o«e.n o.o«o.n I o.o«o.o mIe
I I I I I I I n.~««.o I n.0«a.h "Io
I I I I I I I n.~«¢.o I n.o«N.o mNIn
mnmem> :w MHNMcmu mucn muHMcd MHHN mama“ WHZCE MGHlan—hu fi‘lm nu‘d NF:—
uooun uo<qn =p=ozmu~<a yzzmon zmmmamoz nonsm» nu<NNHo
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: =o»<n
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I I I I I I I I I o.o«~.n «NIo
I I I I I I I I I o.o4c.m an
I I I I o.oMo.n~ I I I I I «aIn
I I I I o.o+o.m I I I I I mHIe
maHmzmssHm maaa<mo mm<m zmea<o mean zomma mazoamq maHzHaa»u a<=w au<o ua<p
soomm uu<sa mpzozmux<s »zz=o~ zamzeaoz :oagm» n¢<N~Ho
L<a
» po»<m

 

Av.ueoov N.m naceunnd

220

 

 

 

I I I I I I I I I n.o«n.n NuIe
I I I I o.o«~._n I I m.~«o.o I ~.o«~.n nNIn
I I I I Ipwoflm.mH I I I I I NaIn
maHmmuqum m~aa<~o mmem umhm<a mama zoxma mHzoamq monHuauo a<=w au<o mace.
moons uo<qn maeozmea<o uzzmon zmuaeuoz :osam» a~<N~Hu
~<a
N aop<n
I u o.o+m.on I I I I I I I nIo
I m.e+m.nn I I I I I I I n.m«m.m NIN
I I I I I I u I I o.~H~.o NNIo
I I I I I I e.o+~.n o.nH~.~ I N.~ߢ.h mIo
I u I u I I I u I a.am~.o "Io
I ~.~+a.m I ~.~+o.~ I I I a.a+o.o I s.o+_.o mNIm
m. u. . ...n .n U. h.. ._ . . “.. ... . . L. ... .U. ;
“ooze uo<on meaozuum<s ~zz=oa zenmamoz mosque au<N~Hu
azuaz
N =o»<m

 

Av.u=oov N.m uwmeonnd

2221

 

m.~flh.m o

 

 

 

 

 

N A
I I I I I I I I I o.m«o.- “In
I I I I I I I I I ~.num.~ «NIo
I I I I I I o.o«~.m I I s.~«o.~ QIo
I I I I I I I I ~.o+m.m ~.o«m.o HIo
I I I I I I I I I m.o«~.o mNIn
maommmasam unaa<xo mm¢m mmpm<a moan =omma mmzoamq maHsza»o n<mw ax<o mp<q
“seem uo<sm zeaozmu~<s yzz=on zmmmexoz soasu» =u<NNHo
azoaz
a<msIozHe<oqm
I I I I I I I I I ~.~«e.o ONIN
I I I I I I I I I ~.o«m.m -Io
I I I I I I I I I ~.o«n.m "Io
I I I I I u I ~.oHo.n I I mnIm
I I I I m.~Hm.~a m.o+o.m I I I I NaIn
mammmmssam maaa<mo mm<m mmem<a mesa zomwa mHzoams maHsza»o a<=m am<o up<n
noozm uo<qm zezozmcm<s »zz=oe zam=e¢oz nonsm» . n~<~NHu
m<a
ezmummzm I
I I I I I I I I I A.e«~.o o~I~
I I I I I I I I I o.a+o.m BIA
I I I I I I I I I o.~+a.h -Ic
I I I I I I i.oa~.n o.o«m.o I m.o«~.e mIo
I I I n I I I I I n.o«q.m “Io
I I I m.aum.a I I I e.o«n.n I m.o«o.n mNIn
I I I e.o+s.m m.am~.~a s.o«o.n I I I I NaIn
I I I I m.o+m.m I I I I I maIe
moommm>gam maaa<mu mm<m mmpm<a moan zomma maxoams maHzHaa»o a<mm ax<o ua<n
“cemm eo<am =e=czmumls >zz=on zzmzemoz zessm» nu<NNHu
axon:
Ezmommzm

ecu .ueoHIweHumoHu .ucomcoeo cw unwfie up use see up Ass ea mmficmoav ecumcmfi Houou :mwu Hm>umq

.comaom ofiaemm Nwofi ecu mcwusu zone: nonmaueom ecu uo mcofiumum o>wumuomu> ueomuoansm

.m.a unecoaa<

2222

 

 

 

 

 

I I I I I I I I I m.m¢m.a omIa
I I I I I I m.mum.m I I m.o4m.n mmIm
I I I I I I I n I o.oum.a mIo
I I I I I I I m.o+o.o I m.o+a.n nmIn
I I I I I m.o«o.m I I I I mmIn
NnHm¢N> .Hm.<xI . m 1.. M. .I_ . .1... n... . m u. ..u .U. . ..
moomm momma mamozmommm mmmmom mmmmmmom mommm» mmmmmmo
mam
ammommmmmm
I I I I. I I o.a«o.mm I I m.m«a.m omIa
I I m.mua.mm I I I I I I m.n«m.om aIa
I I I I I I I m.m«a.mm I a.a«m.a mmIo
I I I I .I I manna €966 I Roam; mIo
I I I I I I I I I a.o«o.o mIo
I I I I I I I a.o«o.o I m.o«o.n nmIn
I I I I I I m.o«o.o I I I mmIn
I I I I n.m«a.m I I I I I nmIm
mammmmammm mmaammo mmmm mmmmmm mmma momma mmmoamm mammmmamo mmmm ammo mama
moomm momma mmmozmommm mzzmom mmmmmmom mommma . mmmmmmo
mmomm
ammommmmmm
I I I I I I I I I o.mum.o mmIo
I I I I I I I n I m.o+m.m mIo
I I I I I I I a.o+o.m I m.m mmIn
mammmmammm mmaammo mmmm mmmmmm mmma momma mmmoamm mammmmamo mmmm ammo mama
moomm momma mamommommm azmmom mmmmmmom momma» mmmmmmo
amm

m<mqloth<oqm

Au.ueouv m.m xmueoqa<

223

 

I I I I —.oHN.n I I o.~fim.h ONIN
I n.ofls.o «In

 

 

 

I I o.oflm.mm I I I I “.mno.»m m.o«m.n m.o«o.n mmIo
I I o.m«n.nm I I I I I m.oan.m n.o«a.o mIo
I . I I n.oflm.n I I I I m.o«m.m n.o«o.o mNIn
.nxmm Yam.“ .j Ti. mm... x... .1”. .J u;
moomm momma manommommm .»mmmom mmmm»mom momma» mmmmmmo
mmomm
mmmzmmo mam:
I I I I I I I I I m.o«o.o omI»
I I I I I I I I m.o««.n m.o«o.a mIo
I m.oMo.n I e.oaa.n I «.mfln.mm m.o«m.n m.m«m.» I n.o«o.o nmIn
I ».o+m.n I I I o.oflo.m I I I I mmIn
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I I I o.ofln.n I I I I I o.o«m.m mmIo
I I I I I I I I I m.o«o.n mIo
I m.oflm.n I o.ofla.n I I I I I n.o«o.o nmIn
I m.ofln.m I I I I I I I I mmIn
mammmmammm mmaammo mmmm mm»m<m mama _ momma .. mmmoamm mmmzmma»o.- mmmm..;;- ammo mama
moomm momma m»mommom<m »mmmom mmmmmmom momma» mmmmmmo

Hmunz
zoz<¢a memo:

.eonnnn unnann Nmom can madman noun: mounxueom on» we Hoeeneu can:
wen gonna; zumon .zoenun sumo: on» em gamma as men new so Ass em mwfienolv nguweou anuou anmu Anson; .¢.m naveoaa<

224

 

 

 

 

I I I I I I n n.mHm.am I n mIm
I I I I I I m.o+m.n I I m.mH».m omIa
I I o.o«m.mm I I I I I I m.on.n mmIo
I I o.m«m.nm I I I I n I m.on.m mIm
I I I a.oH».n I n.~Hm.mm I o.mo+m.a I n.o+m.o nmIn
I m.o«m.m I I I m.oam.» I I I I mmIm
mammmmammm mmaammo mmmm mmmmmm mmma momma mmmoamm mammmma»o ammo ammo mama
moomm momma mmmommommm »zmmom mmmmmmom mommm» . mmmmmmo
mmomm
mmzmmmo mmmm
I I I I I I m.ofin.m I I ».o«m.a omIa
I I I I I I I I I n.o«».o aI»
I I I I I I I I m.o«m.n o.o«a.n mmIo
I I I I I I I I I a.o«m.o mIo
I I I I I m.m«m.mm n.0«m.n o.m«n.a m.o«o.n n.0«m.o nmIn
I I I I I m.omm.wI I I I I InmIm
mammmmammm mmaammo mmmm mm»m<m mama momma mmmoamm mommmma»o ammo ammo mmmm
moomm momma mmmoxmommm »mmmom mmmmmmom mommm» mmmmmmo
mmomm

ago no nmoecnco oumn nan cm: on uzwme he van unu an Ass em wmhdnoev acumeoH Humou noun Hn>mnq

qmzz<mu nH:

.eonnnn qusnn Nmou ecu acumen anunz mounzueom
.m.m nuneonn<

APPENDIX C

Larval fish diversity indices (H', D, and J)
as calculated for various regions and stations of
the Pentwater Marsh during the 1982 sample season.

225

 

 

 

 

 

 

 

 

05.0 00.0 0n.0 <~.~ 0~.— nu.“ 5n.~ 50.~ 0~.~ 00.0 00.H nn.0 00.~ v¢.— cu.0 ma." anon
«5.0 no.0 I no.0 00.0 00.0 00.0 00.0 I I 00.0 0n.0 I mo.0 00.0 00.0 0NI5
n0.~ n0.0 00.0 0N.0 00.~ 0N.0 nn.0 00.0 00.0 I I I I u0.0 00.0 0n.0 NNIo
n~.0 I I I I I I I I I I I n0.0 I I I 5~.0 "I0
Nn.~ 00.0 00.0 50.0 0—.0 ~0.— N0.~ 50.0 00.0 50.0 om.0 I on.0 n0.~ nu.0 00.“ nmln
«N.~ m0.~ I 00.~ I I I I I I I I 00.” 00.0 I 50.~ -In
. Im ”I m .. m... .. . . o .. ”u ”a 3 - z<mu H 0: =05<m uh<0
IH<04m :Haom memo: =0~<0
=0HH<Pmum> muzz<mu =05<0 20Humu
5<0
00.~ «0.0 no.0 00.0 “5.0 ow." 00.0 on.~ 00.0 05.0 no.0 «0.0 no.0 5N." ~0.0 e0.~ you»
00.0 I 00.0 I I I I I I 0"." I I I I I 00.0 nIo
00.~ m~.0 ~c.~ 00.0 00.0 00.0 05.N I on.0 I n<.0 an.0 I 50.0 00.0 c0.~ 0NI5
0~.~ on.0 un.0 0~.0 00.0 05.0 00.0 00.0 00.0 Ho.0 I I cm.0 0n.0 04.0 0~.~ 5I5
~¢.0 5~.0 00.0 no.0 55.0 no.0 «0.0 00.0 5n.0 I nn.0 ~0.0 I 00.0 0N.0 -.0 male
nn.0 on.0 0~.0 -.0 5<.0 no.0 nN.0 05.0 00.0 on.0 5¢.0 I I 0¢.0 nn.0 0~.~ 0I0
00.0 00.0 mn.0 00.0 I I I I I I I 55.0 «0.0 I 05.0 ~0.0 filo
o~.~ m5.0 00.0 n5.0 00.0 -.— nm.0 0~.~ 0n.0 n5.0 00.0 I I 00." «v.0 0n.0 mNIm
m~.~ 00.0 I «5.0 «5.0 mq.0 00.0 «5.0 00.0 I I I 00.0 n0.~ I 00.0 Nfiln
manImmm<z mammaw m<mAI wanna MQHm 0H: 2H4: Ian INMI IINI : M H :<:L msdaflllddflddlllflHdfi
Ip<oqm mksOm :Hmoz =05<m
20HH<Pmum> muzz<=o =05<n _ onumu
H=0Hz

 

.Nwo~ acumen noun: mounxunnm can

no neommnun can macawom nnomana mow vounmsoano nn A.= v nnowvem mumnmnsmv an>n03Ieoeennm gnaw ~n>unq .~.0 naveoan<

2126

 

 

 

 

 

 

 

am.m am.o am.m nn.m mm.o mm.m m~.m on.m ao.o ma.o mm.m ma.o mo.m mn.m am.m mn.m non»
mm.m mo.o I mm.o I I I I I I I am.o I mo.o mo.o m».o omIa
mm.m om.o I an.o mm.m ma.o no.m I I I I I I am.m on.o mm.o mmIm
mm.o I I I I I I I I I I m~.o I I I mm.o mIo
mo.o mn.o mm.o cm.o ma.o am.o me.m mn.o I m».o n~.m I on.m mo.o oo.o nn.° mmIn
mm.o om.m I mo.m I I I I I I I I mo.m I I oo.o mmIn
mamaImmmmm mmmmmm ammm ommmm mmmm mm: 2mm: .mm .mm m a »II x m<mokmmmon..mo»<m mama
IIIIIIIwmamaIIIIIII IIIIIIIIIIIIIIIIIInmmomImmnozI IIIIIIpo»mnIIIIIII
mommmmmoma mmzmmmo mo»<m .momomm
»<m
om.m ma.o ma.o o».o mn.m mm.m ao.o mo.m mo.o mm.m m».o on.m om.m nn.m on.m mm.m an.»
mm.m I om.m I I I I I I am.m I I I I I nn.m mIm
o~.m om.o ao.m I mo.o mo.o mm.o I I I mm.o mo.o I om.o no.m ~m.o omIa
am.o am.o mm.o mm.o I ma.o m».o I I an.o I I mm.o ma.o I ma.o aI»
nn.m om.o I oc.o mm.o ma.o mo.m mm.o nn.o I I om.o I mo.m I am.o mmIo
ma.o mm.o mm.o an.o mo.o om.o oa.o oo.o I mm.o am.o I I mm.o mn.o om.o mIo
om.m I mm.o mm.o I I I I I I I mm.m a~.o I mm.o mm.o mIo
mm.m mn.o I ma.o mm.o mn.m om.o am.m mm.o om.m m».o I I on.m o».o mm.m nmIn
mo.m I I am.o om.o oa.o I am.o I I I I no.o oo.m I mo.o mmIn
mammImmmmm mmmmmm ammm ommzm mammIImm: 2mm: .mmI .mm N m mI m mmmo memo: mo»<m mama
Immoma mmmom mmmom mo»mm
mommmmmoma Immzzmmo mo»mm maHuNMIIIIII
mmomz

 

.mmom mamaam manna
mounmueom any 00 meowmo» ven neOwunon nsommn> you vnunasoano no 500 nnoezuwu noaunqn gnaw Hn>unq

.~.0 nuneoan<

227

 

 

 

 

 

 

 

 

 

 

 

0n.0 an.0 am.0 oo.0 No.0 o5.0 mn.0 o~.m on.m mn.0 mo.0 oo.0 oo.0 0n.0 nm.0 5n.0 moo»
no.0 oo.0 I no.0 oo.0 no.0 oo.0 I no.0 I I ~5.0 I an.m 00.m no.0 0nI5
no.0 o5.0 I o~.0 oo.0 0o.0 0n.0 I I I I I I oo.0 I mn.0 NNIo
om.0 I I I I I I I I I 0~.m I I I n~.0 mIo
~n.0 no.0 no.0 no.0 om.0 No.0 no.0 5o.0 I oa.0 5n.0 I mn.0 oo.0 5o.0 oo.0 nNIn
on.0 I I o».0 I I I I I I I I on.0 I I on.0 NmIn
.NqHaummu4aIIIumandmlmouqllddmmuluqulldHu I amox Inn Inn IIN 3 w x z<m0 memo: pouon neon

Ipooma memom zhmoz =0»<n

.Iddmwmeaumo muzzomu Damon gonna“.
»o0

mo.0 no.0 mm.0 no.0 mn.0 oo.0 oo.0 no.0 nn.0 mo.0 5o.0 0o.0 no.0 nn.0 5n.0 no.0 one»
00.m I no.0 I I I I I 00.m I I I I I oo.0 nIn
oo.0 o~.0 ~0.m I 00.m 0n.0 ~a.0 I oo.0 I on.0 mm.n I oo.0 No.0 no.0 0~I5
no.0 mn.0 oa.0 n~.0 00.0 5o.0 no.0 I I nn.0 I I oo.0 no.0 I on.0 «I5
no.0 mn.0 oo.0 n~.0 I I I I I I N~.0 m0.0 I oo.0 I oo.0 -Io
5m.0 no.0 mm.0 mm.0 o~.0 oo.0 om.0 oo.0 I oo.0 oo.0 I I no.0 nn.0 o5.0 nIo
No.0 I I I I I I I I I 00.m I I I oo.0 on.0 mIo
oo.0 No.0 I no.0 No.0 5n.0 no.0 no.0 no.0 No.0 00.m I I no.0 oo.0 oo.0 oNIn
05.0 I I no.0 I I I I I I I I no.0 I I no.0 NmIm
mqHmummM4zIIIqMuquluommllununMIMQlelq ”II mum: Inn IImn N a 5 u zonu mono: nouon neon

Ihoomm . ahaom memo: souon

IIudHHoHuuMHIIIII. muzzomu nomon zouunm

Baum:

.Nnom

weapon noun: mounaueom on» no neOmunun oen neoonoa nnowmn> new nounanano no 500 nnoeeopo snow Hn>unq

.n.o umocoaao

APPENDIX H

Mean sample Shannon-Weaver diversity indices (H')
across stations and regions of
the Pentwater Marsh during the 1982 sample season.

 

228

 

 

 

 

I I I 50.0 I nn.0 I I I I I I 00.0 I I MIm
I ~—.0 N—.0 N~.0 I 5~.0 I I I m~.0 I I 00.0 00.0 00.0 0NI5
-.0 00.0 00.0 I ~N.0 oo.0 I I 50.0 I I -.0 n~.0 I 00.0 5I5
0N.0 I 00.0 an.0 5~.0 om.0 0n.0 nn.0 I ~N.0 00.0 I on.0 5H.0 n~.0 Nulo
nn.0 NN.0 00.0 0n.0 oN.0 mn.0 No.0 I 00.0 5N.0 I I 5~.0 oN.0 0~.0 0I0
I -.0 -.0 I I I I I I I o~.0 I I oo.0 00.0 "I0
0~.0 00.0 m~.0 ~0.0 no.0 oo.0 00.~ ~n.0 No.0 I I I no.0 0n.0 HN.0 mNIn
I I mm.0 00.0 o~.0 I No.0 I I I I 0~.0 o~.0 I 0H.0 «film
m0H3Immm<x zmzmam m<mq uzmru unmm 0H: zH<z .mm .mm N 3 5 x z<=0 09:0: =05<u ua<0
IF<0AL =H=0m mhuoz =0~<0
20HH<Hm0m> qmzz<=0 =05<n acuumu
Hmouz

 

.nonnon cannon Noam ogu nnwuno
noun: aounxueom ocu no unemnom van anemonun nnOLun A.=0 nooonem muonm0>wn un>n03I=oeengm ouosnn enn: .0 nooeooa<

APPENDIX I

Standing crop estimates (#/HA)
for larval carp, cyprinids, Lepomis spp., northern pike,
and yellow perch
as calculated for major vegetation types of
the Pentwater Marsh during the 1982 sample season.

229

eomunuono> ueonmosonn Im “acmunuonop unoHIneaunoHu Iz “nonunuowos ueonuoao Im a

 

 

 

 

 

I I I I I I I I I I I o I mm I I I I I nlw
I I I I I I I m I No I N I 5H I moo nmo mm 50m 0~I5
I I I I I I I o I I 5H I I I I m5" nnu n0 nmn 5I5
I I I I I 5” o I I 5H 0H an I I 5~0m n00 5-~ nmoo -I0
I I I 50 0N I 50 0a I mm mm ONN coo 5H m0 o00n 0000 Oman 500w 0I0
I I I m I I <0 I I I I I I I I N05 00m 00a 0mm~ "Io
I I I o I I 5~ I I I I oNH man I 50~ own 00m 00m nmo mmlm
NNN 00m 00o on I I 50 I I I I I I I I I I I I -Im
I I I on 50 I On I I I I I I I I I I I I nalo
0<HCP m 0<FOF m z m 4<908 m z m 4<POH m z m J<FOH m z m mh<0
muum mHzommq maHszmwu mm<o
2mmxhxoz

mOmU 02H02<Hm Prqu

.eomnon oaoenm Nnom nnu neonno zmanz anunxueom nzu no noon» eouunuono> acnns Lou vounanuano nn guano

:oHHo5 can .nxmn eaozuaoc ..00mldddd4fl4 .nomcmunuo .manu an>mnH Lou A<:\nv nounaounn coho meanenum .H xaoeooo<

APPENDIX J

Estimated larval fish drift (thousands/hour)
between Pentwater Lake and Pentwater Marsh
during 1982.

Appendix J.

230

Estimated larval fish drift ( thousands/hour)
between Pentwater Lake and Pentwater Marsh during 1982.

Negative values represent net drift into the marsh due to
seiche activity.

 

BROOK
DATE TIME CARP CYPRINID LEPOMIS ALEWIFE SILVER EGGS
5-25 600 4 4 - - — 204
2400 29 - - - —
6-10 600 22 - _ _ _
1200 4 - — 7 -
1800 4 - - - -82
2400 37 -33 34 25 -
6-23 600 —7 — - - —
1800 63 — _ _ -
2400 37 - - - —
7-8 600 - - - - 22
1200 - - - - 7
2400 -345 - - - -
7-20 2400 4 — _ - -

 

APPENDIX K

Spearman—rank correlation coefficients
and associated significance levels
among parameters and larval fish densities in
the Pentwater Marsh during the 1982 sample season.

0~.0v0 n “no.0v0 to “H0.0v0 son H

 

o0.~I I I I I I I I I I unoulam
one o0.0I one ~5.nI I I I I I I I I .nmolu
n~.~ 05.0I «n.0I I I I I I I I >ou.no>
0~.0 on o~.~ not no.~I no.0I I I I I I I soon:
n~.0 ~0.0I no.0 nn.0 om.0I I I I I I .ouna
n0.~l n0.~ ~0.0I ~m.0 on. 00.5 no.0I I I I I 00
nn.0 no.0 00.0I o~.0 no.0I 5N.0 not mm.NI I I I ouch
on.0I -.0 No.0 on. mn.~ n5.0I not «m.~ nm.~I I I unnoq
~o.~ oo.0I ”n.0I 0~.0 no.0 oo.0 no.0I at n—.N oo.0I I news
oo.~ Hm.01 nN.~I mnub. Inm.HI o0.” InNn mo.MI non omwm not n5.nI no ~m.~ mono
azuuumzmbm m<mqlm Hzmouutm umooo.um> manna uhnnumuah on arms Hmong mth

 

231

Hnueoeoomopnn neoln Ho>na

oonnoquqnnun onunuoonnn one

.AOnIeV anon: mounuueom can no nnuuuneov aunu Hn>una one nuouOInuno

nunowomuuooo nouunnomuou soon nnlmnonm

.N.“ “

«onooo<

0~.0v0 a “no.0v0 te “no.0v0 not a

 

 

 

one no.nI I I I I I I I I I unoHIHm
on. oo.nI not m0.nI I I I I I I I I nuoam
to. —.n nn.0I 00.~I I I I I I I I >ou.no>
No.0 on mn.~ not mm.MI Nn.0I I I I I I I canon
Ho.0I Ho.0 on.0 o~.0I «m.~ I I I I I .ounh
~—.HI on.” no.0 ~N.0 not oo.~ oo.0 I I I I 00
om.o 00.0 a ~o.—I o5.0I no." u on.HI not m~.NI I I I 0:05
00.0 00.0 ~o.0 on.0I mo." no: on.~I not om.n on.0I I I ugnmq
n~.0I nm.0I No.0I 05.0 -.0I oo.0 n No.0I a mm.~ not o5.nI I aloe
on -.N as. ~H.NI 50.0 00.0 00.0 to m0.~ on on.~I o0.0I not ~0.nl a do.fi anuu.q
Hzmoxmzmam moqum Hzmoamzm mm>00¢wm> meaun wkwmmnmap 00 mnmh HmoHA uIHH
.A0-Ie0 some: nounxueom can no nooumneoo :nmu Hn>unm anuoo one nonuoenmno
noenomumenon vounouonnn one nuenmoouuoou eomunfioumou xenmIenIunoom .~.u u«onono<

H

OHCOIGOHH>¢0

neoan Ho>om

232

0~.0v0 s “n0.0vn no ”—0.0v0 not a

 

 

not om.nI I I I I I I I I I unnulam
can 5n.nI not nn.nI I I I I I I I I .nuosm
n no.~ 00.0 no. um.nI I I I I I I I >ou.no>
5n.0 No.“ not an.nI nn.o I I I I I I nuns:
«n.0I oN.0I oo.0 m0.~ oo.~I I I I I I .auaa
oo.~l not ~N.n a 05.-I o~.0 no an.N on.” I I I I 00
0N.0 0~.0I 0o.0I to on.“ oo.0 o~.HI one on.NI I I I nine
0 00.nl nn.0 50.0 . 00.nI to o~.u oo.0I tan oo.N not 00.NI I I van“;
o~.0 oo.0 05.0I a nn.~ mo.~l ~0.0 no.0l n—.0I s 50.~I I onus
th5HMN no ~0.~I an.0I oo.0 oo.0 on.0I on.0I mn.0 no.0I nn.HI mm
hzm0¢mzn=m m<qum szuumzm um>00.om> :Hmnn haunHuxah 00 0209 among mzHa

 

.Aoolnv noun: ununxunom ago no unouuneon .0on noeomuq unpunu van nuouosnunn
Hnueosnouupeo neoln anoa ouenuouuenun nounouonnn can nueomumuuooo nouunaouuoo unnulennunoom .o.u noononno

om.ova . "no.ova .. “mo.ova ... m

 

 

0m.0I I I I I I I I I I unoHImm
on: ~n.nI its 5o.~I I I I I I I I I .umouu
not nm.~ Nu.“ n5.0I I I I I I I I ooo.uo>
mm.o .. oo.~ ... mo.mI mo.o I I I I I I moaom
No.0 00.0 om.0 -.~ oo.0I I I I I I .omnb
om.~I oo.~ a no.u on.m o oo.0 «5.0 I I I I 00
oo.0I 00.0 o oo.~I 5N.0I m~.0I 00.~I so. 5m.mI I I I 0.09
no.0 nN.0I oo.~ no.0 o "0.0 om.0I not mn.n one no.nI I I unnua
no.0I 00.0I o0.HI o~.0I «n.0I no.0 no 0~.~I on n~.N n 5o.~I I vows
no.0I 00.0 om.0 m0.“ HH.HI no.0 00.0 a owhHI nH.~I 50.0 .mono
Hzmoxmznam m<qum ezmoxwzm xm>00.um> momma 55HOHnmap 00 0209 among mxnh

 

.Aoolnv noon: anunxueom ago no noouuneoo nwnmuoho Hn>unH one nuouosnuno
mnueoanoam>eo neoan Ho>om noenomumenmn vounooonnn nan nueoououunou nomunnouuoo xenuIenIunoom .n.u uwonooo<

233

0~.0v0 a “m0.0v0

no nH0.0v0 not ~

 

 

not om.nI I I I I I I I I I unoHIHm
not 5n.nI not nm.nI I I I I I I I I .nuoam
o 00.0 00.0 on: Nn.nl I I I I I I I >ou.wo>
5m.0 No.~ not ~m.nl nm.0 I I I I I I gonna
N0.0I o~.0I om.0 m0.~ oo.HI I I I I I .0009
oo.~l one -.n a 05.-I oN.0 to ~n.~ o~.~ I I I I 00
0N.0 0~.0I 0o.0I to 0m.~ oo.0 o~.~I not on.~I I I I 0809
o 00.~I mn.0 50.0 00.~I no oN.N oo.0I not oo.~ one 00.NI I I ucan
o~.0 om.0 ~5.0I t n0.~ ~0.~I Ho.0 n~.0I n~.0I n 50.~I I onus
no 5~.N an “C.NI ~n.0I 0m.0 oo.0 om.0I om.0I nn.0 m0.0I mm.~l mm
azmoxmznam m<quu Hzmozmzm ¢m>00.0m> :Hmmn whmnHmmae 00 0:09 Honq mth

 

.Aoolev noun: mounxunnm 000 no noduoneoo .000 nusomoq Hn>unH ven nuouoanuno

noenomuoenmn vounmoonnn van nueoouwuuooo eouunaomuou xenmIenlunoom

.o.m umocoaao

 

 

 

Anueoseouw>no meoen anonH

om.ova . n3.3a .. n8.3a ... m
om.oI I I I I I I I I I moumIma
not fim.MI not 50.NI I I I I I I I I .nmoam
... mm.m mm.m m».oI I I I I I I I .ou.mo>
mm.o .. oo.m ... mo.mI mo.o I I I I I I moaam
mo.o mm.o om.o mm.m oo.OI I I I I I .mnam
om.mI oo.m . mo.m om.m . oo.m ma.o I I I I on
oo.0I mo.o . oo.mI am.OI mm.OI oo.mI ... am.mI I I I as.»
mm.o mN.OI oo.m no.0 . mm.m on.OI ... mm.n ... no.mI I I ommmm
mm.oI mm.OI oo.mI om.OI mm.oI mm.o .. om.mI .. mm.m . ao.mI I oam»
no.0I mm.o am.o mo.m mm.mI mo.m on.o . oo.mI mm.mI ao.o .aa»o

ammommmmmm ammmIa mmmommmm mmaoo.om> m»amm »»mmmmmm» om azm» emomm mmm»
.AOCIcv £0.00: hvuwiucon— ozu a.“ nwfiuancov vacuhmhu HQ>MQH van mucuOEmumn
Homeoseoam>eo neosn Ho>om oocnomomcnmn onunmoonnn nan nueoHUHuuoou eomunflouaoo xenmIenImnoom .m.u uonnnooo

234

om.ova . “no.ova .. n8.8a ... m

 

on nn.NI I I I I I I I I I unoHIHm
on. oo.oI to. 0m.MI I I I I I I I I .nmosm
oo.0 ~o.0I oo.0I I I I I I I I boo.uo>
an." oo.0 at n0.NI on.0I I I I I I I gonna
no.0I -.0 0~.0 no.0I o5.0 I I I I I .nuna
0~.~I -.0 no.0 on n~.N m—.~ «0.0 I I I I 00
o0.~I o~.0 50.0 5n.0I no.0I ~o.~I ~N.0I I I I much
mo.mI om.o om.o oa.o am.o . on.mI am.oI ... no.n I I ummmm
on.~ 0n.0I no.0I o~.0I 5o.0 mm." at. 5n.~ on.0I one 05.~I I osmh
~m.0I oo.0I a on.“ 05.0 om.0I a. ~n.~ no om.~ H0.0I an.0 oo.0 0.2
azuuumznpm m<qum Hzmommzm xm>00.uw> manna woununuaa 00 0:05 Hmong mznh

 

anaconouopnn

neoen Ho>o~ ouenoouuenun wounuoonnn wen nunoaoouuooo noounaouuoo xnnuIenlunoom

.Amolnv some: mounauenm can no nnoumneow oxwo nooauuon unpuna wen nuouoenuno.

.o.u u

uwenoo<

00.0v0 n “no.0v0 to "H0.0vo not H

 

oo.o I I I I I I I I I muomIma
oo.o mm.o I I I I I I I I .maoum
.. mn.m no.m oo.m I I I I I I I .oo.moa
ao.o oo.m oo.o mo.o I I I I I I muaom
... aa.m om.m m~.o om.m .. an.m I I I I I .ma:»
mn.o mo.m oo.o oo.m mm.m »m.o I I I I on
mo.o mo.o on.m oa.o mn.o am.o mm.m I I I anus
om.m mo.o om.o mo.o am.o om.o mo.o cm.m I I ummmm
»m.o oo.o om.m mm.o om.o oo.o oo.o ... oo.m ... mn.n I oum»
mo.o am.o ... mm.m mm.m .. an.” mm.m mm.o om.m mo.o mo.m a.»
mmmommmmmm ammmIa ammommmm mmaoo.oma m»amm »»mmmmmm» om ammo mmomm mmm»

 

Haven-nomu>=o nnoan

.A5NIev Anon: mounrunom on» an noauoneow guano tendon Hopmnu wen nuouOInunn

Huang ouenuoumenon wounooonnn wnn unnumumuuooo nouunaouuoo xenuIenlunoom

.n.u u

ownnoo<

RIES

(l

 

"‘IIIIIIIIIIIIIII

I