L LARVAL FISH SAMPLING AND POPULATION . . _

DISTRIBUTIONS RELEVANT TO ESTIMATING POWER
_ * PLANT ENTRAINMENT IN WESTERN LAKE ERIE

L” Thesis for the Degree of M. S. . .. »
‘ MICHIGAN STATE UNIVERSITY ' . »

JOHN RANDOLPH MACMILIAN- , . . - -. ~ ¥

0..

1975 ; +    r

 

 

 

 

 

   
 
   

I . , c ' -
I ' . V ' T . . _ - I '- . ‘ - ‘ ~ ':. ,..,/_.'
\‘ ' .' \n ‘ \~ ~ ~ ' . u. - -‘.»¢¢< <-- - ‘R‘\' “.-‘- ""‘““" I: “.t"

    

,.
.‘7. 24‘

 

I I III INN I II I I III II I III I

 

 

 

ABSTRACT
LARVAL FISH SAMPLING AND POPULATION DISTRIBUTIONS
RELEVANT To ESTIMATING POWER PLANT ENTRAINI-iEN’I‘ IN
WESTERN LAKE ERIE
By

John-Randolph‘MacMillan

Larval fish were sampled near the west shore of Lake Erie in 1973,
1974, and 1975. Sampling efficiencies were compared for a 1~m, 571u-mesh,
plankton net, a Kenco pump, and a modified, "high-speed", Hardy, plankton
sampler. The sampling effectiveness was also evaluated for different mesh
apertures and the length of towing time. Studies of larval fish distribu—
tions included day and night assessments of vertical stratification and
the relationship between distance from shore and relative larval abundance
along a 16-km transect. Spatial distributions, abundances, and species
composition were estimated at seven stations in and around the cooling
system of an electric generating station in 1973, 1974, and 1975. The
mortality of larval fish was estimated following condenser passage in the
cooling system.

The most effective sampling technique tested was an oblique tow from
a deep position near bottom to the surface at night using a 571u-mesh,
l-m, plankton net towed for 1—2 minutes. During the daytime, the most
effective technique tested was a combination of oblique tows with the
same net from a deep position to the surface and a l—m, 571u—mesh, plank-

ton net attached to a bottom sled.

John Randolph MacMillan

Vertical, spatial, and temporal variation was great, requiring exten—
sive sampling to identify significant differences in larval fish abundance.
However, the analysis indicated considerable differences in the relative
vulnerabilities of different Species to entrainment. Freshwater drum and
clupeids appeared especially vulnerable. Estimated mortalities, following
condenser passage, were high for all species captured. Therefore, power
plant entrainment potentially has a measurable impact on adult populations
of a few particularly vulnerable species, especially if cooling water re-

quirements continue to expand.

LARVAL FISH SAMPLING AND POPULATION
DISTRIBUTIONS RELEVANT TO ESTIMATING POWER
PLANT ENTRAINMENT IN WESTERN LAKE ERIE

By

JOHN RANDOLPH MACMILLAN

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

1976

ACKNOWLEDGEMENTS

I wish to express my sincere gratitude to Dr. Richard A. Cole for
his intellectual stimulus, advice, and aid in preparing this manuscript.
My appreciation is also extended to Drs. Thomas G. Bahr and Howard E.
Johnson, members of my graduate committee, for their advice and review
of this manuscript.

To the many graduate students who aided in data collection and
provided educational and intellectual piquancy, I am.most appreciative.
Especial thanks are extended to Don D. Nelson for the use of his larval
fish identification key and to Norman Van wagner for his help with the
mortality study.

This study was supported by a grant from the U. S. Environmental
Protection Agency to the Institute of water Research at Michigan State
University. Partial tuition funding was also made possible through a
grant from the U. S. Environmental Protection Agency.

To my parents, for their constant encouragement, I am deeply in-
debted.

Appreciation is also extended to the innocuous perturbations Of
man, whose continual oncogenic behavior and disregard for the environ-

ment precipitated the need for this research.

ii

TABLE OF CONTENTS

LIST OF TABLES . . . . . . . . . . . . . . . .

LIST OF FIGURES O O O O O C O O O O O O O O 0

INTRODUCTION . . . . . . . . . . . . . . . . .

METHODS . . . . . . . . . . . . . . . . . .

Power Plant Description . . . . . . . . .
The Cooling Water Sources . . . . . . . .
Sampling . . . . . . . . . . . . . . . .

RESULTS 0 0‘ O O O C O O O O O O O O O O O O 0

Species Composition . . . . . . . . . . .
Comparison of Surface Sampling Techniques
Mesh Size and Length of Time Towed . . .
Vertical Distributions . . . . . . . . .
Daytime Tows . . . . . . . . . . . .
Transect stations . . . . . . .

Station P17 . . . . . . . . . .

Nighttime Tows . . . . . . . . . . .
Distribution in Relation to Distance from
Distribution in the Cooling System . . .
Seasonal . . . . . . . . . . . . . .
Spatial . . . . . . . . . . . . . .
Variability of Results . . . . . . .
Estimated Mortality . . . . . . . . . . .
Entrainment Estimates . . . . . . . . . .

DISCUSSION . . . . . . . . . . . . . . . . . .

Technique . . . . . . . . . . . . . . . .
Distributions . . . . . . . . . . . . . .
Entrainment Susceptability . . . . . . .

REFERENCES CITED . . . . . . . . . . . . . . .

APPENDIX . . . . . . . . . . . . . . . . . . .

iii

14

14
l4
17
20
20

20
20

28
29

32

32

35
38
4O

45

45

48
51

60
63

Table

2.

3.

LIST OF TABLES

Page

RELATIVE ABUNDANCES OF FISHES IN THE STUDY AREA BASED
ON TRAWL, GILL NET AND TOW NET CAPTURES FROM 1970 TO
1975. O O O O O C O O O O O O O O O O O I O O O O C O O O I 15

MEAN CATCH OF FISH LARUAE PER.100 M3 IN OBLIQUE 1—M
PLANKTON NET Tows FROM MAY THROUGH JULY IN 1974 AND
1975. O O O O O O O O O O O O O O O O O O O O O O O O O O O 16

COMPARISON OF THE MEAN CATCH (5 replicates) PER 100 M3

IN A 571D, l-M, PLANKTON NET; A MODIFIED, HARDY, "HIGH-

SPEED" SAMPLER; AND A KENCO PUMP (all sampling conducted

near the surface) . . . . . . . . . . . . . . . . . . . . . 18

DAYTIME AND NIGHTTIME COMPARISONS OF MEAN CATCH (5

replicates) PER 100 M3 IN OBLIQUE, SURFACE, MIDWATER,

AND DEEP Tows AND TOWING WITH A BOTTOM SLED USING A

571p, 14M PLANKTON NET. . . . . . . . . . . . . . . . . . . 22

PRELIMINARY ESTIMATES OF MORTALITY IN THE COOLING
SYSTEM AT THE MONROE POWER PLANT (ratio of dead to
total catch of alive and dead). . . . . . . . . . . . . . . 39

COEFFIEIENTS OF VARIATION OF ALL LARVAL FISH SPECIES
CAPTURED AT MORTALITY STUDY STATIONS. . . . . . . . . . . . 41

ESTIMATED NUMBER OF LARVAE POTENTIALLY ENTRAINED AT
THE MONROE POWER PLANT IN 1973, 1974, AND 1975. . . . . . . 42

ESTIMATED RELATIVE VULNERABILITY OF IMPORTANT LARVAL

FISH TO ENTRAINMENT AT THE MONROE POWER PLANT FROM AN

AREA 16 KM BY 16 KM IN LAKE ERIE IMMEDIATELY ADJACENT

TO THE POWER PLANT. . . . . . . . . . . . . . . . . . . . . 53

TUKEY'S POST-HOG COMPARISON OF MEAN CATCH USING DIFFER—
ENT SAMPLING TECHNIQUES . . . . . . . . . . . . . . . . . . 63

COMPARISON OF MEAN CATCH BY DIFFERENT SIZES OF MESH IN
I'M PIAANKTON NETS e o e o o o o o o o o o o o o o o o o o o 66

TUKEY'S POST—HOG COMPARISON OF MEAN CATCH FOR LENGTH
OF Tm TOWED l O O O O O O O 0 0 O O O 0 O O O 0 O 0 O O o 68

iv

Page

COMPARISON OF MEAN CATCH BY DIFFERENT LENGTH OF TIME
TOWED IN A 571“, I’M, PLANKTON NET 0 o o o o o o o o o .0 o 69

COMPARISON OF MEAN NUMBER.CAPTURED AT EACH DEPTH STRATUM
T0 OBLIQUE CAPTURE ALONG THE 16 KM TRANSECT. . . . . . . . 7O

TUKEY'S POST-HOG COMPARISON OF MEAN CATCH ALONG THE TRAN-
SECT O O C O O I O O O O O O O O O O O O C I O O I O O O O 72

TUKEY'S POST-HOG COMPARISON OF MEAN CATCH AT STATIONS
SWLED IN 1975. O O O O O O O O O O C O O O O O O O O O 0 75

COEFFICIENTS OF VARIATION INCLUDING MEAN COEFFICIENT
OF VARIATION AT STATIONS SAMPLED IN 1974 AND 1975 FOR
ABUNDANT SPECIES . O C O C O O O O O O O O O O C O O O O O 77

LIST OF FIGURES

Figure Page

1. SURFACE TEMPERATURES IN THE RAISIN RIVER, DISCHARGE
CANAL, AND ALONG THE WEST SHORE OF LAKE ERIE AT THE
SURFACE AND BOTTOM DURING 1973, 1974, and 1975. . . . . . . 6

2. MAP OF THE STUDY AREA SHOWING SAMPLING STATIONS IN
WESTERN LAKE ERIE AND IN THE COOLING SYSTEM . . . . . . . . 8

3. SEASONAL MEAN WIND DIRECTION (tens of degrees azimuth)
AND VELOCITY (km/hr) FROM 1970 TO 1975. . . . . . . . . . . 9

4. COMPARISON OF THE MEAN NUMBER OF LARVAL FISH CAPTURED
(ASE) FOR LENGTH OF TIME TOWED (1, 2, 3, 4, and 5 min)
AND A COMPARISON OF THE MEAN NUMBER OF LARVAL FISH CAP-
TURED (15E) FOR EACH MESH SIZE TESTED (363, 571, 760,
and lOOOu mesh) . . . . . . . . . . .'. . . . . . . . . . . l9

5. COMPARISON OF THE MEAN OF OBLIQUE TOWS TO THE MEAN OF
SURFACE AND DEEP TOWS ALONG THE TRANSECT. . . . . . . . . . 21

6. MEAN NUMBER OF LARVAL FISH CAPTURED (18E) DURING THE
DAY (D) AND NIGHT (N) FOR EACH DEPTH STRATUM (S=SURFACE;
MDfiMIDWATER; D=DEEPWATER; O=OBLIQUE TOW). . . . . . . . . . 30

7. MEAN NUMBER OF LARVAL FISH (18E) CAPTURED ALONG A 16-KM
TRANSECT. O O C O O O C O O O O O O O O O O O C O C O C O O 31

8. SEASONAL VARIATION IN ABUNDANT SPECIES OF LARVAL FISH IN
THE INTAKE REGION AND UPPER DISCHARGE CANAL OF THE COOLING
SYSTEM (Mean i 95% conf 0 Int 0) O O O O 0 O O O O O . O O O O C 33

9. MINIMUM AND MAXIMUM VARIATION (195% CONF. INT.) IN THE CATCH
OF LARVAL FISH NEAR THE MONROE POWER PLANT. . . . . . . . . 36

10. SAMPLING INTENSITY REQUIRED AT VARIOUS PERMISSABLE ERRORS
OF THE We. 0 O O O O O O O O O O O O O O C C O O O C O O 37

vi

INTRODUCTION

Any environmental alterations affecting larval fish survival may
significantly influence the subsequent abundance of reproductively mature
fish. But, the early life history of most wild fish populations is poorly
understood. This is particularly true in the Great Lakes, where demands
on lake resources could influence the survival of young fish. Once-through
cooling at steam-electric generators uses more water than any other process
on the Great Lakes. More importantly, potential for this use could grow at
several times the rate of other resource development on the lakes. This
increasing demand for cooling water could drastically modify the ecology of
early life stages of fish in some environments. The purpose of this paper
is to present data on larval fish distributions and discuss the potential
impact of a large power-plant’cooling system on larval fish survival.

Marcy (1973) concluded that virtually all larval fish died after they
passed through a cooling system on the Connecticut River. Edsall and Yocom
(1972) called attention to the potential for damage of larval fish entrain-
ment into Great Lakes power plant cooling systems. However, because data
on distributions is practically non-existent, potential damage is usually
calculated on the assumption that many important Great Lakes larval fish
are totally planktonic and concentrated close to shore.

A series of mechanistic questions follows as a consequence of the
indiCated need to assess the impact of power plant entrainment on larval

fish populations. Where are larval fish located in relation to the intake?

2

For how long are their movements determined mostly by currents? What currents
are they associated with over that period of vulnerability? How are the
currents determined? How many larvae pass through the cooling system? How
many die following passage? In short, what proportion of the larval fish

from the lake community are entrained and killed by the power plant cooling
system.

These questions were addressed in order to attain preliminary estimates
of the potential impact of intake entrainment at the Monroe Power Plant on
western Lake Erie. Several commonly used sampling techniques were compared
for sampling effectiveness. Vertical distributions were examined under day
and night conditions. Horizontal distributions were sampled in the cooling
system and the lake waters for a distance up to.l6 km from the intake. Larval
fish mortality was estimated in the cooling system. These data were then dis-
cussed in light of statistical complications, the local hydrodynamics as
reported by other investigators, and the potential impact of intake entrain-

ment on fish pOpulations in the western basin of Lake Erie.

METHODS

Power Plant Description

The study was conducted at the Monroe Power Plant which is operated
by the Detroit Edison Company on the western shore of Lake Erie at the
mouth of the Raisin River. All four of the plant's BOO-megawatt units
were completed for operation by mid-1974 with a net total capability of
3,150 megawatts. The cooling water demands for the once-through cooling
system depend on power generation and ambient water temperatures, but maxi-

3 per second. The water is obtained in

mum requirements are about 85 m
varying proportions from the Raisin River and Lake Erie. During spring
runoff the Raisin River may contribute more than 95 percent of the total
cooling water requirements while during the low flow of late summer it
contributes about 5 percent of the total. The biota of each water source
is different so the species and numbers of individuals passing through the
condenser system vary accordingly.

Water enters the cooling system through a lOO-m long intake canal that
is located about 650 m upstream from the river mouth. Prior to condenser
entry, the water passes through a traveling screen with 1-cm diagonal
openings. Water then enters the condenser where water velocities usually
exceed 2 m/sec and the temperature rises to 10-12 C above ambient at full

operation. But, both power generation and pumping rates have varied widely

so temperature elevations have ranged from O to 13 C. The highest temperature

4

elevations were recorded in winter when pumping rates per unit of power
generation were reduced to supply heated effluent for a recirculation
system that is used to control ice accumulation.

The cooling system has a 27,917 m2 double-flow, Type M, single-pass,
divided-surface condenser with 18,154 tubes. Each tube has an effective
length of 17.6 m and 2.54 cm outside diameter. The heated condenser water
is released into a 350-m long concrete conduit where water velocities are
about 1 m/sec at full operation. The water then passes into a rockdwalled
disCharge canal which averages 175 m-wide, 7 m deep in the upper end, 3 m
deep in the lower end, and is 2000 m long. At full pumping, the upper dis-
charge canal velocities average about 6 cm/sec and lower canal velocities
average about 12 cm/sec. However, the velocity is not cross-sectionally uni-
form because high velocity waters approaching l m/sec enter the discharge
canal from the overflow conduit and form an eddy of slower water on the
east side. This adds to the variability of organism residence times in the
discharge canal. Plum Creek drains into the discharge canal but contributes
less than 1 percent of the volume-flow through the canal.

The time of water passage through the cooling system back to Lake Erie
averages 4.5 hrs at full operation. Calculated times are 7 sec through the
condenser, 20 min through the conduit, and 4 hrs through the discharge canal.

The first plant unit began in May, 1971, and the remaining units were
started at approximately one-year intervals thereafter until completion in
May, 1974, Operation began erratically but stabilized as more units
contributed power; 94 percent of all plant shutdowns to date occurred in
1971 and 1972. Total heat loss from the condenser to the lower discharge

canal was about 10 percent of that added. After leaving the discharge canal,

the heated effluent forms a plume which may extend over 4 km from the mouth
of the canal. The largest plume measured by the Detroit Edison Company
(1976) encompassed about 760 he to the 1.7 C isotherm. The plume position
and size depended on the pumping rate, power generation..and the direc- ~
tion and velocity of the wind. Heat dissipation within the plume occurred
in l to 2 days.

Chlorine was added to the cooling water at the intake to control growths
in the condenser; two times per day during summer and once per day during
winter. During the warm months (April-October) chlorine was added at one—
hour intervals for four hours starting at 0700 hrs and then again for four
hrs at 2030 hrs. In winter, chlorine was injected for half-hour periods
at 0700, 0900, 1100, and 1300 hrs. Forty-five kg of chlorine were added at
each application. The highest concentration of chlorine measured in the

discharge canal by the Company was 0.20 mg/liter (The Detroit Edison Com-
pany, 1976).

The Cooling Water Sources

The western basin of Lake Erie is a shallow (7.3 m mean depth), highly
turbid water body which is partially separated from the rest of Lake Erie
by the Bass Islands and Point Pelee. Beeton (1961) attributed the high
turbidity to the wind-generated resuspension of sediments, river discharges,
and plankton densities. submarine photometric measurements made during this
study indicate that only 0.1 percent of the total mean surface light pene-
trated to the 5 m depth during spring and summer. Wind—generated mixing
usually maintains vertical homeothermy in the basin but calm spells may allow
temporary stratification for a few days (Carr £5 31;, 1965). Water tempera—

tures are presented in Figure 1 for selected dates during the study.

    

   

QM
F..t F.T.
GWRT
RRUO
,Zézazzz e“ .A an no.6
e. H E.tct
. CPKK
67 5. mm D..A.A
\\ DULL
\ ..
.. .I§zu
49v“ 2539s§v
Illlllll
7.5
s
s
x
3222‘ x .

5
////.\\ ..
ZI////..\. a _ w 7///////// . Q

I

 

 

 

 

 

 

 

 

zaes .
4‘
s2Z0“ ZZ,/\s .
I: r //z \\\e
azaze . mmVZS
oQZSSS 2Z>¢$_§§
7/4 V\\x I’ll/z / 5/1 x
u x
.1 ..
’ —
El .
.4 ,e a
u . '
. . or
.7. H A E1 5 I.
7
W w .W « mm
. .
P p h F b - IP P b k I F b h n h a I b b h p b p b p s.
.o 2 a 4.nv 6 o..u 4 6 Ac 8 4_nv H mm 8 4.. .u 6 2..u 4.nv 6 as 8 .4

any mmah<mwa2wh

 

CANAL, AND ALONG THE WEST SHORE OF LAKE ERIE AT THE

SURFACE TEMPERATURES IN THE RAISIN RIVER, DISCHARGE
SURFACE AND BOTTOM DURING 1973, 1974, and 1975.

 

Figure 1.

7

The surface area of the basin is 3,276 km2 (Carr.gt.§1L, 1965) and
the shoreline is well deve10ped by islands, peninsulas, spits, and flooded
river mouths. The spatial diversity along the shores provides many kinds
of fish spawning habitat including marshes, rocky reefs, and sand and gravel
bars. The bottom sediment near shore is composed primarily of coarse, medium,
and fine sand Which grades into silt and clay in the deeper waters off shore
(Kelley and Cole, 1976).

The Detroit River annually contributes about 95 percent of the flow.
to the western basin of Lake Erie while the Maumee River, the second largest
tributary, contributes 2.5 percent. The locations of these rivers are shown
in Figure 2. The Raisin River contributes less than 0.3 percent (Ecker and
Cole, 1976). Significant numbers of larval fish may enter the study area
from each of these rivers. The combination of tributaries and prevailing
southwesterly winds generally causes the water in the southwestern corner of
the basin to circulate in a clockwise eddy (Hartley, g£“§1;, 1966). But,
pronounced day to day variations may occur because of changing winds and
tributary discharge. 'Detroit River water predominates off shore while water
from the Maumee and Raisin River dominate the inshore areas. Mean resultant
water velocities in the lake are 1.6 to 2.0 km/day, but during storms fish
larvae from either the Detroit or Maumee River could reach the study area
within a day and larvae from the island region of the basin could reach the
power plant in two days. Wind velocities of 51.5 km/hr or more occur on an
average of 23 days/yr. Mean wind velocity and direction are presented in

Figure 3.

 

 

 

 

 

 

 

 

Figure 2. MAP OF THE STUDY AREA SHOWING SAMPLING STATIONS IN WESTERN LAKE
ERIE AND IN THE COOLING SYSTEM.

.mams oe ohms some Aue\esv seHuosm>
oz< Assesses Assumes so eeouv zoseommHe 92H: z<mz sezomamm .m weewse

¢N 2. Ne. :2. mp3. mh Nh :0» mhwh me. NF 2.0th chm» Nb Koxum.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

106 M
m
and.

r mm mm 8 em 8 I II /
DNMJMWI mmrummmam II I109 m.
em 5 Imam NEWMAN

-03.
1341.. mwszzsm . GZEmm mwkz_>.>

 

 

 

 

10

The lower Raisin River, until recently, was highly polluted with muni-
cipal and industrial wastes, particularly biodegradable organics. Anoxia
was once common during the summer, but improvements in waste treatment have
partially rectified this situation. Environmental conditions remain un-

suitable for spawning by at least some fish species.

Sampling

The efficiencies of different sampling techniques were computed at
station P17 (Figure 2) in 1975.. A submersible,Kenco pump, with a realized
pumping capacity of 6.9 liters/sec, was submersed at the bow of an anchored
boat to a depth of 0.25 m and run for one hour. The pump effluent was
filtered through a 571u-mesh, nylon, plankton net with a l.8—liter,plankton
bucket. Approximately 25 m3 were processed in one hour. Five replicates
were made per sampling date.

A modified,Hardy,plankton sampler (Miller, 1961) was towed initially
at 0.5 m/sec but that was decreased to about 0.2 m/sec because larval fish
extrusion was suspected from the condition of'mutilated larvae found in the
samples. The sampler was mounted off the side of the boat and towed at a
depth of 0.25 m for 15 min. Approximately 18 m3 were sampled at the reduced
speeds. Five replicates were made on each sampling date.

The larval fish rate of capture in l-m nets of different size was com-
pared using 361, 571, 760, and lOOOu mesh sizes. Five replicate samples
were taken with each mesh size. The nets were towed at 0.1 m/sec at the

surface for 3 minutes, and filtered about 90 m3 of water.

11

The variation in catch with length of towing time was estimated with
a 571u~mesh, plankton net. Samples of 1, 2, 3, 4, and 5 minutes were made
at the surface at station P17. An average of 33 m3/min was sampled in the
tows with no apparent variability related to towing time. Five replicate
samples were taken with each length of towing time.

Samples of surface, midwater, deep (1 to 2 m above bottom), and oblique
tows were made at station P17 with a 571u-mesh net. Oblique tows were drawn
at a constant rate from the deep position, at about the S-m depth, to the
surface. Five, l-min replicates (filtering about 33 m3 of water) were made
for each stratum sampled. The station was similarly sampled at night with
surface, midwater, deep and oblique tows. In addition, during the day a
57lu-mesh, plankton net was towed on a bottom sled for 3 min at a speed of
0.2 m/sec. Approximately 31 m3 of water was sampled (estimate based upon
known speed and net area). Five replicates were collected on each date
sampled. A General Oceanics (Model 2030) digital flowmeter was suspended
in the center of all 1-m nets to measure flow through the net.

A transect perpendicular to shore was sampled to define differences
in larval fish densities at various distances from shore (Figure 2). Four
stations along the transect were sampled during the day with a 571u-mesh
net. At each of the transect stations, three replicates were collected
from the surface, three from.deep water, and three with oblique tows from
deep water to the surface. About 100 m3 of water were sampled during a
three-minute tow (l m/sec). Stations P13, P14, P15 and P16, all along the
transect, were 2, 6, 11, and 16 km from shore, respectively.

Tows with 571p-mesh, l-m nets were used during 1973, 1974, and 1975
to estimate larval fish abundance and distributions in the study area. Pre-

liminary sampling was conducted at different depths in 1973 (at stations

12

P1, P2, P3, P4, and P5), but it indicated no consistent significant dif—
ferences among the surface, midwater, and deep samples (Nelson and Cole,

1975). Therefore, in 1974 and 1975, a l-m, 57lu-mesh, nylon, plankton

net was towed at an oblique angle through the water column at a constant

rate from a deep position to the surface for 2.5 minutes. Towing speed was
approximately 1 m/sec. A General Oceanics (Model 2030) digital flowmeter

was fitted at the center of the net opening and a 1.8-1iter,plastic,plankton
bucket was attached to the codend of the net. Because of the unmixed nature
of water entering the intake, two stations were sampled in the Raisin River
channel (Figure 2). An upstream river site (P7) was located about 1 km
upstream from the plant intake and a "downstream" station (P6) was located

at the mouth of the river to sample lake water that was drawn up the old river
channel. An intake station (PO) abundance was calculated from concentrations
at P6 and P7, which were weighed for river and lake volume-flow contributions
to the cooling system. River discharge rates were provided by the U.S.
Geological Service and plant pumping rates were provided by the Detroit
Edison Company. Virtually all river water is drawn into the cooling system
before the balance is made up by lake water (Ecker and Cole, 1976). Samples
also were taken from the upper (P2) and lower (P3) ends of the discharge
canal, and three Lake Erie stations (P10, P11, and P12). The latter were
sampled to assess the concentration and spatial variation of lake larval
abundances.

Mortality was estimated at three stations within the immediate vicinity
of the plant. Larvae were captured with a stationary 1—m, 571u-mesh, cone
shaped,nylon,p1ankton net with a General Oceanics (Model 2030) digital flow-
meter suSpended at its center. A modified (bolting cloth on the inside rather

than the outside of the bucket) 582p-mesh,plankton bucket was attached to the

l3

codend of the net. The stationary net was set in a slow current of 0.15
to 0.25 m/sec to reduce mortality stemming from the technique and to en-
sure comparable sampling conditions. A reference station was sampled in
the intake canal at station P1 to estimate combined natural and net-caused
mortalities. The second station was located near P2 within 100 m of the
outfall from the concrete conduit in the discharge canal. Station P3 was
located 1,5000 m downstream, near the mouth of the discharge canal. Dead
or dying larvae were separated from live animals by color and mobility.
Translucent or mobile individuals were counted as alive while opaque,
immobile ones were assumed to be dead. A field observation device de—
scribed by Marcy (1971) was used to maintain the ambient and elevated
water temperatures around separation dishes while live larvae were counted.

All larvae collected were preserved in S-percent formalin and later
counted and identified to the most specific taxa possible. Rose-bengal
dye was added to ease sorting. All samples were standardized to number
per 100 m3.

All data were tested for normality using the Shapiro-Wilk test (Gill,
in press) and homogeneous variance using Bartlet's test. A log (x + l)
transformation was applied to all data to correct for non-normality and
variance heterogeneity. Then Bartlet's test*was applied to the transformed
data. Heterogeneous variance was usually indicated and a modified Scheffe's
post-data test (Gill, 1971) was applied when applicable. Tukey's multiple
range test was used to identify differences among means when departures
from homogeneity were minor. It was applied to the technique comparisons,
comparisons of stations along the transect, and the comparisons among
stations in 1975. Analysis of variance was applied to comparisons of day

and night abundances.

RESULTS

_§pecies Composition

Out of 15 taxa captured from 1973-1975, the most abundant included
gizzard shad, Dorosoma cepedianum, and alewife, Alosa pseudoharengus (43.6
percent; hereafter referred to as "clupeidS"); Yellow perch, Perca flavescens
(25.3 percent); carp, Cyprinus carpio, goldfish, Carassius auratus, and their
hybrids (10.6 percent); white bass, Morone chrysops (7.3 percent); emerald
and Spottail shiners, Notropis atherinoides and N; hudsonius (3.2 percent);
and freshwater drum, Aplodinotus grunniens (2.0 percent). The combinations
of Species listed above could not be routinely separated to species as larvae.
These species accounted for 92 percent of the total catch. Yolk sac larvae
(prolarvae) represented 19.1 percent of the total catch and post larvae

represented 80.9 percent. Less abundant Species are listed in Tables 1 and 2.

Comparison of Surface SamplinggTeChniques

The 1-m plankton net was the most effective surface sampling technique
tested in the comparison of the Kenco pump, the modified Hardy plankton sampler,
and the 57lu, l-m,plankton net. Significantly (at = 0.05) more larvae were
captured by the l-m net on most of the dates sampled (Appendix A-l). White
bass were captured only in the 1-m plankton net (Table 3).

The Kenco pump was the least effective sampling technique tested.
Significantly (a = 0.05) fewer larvae of all taxa were captured (Appendix

A-l). Fish larvae were captured on June 18 and 19 only (Table 3). On these

14

15

Table l. RELATIVE ABUNDANCES OF FISHES IN THE STUDY AREA BASED ON

TRAWLK GILL NET2 AND TOW NET CAPTURES FROM 1970 TO 1975.
(A a abundant, over 5%; C = common 1 to 5%, S
and NC = not captured).

= scarce, less than 1%;

 

 

 

Adults and
Species Juveniles Larvae

Gizzard shad, Dorosoma cepedianum A A3
Yellow perch, Perca flavescens A A
Emerald shiner, Notropis atherinoides A A“
Spottail shiner, Notropis hudsonius A A“
White bass, Morone Chrysops A C
Goldfish, Carassius auratus A 85
Alewife, Alosa pseudoharengus A C3
Freshwater drum, Aplodinotus grunniens A C
Carp, Cgprinus carpio A C5
Channel catfish, Ictalurus punctatus C C
Common shiner, Notropis cornutus C NC
Brown bullhead, Ictalurus punctatus C NC
Carp-goldfish c 22
Trout perch, Percopsis omiscomaycus C S
Walleye, Stizostedion vitreum C S
White crappie, Pomoxis annularis C S
Rainbow smelt, Osmerus mordax C A
Quillback carpsucker, Carpiodes cyprinus C NC
Silver chub, Hyb0psis storeriana S NC
Log perdh, Percina caprodes S S
Black bullhead, Ictalurus melas S NC
Pumpkinseed, Lepomis gibbosus S S
White sucker, Catostomus commersoni S S
Longnose gar, Lepisosteus osseus S NC
Bluegill, Lepomis macrochirus S S
Yellow bullhead, Ictalurus natalis 8 NC
Smallmouth bass, Micropterus dolomieui S S
Fathead minnow, Pimephales promelas S NC
Stone cat, Noturus flavus 8 NC
Northern pike, Esox lucius S NC
Rock bass, Ambloplites rupestris 8 NC
Chinook salmon, Oncorhynchus tschawytscha S NC

8 NC

Coho salmon, Oncorhynchus kisutch

 

1From Cole (1976)
2From Cole (1976)

3Gizzard shad and alewife are difficult to separate completely
l'Shiners are difficult to separate completely

5Carp and goldfish are difficult to separate completely

16

OquUumuaHnmu m

OqummumuHHamu m “meow—u m no vmaaammm
“mount 0 so vOHaEmmH

 

 

 

 

 

 

 

 

m.ms s.s~ ~.ms m.~e ~.mH o.s~ o.m m.sm m.A~ m.ee e.mH e.H~ m.ms m.em Aesop
o o o o o o o o o o s.0 0 o H.o Lessee muse:
o o o o o o o o o H.o o o o ~.o «masses
0 o o o o o o o m.o o o o o H.o seems mas
o o o o o o o o o H.o o o H.o H.o geese Beets
o H.o o o o o o o H.o o m.o m.o o o Osaaeeo
o o o o o o o m.o m.o o.e m.o H.o H H.o smasueo fleeceso
H.o m.o o e o o o o o H.o m.o s.o o o ewes Reese
o N.o o H.o o H.o N.o e.o «.0 H.H o.H m.H o A.o nmsmeem
m.o H.o H.o e.o ~.o ~.o o o m.o o m.o .H.o e.o A.o Assam
o w.o o ~.H H.o A.H H.o H.H o o.m o H.~ o e.~ aete smeeaemeee
~.o e.s m.o m.o e.o A.o H.o n.o s.~ m.~ e.m e.o ~.o m.o musesem
m.o e.~ m.o m.H e.o o.H e.o m.m m.H m.es H.H H.o e.o s.“ ewes muse:
o m.o o ~.o o ~.o a.o m.m H.e A.os m.m A.NH o e.H cmseeHemueLeo
“.ms o.H m.~ m.H s.m e.s e.o «.0 H.A A.HH e.o s.H A.a o.nu eases gasses
m.m e.o~ o.a m.em m.w m.s A.e e.ms o.HH o.ss n.~ e.m m.s A.ms masseuse
ms es AA es ms es AA SA me I es ms ea As es
NHA AHA cam A «A A A

 

 

.Nmsau oz< seams zH sane
529:: 22 :9: $8. 52 zoeezfia sun upofimo 7: ms 2: mum 33.3 5: mo 5.20 2%.:

. N man—mm.

17

dates, clupeids were the only identifiable taxa captured. About 40 percent
of the larvae captured were damaged. Of the total, 20 percent were damaged
so badly that they could not be identified or included in the statistical
analysis.

The modified, "high-speed", Hardy, plankton sampler was most effec-
tive when larval densities at the surface were relatively high (Table 3).
This occurred only on June 18. On this date significantly (a - 0.05)
more yellow perch and clupeid larvae were captured than with the other

surface techniques (Appendix A-l).

Mesh Size and Length of Time Towed

The 363u-mesh, 1-m net usually caught more fish larvae than l-m nets
with larger mesh sizes (Figure 4). The lOOOp‘mesh nets caught significantly
(a = 0.05) fewer larvae than the 363p or 571u-mesh nets on both dates for
which it was compared. The 760u-mesh net caught significantly (at = 0.05)
fewer larvae on only one of the two dates that it was compared. However, the
relative capture effectiveness of the two smaller mesh sizes appeared to
depend on the species and size (age) of the larvae (Appendix A-2). Prolarval
fish were caught most effectively with the 363u-mesh net. Significantly
(w = 0.05) more smelt prolarvae were caught with the 363u-mesh net compared
to the others on May 21. On May 20, significantly (m = 0.05) more yellow
perch postlarvae were caught with the 57lu-mesh net. On June 21, signifi-

cantly (m = 0.05) more postlarval clupeids were captured using the 363u-mesh

net.

18

 

o m.HN
m.o w.omm
m m m.mo

aesm

Anna:

um: 61H
Hmuoe

000
N00
WOO

mean

ucumm
umc 51H

mumcfizm

mm
oxc;c>
GOO
000
MO‘
O\c;c>
GOO
GOO
GOO

asam

moumm

um: 51H
unEm

GOO
GOO
max
aac$c>
0
OOO
HOO

masm

scum:
um: and
mums mugs:

GOO
GOO
GOO
000
0
GOO
GOO

mean

xnumm

use and
comma Boaamw

hm
a>v§ca
000
0
mm
OUTO
OOO
MOO
\TOO

o.- m.
o.cqm
~.mn

m.H~
n.m<m
H.~o

mesa

zone:
you and

meseaeso

GOO

GOO"

«>c$c>
COO
N00
000

m.
Hmuoe mN\o~\oo m~\ma\oo m~\ma\oo mm\<~\mo m~\m~\mo mm\H~\mo

.AmuwCesm may use: emuwmecou masseeem HHBV Essa oozes < az< “mmamz<m rammmmumonz.wom<z.amHmHaoz <
.emz zoeez<oa 21H Hen < 2H «s ooH mum Ammueusflamu my muses z<mz was ac zomHm<mzoo .m essay

19

.23... .508
see .02 JR .38 SSE 0N3 ems: 8S mom 353 023.20 SE SE:
A0 mmmzpz zfiz m5 m0 2025:1200 < as. SE m Re .e .m .N .3 0860. mama
so 5.025 m0... 333 028.20 mm: .233 m0 swag 24m: use .10 2033:0100

$3 mN_m Imus. m wkdd

 

0N-m m_-m _N-m Cub m_-o m_-m «NA.
0
o .n. n. _ n o _ n" w . n
o h w w R mu 0 u my 0 s m
.5 nim__s n n __ n .m_ _ o n_
mm A
.0.
w
.m. w .
N m
o .n. m
. N W m
m a m
is H
-mm B ...
/
.0» m
w"
C.
.3
.0e

 

.q muswfim

A22): Ikozw... 30... .m wpdo

K)
0]

0
n)

U)
u)

'0
¢

 

rnv

,w 001/ HaawnN NVBW

20

No consistently significant (« = 0.05) or large differences were
apparent between 1, 2, 3, 4, and 5~min tows (Figure 4; Appendix A-3).
The 1, 2, and 3-min tows tended to catch slightly more fish larvae per
unit effort but on June 19, the 5-min tow caught more fish larvae per

unit effort than the others (Appendix A—4).

Vertical Distributions
Daytime Tows

Transect stations: Generally, oblique tows from deep water to surface
were as effective as the mean of stratified tows made at the surface and
deep position along the transect sampled perpendicular to shore. But, some
general species variations existed. Clupeids and smelt tended to be cap-
tured more effectively with stratified tows although they were not statis-
tically different from the oblique tows. Yellow perch and white bass tended
to be caught more efficiently with oblique tows (Figure 5). No consistent
differences in the catch effectiveness appeared between stratified and
oblique tows along the transect, regardless of distance from shore ordif-
ferences in depth to the bottom (Appendix A-S).

Station P17: The daytime net capture efficiency at different depths
was inconsistent in time and by species but in no instances were the means
of oblique and stratified tows different (Table 4). Fish larvae appeared
to be concentrated near the bottom during the day (according to bottom sled
yield) but populations above the bottom did not exhibit any consistent
vertical distributional patterns. Significantly (on = 0.05) more yellow
perch prolarvae were captured using surface and midwater tows (Appendix A-l)

on May 21 and 23 than in deep or oblique tows, but on May 24, no yellow perch

21

50
40
30
20
I0 I

5-22-75 5- 23-75 6- 646-75 7-2-75

mm

 

3% _ I Oblique tows
24 L [I] Mean of the surface and deep tows

 

 

 

5-22-75 5-23-75 6-9-75 646-75 649-75 7-2-75

M

MEAN No./I00m3

Namobfixai
lllllllll

 

 

5-22-75 5-23-75 6 -9-75 6 - 16-75 6 49-75 7- 2 -75

 

 

l8 ... M

I5 ...

I4 .1

'2 ‘

IO .4

8 ..

6 ..

4 _.

2 .4 W
|3|4|5 l6 l3|4|5 16 BMBIG |3|4I5|6 |3|45|6 l3l45|6
5-22-75 5—23-75 6-9-75 646-75 6-l9-75 7- 2-7 5

|2 .

'0 an

 

I I _ I I
5-22-75 5—23-75 6-9-75 646-75 6- I9-75 7-2-75
W

 
 
 

 

    

45l6

Bl4l5l6 13|4| l6 |3I4|5l6 ISM ISIS l3!4|5 I6 |3I
5-22-75 5-23-75 6-9-75 646-75 649-75 7-2-75

Figure 5. COMPARISON OF MEAN OF OBLIQUE TOWS TO
THE MEAN OF SURFACE AND DEEP TOWS ALONG
THE TRANSECT.

22

«.mma

 

0.00 0.00 0.00 0.00 0.00 02002
0.000 0.000 0.0 0.0 0.0 0.0 0.00 000
6002
0.00 0.0 0.0 0.0 0.0 0.0 02002
0.000 0.000 0.0 0.0 0.0 0.0 0 000
00\0~\0
0.000 0.000 0.00 0.00 0.00 0.00 00002
0.00 0.00 0.0 0.0 0 0.0 0.0 000
00\00\0
0.000 0.00 0.00 0.00 0.00 0.00 02002
0.000 0.000 0.00 0.00 0.0 0.00 0.00 000
00\00\0
0.0 0.0 0.0 0 0.0 0 02002
0 I- 0.0 0 0 0 0 000
00\0~\0
0.0 0.0 0.0 0.0 0.0 0 02002
0.0 I- 0.0 0.0 0 0.0 0.0 000
00\0~\0
0.00 0.0 000 0.0 0.0 0.0 02002
0 I- 0.0 0 0 0 0 000
00\0~\0
00000000
«ammz 000m m=d0Hno c002 0009 00003002 womw0=m mmHUOQm
cesaoo Eouuom
00003

 

 

0000 200000 0 2002 020200 024 0300 0000 024 .20023002 .00<0200 .0000000 20
m2 000 000 00000000000 00 20000 2002 00 02000200200 020002002 020 0200000

.002 20022400 210 .2000 < 02000

.0 00000

23

 

 

0.00 0.00 0.00 0.00 0.00 0.0 00002
0.0 0.0 0.0 0.0 0.0 0.0 0.0 000
saw:
0.0 0.0 0.0 0.0 0 0 00002
0.0 0.0 0 0 0 0 0 000
00\0~\0
0.00 0.0 0.0 0.00 0.0 0 00002
0.00 0.00 0 0.0 0.0 0 0 000
00\00\0
0.00 0.0 0.0 0.0 0.0 0.0 00002
0.0 0.0 0.0 0.0 0.0 0 0.0 000
00\00\0
0.00 0.00 0.00 0.00 0.00 0.0 00002
0.0 u- 0.0 0.0 0.0 0.0 0 000
00\0~\0
0.00 0.00 0.00 0.00 0.0 0 00002
0.0 u- 0.0 0.0 0.0 0.0 0.0 000
00\00\0
0.000 0.00 0.00 0.00 0.00 0.00 00002
0.00 -- 0.0 0.0 0.0 0.0 0.0 000
00\00\0
Louwm 30000»
%002 000m 0200000 0:002 0009 0000300: wummusm 000000m
053000 Ecuuom
00003

 

 

0.0.00000 .0 00000

24

 

 

H.MH o.~ o.~ ~.~ o.q N.H uzwfiz
“.0H o.om «.0 m.o w.o m.o H.o awn
:mmz
~.qm o.o m.o ~.m w.OH m.o uswfiz
H.m~ H.m~ o .o o o o has
mm\o~\c
o.OH ~.H o.~ o.H o.m o unwfiz
m.n~ o.NN o ~.o o m.o o ~Amo
m~\¢fi\o
m.~m m.q 0.0 m.m m.~ 0.0 unwfiz
m.mq 5.0m m.~ B.H m.~ o.H ~.o Ame
m~\mfi\o
o o o o o o unwfiz
o.H .. o N.o ~.o o o amp
m~\q~\m
o o o o o o unwfiz
o.m -- m.o 0.0 H.H 0.0 o man
m~\m~\m
o.H o N.o o 0.0 o uswfiz
o u- o o o o o zma
mN\H~\m
mmwm muaxz
kmmz vam macaapo ~:wmz ammo uwumzbwz mummusm meumam
cenfioo Ecuuom
Houmz

 

 

A.c.ucouV .q mHan

25

m.Hw
m.nHH

wmmz
csaaou
umums

m.NNN

o.~

m.m~

o.mmo

vam

Ecuuom

q-cx uxox vqu
h~c> c>r+
h-ww
cnxo CDC)

Om
m
on
H

no 000
HQ 00
cm (\m
Ha) 0CD

umumzcaz

“cwfiz
xma
cmmz
unwfiz
5mm
mm\o~\o
usmfiz
Ana
m~\ma\o
unwfiz
hma
mN\mH\o
unwfiz
Ame
m~\q~\m
unmfiz
>ma
m~\m~\m
unmfiz
xma
mm\am\m

“HQEm

 

mmfiumam

 

 

A.v.ucoov

.c manme

26

000
mm

0.0

”N
NU}

©.N

N.m

H.mm m.mm

wmmz vam
canaoo Ecuuom
umumz

OO

m=UfiHno

amwz

NM
MN

00

CO

ammo

an\
OH

\00

OO

umuvaHz

monuusm

uswfiz
Ame
:mmz

uswfiz
Ame
mN\oN\o
uzwfiz
zmo
mn\ma\o
unwfiz
mma
nm\wa\o
unwfiz
zma
m~\¢~\m
ucwfiz
>ma
mN\mm\m
unmfiz
zma
m~\am\m

mumcfinm

 

mmfiomam

 

 

A.w.ucoov

.q magma

27

.xummc E m w you mumuum Ham mo cmme cmuzwwmz~

.msou nmmv vcm umumavae .mummuzm mo smut"

 

m.mm m.wH o.o~ o.ma “.0N N.MH uswfiz
m.“ m.“ o o o o o xmo
cmmz
~.nmq @.om q.nm q.Ho N.OMH «.05 unwfiz
o.o 0.0 o o o o o zmo
m~\om\o
N.NQH ¢.¢N ¢.mm ~.mm o.qm H.m unwfiz
o.m o.m o o o o o xma
m5\ofi\o
m.oN H.m H.¢ m.~ m.m o.q unwfiz
m.NH m.NH o o o o o ~Ama
n~\mfl\o
o o o o o o unwfiz
o u- o o o o o >mo
m~\q~\m
o o o o o o ucwfiz
o -- o o o o o has
mh\m~\m
o o o o o o unwfiz
o u- o o o o 0 man
m~\H~\m
mumo
kmmz vmfim msvfiano cmwz ammo umumzcaz mummuam mmwuwam
cesfioo Seuuom
umumz

 

 

A.u.u:00v .q maan

28

prolarvae were captured at the surface even though they were captured in

all other tows. Similarly, the catches of clupeid and Shiner larvae at

the three discrete depths usually were not significantly (a = 0.05) dif-
ferent from one another. Yet on exceptional dates, significantly (0: = 0.05)
more clupeids were captured at the surface (June 19) and significantly fewer
shiners were captured in midwater (June 18). Much of the inconsistent-
variation that occurs in vertical distribution above the bottom appears

to be caused by day to day vertical Changes in the clumped distribution

of larvae.

When the 57lu,l-m,plankton net was towed on a bottom sled, it yielded
significantly (a = 0.05) more fish larvae of all important Species than all
netting at other strata above the bottom (Appendix A-l). Capture rates
with the bottom sled were greatest on June 18 when clupeids and smelt
dominated the catch. On this date, over 100 times more larvae were cap-
tured with the bottom sled than with all the other tows tested. Daytime
catches of all taxa were greatest with the bottom sled. It appears that
most larvae concentrate near the bottom during the day, but any larvae
caught above that bottom concentration do not exhibit any consistent strati-

fication.

Nighttime tows

Nighttime capture rates in the water column above the bottom averaged
at least two to three times the daytime capture rates (excluding the bottom
sled) for all of the major taxa. The ratios ranged from 1.5:1 to 49:1.
The nighttime capture rates of yellow perch, white bass, and freshwater drum

were significantly (a = 0.05) greater than daytime capture rates on all dates

29

sampled. Nighttime capture rates of clupeids, smelt, and shiners were
significantly (a = 0.05) greater than daytime capture rates on most of the
dates sampled. The mean ratios over all sampling dates of daytime to
nighttime captures were: freshwater drum, 0.07; yellow perch, 0.18; smelt,
0.20; clupeids, 0.24; white bass, 0.29; and shiners, 0.41. Although the
nighttime ratios of most larval taxa captured at each depth were not always
consistent over the whole sampling period, deep catches tended to be highest
and the surface catch lowest (Table 4). Relatively more yellow perch and
smelt were caught near the bottom at night compared to other species, while
relatively more shiners and clupeids were caught closer to the surface

(Figure 6).

Distribution in Relation to Distance from Shore

Daytime larval distribution along the l6-km transect revealed species
Specific gradients. Clupeids generally were relatively abundant at near-
shore stations (Figure 7) where on June 9 and July 2, these stations yielded
significantly (a = 0.05) more larvae (Appendix A-6). Gradients were unrecog-
nizable when larval catch was relatively low. Yellow perch prolarvae were
significantly (m = 0.05) more abundant at offshore stations as were smelt,
and, to a lesser extent, white bass and shiners (Appendix A-6). On May 22
and 23, yellow perch larvae were caught along a distinct gradient from
shore and station P16 had the greatest abundance. White bass were captured
mostly at station P16. Freshwater drum were captured primarily on June 16.

On this date most (at = 0.05) were captured near shore at station P13.

MEAN NUMBER/loom3

CLUPIIOS

 

VILLW KICn
03 ‘ i

50‘ .[l-uuz.‘
4

 

 

Figure 6.

 

30

,III I .

 

 

13 ‘ ”an:

 

 

220 IRISH-I'll! WI

 

  
     

0-0.0-00 0’000-00 0.000-000 00 00 0
Dru" Ds-nl

'THME

MEAN NUMBER OF LARVAL FISH CAPTURED (:33) DURING THE DAY (D) AND
NIGHT (N) FOR EACH DEPTH STRATUM (SeSURFACE; MD=MIDWATER; DéDEEP .
WATER; O-OBLIQUE TOW).

31

N...

 

N-h

 

~ . s
at a... v... n...

bbbbbbbh—
1

.Smmzéa 5-3 < 98.2 ugh—.20 253 mm: 33% mo an; zfiz

670 070 0-0

9-0 070 0.. o
0.; 9; 0.; n.; 0.; n.; 0.; 9; 0.; n.;!; 2; 0.; 0.; 0‘2; 0.; n... 0.; n... 0.; 0.; 0.; n...

o. . 0 o. - 0 a - w
0.; 0.; 0.; n.; . 0.; n.;'.; 9; 0.; 0.; 0.; n

DDPFFIDDFIh—.-‘——DD_—DD>

20....dhm 024 930

nN-n NN-n

Phbhhbb_bhhblbhh
‘

mcmz.zw
nN-n NN-n

mm<n uh...)

nN-n NN-n

—; _ 0.;o.; 0.; 0.; 0.; 0.; 0.; 9;

bbhhh>b‘_...er'T

m

zuzu; togau>

0.; 0.; 0.; n... 0.; 9; 0.; E; 0.; 0.; 0.; Q; 0.; 0.; 0.; 0.; 0.; 0.; 0.; 0.; 0.; 0.; 0.; n.;

.0
.0

.O.
.N.
.0.
.0.
.0.
.ON

 

 

.2
.2
4.
a.
5.
6N
&~

 

7'
v0
v0
.0.
-N.
1'—
r0.
.0.

..ON
.NN

 

 

N-h 2-0 0. - 0
0r.» mt. 0b.;b m.“ — 0..;. mi 0.; n... 0.; 0.; 0.; 2; 0.;
N-h 9-0 0. - 0
0.; 9; 0.; n.; 0.; 0.; 0.; 0.; 0.; n.;0.; n.;

 

0-0

DID-0’0.

0.; 0.; 0.; n.; —

.5 wim

nu... --n
a: a... «in... 2.382.»:

 

‘

 

Phil-.D-Fhr 01”
a- l m

mo.u;=..u

.n wuswfim

To.
.0.

..ON

#00

 

.00

to.

T00

.00

.00

 

0..

cW DUI I HBBWHN NVBW

32
Distributions in the Cooling_System

Seasonal

Figure 8 shows the seasonal variation in the capture of larvae of
several important taxa captured in the upper discharge canal and the intake
region. The comparative annual data from 1973 and 1974 were obtained partly
from Nelson and Cole (1975). Seasonal patterns repeatedly emerged in each
year even though there was very great temporal variation in the abundance
of larvae captured during the periods of time that they were found there.
Peak abundances of yellow perch and smelt were the first to appear in May.
followed by carp-goldfish and white bass, and finally, clupeids, shiners,
and freshwater drum. The differences in the length of time that different
species were present appeared more obvious than the time of peak abundance.
The earliest spawners tended to persist as catchable larvae for the shortest
time period, while the species that are most abundant later in the year
were more likely to maintain catchable larvae for a longer period of time.
. Larvae of carp, white bass, and clupeids consistently appeared in the dis—
charge canal before they appeared in the intake region, indicating that
some recruitment took place in the discahrge canal. The larvae of one
rarer species, channel catfish, were almost exclusively captured in the
discharge canal and the intake region.
Spatial

The probability that recruitment of some species could be occurring
in the upper discharge canal is indicated by the annual comparison of total
larval numbers shown in Table 2. Carp-goldfish, white bass and clupeids

were captured consistently in greater numbers in the upper discharge canal

33

mum<m0wHQ mmmmb 92¢ ZOHUMM MM<HZH

 

 

 

 

oaa 4:5 2:3 >¢a
C 0. Q C 04.0 0000. 0000.
w m T
.00.
r
33 ”:1; 03.
35:85 5......
03¢ 4:3 2:3 >41
0 0‘ 0‘ CGCD .000. 00.0
mulealJu . o
n a
T
an
T
33 utzs .
wx<hz. rOn

 

...uaH .maou Nam“ ammzv zmemwm quaooo may no q<z<o
may zH mmHm q<>m<a mo mmHummm az<nzam< zH 20H9<Hm<> q<zom<mm

 

 

 

 

 

 

034 435 23a >(3
a a. a. coco cocoa secsb
Ill—In H o
100
lg.
luau; 3044w>
wom<rom5 cw;;:
03¢ .33 22% >42
o do a. «can «can. noon.
0 u n n o
f
100
T
1
55.1333» .
wx<hz. r00.

 

 

 

 

 

.w ounmfim
034 4...... 23... >42
a do a. dado «can. occur
I no!“ u a o
n g T
_ .
— j .00
r
c .
1
e09
mo.w;DJU
u0¢(zom_o Zuni...
0:4 4:3 2:5 ><1
¢ a. no «can coooc secsb
— ,-

n~m_¢
050.4
nhm.0

mo.u;:40
wx<hz.

 

cw oou / HEBWflN Nvaw

34

23.. >4!
coco cocoa ocao

 

and ......-
0 0. O C

034 43..
0‘ 0 0

IMIF<U Juzz<xu

uoz<zuma «man:

235 ><I
coco coco. cacao.

...qm.al.nu.....o
r

1

rec

 

 

Imihdu ..uZZdIU
wxdhz.

.C._
t”.—
'0.—

 

rO.~

>42

 

03¢ ...... 235
Q 40 6‘ 0400 .000. .0000
0:4 43.. 23..
0 0‘ 0‘ 00.0 0000. .0000

 

flmn um

rm...o..oo - ;¢<u
womdzuma tuna:

>41

Im.uo..ou - n¢<u
9.4:...

 

 

eon

.As.ucoos w Guzman

 

oo.

 

 

0:4 3.. 22. >52
0 o. C. 4.0 .040. 00.0
I n .0 and: . u r O
a .
T
:3
.
$2.1m e
35:85 5%.: on
SE ..2. 23. :3
C o. a. .000 .DCD. 00.0 o
n m mum u m n a
l
1
. n~
525m fl
uxdhz. on

 

sW OOI/ BEBWON NVBW

35

than in the intake region. This was not apparent with the perch, shiners

or drum larvae. It also appears that larvae of most Species are consis-
tantly less abundant in the lower end of the discharge canal than in the

upper end of the discharge canal. Most of the abundant taxa were relatively
common in the lake. The exception, carp-goldfish larvae, were much more
abundant in the river, like several of the rarer taxa including the ictalurids

and centrarchids (Table 2).

Variability of Results

Even though consistent annual patterns emerge in the temporal and
spatial patterns of larvae around the cooling system, great Spatial varia-
tion only allows the statistical discrimination (a = 0.05) of major dif-
ferences at the intensity sampled. This variability appeared to be caused
by "patchy" distributions and strong fluctuations in recruitment during the
spawning season.

The influence of patchy variation is exhibited in Figure 9 which shows,
for important species, the dates that Spatial variation was minimum and
maximum in the cooling system. Abundances tended to fluctuate at any one
particular Station in response to patches of larval fish moving through the
lake ecosystem and the cooling system. Differences in concentrations at
the three lake stations, which were all within 4 km of each other, could
exceed an order of magnitude on one date and be virtually indistinguishable
on another date.

The degree of variation determines the sampling intensity required to
differentiate concentrations in different areas at various permissable errors

of the mean. Figure 10 illustrates how the variation is influenced by patchy

36

.Hgm ”530... momzoz mm... 32
:mHm 1:353 no $0.55 ma .3 THZH ..mzoo Nmmflv ZOHH<HM<> 232...”: 02¢ ZDZHZHZ .m ounwflm

                     

 

 

 

 

 

 

 

 

 

wzozkhm
2. 3 3 3 3 a... .... o... 3 3 3 3 3 u: :3 o... 3 3 0.. 3 3 a... :3 o... 3 3 3 3 3 «.3 .3 o...
3.0+);
m n - I I U H.
_ l. m, .on I:
y W .00 w
- .. .8 H .8
. m .2 m m x
. 3. a. ,2
v on W 100. m. v 0' W W v 0'
j .8. m . an m m f 3
. To; - m w n
. o. m m w a o.
.. .00“ m I w
.. 0.. a w . 0..
. 33 m
.8. .oo» . o. .. m . o.
. 63 m. . o. H m . o.
. .ouv - .00. m. m .09.
. .o: w m m
N no. _ m, m 3..
a 63 .... m 93.3?“ -
395...: 33...: ran. acts-3 333.5: 325...; .53... r 3. 8:33) 32.32.. H .02
st..\0 'h\..\0 nhxuzo 0k\.:0
5.389 2: =3 33 up...) 22.3 333» 8.339
3 3 3 3 3 u; .... o... 3 3 3 3 3 a... :3 o: 3 3 0.. 3 3 a... .... o... 3 3 9. 3 3 a... .... o:
m I . w o. - a a
j
v O- v C“ u o.
a
v n. y 1 3 v 0.
..ON a 08 v 0' v ON
. on . . on . on
.8 To. . .0»
..n . 2 .3
v0. won a o. '0'
in. v v o. '0'
.oo . .oo. .oo
.3 .o: .3
v
295.3; .55....- r
2. 2:. o. 395...; 3”...“ 2. 3.5.5» 32:3... 3. 295.3» 1.3.2:. .0.
22.33 22 a u .2 a; .233
33 33 u»!- 333 3343 . 3.339

,w con / uaewnu nvaw

37

 

 

5 0‘ 05
SHINERS

YELLOW PERCH
.2

 

 

 

I0.000 '

CLUPEIDS

90L
20*
O
50,
20>
IO

0 o o o O
o 0 0 o o
o. o. 5 2 I
5 I.

I0.000 '
5.000 »
|.OOO .

500 >
200
l 00 “

 

 

.3 .4 .5

WHITE BASS

 

 

 

 

o o ..u 0 mu 0 o mu 0 .0 O ...u W m 0

o o o o o 0 5 2 I o o O 5 2 m
0 0. O 5 2 I O 0 w 0 nlv

O. 5 l. O- O. W. 2

IO
5

ZO_._.<.rm\m._.<u_-Emm

ERROR

PERMISSABLE
SAMPLING INTENSITY REQUIRED AT VARIOUS PERMISSABLE

ERRORS OF THE MEAN.

Figure 10.

38

distributions and temporal change. The variation was greatest when the mean
catch was low and least when the mean catch was high. The minimal variation
that is plotted for variation among replicates defines an ideal situation
requiring the least sampling intensity. The additional Spatial variation
introduced by sampling at two other nearby (2 to 4 km apart) stations on the
same date requires 6 to 10 times more intensive sampling to maintain the
same permissable error. When sampling at all three stations, the intensity
of sampling must be increased at least 100 times (depending on species and
date) to reduce the permissable error from 50 percent to 10 percent of the
mean with a 95 percent confidence interval.

When seasonal variation is also introduced, the sampling intensity
required may be increased from 10 to 1000 percent depending on the species
and the year sampled.

There was considerable difference in the seasonal variability defined
for the two years; 1974 was less variable than 1975 for all important species.
This demonstrates that the long-term sampling intensity required over a
sequence of annual studies to meet a Specified error cannot be precisely
determined with one year of data. To a certain extent, the variability
encountered is proportional to the mean concentration of larvae captured.
The rare species encountered in the study area would require an extra-

ordinary sampling intensity to precisely estimate their population sizes.

Estimated Mortality_
The studies of larval fish mortality in the cooling system indicate
that substantial mortality occurs following condenser passage (Table 5).

The mortality at the intake station caused by technique and natural events

 

 

 

Table 5. PRELIMINARY ESTIMATES OF MORTALITY IN THE COOLING SYSTEM AT
THE MONROE POWER PLANT.
(ratio of dead to total catch of alive and dead)
Total Total Total
Number Upper Number Lower Number
Species Intake Caught Discharge Caught Discharge Caught
low
Carp 0.09 20 0.27 8 abundance 1
low
Yellow perch 0.20 40 0.72 5 abundance 2
Clupeid 0.15 66 0.79 11 0.80 2
White bass 0.04 25 0.25 3 0.80 5
All larvae 0.16 176 0.73 29 0.59 10

 

40

appeared to be Species Specific. A relatively large prOportion of white
bass and carp larvae were dead in the intake canal while a relatively
large proportion of yellow perch were alive. Following condenser passage,
the proportion of dead larvae of all taxa captured increased from 20 to

80 percent compared to the reference station in the intake canal. Con-
sidering the probability that some larvae hatch in the discharge canal,
the estimates of larval mortality caused by condenser passage may be con-
servative. For example, yellow perch were the least likely to hatch in
the discharge canal and their death rate was about the highest. The total
catch of dead larvae in the lower discharge canal was similar to that in
the upper discharge canal, but there were.fewer fish captured in total.
Coefficients of variation (Table 6) were consistently high making precise
estimation of mortality difficult. These estimates, in combination with the
consistently lower numbers Observed in the lower discharge canal compared
to the upper discharge canal, indicate that very large mortalities take

place among larvae that pass through the condenser.

Entrainment Estimates .

Estimates of the total annual entrainment of all species are presented
in Table 7 for the three years of study, based on captures in the upper
discharge canal. These values were calculated from the estimated length of
time larvae were present and.the mean catch on the dates sampled. In some
cases, the 1973 estimates are low because sampling was discontinued before
the season ended for several of the taxa. However, Species like yellow

perch and white bass should be comparable and, of the three years, 1973

41

Table 6. COEFFICIENTS OF VARIATION OF ALL LARVAL FISH SPECIES
CAPTURED AT MORTALITY STUDY STATIONS.

 

 

 

Upper Lower
Date Intake Discharge Discharge
4/28 172.0% 61.1% 95.0%
5/18 338.4% 108.0% 245.0%
6/3 66.6% 127.1% 97.3%

6/26 82.6% 75.3% 103.0%

 

42

 

o ~.oz H.oz mzmafimz

o m.oz c.0- oaaamuu

Ne w N5 .v.~.o 5.0.. NS- D35

0.02 n.02 o mmmm

«A w. .1 w 0 ES w ed w H; To- $095

~.2 HTS-VJ: 9mm wfifl wag Saw-SA was 222.0,

H.o z m.wm w.m.o~ “.m.n o anew poemsnmmum

m.q w.m.H w. o m.qo .W o.wm .W w.o H. z nmfiwumo Hoccmno

mg; wmamwfifl mgflwaaw No.3 in A ~.N.v.o 58a 30:3

«.2 we; .v-md odomwwdm WHEN Héwegwfia $2 322

0.2“ WTmemi mamawegflwsém Sewma we 38

macaw. WSMQSN OAS-v. men: wagon A: .v.m.o.v.o $3930
maaa «ASH maoH mmfiumam

 

 

A~.uca .maoo Nmm H ummm\m:oqaafiev

.mnma 92¢ «so.
..mnma 2H Hz<4m mmzom momzoz mmH H< szH<mHzm MAA<HHszom m<>m<q ho mmmsz

nme<szmm .n 0.3mm.

43

.ucmecfimuucm mo mumefiumm Hmsccm one m>mw mmmcu
mo Esm one new wmucmmmuamu uH umnu m>mv mo amass: one mp wmfiaefiuHsa was mumefiumo mafimv nomm
.mumc mcaHQEmm ucmnvwmnnm m 00 mxmc mo Henson use man: made oumo mafiansmm umnu ucmmouamu ou
umsnmmm mes mume«umm zafimu one .ucmecwmuuam mo mumefiumm >Hfimv m wcfieumumw 00 Damn umnu co
amumxm wcHHooo ecu stOHSu 30am mesao> onu up mwumnumfip poems ecu um AmHm>umucfi mocmwfimcoo
nmumHoommm nemv Dump wcfiHaEmm\ma\om>pmH mo Henson ecu wcfimfiaauase >n wmumaaonUN

.ocahluae cw nmuoaaeoo mmz wcHHaEmm mnmaa

 

 

~.~m~ .v. 33w «.9... and; w. 0.8m .v. .23 08 wmiw a; $53 .38.
o.Hz H.oz H.o- couma won
N.oz «.02 H.oz canon 03009
O . ~.o- N.o- mumxusm
mama «ASH mama mmaomgm

 

 

9.353 .5 USE.

44
produced the lowest numbers while 1974 produced the highest. The differences
in the estimate between years usually was less than an order of magnitude
among species fairly represented by full seasonal sampling.

Although variances are great, as indicated by mean confidence intervals,
the annual differences in density among the more abundant Species are sur-
prisingly consistent. This would indicate that some universal environmental
feature was Strongly influencing the capture rate of all Species.

The relative abundance of larvae caught in this system is not necessarily
indicative of the actual entrainment ratio because taxa like carp-goldfish,
white bass, clupeids and channel catfish probably hatch in the discharge
canal. Therefore, estimated entrainment abundances are probably high for

those species.

DISCUSSION

Technique

The results of the technique comparisons made in western Lake Erie
should be widely applicable to any comparable, turbid shallow lake or
reservoir that is inhabited by the same or similar fish populations. One
of the primary tenets of practical sampling is to representatively, but
efficiently, assess the relevant characteristics of larval fish distribu-
tions. Practicality urges that the information gained from sampling be
measured against the effort expended. Therefore, time and expense must
be included among the determinants of the most suitable techniques.

The most effective daytime sampling approach used to assess larval
fish density is a combination of oblique, l-m net tows and l—m net tows
made at the bottom with a sled. During the day, oblique tows alone do
not include the greatest concentration of larval fish at the bottom be-
cause the obliquely towed net cannot be set close enough to the bottom.
Above the bottom, there appeared to be no consistent, depth related pattern
to the vertical distribution so towing at discrete depths yields less
information per unit effort than oblique tows of the same length.

Neither the Kenco pump or the modified "high-speed" Hardy plankton
sampler were any better than sampling with a 1~m plankton net. Their
capture rate at the surface was the same or less than the rate with a
l—m, plankton net and both techniques were more time consuming. Icanberry
and Richardson (1972), in using a pump for zooplankton sampling, found

no significant difference in their catch compared to a 150u~mesh plankton

45

46
net. In this study, pumping took about 20 times as long as tow netting

to process the same amount of water. Both the pump and the "high-speed"
sampler are more difficult to use than the tow net for depth-integrated
sampling. The "high-speed" sampler is particularly impractical in rela-
tively shallow, shore zone waters.

The nighttime sampling effort yielded more larvae then the day-
time effort, just as others (Miller £5 21,, 1963; Clutter and Anraku,
1968; Noble, 1970; Faber, 1967; and Marcy, 1973) have described for a
variety of environments. From 2 to 50 times as many larvae were captured
in oblique tows at night compared to day. The estimated catch per square
meter of surface at night, without the bottom sled, averaged close to
the daytime estimate with the bottom sled. This similarity suggests
that larvae do not appear to be consistently concentrated near the bottom
at night, so the sled, which is particularly cumbersome to use at night,
may be unnecessary if all sampling were conducted at night. The varia-
bility among sample replicates was less at night than during the day.
Therefore, night sampling can yield more information per unit effort
about horizontal distributions.

Oblique night sampling is mbre effective than stratified night same
pling. Although species like perch and smelt tend to concentrate in the
lower strata, the differences in nighttime vertical distributions above
the bottom are not nearly as great as differences in current velocities.
Depth related variations in water velocity are much more likely to in-
fluence the determination of the nighttime changes in larval fish distri—
butions than the relatively minor vertical variations in larval densities.
Studies of wind-generated movements in various environments indicate

that velocities can easily decrease an order of magnitude within a few

47
meters of the surface (Hutchinson, 1957; Hartley g£_§l,, 1966) and this

is substantiated by other studies (Cole, 1976) in western Lake Erie.
Hypothetically, both the mesh size and the towing time can influence
the catch rate of plankton nets. Heron (1968), Wichstead (1963) and
Tranter (1963) all found that different mesh sizes affect the yield of
zooplankton because of the animals size distribution, the net filtration
efficiency and the rate of net clogging with suspended matter. In this
study, all nets larger than 363p captured far fewer prolarvae than the
363D net. However, S71u and 760u~mesh appeared to be suitable for most
postlarvae while 1000p mesh was unsuitable. In environments like western
Lake Erie, where there are often strong spatial and temporal variations
in the concentrations of suspended solids, the optimum net size will vary
accordingly. Either the mesh size will have to be adjusted to suit the
conditions, or a "compromise" mesh size should be selected. In this part
of Lake Erie, the compromise mesh size appeared to be near 400p to Soon.
The length of a tow that can be made without affecting the capture
rate also is likely to depend on the mesh size because the amount of clog-
ging from suspended matter depends on the time towed (Vanucci, 1968). The
reSults of towing 571u~mesh nets from 1 to 5 min indicated no differences
in capture rates for any towing times under conditions that were sampled
in Lake Erie. The patchiness of larval fish distributions may influence
the choices of a tow length if the fileering efficiency isnnot greatly
affected by the towing time. Noble (1970) noted that short tow times
may enable an increased number of samples and decrease the variability
at a station which may be introduced by longer tows. This is likely to
be true when the larvae are grouped in relatively large patches or are

not at all clumped in their distributions. On the other hand, Wiebe (1971)

48

thonght he gained precision by lengthening tows whenever larvae formed
small "pat :es" because there is greater probability of sampling a similar
("right") number of patches.

In our studies the length of tow between 1 and 5 min did not affect
the catch rate or variability of catch even though the variability among
replicates was up to a 300 percent coefficient of variation. The Lake
Erie distributions appear to be less variable than those deccribed by
Wiebe (1971). Considering the information return per unit effort in
western Lake Erie, shorter tows of 1 to 2 min seem to yield more than
longer tows of 4 to 5 min because more sampling replication can be gained
within the total time limits.

The most efficient approach to defining horizontal distributional
variations near shore seems to be sampling at night with 1 to 2 min oblique
tows. Even though night navigation can be difficult and night sampling
is more time-consuming than day sampling, greater information appears to
be gained from night sampling. The size of water body, distance from
shore and availability of lighted landmarks and buoys will help to deter-

mine the relative effectiveness of night sampling.

Distributions

 

The kinds of distributions exhibited by different fish species not
only helps to clarify their relative vulnerability to intake entrainment
but also aids in choosing a suitable sampling design. The combination of
physical heterogeneity and behavioral attributes typically causes non-
random, "patchy" (Cushing, 1961), "clumped" (Wiebe, 1970), "aggregated"
(Barnes and Marshall, 1951), or "over-dispersed" (Cassie, 1959) distri-
butions which are usually described or approximated by the negative bi-

nomial (Taylor, 1953) or Poisson-log—normal distribution. These

49

distributional variants have been hypothesized to originate from water
discontinuities and heterogeneity arising from weather phenomena and tri-
butary hydrodynamics or interspecific and intraspecific behavioral patterns
(Cassie, 1962; Saville, 1965; Barnes and Marshall, 1951; and Wiebe, 1971).
In western Lake Erie, both wind and tributaries could influence the patch-
iness of larval fish distributions. The relatively great sample variation
among replicates at a station may indicate that the larvae are concen—
trated in "swarms" of relatively small volume (less than a few.meters in
diameter) like those described by Barnes and Marshall (1951). However,
the average concentration within groups of swarms at different stations
could vary by an order of magnitude within a few kilometers, just as
Silliman (1946) found in the distributions of pilchard, Sardinops caerula,
eggs. The distributions of most larval species frequently seemed to occur
as patches over 100 m long (length of a 3 min tow). It was not possible
to tell whether gradual density gradations or large discontinuous patches
existed among stations. Therefore, the upper size limits of the patches
are unknown.

The configuration of these patchy distributions may be at least
partly dependent on the fluctuations of tributary mixing with lake water,
wind-generated vascillations, and larval locimotion. Both Bishai (1960)
and Saville (1965) state that current is the most important determinant
of larval fish distribution in oceanic environments. In western Lake Erie,
currents are controlled mostly by the wind and the Detroit River. Pre-
vailing southerly winds tend to maintain a clockwise gyre off the mouth of
the Maumee River in the southwestern corner of the lake (Ecker and Cole,
1976), therefore, the prevailing currents move a combination of Maumee

and Detroit River water northward along the shore past the power plant

50

intake. Several kilometers off shore the water is derived almost entirely
from the Detroit River (Hartley gt al., 1966). The results from the sampl—
ing transect, which extended deeply into Detroit River waters, indicate
that densest concentrations of yellow perch, smelt, and white bass larvae
are entering the western basin from the Detroit River. Species of fish
like the shiners did not demonstrate any clear density gradient associated
with the distance from shore. But, species like the clupeids and fresh-
water drum are most abundant near shore and they may have hatched near the
power plant or were carried northward from the Maumee Bay region. Species
groups like the catfishes, sunfishes, and carp-goldfish were common in the
river but not in the lake. These species require marshy or protected
shoreline environments for successful spawning and most river larvae probab-
ly came from.marsh overflow and protected river edges.

Similarly, the larvae of fish species in Lake Erie are not all dis—
tributed alike in the water column, although all of the abundant larvae
appear able to move vertically in apparent response to changing light in—
tensity. Nighttime concentrations in the water column were much greater
than daytime concentrations above the bottom, but they were similar
(although variable) when daytime bottom tows were included in the compar-
ison. An alternative explanation for the apparent difference between
day and night concentrations is differential net avoidance. But, that
seems less plausible than vertical movement because the slower prolarvae
are more likely to be vulnerable to capture during the day than the faster
postlarvae. There was little evidence of such differences. Also, the
"high-speed", modified, Hardy, plankton sampler would have been much more
effective than tow nets if net avoidance had been important. This diurnal

vertical migration between the slowly moving bottom waters and the

51

relatively rapidly moving surface waters strongly affects the probability
that larvae will be carried near an intake.

Some subtle differences occurred in the vertical distribution of
the abundant species. Most members of all species remained close to the
bottom during the day and mostly in the lower half of the water column
at night. But, freshwater drum larvae seem to move toward the bottom
almost immediately after hatching from their floating eggs, and remain
closer to the bottom during the day than other species. Yellow perch,
smelt, and white bass also tend to avoid surface waters, at least more
so than the clupeids which are the least likely af all the species sampled
to avoid the relatively rapid currents near the surface. Therefore, a
larger proportion of the clupeids may be carried greater horizontal dis-
tances away from the points of origin than other species. Relatively
small proportions of the bottom oriented species are likely to be carried

long distances away from their hatching sites.
Entrainment Susceptability

Counting entrained animals alone cannot reveal what impact a once—
through cooling system has on populations in the source waters. Data
also should be gathered in the source waters as well as the cooling system.
These results, similar to Marcy's (1971; 1973), point out that entrainment
probably does kill larvae at high rates. But, the sampling intensity re—
quired to identify an entrainment effect on lake populations depends on
what proportion of the population can be sacrificed to plant Operation
without endangering the fishery resource.

It is possible from the data presented here to tentatively estimate

the vulnerability of more abundant larval fishes to entrainment.

52

Table 8 was.constructed to show the relative impact of entrainment on
abundant larval fish populations near the west shore of Lake Erie. The
relative vulnerability of the population to entrainment was estimated by
using information gathered from the 16-km.transect, the proportion of
daytime and nighttime larvae in the water column, and the estimated rate

of water movements at different depths in the water column. It was assumed
that the proportions of larvae captured at each of the transect stations
was representative of a lake area between lines 8 km to the north and south
of the transect. Data from stations P10, P11, and P12 were used to es-
timate the abundances in the shore zone (within 4 km of shore) and abun—
dances in the three off shore zones centered on the transect where pro-
portioned in relation to known concentrations in the shore zone and the
percent captured at stations along the transect. All data from lake
stations P10, P11, and P12 and the cooling system were sampled at two

to three week intervals, and it was assumed that few if any larval co-
horts were sampled more than once. An estimate of the total abundance

of larvae present in the water column during the day was then calculated
for an area 16 by 16 km (approximately 10 percent of the shoreline and
area of the western basin). At average wind speeds, all of this area
could be within a one-week drift time to the plant intake.

Table 8 reveals that based on these estimates, there may be consider-
able differences in the vulnerability of species to entrainment. Of
course these estimates are crude because of the nature of the sampling
effort, but they give some indication of the magnitude of entrainment
impact. These estimates will be improved by further research efforts in
progress, but present indications certainly indicate that the proportions

entrained could be potentially fairly large for certain species, especially

53

emaaemm mcuawv ounce oLu mo Sumo Eouw unmac cam man one wcfiusv wonnunmo swam mo cowuuoaoua mnu Eoum
Azmc\Exv auflooam> mwmum>m mnu ma mHSHN

nonmasuamo we uH

.mm>oe cofiumasaoa mofiomam m umcu

 

 

 

 

 

 

 

 

 

NN.o NH oe.em om.em Nm.eamm mo.onN No.mam Nm.mNN mN
NN NN am.mm mm.wm so.osmu SN.NNm ss.meN am.mN SN auuma
NH NN mN.o om.sN Nm.mme we.s~N ou.mms Nm.mN MN SN o.mN m.o 3bNNmN
NH NN NN.N 4N.m me.Na mo.om am.mN mm.m mN
o Nm 0 Nm.ou Nm.msm SN.Nom oe.mN NS.N SN
NN.o NH NN.N NN.mw Nm.mNNm am.mNN oe.mee NN.MMN mN mN «.mN 0.0 DNAEN
Nm Nm mm.e wo.N om.meN ma.q~ es.m~ so.m me mmmn
NS NS so.s0N am.mNN mo.mo~ SN.qu mN.NNm «N.NNN SN ma N.ma N.o NANN3
NNN NSN em.m NN.ON NN.mH Nm.NN oa.s mo.m me
Nm NmN mm.NN am.mm mw.me om.ew mo.Nm as.me SN NH o.NN o.o mecNem
NsN Nae No.mm NN.NNH NG.NN wo.~e am.mNN NN.MNN me
Ne Nos NS.NNN am.wwe NN.NNm NN.NNN mw.NNs qm.waq SN
NN NNN cm.m ms.Nm w~.wm Hm.Nm so.Nm SN.oe me a S.N nail meNmasao
Nam Nee em.oN m.ms o 0 No.0 Ne.o mN
NNN Now we.NN NN.NN o o em.c m.NN «N N o.N .uzfi Esta
WEN Adam mumm mumm E 2 5 S E e E N ...; mmuoam N025 1A.; 33.2;
unmoumm - Ou
ucmficfimuucm quESfim-Hucm :mHOSm Cu Cowumfimm CH mumps—Dz Uwumfifiumm mkmn

 

 

Hzmo<hQ¢ >4ma<Hom22H mwmm mx<q zH 2M ca Mm 2M 0H <mm< 24 20mm Hz<4m mmzom mezzo: Mme

AmGONHHfiE a“ muonEDcv
.Hz<qm mmzom mza OH

H< HzmzzH<mazm OH :mHm A<>m<4 Hz<HmomzH ho wBHAHm<mMZAD> m>HH¢AmM amH<zHHmm

.m mNnme

54

.muosm scum museumfiv ouaummo came I n
was “macaw aouw noeumum uommamuu some «0 mocmumav I an unseen mafiaaaum Ham uo>o pummnmuu macaw coaummm
some um unwamo ma\umna=n I .u .uoomcmuu one wnoHs meouumum a Add us unmnmo ma\uoaana Hmuou I 9 specs

H

r-l
II
"-0

 

U:
u
Cid

.5 J

"finesse mums muflsmmn one new

mnocm Eoum wocmuwfib man up wwwaaauane coca mm3 cowumum some um wounuamo coauuoaoua one .pmuaommuamn

cofiumum nowmcmuu some Hence one mo coauoaoua one one“ uommcmuu one mcoam cwusuamo mmfiomam some now
mm>um~ mo hogan: Hmuou one wcflcofiuuoaam an nmumanoamo mmz muonm 50pm museumfic nephews some msew

.noaumaaaoa mo huwooao> Hmuaouwuon amps

u m> was .moamENm swam news mouse mo Hones: I x “mumuum mo unease I a “munmmoumou nonsnn some mouse

mo cowuuoaoun I zm..mus unwaahmv mo dowuuoaoum I am “wumuum swamp some you unwaa one wnwwae uneduamo
mE\umpE:c came I .z 000:3 .mumuum xenon some you >mn mzu wcaunp wounuamo mE\umnE:c came I we when:

op—l

w #HuwH" 4
.0 w
an

(1 N
H
II
n—o

 

"-0

 

 

"Aumma
.comcfinuusmv ucmuuso mummunm ecu mo NOH noncommuamu uCDHNSU down wnu wages >uHoon> mews ucmuasmou

cmme one No NN ucmmmunmu ou bossmmm mums mmfiufioofim> ucmuuso umumzwfie new momuusm new: .mumuum Ham
em>o cessam muaammu one can Enumuum umsu uo~.%uaooam> umum3 pmumeumm can an vofiaafiuase mma wousuamo
:oHupoaoue may .ucmmmue cowumasaoa Hmuou ecu mo nofiuuoaoua w voucommuamu Enumuum 50mm .mu: OH on cu
amasmmm mp3 oENuuswwa use me: q. on on cmeammm mmz meNumma .nmusuamo mum3 ow>nm~ umzu mouse Ham um>o

55

.o.m nowumum um uswsw0ma\uonasa I :u

was .m.m noaumum um unwamoma\umnasn I mu .¢.m nowuwum um unm5m0ma\uuaa=a I «u .uoomamuu one
macaw maoaumum q Has an pamsmona\umna=n Hauou I H .uouoom season aw mono I am “nauomm uoomawuu
than» aw mops I m4 .uouomw vacuum ea some I m< "Au unamfimv uouuom uuomamuu umuam SH menu I ~¢
.a m mo nuamv m ou A53 e x o.v «Hm new ...m .OHm wdavqsouunm «one no maaao> I > mumn3 .muauamo
mo mouse flaw um>o Anna. SH mm nowuwum uov N.m use ...m .o.m soauuum umma\noumo same n.m muons

i: ...> . a a 3
E3 .m> . ..w n 3
ES .~> . "a. u 3

H> . ....H. n J

"vmaNEpmuop mms HOuomm uommcmnu some GHLuNB Hones: can use wDGHEumumb.mm3 moum Ex 0.
x ca m CasuHB ucmmmua Hmuou mnu .mmma a“ uommcmuu ecu mcoaw conduamo mm>umH mo coauuoaoua nofina
one mafia: .mocHEuouov mmz wasao> umnu manufia om>umH mo woman: one new .5 m mo :uaow some a Leas
vmumanoamo mm: Ex q x ca moan cm cfifiuw3 manao> one .ucmmmua on ou nmumEfiumm one: mm>nma meNu one
wcausc cofiumum uummnmuu ccoomm one ou museumfiv one mam: mead ex N umpam mcu seguNB muauamo HmuON
mnu noncommuaou muonm mo Ex N cfinuwa Ammma :H mco uov mcouumum mama mmucu one um Looms came one
wagesmmm >3 nonmasoamo mm3 muosm Scum mmocmumwc ucmumwmfiu um ucmmmua menses: wmumEHumm mcH:

:

mined u I?
m

“zuwooam> Hmucoufiuo; counmama one >2 muonm eoum mocmumwn wusuawo came one wchH>Hw an
nonmanofimo was ocean Meson mnu um mxmucfi mzu Ou mm>umH o>oe Ou m>mn no women: mwmum>m seem

56

.ummcmccoo wnu nmzounu mmma Cu vmumEHumm punssc Esefixme ecu an
sewumasaoa mxma vmumEHumm mzu mzficfi>ww ma cmumasuamo mas mwmmmma ummcmvcou Hmuou ucmuummo

.mmum Ex 0H x ca m aficuws ucmmmua mp ou nmumEHumm mm>uma mo amass: HmuOu «nu cu
unmecwmuucm Esefixme HmUfiumuomcu mnu mafiumasoo an wmumaauamu mmB unmEcwmuucm HmuOu ucmuumms

285: a

ummcwwcoo cmsousu mmma cu wm>uma no pages: wwumefiumm
Ammmw «H n musuamo mo mzmwv ucwmwua ma ou vmumefiumm mm>uma mafiu mo Luwcma

Hmcmo mwumnumfiv uwaa: a“ ownsuamo mE\mm>umH mo umpesc cams

ll
0|: .422

m>onm mm

.ucmmmua mm>umH mo “mass: Hmuou mnu wcfivamfih vowuma mafia manmumaeou m wcfiusu
vmassa “mums mo ucsoEm Hmuou mnu an wmfiaafiuass cmnu mm3 umpeac mane .ucmmmua ma cu woumefiumm muma
mm>uma may mxmw mo umnesc HmuOu ms» >2 wmfiaawuass was Hmcmu wwuwnumwv “man: mnu :H vmusugmu mm>uma mo

mE\umnE:: cams wch .mumu wcflassa umm\mE mm cm vmesmwm wwwmmma ummcmvcou ESEmeE Hmofiumuomsu mcem

U H

3:: J - H

cw ll
0r-‘

 

> U

"ucmmmua mm>uma vowuma um>o

uwcwmuucm mm>umH mafium>wu u Wm mucmmmua on cu wmumsfiumm mm>umH AqH + mumv amusuamUV mefiu mo Luwcma

u A uvmufiscmu ma .uOuumm unmommvm Eouu mesao> Hmcowufinvm cam uummcmuu mo nanomm umufim casuws mszao>

u > mwmufiacmu ma .HOuumm ucmumnwm scum wm>umH HmGOfiqucm mam mafia neuomm uummcmuu umufiw ca mm>umH

u o .vmcfimuucm mumnesc vama> cu Heuuwm uommcmuu mcu a“ uammmua amass: mnu mwefiu wwfiaafiuaza mma

ucwuuma maze .vmcamuucm mm>uma mo umnsac mwmucmuuma msu cmucmmmuamu omHm ucmuuwa umnu cam cmumasoamu

mm3 neuumm uommcmuu nomm Eouw ww>fiumu umuma «nu mo ucmuuma one .mmmum wcflvmmoosm wnu up ume

mp waaoz mucmEmufiavmu HmGOHuchw mam maas3 mmum Exaqomumfivmeafi msu scum %Haumsflua vmcwwuno ma cu

vmszmmm was umums mfiLH .muawEmuwswwu “mums wme HmuOu mzu vamfim ou ucmmmua up vfisoa mmfiomam Hm>nma

umH30fiuuma m mafia mo :uwcmH may cu umumaoamuuxw was wmo uma mucwEmufiavmu “mums mme cams cmuswwmz mze

.vmusaaou was acmEmufinumu uwumz mxma mafimv came m .ucmmmpa mums mmpuma any nucoe comm pom uw>Hu wsu

Boum ucaoEm mzu ou cmumasou mxma mnu aouw vm>fiumv umums mo uczoam mnu wcfiunwfims zm .Aumm\mEmmv
umums mafiaoou mo magmasa Esefixme wcassmwm an kumEHumm mm3 acmecfimuucw mxmfl Esefixme Hmoauwuomshm

57

freshwater drum and clupeids. Assuming the study area is roughly repre-
sentative of the whole basin, less than 1 percent of most fish populations
are being entrained at the plant. However, from 5 to 15 percent of the
drum and clupeid larvae may be entrained. Based on theoretical consider-
ations of commercial catch and fecundities, Nelson and Cole (1975) estimat-
ed similar percentages. At the present time, the intake at the Monroe
Power Plant exceeds the intake of all other cooling waters taken from the
western basin of Lake Erie about 2 to 1. However, future expansion on

the Great Lakes may require 10 times the present cooling needs over the
next few decades. Therefore, the potential mortality percentages in

drum and clupeids border on those that may have a measurable impact on
adult populations, especially in the distant future.

Jensen (1971) has indicated that reduction of as little as 5 percent
in recruitment may eventually affect the adult population of at least one
species of fish. However, this is debatable, since Beland (1974) has
questioned Jensen's conclusions and there have been no empirical studies
published that verify these kinds of projections. Determining a 5 percent
impact on recruitment with statistical confidence for any particular
year of study would demand a much more intensive sampling effort than
that executed during this study because of the high variability in larval
fish distributions.

The variability is derived from vertical and horizontal variation,
and temporal variation caused by-changing rates of larval recruitment.
Although variability at a particular sampling site in the lake may be
only moderately high, the variability among different stations only a few
kilometers apart often is high and inconsistent from one day to the next.

This "patchiness" greatly affects any assessments of change in population

58
abundance within the cooling system as well as estimates of the proportions
of lake populations that are entrained. We do not know enough about the
lengths of time that larvae are susceptible to net capture and the prob-
ability of overestimating or underestimating the actual number of larvae
recruited into the lake population. At the intensity of sampling applied
during these studies, the annual entrainment of populations may be reason-
ably estimated, at a 95 percent confidence interval, within 100 to 1000
percent of the mean.

Variability in the lake is as great as variability in the cooling
system. The intensity of sampling in the lake must consequently be com-
parable to that in the cooling system to produce similar confidence in-
terval proportions.

There could be a prohibitively great expense involved in generating
precise enough estimates of entrainment proportions that would be meaning-
ful to the resource manager. But, one sampling method which could be
applied to reduce variability would be to pool temporal variation by con-
tinuous sampling procedures using pumping devices. Although this is a
reasonable approach for sampling most cooling systems, formidable techni-
cal and economic problems thwart any continuous larval fish sampling
scheme in the source waters.

Taking into consideration the exploratory nature of these pilot
studies, there'is a need to refine estimates. However, there does not
appear to be any immediate indication that the power plant is extremely
destructive to larval fish life, particularly to recreationally and com-
mercially important species. Future estimates of larval fish distribution
and potential entrainment could be improved in several ways. Almost all

of the fish are most vulnerable to entrainment at night because they are

S9

in the faster moving waters nearer the surface. Therefore, horizontal
distributions would be better estimated at night anywhere night navigation
is feasible. The actual growth rate of larval fish and their capacity to
avoid net capture as they grow should be better evaluated. Also, the
relative vulnerability of larval fish to natural mortality should be iden—
tified as it relates to distribution. Are near-shore populations more
likely to die from natural causes than offshore populations? Are hatches
in the tributaries more likely to survive to reproductive age classes

that hatches in the lake? Answers to these questions will provide infor-
mation for suitable coastal zone management including appropriate siting

and operation of cooling systems.

REFERENCES CITED

REFERENCES CITED

Barnes, H. and S. M, Marshall. 1951. On the variability of replicate
plankton samples and some applications of "contagious" series to
the statistical distribution of catches over restricted periods.
J. Mar. Biol. Assoc. U. K., 30:233-263.

Beeton, A. M. 1961. Environmental changes in Lake Erie. Trans. Amer.
Fish. Soc. 90:153-159.

Beland, P. 1974. On predicting the yield from brook trout populations.
Trans. Amer. Fish. Soc. 103(2):353-355.

Bishai, H. M. 1960. The effect of water currents on the survival and
distribution of fish larvae. J. Cons. Int. Explor. Mer. 25(2):

Carr, J. F., V. C. Applegate, and Ma Keller. 1965. A recent occurrence
of thermal stratification and low dissolved oxygen in western
Lake Erie. Ohio J. Sci. 65(6):319-327.

Cassie, R.‘M. 1959. An experimental study of factors inducing aggrega-
tion in marine plankton. New Zealand J. Sci. 2:339-365.

Cassie, R. M. 1962. Frequency distribution models in the ecology of
plankton and other organisms. J. of An. Ecol. 31:65-91.

Clutter, R. I. and M. Anraku. 1968. Avoidance of samplers. Monogr.
Oceanogr. Methodol. 2:57-76.

Cole, R. A. 1976. The impact of thermal discharge from the Monroe
Power Plant on the aquatic community in western Lake Erie. Tech.
Rep. No. 32.6. Institute of water Research, Michigan State Univer-
sity, East Lansing, Michigan. 571pp.

Cushing, D. H. 1961. Patchiness. Rapp. Proces. Verb. Cons. Internat.

Detroit Edison Company, The. 1976. Monroe Power Plant Thermal Discharge
Demonstration. The Detroit Edison Company. 2000 Second Avenue,
Detroit, Michigan.

Ecker, T. J. and R. A. Cole. 1976. Chloride and nitrogen concentra—
tions along the west shore of Lake Erie. Tech. Rep. No. 32.8.
Institute of water Research, Michigan State University, East Lan-
sing, Michigan. 132 pp.

60

61

Edsal, T. A. and T. G. Yocum. 1972. Review of recent technical in-
formation concerning the adverse effects of once-through cooling
on Lake Michigan. U. S. Fish and Wildl. Ser., Great Lakes Fish
Lab., Ann Arbor, Michigan. Unpublished.

Faber, D. J. 1967. Limnetic larval fish in northern Wisconsin lakes.
J. Fish Res. Ed. Can., 24(5):927-937.

Gill, J. L. 1971. Analysis of data with heterogeneous variance: A
review. J. Dairy Sci. 54(3):369-373.

Gill, J. L. In press. Design and analysis of experiments in the animal
and medical sciences. Iowa State University Press.

Hartley, R. P., C. E. Herdendorf, and M. Keller. 1966. Synoptic water
sampling survey in the western basin of Lake Erie. Proc. Ninth
Conf. Great Lakes Res., Inter. Assoc. Great Lakes Res., Ann Arbor,
Michigan. Pub. 15:301-322.

Hutchinson, G. E. 1957. A treatise on limnology. Vol 1. Geography,
physics, and chemistry. John Wiley and Sons, Inc., New York, N. Y.
D 0 265-295 0

Icanberry, J. W. and R. W. Richardson. 1973. Quantitative sampling of
live zooplankton with a filter-pump system. Limnol. and Oceanogr.
18(2):333-335.

Jensen, A. L. 1971. The effect of increased mortality on the young in
a population of brook trout, a theoretical analysis. Trans. Amer.
Fish. Soc. 100(3):456-459.

Kelley, J. E. and R. A. Cole. 1976. The distribution and abundance of
benthic macroinvertebrates along the western shore of Lake Erie.
Tech. Rep. No. 32.7. Institute of Water Research, Michigan State
university, East Lansing, Michigan. 77 pp.

Marcy, B. C., Jr. 1971. Survival of young fish in the discharge canal
of a nuclear power plant. J. Fish Res. Ed. Can. 28:1057-1060.

Marcy, B. C., Jr. 1973. Vulnerability and survival of young Connecti-
cut River fish entrained at a nuclear power plant. J. Fish Res.

Miller, D. 1961. A modification of the small Hardy plankton sampler
for simultaneous high speed plankton hauls. Bull. Mar. Ecol.
5:165—172.

Miller, D. J., J. B. Colton, Jr., and R. R. Marak. 1963. A study of
the vertical distribution of larval haddock. J. Cons. Int. Perm.
Explor. Mer. 28:37—49.

62
Nelson, D. and R. A. Cole. 1975. The distribution and abundance of
larval fishes along the western shore of Lake Erie at Monroe, Mich—
igan. Tech. Rep. No. 32.4. Institute of water Research, Michigan
State University, East Lansing, Michigan. 66 pp.

Noble, R. L. 1970. An evaluation of the Miller high-speed sampler for
sampling yellow perch and walleye fry. J. Fish Res. Ed. Can. 27(6):
1033-1044.

Saville, A. 1965. Factors controlling dispersal of the pelagic stages
of fish and their influence on survival. Spec. Publ. Int. N. W.
Comm. Atlant. Fish., 6:335-348.

Silliman, B. P. 1946. A study of variability in plankton tow-net
catches of Pacific pilchard (Sardinops caerula) eggs. J. Mar. Res.

Taylor, C. C. 1953. Nature of variability in trawl catches. U. S.
Fish and Wildl. Serv., Fish. Bull., 54(83):145-166.

Tranter, D. J. 1963. Comparison of zooplankton biomass determinations
by Indian Ocean standard net, Juday net, and Clarke-Bumpus sampler.
Nature. 198(4886):1179-1180.

Vanucci, M. 1968. Loss of organisms through the meshes. Monogr.
Oceanogr. Methodol. 2:77-86.

Wichstead, J. H. 1963. Estimates of total zooplankton in the Zanzibar
area of the Indian Ocean with a comparison of the results with two
different nets. Proc. 2001. Soc. Lond. 141(3):577-608.

Wiebe, P. H. 1971. A computer model study of zooplankton patchiness
and its effects on sampling error. Limnol. and Oceanogr. 16:29-38.

APPENDIX

63

TUKEY'S POST-HOC COMPARISON OF MEAN CATCHl USING

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table A-1.
DIFFERENT SAMPLING TECHNIQUE32 .
Clupeids
5-21 F A C D E
Mean 0.2314 0 0 0 0
5-23 C F D A E
Mean 0.4823 0.2891 0.1214 0 0
5-24 F A C D E
Mean 0.0698 0 0 0 0
6-18 G H C A F D E
Mean 2.7101 2.4386 1.7411 1.2800 1.1721 1.1294 0.5678
6-19 G C F D E A H
Mean 1.8491 0.8921 0.8265 0.3387 0.1200 0 0
6-20 G F D A C E H
Mean 2.0791 0.2868 0.2341 0.1821 0 0 0
Yellow Perch
5-21 C D E F A
Mean 0.6104 0.4434 0.3422 0.2891 0 V
5-23 C F D E H
Mean 0.5281 0.4434 0.2287 0.1241 0
5-24 D E F C H
Mean 0.1832 0.1241 0.0713 0 0
6-18 G H E C F D A
Mean 0.9522 0.6926 0.4434 0.0720 0.0611 0 0
6‘19 G E F H C D A
Mean 0.4934 0.0700 0.0700 0.0700 0 0 0
6-20 G C D E F H A
Mean 0.5741 0 0 0 O 0 0

 

Table A-1 (cont'd.)

64

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

White Bass
5-23 B F A C D
Mean 0.2301 0.1421 0 0 0
5-24 B A C D F
Mean 0.1792 0 0 0 0
6-18 G H F D C A
Mean 1.4214 0.5687 0.4891 0.3398 0.1821 0
6-19 G D E F A C
Mean 1.3478 0.1184 0 0 0 0
6-20 G D E F A C
Mean 1.3921 0 0 0 0 0
Smelt
5-21 F D C E A
Mean 0.5687 0.4421 0.2884 0.2315 0
5-23 F E C D A
Mean 0.3922 0.1794 0.1794 0.1211 0
5-24 B F A C D
Mean 0.2913 0.0695 0 0 0
6-18 G C D E F H
Mean 2.6871 0.8867 0.8001 0.8001 0.7619 0.1821
6-19 G H F E D A
' Mean 1.3211 0.1800 0.1800 0.1245 0.1245 0
6-20 G A C D E F
Mean 0.4920 0 0 0 0 0

 

65

Table A-1 (cont'd.)

 

 

 

 

 

 

Shiners

6-19 G C F E D H A
Mean 1.4234 0.8849 0.7284 0.4911 0.2902 0.1821 0

6-19 G A C D E F H
Mean 0.5342 0 0 0 0 0 0

6-20 G D A C E F H
Mean 0.3871 0.1189 0 0 0 0 0

 

 

1Mean corrected for normality and homogeneity by 1143(x + l) transformation.

2 = Kenco pump

= Surface net tow
= Midwater net tow
Deep net tow

Oblique net tow
Bottom sled
Modified Hardy Plankton Sampler

IOWMUO>

Table A-2. COMPARISON OF MEAN CATCH BY DIFFERENT SIZES OF MESH IN I'M PLANKTON NETS.

 

 

06/20/75
363p 57lu1000u

05/21/75 06/18/75
3630 57thOOOu

363p 571u10000

05/20/75
3630 5710 10000

 

 

 

 

 

Clupeids

5.2 0.0 0.0
0.0 1.0 0.2

0.4 0.0 0.0 0.8 0.0 0.0
11.2 7.6 8.0

12.4 1.6 0.0

Prolarvae

6.6 4.4 0.0 1.6 0.6 0.0

Postlarvae

Yellow perch

3.6 2.4 0.0 0.2 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
0.4 1.8 0.0 0.0 0.0 0.0

2.6 8.0 0.2

Prolarvae

0.4 0.0 0.0

Postlarvae

White bass

66

0.0 0.0 0.0
0.0 0.0 0.0

0.0 0.0 0.0 0.0 0.0 0.0 0.2 0.0 0.0
0.0 0.0 0.0 0.0 0.2 0.0

0.0 0.0 0.0

Prolarvae

Postlarvae

Smelt

0.0 0.0 0.0
0.0 0.0 0.0

0.0 0.0 0.0

1.2 0.2 0.0
0.8 0.4 0.0

0.8 0.2 0.0

0.4 1.6 0.0

Prolarvae

0.0 0.4 0.4

Postlarvae

Shiners

0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
0.0 0.0 0.0

0.0 0.2 0.0

Prolarvae

0.6 0.0 0.0

1.4 0.2 0.0

Postlarvae

5.8 1.0 0.2

14.0 8.4 8.4

4.6 3.0 0.0

26.4 18.4 0.2

Total

 

67

MEAN CATCHI FOR LENGTH OF

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table A—3. TUKEY'S POST-HOC COMPARISON OF
TIME TOWED2 .

Clupeids

5-20 3 2 5 1 4
Mean 0.5621 .5243 0.3384 .3121 0.2818

5-22 1 5 2 3 4
Mean 0.3621 .1498 0.0821 .0645 0.0641

6-18 2 4 3 5 1
Mean 1.6592 .4234 1.2491 .1810 1.0498

6-19 5 1 3 2 4
Mean 1.4011 .2659 1.2541 .1000 1.0681

Yellow Perch

5-20 2 5 4 l 3
Mean 0.1834 .1592 0.1510 .1434 0.1211

5-22 3 2 4 1 5
Mean 0.2664 .2311 0.1441 .1422 0.0291

White Bass

6-18 5 3 4 2 1
Mean 0.1413 .1211 0.0941 .0813 0

6-19 1 5 3 4 2
Mean 0.3738 .2014 0.1876 .1711 0

Smelt

5-22 2 l 3 4 5
Mean 0.3891 .2210 0.2114 .1847 0.1181

6-18 1 5 2 3 4
Mean 0.2311 .1842 0.0834 .0834 0.0414

6-19 4 5 1 3 2
Mean 0.2231 .2231 0.1341 .1217 O

 

 

68

Table A-3. (cont'd.)

 

 

 

Shiners

6-18 3 4 5 2 1
Mean 0.2841 0.2408 0.2341 0.2184 0

6-19 4 5 3 2 1
Mean 0.1341 0.0689 0 0 0

 

 

 

1Means corrected for normality and homogeneity by log (x + 1).

21 = 1 minute; 2 = 2 minute; 3 = 3 minute; 4 = 4 minute; 5 = 5 minute
lengths of tow.

COMPARISON OF MEAN CATCH BY DIFFERENT LENGTH OF TIME TOWED IN A 571u, l—M, PLANKTON NET.

 

 

06/19/75

06/18/75

05/22/75

05/20/75

 

 

5

4

1
min min min min min min min min min min min min min min min min min min min min

 

Clupeids

2.8

1.3 3.2 2.0 0.8 1.5 0.7 0.3 0.2 0.2 0.5 18.0 18.0 18.1 17.0 14.7 19.8 13.3 20.0 13.1 26.3

0.0 0.0 0.2 0.2 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.3 0.0 0.5 0.0 0.0 0.3 0.8 1.7

Prolarvae

Postlarvae

Yellow perch

0.0 0.0 0.4 0.2 0.2 0.0 0.0 0.2 0.2 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

Postlarvae 0.6 0.7 0.2 0.3 0.5 2.0 0.9 0.9 0.3 0.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.1 0.0

Prolarvae

White bass

0‘
\O

0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.3 0.2 0.0 0.2 0.0 0.0 0.0 0.0 0.0

Prolarvae

0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.2 0.5 0.4 1.7 0.0 1.0 0.6 0.7

Postlarvae

Smelt

0.0 0.0 0.0 0.0 0.0 0.0 0.3 0.4 0.5 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

Prolarvae

1.1

0.0 0.0 0.0 0.0 0.0 1.3 1.4 0.4 0.3 0.4 1.9 0.3 0.2 0.2 '0.7 0.6 0.0 0.4 0.9

Postlarvae

Shiners

0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.2 0.0 0.0 0.0 0.0 0.0 0.0 0.0

Postlarvae 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.3 1.2 1.0 0.9 0.0 0.0 0.0 0.5 0.2

Prolarvae

1.9 3.9 2.8 1.5 2.2 4.0 2.9 2.1 1.5 1.0 19.9 20.2 19.1 19.2 16.9 22.1 13.6 22.2 16.9 31.1

Total

 

COMPARISON OF MEAN NUMBER CAPTURED AT EACH DEPTH STRATUM TO OBLIQUE CAPTURE ALONG

Table A-5.

THE 16 NM TRANSECT.

(No./ 100 m3)

 

 

STATION

 

P16

P15

P14

P13

 

Sur- Sur-
face Deep Mean Oblique face Deep Mean Oblique face Deep Mean Oblique face Deep Mean Oblique

Sur-

Sur-

Species

 

0.1

0.3

0.2 0.1

Clu eids
5/22

0.3

0.5 1.1 1.3
51.2 90.5 70.8 48.6

5/23
6/9

10.2 20.4 15.3 10.1

44.2 87.4 65.8 29.9

20.2 2.7 11.5 21.3

8.6 15.3 12.0 11.7

0.8

2.6 2.9 2.8
21.0 12.9 17.0 23.4

0.9 0.6 0.7
3.7

4.4 5.0
1.5 1.1 1.3

71.3 40.5 55.9 59.2

4.0 4.7

6/16

2.9

1.6
5.5 8.6 7.0 10.3

3.3

1.7 0.4 1.0
48.0 73.4 60.7 58.3

6/19

7/2

70

 

Yellow
Perch

10.8 8.4 9.6 14.2

3.5 4.5 4.0 3.0

0.8
1.6

0.5 1.0 0.8

0.2
0.3

0.4 0.3 0.4
0.5 0.3 0.4

0

5/22

7.4 9.7 12.0 10.8 10.0

0.2

7.4 10.1 8.8

1.8 1.7 1.8

5/23
6/9

0.5
0.1

1.0
0.2

0.1

0.4

0.4 0.9 0.6

6/16

White

 

Bass

0.3 0.3 0.3

0

0.1

0.2. 0.4 0.3
4.7 9.4 7.0

0.2 0

5/23
6/9

17.0 33.3 25.2 18.4

2.6

3.6
0.2

3.4 1.7

0.3
0.6

0.3 0.2 0.3 0.2 0.2

0.6

0.3 0.6 0.4
0.2 0.3 0.2

0.2 0.3 0.2

0

6/16

0.2

0.2 0.3 0.2

0.4

0.4 0.4 0.4

1.2
0.3

0.6 0.7 0.7

6/19
7/2

1.2 2.5 1.8 2.2

1.2

1.7 3.4 2.6

0.2 0.4 0.3

 

(cont'd.)

Table A-5.

 

 

STATION
P14

 

P16

P15

P13

 

Sur-

Sur-
face Deep Mean Oblique face Deep Mean Oblique face Deep Mean Oblique face Deep Mean Oblique

Sur-

Sur-

Species

 

25.2

24.4 37.4 30.9

46.0 87.4 66.7 41.9

4.1
6.8

3.2 6.4 4.8
6.6 13.2 9.9

0.2 0.1 0

0
0

Smelt
5/22

47.0 89.5 68.3 40.8

29.5 58.6 44.0 22.5

0

5/23
6/9

1.4

3.2 1.7 0

2.2 4.3

1.1

0.3 1.0 0.6
0.6 1.2 0.9

0

0
0

0.3

1.3
0.2

1.0

2.0

6/16

71

0.1

0.2 0.4 0.3

0

6/19

 

Shiners

9.1

11.5 13.5 12.5

2.2 2.2
0.4 0.5

1.9 2.6
0.7

0.1 1.8 0.7 1.2 1.6
0.8

0.3

0.2 0.3

6/9

1.2
0.1
3.9

1.4 0.6 1.0
0.2 0.3 0.2

1.1 0
0.2

0.4

1.0 0.8
0

1.1

1.0
0

6/16

0.1 0.1

0

0.2

0.4 0.4 0.4

6/19

5.9 2.3 4.1

3.5 4.8 2.4 0.8 1.6 2.2 2.4 0.3 1.4 2.5

1.6

5.3

7/2

 

72

TUKEY'S POST-HOG COMPARISON OF MEAN CATCH1 ALONG THE TRANSECT.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table A—6 .
Clupeids
5-22 P15 P13 P14 P16
Mean 0.0614 0.0411 0 0
5-23 P13 P14 P15 P16
Mean 0.0841 0 0 0
6-9 P13 P15 P14 P16
Mean 1.6341 1.3412 1.0114 .0621
6-16 P16 P15 P13 P14
Mean 1.0514 0.6278 0.5932 .4241
6-19 P14 P16 P13 P12
Mean 0.6123 0.4935 0.2761 .2218
7-2 P13 P14 P15 P16
Mean 1.7562 1.7119 1.3694 .8791
Yellow Perch
5-22 P16 P15 P14 P13
Mean 0.9641 0.4879 0.2278 .0608
5-23 P16 P15 P14 P13
Mean 0.8438 0.6911 0.1305 .0381
6-9 P15 P16 P14 P13
Mean 0.0634 0.0315 0 0
6-16 P13 P15 P14 P16
Mean 0.1211 0.0315 0 0
White Bass
5-23 P13 P15 P14 P16
Mean _0;0401 0.0294 0 0
6-9 P16 P14 P15 P13
Mean 1.0391 0.4915 0.3294 0.1011
6-16 P14 P13 P15 P16
Mean 0.1401 0.1295 0.0962 0.0811

 

Table A-6.(cont'd.)

73

 

 

6-19
Mean

Mean

Smelt

5-22
Mean

5—23
Mean

Mean

6-16
Mean

6-19
Mean

7-2
Mean

Shiners

6-9
Mean

6-16
Mean

6-19
Mean

7-2
Mean

 

 

 

 

 

 

 

 

 

 

 

 

 

 

P13 P15 P14 P16
0.3001 0.1609 0.1237 0.0811
P15 P14 P13 P16
0.3421 0.2767 0.1000 0.0941
P15 . P16 P14 P13
1.5654 0.3321 0.5109 0.0314
P16 P15 P14 P13
1.4237 1.0642 0.6281 0
P16 P15 P14 P13

0.3101 0.3049 0.2791 0
P14 P13 P15 P16
0.3017 0.2512 0.1776 0.0314
P13 P14 P15 P16
0.0641 0.0291 0 0
P14 P13 P15 P16
0.0294 0 0 0
P16 P15 P14 P13
0.9676 0.4681 0.3933 0.02943
P16 P13 P14 P15
0.3574 0.2341 0.1901 0.1617
P14 P16 P15 P13
0.0651 0.0651 0.0286 0
P16 P13 P15 P14
0.8125 0.6850 0.4623 0.4117

 

 

74

Table A-6. (cont'd.)

 

 

Freshwater Drum

 

 

6-16 P13 P15 P14 P16
Mean 1.0487 0.0321 0 0

6-19 P13 P16 P14 P15
Mean 0.0938 0.0611 0 0

7-2 P14 P13 P15 P16
Mean 0.0294 0 0 0

 

 

1Means corrected for normality and homogeneity by log (x + 1)
transformation.

75

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table A-7. TUKEY'S POST-HOG COMPARISON OF MEAN CATCH1 AT STATIONS
SAMPLED IN 1975.
Clupeids
5-12 P10 P7 P3 P0 P2 P11 P6 P12
Mean 0.3868 .3785 0.3396 .3365 0.1981 .1410 0.0600 0
6-2 P2 P7 P10 P0 P3 P12 P11 P6
Mean 1.5862 .5369 1.3492 .3260 1.1942 .0841 0.7589 0.0571
6-25 P2 P11 P3 P10 P12 P7 P0 P6
Mean 0.9488 .8373 0.7046 .4687 0.3932 .3899 0.2943 0
7-9 P11 P6 P3 P10 P0 P12 P2 P7
Mean 1.4581 .0628 0.9257 .6137 0.5821 .4586 0.4537 0.0719
7-31 P6 P0 P10 P11 P12 P2 P3 P7
Mean 0.0634 .0170 0 0 0 0 0 0
Yellow Perch
5-12 P12 P7 P2 P0 P10 P11 P3 P6
Mean 1.8012 .5293 1.4911 .4180 1.2440 .0256 0.3197 0.2982
6-2 P2 P11 P3 P12 P7 P10 P0 P6
Mean 0.4429 .4133 0.2174 .1418 .0663 .634 0.0461 0
6-25 P6 P0 P2 P12 P10 P11 P3 P7
Mean 0.0634 .0041 0 0 0 0 0 0
7-9 P6 P0 P10 P11 P12 P2 P3 P7
Mean 0.0601 .0146 0 0 0 0 0 0
White Bass
6-2 P11 P2 P7 P0 P3 P12 ' P10 P6
Mean 0.6601 .5245 0.4786 0.3909 0.2398 0.2027 0.1372 0
6~25 P6 P0 P2 P12 P2 P7 P10 P11
Mean 0.6499 .3617 0.2479 0.0571 0 0 0 0
7-9 P12 P6 P2 P10 P3 P0 P7 P11
Mean 0.2745 .2167 0.1206 0.0842 0.0842 0.0792 0 0

 

 

Table A-7.(cont'd.)

76

 

 

Shiners

5-12
Mean

6-2
Mean

6-25
Mean

7—9
Mean

7-31
Mean

Carp
5-12
Mean

Mean

6-25
Mean

7-9
Mean

7-31
Mean

 

 

 

 

 

 

 

 

P2 P12 P10 P11 P3 P7 P0 P6
0.1355 0 0 0 0 0 0 0
P6 P2 P3 P0 P11 P7 P12 P10
0.4101 0.3739 0.2745 0.2528 0 0 0 0
P6 P2 P0 P3 P7 P10 P13 P10
0.4428 0.3258 0.2788 0.2441 0.1267 0.1204 0.0927 0.0603
P6 P11 P0 P3 P2 P10 P7 P12
1.6458 0.6687 0.6096 0.6044 0.5784 0.2076 0.0632 0
P10 P7 P0 P6 P11 P12 P2 P3
0.0571 0.0571 0.0557 0 0 0 0<_fi 0
P2 P6 P0 P10 P11 P12 P7 P3
0.4183 0.0911 0.0777 0 0 0 0 0
P6 P0 P2 P3 , P7 P10 P11 P12
0.5358 0.3670 0.1655 0.1559 0.0634 0 0 0
P2 P6 P0 P3 P7 P10 P11 P12
1.2946 0.7114 0.3802 0.3298 0 0 0 0
P6 P0 P3 P2 P11 P7 P12 P10
1.1146 0.5798 0.3846 0.0927 0.0842 0 0 0
P6 P0 P7 P2 P3 P10 P11 P12
0.0634 0.0170 0 0 0 O 0 0

 

 

 

 

 

 

 

Table A-8.

77

COEFFICIENTS 0F VARIATION INCLUDING MEAN COEFFICIENT OF
VARIATION AT STATIONS SAMPLED IN 1974 AND 1975 FOR ABUNDANT SPECIES.

 

 

 

 

 

 

 

 

STATIONS
Species P6 P7 P2 P3 P10 P11 P12
Clupeids
5/29/74 73.9 99.3 45.6 54.6 30.2 39.0 62.3
6/11/74 73.1 131.7 51.8 29.2 44.6 17.7 26.0
6/21/74 45.4 0 107.0 24.8 60.3 63.2 51.4
7/1/74 36.4 46.9 20.7 23.2 79.4 40.8 33.0
7/15/74 39.9 101.5 48.3 64.6 35.4 30.0 32.8
7/26/74 118.2 154.9 71.2 70.0 49.0 24.6 107.6
Mean 75.3 87.0 56.3 42.9 49.0 35.2 51.4
5/12/75 138.5 244.9 130.0 0 84.0 142.1 116.7
6/2/75 36.9 244.9 56.7 16.7 79.0 56.1 38.7
6/25/75 65.6 0 82.7 55.9 81.6 61.6 81.3
7/2/75 52.2 244.9 93.5 34.8 74.8 53.8 152.1
Mean 73.2 153.0 75.6 22.4 66.5 65.4 81.0
Yellow Perch
5/10/74 0 44.7 21.4 36.1 Not Sampled . . .
5/29/74 43.8 244.9 78.1 98.6 39.4 45.5 64.1
6/11/74 47.0 244.9 34.7 37.8 244.9 0 164.7
Mean 30.3 178.2 44.7 57.5 142.2 22.8 114.4
5/12/75 110.1 112.5 49.3 73.4 63.7 43.9 39.0
6/2/75 306.2 0 95.6 118.6 244.9 113.9 173.3
Mean 208.2 56.2 72.4 96.0 154.3 78.9 106.2
White Bass -
5/29/74 244.9 244.9 155.0 33.9 83.4 244.9 94.6
6/11/74 127.8 165.9 90.1 44.1 88.8 143.0 46.2
6/21/74 244.9 0 0 167.3 0 0 0
7/1/74 110.2 0 244.9 244.9 0 0 244.9
7/15/74 80.0 0 90.0 72.2 95.0 108.3 244.9
7/26/74 244.9 0 72.9 244.9 125.5 226.4 114.0
Mean 175.4 68.5 108.8 134.6 65.4 120.4 100.6
Shiners
5/29/74 122.0 0 83.4 155.1 244.9 0 0
6/11/74 110.0 109.8 92.0 92.7 149.7 67.2 38.1
6/21/74 155.1 109.5 63.2 0 155.1 0 0
7/1/74 244.9 244.9 164.9 109.7 0 244.9 244.9
7/15/74 0 164.7 244.9 0 0 0 0
7/26/74 142.2 166.0 93.3 164.7 125.5 66.0 63.1
Mean 129.0 132.5 123.6 87.0 112.5 63.0 57.7

78

 

 

 

 

Table A—8. (cont'd.)
STATIONS
Species P6 P7 P2 P3 P10 P11 P12
5/12/75 0 0 160.2 0 0 0 0
6/2/75 0 53.9 123.4 61.2 0 0 0
6/25/75 154.9 109.3 115.6 244.9 155.6 244.9 127.0
7/2/75 244.9 31.2 61.4 62.8 168.0 53.7 0
Mean 99.9 48.6 115.2 92.2 80.9 74.6 31.8
Cagp
5/10/74 0 172.5 14.4 63.2 0 0 0
5/29/74 106.4 93.6 55.8 0 126.5 0 0
6/11/74 98.2 33.8 23.2 37.7 0 0 0
6/21/74 183.7 80.3 28.9 114.4 0 O 0
7/1/74 244.9 35.9 79.4 98.9 244.9 151.2 4.3
7/15/74 49.4 28.4 23.4 64.1 0 170.9 244.9
7/26/74 244.9 244.9 244.9 244.9 0 0 0
Mean 132.5 98.5 67.1 89.0 53.1 46.0 35.6
5/12/75 0 234.7 90.5 0 0 0 0
6/2/75 285.8 59.4 160.0 173.8 0 0 0
6/25/75 0 62.4 29.2 84.8 0 0 0
7/2/75 0 44.6 244.9 61.3 0 0 0
Mean 71.4 100.3 131.2 80.0 0 0 0

 

"I7'111'11111'1111’111'1'“