—_—————
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some EFFECTS OF leAI; OPERATION _

6f DETROIT EDISON’S MONROE POWER ,

PLANT'ON FISH POPULATIONS or.
LAKE ERIE’S WESTERN'SHGRE AREA. ‘

Thesis for the Degree "of M. 8.;
MICHIGAN STATE UNIVERSITY
THOMAS JAMES EDWARDS

' 1973

.....

 

ABSTRACT

SOME EFFECTS OF INITIAL OPERATION OF
DETROIT EDISON'S MONROE POWER PLANT
ON FISH POPULATIONS OF LAKE ERIE'S

WESTERN SHORE AREA

By

Thomas J. Edwards

This study was designed to assess the effects of Operation of
Detroit Edison's Monroe power plant on fish populations found along the
western shore of Lake Erie near Monroe, Michigan. The power plant began
operation in May, 1971; and samples were collected from.May, 1971 to
June, 1972. This interval constitutes the postoperational sampling
period. Data were compared to those collected during a preoperational
period which included sampling dates from May, 1970 to November, 1970
summarized in a report by Parkhurst (1971).

Data from both pre and postoperational periods were collected by
replicate trawling at five stations located in the study area. Analysis
of variance and Duncan's Multiple Range Test were used to analyze
differences in species number, numbers of individuals, and biomass of fish
collected. Computer programs were used to evaluate growth characteristics
and coefficients of condition.

Fish distributions at the lake trawling stations showed occasional
significant changes after plant operation began. These changes were
considered to be the result of natural seasonal variation or sampling
error. Fish distributions at the plant's intake and discharge showed

highly significant and consistent changes in the postoperational period.

Thomas J. Edwards

In the discharge the number of species, number of individuals, and biomass
per trawl decreased. These variables increased significantly near the
intake. The changes in the discharge canal were attributed to thermal
instability and a general decrease in water quality of the discharge

canal environment. Increased oxygen concentrations near the intake

which resulted from cooling water drawn into the area from the lake,

is considered an important factor which led to increased fish use in

the river intake area.

Vertical gill nets set in the discharge canal have revealed a
general preference for the surface and intermediate depths. Regression
analysis has shown that this preference is apparently not related to
oxygen concentrations or temperature in the discharge canal.

Horizontal gill nets set near the mouth of the discharge and
at a control have not shown a significant vertical or horizontal response
to the discharge plume.

Growth characteristics for yellow perch (age classes I - V) and
young of the year yellow perch, gizzard shad and spottail shiners collected
at lake stations appear to be unaffected by power plant Operation.
Coefficients of condition (K factors) calculated for carp and gizzard
shad collected in the discharge canal were significantly lower than
fish of these species collected at the lake stations. Coefficients of
condition for goldfish were not significantly different between those

fish collected in the discharge canal and those collected in the lake.

SOME EFFECTS OF INITIAL OPERATION OF
DETROIT EDISON'S MONROE POWER PLANT
ON FISH POPULATIONS OF LAKE ERIE'S

WESTERN SHORE AREA

By

Thomas James Edwards

A THESIS

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

MASTER OF SCIENCE

Department of Fisheries and Wildlife

1973

ACKNOWLEDGEMENTS

I extend my sincere appreciation to all the peeple who helped in
the completion of this research: Dr. R. Cole, for his advice and guidance;
my committee members, Dr. N. Kevern, Dr. E. Roelofs, and Dr. P. Fromm
who willingly served as a committee member while Dr. J. Hoffert was on
sabbatical leave; Dr. W. Conley for his help in the statistical analysis
of the data. I owe a special thanks to my wife, Cheri, for her en-
couragement and review of the manuscript.

This study was supported by a grant from the Detroit Edison Company
to the Institute of water Research at Michigan State University. Use
of Michigan State University computing facilities was made possible

through support, in part, from the National Science Foundation.

11

TABLE OF CONTENTS

Page
INTRODUCTION 0 O O O O O O O O O O O O O O I O O O O O 1
DESCRIPTION OF THE STUDY AREA . . . . . . . . . . . . 3
MATERIALS AND METHODS . . . . . . . . . . . . . . . . 13
RESULTS 0 O O O O O O O O I O O C O O O O O O O O O O 17
Species Composition and Distribution . . . . . . 17
Statistical Analysis of Trawling Data . . . . . 23
Vertical Distribution of Fish in the Discharge
canal O O O O O O O O O O O O O O O O O O O O 38
Vertical Distribution and Movement in
Relation to the Discharge Plume . . . . . . . 40
Growth Characteristics . . . . . . . . . . . . . 41
Coefficient of Condition . . . . . . . . . . . . 42
DISCUSSION AND CONCLUSIONS . . . . . . . . . . . . . . 47
Fish Distributions . . . . . . . . . . . . . . . 47
Growth Characteristics . . . . . . . . . . . . . 51
Coefficient of Condition . . . . . . . . . . . . 52
SUMMARY OF CONCLUSIONS . . . . . . . . . . . . . . . . 55
LITERATLIRE CITE o o o o o o o o o o o o o o o o o o 0 56-59
APPEm IX 0 O O O O O O O O O O O 0 O O O O O O 0 O O O 60

iii

LIST OF TABLES

Table Page

1 Megawatt production of Detroit Edison's Monroe
power plant during August and November of
1971 O O O O O O O O I O O O O O O O O O O O O O 10

2 Periodic chlorine determinations made for samples
collected in the upper discharge canal of Detroit
Edison's Monroe power plant . . . . . . . . . . 12

3 The total numbers and biomass of fish species
captured along the western shore of Lake Erie
from May, 1970 to June, 1972 . . . . . . . . . . 18-19

4 Duncan's Multiple Range Test on the total number
of fish species caught at five trawling stations

located in the study area during 1970 and 1971 . 25
5 Duncan's Multiple Range Test on the total number

of fish caught at five trawling stations located

in the study area during 1970 and 1971 . . . . . 26

6 Duncan's Multiple Range Test on the total biomass
of fish caught at five trawling stations located
in the study area during 1970 and 1971 . . . . . 27

7 Analysis of variance results indicating signif-
icance of change that took place at each of five
trawling stations from 1970 to 1971. Dependent
variables considered are species number, number
of fish, and biomass . . . . . . . . . . . . . . 30

8 Duncan's Multiple Range Test on the total numbers
and biomass of the nine most abundant species of
fish caught at five trawling stations located
in the study area during 1970 and 1971 . . . . . 32-34

9 Back calculated increments and per cent growth
for yellow perch (age classes I - V) collected
in the study area during the 1970 and 1971
sampling periods . . . . . . . . . . . . . . . . 43

10 Maximum growth attained by the end of the 1970
and 1971 sampling periods for the young of the
year of three species collected in the study area,
and results of an analysis of variance between years
for each species . . . . . . . . . . . . . . . . 44

iv

List of Tables (con't)

Table

A-1

Page
Actual mean values for the number of species,
number of fish, and biomass (gms) collected
per trawl at each of five trawling stations
during 1970 and 1971 O O O O O O O O O O O O O O 60

Figure

LIST OF FIGURES

Page

A map of.the study area located along the near
shore area of western Lake Erie at Monroe,
MiChigan O O O O O O O O O I O O O O I O O O O O O 4

Oxygen concentrations in the Raisin River, dis-
charge canal and near shore areas of western
Lake Erie during 1970, 1971, and 1972 . . . . . . 8

Temperatures in the Raisin River, discharge
canal and near shore areas of western Lake Erie
during 1970’ 1971 and 1972 I O O I O O O O O O O O 9

Number of fish species collected per sampling
date in the study area 0 O O O O O O O O O O O O O 20

Number of fish collected per sampling date in
the StUdy area 0 O O O O O O O O O O O O I O O O O 2 1

Biomass collected per sampling date in the
study area . . . . . . . . . . . . . . . . . . . . 22

Relationship of per cent of fish caught (Y axis)

and depth (X axis) in the discharge canal. Eight
sampling dates from'May, 1972 to October, 1972

are included . . . . . . . . . . . . . . . . . . . 39

Coefficients of condition (K factors) for gizzard

shad, goldfish, and carp collected in the discharge
canal (+) and lake station (-) during the 1971

sampling period . . . . . . . . . . . . . . . . . 45

vi

INTRODUCTION

Lake Erie is undergoing accelerated eutrophication due to the
introduction of increased municipal and industrial wastes associated
with a growing population (Beeton, 1961). One of the most striking
changes to take place in the biology of Lake Erie has been in the relative
abundance of fish populations. Within the last fifty years the fishery
in Lake Erie has changed from one comprised of high value species to
a fishery made up primarily of medium and low value species. In spite
of this drastic change in species composition, fish production, as
indicated by commercial fishing records, has remained virtually un-
changed (Applegate, 1970). In terms of available fish biomass, Lake
Erie remains a valuable fishery resource.

It has recently been suggested that the fishery of aquatic environ-
ments may be damaged by an expanding electric power industry. A great
deal of laboratory data is available on the effects of temperature on
fishes. These data have been used as a basis for speculation concerning
the effects of thermal discharges on natural fish populations. Survival
times, reproductive capacities, growth and metabolic processes, and be—
havioral responses may be dependent on the thermal environment.

In spite of the amount of information available, there has been
relatively little conclusive research conducted at thermal discharge
sites. Because thermal discharges are usually open to fish migration,
unlike laboratory tests in closed systems, it is not clearly understood
what effect these thermal discharges will have on natural fish popula-

tions. But, public concern has frequently forced industry to consider

1

2
constructing expensive cooling alternatives such as cooling towers, cool-

ing ponds, and spray canals. It is usually apparent in these cases that
additional information about environmental effects is needed to justify
the extra expense of such alternate cooling methods.

The study described here was conducted in western Lake Erie in the
vicinity of Detroit Edison's Monroe power plant. Reported here are
data collected from May, 1970 to July, 1972. Data collected from May
to November, 1970 was summarized in a preoperational report submitted
in September of 1971 (Parkhurst, 1971). The purpose of this study is
to carry out and evaluate statistical comparisons between fisheries data
collected during the power plant's preoperational and postoperational
periods. Included are changes in fish distributions, growth characteris-
tics, condition factors, and behavioral responses. An evaluation is made
of the effect of initial operation of the Monroe power plant on these
characteristics of the fish populations in the study area. It should be
pointed out that during the period of early electrical generation which
is considered in this report, only one of four generating units was
in operation. All data presented apply only to this early period of

sub-optimal production from the Monroe power plant.

DESCRIPTION OF STUDY AREA

The study area (Figure 1) is located in the near shore area of
Lake Erie's western basin. The power plant, which will ultimately have
a 3200 megawatt production capacity, has been constructed immediately
south of the Raisin River's mouth. The plant's intake is located
approximately 1.5 kilometers upstream from the river mouth and cooling
water is drawn from both the river and lake. After passing through the
condenser system the cooling water enters the discharge canal and then
empties into the lake basin 2.4 kilometers south of the river's mouth.

The western basin of Lake Erie is characteristically shallow‘with
a mean depth of little more than 24 feet. Strong winds mix the waters
completely although temporary stratification has been reported several
times during an average summer (Carr, 1965). water transparency is
low because of the presence of suspended solids, highly turbid river
discharges, and a high concentration of phytOplankton. The low
transparency has remained essentially unchanged since Secchi-disc read-
ings of one to two meters were recorded in the summers of 1929 and 1930
(Beeton, 1961). Most of western Lake Erie has a mud bottom, although
extensive areas of sand are scattered through the basin (Applegate,
1970).

The Detroit and Maumee rivers undoubtedly have the greatest effect
on the water quality of the western basin, contributing approximately
982 of its volume. The effect of the Raisin River, although contributing
about 1% of the total, is probably significant. The BOD carried by the

3

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“a

   
   

Power Plant sm

Discharge (“m

 

IKIIII

.. /
//\   :':§:§§:§"lr:rm
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Figure 1. A map of the study area located along the near shore area

of western Lake Erie at Monroe, Michigan.

5
Raisin River is high; this in addition to high concentrations of nitro-

gen and phosphorus probably make the Raisin River a significant factor
contributing to the water quality near its mouth in spite of its rela-
tively low discharge.

As the Monroe power plant increases production and its heated plume
becomes more prominent, the local currents may become an important factor
concerning what effect the heated water will have on the area. Detroit
Edison Company personnel have studied currents in the study area. They
have found that direction of current is dependent on wind direction, and
velocities are dependent on water depths. It has been estimated that
mean monthly water movement is in a northerly direction at 0.5 to 1.5
km/day (Figure 1).

From 1930 to 1961 there have been drastic changes in species
composition, distribution and abundance of macroinvertebrates in Lake
Erie's western basin (Carr, 1965). Among those changes described were
increases in Oligochaeta, Tendipidae, Sphaeriidae and Gastropoda. During
this same period Hexageneidae were reduced to less than one percent of
their former abundance. Reductions in hexageneidae has been
attributed to thermal stratification and the subsequent reduction of
dissolved oxygen near the lake bottom (Britt, 1955).

Data collected from 1919 to 1963 have indicated that there have
been both quantitative and qualitative changes in Lake Erie's phytOplank-
ton populations (Davis, 1964). Over the years, phytoplankton maxima in
spring and fall have become more marked and longer while winter and
summer minima have become less marked and shorter. The diatoms, as
Davis points out, which once dominated the autumnal maxima, have been,

in part, replaced by species of green and blue-green algae.

6

Chemical characteristics determined throughout the study period of
1971 depict the study area as a highly enriched environment. The river
station was the most enriched area reflecting the municipal, agricultural,
and industrial effects on the Raisin River drainage. During the study
period of 1971 total phosphorus levels in the river averaged 0.28
mg/liter and ranged from 0.22 mg/liter to 0.36 mg/liter. Average total
nitrogen levels were found to be 1.89 mg/liter with a range from.l.26
mg/liter to 2.68 mg/liter. Suspended solids in the river ranged from
20.3 mg/liter to 77.7 mg/liter with an average of 44.41 mg/liter. The
lake environment had the lowest nutrient and suspended solids levels
in the study area. Total phosphorus levels averaged 0.11 mg/liter and
ranged from 0.07 mg/liter to 0.14 mg/liter. Nitrogen levels in the lake
were found to average 1.03 mg/liter and range from 0.50 mg/liter to 2.64
mg/liter. The average level of suspended solids in the lake during 1971
was 20.44 mg/liter; and the range was from 8.8 mg/liter to 45.7 mg/liter.
The discharge canal station which in 1971 was comprised of cooling water
pumped partially from the river and partially drawn in from the lake,
generally had nutrient and suspended solid levels which were intermediate.
Phosphorus values averaged 0.20 mg/liter and ranged from 0.13 mg/liter
to 0.27 mg/liter; nitrogen levels averaged 1.75 mg/liter and ranged from
1.06 mg/liter to 2.88 mg/liter; and average suspended solids were found
to be 35.9 mg/liter with a range from 16.7 mg/liter to 61.2 mg/liter.

Lake Erie's western basin was at one time fished heavily by
commercial fishermen. Today the high value species of the past have
virtually disappeared. Walleye and yellow perch are the major remaining
species of high and medium value. Populations of both of these species,
however, are declining (Anonymous, 1970). Populations of less valuable

fish are still represented in large numbers and are generally underexploited.

7

Included among these low value species are carp, goldfish and sheepshead.
Overfishing and a general degredation of the aquatic environment have

been cited as the causes for the major changes in fish populations in Lake
Erie. As a result of the loss of desirable fish species and the dis-
covery of high mercury levels in Lake Erie's fish, the western basin is
only infrequently fished commercially. A sport fishery continues in

the western basin, dependent primarily on populations of yellow perch,
white bass, catfish, and probably to some extent, carp, goldfish and
sheepshead.

When the plant began operation in May, 1971 certain environmental
factors changed immediately in areas most closely associated with the
operation of the power plant. Oxygen levels in the discharge canal
dropped from 1970 levels resulting from.the introduction of poorly
oxygenated river water (Figure 2). Surface water in the river remained
at a low level; however, in 1971 oxygen levels increased at the river
bottom because oxygenated lake water was drawn along the bottom by
pumps at the plant intake (Figure 2).

Temperatures were altered in the discharge canal where the maximum
value recorded was 33.5 C (Figure 3). Short term fluctuations as well
as increases in temperature were typical of the discharge canal environ-
ment after the plant began production. During 1971 electrical generation
was erratic because of mechanical difficulties and "shut downs" for
testing purposes (Table 1). Temperature data collected during 1971
showed that the change in temperature from intake to discharge (A t)
reached a maximum of approximately 11 C. Direct information on daily
fluctuations in temperature are not available. However, it can be
assumed that fluctuations in discharge temperatures vary directly with

changes in megawatt output, and that Table 1 represents erratic changes

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in temperature as well as in production. Data have been summarized for
one summer and one winter month to show that abrupt temperature changes
occurred in the discharge canal throughout the entire range of natural
seasonal temperatures.

The same trawling stations were sampled in 1971 that were sampled
by Parkhurst in 1970 (Parkhurst, 1971):

Station I (North Lake Station) was 2 km north of the discharge canal
and 100 meters off the beaches of Sterling State Park. The water depth
at this station was from 2 to 3 meters. The bottom was generally muck
with areas of sand interspersed.

Station II (Shoal Station) was 1.6 km directly off the mouth of the
discharge canal. The depth of the water at this station ranged from
1.5 to 2.5 meters. The bottom was sandy and with very little slope.

Station 111 (South Lake Station), the farthest station from the
discharge canal, was 6 km to the south and 1.6 km off shore. The water
depth ranged from 2 to 4 meters over a muck bottom.

Station IV (Discharge Canal Station) was located in the last kilo-
meter of the discharge canal. The water depth was from 3 to 8 meters and
the bottom was generally muck. When plant Operation began this station
was affected by the highly enriched and poorly oxygenated water pumped
from the river for cooling purposes. Chlorine was introduced into the
power plant's condenser system as an algacide. Table 2 represents
periodic chlorine levels determined in the discharge canal (provided by
Detroit Edison personnel). Sufficient water was being pumped to create
a flow in the discharge of approximately 26 m3/sec (482 million gallons/
day).

Station V (Raisin River Station) was located in the last kilometer
Of the Raisin River. The water at this station was from 6 to 8 meters

over a thick mucky bottom.

Table 2. Periodic chlorine determinations made for samples collected
in the upper discharge canal of Detroit Edison's Monroe power

 

 

plant.

Date - 1971 ppm1 Date - 1972 ppm1
6-24 0.52 1-6 0.05
6-29 0.42 1-7 0.05
7-1 0.52 1-12 0.10
7-6 0.42 1-14 0.20
7-8 0.72 1-21 0.30
7-12 0.52 1-27 0.35
7-15 0.15 1-28 0.50
7-21 0.152 2-1 0.35
7-23 0.152 2-3 0.35
7-27 0.22 2-8 0.25
8-10 0.23 2-10 0.25
8-17 0.15 2-15 0.20
8-20 0.20 2-17 0.20
9-3 0.15 2-22 0.20
9-10 0.752 2-24 0.40
9-15 0.13 2-29 0.40
9-17 0.13 4-11 0.50
9-22 0.13 4-20 0.3
9-25 0.05 4-27 0.10
9-28 0.053 5-2 0.07

10-12 0.053 5-4 0.05
10-15 0.05 5-9 0.06
10-20 0.2 5-11 0.04
10-22 0.05 5-16 0.07
10-27 0.1 5—18 0.12
11-1 0.05
11-11 0.10
12-7 0.70
12-14 0.25
12-16 0.05

MATERIALS AND METHODS

To compare data of pre and postOperational periods, an effort was
made to duplicate as closely as possible those methods described by
Parkhurst (1971). Trawl samples were taken with a 5 meter otter trawl
with 2.5 cm stretch mesh netting in the wings and 6 mm stretch mesh
netting in the cod end. Two Siminute replicate trawls at 1500 rpm were
made at each station at two week intervals. Each trawl covered about
1 km in length or approximately 0.5 hectare.

Because the discharge canal is considerably deeper than the lake
stations, the relative efficiency of trawling at that station was
questioned. To provide data on vertical distributions of fish in the
discharge canal, vertical gill nets were set beginning in the spring of
1972. The nets were set for approximately 10 hours during the night on
eight sampling dates fromfiMay 31, 1972 to October 28, 1972. Eight nets
were set on each sampling date. Each net was 8 meters long and two nets
of each mesh size 1/2 inch, 1 inch, 1 1/2 inch, and 2 1/2 inch bar were
used.

Horizontal gill nets were used in an attempt to provide information
concerning the response of fish to the discharge plume. Two nets were
used. One net was set just off the mouth of the discharge, the other was
set at the south lake station as a control. Each net was set where the
water depth was approximately 2 meters. Both nets measured 200 feet
by 6 feet, and each was made up of two sections. Each section was

comprised of four equal areas of mesh sizes 1/2 inch, 1 inch, 1 1/2 inch

13

l4
and 2 1/2 inch bar. It was presumed that when the heated discharge
spread out over the surface of the lake, avoidance or attraction responses
could be evaluated on the basis of the vertical position at which fish
were caught. The nets were set at night to eliminate the effects of
light on vertical distribution. It was also thought that the prevalent
direction of movement when the fish were caught could reveal an attraction
to or avoidance of the discharge canal.

Only the large carp, goldfish and gar were processed in the field.
All other fish were preserved with formalin and returned to the lab for
further study. All fish were measured (total length) and weighed.

Record was made of the number of species, number of fish and biomass
collected per trawl at each station on each sampling date. In addition,
scale samples were taken from all the major species of fish defined by
Parkhurst (1971).

Impressions of scale samples were made on cellulose acetate (Smith,
1954). Age and growth relationships were determined by measuring the
distance from the origin of the scale to each annulus and to the margin
of the scale. Following the technique used by Parkhurst (1971), annulus
formation was assumed to occur on January 1. All fish collected after
January 1 and before the time of actual annulus formation were credited
with an annulus.

The age and growth relationships for yellow perch were determined
using a computer program designed by Hogman (1970). The program computed
lengths corresponding to each annulus using the Lee-Lea formula,

(L

t - a) Sn

SI:

L 8 a +
n

where Ln equals length of fish at annulus n, Lt equals fish total length,

3 equals the total length intercept of the body-scale equation, St

15
equals the total scale diameter, and Sn equals the scale diameter at
annulus n.
The coefficient of condition (K) was calculated as described by
Carlander (1969),

K.= w'x 10

L3

where w is the weight of the fish in grams, and L is the total length of
the fish. The K factor is an index of "robustness" of an individual
fish. The value of K has been used in this study as an indicator of
habitat suitability during 1971. It was desired to make a comparison
between the K factors characteristic of fish in the discharge canal

to those characteristic of fish of the same species found in the lake.
For this reason the number of fish used in the analysis was limited by
the relatively low fish catches in the discharge canal during the 1971
sampling period. The three species caught most frequently in the dis-

charge canal, carp (Cyprinus carpio), goldfish (Carassius auratus), and

 

gizzard shad (Dorosoma cepedianum) were used for the statistical compari-
son of K factors. Those fish caught in the discharge canal were first
grouped into classes according to length (10 cm intervals for carp and
goldfish, 2 cm intervals for gizzard shad), and month of capture.
Comparisons were made on the basis of equal numbers of fish from each
class selected randomly from the lake stations. Sexes were combined for
analysis of all three species considered.

A computer program for analysis of variance was utilized for
statistical analysis of trawling data. The analysis was designed to
detect significant differences in replicate trawls, sampling dates and
stations in respect to species numbers, numbers of fish, and total bio-

mass collected per trawl. Tests were run on the total number of fish

16

collected per trawl, and in addition individual tests were run for each
of the nine major species.

It was found necessary to transform raw data in order to meet the
required assumptions of an efficient analysis of variance. Data con-
cerning numbers of species were transformed using square roots. Total
numbers of fish and total biomass data were transformed using common
logarithms. All data from.May, 1970 to November, 1971 were transformed
before comparisons were made. All mean values presented in the various
tables of this report are based on transformed data. The corresponding
means based on raw data are given in the appendix. The distributions
of raw data were often highly skewed because of the incidental capture
of large fish or the occasional capture of unusually large numbers of
fish. For this reason the means of raw data do not always indicate
the same relationships between stations as do means of transformed data.
Means based on transformed data are considered the best possible repre-
sentation of the relationships existing between stations in terms of num-
ber of species, number of fish, and biomass collected per trawl. All
comparisons made are based on 10 comparable sampling dates from each
sampling period.

A Duncan's Multiple Range Test was used to establish specific
differences when differences were found, by analysis of variance, to be

significant.

RESULTS

Species Composition and Distribution

 

During the period from May, 1971 to June, 1972 a total of 8,735
fish were collected by trawling from the five sampling stations (Table
3). This total is made up of twenty-four different species of fish
representing 11 different families. Analysis of variance indicates
that there was no significant difference between replicate trawls in
the number of species, total number of fish, and total biomass collected
per trawl. There were, however, significant differences between sampling
dates attributed to natural seasonal variations. Also significant
differences existed between sampling stations.

Data collected on species numbers, number of fish, and biomass
have been summarized in Figures 4, 5, and 6 to illustrate the changes
that have taken place since the power plant began operating in May,
1971. Average values are given for the three lake stations. The
discharge canal and river stations are shown separately. These data
are subject to considerable variability resulting from natural seasonal
changes in the intensity of fish use of the area and the unavoidable
variation inherent in the sampling technique. Biomass data are further
subjected to variation caused by the incidental capture of small numbers
of large fish such as carp and goldfish. Even with its high inherent
variability, raw data such as these do reveal real changes that occurred
at specific stations from 1970 to 1971.

Values for the combined lake stations remained realtively constant

throughout 1970, 1971 and early 1972. Because of the relatively small
17

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23

amount of production by the power plant and the distance from the lake
stations to the mouth of the discharge, it is safe to assume that these
stations were not directly affected by plant operation. Figure 5 shows
distinct changes in fish use of the discharge canal from 1970 to 1971.
In 1970 the newly dredged discharge canal yielded relatively large
numbers of fish per trawl. However, in 1971, after plant production
began, trawling data indicate an 80% drop in the number of fish using
the discharge canal. This drop in numbers of fish is also reflected

by a less obvious decline in biomass (Figure 6). However, change in
biomass may not be as distinct as change in fish numbers because large
carp and goldfish continued to be captured. The average number of fish
species collected per sampling date from the discharge canal decreased
from approximately nine species in 1970 to approximately five species
in 1971. It may appear from these data that there were fewer species
inhabiting the discharge canal in 1971. This drop in mean species num-
ber per trawl, however, may have resulted from a decreased efficiency
of the sampling technique under conditions of low fish density.

Because of the low water quality of the Raisin River, trawling at
the river station produced fish on only three of the sampling dates in
1970. During 1971 catches of fish in the river were considerably more
consistent and trawling produced fish on all but one sampling date. The
river station, however, continued to yield the lowest numbers of species,
numbers of individuals and total fish biomass of any of the trawling

stations.

Statistical Analysis of Trawling Data
An analysis of variance was applied to separate data collections

from 1970 and 1971. Significant differences were found to exist between

24
stations (p < .05) when each of three dependent variables were considered;
species number, number of fish, and biomass collected per replicate trawl.
A Duncan's Multiple Range Test was carried out to reveal where the signif-
icant differences between stations existed. These data are summarized
separately for 1970 and 1971 in Tables 4, 5 and 6. These means from
transfonmed data are used to illustrate, as precisely as possible, the
relationships that exist among stations and do not represent exact mean
values of the raw data which can be found in the appendix.

In 1970 the north lake station (Station I) was not significantly
different from those stations that produced the greatest mean numbers
of species, number of fish, and biomass. This relationship continued
in 1971 for each variable. Even though it has been established that
local currents would generally carry the discharge plume toward the
north lake station, it appears that this station is located far enough
from the mouth of the discharge canal to be unaffected by the heated
plume.

In 1970, Station 11 generally represented an intermediate position
between the high catches at the other lake stations and in the discharge
canal and the consistently low catches in the river. In 1971 Station 11
'was not significantly different from the highest yield of numbers and
biomass characteristic of Station I and II. This data suggests an
increase in fish use at the shoal station during the sampling period of
1971.

The highest mean numbers of fish were found at the south lake station
(Station III) during both years. Located about six kilometers from the
mouth of the discharge canal, the south lake station is the most distant

from the discharge plume, and probably is unaffected by it. During both

25

Table 4. Duncan's multiple range test on the total number of fish
species caught at five trawling stations located in the study
area during 1970 and 1971.

 

Number of Species 19701
Stations2 V II III IV I
Means3 0.57 5.54 6.08 6.24 7.11

 

 

Number of Species 1971
Stations V IV 11 I III

Means 1.81 2.68 5.43 7.48 7.92

 

 

 

1From Parkhurst (1971).

21 a North Lake Station; II - Shoal Station; III - South Lake Station;
IV - Discharge Canal Station; V - Raisin River Station.

3Mean value per trawl based on transformed data used to meet the required
assumptions of the analysis of variance carried out. Means not under-
lined by the same line are significantly different (P < .05).

26

Table 5. Duncan's multiple range test on the total number of fish caught
at five trawling stations located in the study area during 1970

 

 

and 1971.
Total Number of Fish 19701
Stations2 V II IV I III
Means3 1.95 29.24 47.09 66.97 68.38
Total Number of Fish 1971
Stations V IV II I III
Means 6.09 6.63 46.23 67.37 71.73

 

 

 

1From Parkhurst (1971).

21 a North Lake Station; 11 - Shoal Station; III - South Lake Station;
IV - Discharge Canal Station; V - Raisin River Station.

3Mean value per trawl based on transformed data used to meet the required
assumptions of the analysis of variance carried out. Means not under-
lined by the same line are significantly different (P < .05).

27

Table 6. Duncan's multiple range test on the total biomass of fish
caught at five trawling stations located in the study area during
1970 and 1971.

 

Total Biomass (gm) 19701
Stations2 V II III I IV
Means3 4.81 723.55 1551.57 4330.60 4584.00

 

Total Biomass (gm) 1971

Stations V IV II I III

Means 64.75 197.83 1071.73 2568.68 3113.71

 

 

1From Parkhurst (1971).

21 a North Lake Station; 11 - Shoal Station; 111 - South Lake Station;
IV = Discharge Canal Station; V - Raisin River Station.

3Mean value per trawl based on transformed data used to meet the required
assumptions of the analysis of variance carried out. Means not under-
lined by the same line are significantly different (P < .05).

28

years the number of species collected at the south lake station was not
significantly different from those stations that produced the highest
yields in that respect. The relative increase in biomass at the south
lake station in 1971 reflects capture of greater numbers of larger
fish and does not indicate a change in fish use in that area.

As indicated by bottom trawls, the discharge station (Station IV)

was the only one of the five stations to undergo a merked change, rela- 4
W, 5‘I

tive to other stations, from 1970 to 1971. In 1970 the discharge canal i

was consistently among those stations that yielded highest values for g

species number, number of fish and biomass. During the 1971 sampling
period, the numbers of species and numbers of fish caught in the dis-
charge canal drOpped to such an extent that there was no significant
difference between the discharge canal and the Raisin River. The biomass
for the discharge canal also dropped drastically in 1971 when it exceeded
only those biomass levels found in the river.

The river (Station V) showed increases in transformed mean values
for each of the variables considered. However, it still yielded the
lowest numbers of species, number of individuals, and biomass collected
during the entire sampling periods of 1970 and 1971.

The data presented have illustrated the relationships that existed
between stations within each of two separate sampling periods during
1970 and 1971. Although useful in comparing relative changes within
sampling periods, this type of analysis does not represent a direct
statistical comparison between conditions existing at a given station
from one sampling period to the next. To provide this information an
additional analysis of variance was used. The test was carried out for
each station individually and was designed to reveal which stations had

changed significantly from the preoperational to postoperational periods

29
and to indicate the extent of change. Again, the three dependent vari-
ables considered were species numbers, numbers of fish, and biomass.
Results of this analysis are given in Table 7.

Among the lake stations, the north lake area did not show significant
changes with respect to any of the variables considered. The fish use
at the north lake station, as indicated by bottom trawls, has therefore
remained unchanged over a period of time that began one year before
power plant operation. However, the shoal and south lake regions did
exhibit significant changes from 1970 to 1971 in respect to certain
variables. The shoal station showed a significant increase in the number
of fish caught per trawl in 1971 while species numbers and biomass re—
mained similar to those values reported in 1970. For the south lake
station species number and biomass increased significantly, while the
number of fish caught per trawl has remained unchanged.

The discharge canal and river, the two areas directly associated
with the Operation of the power plant, were the only stations that
revealed consistent and highly significant changes from 1970 to 1971
in respect to all variables concerned. Fish use in the discharge canal,
as indicated by bottom trawl data, decreased from 1970 to 1971. This
decrease in fish use was evident for species number, number of fish,
and biomass collected per trawl. All decreases were statistically highly
significant (p < .005).

The changes found in the river were exactly opposite from those
found in the discharge canal. The fish use at the river station indi-
cates significant increases from 1970 to 1971. The increase was expressed
in higher numbers of species, numbers of individuals and biomass caught

per trawl. Again, each increase was highly significant (p < .0005).

‘L

Pun—n
I

‘41

30

Table 7. Analysis of variance results indicating significance of change
that took place at each of five trawling stations from 1970

to 1971.

number of fish, and biomass.

Dependent variables considered are species number,

 

 

 

 

 

 

Station Species Number Fish Number Biomass
North Lake (1) 0.6121 0.982 0.249
(1970 x 1971) Increase2 Increase Decrease
52 12 412
Shoal (11) 0.850 0.009* 0.501
(1970 x 1971) Decrease Increase Increase
21 58% 48%
South Lake (III) 0.003* 0.810 0.013*
(1970 x 1971) Increase Increase Increase
30% 5% 1012
Discharge Canal (IV) .0005* .0005* .0005*
(1970 x 1971) Decrease Decrease Decrease
57X 862 962
River (V) .0005* .0005* .0005*
(1970 x 1971) Increase Increase Increase
2182 2122 12462

 

1

Significance of F statistic.

2Observed trend and per cent change from

3Accepted as a significant change.

1970 to 1971.

31

In 1971, as in 1970, nine species accounted for a substantial
majority of the total numbers of fish and total biomass collected from
all stations. In 1970 these species comprised 97.5% of the total numbers
of specimens and 90.32 of the total biomass. In 1971, 97.1 and 95.1
were the respective percentages for numbers of fish and biomass collected.
Parkhurst (1971) evaluated the habitat preferences of these nine species
and separated them into three categories. The first category included
yellow perch, white bass, emerald shiners, spottail shiners and alewives.
These five species preferred the lake stations over the discharge canal
and river. The second category was comprised of sheepshead, carp, gold-
fish, and the carp—goldfish hybrid. These species generally preferred the
discharge canal as well as the north and south lake areas. The gizzard
shad was the only species representing the third category of universally
distributed species found at all stations.

The distributions of each of these individual species have been
determined, from trawling data, for the 1971 sampling period. After an
analysis of variance was applied to each species during each year (1970
and 1971), the means were ranked and significant differences were deter-
mined with a Duncan's Multiple Range Test. These data are summarized in
Table 8 which is intended as a further, species specific, illustration
of the relative changes in fish populations that occurred in the study
area after plant Operation began.

During 1970 yellow perch were most abundant at the north and south
lake stations. Consistent but low catches were reported at the shoal
and in the discharge canal, while they were rarely caught in the river.
During 1971, the lake continued to yield the highest numbers and biomass
of yellow perch, but in both instances the north lake station yielded

less than during the previous sampling period. The catch of yellow perch

32

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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34

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35
at the shoal station increased to the point that its catches were consis-

tent and relatively high. The discharge canal which provided low but
consistent catches in 1970 did not differ significantly in 1971 from
the very infrequent catches in the river.

White bass in 1970 were more typically caught at the three lake
stations. There was no significant difference between the catches of
the lake stations with respect to both numbers of fish and the biomass.
The next highest yields of white bass in 1970 came from the discharge
canal which was not significantly different from the high catches at the
shoal and south lake stations in respect to numbers of fish. It also
was not significantly different from the south lake station in terms of
biomass collected. The river produced only extremely inconsistent
catches of very low numbers of white bass during 1970. The 1971 sampling
period again shows the three lake stations yielded the highest numbers
and biomass of white bass. The decrease in numbers of fish caught at
the shoal station represent what is probably an incidental drop in the
catch of young of the year fish. This would explain the continued high
yield of biomass relative to the other lake stations. The discharge
canal, which was not unlike certain lake stations in its high catches
of white bass in 1970, decreased significantly in 1971. During 1971
the discharge canal was not significantly different from the river
station which continued its almost negligible yield of white bass typical
of the 1970 sampling period.

Emerald shiners were found only infrequently in the river and dis-
charge stations during 1970. This species definitely preferred the lake
stations and was most abundant at the south lake station followed by the
shoal station and the north lake station. Catches were quite variable

at all stations. In 1971 the distribution of emerald shiners was generally

36
similar to the 1970 sampling period. The use of the river and discharge

stations by this species was again low and there were no significant
differences in the two stations in this respect. During the 1971
sampling period emerald shiners continued to show a marked preference
for the lake stations. However, in 1971 there were no significant
differences found among lake stations concerning numbers or biomass of
emerald shiners collected. Catches of emerald shiners continued to be
highly variable in comparison to those of the spottail shiners.

Like the emerald shiners, the spottail shiners preferred the lake
stations during 1970 and 1971. Data collected for each sampling period
indicate that there was no significant difference among lake stations in
the amount of use each received by the spottail shiner. During 1970
the discharge canal represented an intermediate position concerning
numbers and biomass collected, while the river was significantly lower
in this respect than any of the other stations. The relationship of
the discharge canal station to the remaining stations changed during 1971
when the canal yielded the low numbers and biomass which had been
previously characteristic only of the river.

Sheepshead distinctly preferred the discharge canal as well as the
north and south lake stations during 1970. During this period no sheeps-
head were captured in the river station and few were taken at the lake
shoal. In 1971 the highest catches of sheepshead were still taken at
the north and south lake stations. However, the relatively high pro-
ductivity characteristic of the discharge station before 1971 had dropped
considerably and was not significantly different from the river station
after plant operation began. Also, in 1971, the shoal station increased
its yield of numbers and biomass of sheepshead and was similar to the north

lake station during that period.

37

Carp, during 1970, were caught more extensively in the discharge
canal than any other station although the north lake station was not
significantly different in this respect. All other stations provided
very low catches of carp throughout the sampling period. In 1971 the
catch of carp in the discharge canal was reduced to such an extent that
in terms of numbers of fish and biomass collected it was not signifi-
cantly different from the river and shoal stations which had been typically
avoided by carp throughout both sampling periods. The south lake station
provided significantly greater biomass of carp while numbers of carp
remained the same. This is likely the result of the capture of some
unusually large specimens at this station during 1971.

Trawling data for 1970 show that the goldfish, more than any other
species, was closely associated with the discharge canal. Numbers of fish
and biomass collected were significantly higher in the discharge canal
than in any of the other stations. Intermediate catches were typical of
those at the north lake station. The river, shoal and south lake stations
provided considerably lower catches. Comparing the 1971 data to that
of the previous 1970 sampling period, it appears that the discharge canal
is the only station that has obviously changed in respect to numbers of
goldfish caught. The discharge canal has been reduced from the highest
producer of goldfish to one of three stations representing the lowest
yield of this species. As a result of the decrease in numbers of fish
caught at the discharge canal, the north lake station was the most pro-
ductive source of goldfish during the sampling period in 1971.

Gizzard shad in 1971 were collected in considerably fewer numbers
than during the sampling period in 1970. There were also significantly
greater numbers of fish caught in the discharge canal during 1970 than

at any of the other stations. Intermediate size catches were taken

38

at all three lake stations while the river catches were significantly
less than at any other station. In 1971 the overall decrease in giz-
zard shad numbers was proportionately greater in the discharge canal.
This, accompanied by an increase in gizzard shad caught in the river,
resulted in all stations being statistically similar in respect to
numbers of fish caught. This same general relationship is shown for
biomass data; however, the north lake station remains significantly
different from the south lake and discharge canal stations concerning
biomass collected. Although there were changes in relative and total
abundance, gizzard shad still exhibited a universal distribution in

1971.

Vertical Distribution of Fish in the Discharge Canal

Vertical gill nets were set overnight on eight dates from May 31
to October 28 of 1972. During this period 786 fish representing 14
species were collected. Those species generally caught with the bottom
trawl were also caught in considerable numbers with the vertical gill
nets, but the gill nets were less efficient at capturing spottail and
emerald shiners presumably because of the small size of these species.

Gizzard shad and longnose gar tended to prefer surface waters more
than other species but otherwise there was not a great deal of difference
in the preferred depths of the different species. All species tended
to avoid the bottom and preferred the intermediate depths and the sur-
face. In terms of total numbers of fish caught with vertical nets, 100
(12.7%) were caught at the bottom two meters, 260 (33.1%) were caught at
intermediate depths, and 426 (54.2%) were caught in the upper two meters
of the discharge canal.

Regression analysis of percentage of fish caught against depth

(Figure 7) revealed a highly significant negative regression (p < .001).

39

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.Hmcmo omumcomfiw mnu cw Amwxm xv nuemw mam Awake NV unwsmo Swan mo ucmo use mo awnmsoaumaom .n muamwm

.832... :23

 

a h o n Q n N —
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o o
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40

The per cent of fish caught decreased significantly with an increase
in depth.

In an attempt to provide an explanation for the vertical distri-
butions of fish in the discharge canal, oxygen and temperature profiles
were determined on each date vertical gill nets were set. The water in
the discharge canal appeared to be well mixed with temperature and
oxygen levels relatively constant from tap to bottom, although these
levels did vary considerably between sampling dates. Regression analysis
was also carried out on data concerning per cent of fish caught in
relation to both oxygen and temperature levels. No significant regres-
sion existed between the per cent of fish caught and either of these

two variables.

Vertical Distribution and Movement in Relation to the Discharge Plume
Horizontal gill nets were set at night on five dates from'May 17,
1971 to October 30, 1971. The nets were set only when the power plant
was operating and temperature of the discharge water was noticeably
above ambient lake temperature. All of the major species were well
represented at both the discharge and the control station, and differences
in species composition between the two stations is not considered a
variable factor affecting overall vertical distribution of fish. It was
thought, however, that the heated plume would spread out over the sur-
face of the lake near the mouth of the discharge and this stratification
could influence the vertical distribution of fish in the immediate area.
Throughout the study period a mean of 70.85 per cent of all fish caught
in the discharge plume were taken in the upper half of the gill nets.
At the control station a mean of 57.75 per cent of the fish caught were

found in the upper half of the nets. This suggests a possible preference

41

for the heated surface water in the area covered by the discharge plume.
However, an analysis of variance was carried out on the experimental
data and this difference was found not to be significant.

If the increased temperatures in the discharge canal had created
a habitat which was either preferred or avoided by fish species in the
area, this response may be indicated by predominant movement toward or
away from the discharge mouth. The direction of movement at capture
was recorded for each fish caught at both the plume and control areas.
Of the total number of fish caught in the discharge plume 39.1 per cent
were moving toward the mouth of the canal. At the control station 42.5
per cent of the fish caught were moving in a similar direction. This
relationship between plume and control station varied among sampling
dates. From these data it was determined that the two stations did not
differ significantly in respect to direction of fish movement and that
sampling with gill nets over a short duration has not revealed any

characteristic response to the discharge plume.

Growth Characteristics

It was originally planned that age and growth characteristics of
fish found in the discharge canal could be compared with those for the
same species found at the lake stations. In this way it would be possible
to estimate the effects on growth that the habitat of the discharge canal
had on various species of fish. However, during the 1971 sampling period,
all species in the discharge canal were caught in insufficient numbers
to accurately establish an age and growth relationship.

Yellow perch were the most frequently caught species in the study
area during both the 1970 and 1971 sampling periods, and this species

provides the greatest amount of data available on fish growth characteristics

42

of the lake stations. A body-scale relationship was determined using a
random sample of 963 perch which represented age classes 0 through VI.
The body-scale relationship was found to be linear for sexes combined
with a correlation coefficient of 0.895. The back calculated increments
for growth in length for individual age classes as well as per cent of
total growth achieved for age classes I through V are shown in Table 9
for each sampling period. Increments of growth and per cent growth
achieved at each age class are similar for both sampling periods; and
the Operation of the power plant appears not to have influenced growth
characteristics of yellow perch in the lake proper.

If a change in environmental conditions due to power plant operation
were to effect growth of fish, that effect would likely be most evident
for the young of the year when the increment of growth is generally
greatest. Mean lengths attained by the end of the sampling period
(October to November) were determined for young of the year fish of
three species for both 1970 and 1971. These data as well as results of
an analysis of variance between years for each species are presented in
Table 10. The data indicate that there were no measured significant
differences in maximum attained growth between sampling periods for young

of the year yellow perch, gizzard shad, and spottail shiners.

Coefficient of Condition

 

Coefficient of condition data were computed for carp, goldfish,
and young of the year gizzard shad caught in the discharge canal and at
the north lake station (the north lake station is used here as a control).
These species were caught with the trawl in sufficient numbers at both
stations to provide data for a comparative study. Calculated coefficients

of condition (Figure 8) for mature carp from the north lake station were

43

Table 9. Back calculated increments and per cent growth for yellow
perch (age classes I-V) collected in the study area during the
1970 and 1971 sampling periods.

 

 

 

 

1970
Age Class I II III IV V
Increment
Growth (mm) 73 61 38 22 17
Per Cent Total
Growth 32.4 60.0 79.5 89.5 94.5
1971
Age Class I II III IV V
Increment
Growth (mm) 81 56 38 21 17

Per Cent Total
Growth 35.6 60.2 77.3 86.5 94.1

 

44
Table 10.

Maximum growth attained by the end of the 1970 and 1971

sampling periods for the young of the year of three species
collected in the study area and results of an analysis of

variance between years for each species.

 

 

 

 

1970 1971
Maximum Standard Maximum Standard
Growth (mm) Error Growth (mm) Error
yellow perch ‘94.9 2.40 92.1 2.42
gizzard shad 119.0 3.79 113.1 3.98
spottail shiner 86.7 1.18 87.0 0.98
ANOVA Results (1970 x 1971)
F Statistic Degrees of Confidence
Freedom
yellow perch 0.69 NS1 22 .25 - .50
gizzard shad 1.12 NS 44 .25 - .50
spottail shiner 0.31 NS 88 .50 - .75

 

1Not significant, i.e.: there is not a significant
lengths between years.

difference in fish

45

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oouooflaoo mums was .smamoaow .vonm vumuuww you AmHOuomm xv coaufiocoo mo muooaoammooo .w ouowfim

”9:37:0sz 4<b0h A80. IFGZNJ ._<._.O._. .53 15.02%. ._<.—.O._.

 

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46
significantly higher than those from the discharge canal station (p <

.01). Coefficients of condition calculated for mature goldfish did
not differe between the two stations. Young of the year gizzard shad
differed most between the two stations and had a significantly higher

coefficient of condition at the north lake station (p < .001).

E

_-.- .-‘—

 

DISCUSSION AND CONCLUSIONS

Fish Distribution

 

In 1971 the relationship of the river, with its poor water quality,
to the discharge canal is important. Prior to this period the discharge
canal was comprised of relatively stagnant lake water. In 1971 the power
plant created a flow in the discharge which was comprised largely of
river water used for cooling. Mean temperatures in the discharge canal
increased as the heated effluents were released. Oxygen in the dis-
charge canal decreased in response to the rise in temperature and poor
quality of the river water. Oxygen at the river bottom increased as
a result of lake water being drawn toward the plant's intake.

In 1971 the relative distributions of fish in the study area
appeared to have been influenced by power plant Operation. The total
abundance of fish in the study area during 1970 and 1971 changed very
little from 1970 to 1971. After the plant began Operating fish appeared
to redistribute themselves within the study area rather than move in or
out .

Changes in the relative abundance of fish and the numbers of species
were most Obvious in the discharge canal in terms Of actual numbers or
weight per trawl, but on a percentage basis the river changed most in
the relative abundance of fish. Changes found at the lake stations were
intermediate and apparently real in terms of actual change in abundance.

Superficially, the data may suggest that increased fish use at the

river, shoal, and south lake station may have resulted primarily from a

47

arr-.3 .
r

48

redistribution of those fish repelled by the discharge canal environment
in 1971. This is unlikely, however, because total evacuation of the dis-
charge canal, with its relatively small area. could not measurably
increase fish abundance throughout the much larger lake study area. It
is possible, however, that some increases in fish use at the river and
shoal stations occurred as a result of redistribution of fish repelled
by the power plant discharge. But, since the south lake station is
located several kilometers from the discharge, it is unlikely that the
increase in fish abundance in that region is in any way related to power
plant Operation.

It is more likely that increases in fish abundance at the south
lake station were caused by normal annual variations of fish distribution
in the lake. It is also possible that normal annual variations were in
part responsible for the significant but relatively small increases in
abundances at the river and shoal stations, although it is likely that
increased oxygen concentrations in the river, caused by plant operation,
were an important factor determining fish use in this area. Fish abun-
dance may have increased at the shoal station in response to increased
enrichment and food concentrations carried there by the discharge plume.

Changes in the discharge canal were so much more marked than changes
in the lake that it is improbable that normal annual variation completely
explains the Obvious aversion of bottom waters by fish after the plant
began operating. A number of possible changes could have caused the aver-
sion which could have resulted from a migration toward the surface or
away from the bottom where trawling is effective.

Vertical distributions of fish in the discharge canal according
to catches made with vertical gill nets in 1972 indicated preferences for

intermediate and surface depths. Gill netting was conducted overnight

49

to negate the effect of daylight on vertical distribution. Data on
vertical gill netting during the day when trawling was done is not
available so it is not known that distributions changed daily. The
relatively small temperature variation with depth and oxygen variation over
4 mg/liter had no apparent influence on vertical distributions of fish
according to regression analysis. There is no direct evidence that the
same kind of vertical distributions that existed in 1972 could not have
also existed in 1970 and 1971.

The low oxygen concentrations in the discharge canal during 1971

 

were lower than when vertical gill nets were set in 1972 because river
water comprised more of the discharge water in 1971. Although some
argument exists (England, 1971), there is otherwise a general consensus
(Whitmore, warren and Doudoroff, 1970; Jones, 1952) that fish can avoid
low concentrations of oxygen. This suggests that low oxygen concentrations
may have been a causative factor leading to low trawl catches in the dis-
charge canal due either to a complete avoidance of the canal or an
avoidance of the lower oxygen levels at the discharge bottom. Undoubted-
ly oxygen reached low enough concentrations in the summer of 1971 to
exceed the tolerances Of some fish species (yellow perch and sheepshead)
investigated by Doudoroff and Shumway (1970). However, the continued

low trawl catches in the autumn of 1971, when oxygen concentrations had
returned to levels comparable to 1972, indicates that fish distributions,
both horizontal and vertical, were not solely dependent on oxygen. This
also suggests that relative trawling efficiency during 1971 was not
highly dependent on vertical fish distributions due to oxygen concen-
trations and that the indication of a general avoidance of the discharge

canal is apparently valid.

50

Chlorine is applied regularly (four times daily during most of the
year) and concentrations of total residual chlorine at the upper end of
the discharge canal frequently surpassed those advised by Brungs (1973).
No fish kills, other than scattered individuals, were observed during
1971. Therefore, chlorine concentrations were apparently not high enough
to cause obvious harm to fish. But regular chlorine use could have
reduced the attractiveness of the discharge canal to fish. This could
also be true of a number of possible contaminants in the Raisin River
water .

Those fish caught in considerable numbers in the discharge canal
before plant Operation began appeared to avoid the discharge canal during
cold as well as warm parts Of the year in 1971. This is in contrast to
reports of other investigators who Observed aversion only in summer and
attraction during the cooler months (Agersborg, 1930; Gammon, 1970;
Roessler, 1971; Coutant, 1972; and Merriman, 1972). Pitt (1954) and
deVlamming (1970) have revealed that mature fish Of at least certain
species can orient to temperature gradients and move toward a preferred
temperature. But fish apparently did not respond to temperature gradients
in the discharge canal even when preferred temperatures existed in the
fall of 1971.

Stable sublethal stresses (low oxygen, chlorine, other toxins, or
heat) can be expected to influence species populations differentially,
some species being more tolerant to various stresses than others. However,
Operation of the power plant in 1971 seemed not to have a strong differ-
ential effect on those species inhabiting the discharge canal before plant
Operation began. The responses of these species considered in total sug-
gests that no single continuous stress was responsible for the avoidance

of the discharge bottom waters after plant Operation began. It is more

mumj‘
3‘ I

'W—

51

likely that most fish avoided an intolerable intermittant stress.
Temperature change seems to be the only physical factor that was an
intermittant stress during the 1971 postOperational period. Although
gill nets set in the discharge plume indicated no net movement toward
or away from the discharge canal, fish most likely avoided the thermal

instability without succumbing directly to the frequent thermal change.

Growth Characteristics

Data available on growth characteristics of fish from the study
area have indicated that growth rates for yellow perch (age classes I -

V) and young of the year yellow perch, gizzard shad, and emerald shiners
collected at the lake stations appear not to have been effected by opera-
tion of the power plant. This, however, does not mean that the power
plant will not become a factor effecting fish growth in the future. As
the plant increases production and begins operation of the final generat-
ing units, the increased temperatures should become more stable. Stable
temperatures and the undoubtedly higher oxygen concentrations in the
discharge canal may cause the discharge canal to be increasingly utilized
over extended periods of time by fish in the study area, especially during
the fall and winter seasons. If this situation develops, the increased
temperatures of the canal station may prove to be a controlling factor

in respect to fish growth of some species.

The effect of temperature on the growth of fishes has been exten-
sively studied and a great deal of literature is available on this subject.
In spite of the attention it has received there are some differing Opinions
concerning the mode by which growth is controlled by temperature.
Temperature has been considered as having a physiologically direct influ-

ence on growth (LeCren, 1958). This view has received support by other

T.

“an uni-go;

SE. "

52
investigators who have reported other direct influences of temperature on
fiSh PhYSiOIOBY (Stanley, 1971; Hochachka, 1969; Gordon, 1970; Prosser,
1970; Kunneman, 1970; Edwards, 1971; and Dickson, 1971). Temperature has
also been described as having certain indirect effects on growth (Brown,
1957) and its effect may depend on such variables as food quantity and
quality (Paloheimo and Dickie, 1966; Pandian, 1970; and Kerr, 1971) actively
of the fish (011a, 1971; and Kinne, 1960), or fish densities (Shuett,
1933). The relationship between temperature and growth is not a simple
one. If the discharge canal at the Monroe power plant becomes more
extensively used in the future by fish in the area their growth will de-
pend on these indirect variables as well as the direct effect of tempera-

ture .

Coefficient of Condition

 

In contrast to growth characteristics determined by increment of
growth in length over an extended period of time, the coefficient of
condition depends on the fishes weight in relation to its length and may
describe only a temporary situation. That is, the coefficient of con-
dition may vary according to the most recent environmental conditions
while growth in length is constantly increasing and only the rate of
growth over time is variable. This makes the K factor a valuable indi-
cator of conditions as they exist near the time samples are taken.

The values of K have been used extensively to express the relative
robustness or degree of well-being of fishes (LeCren, 1951)- On this
basis, K has also been used as an indication of relative suitability or
unsuitability of a specific environment (Lagler, 1956). It is with this
purpose in mind that coefficients of condition have been reported for

three species of fish caught in the discharge canal and lake stations.

 

53

It appears that, for carp and young of the year gizzard shad, the
significantly lower R value for fish caught in the discharge canal indi-
cates that in 1971 this station has become less suitable relative to the
lake stations. Again, more than a single variable is involved, and the
resulting K.values may be due to a combination of factors. A change
in the quality or quantity of food organisms could have had an effect.
Increased temperatures accompanied by a stimulated metabolic rate under
conditions of reduced food may have had an additional effect. Reduced
oxygen levels typical of the canal station during the 1971 sampling
period must also be considered. Sublethal decreases in oxygen concen-
tration have been reported to have caused reductions in food intake
(Chittenden and Westman, 1967) and (Davidson, 35 31,, 1959). Chlorine
must also be considered as a possible factor which may alter the condition
of those fish exposed to it.

It is not apparent why the carp and gizzard shad appeared to be of
poorer condition in the discharge canal while the goldfish did not.
Differences in food habits of carp and goldfish (Moen, 1954) would seem
to be a likely factor. However, since the gizzard shad, whose feeding
habits are more similar to the goldfish (Dendy, 1946), showed a decrease
in K in the discharge while the goldfish did not, the hypothesis that
food is the sole factor is not likely. The apparent species specific
response to the discharge canal, in terms of coefficient of condition,
may have resulted from a greater variability of K for goldfish (insufficient
sample size) or an actual species specific reaction to the discharge
environment. Similar variations in response to heated environments by
different species have been reported by Bennett (1972).

The ultimate effect the Monroe power plant will have on the study

area will depend most heavily on the discharge of its heated effluents.

 

54

The changes that took place in the discharge canal during 1971 were
related not only to thermal conditions created by the power plant but

also to changes which occurred resulting from poor quality river water
being pumped into the canal environment. In the future, as pumping rates
increase, a larger proportion of cooling water will be drawn from the
lake, and the water quality in the discharge canal will improve. It is
advised that this study be continued so that thermal effects of the Monroe
power plant can be evaluated in the absence of the additional variables

that were present during the period in which this study was conducted.

SUMMARY OF CONCLUSIONS

Data collected from replicate trawls made in the study area during
1970 and 1971 have not revealed change in total abundance of fish
pOpulations in the study area after plant operation began.

Changes in fish distributions in the study area after plant operation
began are apparent, including an increase in fish use of the Raisin
River and a decrease in fish use of the discharge canal throughout
the entire 1971 sampling period. The changes in the discharge canal
at least attributed, in part, to power plant Operation.

Increased usage of the river station by fish may be attributed to
increased oxygen levels which resulted from lake water being pumped
into the river toward the plant's intake.

Several factors may have contributed to the obvious decline in fish
use in the discharge canal including reduced oxygen, chlorine, and
possible toxicants from the Raisin River. However, an instable
thermal environment is considered the most influential single factor
which resulted in a general avoidance of the discharge canal in 1971.
Growth of mature yellow perch, young of the year yellow perch, giz-
zard shad, and spottail shiners collected in the lake area appears
to be affected little, if at all, by Operation of the power plant.
The discharge canal environment probably has influenced the condition
of some fish species collected at that station in 1971. Lower K
values for carp and gizzard shad are associated with plant operation.
COndition of goldfish did not change significantly during the same

period.
55

LITERATURE CITED

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Ecology. 11: 136-144.

Anonymous. 1970. Lake Erie: common effort can save it. Commercial
Fisheries Review. 32 (8-9): 15-20. A

Applegate, Vernon C., and H. D. VanMeter. 1970. A brief history of
commercial fishing in Lake Erie. U.S. Fish and Wildlife Service.
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Beeton, Alfred M. 1961. Environmental changes in Lake Erie. Trans.
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Bennet, David H. 1972. Length-weight relationships and condition fac-
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Britt, N. W. 1955. Stratification of western Lake Erie in summer of

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56

57

Coutant, Charles C. 1972b. Biological aspects of thermal pollution II.
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Davis, Charles C. 1964. Evidence for the eutrOphication of Lake Erie
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Davison, R. C., W. P. Breese, C. E. warren, and P. Doudoroff. 1959.
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deVlamming, Victor L. 1971. Thermal selection behavior in the estuarine
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Kinne, Otto. 1960. Growth, food intake, and food conversion in a
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Kunneman, H. 1970. The influence of temperature changes on enzymes
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59

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APPENDIX A

60

Table A—1. Actual mean values for the number of species, number of
fish, and biomass (gms) collected per trawl at each of

five trawling stations during 1970 and 1971.

 

Number of Species

 

19701 I

 

 

 

 

II III IV V
7.30 5.20 6.15 6.65 0.95

1971 I II III IV V
8.60 5.85 9.45 3.10 2.00

Number Of Fish

1970 I II III IV V
134.55 50.60 138.6 121.05 8.50

1971 I II III IV V
107.10 80.95 95.90 11.20 11.30

Biomass of Fish (gms)

1970 I II III IV V
7915.60 1390.25 2709.10 7108.05 192.95

1971 I II III IV V
8006.00 2830.45 4513.55 1955.15 286.05

 

1From Parkhurst (1971).

HICHIGQN STQTE UNIV. LIBRQRIES

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