ADULT, JUVENILE AND LARVAL FISH POPULATIONS

IN THE VICINITY OF THE J- H. CAMPBELL POWER PLANT,

EASTERN LAKE MICHIGAN, 1977-1980

DAVID J. JUDE, HEANG T. TIN, GEORGE R. HEUFELDER,
PHILIP J. SCHNEEBERGER, CHARLES P. MADENJIAN, THOMAS L. RUTECKI,
PAMELA J, MANSFIELD, NANCY A. AUER, GEORGE E. NOGUCHI

Under contract with Consumers Power Company
David J. Jude, Project Director

Special Report Number 86

Great Lakes Research Division
The University of Michigan
Ann Arbor, Michigan 48109

November I98I

ACKNOWLEDGEMENTS

The successful completion of this research endeavor necessarily involved
the cooperation and help of numerous individuals. In addition to all those
individuals acknowledged in previous Special Reports 65» 73 and 79 of the
Great Lakes Research Division, the I98O field effort, and compilation of data
from 1977-1980 presented herein, have drawn upon the resources and expertise
of a number of additional associates. Sharon Klinger, who co-authored past
reports and was involved In much of the formation and improvement of the
project, has departed for the U.S. Forest Service in Alaska. We greatly
acknowledge her help and extend best wishes for continued success in the
future. The financial support provided by the Consumers Power Company,
Environmental Services Department, Jackson Michigan is acknowledged and
appreciated. The assistance and suggestions of Ibrahim Zeitoun and John
Gulvas are gratefully acknowledged.

Maintenance and smooth operation of our field station was largely the
result of the efforts of James Greiner, with commendable cooperation from
supervisory personnel at Campbell Units 1, 2 and 3« Access to our sampling
sites was graciously allowed by Lake Michigan shoreline residents Herbert
Norder and Roy Glutting. The successful collection of field samples would
have been impossible without the support of the crew of The University of
Michigan's R/V Mysis, Captain Cliff Tetzloff and first mates Earl Wilson and
Glen Tompkins. Their cheerful cooperation despite long and arduous hours is
greatly appreciated. We are indebted to a number of larval fish sorters and
adult fish processors including: Jeff Braunscheidel , Jim Greiner, Dennis
Mounsey, Jodie Schlott, Laura Black, Loren Flath, Jim Wojcik, Pam Humphries,
Phil Hirt, Sheryl Corey, Linda Cooley, Gerard Li 1 lie, Janet Huhn. Professor
Harvey Blankespoor of Hope College has aided us greatly in finding qualified
summer personnel as well as helping us on numerous occasions to process
samples. Jan Parr is and Linda Gardner deserve much credit for handling the
abundant detail involved in travel arrangements, equipment ordering, time
keeping, correspondence and record keeping, which was much needed to keep our
project afloat. Linda Gardner and Pam Downie are especially acknowledged for
their efforts in preparing this 4-yr summary. Nelson Navarre helped with
contract negotiations. Steve Schneider coordinated report reproduction.
Frank Tesar critically reviewed the report with his usual incisive style.
Illustrations in this text were prepared by Jeff Braunscheidel, Sheryl Corey
and Mary Sweeney. Alan Mansfield and Mary Vian De Weert also assisted in
report preparation. We greatly acknowledge the help of Steve Wineberg for
sharing his expertise on computer-drawn graphics in this report, as well as
Barb Ladewski for her help in developing programs for the word processing
unit. Arrangements for loans of various equipment were arranged by Frank
Tesar and Nancy Thurber, and are gratefully acknowledged. John Dorr Ml and
Karl Luttrell provided inestimable assistance in the SCUBA program, often
donating time and effort despite numerous other commitments. Final thanks go
to the spouses and loved ones of all the authors, who often endured their
absence with little complaint.

t i i

TABLE OF CONTENTS

ACKNOWLEDGEMENTS iii

LIST OF TABLES ix

LIST OF FIGURES y^]]\

INTRODUCTION • 1

STUDY AREA 3

METHODS 7

Introduction 7

Seining 7

Gillnetting 7

Trawling 9

Missing Adult and Juvenile Fish Samples 9

Fish Larvae Tows 9

S 1 ed Tows 12

Missing Larval Fish and Egg Samples 16

Fish Egg and Larvae Processing 16

Quality Assurance 17

Laboratory Analysis of Juvenile and Adult Fish 17

Data Processing and Calculations l8

Definition of Terms 19

SCUBA Observations 20

Statistics 23

Design and Analysis Considerations 2k

Power Analysis 30

Fish Larvae Analysis 32

RESULTS AND DISCUSSION 33

Total Catch 33

Most Abundant Species 55

Alewife 55

Rainbow Smelt 106

Spottail Shiner 142

Trout-perch 179

Unidentified Coregoninae 205

Yellow Perch 217

Less Abundant Species 255

Lake Trout 255

White Sucker 265

Johnny Darter 268

Emerald Shiner 271

Ninespine Stickleback 27^

Longnose Sucker 279

Slimy Sculpin 28l

Round Whitefish 28i+

Gizzard Shad 286

Chinook Salmon 288

Coho Salmon 289

Lake Whitefish 290

Brown Trout 292

Rainbow Trout 292

Golden Shiner 294

Common Carp 294

Silver Redhorse 297

Channel Catfish 298

Shorthead Redhorse 298

Burbot 299

Mottled Sculpin 3OO

Golden Redhorse 3OI

Longnose Dace 30I

Walleye 302

Central Mudminnow 302

Yellow Bullhead 303

Quillback 303

Deepwater (Fourhorn) Sculpin 303

Black Crappie 305

Freshwater Drum 305

Lake Herring 305

Northern Pike 306

Bluegill 306

Lake Sturgeon 306

Brook Silverside 307

Green Sunfish 307

Pumpkinseed 307

Logperch , 307

Smallmouth Bass 307

Bluntnose Minnow 308

Goldfish 308

Fathead Minnow 308

Damaged Larvae 308

Fish Eggs 318

Introduction . 31 8

Seasonal Distribution 319

Plant Effects 33I

SCUBA Observations 332

1977 332

1978-1979 334

1980 334

SUMMARY AND CONCLUSIONS 338

Introduction 338

Total Catch 338

Alewife 339

Rainbow Smelt 339

Spottail Shiner 341

VI

Trout-perch 3^^

Yellow Perch 344

Unidentified Coregoninae 3^7

Fish Eggs 3^9

SCUBA Observations 349

LITERATURE CITED 351

INDEX TO FISH SPECIES 363

APPENDIXES (1-11 in text) Al-AllB

(12-41 in microfiche) A114-A358

VI I

LIST OF TABLES (not exact table headings) Page

Table 1. Monthly sampling scheme (dates and stations sampled) for

juvenile and adult fish collections. 8

Table 2. Summary of juvenile and adult fish samples missing from

proposed monthly sampling, 1977*1980. 10

Table 3* Fish larvae sampling depths (m) . 11

Table 4. Example of computational procedures used to correct larvae

for upper level contamination, 14

Table 5« Experimental designs employed to analyze C.P.E. data for

the six most abundant species caught, 1977-1980. 26-28

Table 6. Descriptive statistics for C.P.E. data used in the

experimental designs for the six most abundant species

caught, 1977-1980. 29-30

Table 7. Least detectable true ratio (LDTR) for each experimental
design employed for the six most abundant species caught,
1977-1980. 31

Table 8. Family, scientific, common name and codes for all species

of juvenile and adult fish captured, I377-I98O. 38-40

Table 9. Taxons and abbreviations of fish larvae captured,

1977-1980. 1,1.42

Table 10. Summary of all species caught by all gear types,

1977-1980. kk-k5

Table 11. Summary of all species caught by seines, 1977-1980. 48-49

Table 12. Summary of all species caught by surface gill nets,

1977-1980. 50

Table I3. Summary of all species caught by bottom gill nets,

1977-1980. 51-52

Table 14. Summary of all species caught by trawls, 1977-1980. 53-54

Table I5-I8. Mean density of all species of larval fish

collected, 1977-1980. 56-59

Table I9. Analysis of variance summary for alewives caught in bottom

gill nets at stations C and L, 1977-1980. 103

Table 20. Analysis of variance summary for alewives caught in bottom

gill nets at stations C and L, I978-I98C. 103

ix

Page

Table 21. Analysis of variance summary for alewives caught in bottom

gill nets at stations C, D, L and N, 1980. 10i>

Table 22. Analysis of variance summary for alewives caught in

surface gill nets at stations C and L, 1977-1980. 10^

Table 23- Analysis of variance summary for alewives caught in

surface gill nets at stations C and L, 1978-1980. 105

Table 2k. Analysis of variance summary for alewives caught in seines

at stations P, Q and R, 1977-1980. 105

Table 25- Analysis of variance summary for alewives caught in trawls

at stations C and L, 1977-1980. 107

Table 26. Analysis of variance summary for alewives caught in trawls

at stations C, D, L and N, I978-I98O. IO8

Table 27- Mean density of larval rainbow smelt, 1977-1980. 123

Table 28. Number of rainbow smelt caught by all gear types,

1977-1980. 141

Table 29* Analysis of variance summary for rainbow smelt caught in

trawls at stations C and L, 1977-1980. 142

Table 30. Analysis of variance summary for rainbow smelt caught in

trawls at stations C, D, L, and N, I978-I98O. 143

Table 31- Analysis of variance summary for spottail shiners caught

in seines at stations P, Q and R, 1977-1980. l82

Table 32. Analysis of variance summary for spottail shiners caught

in bottom gill nets at stations C and L, 1977-1980. l82

Table 33* Analysis of variance summary for spottail shiners caught

in bottom gill nets at stations C and L. I978-I98O. I83

Table 34. Analysis of variance summary for spottail shiners caught

in bottom gill nets at stations C, D, L and N, I98O. I83

Table 35* Analysis of variance summary for spottail shiners caught

in trawls at stations C and L, 1977-1980. I85

Table 36. Analysis of variance summary for spottail shiners caught

in trawls at stations C, D, L and N, I978-I98O. I86

Page

Table 37- Analysis of variance summary for trout-perch caught in

trawls at stations C and L, 1977-1980. 205

Table 38. Analysis of variance summary for trout-perch caught in

trawls at stations C, D, L and N, I978-I98O. 206

Table 39* Total number of unidentified Coregoninae collected by each

sampling gear type, I977-I98O. 210

Table kO, Unidentified Coregoninae collected by each gear type,

1977-1980. 211

Table 41. Numbers of unidentified Coregoninae collected (various

stations combined) . 1977-1980. 212

Table k2. Gonad conditions of unidentified Coregoninae, 1980. 214

Table 43. Average length and standard error of YOY Coregoninae,

1977-1980. 215

Table 44. Analysis pf variance summary for unidentified Coregoninae

caught in trawls at stations C and L, 1977-1980. 219

Table 45. Analysis of variance summary for unidentified Coregoninae

caught in trawls at stations C, D, L and N, 1978-1980. 220

Table 46. Analysis of variance summary for yellow perch caught in

bottom gill nets at stations C and L, 1977-1980. 252

Table 47. Analysis of variance summary for yellow perch caught in

bottom gill nets at stations C and L, I978-I98O. 252

Table 48. Analysis of variance summary for yellow perch caught in

bottom gill nets at stations C, D, L and N, I98O. 253

Table 49. Analysis of variance summary for yellow perch caught in

trawls at stations C and L, 1977-1980. 253

Table 50. Analysis of variance summary for yellow perch caught in

trawls at stations C, D, L and N, I978-I98O. 254

Table 51. Occurrence of sea lamprey scars on lake trout caught,

1980. 263

Table 52. Number of lake trout gillnetted at stations C and L,

1977-1980. 264

XI

Page

Table 53. Summary of gizzard shad catch by age-groups, 1977"1980. 288

Table 5k. Densities of all species of larvae in samples containing

damaged larvae taken, 1977-1980. 310-316

Table 55. Summary of the abundance, distribution and temperature-
catch relationships for larval, juvenile and adult
alewife collected, 1977-1980. 3^0

Table 56. Summary of abundance and temperature-catch relationships
for larval, juvenile and adult rainbow smelt collected,
1977-1980. 3^2

Table 57. Summary of abundance, distribution and temperature-catch
relationships for larval, juvenile and adult spottail
shiner collected, 1977-1980. 3^3

Table 58. Summary of the abundance, distribution and temperature-
catch relationships for larval, juvenile and adult
trout-perch col lected, 1977-1980. 3^5

Table 59. Summary of abundance, distribution and temperature-catch
relationships for larval, juvenile and adult yellow perch
collected, 1977-1980- 3^6

Table 60. Summary of abundance, distribution and temperature-catch
relationships for larval, juvenile and adult unidentified
Coregoninae col lected, 1977-1980. 3^8

XI I

LIST OF FIGURES (not exact figure captions) Page

igure 1. Scheme of the Campbell Plant and the l8 sampling

stations. 4

igure 2. Scheme of various components of the intake and discharge

system for Units 1, 2 and 3* 5

igure 3* Schematic representation of adjustment calculations for

upper level contamination in larvae samples. 13

igure k. Benthic fish larvae sled. 15

igure 5« Scheme of Campbell Plant and the eight diving transects

swum, 1977- 21

igure 6. Scheme of Unit 3 manifold depicting site of SCUBA

observations, I979-I98O. 22

igure 7- Daily Lake Michigan water temperatures, 1977"'1980. 34"37

igures 8-I9. Density and length-frequency of larval alewives

collected at I-3. 6-9 and 12-15 m, 1977-1980. 62-73

igure 20. Mean density of larval alewives for north and south

transect stations, 1977-1980. 7^-77

igure 21. Length-frequency histograms for alewives collected at

north and south transects, 1977-1980. 82-89

igure 22. Mean bottom temperatures observed during monthly

sampling, 1977-1980. 92-9^

igure 23. Number of mature alewives with well developed, ripe-
running and spent gonads, 1977-1980. 97

igure 2k. Geometric mean number plus one of alewives caught in
bottom and surface gill nets at stations C and L,
1978-1980. 100

igure 25- Geometric mean number plus one of alewives caught in

seines at stations P, Q and R, 1977-1980. 101

igure 26. Geometric mean number plus one of alewives caught in

trawls at stations C, D, L and N, I978-I98O. 102

igures 27*36. Density and length-frequency of larval rainbow smelt

collected at I-3, 6-9 and 12-15 m, 1977-1980. IIO-II9

igure 37- Mean density of larval rainbow smelt for north and south

transect stations, I978-I98O. 120-122

Xi I i

Page

Figure 38. Length-frequency histograms for rainbow smelt collected

at north and south transect stations, 1977-1980. 128-135

Figure 39* Number of mature rainbow smelt with well developed,

ripe-running and spent gonads collected, 1977-1980. I38

Figure kO. Geometric mean number plus one of rainbow smelt caught

in trawls at stations C, D, L and N, I978-I98O. ]kk

Figures 41-52. Density and length-frequency of larval spottail

shiners collected at 1-3, 6-9 and 12-15 m, 1977-1980. 146-157

Figure 53* ^lean density of larval spottail shiners for north and

south transect stations, 1977-1980. 158-I6I

Figure 5^, Length-frequency histograms for spottail shiners
collected at north and south transect stations,
1977-1980. 166-173

Figure 55- Number of mature spottail shiners with well developed,

ripe-running and spent gonads collected, 1977-1980. 175

Figure 56. Geometric mean number plus one of spottail shiners caught
in seines at stations P, Q and R and in bottom gill nets
at stations C and L, I978-I98O. I80

Figure 57- Geometric mean number plus one of spottail shiners caught

in trawls at stations C, D, L and N, I978-I98O. 184

Figure 58. Length-frequency histograms for trout-perch collected

at north and south transects, 1977-1980. 188-195

Figure 59* Number of mature trout-perch with well developed, ripe-
running and spent gonads collected, 1977-1980. 200

Figure 60. Geometric mean number plus one of trout-perch caught in

trawls at stations C, D, L and N, I978-I98O.. 207

Figure 6I. Monthly average length of unidentified Coregoninae

collected in all sampling gear, 1977-1980. 208

Figure 62. Total number of different sizes of unidentified

Coregoninae collected, 1977-1980. 209

Figure 63. Length-frequency distribution of unidentified Coregoninae

collected by all gear, I98O. 213

XIV

Page

Figure Gk. Total number of unidentified Coregoninae caught in trawl

hauls at stations C, D. L and N, I978-I98O. 21?

Figure 65- Total number of unidentified Coregoninae caught in bottom

gill nets at stations C, D, L and N, I98O. 2l8

Figure 66. Geometric mean number plus one of unidentified

Coregoninae caught in trawls at stations C» D, L and N,
1978-1980. 221

Figures 67-77« Density and length-frequency of larval yellow
perch collected at l-3» 6-9 and 12-15 m, 1977-1980.

Figure 78. Mean density of larval yellow perch for north and
south transect stations, I978-I98C.

Figure 79- Length-frequency histograms for yellow perch collected
at north and south transect stations, 1977"1980.

Figure 80. Number of mature yellow perch with well developed,
ripe-running and spent gonads collected, 1977-1980.

Figure 8I. Geometric mean number plus one of yellow perch caught
in bottom gill nets at stations C and L, I978-I98O.

Figure 82. Geometric mean number plus one of yellow perch caught
in trawls at stations C, D, L and N, I978-I98O.

Figure 83. Numbers of lake trout fry collected in trawls and the
fish larvae sled, I98O.

Figure 8i*. Numbers of adult and juvenile lake trout collected in
all gear, 1977-1980.

Figure 85. Number of mature lake trout with well developed, ripe-
running and spent gonads collected, I977-I98O.

Figure 86. Number of white suckers collected by all gear, 1977-1980.

Figure 87. Total catches of ninespine sticklebacks by month for

south transect stations B through F, I978-I98O. 277

Figure 88. Number of mature ninespine sticklebacks with well

developed, ripe-running and spent gonads collected,

1977-1980. 278

Figure 89. Number of mature slimy sculpins with well developed,

ripe-running and spent gonads collected, I978-I98O. 283

XV

222-232

23it-236

238-245

249

251

255

257

258-259

262

267

Page

Figure 90. Mean density of larval carp for north and south transect

stations, 1977-1980. 296

Figures 9I-IOO. Density of fish eggs at all depths, 1977-1980. 320-329

XV I

INTRODUCTION

In 1975 Consumers Power Company, Jackson, Michigan began construction of a
third unit at the J. H. Campbell Power Plant, Port Sheldon, Michigan. It was
decided that the cooling water for this new unit would be drawn from Lake
Michigan via an offshore intake pipe with an opening at the 11-m depth
contour. The openings leading to the intake pipe were fitted with cylindrical
wedge-wire screens with 9-5"nim openings. The number and configuration of
screens were designed to supply adequate water for the cooling of Unit 3 while
creating a minimal withdrawing current of approximately 0.2 m/s. The former
discharge from Units 1 and 2 flowed through a canal opening at the shoreline
of Lake Michigan. This scheme was modified in 1979-1980 to an offshore
discharge structure which now accommodates the discharge from Units 1, 2 and
3. The number and configuration of diffusers at the end of the discharge pipe
were designed to mix discharge water with Lake Michigan ambient water to
promote mixing in the vicinity of the discharge structure so the change in
water temperature over ambient does not exceed 1.7 C within a 29-hectare
surface area (72 acres) .

To address environmental concerns, an extensive surveillance study in the
area was initiated. Environmental impacts of Units 1 and 2 on the fisheries
in the area were addressed in previous reports (Jude et al. 1978, 1979a, I98O,
1981a). Additional reports describing the effects of Units 1 and 2 on the
benthos of the area were also published (Winnell and Jude 1979, I98O) .

The present report includes data taken during 1977-1980 in Lake Michigan
near the Campbell Plant and is intended as a baseline data set against which
1981 operational data (Unit 3) can be compared. The entire I98O data set was
considered preoperational, since Unit 3 was infrequently operated in I98O
following its completion in September.

Our intent in designing the sampling scheme used at the Campbell Plant was
to establish a spatial and temporal pattern of gear deployment such that all
important species and sizes of fish that inhabit the Campbell Plant area were
collected. To this end, we incorporated different gear for both adult and
juvenile (seines, trawls, gill nets) and larval fish (pelagic net and sled
tows) sampling. We increased the intensity of our sampling of larval fishes
during the known spawning time of most abundant species (June, July, August).
We also sampled a wide range of areas (beach zone out to 15 m in Lake
Michigan) and we sampled during the day and night to obviate net avoidance and
to collect day-active and night-active species. Onshore and offshore
migrations could also be documented in this manner. In Lake Michigan, the
classical treatment vs. reference area experiment was established to assess
the future effects of the Unit 1, 2 and 3 discharge at 6 m and the Unit 3
intake at 11 m. A reference 6-m station about 3.1 km south has been fished
regularly with surface and bottom gill nets, trawls and larval fish nets.
Catches have been compared each year to establish whether differences exist
between the two areas so that this station on the south transect can act as a
valid control. During I98I, any effects of Unit 3 operation can be documented
by comparing catches between the two areas.

From 1977 to I98O, there have been a few minor changes in sampling design.
These will be specified in detail in METHODS. Our comparisons among years are
thought not to be seriously affected by these changes. This report will focus
on the Lake Michigan catches of larval, juvenile and adult fish. We will
establish the spatial and temporal variability observed in catches over the k
yr and document the patterns of spawning, local inshore and offshore
movements, migrations (immigration, emigration), nursery areas, effect of
physical factors such as water temperature and upwel lings on fish behavior and
some food eaten by selected species of fish will be discussed. Each major
species of f i sh col lected in Lake Michigan during our 1977"*1980 studies will
be discussed under headings of larvae, certain age-groups (YOY, yearlings,
adults) and plant effects. Less abundant species will be discussed in a more
general manner with efforts directed at seasonal distribution patterns, sizes
collected, sex ratios and any atypical behavior or presence noted.

STUDY AREA

The J. H. Campbell Power Plant is located on the eastern shoreline of
Lake Michigan in Port Sheldon Township (T6N, R6W) Ottawa County, Michigan
(Fig. 1). Land immediately surrounding the the 3-24-km^ site is classified as
'•dune'* area and is characterized by high sand dunes and bluffs (U.S. Army
Corps of Engineers 1971)- Within an 8-km radius of the plant, land is
primarily used for agriculture and forestry. The aquatic habitat immediate to
the plant exhibits considerable variation.

Situated directly south of the plant is Pigeon Lake, the natural
collecting basin for the Pigeon River before it enters Lake Michigan. The
drainage area of the Pigeon River (approximately 155 km^) supplies an average
flow of 1.12-1.26 m^/s to Pigeon Lake (Water Resources Commission I968) . The
present Unit 1 and 2 water usage of I8.7 m^/s for cooling condensers causes
the natural flow of Pigeon Lake into Lake Michigan to be redirected through
the plant. The balance of the water demand is supplied by Lake Michigan water
which is drawn into Pigeon Lake. Outflowing water from Units 1 and 2 is
discharged into a canal, which prior to 1979 opened at the shoreline of Lake
Michigan approximately 1 km north of the entrance of Lake Michigan into Pigeon
Lake (Fig. 1). Two stone jetties (366 m long) were constructed at the
entrance of Lake Michigan to Pigeon Lake to maintain a passage from Pigeon
Lake to Lake Michigan and thus ensure adequate flow of intake water for Units
1 and 2. A comprehensive ecological study of Pigeon Lake is presented by Jude
et al. (198la) .

The Lake Michigan area adjacent to the Campbell Plant receives
considerable use as a recreational resource. Many sport fishermen troll for
trout and salmon, and perch fishing is popular during the summer. Dipping for
smelt occurs during the spring. Sailing, swimming and camping are other
common recreational uses of the Lake Michigan shore zone.

Depth contours in the area of the plant run roughly parallel to shore
under normal conditions. However, during the study period, construction
activities associated with the Unit 3 intake and discharge structures often
resulted in abnormal sand bar formations due to extensive displacement of
large volumes of sand.

In 1973* construction began on an additional power generating unit (Unit
3) which would be situated adjacent to Units 1 and 2 and utilize a common
discharge canal. In order to minimize environmental impact, cooling water for
Unit 3 was to be drawn from Lake Michigan via an offshore intake pipe.
Construction of this offshore intake pipe was initiated in April, 1978. The
intake was to be of a branched arm design using 9»5""nim, wedge-wire screens
(see Zeitoun, et al. I98I and Fig. 2) extending to about the 11-m contour. In
addition to intake construction, construction of an offshore discharge, which
would accommodate the warmwater discharge of Units 1, 2 and 3» was initiated
concurrent 1 y .

Fig. 1. Scheme of the J. H. Campbell Plant showing Lake Michigan
and the 18 sampling stations (A, B, C, D, E, F, G, H, I, J, L, N,
0, P, Q, R, U and W) established for fisheries monitoring.

From
Pigeon LakeN

'7/

illUU/>«^ Intake Screen
ll-M DEPTH

Units 1 and 2 Discharge Pipe
Unit 3 Discharge Pipe

Discharge Nozzle
'6-M DEPTH

Lake Michigan

Fig. 2. Scheme of the J. H. Campbell Power Plant showing the various
components of the intake and discharge system for Units 1, 2 and 3.
Adapted from Randall and Landon (1981).

Water intake and discharge systems and water flow for the Campbell Plant
as of 1979 are illustrated in Figure 2. Intake water for Units 1 and 2
continues to be withdrawn from Lake Michigan through Pigeon Lake, while Unit 3
intake water comes from offshore intake structures located at the ll-m depth
contour. Cooling water for Unit 3 "S gravity fed into the intake canal, and
pumped from the canal into Unit 3 condensers* Discharges of all three units
are released into a common canal adjacent to the Unit 3 intake canal. Four
discharge pumps near the Lake Michigan shoreline pump the combined discharge
of Units 1, 2 and 3 offshore in Lake Michigan to the 6-m depth. A variety of
bypass mechanisms were incorporated into the entire intake system to provide
adequate flow and water levels in the canals, as well as allowing
recirculation for prevention of icing.

Stations were established in the area immediate to the past onshore and
present offshore discharge (Fig. 1). This transect was chosen to monitor fish
distribution in the area affected by the onshore discharge (Units 1 and 2) and
potentially affected by the offshore discharge (Units 1, 2 and 3)* Stations
I, J, L, N, 0, U and W (north transect) ranged in depth from 1 .5 m at station
I to 15 m at station W. Two 6-m stations were chosen at this north transect.
Station L (6m), located approximately 0.3 km south of the Unit 3 discharge,
and station U (6m), approximately O.3 km north of the discharge, were chosen
to aid in monitoring the projected thermal plume and its effect on pelagic
fish movement. Station U will be referred to as 6 m, north discharge
throughout the text. Station L will be referenced as 6 m, north, except when
referring to gill nets when for clarity it will be designated 6 m, south
discharge.

Additional stations were chosen at a sequence of depth contours
approximately 3.1 km south of the power plant in Lake Michigan (Fig. 1). This
reference transect was chosen for its position outside the influence of the
present and projected thermal plume and intake channel. Data from these
stations are invaluable in describing "normal" trends in fish distribution
occurring in Lake Michigan. Stations A - F (south transect) ranged in depth
from 1.5 m at station A to 15 m at station F, with intervening stations B, C,
D and E separated by ^-m depth intervals.

Of the three Lake Michigan beach stations established, one (station P -
Fig. 1) was positioned in the vicinity of the south open water transect
(approximately 3.I km south of the plant) as a reference station in the
shoreline area. The two additional stations in the vicinity of the former
onshore discharge canal (station Q, approximately 0.6 km south of the
discharge and station R, approximately 0.6 km north of the discharge - Fig. 1)
aid in monitoring the thermal plume and its effect on shoreline fish movement.

Throughout the study period slight changes in the sampling scheme were
initiated to improve the data set in response to changing needs. These
changes, along with those alterations in the scheme over the k yr imposed by
construction activities, are summarized in the METHODS section.

METHODS

INTRODUCTION

Adult and juvenile fish sampling scheme changes at the J. H. Campbell
Plant from 1977 to I98O (Table 1) reflect refinement of our study objectives
over the k yr to answer additional questions which arose after the initial
sampling years. As new information became available regarding placement and
configuration of the new offshore intake for Unit 3 and the combined discharge
structures for Units 1, 2 and 3» deletion of some stations, which provided
more peripheral information, and addition of other stations within the
possible zone of influence of the intake and discharge structures became
necessary. Throughout the k yr, sampling methods and the gear itself remained
constant and are described as follows.

SEINING

Seining was performed using a 0.6-cm (0.25 in) mesh nylon seine, 15.2 m x
1.8 m (50 ft X 6 ft) including a 1.8-m (6 ft) bag. The seine was hauled
parallel to shore for a distance of 6I m (200 ft). Duplicate non-overlapping
hauls were performed both day and night at all seining stations. Monthly
seining was performed from April through November (commencing in June 1977) at
three beach stations in Lake Michigan (Table 1, Fig. 1). Hauls were performed
against the current when possible. During times when waves and current did
not permit seining against the current, hauls were made in the direction of
the current. Over the k yr, sampling stations for seining remained constant.
Limnological and physical data (water temperature, secchi disc, wind and wave
height) were recorded each time a gear was fished (see Appendixes 2, 3 and k) .

GILLNETTING

Nylon experimental gill nets 36.6 m x 1.8 m (120 ft x 6 ft) were set once
a month for approximately 12 h during daylight and 12 h during the night from
April to November (commencing in June 1977) • Each gill net was composed of 12
panels, each 3 m long, starting with 1.3-cm (O.5 in) bar mesh and proceeding
in 0.6-cm (0.25 in) increments up to 7.6-cm (3 in) mesh, with the last panel
having 10.2-cm (4 in) mesh. Two of these nets fastened end to end were set
together and considered replicates. All gill nets were set parallel to shore.
During all k yr, bottom gill nets were set at the I.5-, 3-, 6-, 9- and 12-m
depth contours on the reference transect 3-1 km south of the plant (also
referred to as the south transect) and at the 6-m depth contour opposite the
former onshore discharge canal (Fig. 1). In 1978, this north station (L) was
shifted in its designation slightly to the south, but was still within the
influence of the thermal plume, while an additional 6-m north station (station
U-Fig. 1) was added north of station L in the event that the thermal plume
moved north after coming from the discharge. Station L in this report is
referred to as 6 m, south discharge and station U is referred to as 6 m, north
discharge. Bottom gillnetting at station U (6 m, north discharge) and station
N (9-m depth contour. Fig. 1) commenced in 1980 to better document any
attraction of fish to the intake and discharge area.

Table 1. Monthly sampling series for juvenile and adult fish at
selected stations in Lake Michigan near the J. H. Campbell Plant,
Port Sheldon, Michigan. Trawling at station B (3 m) was only
done during conditions of reduced wave height.

Maximum Beach Surface Bottom Bottom

Station Depth (m) Seining Gillnetting Gillnetting Trawling

A 1.5 1977-1980

B 3.0 1977-1980 1977-1980

C 6.0 1977-1980 1977-1980 1977-1980

D 9.0 Jun-Aug 1977 1977-1980 1977-1980

E 12.0 Jun-Aug 1977 1977-1980 1977-1980

F 15.0 1977-1980

G 18.0 1977 (Day only)

H 21.0 1977 (Day only)

L 6.0 1977-1980 1977-1980 1977-1980

U 6.0 1978-1980 1980

N 9.0 1980 1978-1980

P 1.5 1977-1980

Q 1.5 1977-1980

R 1.5 1977-1980

Surface gill nets, which are identical to bottom gill nets except for
additional floats, were set in all years at the 6-m depth contour at the
reference and north transects. In 1978 the previously described station
addition (station U, 6 m, north discharge) and modification of the existing 6-
m north transect station L were effected to increase surface gill net sampling
in the zone of influence of the thermal plume. Additional surface gillnetting
was performed at the 9- and 12-m south transect stations only from June to
August 1977-

TRAWLING

Bottom trawling was performed using the University of Michigan's R/V
Mysis, All trawl hauls were made at an average speed of 4.8 km/h (3 mph) .
Duplicate 10-min hauls were performed at the 6-, 9*". ^2- and 15"ni depth
contours on a transect 3«1 km south of the plant and at the 6-m depth contour
in the vicinity of the new discharge/intake structures at the Campbell Plant.
Trawling was performed each year once per month from April to December except
in 1977 when trawling commenced in June. In 1977 additional day trawl hauls
were performed from June to August at the l8- and 21-m depth contours at the
south reference transect. In 1978 a 9""' contour station (station N) was added
to the trawling scheme at the north transect to better document the attraction
of fish to the intake and discharge area. During all sampling periods,
1977-1980, the 3-m south reference station B was trawled only if diminished
wave heights occurred.

A semi-balloon, nylon otter trawl having a if.9-m (I6 ft) headrope and a
5.8-m (19 ft) footrope was used. The body and cod end of the net were
composed of 1.9""cm (0.75 in) and 1.6-cm (0.62 in) bar mesh respectively, while
the cod end inner liner was 0.63-cm (0.25 in) bar mesh. All trawl hauls were
taken parallel to shore following the station depth contour. Two replicate
samples were obtained at each station by once trawling south to north and once
trawling north to south.

MISSING ADULT AND JUVENILE FISH SAMPLES

While it was hoped that proposed fishing could be performed every month,
this was not always possible due to inclement weather, construction activity
in the area, or equipment failure. Within reasonable time constraints, effort
was made to reschedule sampling which was deleted because of inclement
weather. In addition a number of samples over the k yr were inadvertently
lost before they could be examined. In the case of lost samples, these were
carefully reconstructed using field record sheets which were filled out at
time of collection. Data from fish collected in the replicate sample could
often be used to reconstruct missing length, weight or sexual condition data.
Table 2 summarizes all samples of juvenile and adult fish which were missing
from our collections during 1977*1980.

FISH LARVAE TOWS

Fish larvae, arbitrarily defined as any fish less than 2.5^ cm total
length, were collected using a 0.5-n! diameter, nylon plankton net of no. 2
mesh (363-micron aperture). A Rigosha flowmeter (Rigosha and Co. Ltd., 10-4
Kajicho 1-Chome, Chiyoda-Ku, Tokyo, 101 Japan) attached to the center opening
of the plankton net was used to calculate volume of water sampled. When
flowmeters were not available or stopped functioning, average flowmeter values
were computed from readings available from the same stations at other times or
from stations of comparable depth. Suspect flowmeter readings were changed
when accuracy was questionable. All meter revolutions were converted to

Table 2. Summary of juvenile and adult fish samples missing from the proposed
monthly sampling series near the J. H. Campbell Power Plant, eastern Lake
Michigan 1977"1980. Number of missing observations in parentheses.

Year Samples Missing

1977 June - All night gill net sets (I6)

August - night surface gill nets at stations C (6 m, south
reference) and L (6 m, north discharge) (4)

October - All day and night gill nets (32)

1978 April - night trawls at station L (6 m, north discharge) (2)
day bottom gill net at station A* (I.5 m, south) (1)
day surface gill net at U (6 m» north discharge) (2)

June - night trawl at station N (9 m, north) (1)

July - day surface gill net at U* (6 m, north discharge) (1)
night surface gill net at L (6 m, south discharge) (1)

August - day trawl at station B (3 m, south) (1)

October - night trawl at station D* (9 m, south)

day seine at station P* (beach - south reference)

November - day bottom gill nets at stations B* (3 m, south) and E
(12 m, south) (2)

night surface gill nets at stations C, L and U (all 6 m
stations) (6)

1979 November - night surface gill net at station L* (6 m, south

discharge)

day and night bottom gill net at A (I.5 m, south) (4)

day trawl at station B (3 m, south) (2)

1980 July - night bottom gill net at U* (6 m, north discharge)

September - day and night trawl at B (3 m, south)

November - night bottom gill nets at A (I.5 m, south), B (3 m,
south) and D (9 m, south) (3)

^Samples reconstructed for purposes of analysis.

10

volume filtered using 1 revolution - 15 liters. Flowmeters were calibrated in
a swimming pool by walking a measured distance with a flowmeter attached to a
0.5-m diameter hoop without the net (see Jude et al. 1979b).

Duplicate surface tow samples were collected at the seining stations in
Lake Michigan (Fig. 1). Three people simultaneously hand-towed two nets for a
distance of approximately 6I m (200 ft) once during the day and once at night.
Beach tows were performed twice in June, July and August and once in April,
May and September during I978-I98O. In 1977» beach tows were performed twice
in June and July (three times at station R in July) and once in August,
September, October and November.

Horizontal 5-min fish larvae tows were also performed at discrete depths
parallel to shore at 13 stations in Lake Michigan (A, B, C, D, E, F, G, H, I,
J, L, N, 0) in 1977 (sampling at stations I, J, N and commenced in July
1977) and 12 stations (A, B, C, D, E, F, I, J, L, N, 0, W) from 1978 to I98O.
A summary of station depths and sampling strata is presented in Table 3*
Sampling was performed both day and night on the same schedule as beach tow
samples. Additionally, station L (6 m, south discharge) was sampled three
times in July 1977- The series of tows performed in mid-July 1977 at north
transect stations by Consumers Power personnel were made at slightly different
depth strata compared with our standard series tows.

Table 3- Fish larvae sampling depths (m) from selected stations in Lake
Michigan near the J. H. Campbell Plant, eastern Lake Michigan 1977"1980.

South transect
stations

G*

H*

North transect
stations

W#

Q, R

Tow depth (m)

0.5

0.5

0.5

0.5

0.5

0.5

0.5

0.5

2.5

2.0

2.5

3.0

^.5

4.0

5.0

k.O

^♦•5

6.0

8.5

9.0

10.0

5.5

6.5

9.0

11.5

14.0

15.0

8.5

11.0

lif.O

17.0

20.0

0.5

Max i mum
depth (m)

1.5 3.0 6.0 9.0

12.0

15.0 18.0 21.0

* Stations only sampled during 1977.

# Station added to sampling scheme in 1978-1980.

11

Larvae tows performed in Lake Michigan at depths of } m and less were
taken from 6-7"ni-]ong outboard motorboats. The University of Michigan's R/V
Mysis was used for tows at deeper stations. For each tow, the procedure was
similar and was as follows:

1) Plankton net with attached mason jar and depressor lowered to desired
depth (average ship speed: 3''6 km/h or 2-4 mph) .

2) Plankton net towed horizontally for 5 niin starting at the desired
depth which was obtained by measuring cable or rope angle and
tr igonometr ical ly calculating the amount of cable or rope to be
released to reach desired depth.

3) Plankton net hauled to surface and washed using a water hose from the
vessel used.

k) Contents rinsed into the wide-mouth glass (0.47 liter) Mason jar,
preserved (40 ml of buffered formaldehyde), labeled and sealed.

Total numbers of larvae captured in all tows (other than surface tows)
were adjusted to compensate for upper strata contamination. The adjustment
procedure is outlined in Fig. 3* The method consists of sequential
subtraction of numbers of larvae from the lower water depth levels based upon
densities observed in upper water strata. We assumed that larvae were
homogeneously distributed within a water stratum and that nets passing through
a particular stratum from a lower level would catch larvae in proportion to
the volume of water filtered. Larvae from all tows conducted below the
surface stratum, which were probably caught during the vertical haul following
termination of the horizontal tow, were removed via calculation from the final
total larvae density presented. We assumed that contamination occurring while
lowering the net was negligible. The effect of differential vertical
distribution due to larvae size was mitigated by stratifying larvae from each
sample into 0.5*nim length intervals. A total of 5^ length intervals were
defined for fish larvae.

Vertical net hauls, conducted in a 3«6"ni-deep swimming pool, were used to
estimate the volume of water filtered per meter of vertical tow. Mean volume
filtered was 0.48 m^ (28 ± 0.52 SE revolutions) yielding a correction factor
of 0.l8 m^ water filtered/meter of vertical haul. An example of this
adjustment procedure is presented in Table 4.

Length-frequency histograms were prepared for various combinations of the
larval fish data. Data were presented as a percentage of the total based on
densities. Thus, collection of two larvae of different sizes (n » 2) and
presentation of these data would not necessarily yield a histogram showing
50%: 50%.

SLED TOWS

Bottom tows were performed with a benthic fish larvae sled equipped with
a flowmeter (Yocum and Tesar I98O) (Fig. 4). A single 5""niin sled tow was
performed once during the day and once at night at all Lake Michigan stations
(except beach station R - north discharge) coincident with other fish larvae
tows when time and weather permitted. During 1977 only selected stations were
sampled, while consistent collection at all stations (except station R)

12

/

/

7

A

^\ /

STIUTA 1

/

*^

T,

/J

u

STMATA 2

/

V

/

v

STRATA 9

*1

^1

/'•/

STUATA 4

/

-4

\

/

» /

STRATA 9

/

s

\

/

CALCULATION PROCEDURE:

!• Convert current meter reading to voltime filtered (V^)

2. Stratify total larval (T^^) catch for each sample depth Interval Into n 0.5-mm length
Intervals, denoted by Nj^ ^*

n
Thus, T^ - E N4 _
^ ir-l ^*"

3. Calculate average concentration of larvae of length class m in the first stratum for
all m.

T»*"«» \,j!, - <Nl,m/^l> ^^^

4. Begin iterative calculation of adjusted average concentrations of larvae for each
depth stratum where

i-1 _
^lOOOftli^^ - trc (0.18(1 dj Z^^^IXmO^

c -i ' 3-1 '

^i,m \ ^ a if a >

i-1
Vi - 0.18 E d4
J-1 ^
. otherwise
where d^ • vertical depth of water in the i-th water stratum
D - total depth of water column 5

D - r di
i-1
T|^ « total uncorrected catch of larvae in the i-th water stratum.
N^ ^a » total uncorrected catch of larvae of the m-th size class caught in the
i-th water stratum.
Vj - estimates volume of water filtered by net towed in stratum i.
(0.18; » correction factor expressed in terms of volume of water filtered/meter of
vertical tow.
i.e.,

units « m^ 2

— ■ m
m

trc(*) ■ function which truncates argument to nearest non-negative integer number.
C|^^n ■ 3<JJusted average concentration of larvae of the m-th length class in the
j-th depth stratum.

Fig. 3. Schematic representation of adjustment calculations for upper
level contamination in larvae samples. Blocks represent varying quan-
tities of water filtered in five different water strata.

13

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15

commenced in 1978. Beginning in May 1979 beach station R (north discharge)
was also sampled with a benthic sled. All sled tows were performed from d-J-m
outboard motorboats.

MISSING LARVAL FISH AND EGG SAMPLES

During the study period, fish egg and larval fish sa^nples were
occasionally lost because of breakage, inadequate preservation, or inability
to collect them due to inclement weather. In the case of beach tows, the
replicate was used to estimate the density of larvae in the missing sample.
This could not be done for sled tows or larvae tows outside the beach zone.
The following is a list of samples which were missing from our standard series
due to one of the aforementioned reasons:

1977 22 September night net tows at stations G and H

1978 27 April at station W (4.5 m tow - day)

1 July at station C (4 m tow - night)

2 August at station N. (6.5 ^ tow - night)

14 August at station B (sled tow - night)

1979 15 May at station E (sled tow - night)

15 '^ay at station F (sled tow - night)
15 '^ay at station (6 m tow - day)

22 August at station A (sled tow - night)

1980 21 April at station A (0.5 m tow - day)

FISH EGG AND LARVAE PROCESSING

Fish eggs and larvae were removed from samples with the aid of a
dissecting binocular microscope. In late 1978 a staining technique using
Lignin Pink was employed for use with some of the samples difficult to pick
because of vast amounts of algae and/or detritus. This stain was used
sparingly, but did expedite larval extraction. Larvae samples were first
washed with tap water using a screened bucket. Dilute acid was then added and
the sample remained in the acid for 45 min. The acid was then rinsed from the
sample with tap water and the stain added. After at least 1 h of staining,
the sample was rinsed again with tap water and examined. Development and
refinement of this technique continued in 1979-

Once larvae were extracted from samples, they were measured to the
nearest 0.1 mm (total length), except when samples contained more than 20
larvae of any one species, at which time lengths were determined to the
nearest 0.5 ntm. Number, species and length of larvae as well as number of
eggs found were entered on coding forms and later keypunched to allow for
computer data processing. A computer program was developed to adjust numbers
of larvae and eggs to number per 1000 m^ of water filtered using flowmeter
readings. (See METHODS -FISH LARVAE TOWS for details).

16

Knowledge of fish populations and spawning times in southeastern Lake
Michigan, specimen comparisons with those stored in the Great Lakes Regional
Fish Larvae Collection (Dorr and Jude I98I) and the taxonomic works of Dorr et
al- (1976), Hogue et al. (1976), Lippson and Moran (197^) » Nelson and Cole
(1975) and Jude et al. (1979^) were used in larval fish identifications.

Problem areas exist in some species identifications of larval fish and
some identifications were tentative, particularly early in the study. Alewife
and gizzard shad could not easily be distinguished from one another from the
time of yolk-sac absorption until fin formation had taken place. Separation
of longnose and white suckers was also difficult. For a continued description
of these problematic areas, see species sections in RESULTS AND DISCUSSION.

Qual i ty Assurance

A quantitative evaluation of the effectiveness of our larval fish
processing procedures was conducted. To ensure that larval fish samples were
processed efficiently, a quality control program was initiated in 1979 and
continued in I98O. A random selection of about 10%, or 212 of the 2231 field
samples collected, was conducted and these samples were reprocessed.
Techniques were the same as those discussed in FISH EGG AND LARVAE PROCESSING.

Of 101 samples reprocessed in 1979» an average of 11.5% of the larvae in
these samples was missed. In I98O 11.1% of the larvae were missed in 111
samples reprocessed. The degree of difficulty in picking through the sample
(presence of algae, zooplankton and debris), as well as time of year and thus
size of larvae, obviously influenced the percentage of larval fish recovered
from samples during the second processing. Lake Michigan samples tended to be
filled with small crustaceans, algae and particles of debris. Larvae in these
samples were usually small and relatively transparent (e. g. alewife), which
made processing difficult. All larvae found during reprocessing were added to
the sample totals; no adjustments were made to samples not repicked in the
process.

LABORATORY ANALYSIS OF JUVENILE AND ADULT FISH

Each replicate from seine, gill net and trawl catches was labeled and
kept separately in plastic bags. Fish were processed fresh when time
permitted, or otherwise frozen at the Campbell Plant or on board the R/V Mysis
(trawl catches). For laboratory examination, fishes in each bag were thawed,
separated by species, then grouped into size classes. When large numbers of a
particular size class for an unusually abundant species were present, a
subsample was randomly selected from the group and the remaining fish weighed
(herein referred to as the mass weight) and discarded. The following data on
each fish from the subsample were recorded: total length (to the nearest
millimeter, caudal fin pinched), weight (to the nearest 0.1 g using a PIOOO
Mettler balance), sex, gonad condition, presence or absence of food in the
stomach, fin clips, lamprey scars and evidence of diseases and parasites.
Identification of food items in piscivorous fish were made when possible.
Large fish and fish in the mass weight (over 1000 g) were weighed with a
hanging scale spring balance (K023G Chatillon) to the nearest 20 g.

17

Gonad condition of adult fish was described according to five stages of
development: 1) slightly developed, 2) moderately developed - for female,
eggs discernible, but not fully ripe, 3) ripe, 4) ripe-running - sex products
exiting with application of moderate pressure, 5) spent. Other gonad
conditions recorded included: 6) immature, 7) unable to ascertain sex on
adult fish, 8) reabsorbed eggs - for female fish, 9) fish decomposed or
mutilated so that sex was impossible to determine.

All fish were identified to species using Hubbs and Lagler (1958),
Trautman (1957)* Scott and Grossman (1973) and Eddy (1957) with the exception
of the genus Goregonus (subgenus Leucichthys ) . Satisfactory keys for this
subgenus do not exist because of unsettled questions on the validity of
several species (Scott and Grossman 1973) and the possibility of their
introgression (Wells and McLain 1973)- The only adult Leucichthys that can be
positively identified is the lake herring, Goregonus artedi i . Other
Leucichthys , adult or juvenile, were pooled as unidentified Goregoninae (code
XG) . These were believed to be mostly bloaters, C. hoyi (see RESULTS AND
DISGUSSION, Unidentified Goregoninae ).

DATA PROGESSING AND GALGULATIONS

For each adult and juvenile fish examined, the following information was
recorded on a 75"Column coding form, one fish per line: date and time of
sample collection, type of gear, day or night series, station, species code, a
unique incrementing number, length, weight, sex, gonad condition and presence
or absence of food in the stomach.

Data on subsampled fish were recorded on consecutive lines each having a
subsampling code. Special columns were reserved for the corresponding mass
weight. Gomputer programs searched for subsampled lots and calculated number
of fish processed, their mean weight and the total number of mass-weighed fish
not examined. Mass-weighed fish were proportionally assigned to length
intervals based on the number of sampled fish found in each length interval.
Fish were divided visually by length into many narrow size classes when
originally subsampled to minimize error associated with this reconstruction of
sample length frequencies.

Data were keypunched, then read onto computer disks and tapes. For the
bulk of our statistical analyses, we used the Michigan Interactive Data
Analysis System (MIDAS) which was developed by the Statistical Laboratory of
the University of Michigan. From our computer programs, we obtained summary
statistics on seasonal gonad condition, temperature-catch relationships,
catches by month, gear type, station and day and night series and length-
frequency histograms. Most plots used in the report were drawn by the GALGOMP
plotter at the University of Michigan Gomputing Genter.

Gill nets were set for as close to 12 h as possible when there was
available daylight or darkness. Due to unpredictable weather conditions and
changing day length, however, actual time gill nets were fished varied from k
h 25 min to 15 h 25 min, except for sets in October 1980 when, due to inclement
weather, nets were in from 23 h 15 min to 2k h 10 min. Gill net catches for

18

calculating statistics were adjusted to approximate numbers caught per 12 h by
assuming that catch was a linear function of time. The above assumption is
not completely valid as gill net catch-per-uni t-t ime might be expected to
decrease as the net fills with fish, but increased accuracy could not justify
the cost of determining a precise relationship for each species.

DEFINITION OF TERMS

Adult fish length intervals - for figures describing total lengths of adult
fish, individuals were assigned to 10-mm intervals. For example, the 30"
mm length interval would include fish from 25 to 3^ nim. For length-
frequency histogram figures for most abundant species, size ranges for
adult, yearling and young-of-the-year were determined from length modes
of fish collected during each sampling period. Size ranges of each of
these groups may be slightly different for different months or years of
capture.

Beach zone - refers to that area of water, usually less than 1.5 m, that is
accessible to wading during seining and fish larvae sampling activities.
Includes only beach stations.

Fish larvae - any fish less than or equal to 25-^ mm in total length.

Fry - any fish greater than 25-^ nun in total length caught in plankton nets.
Fish were usually 25-5 to 100 mm.

Inshore - refers to that area of water between the shoreline and 21 m.

Larval fish length intervals - for figures describing total lengths of larval
fish, a specimen was assigned to a 0.5-nim interval based on total length.
For example, larvae 0.3 mm would be assigned to the interval 0.5 mm
(which includes all larvae 0.1 to 0.5 mm), 5.6-mm larvae would be
assigned to the interval 6 mm (which encompasses 5^6- to 6.0-mm larvae).

Mature fish - when used in figures, refers to fish which normally would spawn
during year of capture.

Nearshore - refers to that area of water less than or equal to 3 m and
includes stations P, A, B, Q, R, I and J.

Offshore - term for that area of water, not beach zone, 21 m deep or greater.
There are no stations in this zone. Same as deepwater.

Open water - refers to that area of water, which is not beach zone and

includes all stations 6 m to 21 m which were usually sampled by boat and

which had no aquatic macrophytes present. The area includes stations C,
D, E, F, G, H, L, N, 0, U and W.

Transition zone - area of water from 1 .5 to 3 m.

19

Zone of influence - that area of Lake Michigan aquatic habitat actually or

potentially affected by the presence of the intake and discharge

structures of Units 1 and 2 and Unit 3 and their associated withdrawal
and discharge of cooling water.

YOY - young-of-the-year - fish in their first year of life. They become
year 1 ings January 1 .

Water temperature intervals - catch of adult fish was assigned to 2 C water
temperature intervals for the purposes of establishing temperature-catch
relationships. For example, the 3 C temperature interval would include
fish caught between 2.0 and 3-9 C.

SCUBA OBSERVATIONS

A program of underwater observations has been conducted at the Campbell
Plant in Lake Michigan in varying degrees of intensity since 1977* The first
survey was performed by J. Dorr in 1977 to ensure the area of the proposed
Unit 3 intake and discharge pipeline was not an important spawning site.
Details of the study were presented in Jude et al . (1978), but will be briefly
restated for completeness.

During 9-10 August 1977» daylight underwater observations were made on
seven transects in the vicinity of the J. H. CampbelJ Plant using SCUBA. Two
transects (dives no. 1 and 3) were swum perpendicular to shore between the 6-
and 12-m depth contours (Fig. 5) • The first transect was offshore from the
discharge canal, the second was offshore from the jetties; each transect
covered a distance of approximately 1000 m. At the end of each transect a
continuing leg was swum perpendicular to the main transect for distances of
kOQ and 200 m respectively.

A third transect (dive no. 2) was swum at a reference location 3 km south
of the plant. This transect was perpendicular to shore, extending from the
10.5-m to 6-m contours, a distance of approximately 8OO m. A continuing leg
was swum south, parallel to shore along the 6-m contour, for a distance of 400
m. An additional three transects (dives no. 4-6) were swum parallel to shore
for a distance of 200 m along either the 9" or 12-m contours. One final
transect (dive no. 7) was swum 200 m north along the 12-m contour, then
shoreward to the 9-m contour, and then 200 m north along the 9-m contour.

In 1978 and 1979 SCUBA observations were confined to the intake canal.
During I98O a regular diving program was initiated in the area of the new
intake and discharge system in Lake Michigan, but because of construction
activity, was limited. Visual observations were conducted once per month,
July through October I98O at two specified locations, including two dives in
the area of the intake structures (one day, one night), and one day dive at
the reference area 3 km south of the plant. Substrates in the reference area
were typical of those found in the inshore areas of southeastern Lake Michigan
and were comprised of uniform-size, shifting sand presenting a smooth and
gently sloping surface profile. The intake station substrate consisted of

20

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— Dive no,1
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21

riprap (crushed limestone 0.1-2.5 m in diameter; 225""900 kg) deposited during
intake construction to reduce erosion of in-lake cooling water intake
structures.

The standard series dives were conducted using two or three divers
equipped with SCUBA. Divers always swam side by side and either 1 or 2 m
apart. Divers made observations at the intake station (southeast arm of
intake manifold) (Fig. 6) by swimming southwest along the west side of the
seven risers and back northeast along the east side of the risers
(approximately 50 m total). While swimming, each diver examined a plot of 2 m
in width. In addition the divers swam for 5 min, side by side on the sand
directly south of the southeast intake arm. Divers were 2 m apart during this
swim.

CAMPBELL PLANT UNIT 3
INTAKE MANIFOLD CONFIGURATION

0030
SCALE IN METERS

/

SOUTHEAST ARM

LAKE BOTTOM

l.UM DIA. RISER

2.4.M DIA.
HEADER PIPE

Fig. 6. Scheme of the J. H. Campbell Plant Unit 3 intake manifold
depicting site of SCUBA observations during 1979 and 1980. Inset shows
enlargement of an individual riser with two accompanying screens.

22

The previously described stations and observational methods comprise our
monthly standard series sampling effort. Due to construction activity in the
study area sampling did not begin until June. However, dives were undertaken
in May and June to select the best sites for standard series dives.

Observations were made following the format of Dorr and Miller (1975) and
were recorded underwater on water-resistant paper. Because of the uneven
nature of the riprap substrate at the Campbell Plant, abundance of cryptozoic
or demersal organisms was most likely underestimated. Large chunks of
limestone (approximately 2 m in diameter) rest on the bottom in such a manner
as to produce a vast number of small fissures and interstices which cannot be
examined and may contain demersal organisms.

STATISTICS

One objective of this study was to see how fish populations fluctuate
from year to year and to detect differences in fish abundances between the
reference area and the zone of influence (area of Lake Michigan affected by
the intake of cooling water and discharge of heated water). Catch-per-uni t-
effort (CPE) was utilized as an index of abundance, providing estimates of
relative population size. Note that CPE is an index of numerical abundance
and not an absolute measure of population size. Replicate samples were taken
using trawls, seines and gill nets. Each sample represented one unit of
effort. One unit of trawling effort was defined as a 10-min tow, one unit of
gill net effort was defined as one lift of one replicate of the net adjusted
to a standard 12-h fishing period and one unit of seining effort was defined
as a 6l-m sweep parallel to shore with the seine. There are many problems
equating units of effort of one gear type to effort units of another, so
abundance indices for different gear types are not directly comparable (Lawrie
and Rahrer 1973) • However, CPE values for different gear types may provide
complementary information about a particular fish population. For example,
individual fish which might avoid trawls might be captured by gill nets.
Conversely, fish which are too small to be captured in gill nets are likely to
be caught with seines and trawls. Assuming that biases of each gear are
constant over time and sampling stations, standardized units of effort for
each gear ensured that CPE was a reliable index for abundance for fish
populations (Ricker 1975)- Although the data were analyzed separately for
each gear type for a particular species, the aggregate of the results for all
gear types was reviewed for that species.

BMD8V was used to perform the analyses of variance (ANOVA) on the adult
and juvenile fish data (Statistical Research Laboratory 1975). Attained
significance values for ANOVA F-statistics were generated from TABLES, an
interactive computer program for statistical probability distributions (Fox
1978). The Michigan Interactive Data Analysis System (MIDAS - Fox and Guire
1973) was used for analyses of ANOVA residuals. Residuals, defined as the
difference between the cell mean and actual data value, were examined to
determine how well ANOVA model assumptions were met (Draper and Smith I966) .
A FORTRAN program was written to compute the LDTR (Least Detectable True
Ratios). MIDAS was used to perform the Wilcoxon signed ranks test on the
larvae data.

23

Design and Analysis Considerations

Statistical analyses were performed on catch data of the six most
abundant species of fish collected during field sampling in Lake Michigan.
They included: spottail shiner, alewife, rainbow smelt, yellow perch, trout-
perch and unidentified Coregoninae. Differences in fish abundance between the
reference area and the zone of influence were examined using analysis of
variance (ANOVA) . These analyses will hopefully provide information to
determine what impact the power plant may be having on fish populations. The
experimental designs were analyzed as completely crossed, factorial models
with YEAR, MONTH, AREA, DEPTH (for some designs) and TIME OF DAY as design
variables (Table 5)* All factors were considered fixed. The response
variable was either number of fish per unit of effort or a transform thereof.
We transformed raw data by taking log of the sum of CPE plus one. The
addition of one ensured inclusion of zero values of CPE in the transformed
data. This transformation was designed to reduce data variance so ANOVA
assumptions might be more closely met.

The factorial ANOVA designs were chosen according to species, gear type
and presence of zero values in data (Table 5)- The YEAR factor was examined
for each gear type to see if population abundances were significantly
different among the 3 yr. The MONTH factor was expected to explain a
considerable amount of variation attributable to seasonal changes in fish
abundance. The STATION factor was designed to test for differences between
the reference station C (6 m, south) and the zone of influence station L (6 m,
north) for trawl and gill net models, while for seining, this factor was
designed to test for differences between beach reference station P (1 m,
south) and treatment stations Q (south discharge) and R (north discharge).
AREA was used in the second trawl design to examine differences between the
reference area [stations C (6 m, south) and D (9 m, south)] and the zone of
influence [stations L (6 m, north) and N (9 m, north) ]• Depth was used in
this design to compare abundances between the 6- and g"'" contours. The data
for 6- and 9"ni stations were analyzed only for 1978-I98O because trawl samples
were not collected at station N (9 m, north) In 1977. TIME OF DAY was
employed in all of the designs. A main effect or an interaction was
considered significant if the attained significance (p) of its statistical
test was less than 0.01 (p < 0.01); the main effect or Interaction was
considered highly significant If the attained significance (p) for its test
was less than 0.001 (p < 0.001) .

Assumptions for the ANOVA model were: 1) residuals are normally
distributed, 2) variances of the population are constant for all partitions of
the population and 3) observations are statistically Independent. Balanced
factorial ANOVA are robust to the assumptions of normality and homogenous
variances. In other words, moderate departures from these assumptions do not
completely invalidate results of the model. Violation of the independence
assumption may have more serious consequences. Examination of frequency
histograms of residuals and plots of residuals versus cell means indicate that
the assumptions of normality and homogeneous variances were not seriously
violated.

24

Given that these assumptions are met, sensitivity of the ANOVA model to
detect the alternate hypothesis can be calculated. In this study, we were
interested in detecting significant differences between areas (or stations).
The least detectable true change (LDTC) is the minimum difference in mean
abundance between areas (or stations) that can be detected by our experimental
design. The formula we used for LDTC, as presented by Jude et al. (1979^), is
as fol lows :

6-s{2/n)^ (t^.v + 4(1-P),v)
Where: 6 = least detectable true change (LDTC)

s « within cell standard deviation of the ANOVA (i.e., the square root
of the mean square error)

n « number of observations in each of the two groups being compared

a a significance level

t = Student's t-statistic

V = degrees of freedom for the error sum of squares of the ANOVA

P » power (the probability that a true difference will be judged
significant by the ANOVA test)

Results for all ANOVA models were computed using both raw and log-
transformed data. Data for all species and gear types were initially screened
by calculating mean catch (which was equal in value to mean CPE since effort
for collecting any one sample was always one), its variance and percentage of
zero values in the design matrix. Summary statistics for those data sets
considered amenable to further statistical analyses (Table 6) showed that
percentage of zero catches for these data usually exceeded 25%. Consequently,
distribution of values was generally bimodal with modes at zero and near the
geometric means. The transformation did, however, yield residuals which were
slightly closer to meeting ANOVA assumptions than residuals from raw-data
values. Unless stated otherwise, future references to abundance when
discussing the ANOVA results will refer to geometric mean abundance derived
from log-transformed data. Geometric means for various partitions of the data
were derived by back transforming cell means from log^^Q-transf ormed data. For
example, if x represents the mean catch for log-transformed data, then x"= 10^
is the geometric mean catch. Use of log-transformed data can yield cell means
which are not in the same ranking order as cell means from the original data.
If so, the geometric means will also differ in ranking order since the
exponential function is monotonic.

When using log-transformed data, the LDTC or 6 is expressed as the change
in the logarithm of fish numbers and not in terms of the actual numbers of
fish. Back transforming 6 yields 10^; 10^ represents the ratio of the mean
number of fish per unit effort plus one for reference area RA to that of
experimental area PA (pi ant- i nf 1 uenced area). In the transformed coordinate

25

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charge)

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<u

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0) o
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pes >-3
CO CJ

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28

Table 6. Descriptive statistics for catch-per-uni t-of-ef f ort (CPE) data used
in the experimental designs for the six most abundant species caught in the
vicinity of the J. H. Campbell Plant, eastern Lake Michigan for years 1977
through J^980. N is number of observations included in the experimental
design; X is the mean number of fish caught per one unit of effort for the
data set.

Max i mum

Percentage of

catch

Standard

zero catch

Design

N

(no. fish)

X

deviation

data

TRAWL 1

Spottail shiner

22U

736

23.0

69.2

42.0

A 1 ew i f e

192

4287

100.4

407.8

23.4

Rainbow smelt

224

2268

118.8

286.5

8.9

Yel low perch

96

90

6.0

12.9

40.6

Trout-perch

192

144

9.9

19.4

47.9

Unidentified

Coregoninae

192

395

26.2

65.1

35.9

TRAWL 1 1

Spottai 1 shiner

384

736

27.^

76.6

35.2

Alewife

288

4287

122.9

434.5

29.5

Ra i nbow sme 1 1

384

2268

146.0

295.7

7.0

Yel low perch

144

195

6.5

19.5

43.8

Trout-perch

336

144

11.8

20.2

37.2

Unidentified

Coregoni nae

288

503

36.9

70.1

20.8

BOTTOM GILL NET 1

Spottail shiner

128

244

18.6

42.0

39.8

A 1 ew i f e

96

195

16.8

37.6

27.1

Yel low perch

96

34 ■

6.9

7.9

21.9

BOTTOM GILL NET II

Spottail shiner

144

244

24.2

43.8

33.3

Alewi fe

120

185

17.1

36.4

25.0

Yel low perch

48

3^

8.2

7.9

14.6

BOTTOM GILL NET III

Spottail shiner

96

244

19.8

43.5

27.1

Alewife

64

168

15.8

34.4

35.9

Yel low perch

48

3A

. 6.9

9.1

20.8

SURFACE GILL NET 1

Alewife

64

213

29.3

41.5

31.2

29

Table 6 continued.

Design

N

Maximum

catch
(no. fish)

X

Standard
deviation

Percentage of
zero catch
data

SURFACE GILL NET II
Alewife

SEINE

Spottail shiner

A 1 ew i f e

120

2i»0
190

213

1678
617^

22.7

68.7
225.0

36.8

20i».l»
697.^

38.3

22.5
27.1

system (i.e., log-transformed system) changes will be detectable if |5^ * %aI
> 6 where xg^and x p^ref er to the log-transformed mean catches at areas kA
and PA respectively. In the original coordinate system, differences are
detectable whenever:

RA

< 10

-5

or

RA

> 10'

PA

PA

We shall refer to the quantity 10^ as the least detectable true ratio (LDTR) .

Power Analysis

The LDTRs (Least Detectable True Ratios) are ratios involving geometric
mean number of fish. Least detectable true ratios for the designs employed
ranged from ] .2k to 2.97 with most occurring between 1.3 and 1.7 (for a « 0.01
and Power « 0.95) (Table 7)- The lowest LDTR (for a= 0.01 and Power « 0.95) t
1.2^4, was for the second trawl design for trout-perch; thus for this design
the mean abundance at one area should have to be at least 2k% greater than the
mean abundance at the other area to detect a difference in abundance between
areas. Overall the LDTRs of ANOVAs including just 1977 through 1979 data were
lower than those for ANOVAS including 1977 through I98O data. This was
probably due to increased variance in the data caused by difference in catch
distribution between I98O and previous years. LDTRs were highest for surface
gill net and seine designs. Among species, sensitivity of the ANOVA to detect
a significant difference between areas was lowest for alewife, which may be
related to alewife migration and highly variable recruitment of their young.
The trawl was probably the best gear for assessing impacts of plant operation;
in general, LDTRs were lower for trawl designs than for designs for other
gear. For all the trawl designs except the first trawl design for alewife,
the LDTRs were less than or equal to I.6I. Given that the assumptions of the
power analysis have been met for these trawl designs (same assumptions as for
ANOVA) • a 61% greater abundance at one station than at the other should be

30

(U

>%
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B
CO a

0)

u

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cd

0)

cd

c

0)

B

O4 a

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cd

0)
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cd
u
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0)
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Cd CO

rH <U

cd 0)

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N
0) -H
^ CO

0)

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>, CO -H -H

•H

X rj

O
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50»-4

cd x:

0) o
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0) CO

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dJ

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r* m -4

en en en

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en

r- ST.

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o> in

NO

en

00 -3-

en

m

en

en

NO

00 -^ vO

m m ^a^

^a- -• 00
m m CM

vn

CM

r^ ^ -.

CN <M PSI

«jr

en

en

en 0^

^ en

m

m

en

vO

m

CM m
m nt >3-

00 O 0^ —
00 00 vO vO

-^cMino — cMino ^iNino -♦c^iino — rsimo-^cMino -^cMino -^r^mo
000— 000— 000— • 000— ' OOO'-' 000-^ 000— • 000— '

z

1— 1

CJ

1— (

)—•

E-*

03

h-i

M

Cd

Id

Z! Z

Q

1

<

sc

-t

H

E-

flO CJ

Cd

r z

Ed

o -

33 CJ

X Z

o --
aa a

Cd Cd

CJ Z

<

o: H

=5 ^-

E-«
Cd Cd
CJ Z

^ H

CO CJ

Cd

Z

31

detected. The higher LDTRs for alewife are not a reflection of the
experimental design, but rather an indication of the naturally high variations
in abundance of alewives within the inshore zone.

Fish Larvae Analysis

The Wilcoxon signed ranks test was performed on fish larvae and fish egg
data to investigate differences in larvae and fish egg densities between the
reference (south) transect and the plant-i nf luenced or discharge (north)
transect. This statistical technique is the nonparametr ic analogue of the t-
test for paired observations (Conover 1971) • With a few exceptions, for each
tow performed at a particular depth contour and a particular stratum in the
water column at one transect there was a corresponding tow performed at the
same depth contour and stratum at the other transect for each sampling period.
Thus, during a particular diel period of larvae sampling, pairs of densities
could be calculated for all taxons of larvae found and this technique could be
used. To apply this procedure, both beach tow replicate samples were averaged
to yield one value for the 0.5-m depth in the beach zone. The four beach tows
[two at both stations Q (south of discharge) and R (north of discharge)] were
averaged to yield one value to be paired with the average value of the beach
tows at the south transect. The two beach sled tows at the north transect
(one at both stations Q and R) were averaged to pair with the beach sled tow
at the south transect. Any incomplete (one missing observation) pair of
observations negated calculation of the test statistic. All zero differences
or ties between pairs of observations were ignored. For most of the 1977
sampling year complete pairs of observations were available from the beach to
12 m; the 15-m depth contour was sampled for the south transect but not for
the north one.

The Wilcoxon signed ranks test was applied to data for each year
separately from 1977 to 198O for each of the more abundant taxons of larvae
collected as well as fish eggs. The. test was also conducted for all 4 yr of
data pooled for each of those taxons. A difference in densities between
transects was considered significant if the attained significance level for
the statistic was less than O.O5.

32

RESULTS AND DISCUSSION

TOTAL CATCH

The total catch of various species of fish in the vicinity of the
Campbell Plant is a relative index of abundance of fish populations in Lake
Michigan. When fish are collected consistently with the same gear, frequency
and effort, comparisons can be made among various areas and years. However, a
number of factors can affect total catch and should be considered when
discussing these data. Strong year classes and, conversely, weak ones have
dramatic effects on total catch as YOY always comprise the highest proportion
of our catches. Consequently their fluctuations usually explain most of the
variability seen in total catches. Timing, frequency and duration of
upwel lings (for example see Fig. 7) can also change the catch composition in a
given month by causing the usual warm-water species to be replaced by cold-
water species, such as lake trout, smelt and bloaters. Comparisons of catches
among years are thus drastically affected. Another cause of catch variation
is timing of gear deployment. Depending upon what time of the month our gear
are used we may or may not encounter migrations, spawning aggregations, or as
discussed, upwel lings. Lastly, there have been some minor changes in stations
fished over the 1977"1980 study period, but these were minor deletions and
additions which are not expected to affect total catch trends.

During 1977-1980, we collected k8 different species of juvenile and adult
fish in Lake Michigan near the J. H. Campbell Plant (Table 8). The list of
larval fish collected (Table 9) does not include any new species, but the
collection of lake trout larvae for the first time in southern Lake Michigan
since planted lake trout were introduced in the 1960s, is a notable entry (for
details see Jude et al. 198 lb and RESULTS AND D I SCUSS I ON— Lake Trout ). Among
these fish were 17 families, ranging from the ancient and threatened lake
sturgeon to the recently stocked array of salmonids, e.g., coho salmon,
Chinook salmon, brown trout and rainbow trout.

In the study area, the family with the most members was Salmonidae with
nine entries, followed by the Cyprinidae with eight and the Catostomidae with
six. Among fish caught are a number of marine species, including the
ubiquitous alewife, rainbow smelt and the recently introduced salmon.
Overall, the historical species complex in Lake Michigan has changed
drastically over recent history (see Smith 1968; Christie 197^)- The more
abundant and long-standing species in Lake Michigan, such as the lake herring,
members of the chub complex, lake trout, burbot and lake whitefish have been
overfished, preyed upon by sea lamprey, and have suffered destruction of
spawning habitat and nursery areas which have resulted in wholesale extinction
of some species and severe reductions in the abundance of others. Concurrent
with this upheaval in species interactions was the introduction of exotic
species like alewives and smelt, which are numerical dominants in our present
catches and undoubtedly in Lake Michigan in general. Certain species like
deepwater sculpins, which are abundant in the deeper regions of the lake, were
probably less affected by these changes than other endemic species. It is
against this backdrop of species interactions, fish stocking programs and the
continual eutroph i cat ion of Lake Michigan that we must evaluate the impact of

33

UJ

0) u

o

cd

-O

03 OJ

4J 4->

dJ CO

>

oj a

o

B o

1^
cn

O) 3dniVd3dlAI31 d3

0)

3 4J
03 C
CO CO

S a.

c
• o

o -H

00 JJ
ON CO

*-< j-i

ON fo

03
«3 T3
C -H

S^

<a d

Q) CO
3 O

CO
U
0)

a

6

S

4J CM

c

CO

o

CO

CO
•H

a

a

0)
CO

CO

H-3

•H
CO
Q

C
CO
&0

•H

a

J-i o

• 6 ^

^ O 03

•H Jul <u

pE4 M-i :^

IVM

34

o

LJ

a

>
o

o
o

Q.

O

ID
<

00

(J)

n3

c
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«>0

O) 3dniVd3d^31 d31VM

35

o

Ui

o

>
o

o
o

a.

UJ

en

<

o

CVJ

T3

o

00
•H

O) 3dniVd3dlAI3l d31VM

36

o

UJ
Q

>
O

z

u
o

c

0.
CO

<

X

z

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00
CD

<

q:

Q.

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<
2

m

LU

li.

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<

0)

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60
•H

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O) 3dniVd3d^M31 d31VM

37

Table 8. Family name, scientific name, common name and codes for all
species of juvenile and adult fish captured (from 1977 through 1980) in
Lake Michigan near the J. H. Campbell Plant. An X denotes presence in
a given year. Names assigned according to Robins et al . (I98O) .

Family, Scientific and Common Name

Code 1977 1978 1979 1980

Acipenser idae

Acipenser f ulvescens Raf inesque
Lake sturgeon

LG

Ather i nidae

Labidesthes sicculus (Cope)
Brook si Iverside

SV

Catostomidae

Carpiodes cypr i nus (Lesueur)

Qui 1 Iback
Catostomus catostomus (Forster)

Longnose sucker
Catostomus commersoni (Lacepede)

White sucker
Moxostoma ani surum (Raf inesque)

Si Iver redhorse
Moxostoma erythrurum (Raf inesque)

Golden redhorse
Moxostoma macrolepidotum (Lesueur)

Shorthead redhorse

QL

X

X

LS

X

X

X

X

WS

X

X

X

X

MA

X

X

X

X

GR

X

X

X

SR

X

X

X

X

Centrarchidae

Lepomi s cyanel lus Raf inesque

Green sunfish
Lepomis gibbosus (Linnaeus)

Pumpkinseed
Lepom i s macrochi rus Raf inesque

Bluegi 1 1
Micropterus dolomieui Lacepede

Smal Imouth bass
Pomox i s nigromaculatus (Lesueur)

Black crappie

GN

PS

X

BG

X

X

SB

X

BC

Clupeidae

Alosa pseudoharenqus (Wi 1 son)

A 1 ew i f e
Dorosoma cepedianum (Lesueur)

Gizzard shad

AL
GS

X
X

X
X

X
X

X
X

38

Table 8 continued.

Family, Scientific and Common Name

Code 1977 1978 1979 1980

Cottidae

Cottus bai rdi Girard MS X

Mottled sculpin
Cottus coqnatus Richardson SS X

SI imy scul pi n
Myoxocephalus thompsoni (Girard) FS

Deepwater sculpin

Cypr i nidae

Carass ius auratus (Linnaeus) GF

Goldfish
Cypr i nus carpio Linnaeus CP X

Common carp
Notemigonus crysoleucas (Mitchill) GL

Golden shiner
Notropis ather inoides Raf inesque ES X

Emerald shiner
Notropis hudsonius (Clinton) SP X

Spottai 1 shi ner
Pimephales notatus (Raf inesque) BM

Bluntnose minnow
Pimephales promelas Raf inesque PP

Fathead minnow
Rhinichthys cataractae (Valenciennes) LD X

Longnose dace

Esocidae

Esox lucius Linnaeus NP

Northern pike

Gadidae

Lota lota (Linnaeus) BR X

Burbot

Gasterosteidae

Pungi tius pungi tius (Linnaeus) NS X

Ninespine stickleback

I ctalur idae

i ctalurus natal i s (Lesueur) YB

Ye 1 low bul Ihead
I ctalurus punctatus (Raf inesque) CC X

Channel catfish

X X

X X

X

X
X

39

Table 8 continued,

Family, Scientific and Common Name Code 1977 1978 1979 1980

Osmer idae

Osmerus mordax (Mitchill) SM X X X X

Ra i nbow sme 1 1

Percidae JD X X X X

Etheostoma nigrum Raf inesque

Johnny darter
Perca flavescens (Mitchill) YP X X X X

Yel low perch
Stizostedion vitreum vitreum (Mitchill) WL X X

Wal leye

Percopsidae

Percopsi s omi scomaycus (Walbaum) TP X X X X

Trout-perch

Salmon idae

Coregonus artedi i Lesueur

Lake herring or Cisco
Coregonus clupeaformis (Mitchill)

Lake whi tef i sh
Coregonus hoy i

Bloater
Coregonus spp.

Unidentified Coregoninae
Oncorhynchus ki sutch (Walbaum)

Coho salmon
Oncorhynchus tshawytscha (Walbaum)

Chinook salmon
Prosopium cyl indraceum (Pallas)

Round whi tef i sh
Sal mo gai rdner i Richardson

Rainbow trout
Sal mo trutta Linnaeus

Brown trout
Salvel i nus namaycush (Walbaum)

Lake trout

Sciaenidae

Aplodi notus grunniens Raf inesque FD

Freshwater drum

Umbr idae

Umbra 1 imi (Kirtland) MM

Central mudminnow

LH

X

LW

X

X

X

X

BL

X

X

X

X

XC

X

X

X

X

CM

X

X

X

X

CH

X

X

X

X

RW

X

X

X

X

RT

X

X

X

X

BT

X

X

X

X

LT

X

X

X

X

ko

Table 9. Taxons and abbreviations for all groups of fish larvae
captured from 1977 through I98O in Lake Michigan near the J. H. Campbell
Plant. An L denotes presence of fish larvae and an F represents fry.
Names assigned according to Robins et al . (I98O) .

Scientific and Common Name Code 1977 1978 1979 1980

Catostomidae

1-+

Catostomidae spp.

XS

Unidentified Catostomidae

Carpi odes cyprinus (Lesueur)

QL

Qui 1 Iback

Centrarchidae

Lepomis qibbosus (Linnaeus)

PS

F

Pumpk i nseed

Lepomis macrochirus Raf i nesque

BG

F

Bluegill

Lepomis spp.

XL

L

Unidentified Lepomis

Pomoxis spp.

PM

L

Unidentified Pomoxis

Clupeidae

Alosa pseudoharengus (Wilson)

AL

L,

Alewife

Dorosoma cepedianum (Lesueur)

GS

L L
L L

L,F L,F L,F

L L

Gizzard shad

Cott idae

Cottus cognatus Richardson

SI imy sculpin
Myoxocephalus thompsoni (Girard)

Deepwater sculpin
Cottidae spp.

Unidentified Cottidae

Cypr inidae

Cypr inus carpio Linnaeus CP L L L L

Common carp
Notropi s ather i noides Raf i nesque ES L L L

Emerald shiner
Notropi s hudsonius (Clinton) SP L,F L,F L,F L,F

Spottai 1 shi ner
Pimephales promelas Raf i nesque PP F

Fathead minnow
Cyprinidae spp. XM L,F L L

Unidentified Cyprinidae

ss

L

F

L.F

L

FS

L

L

L

L

UC

L

itl

Table 9 continued.

JD

F

L.F

L.F

L.F

YP

L

L.F

L.F

L.F

LP

L

Scientific and Common Name Code 1977 I978 1979 I98O

Gadidae

Lota lota (Linnaeus) BR L L L

Burbot

Gasterosteidae

Pungi tius punqi tius (Linnaeus) NS L,F L L,F

Ninespine stickleback
Gasterosteidae spp. XG L

Unidentified stickleback

Osmeridae

Osmerus mordax (Mitchill) SM L,F L,F L,F L,F

Ra i nbow sme 1 1

Percidae

Etheostoma nigrum Raf inesque

Johnny darter
Perca flavescens (Mitchill)

Yel low perch
Perci na caprodes (Raf inesque)

Logperch

Percopsidae

Percopsis omiscomaycus (Walbaum) TP L L L,F L,F
Trout-perch

Salmonidae

Coregoninae spp. XC L L.F L,F

Unidentified Coregoninae
Oncorhynchus tshawytscha (Walbaum) CH F

Chinook salmon
Salvel inus namaycush (Walbaum) LT L,F

Lake trout

Larvae damaged beyond recognition XP L L L L
Unidentified Pisces XX L L

f Appeared as white sucker in Jude et al. 1979a.

the Campbell Plant. Any conclusions we make must take into consideration the
vastness of the Lake Michigan ecosystem, the present species complex in the
lake and the specific life histories of each fish and how that information
relates to the present intake and discharge system at the plant.

hi

Examining the total yearly catch of all fish caught by all gear in Lake
Michigan over the 1977"1980 preoperational period, showed an unexpected shift
in species dominance from alewife in 1977"1978 to rainbow smelt in 1979"1980
(Table 10). Alewives were 69% and 49% respectively of the total fish caught
in the first 2 yr, while they declined to 36%. then 19% in the latter 2 yr.
Though this implies a catastrophic decline in alewife abundance over the ^-yr
period, careful analysis (see RESULTS AND DISCUSSION, Alewife ) showed that
most variation was due to dramatic declines in alewife YOY numbers in the
catch. The adult component of the catch remained relatively stable over the k
yr. Pelagic pi ankt i vorous fish, like alewives, exhibit extreme fluctuations
in abundance and our findings are certainly not unexpected. In fact, alewife
populations in recent years may have finally reached a certain level of
stability since the 1960s when millions of dead fish littered Lake Michigan
beaches. Increased salmonid predation and commercial fishing may be mortality
vectors tending to keep populations in check. Our recent data (see RESULTS
AND DISCUSSION, Un i dent i f i ed Cor egon i nae ) show that bloaters, believed to be
suppressed by commercial fishing and alewife abundance, are now increasing in
numbers in Lake Michigan.

Rainbow smelt comprised I6, 28, 38 and kk% of the numbers of fish
collected during 1977 to I98O, respectively. Again, a strong year class was
produced in the latter 2 yr of our i*-yr study, causing these fish to be the
most abundant fish collected during 1979"1980. Most of the catch was
comprised of YOY and yearlings trawled during late summer and fall.

Spottail shiner catch appeared to be stable over the k yr, ranging from
7883 fish (10% of catch) in 1977» a year of incomplete fishing, to 15,273 fish
in 1980 (18%). June through September were months of maximum catch of
spottails. Spottails apparently are not as drastically affected by
fluctuations of other dominant species such as the alewife and smelt.
Spottails are usually separated temporally from smelt and spatially from
alewife. They are demersal species, feeding on benthos and epibenthic
zooplankton, organisms that are not the main food supply of alewives, which
feed in mid-water. Spottails are also nearshore, beach-zone fishes, which
keeps them spatially separated from rainbow smelt adults. Adult smelt inhabit
cooler water offshore, while YOY and yearlings are usually in deeper water
(6-12 m) than spottails.

Yellow perch, an important sport fish in the vicinity of the plant, was a
consistent part of our total catch, varying between 1 and 2% of the total
number of fish caught. Large year classes of perch apparently were produced
in 1977 (1254 fish) and I98O (1715 fish), resulting in high total catches
during these years because of the large YOY component in the catches. In I978
and 1979. lower catches (IO78 and 605 fish respectively) were observed.
Yellow perch were very responsive to water temperature, as was obvious from
the 1979 catch of 605 fish during a year of frequent upwel lings and cold
inshore temperatures (see RESULTS AND DISCUSSION, Yel low Perch for more
detail). Yellow perch were caught in highest numbers during August and
September, when YOY are recruited to fishing gear and yearlings are sometimes

43

Table 10. Summary of all fish species caught by all gear types during
June to December 1977 and April to December 1978-1980 in Lake Michigan
near the J. H. Campbell Plant, eastern Lake Michigan.

1977

MONTHS

y. OF

TOTAL

SPfCIES

JUN

JUL

AUG

SEP

OCT

NOV

DEC

SUM

ALEWIFE

2198

9890

13680

16314

9413

6409

93864

68.922

RAINBOW SMCLT

1065

994

7418

2706

393

70

732

12898

16.408

SPOTTAIL SHINER

999

1207

1444

4021

366

38

198

7883

10.028

YELLOW PERCH

92

147

448

463

7

43

94

1294

1.999

TROUT -PERCH

326

221

129

133

36

43

9

393

1. 136

UNIDENTIFIED COREGONtNAE

73

46

4

38

234

61

4

460

0.986

JOHNNY CARTER

116

13

17

73

68

1

298

0.379

WHITE SUCKER

3

91

191

34

4

1

294

0.374

LAKE TROUT

4

96

1

120

1

a

1

201

0.296

GIZZARD SHAD

3

14

90

13

94

174

0.221

NINESPINE STICKLEBACK

87

16

11

14

3

2

133

0. 169

COHO SALM3N

47

4

94

0.069

BROWN TROUT

11

6

3

19

4

49

0.062

SLIMY SCULPIN

12

9

3

1

23

44

0.096

LONGNOSE SUCKER

16

13

1

36

0.046

SILVER REOHORSE

6

2

1

12

0.019

LAKE WHITEFISH

8

2

11

0.013

RAINBOW TROUT

3

4

8

o.oto

ROUND WMTTEFISH

1

1

2

1

8

0.010

CtSWrnOH CARP

4

2

7

0.009

CHANNEL CATFISH

6

6

0.008

CHINOOK SALMON

1

1

2

4

0.009

SLUEGXLL

4

4

0.009

MOTTLED SCULPIN

4

4

0.009

LONGNOSE DACE

1

2

3

0.004

BROOK SXLVERSIDE

1

1

0.001

SHORTHEAO REDHORSE

1

1

0.001

EMERALD SHINCR

1

1

0.001

LAKE STURGEON

1

1

0.001

PUMPKINSEED

1

1

0.001

BURBOT

1

1

0.001

TOTALS

4606

8209

23349

24090

10908

6873

1021

78608

1978

MONTHS

% OF
TOTAL

SPECIES

APfl

MAY

JUN

JUL

AUG

SEP

OCT

NOV

DEC

SUM

ALEWIFE

21

880

966

3994

1983

1896

9309

26846

6

44617

49 . 038

RAINBOW SMCLT

1093

4046

2492

6692

6216

2279

1116

1083

391

29328

27 . 838

SPOTTAIL SHINER

26

429

3083

4222

3471

1049

249

142

109

12764

14.029

UNIDENTIFIED COREGONINIE

9

191

940

203

19

1666

479

18

3121

3.430

TROUT -PERCH

1 1

320

492

397

400

204

22

96

19

1841

2.023

YELLOW PERCH

8

3

8

142

302

939

28

19

29

1078

1. 189

NINESPINE STICKLEBACK

5

33

143

191

80

2

414

0.499

JOHNNY DARTER

29

48

36

89

96

62

36

6

362

0.398

WHITE SUCKER

39

29

78

78

79

9

1 1

319

0.391

SLIMY SCULPIN

61

129

13

32

9

1

34

279

0.307

LAKE TROUT

31

32

22

19

7

2

96

93

298

0.284

GIZZARD SHAD

1

69

98

19

18

32

189

0.208

BROWN TROUT

41

23

20

11

4

9

3

7

1 14

0. 129

LONGNOSE SUCKER

1

31

9

16

2

9

2

3

73

0.080

COHO SALMON

2

7

18

16

2

7

3

1

96

0.062

EMERALD SHINER

3

16

27

4

90

0.099

CHINOOK SALMON

4

1

13

7

3

1

29

0.032

BLUNTNOSE MINNOW

1

13

1

19

0.016

COMMON CARP

2

1

7

2

1

13

0.014

ROUND WHITEFISH

1

1

2

3

1

1

1

10

0.011

RAINBOW TROUT

2

2

1

4

9

0.010

LAKE WHITEFISH

4

1

2

1

1

9

0.010

WALLEYE

6

1

7

0.0O8

SILVER REDHORSE

4

4

0.004

0UILL8ACK

1

2

1

4

0.004

BURBOT

1

2

1

4

0.004

GOLDEN REDHORSE

1

3

4

0.004

CHANNEL CATFISH

1

2

3

0.003

BLUEGILL

1

1

2

0.0O2

NORTHERN PIKE

1

1

2

0.0O2

SMALLMOUTH BASS

1

1

2

0.002

SHORTHEAO REDHORSE

1

1

0.001

FATHEAD Ml?WOW

1

1

0.001

FRESHWATER DRUM

1

1

0.001

GOLDFISH

1

1

0.001

TOTALS

1313

6008

7116

19833

12952

6216

12977

28767

S02

90984

kk

Table 10. Continued.

1979

MONTHS

SPECIES

APR

MAY

JUN

JUL

AUG

SEP

OCT

NOV

DEC

SUM TOTAL

9AIN80W SMELT

305

3367

211

2108

17306

4275

599

1037

320

30028 38.400

ALE\rfIFE

449

1199

677

2703

1 193

4259

17846

164

28490 36.434

SPOTTAIL SHINER

31

1313

3442

1748

1315

417

783

219

206

9474

2. 116

UNIDENTIFIED COREGONINAE

3

309

2730

405

429

392

1431

9

5713

7 306

TROUT-PERCH

4

440

137

514

274

171

136

72

7

1755

2.244

YELLOW PERCH

12

13

36

103

103

1 1

40

200

505

0.774

WHITE SUCKER

47

42

113

42

158

7

4

413

0.528

JOHNNY CARTER

7

99

78

37

33

68

50

t7

16

405

0.518

NINESPINE STICKLEBACK

2

35

143

167

f

1

3

1

373

0.477

LAKE TROUT

9

13

13

22

13

27

37

37

1

222

0.284

LONGNOSE SUCKER

48

14

97

4

30

12

3

208

0.266

SLIMY SCULPIN

61

65

2

1

1

1

1

24

156

0. 199

8R0WN TROUT

27

16

13

9

4

12

3

2

38

0. 113

CHINOOK SALMON

4

21

16

1 1

2

10

1

2

57

q.086

ROUND WHITEFISH

2

4

4

2

6

19

6

t

44

0.056

GIZZARD SHAD

3

1

1

1

2

2

21

2

2

35

0.045

RAINBOW TROUT

17

1

3

6

29

0.037

LAKE WHITEFISH

9

12

1

5

27

0.035

CDHO SALMON

4

4

3

4

3

18

0.023

COMMON CARP

2

1

2

1-

2

2

10

0.013

GOLDEN REDHORSE

2

7

1

10

0.013

EMERALD SHINER

3

2

2

7

0.009

CHANNEL CATFISH

1

3

2

1

7

0.009

SHORTHEAO REDHORSE

2

1

1

4

0.005

BLUNTNOSE MINNOW

3

3

0.004

SILVER REDHORSE

1

2

3

0.004

MOTTLED SCULPIN

1

1

0.001

GREEN SUNFISH

1

1

0.001

LAKE STURGEON

1

1

0.001

TOTALS

493

5967

5674

8357

22219

6900

6403

20731

1453

78197

1980

MONTHS

SUM

SPECIES

APR

MAY

JUN

JUL

AUG

SEP

OCT

NOV

DEC

% OF
TOTAL

RAINBOW SMELT

2089

3327

3502

616

17865

3103

2978

1644

1573

36697

43 . 60 1

ALEWIFE

152

376

4142

1857

2042

3880

3291

198

59

15993

19.002

SPOTTAIL SHINER

35

569

3889

4667

577

3002

2175

236

127

15273

18. 146

UNIDENTIFIED COREGONINAE

2

741

3070

710

595

348

1387

687

394

3934

10.615

TROUT -PERCH

31

470

520

626

429

610

149

45

5

2885

3.428

YELLOW PERCH

25

15

42

230

513

787

36

12

5

1715

2.038

LAKE TROUT

19

54

28

10

61

211

125

1

506

0.601

WHITE SUCKER

42

58

36

92

120

30

14

392

0. 466

JOHNNY OARTER

22

80

37

21

16

54

29

20

34

313

0. 372

EMERALD SHINER

1

SO

107

31

28

247

0. 293

NINESPINE STICKLEBACK

4

98

too

24

9

1

236

0. 280

LONGNOSE SUCKER

8

35

21

10

18

34

26

14

166

0. 197

SLIMY SCULPIN
ROUND WHITEFISH

78

19

44

6

18

a

7

a

1
9

1

7

31

2
27

12
4

163
1 16

0. 194
0. 138

GIZZARD SHAD

2

1

22

51

6

25

4

1 1 1

0. 132

CHINOOK SALMON

3

3

59

3

3

21

1

1

99

0.118

CQHO SALMON
LAKE WHITEFISH

5
2

88

3

13

1
1

1
36

9
17

1

1
2

75
75

. 089

0.089

BROWN TROUT

RAINBOW TROUT

GOLDEN SHINER

COMMON CARP

SILVER REDHORSE

CHANNEL CATFISH

SHORTHEAO REDHORSE

BURBOT

MOTTLED SCULPIN

GOLDEN REDHORSE

LONGNOSE DACE

WALLEYE

CENTRAL MUOMINNOW

21
1

1

1

1
1

5

1

2

16

1
1

2

1

2

5

2

3

1

2
6
5
3

1

2
6

5
4
1

2

3

7
15
3

1

3
1

2

3

10

2

1
1

1

50

26

15
14

14
10
7
5
5
4
3
3
2

0.059
0.031
0.018
0.017
0.017
0.012
0.008
0.006
0.006
0.005
0.004
0.004
0.002

YELLOW BULLHEAD

2

2

0.002

OUILLBACK

1

1

2

0.002

OEEPWATER SCULPIN

2

o

2

0.0O2

SLACK CRAPPIE

1

0001

FRESHWATER DRUM

1

0.001

LAKE HERRING

1

0.001

NORTHERN PIKE

1

0.001

8LUEGILL

1

0.001

TOTALS

2517

5927

15533

3851

22371

12687

10489

3079

27 11

84165

U5

abundant inshore. The exception was 1979» when December trawls yielded 200
fish which was the highest monthly total catch during that year of cold water
temperatures.

Trout-perch were the fourth- or fifth-most abundant fish collected during
the ^-yr study (Table 10). Total catch varied from a high of 2885 fish in
1980 (3.4% of the total catch) to a low of 893 in 1977 (1.1% of the catch).
The low 1977 catch was probably due to reduced fishing during the early part
of the year when large catches were usually taken. Trout-perch have an
extended spawning season and seem to prefer moderately warm water » so they
were caught in large numbers over most of the spring and summer (May-August).
The largest catch of trout-perch, in I98O, was attributed to a year of good
survival for adults and yearlings, which were dominant age-groups in our
catches. In prior years their contribution to yearly total catch was
sporadic, with only one of the age-groups abundant.

The catch of fish in the subfamily Coregoninae ( Unidenti f ied
Coregoni nae ) . which are believed to be mostly bloaters, Coreqonus hoy i , rose
steadily from 460 fish in 1977 (1% of catch) to 893^ fish in I98O (11% of the
catch). This increase has been a lake-wide phenomenon and is attributed to
the banning of gill nets for commercial harvest of bloaters and a decline in
alewife abundance. The Coregoninae were the fourth- to sixth-most abundant
fish collected during our study years. The catch was generally comprised of
three groups of fish which varied in abundance over the study years. Most
were YOY in the 60-80-mm length range.

Among remaining species, lake trout was one that showed a large increase
in catch from 258 and 222 in 1978 and 1979 respectively to 507 in 198O. The
large increase in I98O may be a manifestation of the attraction of lake trout
to the newly laid riprap in the vicinity of the plant in fall 1979"1980.
However, no large differences in catch between reference (south) and plant
transects were found for I98O (see RESULTS AND DISCUSSION, Lake Trout ) .

Many other species were collected in lesser numbers, including some that
are known to be attracted to riprap or a thermal plume. When catches of
johnny darter and slimy sculpin (species which commonly inhabit riprap areas)
were examined, we found no increased catch over the k yr. Two other species,
carp and gizzard shad, are usually found in greater numbers around thermal
plumes. To date, however, no evidence of such an attraction was apparent in
our study area, but the offshore thermal plume during I98O was probably small
(Units 1 and 2 only) and intermittent. The catches in I98I should establish
whether significant attraction is occurring, since Unit 3 will be in
operation.

The lake sturgeon, a threatened species, is present in the plant vicinity
as two were collected, one in 1977 and one in 1978. Both were released. We
do not expect the plant will have any impact on this rare species.

The number of each species collected was separated by gear type (Tables
11» 12, 13» 14). The catch in each gear of all species pooled over years was
highest for trawls (68.2% - 226,260), followed by seines (21.2% - 70,396),

46

bottom gill nets (8.8% - 29,135) and surface gill nets (1.8% - 6163) . Trawls
were statistically the most effective gear for making comparisons, because
among gear, trawl catches exhibited the least variability. As could be
expected, surface gill nets were the least efficient gear, catching the fewest
fish overall. In 1977* seines caught the most fish, while for remaining years
trawls caught the greatest number. Examination of total catch by species and
gear within a given year showed that for 1977» alewives were the most
frequently seined fish (36,784). In 1978 spottail shiners were the dominant
fish (6873) in seines followed by alewives (2999). For both I979 and I98O,
alewives were the most frequently seined fish. Among fish caught in surface
gill nets, attesting to their habitation of surface waters at 6 and 9 ni,
alewives were by far the most frequently caught fish in all k yr. Alewives
are known to migrate to surface waters during the night. For bottom gill
nets, alewives (1977) and spottail shiners (1978-1980) were the most commonly
caught fish. Trawl catches reflected total catch trends. Alewives were most
frequently caught in 1977~1978, while rainbow smelt assumed dominance in trawl
hauls in the latter 2 yr. However, total catch is not the only criterion on
which we evaluate the use of four types of gear. Each type has its own
particular bias and strong points. For example, although surface gill nets
catch the least number of fish, it is the only gear which will fish directly
in the thermal plume, as most plumes float on surface waters. All our other
gear fish bottom waters.

In 1977 seined alewives (36,784) and trawled alewives and smelt (15,191
and 12,725 respectively) comprised the largest percentage of the total catch
(Tables 11-14). This pattern was not much different in 1978 when trawled
alewives and smelt (36,528 and 24,077) were the largest proportion of the
total catch and in I979 when trawls caught 23,127 alewives and 27,8l5 smelt.
In 1980, the number of major species comprising most of the total catch
increased, but all were collected primarily by trawls. They included: 35,238
smelt; 8834 spottails and 8043 unidentified Coregoninae. More detailed
discussion of catch differences and their significance will be presented in
the individual fish sections under RESULTS AND DISCUSSION.

The densities and distributions of larval fish species are discussed
under individual species accounts. To give a more general overview of
distribution of all larvae (all species combined) with depth, we calculated a
mean density for each station and sampling period, pooled over diel periods,
strata and replicates (in the case of beach tows) for each year 1977-1980
(Tables 15"l8) . These data should be useful for giving times and depths of
greatest occurrence of larval fish in the vicinity of the Campbell Plant.
Yearly variability of total larvae was high. In I98O, catches were highest,
with five incidences of densities over 10,000/1000 m^, very few catches of no
larvae and remaining catches in the 1000-2000/1000 m^ range. As noted
previously, 1980 was a warm year, with no major upwel lings occurring during
sampling periods, or for the larval fish season. Thus, warm years and
infrequent upwel lings are major physical factors controlling strength of
larval fish production in eastern Lake Michigan. During 1977-1979, larval
fish densities were in the 1000-2000/1000 m^ range, with few exceptionally
high catches.

47

Table 11. Summary of all fish species caught by seines during June to
November 1977 and April to November 1978-1980 in Lake Michigan near the
J. H. Campbell Plant, eastern Lake Michigan.

1977

MONTHS

% OF
TOTAL

SPECIES

JUN

JUL

AUG

SEP

OCT

NOV

SUM

ALEWIFE

1110

5077

11218

14880

2856

1643

36784

83.655

SPOTTAIL SHINER

435

1166

1298

3634

52

24

6609

15.030

YELLOW PERCH

31

14

285

2

332

0.755

RAINBOW SMELT

19

5

16

29

5

1

75

0. 171

GIZZARD SHAD

3

2

47

13

4

69

0. 157

COHO SALMON

47

47

0. 107

BROWN TROUT

9

1

10

0.023

UNIDENTIFIED COREGONINAE

7

7

0.016

TROUT-PERCH

4

2

6

0.014

COMMON CARP

4

1

5

0.011

BLUEGILL

4

4

0.009

RAINBOW TROUT

0^

1

3

4

0.009

SILVER REDHORSE

4

4

0.009

LONGNOSE DACE

1

2

3

0.007

LAKE TROUT

2

1

3

0.007

WHITE SUCKER

2

2

0.005

BROOK SILVERSIDE

1

0.002

JOHNNY DARTER

1

0.002

LAKE STURGEON

1

0.002

EMERALD SHINER

1

0.002

PUMPKINSEED

1

0.002

CHINOOK SALMON

1

0.002

NINESPINE STICKLEBACK

1

0.002

TOTALS

1626

6294

12551

18886

2937

1677

43971

1978

MONTHS

SUM

% OF
TOTAL

SPECIES

APR*

MAY

JUN

JUL

AUG

SEP

OCT

NOV

SPOTTAIL SHINER

11

146

1248

2495

2731

213

19

10

6873

62.957

ALEWIFE

3

9-

55

79

1258

1077

509

9

2999

27.471

RAINBOW SMELT

73

379

119

3

3

5

3

7

592

5.423

YELLOW PERCH

2

113

13

1

129

1 . 182

TROUT-PERCH

8

19

28

J3

15

5

78

0.714

WHITE SUCKER

4

1

39

13

57

0.522

EMERALD SHINER

3

16

27

4

50

0.458

COHO SALMON

5

17

14

36

0.330

CHINOOK SALMON

11

5

16

0. 147

Bi.UNTNOSE MINNOW

1

13

14

0. 128

BROWN TROUT

5

6

1

1

13

0. 1 19

NINESPINE STICKLEBACK

5

2

4

1 1

0. 101

LAKE TROUT

9

1

10

0.092

WALLEYE

6

6

0.055

GIZZARD SHAD

3

3

6

0.055

COMMON CARP

2

1

2

5

0.046

UNIDENTIFIED COREGONINAE

2

3

5

0.046

JOHNNY DARTER

2

2

4

0037

SLIMY SCULPIN

1

1

1

3

027

RAINBOW TROUT

2

1

3

0.027

LONGNOSE SUCKER

1

1

2

0.018

GOLDFISH

1

0.009

SMALLMOU-^H BASS

1

0.009
0.009
0.009
0009

fathead minnow
ouillback

BLUEGILL

1

Q

1

1

TOTALS

110

574

1494

2754

4062

1343

543

37

10917

A8

Table 11. Continued,

1979

MONTHS

% OF
TOTAL

SPECIES

APR

MAY

JUN

JUL

AUG

SEP

OCT

NOV

SUM

ALEWIFE

1

46

2155

160

220

5

2587

41 . 122

SPOTTAIL SHINER

13

171

364

1017

209

111

6

4

1895

30. 122

RAINBOW SMELT

4 .

1321

178

66

82

6

1

1658

26.355

TROUT-PERCH

3

44

1

1

49

0.779

CHINOOK SALMON

2

16

14

6

38

0.604

UNIDENTIFIED COREGONINAE

4

6

10

0. 159

GIZZARD SHAD

1

1

1

2

4

9

0. 143

BROWN TROUT

1

3

1

1

1

7

0.111

EMERALD SHINER

3

2

2

7

0.111

NINESPINE STICKLEBACK

2

3

1

6

0.095

RAINBOW TROUT

1

4

1

6

0.095

COHO SALMON

4

1

5

0.079

LONGNOSE SUCKER

1

4

5

0.079

YELLOW PERCH

1

1

2

4

0.064

BLUNTNOSE MINNOW

3

3

0.048

SLIMY SCULPIN

1

1

0.016

WHITE SUCKER

1

1

0.016

TOTALS

32

1561

389

1255

2433

362

248

11

6291

1980

MONTHS

% OF
TOTAL

SPECIES

APR

MAY

JUN

JUL

AUG

SEP

OCT

NOV

SUM

ALEWIFE

1

46

1336

283

1804

2663

127

6260

67.918

SPOTTAIL SHINER

3

182

17^

284

297

655

74

2

1670

18. 119

RAINBOW SMELT

2

330

91

48

96

6

4

577

6.260

UNIDENTIFIED COREGONINAE

16

236

252

2.734

EMERALD SHINER

1

80

107

3t

28

247

2.680

CHINOOK SALMON

2

52

1

55

0.597

COHO SALMON

54

54

0.586

YELLOW PERCH

7

6

20

33

0.358

GIZZARD SHAD

26

2

28

0.304

GOLDEN SHINER

15

15

0. 163

TROUT-PERCH

4

1

1

3

1

10

0. 108

WHITE SUCKER

2

2

1

5

0.054

NINESPINE STICKLEBACK

2

2

0.022

LONGNOSE DACE

2

2

0.022

LAKE WHITEFISH

1

0.011

JOHNNY DARTER

1

0.011

FRESHWATER DRUM

1

0.011

RAINBOW TROUT

1

0.011

BLACK CRAPPIE

1

0.011

BROWN TROUT

1

0.01 1

BLUEGILL

1

0.011

TOTALS

7

622

1673

572

2262

3765

280

36

9217

^9

Table 12. Summary of all fish species caught by surface gill nets
during June to November 1977 and April to November 1978-1980 in Lake
Michigan near the J, H. Campbell Plant, eastern Lake Michigan.

1977

■""

MONTHS

— —

—^

% OF

SPECIES

-JUN

JUL

AUG

SEP

OCT

NOV

SUM TOTAL

ALEWIFE

278

251

205

734 86.967

RAINBOW SMELT

1

34

35 4.147

LAKE TROUT

12

17

29 3.436

GIZZARD SHAO

19

19 2.251

BROWN TROUT

2

4

4

10 1.185

UNIDENTIFIED COREGONINAE

7

0'

7 0.829

WHITE SUCKER

1

2

3 0.355

CHINOOK SALMON

1

2

3 0.355

COHO SALMON

2

2 0.237

SPOTTAIL SHINER

1

1 0.118

LONGNOSE SUCKER

1

1 0.118

TOTALS

278

276

265

25

844

1978

MONTHS

% OF

SPECIES

APR

MAY

JUN

JUL

AUG

SEP

OCT

NOV

SUM

TOTAL

ALEWIFE

15

370

254

758

177

131

7

1712

83.026

SPOTTAIL SHINER

28

166

7

1

202

9.796

RAINBOW SMELT

5

66

2

1

1

2

77

3.734

LAKE TROUT

1

9

1

20

31

1.503

GIZZARD SHAD

12

3

1

16

0.776

COHO SALMON

1

1

1

3

1

7

0.339

BROWN TROUT

1

3

1

1

6

0.291

CHINOOK SALMON

3

1

1

5

0.242

CHANNEL CATFISH

1

1

2

0.097

WHITE SUCKER

1

1

0.048

LAKE WHITEFISH

1

1

0.048

TROUT-PERCH

1

1

0.048

LONGNOSE SUCKER

1

1

0.048

TOTALS

25

478

428

768

192

140

31

2062

1979

"~"

MONTHS

% OF
SUM TOTAL

SPECIES

-APR

MAY

JUN

JUL

AUG

SEP

OCT

NOV

ALEWIFE

X3

339

363

493

170

190

1555 86.197

RAINBOW SMELT

9

2

39

30

54

1

135 7.483

LAKE TROUT

1

2

2

2

14

6

27 1.497

BROWN TROUT

8

1

3

1

5

1

19 1 053

SPOTTAIL SHINER

1

3

2

12

18 0.998

RAINBOW TROUT

8

1

1

5

15 0.831

CHINOOK SALMON

2

3

1

4

1

11 0.610

UNIDENTIFIED COREGONINAE

7

7 0.388

COHO SALMON

2

1

2

5 0.277

TROUT-PERCH

5

5 0.277

YELLOW PERCH

.

5

5 0.277

WHITE SUCKER

2

2 0.111

TOTALS

10

361

371

549

204

278

18

13

1804

1980

■""

MONTHS

% OF
SUM TOTAL

SPECIES

APR

MAY

JUN

JUL

AUG

SEP

OCT

NOV

ALEWIFE

83

472

464

46

81

1

1147 78.940

RAINBOW SMELT

6

14

22

18

56

116 7.983

LAKE TROUT

2

60

10

72 4 955

SPOTTAIL SHINER

24

21

1

46 3. 166

YELLOW PERCH

16

16 1 . 101

RAINBOW TROUT

3

3

9

15 1 .032

CHINOOK SALMON

1

1

1

8

1

1

13 0.895

COHO SALMON

3

1

7

11 0.757

BROWN TROUT

3

1

2

6 413

UNIDENTIFIED COREGONINAE

4

1

5 0.344

CHANNEL CATFISH

2

2

4 0275

WHITE SUCKER

1

1 0.069

LONGNOSE SUCKER

1

1 . 069

TOTALS

9

99

504

488

106

160

64

_^

23

__

1453

50

Table 13. Summary of all fish species caught by bottom gill nets during
June to December 1977 and April to November 1978-1980 in Lake Michigan
near the J. H. Campbell Plant, eastern Lake Michigan.

1977

MONTHS

% OF

SPECIES

JUN

JUL

AUG

SEP

OCT

NOV

DEC

SUM

TOTAL

ALEWIFE

67 -

327

325

435

1

1155

35.517

YELLOW PERCH

58

111

368

146

1

37

721

22. 171

SPOTTAIL SHINER

26

40

144

349

31

590

18. 143

WHITE SUCKER

2

48

150

82

4

1

287

8.825

LAKE TROUT

2

42

1

101

18

164

5.043

GIZZARD SHAD

12

3

71

86

2.645

RAINBOW SMELT

3

7

53

63

1 .937

UNIDENTIFIED COREGONINAE

34

16

5

55

1 .691

LONGNOSE SUCKER

15

13

6

34

1 .046

TROUT-PERCH

2

8

3

21

34

1 .046

BROWN TROUT

2

3

3

11

10

29

0.892

SILVER REDHORSE

2

2

3

1

8

0.246

CHANNEL CATFISH

6

6

0. 185

ROUND WHITEFISH

1

3

2

6

0. 185

COHO SALMON

1

4

5

0. 154

RAINBOW TROUT

4

4

0. 123

LAKE WHITEFISH

1

1

2

0.062

COMMON CARP

2

2

0.062

SHORTHEAD REDHORSE

1

1

0.031

TOTALS

191

611

1042

1202

1

204

1

3252

1978

MONTHS

% OF

SPECIES

APR

MAY

JUN

JUL

AUG

SEP

OCT

NOV

SUM

TOTAL

SPOTTAIL SHINER

7

166

1454

1718

262

202

53

39

3901

42.601

ALEWIFE

3

488

114

2397

84

219

11

62

3378

36 . 890

RAINBOW SMELT

322

149

7

16

12

61

8

13

582

6.356

YELLOW PERCH

5

1

3

23

176

199

6

13

426

4.652

WHITE SUCKER

33

28

29

65

78

5

11

249

2.719

LAKE TROUT

30

23

18

10

5

2

67

52

207

2.261

GIZZARD 5HA0

1

53

45

7

18

124

1 .354

BROWN TROUT

36

16

16

9

4

4

3

7

95

1 .037

LONGNOSE SUCKER

1

29

9

16

1

7

2

3

68

0.743

TROUT-PERCH

3

1

2

9

6

24

45

0.491

COHO SALMON

1

2

1

2

4

2

1

13

0. 142

UNIDENTIFIED COREGONINAE

3

7

1

1 1

0. 120

JOHNNY DARTER

8

8

0.087

ROUND WHITEFISH

1

1

2

.

2

1

1

8

0.087

COMMON CARP

5

2

7

0.076

LAKE WHITEFISH

4

1

1

6

0.066

CHINOOK SALMON

1

1

1

2

1

6

0.066

RAINBOW TROUT

1

1

4

6

0.066

SILVER REDHORSE

4

4

0.044

GOLDEN REDHORSE

1

3

4

0.044

OUILLBACK

2

1

3

0.033

NORTHERN PIKE

1

1

2

0.022

SHORTHEAD REDHORSE

1

t

0.011

CHANNEL CATFISH

1

1

0.011

FRESHWATER DRUM

1

1

0.011

SMALLMOUTH BASS

-0

1

1

0.011

TOTALS

411

907

1655

4224

684

845

181

250

9157

5J

Table 13. Continued.

1979

MONTHS

% OF

SPECIES

APR

MAY

JUN

JUL

AUG

SEP

OCT

NOV

SUM

TOTAL

SPOTTAIL SHINER

17

397

679

664

401

217

220

75

2670

45 . 908

ALEWIFE

87

510

132

248

242

2

1221

20.994

RAINBOW SWELT

8

36

5

91

276

4

420

7.221

WHITE SUCKER

47

42

110

40

156

7

4

406

6.981

UNIDENTIFIED COREGONINAE

28

183

2

13

1

227

3,903

YELLOW PERCH

5

5

17

32

39

78

6

36

218

3.748

LONGNOSE SUCKER

47

12

93

3

29

11

3

198

3.404

LAKE TROUT

9

11

6

15

13

22

73

27

176

3.026

TROUT-PERCH

1

10

11

7

11

10

39

89

1.530

BROWN TROUT

26

8

8

5

2

7

4

60

1.032

ROUND WHITEFISH

2

3

4

6

17

5

37

0.636

LAKE WHITEFISH

9

8

3

20

0.344

CHINOOK SALMON

2

1

1

2

1

6

1

1

15

0.258

GIZZARD SHAD

2

1

2

9

1

15

0.258

GOLDEN REDHORSE

2

7

1

10

0. 172

COMMON CARP

2

1

1

2

1

7

0. 120

RAINBOW TROUT

7

7

0. 120

CHANNEL CATFISH

1

3

2

6

0. 103

COHO SALMON

2

3

5

0.086

SHORTHEAD REDHORSE

2

1

1

4

0.069

SILVER REDHORSE

1

2

3

0.052

SLIMY SCULPIN

1

1

0.017

LAKE STURGEON

1

1

0.017

TOTALS

84

654

1337

1258

843

1075

372

193

5816

1980

MONTHS

% OF
TOTAL

SPECIES

APR

MAY

JUN

JUL

AUG

SEP

OCT

NOV

SUM

SPOTTAIL SHINER

11

138

924

2147

208

1033

204

58

4723

43.291

ALEWIFE

5

50

1235

960

115

184

20

1

2570

23.556

YELLOW PERCH

8

5

13

172

266

335

7

8

814

7.461

RAINBOW SMELT

240

17

39

187

224

50

766

7.021

UNIDENTIFIED COREGONINAE

7

401

15

29

182

634

5.811

WHITE SUCKER

42

55

30

91

119

29

14

380

3.483

LAKE TROUT

15

7

15

5

61

150

1 15

368

3.373

TROUT-PERCH

2

16

10

10

8

29

67

18

160

1.467

LONGNOSE SUCKER

8

35

20

2

16

34

26

14

155

1 .421

ROUND WHITEFISH

10

3

5

4

2

27

26

77

0.706

GIZZARD SHAD

2

1

22

25

6

7

4

67

0.614

LAKE WHITEFISH

1

9

32

15

57

0.522

BROWN TROUT

21

4

13

1

3

42

0.385

CHINOOK SALMON

2

1

6

13

22

0.202

SILVER REDHORSE

1

2

6

5

14

0. 128

COMMON CARP

1

1

5

2

2

2

13

0. 119

RAINBOW TROUT

1

1

3

4

1

10

0.092

COHO SALMON

2

3

1

2

1

9

0.082

SHORTHEAD REDHORSE

2

3

1

1

7

0.064

CHANNEL CATFISH

1

3

2

6

0.055

GOLDEN REDHORSE

2

2

o

4

0.037

BURBOT

1

2

I

4

0.037

WALLEYE

2

1

3

0.027

YELLOW BULLHEAD

2

2

0.018

OUILLBACK

1

1

2

0.018

NORTHERN PIKE

1

1

0.009

TOTALS

331

327

2746"

3369

1008

2253

603

273

10910

52

Table 14. Summary of all fish species caught by trawls during June to
December 1977 and April to December 1978-1980 in Lake Michigan near the
J. H. Campbell Plant, eastern Lake Michigan.

1977

MONTHS

SPECIES

JUN

JUL

AUG

SEP

OCT

NOV

DEC

SUM

% OF
TOTAL

ALEWIFE

743

195

2137

794

6557

4765

15191

49.740

RAINBOW SMELT

1046

•545

7395

2590

348

69

732

12725

41 .665

TROUT-PERCH

322

219

119

130

36

22

5

853

2.793

SPOTTAIL SHINER

98

2

38

314

33

198

683

2.236

UNIDENTIFIED COREGONINAE

39

23

4

26

234

61

4

391

1.284

JOHNNY DARTER

116

13

17

73

68

9

1

297

0.972

YELLOW PERCH

34

5

66

32

6

4

54

201

0.658

NINESPINE STICKLEBACK

86

16

11

14

3

2

132

0.432

SLIMY SCULPIN

12

5

3

1

23

44

0. 144

LAKE WHITEFISH

8

1

9

0.026

LAKE TROUT

2

2

1

5

0.016

MOTTLED SCULPIN

4

4

0.013

ROUND WHITEFISH

1

1

2

0.007

WHITE SUCKER

1

1

2

0.007

BURBOT

1

1

0.003

LONGNOSE SUCKER

1

1

0.003

TOTALS

2511

1024

9752

3697

7570

4967

1020

30541

1978

MONTHS

% OF

SPECIES

APR

MAY

JUN

JUL

AUG

SEP

OCT

NOV

DEC

SUM

TOTAL

ALEWIFE

13

143

320

64

429

8778

26775

6

36528

53.056

RAINBOW SMELT

693

3458

2364

6633

6200

2212

1103

1063

351

24077

34.971

UNIDENTIFIED COREGONINAE

*5

189

537

196

16

1666

478

18

3105

4.510

SPOTTAIL SHINER

8

85

215

2

477

630

173

93

105

1788

2.597

TROUT-PERCH

3

297

423

354

383

195

16

27

19

1717

2.494

YELLOW PERCH

3

2

3

6

113

340

22

5

29

523

0.760

NINESPINE STICKLEBACK

31

139

151

80

2

403

0.585

JOHNNY DARTER

29

46

36

87

56

54

36

6

350

0.508

SLIMY SCULPIN

60

128

13

31

9

1

34

276

0.401

GIZZARD SHAD

7

4

32

43

0.062

WHITE SUCKER

1

10

1

12

0.017

LAKE TROUT

3

5

2

10

0.015

BURBOT

1

2

1

4

0.006

LONGNOSE SUCKER

1

1

2

0.0O3

ROUND WHITEFISH

1

1

2

0.003

CHINOOK SALMON

1

1

2

0.003

LAKE WHITEFISH

1

1

2

0.003

COMMON CARP

1

1

0.001

BLUNTNOSE MINNOW

1

1

0.001

BLUEGILL

1

1

0.001

WALLEYE

1

1

0.001

TOTALS

767

4049

3539

8087

7614

3888

11822

28480

602

68848

53

Table 14. Continued.

1979

MONTHS

% OF
TOTAL

SPECIES

APR

MAY

JUN

JUL

AUG

SEP

OCT

NOV

DEC

SUM

RAINBOW SMELT

293

2001

204

1891

17119

3863

588

1036

820

27815

43.268

ALEWIFE

23

325

6

130

601

4037

17841

164

23127

35.975

UNIDENTIFIED COREGONINAE

8

277

2540

403

410

392

1430

9

5469

8.507

SPOTTAIL SHINER

1

744

2396

67

703

77

557

140

206

4891

7.608

TROUT-PERCH

386

126

507

274

154

125

33

7

1612

2.508

JOHNNY DARTER

7

99

78

37

33

68

50

17

16

405

0.630

YELLOW PERCH

6

8

18

71

64

4

3

4

200

378

0.588

NINESPINE STICKLEBACK

52

143

166

1

1

3

1

367

0.571

SLIMY SCULPIN

59

65

2

1

1

1

1

24

154

0.240

LAKE TROUT

1

5

5

3

4

1

19

0.030

GIZZARD SHAD

8

1

2

1 1

0.017

ROUND WHITEFISH

1

2

2

1

1

7

0.011

LAKE WHITEFISH

4

1

2

7

0.011

LONGNOSE SUCKER

1

1

1

1

1

5

0.008

WHITE SUCKER

2

2

4

0.006

COMMON CARP

2

1

3

0.005

CHINOOK SALMON

2

1

3

0.005

COHO SALMON

3

3

0.005

BROWN TROUT

1

1

0003

RAINBOW TROUT

1

0.002

GREEN SUNFISH

1

0.002

MOTTLED SCULPIN

1

0.002

CHANNEL CATFISH

1

0.002

TOTALS

367

3391

3577

5295

18739

5185

5765

20514

1453

64286

1980

MONTHS

% OF
TOTAL

SPECIES

APR

MAY

JUN

JUL

AUG

SEP

OCT

NOV

DEC

SUM

RAINBOW SMELT

1841

2966

3350

616

17612

2727

2922

1631

1573

35238

56 . 304

SPOTTAIL SHINER

21

245

2792

2212

51

1313

1897

176

127

8834

14. 115

UNIDENTIFIED COREGONINAE

2

734

2649

695

565

430

1387

687

894

8043

12.851

ALEWIFE

146

197

1099

150

77

952

3144

196

55

6016

9.613

TROUT-PERCH

29

450

509

616

421

580

79

26

5

2715

4.338

YELLOW PERCH

17

10

29

58

224

446

59

4

5

852

1 .361

JOHNNY DARTER

22

80

37

21

16

53

29

20

34

312

0.499

NINESPINE STICKLEBACK

4

96

100

24

9

1

234

0.374

SLIMY SCULPIN

78

44

18

7

1

1

2

12

163

0.260

LAKE TROUT

1

47

11

5

1

1

66

0. 105

ROUND WHITEFISH

6

3

3

8

5

5

4

1

4

39

0.062

LAKE WHITEFISH

1

3

3

1

4

2

1

2

17

0.027

GIZZARD SHAD

16

16

0.026

LONGNOSE SUCKER

1

8

1

10

0.016

CHINOOK SALMON

1

6

1

1

9

0.014

WHITE SUCKER

1

4

1

6

0.010

MOTTLED SCULPIN

1

1

1

1

1

5

0.008

DEEPWATER SCULPIN

2

2

0.003

CENTRAL MUDMINNOW

2

2

0.003

LONGNOSE DACE

1

0.002

BURBOT

1

0.002

LAKE HERRING

1

0.002

COHO SALMON

1

0.002

COMMON CARP

1

0.002

BROWN TROUT

1

0.002

TOTALS

2170

4879

10610

4422,

18995

6509

9542

2747

2711

62585

5A

Larvae were most abundant during July and August of all years. In 1977»
July was the peak month, while in 1979. August had highest catches. In I978
and 1980, both July and August were months of maximum abundance. High
densities of larvae were also recorded in June; densities were much higher
than September levels, but lower than July and August collections.

The depth distribution of total larvae was in general inversely related
to depth. A clear pattern of decreased densities with increasing depth was
shown for peak larval abundance months in 1978 and 1979- In 1979. densities
at beach to 3-m stations were high (some over 10,000/1000 m^) , while all
densities at 6- to 15-m stations averaged less than 1000/1000 m^. In 1978, a
similar pattern was evident, but the densities at intermediate depths (3 to 9
m) were considerably higher with many values in the 2000/1000 m^ range. At 12
and 15 m, average densities were mostly less than 500/1000 m^. Trends in 1977
and 1980 were not as clear as the pattern established for 1978-1979* although
the major deviation from the pattern was the occurrence of high average
densities at intermediate depths. This occurred for two dates in I98O at 6
and 9 m and at one date in 1977 at 12 m. Other than these sporadic
occurrences of high densities at intermediate-depth stations, a similar trend
of decreasing densities the deeper the station was observed.

MOST ABUNDANT SPECIES

Alewi fe

I ntroduction —

Over the k yr, the relative abundance of alewives has decreased from
68.5% of the total fish catch in 1977 to 19% of the total fish catch in I98O.
Although there is an apparent precipitous decline over the k yr, a closer
examination of the data reveals a more stable condition in adult populations.
The total adult catches not adjusted for changes in sampling design were
approximately 365O, 4858, 318O, and 4190 in 1977-1980 respectively. Year-to-
year fluctuations in total catch (all age-groups combined) were primarily
caused by extreme variability in catch of YOY and yearlings. Additionally,
the increased catches of smelt and unidentified Coregoninae from 1977 to I98O
were the primary causes for the decreased percentage of alewives in our
samples.

Adult alewives are generally most abundant in the area of the Campbell
Plant in June and July, corresponding to times of intense spawning. It is
likely that most spawning occurs at depths of 9 ni or less. A major spawning
peak in late June was indicated in all h yr resulting in highest densities of
larval alewives in early July. The first occurrence of larvae in any year was
related to the warming trend of Lake Michigan and occurred when water had
warmed to approximately 12-15 C. Throughout June to August in any year cold-
water upwel lings caused temporary cessations in spawning which again ensued
when the upwel ling dissipated. YOY alewives along with yearlings and adults
move offshore in autumn to depths outside our study area.

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59

Larvae —

Our i+-yr studies documented that alewife was the most abundant species of
larval fish present in the study area. Alewife larvae were most abundant from
June to August, which might be expected from their reported May to August
spawning time (Jude et al. 1979a» I98O) . Previous studies (Jude et al,
1979a» 1980) suggest that larval alewives exhibit a "passive" stage during
which little substantial horizontal determinate movement takes place, and
during which larvae are carried passively by water currents. Since it is not
known at which stage larval alewives begin to exhibit substantial directed
horizontal movement in response to environmental factors, nor is it known at
what critical current speeds this directed movement is possible, the extent to
which ambient water currents determine the distribution of the larval
population sampled is difficult to assess. It is possible that the net
horizontal movement of larval alewives may be in the same direction as the
prevailing water currents until the time of fin formation, as was found for
mackerel (Sette 19^3)' In consideration of this possibility a study of their
distribution requires an understanding of study area water currents.

The nearshore area is perhaps the most dynamic zone in Lake Michigan, and
it is in this zone (a strip of approximately 10 km) that the main transfer of
energy from the wind to the total basin takes place (Mortimer 1975) • The
current patterns in this nearshore area are extremely complex, being subject
to a number of factors. Prominent among these factors are bottom topography
and wind stress. The predominant currents in the area are shore-parallel, but
under certain conditions the alongshore pattern is altered. One such
aberration occurs when waves arrive at right angles to the beach which causes
offshore rip currents (Bowen and Inman 1969)* In addition to those currents
produced more immediately by wind, there are a number of additional whole-
basin internal waves which result from more prolonged wind stress; these also
affect nearshore current patterns. These whole-basin wave motions are
reviewed by Mortimer (1975) •

One particular circulation pattern in Lake Michigan which has dramatic
effects on the distribution and abundance of not only larval, but juvenile and
adult fish, is the phenomenon of upwelling. Upwel lings occur along the
eastern shore of Lake Michigan with a north wind and along the western shore
with a south wind (Mortimer 1975) • Currents produced by these winds are
deflected offshore by the Coriolis force resulting in the warmed surface water
moving offshore and the cold hypolimnetic water moving shoreward and upward to
replace it. Upwel lings, on specific dates, can be the major driving force
forging the distribution and abundance of larval alewives. This effect is
examined in detail in the following text. Speculations regarding the time
that particular groups of larvae hatched relative to our sampling periods are
based on a mean hatching length of 3*8 mm and an average growth rate of 0.62
mm per day derived for Lake Huron stocks (Heinrich 198l) .

60

Seasonal di str ibution —

April and May — Over the k-yr period larval alewives were rarely
encountered in Lake Michigan during April or May. The single larva caught in
April 1978 was attributed to a late hatched larva from 1977- The only other
occurrence was in May 1979 when very low (less than 65 larvae/1000 m^)
densities of alewife larvae were observed at one station in Lake Michigan
which was evidence of only limited spawning at this time. Additional evidence
for limited spawning and hatching of alewives in Lake Michigan during May is
also given by Wells (1973f ^97^) who found a few larval alewives in Lake
Michigan near Saugatuck (25 km south of Port Sheldon) during late May 1972 and
1973* A few alewife larvae were also collected near Bridgman (IO8 km south of
Port Sheldon) on 1 June 1974 (Jude et al. 1979b) further indicating limited
spawning in May by alewives. Since the aforementioned study areas are all
adjacent to a river system, it is also possible that early alewife spawning
may have been occurring in the rivers resulting in some larvae being carried
passively into Lake Michigan.

Early June — The occurrence of a major alewife hatch in early June of any
year appears to be directly related to water temperature (Figs. 8-20).
Threinen (1958) reported that alewives initiate spawning at water temperatures
of 12.0-15-5 C. Water temperatures exceeding 15 C during early June 1978
evidently triggered substantial alewife spawning and hatching (Figs. 11-13)-
Mean densities of larval alewives at this time were highest at the beach to 3-
m stations (Fig. 11) and exhibited substantial declines at the 6- to 15-ni
stations (Figs. 12-13). With the additional exception of early June 1979,
when north transect beach and 3"") station water temperatures resulted in
minimal alewife spawning and hatching (Fig. 14), mean densities exceeding 20
larvae/1000 m* were not observed in early June of other years.

It is probable that alewife spawning near Port Sheldon is generally
minimal during early June unless inshore water warms to temperatures exceeding
12 C. Substantial late May-early June spawning and hatching occurred in only
one (1978) of the k yr of the study.

Late June — The occurrence of larval alewives in late June was variable
over the k yr. During 1977 and I978 only limited hatching had occurred in
late June as no mean densities exceeding kO alewife larvae/ 1000 m^ were
observed (Figs. 8-I3). During 1979 and 198O, mean densities of alewife larvae
ranged from 73 to 100 larvae/1000 m^ indicating a higher level of hatching
activity compared with late June of 1977 and 1978 (Figs. 14-19). As during
early June of all years, larvae captured in late June were primarily newly
hatched (Figs. 8-I9) -

These data collectively indicate that spawning activity in the area of
Port Sheldon is limited during the first half of June. Substantial spawning
activity during early to mid-June would have resulted in higher larval alewife
densities in the latter part of June of each year.

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1977

3000--

vf>,.^'^''^^,,V-'\„,.>*;^,,.,'•

NORTH TRANSECT

SAMPLING PERIOD

4000 ■-

^21

SOUTH TRANSECT

SAMPLING PERIOD

Fig, 20. Mean density (no./lOOO m ) of larval alewives for north
and south transect stations in Lake Michigan near the J. H. Campbell
Plant, 1977 to 1980. Mean densities were calculated by averaging
densities over all gear (plankton nets and sleds) , strata and diel
periods (day and night) sampled. O = no sampling performed.

74

1978

NORTH TRANSECT

SAMPLING PERIOD

^^_^- ^' ^-^^^- '^' ^'

^15

SAMPLING PERIOD

.>'<' ..^^^'

SOUTH TRANSECT

Fig. 20. Continued.

75

1979

5295

I

3000-

o

D
C
— 20C0--

<
>

<

'000--

^^^' .c^^^' .^^^^ .0.^^^

SAMPLING PERIOD

NORTH TRANSECT

3000-

o
o

O2000-

uJ

<

>

<

1000--

SAMPLING PERIOD

SOUTH TRANSECT

Fig. 20. Continued.

76

1980

4000

fo 3000

o
o

o

^2000

>

<

,v>^' ,vi^— ^— ^— ^— ^-— ^

NORTH TRANSECT

\^'

SAMPLING PERIOD

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>

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6684

i

500

I

'"■■F^ll^ ^

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SOUTH TRANSECT

SAMPLING PERIOD

Fig. 20. Continued.

77

Early July — For all years studied, the first sampling period in July
marked the first major occurrence of larval alewives near Port Sheldon
(Figs. 8-19). With the exception of early July 1979» mean densities at the
beach to 3 n^ and 6- and 9"ni stations ranged from 1000 to over 6OOO iarvae/1000
m^. During early July 1979* a cold-water upwelling depressed water
temperatures below those conducive to alewife spawning, and thus mean
densities at the beach to 3*ffi stations did not exceed 66O larvae/ 1000 m^, and
no mean densities exceeding 70 larvae/1000 m^ were observed at the 6- to 9"""^
and 12- to 15""^ stations.

There are at least three possible mechanisms by which cold-water
upwel lings could affect the abundance of alewife larvae in the study area.
The first is the effect of cold-water upwelling on adults expected to spawn in
the area. Our studies indicate that many adult alewives move from the
nearshore zone affected by an upwelling (see RESULTS AND DISCUSSION, Alewife .
Adults, Seasonal distribution ) . This movement from the area by the spawning
stock, as well as the retarding effect cold water would have on the spawning
stock that remained in the area, would dramatically affect egg deposition and
hence recruitment of newly hatched larvae. Newly hatched individuals
comprised the majority of larvae in our early July samples in all years.
Another effect a cold-water upwelling may have on recruitment of newly hatched
larvae is direct mortality or decreased survival of alewife eggs deposited
just prior to the upwelling. Edsall (1970) observed that the development of a
functional jaw in larval alewives did not occur at water temperatures less
than 10 C. Water temperatures below 10 C are frequently observed during
upwel lings. The third mechanism by which upwel lings could affect abundance of
alewife larvae in the study area is by transporting newly hatched passive
larvae offshore with surface currents. The fate of larvae transported from
the nearshore zone to the offshore zone is uncertain. Since the alewife has
adapted to spawn in the nearshore zone, it is probably most advantageous for
larvae to use the nearshore zone as a nursery. Thus factors which would
distribute the larvae offshore probably negatively affect their survival. It
is likely that the aforementioned mechanisms exert differential effects on the
abundance of larval alewives which are dependent on the extent of the
upwel 1 ing.

There was a general tendency over the 4-yr study for larval alewives to
be more concentrated at depths of 9 "» or less. This tendency was more
pronounced during times of upwelling when nearshore stations had relatively
higher water temperatures.

Early July sampling during 1977"1980 confirmed that the first substantial
alewife spawning activity usually took place in late June to early July.
There is also a clear indication that upwel lings have a depressing effect on
spawning and hatching.

During 1977 when the Units 1 and 2 discharge canal opened at the
shoreline of Lake Michigan substantial spawning occurred in the discharge
canal during early June. Early July 1977 length-frequency histograms from the
north and south transects beach to 9"^" stations were compared (Figs. 8-10).
They showed that a considerably higher proportion of larvae captured at the

78

north transect stations exceeded 10 mm total length when compared with the
south transect catch. We believe that early spawning in the onshore warm-
water discharge in Lake Michigan was responsible for the observed differences.

Late July — The effect of cold-water upwelling was most clearly observed
during late July sampling. For 1977-1979. deflections in the warming trends
(Figs. 8-16) in late July indicated an upwelling either during sampling or
just prior to it. The result of the upwel lings during late July 1977 and 1978
was reduced mean densities at all station groupings, compared with earlier
July densities of these same years (Figs. 8-13). Since an upwelling was
present during both July 1979 sampling periods, low mean larval alewife
densities were observed for that entire month (Figs. 14-16). Presence of
upwel lings generally resulted in a more nearshore distribution of larvae, as
can be seen in late July 1977 and 1979 (Figs. 8-19), which is probably related
to increased spawning and hatching in warmer nearshore water. During late
July 1978 sampling, the effect of an upwelling, which occurred just prior to
our collections, was diminishing and a more general distribution of larvae to
15 m occurred (Figs. 11-13)-

There was a striking difference between late July sampling in 1977-1979
and 1980. During the I98O period, no interruption in the summer warming trend
of the inshore zone was observed, and the intensive spawning and hatching
activity, observed in early July, continued. Mean densities at nearshore
(beach to 3 m) stations in late July I98O were clearly higher than offshore
stations, exceeding 4000 larvae/1000 m^ (Figs. 17-19)*

Thus it appears that if a warming trend continues uninterrupted
throughout July in the inshore zone, intensive hatching, resulting in mean
densities often exceeding 2000 larvae/1000 m^, might be expected to depths of
15 m. If a warming trend is interrupted by an upwelling, a diminishing effect
on spawning and hatching might be expected, resulting in mean densities well
below 2000 larvae/1000 m^. The extent of this attenuating effect of
upwel lings on larval alewife abundance is dependent on upwelling intensity and
duration.

Early August — Resumption of a summer warming trend in early August 1978
and 1979 resulted in substantially higher mean densities of larval alewives
compared with late July in these years (Figs. II-I6). Continued warming of
inshore water during early August I98O resulted in mean densities of alewife
larvae which were comparable to levels in early August 1978 and 1979
(Figs. 17-19); however, these mean densities were much lower than densities
measured during late July I98O. Lower densities of alewife larvae in early
August 1980 compared with late July I98O suggest a tapering off of an alewife
spawning peak which occurred in early to mid-July. Thus it appears that the
upwelling temporarily delayed spawning and hatching. A resumption of the
inshore summer warming trend resulted in increased spawning and hatching.
During years when there were no significant upwel lings and the warming trend
proceeded uninterrupted, a more defined spawning peak would be expected in
July, and a tapering off of the peak would be expected in August, as was
observed in I98O.

79

Distribution of larval alewives for all 3 yr in which early August
samples were taken (1978-1980) showed similar trends. Highest mean densities
were at beach and 3"ni stations, with successive declines at 6- to 9""''^ and
12- to 15"ni stations. It is this distributional trend which is most common,
except when the major hatching peak occurs, which can occur in June-August.
During those peak hatching periods the distribution of larval alewife was more
widespread out to depths of 15 m.

Examination of early August length-frequency data comparing north with
south transects over the 3 y revealed few differences. During early August
1978, a substantially higher proportion of larvae captured within the
nearshore zone (beach and 3 ni) at the north transect exceeded 10 mm while
those within the similar south transect area were less than 10 mm
(Figs. 11-13). A reverse of this trend was observed during early August 1979
and 1980 (Figs. 14-19); thus we feel that length-frequency differences
observed between transects at these times were attributable to natural
variability rather than plant effects.

Late August — During most years sampled, hatching tapered off in late
August. This decline was most evident during I98O when, as previously noted,
the lack of substantial upwel lings resulted in a more defined hatching peak in
July. Mean densities at any of the station combinations during late August
1980 did not exceed 55 larvae/1000 m^, while late August sampling during 1977
and 1978 showed consistently higher mean densities (60-5^1 larvae/1000 m^)
(Figs. 8-19)- During late August 1979» even higher densities (up to 2150
larvae/1000 m^) were observed. These data support the contention that
upwel lings cause an apportioning of spawning over a longer period of time,
resulting in less defined peaks in abundance. Duration of major spawning
effort is determined by duration of the upwel lings. During 1979 when there
was an extended upwel ling through July, there was still substantial spawning
occurring in late August. During 1978 and 1979f upwel lings were present only
in mid- and late July, resulting in substantial spawning into early August.
For these 2 years through early July the primary spawning peak was dictated by
physical factors.

During all study years there was a general tendency in late August for
larvae to be more concentrated at depths of 9 m or less when compared with 12-
and 15-m stations (Figs. 8-19). Length-frequency data indicated that during
most years a substantial portion of the larvae captured in late August were
hatched within 2 wk or less prior to sampling (Figs. 8-19)-

September — With initiation of cooling in Lake Michigan in September,
alewife spawning generally ceases. Substantial decreases in mean larval
alewife densities were observed in September of all years when compared with
late August (Figs. 8-I9) . These decreased densities of larval alewives in
September reflect the lack of recruitment of newly hatched larvae as well as
net avoidance by larger larvae which would be expected at this time.

Length-frequency histograms from September 1979 stand out from those of
the other years (Figs. Ii+-l6) . During 1977» 1978 and I98O all alewife larvae
captured in September were 15 nim or longer (Figs. 8-19)- In September 1979*

80

in excess of 50% of the larvae captured were less than 15 mm, indicating that
they probably were spawned and hatched in early September. This abnormal
extension of spawning in September 1979 was probably due to the extensive
upwelling which occurred in July 1979* The effect this delayed spawning has
on survival of larvae hatched so late in the growing season is unknown. We
believe these larvae experience higher winter mortality than larvae hatched
earlier in the season.

Young-of-the-Year —

As larval alewives grow during summer months, they become increasingly
susceptible to capture by seines and trawls. It is at this point of
susceptibility that we refer to them as young-of-the-year (YOY) . YOY are an
extremely important age-group of fish since they have survived the period of
highest mortality. Since it is assumed that this age-group would have the
highest probability of impingement on the 9'5"'nim wedge-wire intake screens, a
documentation of their preoperational distribution relative to the intakes was
essent i al •

Seasona I d t s tr i but i on — Generally, the first substantial catch of YOY
alewives in any year occurred in August (Fig. 21). The exception to this
trend was observed in July 1977 when over 5000 YOY were captured in seine
hauls at beach stations in Lake Michigan (Fig. 21). Although this might
appear to indicate that spawning had occurred earlier in Lake Michigan during
this year, larval fish data from Lake Michigan stations do not support this
hypothesis (see RESULTS AND DISCUSSION, Alewife . Larvae,
Seasona I d i s tr i but i on ) . The most notable correlation which could explain the
early occurrence of YOY alewives in Lake Michigan in 1977 was found by
examining larval fish data from adjacent Pigeon Lake for 1977"1979 (Jude et
al. 1978, 1979a, 1980). Over the 3-yr study period, the most intensive early
June spawning of alewives was observed in 1977 when densities of alewife
larvae were high (near 2000 larvae/1000 m^) at two of the three beach sampling
stations in Pigeon Lake. It was thus strongly indicated that Pigeon Lake was
used as an early June spawning area by many adult alewives. It is possible
that these larvae used the area of Pigeon Lake as a nursery area and moved out
into Lake Michigan in July in 1977* Another possible origin of the YOY caught
in July 1977 may have been the discharge canal which in that year opened
unobstructed at the shoreline of Lake Michigan. We believe that early June
spawning took place there by either early inshore migrating alewives from Lake
Michigan or a resident population of alewives from the canal itself. During
early June 1978 and 1979 no larval alewives were reported at beach stations in
Pigeon Lake (Jude et al. 1979a, I98O) indicating that during these years very
little early June alewife spawning occurred there. In contrast to July 1977,
only one YOY was caught at adjacent Lake Michigan beach stations during July
1979 and none were caught in July 1978.

Although July data suggest that YOY alewives remain in the nearshore
zone, larval fish data (see RESULTS AND DISCUSSION, Alewife , Larvae,
Seasonal di str i but ion ) indicate that some larvae which have overlapping size
ranges (15"25 mm) with those classified as YOY, were distributed to the 15-m
depth contour in July of all years.

81

I-YL

-- AO

lo-3n l6-9r

NORTH TRANSECT
977

]xlO*-
1x10'-
1x10'-
1x10'

1x10* =r

1x10'

5 1x10'

S 1x10' —

o 1x10* =r
o

w 1x10' —

^ 1x10'-
iZ

1x10' -

^ 1x10*"

i 1x10'-

2

I 1x10'

1x10'

1x10* =r

1x10' —
1x10' —
1x10'

1x10* =r

1x10' —
1x10' —
1x10'

YOY

YOY'

AD

., I I,

— YOY

•YL

AD'

YOY'

YOY

JUN

JUL

AUG

SEP

OCT

NOV

DEC

20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320
TOTAL LENGTH (MM)

Fig. 21. Length-frequency histograms for alewives collected during June
December 1977 and April - December 1978-1980 at north and south transects.
Stations were combined into two groups for the north transect: beach and
3 m; 6 and 9 m and into three groups for the south transect: beach, 1.5
and 3 m; 6 and 9 m; and 12 and 15 m. Diel periods and gear types were
pooled. YOY = Young-of-the-year; YL = Yearling; AD = Adult.

82

IxlQ'-
\xlO'-
^xlC -

]xlO*-
IxIC'-

1x10' -
1x10* =
1x10'-

^ 1x10'-

< 1x10' -
u

Q 1x10* =

O 1x10'-

^yi

AO

lQ-3n l6-9n ii2-i5n
SOUTH TRANSECT
1977

l-YOY

X
CO

1x10' —
1x10'

5 1x10*-

(T 1x10'-
UJ

2 1x10'-

D

^ 1x10' -

1x10*-
1x10'-
1x10'-
txIO' -
1x10*-
1x10'-
1x10'-
1x10' -

YL

AD-

^

.YOY,

Ij.. .

.YOY

YL

AD-

i: I

• YOY

-H*^

n 1 r

JUN

JUL

RUG

SEP

-1 r' 1 1 1 1 1

OCT

n 1 1

NOV

20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320
TOTAL LENGTH (MM)

Fig. 21. Continued.

DEC

83

1x10'
1x10'
1x10'
1x10'

1x10*
IxiO'
1x10'
1x10'
Ix iG*

S 1x10'
< 1x10'

O 1x10*

2 1x10'

CO

il 1x10'

fc 1x10'
O

ec 1x10*

LU

g 1x10'
S 1x10'
1x10'
1x10*
1x10'
1x10'
1x10'

1x10*
1x10'
1x10'

1x10'

1x10*
1x10'
1x10'
1x10'

■A^— * lo-sn ie-an

NORTH TRANSECT
1978

-I 1 r

•YL

4^

-AD

-I 1 T

JU-UL

'YL

' r " I r

AD

r-^-V 1 ^

— YL —

,,! I! li ■! J ■■ ,.

■AD

YOY

YL

A0<

T — 1 — ■ T

— YOY

YL

AO

I I I I I . I i
M .i n I! I .. .! .......

T — '^— T — ' — r — ' — 1 1-

YOY I

MoH

^-^-i^

YOY ^

"T r I I I I T"

JY0Y<

I I

-i 1 r

-1 1 ! ! 1 r

RPR

n 1 1 1 1

nflY

JUN

JUL

,. ■ ,. ■! ,. I! l! ■! ij .! RUG

I I I I I I I 1 I I I I

SEP

-i 1 1 1

OCT

NOV

DEC

20 40 60 80 ^20 120 140 160 180 200 220 240 260 280 300 320
TOTAL LENGTH (MM)

Fig. 21. Continuea.

84

AO -^ |o-3n ie-sn Ii2-i5n
SOUTH TRANSECT
1978

20 40 60 80 100 120 140 160 180 200 220 240 260
TOTAL LENGTH (MM)

Fig- 21,

^^outmuea.

RPR

nflY

JUN

JUL

AUG

SEP

OCT

NOV

300 320

85

lo-3n l6-9n

NORTH TRANSECT

1979

PPR

MRY

JUN

JUL

flUG

SEP

OCT

NOV

20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320
TOTAL L E NGTH (MM)

lEC

Fig, 21. Continued.

86

.X lU -

IxiO^-

•,x1Q' -

MU* -

1x10' -

1x10^

1x10'

1x10'

1x10^

1x10^

:x'0'

1x10*

1x10'

UJ

-J
<

CO

1x10'
1x10'

S

o

-1

1x10*
1x10'

lG-3n \6-3r. ]\2-:sn
SOUTH TRANSECT
1979

YL

li I,

AD

|i * !. !■

». ■■ ■

YL

AD

" M » — H-

Ji-^

1x10*'
1x10'

x10*=r

o: 1x10'-

UJ

i 1x10*-

^ 1x10' -
^ 1x10* =
1x10'-
1x10*-
1x10' -
1x10*-
1x10'-
1x10*-
1x10' -

1x10*
1x10'-
1x10*-
ix10' ■

J— YOY

^ YL

— AD

YOY

YL

i: ,i: I I

i: ,i

•YOY.

-ii-l-YOY^

YOY

20

Fig.

— T — "

40

21

flPR

nflY

JUN

JUL

AUG

SEP

OCT

NOV

DEC

60 80 100 120 140 160 ^80 200 220 240 260 280 300 320
TOTAL LENGTH (MM)

Continued.

87

H>

AO-

lc-3n {6-9n

NORTH TRANSECT
1980

X .0

"x lu* — r
IxlC'-f

ixiO' — L

YL

AD

YL

-i — '■' — r — — r — ' — r

AD

I 1

-r

! I!

-r-- — I-

ix:c'-

1x10'-

<

a

,yiC'

CO

2

ixin*

-J

ixiir

X

IxlQ*

w

u.

1x10'

^-YOY-

CD

1x10* -
IxiQ'-

ixlG'-

iC ~r

'YL

AO -

-T 1 T"

YL-

AD

-T r" — — r r

YOY

YL

AO

1x10*-
1x10'-
1x10'-
1x10' -

n — "^n — ■ — r — " — r
I YOY .

T — ' — r — ■ — r — --T

|ftD|

1x10* =p V r — •— T 1 1 1 r-

1,103^ l-YOYH

1x10'

IxlO'

•AO-

IxiO* =1= ^ r — "-V

1x10' 4- I— YOY-^

IxiC-
1x10'

~i 1 1 f 1 f-

flPR

MAY

n 1 1 1

JUN

n — ■ — I 1 1 1

JUL

n 1 1 1 1

AUG

-T 1 1 1

SEP

~i I 1 1 1 1 1

OCT

NOV

20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320

TOTAL LENGTH (MM)

Fig. 21. Continued.

88

DEC

<
u

CO

o
O

o

a:

Ui
00

:x;0'
:xiO'

1x10'
1x10^
1x10*
1x10^
1x10'
IxlC
biC*
1x10'
1x10'
1x10'

1x10*
1x10'
. 1x10'
1x10'
1x10*
1x10'
1x10'
1x10'

1x10*
IxiO'
1x10'
1x10' ■

'xlO*-
1x10'-
1x10'-
1x10' -
1x10* =
1x10'-
IxiC-
'xlO' -

hYL

AD

.j: l!^ Il

lG-3n l6-9n :i2-'5n

SOUTH TRANSECT
1980

YL

tA-

AD

I Ij I I- I j II

' YL

AO

AO

h-YOY-

AO

Id

YOY

YL<

I- I- I

jiLk.

YOY

Kii

^-^YOY.

-AO-

hvoYH

_, —
20

-^

flPR

nflY

1

-f

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1
1

i

H-

i:
1-
i:

i:
i:

!•

1^

;Li_i_i|_L^

i

1
1

1
1

I

1

1.

1

1
1
1 t

''• 't ' 'l ^ 1 1 ,

JUN

JUL

ALfG

SEP

OCT

NOV

Fig,

40 60 80 100 120 140
TOTAL

21. Continued.

DEC

IBO 180 200 220 240 260 280 300 320
LENGTH (MM)

89

During August of all years, there was a definite tendency for YOY to be
distributed in the nearshore beach zone (Fig. 21). Without exception at least
99% of YOY captured in August from 1977 to I98O were seined at beach stations.
Modal length of YOY alewives caught in August each year ranged from kO mm in
1977 to 30 mm in I978-I98O. The slightly higher modal length of YOY caught in
August 1977 may substantiate the contention that some of these YOY were
spawned early in Pigeon Lake or the discharge canal and moved into the
adjacent Lake Michigan beach zone. It is also possible that this slight
difference in modes was caused by variation in growth rates between years. A
close examination of I978 length-frequency data for YOY captured in August
also revealed that although modal length was 30 mm, nearly as many fish were
in the 40-mm length interval.

During September YOY alewives were primarily distributed from the beach
to 3-m depths (Fig. 21). The most marked nearshore distribution of YOY in
September was observed in 1977 when 99% of the YOY captured were taken at
beach and 3-m stations. During September 1977 there were also 10 times as
many YOY captured (over 15,000) than in September of any other year. The
reason for this extraordinary occurrence of YOY nearshore in September 1977
may be related to water temperature differences between stations. During
September of other study years, 1 978-1980, water temperatures at 6- and 9-m
stations were not significantly different from beach and 3-m stations
(Fig. 22), which apparently allowed for a wider distribution of YOY to the
6- and 9-m contour. During September of these years 7*33% of the YOY catch
was taken at 6- and 9"»n depths. During 1977» however, nearshore bottom
temperatures were substantially higher than bottom temperatures at 6- and 9-m
stations (Fig. 22), resulting in a concentration of YOY in the nearshore zone.
The contention that YOY alewives were attracted to warmer water temperatures
is substantiated by the observed correlation of highest YOY alewife catch at
beach station Q (south discharge) in September 1977 when this station
exhibited highest water temperatures available (15-5 C) among Lake Michigan
beach stations. Brandt (I98O) reported that YOY alewives near Grand Haven
(17.5 ^ni north of Port Sheldon) were mainly captured in the warmest water
available during September. Our data indicate that during years when the
inshore area of Lake Michigan is more or less isothermal, YOY distribution is
generally at depths of 9 m or less. Limited distribution to the 12- and 15-m
depths was also indicated during I979 and I98O (Fig. 21). During years when
either the natural cooling of Lake Michigan occurs or an upwelling results in
marked temperature differences between depth contours, YOY alewives will
probably remain in the warmest water temperatures available. Brandt (I98O)
suggested that their September YOY alewife distribution was independent of
depth and primarily related to water temperature.

The modal lengths of YOY taken in September varied from 30 mm in I98O to
60 mm in 1977 and 1979* A definite bi modal distribution was indicated in
September 1977* the modes of which were primarily separable by station. The
mode of YOY caught in September 1977 at station Q (south discharge) was 60 mm,
while the mode at other beach stations (P, south reference and R, north
discharge) was kO mm. This observed difference in modes may reflect the
increased ability of larger YOY to maintain themselves at the highest water
temperature available. Another possible explanation for the difference in

90

modes among beach stations may be that those YOY sampled at station Q in
September 1977 were part of the cohort spawned in the discharge canal earlier
in the season which subsequently moved into the adjacent Lake Michigan beach
zone.

It is during October that the first substantial movement of YOY to depths
greater than 9 m usually occurred (Fig. 21). In all years sampled, the
October YOY catch taken at 6- and 9"ni stations ranged from 12% of the total
monthly catch in 1979 to kO% in 1978, while at 12- and 15-ni stations this
percentage ranged from 12 in 1979 to 72 in 198O. During 1977 when the l8- and
21-m contours were sampled, 27% of all YOY captured were trawled at these
stations (Jude et al. 1978). While a definite offshore movement of YOY
alewives in October was indicated in all years, the extent of the movement was
variable. In I98O as low as 6% of the YOY were captured at beach and 3"ni
stations, while in 1979 as high as 76% were taken nearshore. The
extraordinary occurrence of YOY in the nearshore zone during October 1979 'Tiay
be related to the delayed spawning peak of alewives that year, resulting in a
prolonged stay in nursery areas.

In most years, during October sampling the temperature differences
between stations were subtle and temperature preference patterns were not
obvious. For whatever reason, however, a distinct offshore movement of YOY
alewives was indicated in all years (Fig. 21). The one sample collected at 21
m in October 1977 suggests the possibility that many YOY leave the study area
for greater depths (Jude et al. 1978). An examination of modal lengths of YOY
in October gives some indication that larger YOY migrate offshore ahead of
smaller YOY. For years 1977. 1979 and I98O the modal length for those larvae
captured at the beach and 3'ni stations was ^0 mm, while modal lengths for
those YOY caught at more offshore stations was 60 or 70 mm. Modes of 60 mm
were observed at all station combinations in 1978; however, there was a
bimodal distribution at beach and 3~ni stations with the additional mode at 30
mm •

During November, a continued offshore movement of YOY was indicated in
all years. The extent of the offshore movement, was variable. During 1977
when 18- and 21-m stations were sampled in addition to beach to 15""n[i stations,
6i+% of the YOY were captured at 21 m (Jude et al. 1978). During I978, 70% of
the YOY catch was made at depths of 6 and 9 m, while 90% of the YOY catch
during 1979 was taken about equally at the 6- to 9~n™ and 12- to 15*ni contours.
An even more extensive offshore migration in November I98O was indicated by
the comparatively low catches of YOY in the study area.

Without exception for 1977"1979 modal lengths of YOY caught at more
offshore station groupings were larger than those YOY caught at more inshore
stations. Modal comparisons during November I98O were precluded by the small
catch of YOY. These data further indicate that larger YOY do migrate offshore
ahead of smaller YOY. In all years, water temperature did not correlate with
any trend of YOY abundances.

91

20

10-

BEACH, 1.5,3 M

NORTH

SOUTH

1977

H 20

IT 10

h-
<

tr

LU

UJ

201-

ir

UJ
< 10

BEACH, 1.5, 3 M

.i.

1978

T y /-^

■''^>:^-.^

z-^^— 4l

r/

^^^^^

/

^^N^qr

1//^^^^^

"^

-^ ^^^ \r^'^^

1 1 1 1 1

BEACH, 1.5, 3 M

'5?=— 4-^

1979

BEACH, 1.5, 3 M

1980

-f^ 5s.T

20

. J

10

Ir

1

^*"'**""i^~-~~^

n

^^^

APR MAY JUN JUL AUG SEP OCT NOV DEC

SAMPLING PERIOD
Fig. 22 . Mean bottom temperatures observed during monthly sampling from June
to December 1977 and April to December 1978-1980 in eastern Lake Michigan, near
the J.H. Campbell Plant. Vertical bars denote temperature range.

92

20

20

UJ

6,9 M

NORTH

SOUTH

1977

6,9 M

1979

■^

i^x-

1>-

20

10-

6,9 M

APR MAY JUN JUL AUG SEP

SAMPLING PERIOD

Fig. 22. Continued.

1980

OCT NOV DEC

93

20-

10

12,15 M

1977

1978

20

10

12,15 M

1980

APR MAY JUN JUL AUG SEP

SAMPLING PERIOD
Fig. 22. Continued

OCT NOV DEC

94

Migration of YOY alewives from the inshore water of Lake Michigan near
the Campbell Plant was generally completed by December of each year. With the
exception of low numbers of smaller YOY (modal lengths 5O-6O mm) caught at
beach to 15-m stations in December 1979 and 1980, no substantial
concentrations of YOY were recorded in the study area during December,

Year 1 i ngs —

In general, catches of yearling alewives near Port Sheldon were lowest of
the three age-groups sampled. This concurred with Jude et al . (I98O) who
noted that yearlings were least abundant in samples taken near Bridgman,
Michigan (108 km south of Port Sheldon), Yearling alewives are reportedly
more pelagic and reside primarily offshore (Brown 1972; Wells I968) .

The exception to low catches of yearling alewives occurred during I98O.
In contrast to previous years* (1978 and 1979) sampling in which no yearling
alewives were caught during April, effort during April I98O indicated a
limited inshore distribution of yearlings (Fig. 21). This inshore presence
continued to occur in May I98O when over 200 yearlings were caught inshore,
compared with less than 25 caught in May I978 and 1979- During May I98O more
than 95^ of the yearling alewives were caught at beach to 9"ni stations
(Fig. 21). A continued inshore movement and increased abundance of yearlings
were observed in June I98O when over 2000 yearlings were caught primarily at
beach to 9-m stations. The total number of yearling alewives caught in June
1980 exceeded the total number of yearlings caught in all months sampled from
1977 to 1979 combined, and represented an extraordinary inshore migration of
yearlings in late spring 1980. Although the reason for this extensive inshore
migration of yearlings is unknown, it may be related to the previous year's
abnormal delay in the spawning peak for alewives. The prolonged and somewhat
delayed spawning season of 1979 seems to have resulted in a group of smaller
yearlings in I98O. During 1977'"1979 the modal lengths of the few yearlings
collected which returned to the inshore zone in June were 100 mm, 90 nini, and
120 mm respectively. Length-frequency data for yearling alewives caught in
June 1980 indicated a mode of 70 mm. It may be that smaller yearlings are
behavioral ly adapted to return again to the inshore zone during spring and
summer warming, while larger yearlings remain more offshore and are more
pelagic. During all years, most returning yearlings were caught at depths to
9 m.

Compared with previous years, the catch of yearling alewives during
August 1980 was still considerably larger, exceeding the August catch of all
previous years combined. Modal lengths however were similar among years
ranging from 90 to 120 mm. In all years relatively higher catches were made
at 6- and 9"ni stations in August. This trend was continued during September
sampling. Although these data may appear to indicate a preference for the
6- and S^m contours during August and September of most years, a more detailed
scrutiny of the data indicated alewives moved offshore. The majority of
yearlings caught during August and September of most years were taken in
surface gill nets which were only fished at 6-m stations, except in 1977-

95

In all years sampled, no yearlings were caught from October to December
suggesting that yearlings overwinter at depths greater than 21 m. Offshore
migration of yearlings was generally completed by late October of most years.

Adults--

From January until mid-April adult alewives were generally distributed
offshore in deeper water (greater than 15 ni) (Reigle 1969; Wells I968) . As
inshore water warms, adult alewives typically move inshore for an extended
period of spawning from May to September. Periodic upwel lings in spring and
summer months result in temporary offshore or alongshore movements and
interruption of spawning.

Seasonal di str ibut ion —

April and May — The first indication of an annual inshore migration of
adult alewives near the Campbell Plant occurred in April or May (Fig. 21).
During the 2 yr when adult alewives were caught in April (1978 and I98O)
catches were small (less than 100 fish). Gonad data (Fig. 23) indicated that
none of the adult alewives taken in April I978 or I98O had well developed
gonads, thus we believe that spawning was not occurring at this time. These
data, along with larval fish data, indicate that alewife spawning in the
vicinity of Port Sheldon generally does not occur prior to May.

Alewives exhibited a more substantial inshore movement in May when
compared with April during all years sampled (Fig. 21). Although accurate
numerical comparisons among the depth groupings were confounded by the
differential catch effort at each grouping, there was a clear indication that
adult alewives in May showed a major concentration at depths of 9 »" of" less
(Fig. 21) .

Gonad data showed as high as 30% of the alewives caught in May I98O had
well developed gonads or were ripe-running (Fig. 23). A small portion of the
adult catch in May I978 and 1979 were spent (Fig. 23). Collectively these data
indicate that alewife spawning in Lake Michigan near Port Sheldon usually
initiates during May, however a large part of the population sampled in May of
all 3 yr was not ready to spawn.

June — With the exception of June 1978, when less than 3OO adult alewives
were caught inshore (15 m or less), the catch of adult alewives in June of
other years exceeded 1000 alewives, and in June of 1977 and I98O exceeded 2000
adult alewives (Fig. 21). The vast majority of adult alewives taken in June
of any year were taken at 9 m or less (Fig. 21). Gonad data indicated that in
all years over 50% of those adult alewives caught in June had well developed
gonads or were ripe-running (Fig. 23). Generally between 5% and 20% of adult
alewives caught in June were spent (Fig. 23). These data indicate that
spawning activity toward the latter part of June in all years was intensified
compared with May. This is supported by larval fish data indicating a
hatching peak in early July of all years.

96

200-

100-

N = 380

O
UJ

o
o

X
CO

300
200
100

3001
UJ

3

H 200-

U- 100

o

UJ
CD

3

600

4010.

200-

ND

N32i

NO

N3290

NsO Nsl90

Ns6
1 I

APR MAY

N:380

Nr553

n

N«762

1977

B » WELL DEVELOPED AND
RIPE-RUNNING GONADS

n "SPENT GONADS

N:24S

r

Nsl87

n.

N = 626

1978

Nsl32

Ns279

I

N«335

1980

N2293

n

N<I82

979

N>293

n

NXI39 N=I93

Nsi8

Nst3

N«3
OCT

Nsl

N:2

NOV

NsO

Ns49 NsO

NsO
DEC

JUN JUL AUG SEP

SAMPLING PERIOD
Fig. 23. Number of mature alewives with well developed, ripe-running and
spent gonads collected monthly during June-December 1977 and April-Decem-
ber 1978^1980 near the J. H. Campbell Plant, eastern Lake Michigan. N =
total number of mature alewives caught per month.

97

July — As can be inferred from larval alewife data, July is typically the
time of most intensive alewife spawning near the Campbell Plant. During July

1978 and 1980 when water temperatures were highly conducive to spawning,
catches of adult alewives were high (over 3200 and over 1300 respectively) in
the inshore zone. During 1977 and 1979 when the warming trend was interrupted
by upwel lings, the catch of alewives in either year did not exceed 700 adults,
suggesting that adult alewives had to some degree moved offshore in response
to the upwel ling. In all years the distribution of those alewives that did
occupy the inshore zone was primarily at depths of 9 ni or less.

With the exception of July 1977f over 50% of those alewives caught in
July of other years showed advanced gonad conditions or were ripe-running
(Fig. 23) • In all years between 10% and 15% of all adult alewives examined in
July were spent (Fig. 23). These data suggest that we observed a progression
in gonad conditions through the spawning season. Individuals with well
developed gonads or which were ripe-running were still present in relatively
high proportions as was found in June, while generally higher proportions of
spent individuals were being caught compared with June of the same years. The
extraordinary low proportion of adult alewives with advanced gonad condition
in July 1977 (less than 20%) was probably due to the upwel ling which occurred
then and may have induced potential spawners to temporarily move offshore.

August — The catch of adult alewives inshore in August of all years
exhibited a marked decline compared with respective July periods (Fig. 21).
This indicated that generally an offshore migration by adults from the inshore
zone near Port Sheldon began in August. Relative distribution of those adult
alewives that had remained inshore exhibited some variation. During August

1979 the distribution of adult alewives in the inshore zone was primarily at 9
m or less (Fig. 21). During 1977 when depths to 21 m were sampled, higher
densities of alewives were observed at the beach and 3""^ depths and the l8-m
station compared with the intermediate 6- to 15"ni depth groupings. Sampling
in August 1978 and I98O indicated that alewives were primarily distributed at
depths of 6 m or greater (Fig. 21).

Gonad data from all years showed only a small proportion of those adult
alewives examined in August (less than 5% " Fig. 23) had yet to spawn, while
an increased percentage of adult alewives caught in August of all years,
except 1980, were spent. It is possible that the more advanced progression of
the adult alewife population through the spawning season was responsible for
the more random distribution of adults in the inshore zone in August, compared
with the more pronounced preference for depths 9 ni or less which was indicated
in July of all years.

September — In most years the abundance of adult alewives in September
catches at depths of 15 m or less did not significantly differ from August
collections. The exception to this pattern was during September 1977 when
there was a two-fold increase in the adult catch in September compared with
August of that year. During all years, September sampling indicated that
adult alewives were less concentrated in the nearshore zone compared with
August, however the extent of their offshore migration was variable (Fig. 21).
The adult alewife catch in September of all years indicated that there were no

98

fish with well developed gonads or which were ripe-running (Fig. 23). It is
likely that alewife spawning for the most part was completed by September.
Larval fish data do indicate, however, that limited alewife spawning did occur
into September 1979. During years when extended periods of upwelling delayed
the major spawning period for alewives, more intense spawning into the later
extremes of the spawning season were observed.

October, November and December — From October to December adult alewives
were only rarely caught in the inshore zone near the Campbell Plant. A
massive offshore movement of adult alewives probably occurs coincident with
the rapid autumn cooling of the inshore zone in late September to early
October in most years.

Plant Effects —

A Wilcoxon signed ranks test combining data from all k yr indicated that
there were no significant differences in the densities of larval alewives
collected between north and south transects. Year to year variability in
relative abundances of larval alewives between transects was, however, clearly
demonstrated by annual Wilcoxon signed ranks testing. The combined monthly
data for 1978 indicated that significantly higher densities of larval alewives
were observed at the south transect compared with the north transect for that
year (a » .OI58) . Conversely, during I98O, combined monthly data indicated
significantly higher densities of larval alewives at the north transect
compared with south transect stations (a « .0002). For both 1977 and 1979 no
significant differences in the abundances of larval alewives between transects
was indicated. These data collectively suggest that a single year transect
comparison in I98I will be inconclusive in ascertaining the effect of Unit 3
operation on larvae, since there is approximately equal probability that in
any 1 yr north or south transect stations would have significantly higher or
lower densities of larval alewives. These data also suggest that operation of
Units 1 and 2 is not significantly affecting the abundances of larval alewives
in the vicinity of Port Sheldon.

Over the k yr, the catch of adult and juvenile alewives did not
significantly differ between north and south transect stations based on bottom
gill net, surface gill net, seine and trawl data (Figs. 2^-27» Tables 19"26) .
Simplified north transect-south transect comparisons were confounded by a
variety of interactions (Tables 19"26) ; however, these interactions are
primarily related to life history peculiarities of alewives previously
explained. The greatest disparity in catch of adult and juvenile alewives
between transects occurred in 1978, when an extraordinarily high trawl catch
at the north transect in November caused the AREA factor in the ANOVA to
almost approach significance (Fig. 27. Table 26). Other than this spurious
event, we detected no significant buildup or depletion of fish at either
transect. We thus feel that the thermal plume is not causing any significant
shift in the distribution of adult and juvenile alewives near the Campbell
Plant.

99

ALEWIFE

J-,

-*

♦

z

o

N

^^^^

^ — »>.

S6

>

N

N

\.

H-

N

^s.

Ui

N

^s,,,^

z

\

N

\^

^

d «

.

^ — — . -.

C9

■~ "~ — -».

*^

z

s

UJ

z

o2

.

ta«

oc

>-

Ui

z

o

UJ

o

-, „- I„,

.—

,___

__

.,1 -, - -.-,., I -.

1978

1979
YERft

1980

BOTTOM GILL NETS

STATION C (REFERENCE)

STATION L (PLANT)

SURFACE GILL NETS

STATION C (REFERENCE)

STATION L (PLANT)

1980

Fig. 24. Geometric mean number plus one of alewives caught in
bottom gill nets and surface gill nets at stations C (6 m, south)
and L (6 m, north) near the J. H. Campbell Plant, eastern Lake
Michigan, 1978 through 1980. Graphs illustrate the YEAR X
STATION interaction.

100

ALEWIFE

108

90

cc

o

72

liJ

z

•■4

Ul

en

54

38

Lj 18

UJ

SEINES

STATION P

STATION

STATION R

1977

1978

1979

1980

TEAR

Fig. 25, Geometric mean number plus one of alewives caught in
seines at beach stations P (south reference) , Q (south discharge)
and R (north discharge) near the J. H. Campbell Plant, eastern
Lake Michigan, 1977 through 1980. Graph illustrates the YEAR X
STATION interaction.

Although an estimate of larval alewives lost to entrainment by Unit 3
must await analysis of data from I98I entrainment sampling, a certain amount
of predictability is allowed from observation of trends during preoperational
years 1977-1980. Highest entrainment of larval alewives will probably
coincide with the alewife hatching peak in any year. In most years, this
hatching peak occurred in July, but during years of extensive upwel lings, the
hatching peak may be delayed until August. During alewife hatching peaks,
larval alewives were generally distributed to depths of at least 15 m. We
believe that during hatching peaks, most alewives present will be newly

101

15

<

UJ

+

10

2

X

o

o

y-

<

E

o

H

UJ

_i

5

o

I.I

1

O

ALE WIFE

STATIONS C AND D
(REFERENCE)

.^STATIONS L AND N
(PLANT)

1978

1979
YEAR

1980

Fig, 26. Geometric mean number plus one of alewives caught in trawls

at stations C (6 m, south), D (9 m, south), L (6 m, north) and N (9 m,

north) near the J. H. Campbell Plant, eastern Lake Michigan, 1978 through
1980. Graph illustrates the YEAR x AREA interaction.

hatched, and thus be passively carried by water currents. It is doubtful at
this point whether the majority of these newly hatched larval alewives will be
able to avoid the intake current at the Unit 3 structures.

There are two factors which will tend to attenuate entrainment loss
through Unit 3, although the degree of attenuation in each case will be highly
variable. Our data indicate that location of the Unit 3 intake structures at
11 m will result in less entrainment loss compared to water withdrawal at a
shallower depth contour (see Tables 15-18 also). Over the k yr sampled, there
was a general tendency for larvae, at times other than an intense hatching
peak, to be more concentrated at depths of 9 m or less. This trend was
particularly evident during times of upwelling.

A second factor which will tend to limit entrainment of larval alewives
at Unit 3 relates to the location of the intake structure in the water column.
In the majority of cases, surface strata at the 12- and 15-ni stations had
higher densities of larval alewives than did bottom strata. Thus, as opposed
to a surface withdrawal of cooling water, the bottom water withdrawal (lower
3-i*-m strata) of Unit 3 wi 1 1 probably entrain fewer alewife larvae.

102

Table 19. Analysis of variance summary for alewives caught in bottom
gill nets at stations C (6 m, south) and L (6 m, north) near the J, H,
Campbell Plant, eastern Lake Michigan, 1977 through 1980. Data for
July through September were analyzed.

Attained

Source

of

significance

variation

df

Mean square

F-statistic

level

Year

3

0.431i

4.5213

0.0072'>

Month

2

0.5325

5.5856

0.0066*

Station

1

0.i3'*5

1.9354

0.1706

Time

1

O.U58a

4.3084

0.0332

Y X M

6

1.0680

11.2023

<0.0001**

Y X S

3

0.5729

6.0091

0.0015*

M X S

2

0.0126

0.1337

0.8751

Y X T

3

1.1570

12.1350

<0.0001**

M X T

2

2.2a81

23.5794

<0.0001**

S X T

1

0.002U

0.0256

0.8736

Y X M X

S

6

0.3497

3.6678

0.0045*

Y X M X

T

6

1.5296

16.0438

<0.0001**

Y X S X

I

3

0.2507

2.6290

0.0608

M X S X

T

2

0.5266

5.5438

0.0068*

Y X M X

S X T

6

0.4792

5.0260

0.0005**

Within cell

error

48

0.0953

** Highly significant (P < 0.001).
* Significant (P < 0.01).

Table 20. Analysis of variance summary for alewives caught in bottom
gill nets at stations C (6 m, south) and L (6 m, north) near the J. H.
Campbell Plant, eastern Lake Michigan, 1978 through 1980. Data for
June through September were analyzed.

Attained

Source

of

significance

variation

df

Mean square

F-statistic

level

Year

2

0.3138

3.5343

0.0354

Month

4

1.0745

12.1022

<0.0001**

Station

1

0.2268

2.5540

0.1153

Time

1

1.1024

12.4165

0.0008**

Y X M

3

0.9413

10.6019

<0.0001**

Y X S

2

0.15C8

1.6982

0.1917

M X S

4

0.3139

3.5351

0.0118

Y X 1

2

1.3593

15.3101

<0.0001**

M X T

4

1.6841

18.9681

<0.0001**

S X T

1

0.0500

0.6758

0.4143

Y X M X

S

8

0.2764

3.1355

0.0050*

Y X M X

T

8

1.4462

16.2881

<0.C001**

Y X S X

I

2

0.7802

8.7868

0.0004**

M X S X

T

4

0.6972

7.8525

<0.0001**

Y X M X

S X T

8

0.1633

1.3395

0.0872

Within cell

error

60

0.0888

** Highly significant (P < 0.001).
* Significant (P < 0.01).

103

Table 21. Analysis of variance summary for alewives caught in bottom
gill nets at stations C (6 m, south), D (9 m, south), L (6 m, north)
and N (9 m, north) near the J. H. Campbell Plant, eastern Lake Michigan,
1980. Data for June through September were analyzed.

Attained

Source

of

significance

variat:

Lon

df

Mean square

F-statistic

level

Month

i,5ee6

20.9999

<O.0OCl««

Area

0.0469

0.6540

0.4247

Depth

1.5915

21.3055

0.0001**

Time

0.26U9

3.5457

0.0688

M X A

0.1015

1.3591

0.2729

M X D

0.6812

9.1199

0.0002«

A X C

0.0023

0.0304

0.8627

M X T

^.2eSk

57.1026

<0.0001*«

A X T

0.0384

1.1837

0.2847

D X T

C.7055

9.4455

0.0043*

M X A X

D

0.3352

4.4869

0.0097*

M X A X

T

0.2423

3.2506

0.0345

M X D X

T

o.a06e

5.4458

0.0039*

A X D X

I

0.0469

0.6283

0.4338

M X A X

D X T

0.2999

4.0134

0.0156

Within <

:ell

error

32

0.0747

** Highly significant (P < 0.001).
* Significant (P < 0.01) .

Table 22. Analysis of variance summary for alewives caught in sur-
face gill nets at stations C (6 m, south) and L (6 m, north) near the
J. H. Campbell Plant, eastern Lake Michigan, 1977 through 1980.
for July through September were analyzed.

Data

Attained

Source

of

si'jnif icance

variation

df

Mean square

f-statistic

level

Year

0.3633

2.0007

0.1337

Month

2.3445

12.9123

0.0011*

Station

0.0801

0.4412

0.5113

Time

18.1489

99.9537

<0.0001**

Y X M

0.2594

1.4285

0.2526

Y X S

0.2158

1.1883

0.3297

M X S

0.2384

1.3132

0.2603

Y X T

0.7154

3.9403

0.0169

M X T

0.0911

0.5018

0.4838

S X T

0.4537

2.4985

0.1238

Y X M X

S

0.3922

2.1600

0.1121

Y X M X

T

0.4723

2.6011

0.0691

Y X S X

T

0.6412

3.5313

0.0257

M X S X

T

0.5437

2.9946

0.0932

Y X M X

S X T

0.8406

4.6293

0.0085*

Within <

jell

error

32

0.1S16

** Highly significant (P < 0.001).
* Significant (P < 0.01).

]0k

Table 23. Analysis of variance summary for alewives caught in sur-
face gill nets at stations C (6 m, south) and L (6 m, north) near the
J. H. Campbell Plant, eastern Lake Michigan, 1978 through 1980. Data
for May through September were analyzed.

Attained

Source

of

significance

variation

df

Mean square

F-statistic

level

Year

2

0.23ia

2.0504

0.1376

Month

U

0.8758

7.7611

<0.0001««

Station

1

0.2760

2.4634

0.1218

Time

1

38.2369

338.8459

<0.0001«

Y X M

8

0.2667

2.3637

0.0278

y X S

2

0.22148

1.9923

0.1453

M X S

a

0.2075

1.8384

0.1333

Y X T

2

0.3a56

3.0622

0.0542

M X T

14

0.ieu2

1.6320

0.1780

S X T

1

O.C77a

0.6862

0.4107

Y X M X

S

8

0.3370

3.4297

0.0026*

Y X M X

T

8

0.3629

3.2161

0.0042*

Y X S X

T

2

0.7753

6.8703

0.0021*

M X S X

T

k

0.8569

7.5933

0.0001**

Y X M X

S X T

8

0.4032

3.5729

0.0019*

Within cell

error

60

0.1128

** Highly significant (P < 0.001)
* Significant (P < 0.01) .

Table 24. Analysis of variance summary for alewives caught in seines
at stations P (south reference), Q (south discharge) and R (north dis-
charge) near the J. H. Campbell Plant, eastern Lake Michigan, 1977
through 1980. Data for June through September were analyzed.

Attained

Source

of

significance

variation

df

Mean square

P-statistic

level

Year

3

15.6723

68.1479

<0.0001**

Month

3

11.2659

48.9874

<0.0001**

Station

2

0.2475

1.0762

0.3450

Time

1

0.5471

2.3789

0.1263

Y X M

9

2.0260

8.8185

<0.0001**

Y X S

6

0.2327

1.0120

0.4222

M X S

6

0.5030

2.1874

0.0507

Y X T

3

0.4469

1.9431

0.1278

M X T

3

12.1781

52.9540

<0.0001**

S X T

2

0.5S07

2.5250

0.0854

Y X M X

c

18

0.6467

2.8122

0.0006**

Y X M X

T

9

1.6064

7.8549

<0.0001**

Y X S X

T

6

0.6432

2.7967

0.0150

M X S X

X

6

0.9522

4.1403

0.0010**

Y X M X

S X T

18

0.8784

3.8193

<0.0001**

Within cell

error

96

0.2300

** Highly significant (P < 0.001)
* Significant (P < 0.01).

105

Our investigations of the distribution of young-of-the-year (YOY)
alewives, another group of alewives possibly subject to entrainment (see
Schneeberger and Jude I98O) or impingement loss at Unit 3» indicate that
maximum loss would be expected during October or November. At this time YOY
were shown to exhibit an offshore movement. Prior to this time of year, as
indicated by our trawl and seine catches, YOY remained primarily closer to
shore at depths of 9 ni or less, and often exhibited an extreme inshore (beach
to 3 ni) distribution.

Although maximum loss of YOY alewives might be expected to occur in
October and November based on distributional data, an accurate prediction of
the magnitude of loss is not possible. Since YOY alewives could probably
avoid the predicted intake current (maximum through-slot velocity 15«2 cm/s) ,
behavioral factors rather than mere distributional coincidence will be
responsible for any YOY alewife loss.

Rainbow Smelt

I ntroduction —

Rainbow smelt populations in Lake Michigan, as indicated by commercial
catches, fluctuated widely during the period 1931"1972 (Wells and McLain
1973) • Near the J. H. Campbell Plant, rainbow smelt abundance appeared to be
steadily increasing during 1977-1980. Rainbow smelt accounted for 16.4%,
27.8%, 38.4% and 43.6% of the total juvenile and adult fish catches in Lake
Michigan in 1977» 1978, 1979 and I98O respectively (Table 10). During
1977'" 1978 smelt was the second-most numerous species caught in the study area
after alewife. In 1979"1980 smelt ranked first in numerical abundance over
all juvenile and adult fish collected. Rainbow smelt larvae were, however,
less frequently caught than larvae of other abundant species in the study
area, such as alewife and spottail shiner. Density of larval rainbow smelt
varied considerably during 1977-1980 (Figs. 27-36) • Highest densities of
smelt larvae were observed during 1979* Rainbow smelt generally migrate
inshore during spring and return to deeper water during fall and winter.
Early life stages of rainbow smelt were caught in plankton nets and sleds from
May to August. YOY larger than 25-4 mm and yearlings were mostly caught in
trawls. In addition, fish in these two size groups were occasionally found in
seines. Adult smelt occurred mostly in bottom gill nets and trawls.

Larvae —

Seasonal di str i but ion —

May — In 1977 fish larvae sampling was not performed during April and May.
During 1977 smelt larvae were first collected in June (Fig. 27) • During
1978-1980, smelt larvae first occurred in the study area from 14 to 19 May
(Figs. 28-36). Weekly entrainment sampling conducted at the Campbell Plant
during 1978 and 1979 (Jude et al . 1979a; Jude et al . 198O) captured no smelt
larvae during early May suggesting that larvae collected from 14 to 19 May
were among the first brood of smelt larvae in the study area during I978-I98O.
Near the Cook Plant, southeastern Lake Michigan, smelt larvae were first

106

Table 25. Analysis of variance summary for alewives caught in trawls
at stations C (6 m, south) and L (6 m, north) near the J. H. Campbell
Plant, eastern Lake Michigan, 1977 through 1980. Data for June through
November were analyzed.

Attained

Source

of

significance

variation

d£

Mean square

F-statistic

level

Year

3

0.5221

3.0635

0.0318

Month

5

7.3258

42.9810

<0.0001««

Station

1

0.3768

2.2106

0.1403

Time

1

1.3861

8.1324

0.0053*

y X M

15

3.0990

18.1822

<0.0001*«

Y X S

3

0.2179

1.2782

0.2863

M X S

5

0.2823

1.6561

0.1527

Y X T

3

2.2918

13.4461

<0.0001**

M X T

5

0.5020

2.9454

0.0162

S X T

1

0.0627

0.3681

0.5455

Y X M X

S

15

0.4022

2.3600

0.0063*

Y X M X

T

15

0.9374

5.5001

<0.0001*«

Y X S X

T

3

0.6514

3.8216

0.0124

M X S X

T

5

0.4868

2.8560

0.0190

Y X M X

S X T

15

0.4211

2.4704

0.0042*

Within cell

error

96

0.1704

** Highly significant (P < 0.001)
« Significant (P < 0.01) .

observed during 26-27 April in 1973 and 2-3 ^ay in 197^ (Jude et al. 1979b).
Late appearance of smelt larvae near the Campbell Plant was probably due to a
late spawning run caused by lower water temperatures in this part of Lake
Michigan during spring (see Adult-this section). Water temperatures ranged
from 7.^ to 12 C during 18-24 April 197^ at the Cook Plant (Jude et al . 1979b)
and from 3.5 to 7 C during 21-22 April I98O (Appendixes 5 and 6) near the
Campbell Plant. Lower temperatures at the Campbell Plant may have also
delayed hatching of smelt larvae. Incubation time of smelt eggs varies
inversely with water temperatures. McKenzie (1964) reported an incubation
period of 29 days at 6 to 7 C, 25 days at 7.1 to 8.5 C and I9 days at 9 to 10
C. Cooper (1978) observed smelt hatching 8 to 9 days after fertilization at a
mean water temperature of I6.5 C. At Ludington, located approximately 120 km
north of the Campbell Plant on eastern Lake Michigan, smelt larvae were first
collected around mid-May in I978 (Listen et al. I98O) .

Rainbow smelt larvae collected during May ranged from 5 to 8 mm during

1978-1980 (Figs. 28-36). Mean length of smelt larvae collected during 14-16

May 1978, 16-17 May 1979 and 19-20 May I98O was 6.0, 5-5 and 5-8 mm

respectively indicating that most larvae collected during mid-May were newly

hatched (Scott and Crossman 1973; Cooper 1978). Smelt larvae collected in the

shallow area (beach-3 m) and those found at deeper water (6-I5 m) were in the
same size range (Figs. 28-36).

107

Table 26. Analysis of variance summary for alewives caught in trawls at
stations C (6 m, south), D (9 m, south), L (6 m, north) and N (9 m, north)
near the J. E. Campbell Plant, eastern Lake Michigan, 1978 through 1980.
Data for June through November were analyzed.

Attained

Source

of

significance

variation

d£

Mean square

F-statistic

level

Year

2

1.7032

11.1799

<0.0001**

Month

5

18.7503

123.0799

<0.0001*«

Area

1

0.8984

5.8970

0.0164

Depth

1

0.4830

3.1703

0.0771

lime

1

0.0006

0.0037

0.9517

Y X M

10

5.4579

35.8262

<0.0001**

y X A

2

0.1240

0.8137

0.4452

M X A

5

0.6012

3.9463

0.0022*

Y X D

2

0.5282

3.4674

0.0338

M X D

5

0.7443

4.8857

0.0004**

A X D

1

0.0914

0.5997

0.4400

Y X T

2

6.9363

45.5308

<0.0001**

M X T

5

1.4837

9.7391

<0.0001**

A X I

1

0.3565

2.3401

0.1283

D X T

1

2.7351

17.9533

<0.0001**

Y X M

X

A

10

0.4361

2.8626

0.0028*

Y X M

X

c

10-

0.2113

1.3872

0.1917

Y X A

X

D

2

0.3357

2.2035

0.1141

M X A

X

D

5

0.3997

2.6236

0.0265

Y X M

X

T

10

1.5489

10.1670

<0.0001**

Y X A

X

T

2

0.9170

6.0190

0.0031*

M X A

X

T

5

0.3204

2.1029

0.0684

Y X D

X

I

2

0.0082

0.0538

0.9477

M X D

X

T

5

0.4191

2.7513

0.0209

A X D

X

T

1

0.1006

0.6604

0.4177

Y X M

X

A

X

D

10

0.5802

3.8083

0.0001**

Y X M

X

A

X

T

10

0.5921

3.8868

0.0001**

Y X M

X

D

X

I

10

0.1376

0.9033

0.5319

Y X A

X

D

X

I

2

0.2625

1.7230

0.1822

M X A

X

D

X

T

5

0.3363

2.2074

0.0567

Y X M

X

A

X

D X T

10

0.2356

1.5467

0.1287

Within '

cell

error

1**

0.1523

.

»<s Highly significant (P < 0.001).
« Significant (P < 0.01) .

During /lay smelt larvae were more abundant in the shallow area (beach-3
m) than in deeper water (6-15 m) (Figs. 28-37). Mean densities in the beach
to 3-m zone ranged from 1 to 213 larvae/1000 m^ during May 1978, 1979 and
1980. High abundance of smelt larvae in shallow water during May was also
observed in eastern Lake Michigan nea^- the Palisades Power Plant (WAPORA 1979)
and near Ludington (Listen et al. 19£U . Rainbow smelt are known to spawn in
shallow water (Daly and Wiegert 1958; Rupp 1959; Jude et al . 1979b) and some

108

spawning takes place sooner at 1 to 3 ni than at 6 to 15 m. Most larvae we
collected during May probably hatched in the shallow area (beach-3 m) although
some hatching may have started in deep water (6-15 m) by the May sampling
period. Newly hatched larvae collected at 12 and 15 m (Figs. 30, 33, 36) may
have hatched at these depths or may be carried from shallow areas by offshore
currents. During 14-16 May 1979 on the south transect, smelt larvae were
relatively abundant at 12 and 15 m and were scarce at the beach to 3 m,
probably because most larvae that hatched in the shallows were dispersed to
deeper water at sampling time (Figs. 31"33) • Alongshore current (either north
or south) which occurs frequently in the vicinity of the J. H. Campbell Plant
at speeds varying from to 30 cm/s (Liston and Tack 1976), also contributed
to the quick dispersal of newly hatched smelt larvae.

Mean densities of smelt larvae in the study area during May were 15. 31

and kS larvae/1000 m^ in 1978, 1979 and I98O respectively. During 1978-1980

smelt larvae were generally more abundant during May than other sampling

periods (Figs. 28-37)* Weekly entrainment sampling performed during 1978 and
1979 (Jude et al. 1979a. I98O) revealed that peak smelt hatching in the study

area occurred during late May. In eastern Lake Michigan near Ludington,

Michigan, Liston et al. (I98O) observed highest density of smelt larvae at the
end of May in 1978.

June — Smelt larvae were scarce during early June. No smelt larvae were
collected during 1-2 June ' 1977* Mean larval density during early June
(1978-1980) ranged from to 10 larvae/1000 m^ (Figs. 28-36). Scarcity of
smelt larvae during early June was due to low hatching intensity during this
period and dispersal of larvae hatched in May to deeper water. Smelt larvae
collected were 5 to 15 nwn, 4.1 to 14 mm and 4.1 to 13 mm during 5-IO June
1978, 4-6 June I979 and 2-4 June I98O respectively. The cohort that hatched
in May was approximately 8 to 15 mm and made up the major portion of smelt
larvae collected during early June I978 and 1979. while newly hatched larvae 5
to 7-5 "im predominated during early June I98O (Figs. 28-36). Reasons for this
change in size composition are not known. As was found during May, no
difference in size of larvae collected between shallow and deep water was
observed.

Smelt larvae abundance was generally higher during late June than early
June, in particular during 1979 and I98O (Fig 37). Mean density of smelt
larvae in the study area during late June was 4, 44 and 19 larvae/1000 m^
during 1978, 1979 and I98O respectively (Table 27). in I978 and I98O,
increase in larval density during late June resulted in part from catches of
higher numbers of larvae 5-7.5 mm (Figs. 27*36) suggesting that substantial
hatching took place between the early and late June sampling periods. During
1979 the increased density was due mainly to capture of a larger number of
larvae 10 to 20 mm. Smelt larvae collected during late June I98O, however,
included mostly recently hatched larvae 5 to 8 mm (Figs. 34-36). Reasons for
the scarcity of larvae larger than 8 mm during late June I98O are not known.
In 1978, both recently hatched larvae (5-7.5 mm) and larger larvae (8-I5 mm)
were scarce during late June (Figs. 27-30). Variability of abundance of smelt

109

40 +

O

O 10

UJ

<
>

<

z

1977

12 ANO IS M

DENSITY TRANSECT TEMP.

D
3

NORTH
SOUTH

T

H

"i J

1

-• 25

-• 20

-• 15

'• 10

- 5

UJ

q:

U
CL

UJ

17-22 JUN

20-28 JUL

21-23 SEP

40 1
30
20-1
10

Z
Ui

o

S 40

30

20

10

1977

20-28 JULY

LAKE MICHIGAN
STATION 12-15M
N. TRANSECT
DAY-I-NIGHT
X-20.5 (2.5)
N- 2

/ f:

9| 21-23 SEPTEMBER 1977
o LAKE MICHIGAN
"LSTATION 12-15M
/N. TRANSECT
DAY+NIGHT

X-150 (0.0)
N- 1

\

17-22 JUNE 1977
LAKE MICHIGAN
STATION 12-15M
S TRANSECT
DAY + NIGHT

X- 6.0 (0 0)
N- 1

5 10 15 20 25 5 10 15 20 25

5 10 15 20 25

TOTAL LENGTH (MM)

Fig. 27. Density (no./lOOO M"^ plotted on log scale) of larval rainbow smelt
collected during June to Septeinber 1977 at 12 and 15 m (all contours, depth
strata and diel periods pooled) near the Campbell Plant, eastern Lake Michigan,
Horizontal line across each bar denotes mean density while height of bar re-
presents ± 2 S.E. Midpoint of water temperature range (vertical line) at time
of collection is shown. Length-frequency histograms for all larvae collected
during each period are also shown. N =* number of larvae collected, x = mean
length of larvae, S.E. given in parentheses.

no

(D) adnivd3dW3i

£W000l/3VAdVl ON

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CO

o

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z

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^"^

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CO

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CO

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CO CO

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CO S

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U CO

CO hJ

CX3 C
r^ U

CO

U CO

•i .

Q- CO

(U iH

o

c

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•H 00
S O

4J

CO

• -H

W X

CO

00

G
0)

IX

0)
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a

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U 00

11

-• 25

+ 20^

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+ 155

10 w

'• 5

40
30
20
10

UJ

g 40

30
20

to

15-18 MAY

15-18 MAY 1978
LAKC UIC^HGAN
STATION 6-9M
M. TRANSECT
OAY+MCHT
X- 8 2 (0 0)

5-10 UUN

1-4 AUO

I

'I S-10 JUNC 1978
: LAKE MICHICAN
MUTATION 8-9M
/it TRANSECT
^ DAY *HtGHr
X- 8 5 (J 5)

tS-tS MAY t978
LAKE MICHIGAN
STATION 6-9M
S. TRANSECT
OAr-*-NM>fr
X- 70 (0 4)

S-W JUNE 1878
LAKE MICHICAN
STATION 8>9M
S. TRANSECT
DAY ♦NIGHT

1»-U JUNC ItTt
f LAKC MICMQAN
STATION 8-8M
N. nUNSCCT
OAY-H>«IGHT
i-10.1 (3 J)

t-3 JULY 1978
LAKE MtCHlGAN
STATION 6-8M
N TRANSECT
0AY>NICHT

1-4 AUGUST 1978
LAKE MtCHICAN
STATION 6-9M
N TRANSECT
OAY ♦NIGHT

19>2J JUNE ^78
LAKE MCHKAN
STATION 8-9M
S TRANSECT
OAY^NKKT
5- 7 5 (0 0)

5 10 15 20 25

1-3 JUIY 1978
LAKE MTMCAN
STATION 8-9W
S. TRANSECT
OAY^MGHT
X- 7 8 (17)

5 10 15 20 25

5 10 15 20 25 5 10 15 20 25 5 10 15 20 25
TOTAL LENGTH (MM)

Fig. 29. Density (no./lOOO w plotted on log scale) of larval rainbow smelt
collected during April to September 1978 at 6 and 9 m (all contours, depth
strata and diel periods pooled) near the Campbell Plant, eastern Lake Michigan.
Horizontal line across each bar denotes mean density while height of bar re-
presents ± 2 S.E. Midpoint of water temperature range (vertical line) at time
of collection is shown. Length-frequency histograms for all larvae collected
during each period are also shown. N = number of larvae collected, x = mean
length of larvae, S.E. given in parentheses.

112

30 -•

10

12

ANO 15 M

O

o

g

<
>

<

o

z

'

L

DENSITY TRANSECT TgMP.

D

NORTH
SOUTH

1978

PI

/
/

/
/

/
/

/

15-18 MAY

S-IO JUN

/
/

19-23 JUN

T
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/

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/
/
/
/
/
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/
/
/
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-> 25

20 a

q:

<

q:

15 UJ

a.

2

•• 10

•• 5

1-3 JUL

40
30
20
10 ^

ir

tS-18 kMV 1978
LAKE MCHiCAN
STATION 12-J5M
N. TRANSECT
DAY -f NIGHT

5 10 15 20

30 ^

20

10

'I*

k

5-10 JUNC 1978
LAKE MICHIGAN
~TATK)N 12-I5M
I. TRANSECT
OAY-t-NtGHT
X- 8.7 (2 7)

5-10 JUNE 1978
LAKE MICHIGAN
STATION 12-15M
S TRANSECT
DAY ♦NIGHT

19-13 JUNei978
LAKE MICHIGAN .
STATION 12 -15M
N TRANSECT
OAY-fNKJHT
X-13 7 (2.8)

• 19-23 JUNE 1978

- LAKE mk:hk;an

STATKX I2-I5M
S TRANSECT
DAY 4- NIGHT
X- 7 1 (1 1)

1-3 JULY 1978

LAKE mk:hn;an

STATK>N 12-15M

n transect
oay4Nk;ht

I J .JULY I9?fl

LAKE mchk;an

STATH)N 12-t'SM
S TRANSECT

Oay>nk;ht

11

5 10 15 20 25 5 10 15 20 25 5 10 15 20 25
TOTAL LENGTH (MM)
Fig. 3C. Density (no./lOOO M^ plotted on log scale) of larval rainbow smelt
collected during April to September 1978 at 12 and 15 m (all contours, depth
strata and diel periods pooled) near the Campbell Plant, eastern Lake Michigan.
Horizontal line across each bar denotes mean density while height of bar re-
presents ± 2 S.E. Midpoint of water temperature range (vertical line) at time
of collection is shown. Length-frequency histograms for all larvae collected
during each period are also shown. N = number of larvae collected, x = mean
length of larvae, S.E. given in parentheses.

113

BEACH — 3 M

QENStTY TWAMSECT TEMP.

NORTH

SOUTH

T
I
I
I

I

I
I
1

20

- 15

cr

<
q:

10%

.. 5

4-6 JUN

u

a:

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ql

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s

M)

il)

11) -

14-16 MAY t979
LAKE MICHIGAN
BEACH- 3M
N TRANSECT
DAY ♦ NIGHT
X- 5 5 (0 I)
N- 33

Si

4-6 JUNE 1«7»
LAKE MICHIGAN
BEACH- 3M
N TRANSECT
OAY^NIGHT
X- 6 5 (0 0)
N- 1

18-20 JUN

ia-20 JUNE 1979
LAKE MICHICAN
BEACH- 3M
N TRANSECT
DAY ♦NKiHT
X- 80 (to)
N- M)

2-9 JUL

17-19 JUL

2-3 JULY 1979
LAKE MICHIGAN
BEACH- 3M
N TRANSECT
DAY ♦■NKJHT
169 (t8)

X

17-19 JULY 1979
LAKE m(ghk;an

BEACH -3M
N TRANSECT

Oay+nk;ht

40 1

30

20

10-

14-16 MAY 1979
LAKE MICHIGAH
BEACH- 3M
S TRANSECT
OAY+NWHT
X- 5 (0 0)
N- 1

5 10 15 20

ie-20 JUNE »79

LAKE mh:hn;an

BEACH- 3M
S TRANSECT
OAY tNICHT
X- 6 3 (0 3)
N- 6

5 10 15 20 25 5 10 15 20 25

5 10 15 20 25

5 10 15 20 25
TOTAL LENGTH (MM)

Fig. 31. Density (no./lOOO M^ plotted on log scale) of larval rainbow smelt
collected during April to September 1979 at beach -3m (all contours, depth
strata and diel periods pooled) near the Campbell Plant, eastern Lake Michigan.
Horizontal line across each bar denotes mean density x^ile height of bar re-
presents ± 2 S.E. Midpoint of water temperature range (vertical line) at time
of collection is shown. Length-frequency histograms for all larvae collected
during each period are also shown. N = number of larvae collected, x - mean
length of larvae, S.E. given in parentheses.

11^4

14-16 MAY

40
30
20

H 10

z

^ 30
20
10 i

- tR MAY

•979
LAKE MICHIGAN
STATION 6-9M
N TRANSECT
OAY>NICHr
X- 5 8 (O I)

14- J6 MAY 1979
LAKE MtCHIGAN
STATION 8-9M
S TRANSECT
DAY -f NIGHT
X- 6 3 (0 4)

6 ANO 9M

OCMSITY

TRANSECT TEMP.

E

NORTH

20

15 UJ
q:

UJ

10 ^

UJ

.. 5

4-6 JUN

4-6 JUNC »79

LAKE MCHIGAN
STATION 6-»U

N. TRANSeCT
OAY-t-NKMT

4-6 JUNC 1»7«
LAKE MICHIGAN
STATION 6-»y
S. TRANSECT
OAY-t-MCHT
X-10 3 (0 5)
N- IS

18-20 JUN

«-20 JUNC 1>7«

LAKE mn;higan

STATKM 6-9M
N TRANSECT
OAY^MGHT
X-10 6 (OS)

JilL JlLlL .

l»-20 JUNC W79
LAKE MCMGAN
STATION 6-9M
S TRANSCCT
OAY-fMGHT
X-13 3 (0 9)
N- 22

2-3 JUL

17-19 JUL

2-3 JULY lt7».
LAKE MICHKUN
^TATKm 6-9M
N TRANSECT
OAY-t-MCHT

>?'

2-3 JULY «79

STATION 4
S. TRANSCCT
OAY-»-NiGHT

5 10 15 20 25

111. . . , Mil.
10 15 20 25 5 10 15 20 25

TOTAL LENGTH (MM)

,1,1

5 10 15 20 25

8|17-

SIlaki

*LSTA1

Ts. T

-19 JULY 1979
SI LAKE MICHIGAN
'LSTATION 6-9M

Ts. TRANSECT

OAY-t-NNMT

X-12 (0 0)

5 10 15 20 25

Fig. 32. Density (no./lOOO M^ plotted on log scale) of larval rainbow smelt
collected during April to September 19 79 at 6 and 9 m (all contours, depth
strata and diel periods pooled) near the Campbell Plant, eastern Lake Michigan,
Horizontal line across each bar denotes mean density while height of bar re-
presents ± 2 S.E. Midpoint of water temperature range (vertical line) at time
of collection is shown. Length-frequency histograms for all larvae collected
during each period are also shown. N » number of larvae collected, x = mean
length of larvae, S.E. given in parentheses.

115

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1980

/

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19-20 MAY

96ACH — 3 M

OCNSITY TWAJitSECT TEMP.

n NORTH

2 SOUTH

T"

1

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T'

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"3?

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L
1
1

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16-18 JUN

7

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1-2 JUL

20

• 15

• 10

UJ

q:

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Q.

2

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40 1
30
20
10 ^

19-20 k4Ar 1960
LAKE MICHIGAN
BCACH-JU
N TRANSCCr
OAY-l-NlGHr
X- 5.9 (0.1)
N- 92

2-4 JUMC 1980
LAKE MICHIGAN
BCACH-3M
H TRANSECT
DAY 1^ NIGHT
i- 5.1 (0 0)
N« I

o

40 1

il

19-20 IMT I9M 1

s

2-4 JUNE 1990

30-

LAKC MKHttAN
BCACH'JW
S TRANSECT
DAY+N1CHT

LAKE MICHIGAN
L BEACH- 3M
' S TRANSECT

DAY ANIGHT

X- 9.2 (0.1)
N« 4

X- 88 (00)
N« 1

20

10^

18-18 JUNE 1980
LAKE MICHIGAN
BEACH- 3M
N TRANSECT
OAY-I-NICHT

1-2 JULY 1980
LAKE MtCHWAN
BEACH- 3M
N TRANSECT
OAY + NK^HT
X-25 (0 0)
N« 3

f

\\

»-» JUNE M
LAMC MCMGAN
KACN-JM
$ TRANSCCT
OAY-fNIGMT
X- 7 (0.7)
N« 10

1-2 JULY 1980

LAKE MCHKAM
8eACH-3M
S. TRANSCCT
0AY4MGHT
X-23 (0.0)
N- I

5 10 15 20 5 10 15 20 25 5 10 15 20 5 10 15 20 25
TOTAL LENGTH (MM)

Fig. 34. Density (no./lOOO W plotted on log scale) of larval rainbow smelt
collected during April to September 1980 at beach -3m (all contours, depth
strata and diel periods pooled) near the Campbell Plant, eastern Lake Michigan •
Horizontal line across each bar denotes mean density while height of bar re-
presents ± 2 S.E. Midpoint of water temperature range (vertical line) at time
of collection is shown. Length-frequency histograms for all larvae collected
during each period are also shown. N =» number of larvae collected, x = mean
length of larvae, S.E. given in parentheses.

117

70 +

ro

O
O

o

<
>

<

z

10 ..

1980

6 AND 9M

DENSITY

TRANSECT TEMP.

E

NORTH

SOUTH

- 25

20 3

q:

3

•• 15

-• 10

-• 5

<

UJ
Q.

2

19-20 MAY

2-4 JUN

16-18 JUN

1-2 JUL

40
30
20-
10-

40
30
20
10-1

SI 19
« LA

i

-20 MAY 1980
LAKE MICHIGAM
STAriON 6-9M

TRANSECT
OAY+NWHT

2-4 JUNE 1980
LAKE MCHKIAN
STATIOH 6-9M
N. TRANSECT
OAY-t-NKiHT
X- « I (0 2)
M- 17

?| 16-18 JUNE 1980
;{ LAKE MICHKV^N
USTATION 6-9M
/n TRANSECT
^ OAY+NHJHT

19-20 MAY 1980

LAKE mk:hk;an

STATK}N 6-9M
S TRANSECT
DAY -•■ NIGHT
X- 8 (0 0)

5 10 15 20

5 10 15 20 25

16-18 JUNE 1980
LAKE WMCHKMN
STATKM4 S-9M
S TRANSECT
DAY+NKJHT
X- 69 (13)

s

1 1 ? JUl y t9R0

§1 LAKF MHIMIOAN

USIATION 6 9M

/ S TRANSECT

OAr fNir.HT

X=12 -i (00)

M- !

5 '10 !5 20 25

5 10 15 20
TOTAL LENGTH (MM)

Fig. 35. Density (no./lOOO W plotted on log scale) of larval rainbow smelt
collected during April to September 19 80 at 6 and 9m (all contours, depth
strata and diel periods pooled) near the Campbell Plant, eastern Lake Michigan,
Horizontal line across each bar denotes mean density while height of bar re-
presents ± 2 S.E. Midpoint of water temperature range (vertical line) at time
of collection is shown- Length-frequency histograms for all larvae collected
during each period are also shown, N = number of larvae collected, x = mean
length of larvae, S.E. given in parentheses.

118

12 ANO IS M

DENSITY

TRANSECT TEMP.

D

NORTH

1980

O
O

o

<

" 25

•• 20

•* .15

- 10

•• 5

q:

UJ

19-20 MAY

2-4 UUN

40
50
20

K 10

z

UJ

S 40
50
20
10-1

!

19-20 MAY 1980
LAKE MICHIGAN
STATION 12- ISM
N TRANSECT
DAY -»■ NIGHT
X- 6.0 (0 4)
N- 5

2-4 JUNE 1980
LAKE MICHIGAN
STATION 12- ISM
N TRANSECT
DAY ANIGHT
X- 6 (03)

19-20 MAY 1960
LAKE MICHIGAN
STATION 12-15M
S TRANSECT
DAY ■♦• NIGHT
X- 6.5 (0 0)
N- 1

16-18 JUN

16-18 JUNE 1960
LAKE MKHKMN
STATION 12 -ISM

n transect
Day>nk;ht

X- 7 7 (OS)
N- 25

1-2 JUL

u

1-2 JULY 1980
LAKE MCHK^AN
STATK)N 12-15M

n transect
oay^nk;ht

X-2S0 (0.0)
N- 1

2-4 JUNE 1960
LAKE MtCHNMN
STATION 12- ISM
S. TRANSECT
OAY^NK^HT

16-18 JUNC I960
LAKE MICHIGAN
STATKX 12- ISM
S TRANSECT
OAY+NWHT

JU

1-2 JULY -I960
LAKE MK:h»AN
STATIOM 12- ISM
S TRANSECT
OAY+NKJHT
X-2S0 (0 0)
N- I

f

5 10 15 20 5 10 15 20 25 5 10 15 20 25

TOTAL LENGTH (MM)

5 10 15 20 25

Fig. 35. Density (no./lOOO >r plotted on log scale) of larval rainbow smelt
collected during April to September 1980 at 12 and 15 m (all contours, depth
strata and diel periods pooled) near the Campbell Plant, eastern Lake Michigan.
Horizontal line across each bar denotes mean density while height of bar re-
presents ± 2 S.E. Midpoint of water temperature range (vertical line) at time
of collection is shown. Length-frequency histograms for all larvae collected
during each period are also shown. N = number of larvae collected, x = mean
length of larvae, S.E. given in parentheses.

119

1978

>»^' '~z^^z:^'~::^"~:^'^w~^

NORTH TRANSECT

,.*- v^°' ,,.^^^ v^^ ^^.z-

SAMPLING PERIOD

150 ■■

O 100 1
O

O

50-'

SOUTH TRANSECT

SAMPLING PERIOD

Fig, 37. Mean density (no./lOOO m ) of larval rainbow smelt for north
and south transect stations in Lake Michigan near the J. H, Campbell
Plant, 1978 to 1980. Mean densities were calculated by averaging
densities over all gear (plankton nets and sleds) , strata and diel
periods (day and night) sampled.

120

1979

150

I00-.

5

<, 504-

O

2

NORTH TRANSECT

SAMPLING PERIOD

SOUTH TRANSECT

SAMPLING PERIOD
Fig. 37. Continued.

121

1980

NORTH TRANSECT

SAMPLING PERIOD

150 --

-^15

\^'

SAMPLING PERIOD

SOUTH TRANSECT

NVi^

Fig. 37. Continued.

122

during June and the remainder of the summer during 1977-1980 may be related to
water temperature. Relationships between water temperature and larval density
will be discussed at the end of this section.

Table 27. Mean density of larval rainbow smelt during May-August,
1977-1980 in Lake Michigan, near the J. H. Campbell Plant, eastern Lake
Michigan.

1977

Mean Density (no./lOOO m^)

Date North and South North South

transect transect transect

17-22 June 1 1

20-28 July 2 2

1978

15-18 May 15 11 19

5-10 June 3 2 4

19-23 June k 3 6

1-3 July 9 10 9

1-2 August 1 2

1979

14-16 May 31 56 5

4-6 June 8 9 7

18-20 June kk 50 38

2-3 July 13 20 5

17-19 July 1 1

1980

19-20 May 48 83 13

2-4 June 9 13 5

16-18 June 19 23 14

1-2 July 2 3 2

During late June smelt larvae were generally more abundant in deeper
water than in shallow areas (Fig. 37). Mean density ranged from 1 to 32
larvae/1000 m^ from the beach to 3 m, 1 to 63 larvae/1000 m^ at 6 and 9 m and

123

k to 67 larvae/1000 m^ at 12 and 15 m (Figs. 27-36). As has been observed
during previous sampling periods there was little difference in size between
larvae caught in shallow and deeper water.

Three size groups of rainbow smelt larvae were observed during late June.
The first group included recently hatched larvae 4.5"7*5 'nm which were most
abundant during 18-20 June 1979 and 16-18 June I98O. During late June newly
hatched larvae appeared to be more widely dispersed in the study area than
during May. Because of relatively warm water at beach to i~m stations in
spring (Appendixes 5 and 6) » smelt eggs laid in the shallow area during April
and May probably hatched by early June. Since no smelt spawning has been
observed in the shallow area during June, newly hatched larvae collected
during late June and July (Figs. 27"36) probably originated from hatching in
deep water (6-15 ni) • Delay of hatching of smelt eggs deposited in deep water
until late June or July was probably caused by low water temperature. Bottom
temperatures at 6 to 15 m near the Campbell Plant ranged from 5*2 to 9-2 C
during I9-2O May I98O and 6.4 to 14.6 C during 1-2 June I98O. The second size
group of larvae collected during late June was comprised of larvae 8-12 mm.
Larvae in this size range were scarce during 19""23 June 1978 and 18-20 June
1979 but were relatively common during late June I98O (Figs. 27*36) • Based on
the observed growth rate of the first cohort collected during the first few
weeks of life, larvae 8-12 mm collected during late June probably hatched
around early June. Larger larvae 12.5*20 mm were undoubtedly members of the
first cohort which hatched during May and were approximately 1-mo old by late
June. Mean lengths of this cohort during late June 1978, 1979 and I98O were
17-5» 15*7 and 16. mm respectively. Bigelow and Schroeder (I963) reported a
slightly larger size (17 to I8 mm) for 1-mo-old smelt larvae in the Atlantic
coastal drainage. Members of the first cohort were the most abundant size
group during 18-20 June 1979» They were scarce during late June in 1977» 1978
and 1980. Based on larval density observed during May (Table 27) smelt larvae
in the first I98O cohort were relatively abundant. The reason for the low
catches of larvae in this cohort during late June 198O was probably their
widespread distribution.

July — Mean density of smelt larvae during early July declined
substantially from levels observed during late June (Table 27). This decline
was probably due to dispersal of smelt larvae hatched during May and June and
scarcity of newly hatched larvae during early July. During 1978, however,
mean density of smelt larvae during I-3 July was higher than that observed
during 19*23 June. Reasons for this increase are not known. During early
July larval densities in shallow and deep water were in general similar
(Figs. 28-36) .

Rainbow smelt larvae collected during early July ranged from 4.1 to 24 mm
and may be subdivided into three size groups. Few newly hatched larvae
4.1-7-5 nini were found in 1978 and 1979* The second group consisted of larvae
8-17 ninft which probably hatched from early to late June. Larvae in this size
range were more common during I-3 July 1978 than the early July sampling
period in 1977» 1979 and I98O. The third group was comprised of larvae 18-25
mm which were members of the cohort that hatched during May. The latter size
group occurred most commonly during I-3 July 1979*

124

Small numbers of YOY smelt 26-28.5 mm, which were undoubtedly members of
the first cohort, were caught in plankton nets and sleds during 1-2 July I98O
(Appendix 11). YOY smelt > 25.4 mm were not caught during early July larvae
sampling in 1977, 1978 and 1979-

Smelt larvae were relatively scarce during late July (Fig. 37). They
were caught in low numbers during 19-23 July 1977 and 17"19 July 1979
(Figs. 27, 31-33). None were found during late July 1978 and 1980. As was
found during June and early July, smelt larvae were widely dispersed in the
study area during late July. Smelt larvae collected during late July ranged
from 12 to 25 mm (Figs. 27, 31-33). A newly hatched larva h.] mm TL was also
observed during 17"19 July 1979-

Smelt fry 27-^0 mm were commonly caught in plankton nets and sleds during
late July from 1977 to I98O (Appendixes 11, 39, kO and 41). Smelt fry were
found in shallow and deep water at both transects. They were undoubtedly
members of the cohort that hatched during May and were approximately 2-mo old
by late July. Size range of fry collected during late July was comparable to
lengths of 27-34 mm reported for 2-mo-o1d smelt YOY (Bigelow and Schroeder
1963).

August and Septembei — Smelt larvae were scarce during August. A few
larvae 15"25 mm were caught during early and late August 1978 and early August

1979. Smelt larvae have never been caught during September, except for a I5-
mm larva collected during 21-23 September 1977 (Fig. 27). Smelt fry 26-45 mm
continued to increase in density in our study area during early August and
reached a peak during late August. Smelt fry occurred from 1 to 15 ni. High
abundance of smelt fry was commonly observed in plankton nets and sleds towed
at 1.5 and 3 m (Appendixes 10, 39, 40 and 41). These data suggested that YOY
smelt, which were widely dispersed from May to July, began to congregate
inside the 15"ni contour during August. In eastern Lake Michigan, near
Ludington, most YOY smelt collected in nets during August occurred at 1 .5 and
3 m (Liston et al. I98I) . During September smelt fry were scarce in plankton
nets and larval sleds (Appendix 11).

During June and July distribution of smelt larvae appeared to be related
to water temperature. Smelt larvae tended to be most common at moderately
high temperatures. High catches of smelt larvae were observed during late
June 1979 and late June I98O at water temperatures of 13 to I5 C (Figs. 22,
31-36). These data agreed with Jude et al. (1979b) who found most YOY smelt
in water temperatures of 13-14 C. Smelt larvae appeared to avoid high
temperatures (16-24 C) which were observed during June 1978 and early July

1980. Smelt larvae were also scarce during sharp drops in temperature due to
upwelling of very cold water. Only low densities of larvae were observed
during early and late July 1979 when water temperatures ranged from 4 to 12 C.

125

Young-of -the- Year--

Seasonal di str ibution —

July — YOY smelt 29"^0 mm first entered trawl catches during July.
Catches of YOY during July were relatively low, ranging from 1 during July
1978 to 3^1 during July 1977- Scarcity of smelt YOY during July may be due to
their widespread distribution in the inshore area as has been observed during
fish larvae sampling. In addition, YOY smelt generally live in the upper
levels of the water column until late summer (Wells I968) and were therefore
only partially vulnerable to bottom trawls during July. During July, YOY were
found mostly at 6 and 9 ni; a few YOY also occurred at beach, 3f 12 and 15 m
(Fig. 38) .

August — During the i*-yr period catches of YOY smelt 26-5^ nim peaked in
August. In southeastern Lake Michigan high catches of YOY were also observed
during August (Jude et al. 1979b). As has been found during fish larvae
sampling, YOY smelt began to concentrate in the inshore area during August.
Crestin (1973) reported YOY migrate to the bottom as they grow older. In
eastern Lake Michigan YOY smelt move to the bottom by late summer or during
the fall (Wells I968) . High catches of YOY smelt in bottom trawls during
August indicated that migration to the bottom started during this month in the
vicinity of the Campbell Plant.

Small numbers of YOY smelt occurred in beach seines during August
(Appendixes 8, 3^"32) . August trawl catches showed that YOY were less
abundant at 3 ni than at deeper water stations (Fig. 38). Mean catches of YOY
smelt per trawl haul at 3 ni ranged from 8 to 80 during August 1977"1980.
Plankton net and sled tows however, sometimes captured YOY smelt (>25.^ mm) in
relatively high densities at 1.5 and 3 ^* During August 1977 and 1979 YOY
smelt were most abundant at 12 and 15 m (Fig. 38). Mean catches per trawl haul
at these depths were 512 and 1250 YOY during August 1977 and August 1979
respectively. During August 1978 and I98O YOY were most common at 6 and 9 n^-
Mean catches at 6 and 9 ^ during these two sampling periods were 437 and 1750
YOY per trawl haul respectively.

Abundance of YOY smelt in the study area may be in part related to water
temperature. Low catches of YOY in the shallow water may be due to relatively
high temperatures (15«8-25*7 C) observed from the beach to 3 ni during August
trawling (Appendixes k, 18-20). YOY smelt tended to occur in moderately warm
water during August. Highest catches of YOY during August 1977 and 1979
occurred at mean bottom temperatures of 14.6 and 14.0 C respectively. During
August 1978 and I98O YOY were most common at mean bottom temperatures of 19-5
and 15*5 C respectively. In southeastern Lake Michigan, Jude et al . (1979b)
found YOY over a wide range of temperatures (11-19 C) ,with highest catches
observed at 13-14 C. Smelt YOY in Lake Erie were reported to inhabit the
thermocline during the summer (MacCallum and Regier 1970). High catches of
YOY during August 1977"1980 in the study area were also generally observed
near the thermocline (Figs. 22 and 38).

126

During the 4-yr period YOY catches appeared to be increasing. Catches
per trawl haul during August were 330, l83, 703 and 638 YOY from 1977 to igSO
respectively. YOY smelt were substantially more abundant in 1979 and I98O
than during the previous 2 yr. Discussion of the increased smelt abundance
will be presented at the end of the adult section.

During August YOY smelt collected in trawls ranged from 30 to 5^ nfim.
Kendall (1927) reported a similar size range (31"51 ^^) ^or 3-mo-old smelt in
Maine lakes. Most fish we collected ranged from 35 to kk mm with an interval
midpoint of kO mm (Appendixes 8, 30, 31 and 32). During August 1977-1980 YOY
in the 40-mm length interval made up 63 to 82% of the total YOY smelt
collected. YOY < 35 mm represented I3 to 20% of the total YOY catches, while
YOY > kk mm accounted for only 0.1 to 7%-

September — Catches of YOY in September declined substantially from the
levels observed during August probably as a result of YOY migration to deeper
water. In Lake Erie, MacCallum and Regier (1970) found YOY smelt with
yearlings and adults at 2^-27 m in September. Jude et al . (1979b) also
observed a YOY smelt catch decline during September in inshore southeastern
Lake Michigan.

As was observed during August, YOY were scarce in shallow areas due to
warm water (Fig. 22). During September I98O appreciable numbers of YOY were
collected in the beach zone because of relatively cool water (16. 5 C) during
sampling. During September high catches tended to occur in colder water than
in August. During September 1977f ^979 and I98O, YOY were most common at 12
and 15 m at mean bottom temperatures ranging from 6.3 to 10. 5 C (Fig. 22).
Many YOY were also found at 6 and 9 ^ during September during these 3 yr
because of relatively cold water (7.1-12.6 C) at these depths (Fig. 22).
During September in Lake Michigan Brandt et al. (I98O) found most YOY smelt at
5-6 C at night and at 13"!^ C during the day. During September I978 YOY
appeared to avoid the 6- and 9'"ni contours because of warm water (mean bottom
temperature I8.7 C) . Substantial quantities of YOY were, however, collected
during September 1978 at 12 and 15 ni where mean bottom temperature was I6.6 C.

Catches of YOY smelt during September over the k-yr period were less
variable than was observed during August. Mean catches per trawl haul in
September ranged from 78 to 126 during the 4-yr period. Differences in YOY
catches may be related to water temperature. Low catches of YOY during
September 1978 (78 YOY/trawl haul) resulted from water temperatures which were
too high, while high catches observed during September 1977 (112 YOY/trawl
haul) and 1979 (126 YOY/trawl haul) coincided with periods of cold-water
upwel lings (Fig. 22). During September I98O, water temperature was relatively
high (16.9 C at 6 and 9 ^) on the north transect and relatively low (12.1 C at
6 and 9 m) on the south transect. A mean catch of 99 YOY per trawl haul was
found during the sampling period. During September YOY smelt ranged from 30
to 64 mm. As was found during August the major portion of YOY were 35'kk mm.

October, November and Decembei — YOY smelt in appreciable numbers were
caught from October to December during the k yr suggesting that one portion of
the YOY population continued to inhabit inshore waters until the end of the

127

<
o

o

o

-J

X
CO

o

UJ
CD

2
3

1x10^
1x10^
1x10'
1x10'
1x10^
1x10^
1x10'

1x10'
1x10^
1x10=

1x10'

1x10'
1x10'
1x10=
1x10'
1x10'
1x10=
1x10=
1x10'

1x10'
1x10'
1x10=
1x10' —

YL

AD

-3r

NORTH TRANSECT
1977

^ YOY

YL

AD-|

\m yoy4-

•YL

^- YOY

r " 'I
YL

AD«

I Ij I! . I! l ,i .i .i ■

„ ^1— YOY-4-

' YOY

YL

YOY

YL

JUN

JUL

AUG

SEP

OCT

NOV

DEC

20 40 60 80 100 120 140 16G '80 200 220 240 260 280 300 320
TOTAL LENGTH (MM)

Fig. 38.. Length-frequency histograms for rainbow smelt collected during
Jxjne - December 1977 and April - December 1978-1980 at north and south
transects. Stations were combined into two groups for the north transect:
beach and 3 m; 6 and 9 m and into three groups for the south transect:
beach, 1.5 and 3 m; 6 and 9 m; and 12 and 15 m. Diel periods and gear
types were pooled. YOY = Young-of-the-year; YL = Yearling; AD = Adult.

128

YL

lo-3n l5-9n i:2-i5n

I X ] G'
1x10*
IxiO'
1x10'-
1x10' ■

1x10*-

^ 1x10' •

^ 1x10'-
o

CO

1x10' —

o
2" 1x10*"

o

^ 1x10'-

I 1x10'-

1x10' -
u.

® 1x10*^

UJ

m

1x10'-

IxlG' —

1x10'

1x10*-

1x10'-

1x10'-

1x10' -

1x10*-
1x10'-
1x10'-
1x13' -

Fig,

SOUTH TRANSECT
1977

I !• I< I

HyoyH

AD'

.YOYi

A0<

H YOY

YL

AD

•YOY

YL-

YOY

YL-

' YOY

AOH

-F

JUL

AUG

SEP

OCT

NOV

20 40 60

"^ 1 1 T 1 , 1 1 I J r— r— ■

80 100 120 140 :60 180 200 220 240 260 280 300
TOTAL LENGTH (MM)

DEC

320

38.

Continued .

129

1x10'
1x10' — I-

YL

AD-

1x10*-
1x10'-
1x10'-
1x10' -

lc-3n !6-9n
NORTH TRANSECT
1978

li !

\ I

flPR

h

-YL

1x10*
1x10' -f
1x10'— [-
1x10' -^

_Li

,1 I I, u,

AD

hiL

n 1 r-

MflY

YL ■

-=^ AO-H

1x10* =

1x10'-

5 1x10'-
<

en 1x10' —

§ 1x10*

-T 1 1 r-

~T 1 1

JUN

YL

AO'

i 1x10'-

1x10' -

1x10* =r ^

S 1x10'

I 1x10' —

1x10' —
1x10* =h

T 1* r

YL

AD-I

-T 1 ! r

JUL

5 u.n.\ h^OY.

' i' ' I' ■ I ^ r

n 1 \ r

RUG

.YL

1x10'
1x10' —
1x10' —

AO

1x10' —

1x10'

1x10'

1x10* =r 1 V

1 1 \ r~

YOY YL

SEP

! AD— I

-T 1 r

-1^

YOY

T I 1 1 ( 1 -p.

YL , - AD-f

OCT

1x10^=4= — ^ ^

1x10' —
1x10'-
1x10' —

-YOY

-T r-

YL '

! • ■ 1 1 1 1 r

NOV

20 40 60 80 IOC 120 140 160 180 200 220 240 260 280 300 320
TOTAL L ENGTH (MM)

Fig. 38. Continued.

lEC

^^Q^-r-

ixlC
ixlQ*

C-3n l5-9ri

:!2-]5n

AD

Ui-ML.

SOUTH TRANSECT
1978

AO

i: ,1 |i: I

[LULJiL

YL

AO-

-RPR

nflY

<

CO

o
o

ixlG*

1x10^

1x10'

IxiG'

1x10* =F

2 lx,0'4

IxlC •
1x10*-

1x10*

1x10'

T

1x10*
1x10'
1x*Q'
1x10'

1x10*
1x10'
1x10'

1x10'

1x10*

1x10'

1x10'- —
1x10'

^YOY

YL

A0<

|. YOY

YL

A0«

I— YOY

YL-

' !■ ■■ ' I

►YOY

YL

AD— I

■ t

YOY

YL-

►AD-

jJi

YOY

YL I AD^

-F

20 40 60 80
Fig. 38 . Contmuea.

JUN

JUL

AUG

SEP

OCT

NOV

DEC

00 120 140 ^50 '80 2G0 220 240 260 260 3CC
TOTAL LENGTH (MM)

320

131

^•c= —

>YL

AD '

YL

li .,! ! ,i li .,!■.■

YL— ' AD— i

IL-:; ic-

NORTH TRANSECT
1979

-n ' — ^ \ \ 1 r-

--. AD

-T 1* r— — T \ \ I

IflY

III!
I I I I
I ,' « '

YL-

AD«

CO

S
o
o

X
CO

UJ
CD

2
3

1x10' -|-

-T 1 — "'-T

IxiQ' —

IxiG'

IxlQ'

|.YOY

Jl.

YL

AD-

IX /u
lx;C'

— r r

YOY

M l« . ^

T — »— T r \ 1 1 r-

— YL-

AD<

Ix'O^-
IxlG'-

;x]Q' -

Ix'C*-
■xiG'-
:xlG^-
Ix'G' -

lX:G*-

Ix'G'-

I— YOY— 4-

— YL

AD'

I I I
I I I
I I I

n TT-^ — r — — r

-I* 1* 1 1 1 r

YOY

— YL-

YOY I

— I r

YL 1

1 I

-I 1 r

JUN

-T* \ 1 1 \ \ \ 1

G 20 40 60 80 lOO 120 ^40 160 :8C 200 220 240 260 28C
TOTAl LENGTH (MM)

Fig. 38. Continued.

132

JUL

AUG

SEP

OCT

— YL

YL

AO

L

;2-;3^

SOUTH TRANSECT
1979

^-PR

AO

1x10*

II h: li: I. Ii.

YL

AO— I

HRy

IxlC -^

<

o

CO

iX IL

o

o

iv'n*

o

^

Ix .u

z

en

1x:g^

u.

1x1,"

u.

o

IxlC*

(T

UJ

1v 1^'

ffi

IX iL

25

IxlC'

z

'^

-t

IXid^

1x10'
^xlO'

1x10*
1x10' —

1x10'

1x10'

a-

•: •:

JUN

JiYOY

YL

AO-

JlLl

: Ir ■!■ ■;■ Ir \f- li- I, i

-

ii
i:

!•

i:
1-
i:
i:
1-
i:
i:

!•

li

1;

1-

i:

I: 1

i: 1
1- 1
i: 1
• : 1

!• 1

¥-^

OY

III

- Y

L

i
1

u

Ao•^

r ''• 'r ■ ■ • t

YOY

YL -

1

1
1. 1

i: 1
li 1

1
1

1
1
1

1
1

-4.

• ••* : i .: 1
: •: |i: i: i: i

- AO-

I- I- ll

YOY

YL

AO

jUOLJiU

JUL

flUG

SEP

OCT

YOY

- YL

NOV

YOY

YL

Fig.

-^

20 40

38

?Q

lOO i2Q UO :6C 180 200 220 240 260 280 300 320
TOTAL LENGTH (MM)

Continued

JbL

133

:x]0'

ixlQ^
1x10'

IxIC

"xlG^

:xiO^

1x^0

x^G'

1x10=

5 1x10=

d" 1x10'
o

^ 1x10^

w 1x10=
u.

1x10'
u.

® 1x10'

(T

ui 1x10=

CD

i 1x10=
z

:x10'
'xlO'
1x10^
1x10=
1x10'

1x10'
1x10=
1x10=
blO'

1x10'
1x10=
1x10=
1x10'

NORTH TRANSECT
1980

lQ-3r ;6-9n

YL

AD

YL

AD

-] ' '!' " T " 'I'

— YL '

1 ! r

AD-

I- YOY'

YL.

n — ■ — r 1 r

.YOY^

YL

1 I

AD-

n 1 r

-I 1 r

I— YOY

YL

- AD

■YOY +

'YL

_, — . — J. ji_

AD I

n 1 ' " ' r

I— YOY

III!

YL 1 AD —I

T — — r
YOY

-^ — . — , , ^

YL

AD— I

PPR

HflY

"T ■ T 1 1 1 \ 1

JUN

JUL

AUG

SEP

OCT

NOV

20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320

DEC

Fig. 38. Continued.

TOTAL LENGTH (MM)

13^

SOUTH TRANSECT
980

APR

nflY

JUN

JUL

flUG

SEP

20 40 60 80 100 120 140 160 ^80 200 220 240 260 280 300 320
TOTAL LENGTH (MM)

Fig.

38

Continued.

135

year. During fall, YOY may be found from the beach to 15 m. Only a small
number of YOY occurred in the shallow area {beach-3 m) , except during October
1980, when substantial numbers of YOY were caught from the beach to 3 ni
(Fig. 38). Most YOY were found at 6 to 15 m during fall.

Abundance of YOY smelt during fall varied considerably. Catches per
trawl haul ranged from 3 to kO YOY during October, November and December over
the k-yr period. During I978 and 1979 highest monthly catches in the fall
occurred in November in water temperatures of 6.5 to 13*2 C (Fig. 22). During
fall 1980 catches of YOY were highest during October in water temperatures of
7.3-12.0 C. YOY were still common inshore during December when water
temperatures ranged from 0.5 to 5.3 C. During 1977 highest fall catches were
observed during December. These data indicated that YOY tolerate a wide range
of water temperatures.

Smelt YOY reached a modal length of 50 mm in October and 60 mm in

December. Since modal length of YOY was estimated at 40 mm during August,

growth rate of YOY was approximately 5 ^^ P^f month (O.I6 mm/day) from August
to December .

Year 1 ings —

Seasonal distr ibution —

April — Yearling smelt live in deep water during winter and migrate
inshore during spring. During April yearlings were found at all depths in the
study area. Few yearlings occurred in shallow water (beach-3 m) • They were
most common at 6 and 9 m during April I978 and were evenly distributed from 6
to 15 m during April 1979 and I98O (Fig. 38). Catches of yearlings per trawl
haul during ApriT ranged from 10 to 64 during 1978-1980. High catches during
April 1980 (64/trawl haul) were probably related to relatively warm water
(3.8-12.0 C) in the study area. Cold water (1.5-10 C) probably delayed the
inshore migration of yearlings during April 1979- Only 10 yearlings were
caught per trawl haul during April 1979- During April, yearling smelt ranged
from kO to 100 mm. Modal length of yearlings in April (60 mm) was the same as
the modal length of YOY observed during December.

May — Catches of yearlings increased dramatically during May. More
yearlings were found in shallow water (beach-3 m) during May than during
April. During May 1979 higher catches of yearlings were found from the beach
zone to 3 m than at 6 and 9 m, or at 12 and 15 m. Most yearlings occurred at
12 and 15 m during May 1978 and I98O (Fig. 38). Mean catches of yearlings per
trawl haul during May were from 112 to 132 individuals during 1978-1980. This
large influx of yearlings to the inshore area was caused by increased water
temperature in the spring. Mean bottom water temperatures during May ranged
from 6.2 to I3.8 C (Fig. 22). Unlike other monthly catches, yearling catch
during May varied only slightly over the 3""yr period.

June — Catches of yearlings in the study area generally declined during
June due to warming of inshore water (Fig. 38). June catches varied
considerably over the 4-yr period. During 1977-1980 catches of yearlings per

136

trawl haul during June ranged from 7 to 112 individuals. Scarcity of
yearlings during June 1979 (7 yearlings/trawl haul) was probably caused by the
unusually warm water (7.5-17.0 C) observed during this sampling period. Low
catches during June 1977 (36 yearlings/trawl haul) probably resulted from
relatively low temperatures which ranged from 5 to 11.7 C from 6 to 15 ni.
High catches (119 yearlings/trawl haul) were observed during June 1980 in
water temperatures ranging from 7.3 to 13*2 C at depths of 6 to 15 m. During
June 1978 water temperature was relatively higher at the south transect than
at the north transect (Fig. 22). Mean catch of yearlings collected per trawl
haul was approximately 87 during June in our study area.

Yearlings were scarce in shallow water (beach-3 ^) during June and the
remainder of the year indicating that smelt in this size group remain in the
shallow area only briefly during hay. During June 1977 and 1978 highest
catches of yearlings were found at 6 and 9 m, while during 1979 and I98O
yearlings were most common at 12 and I5 m.

July-December — Most yearlings probably live in deep water during the
summer. In July large numbers of yearlings sometimes followed upwel lings to
the inshore area. High catches of yearlings observed during July 1978 and
July 1979 (Fig. 38) occurred in relatively cold water. Mean water
temperatures from 6 to 15 m ranged from S.k to 11. 3 C in 1978 and from 5.3 to
9.3 C in 1979 (Fig. 22). During July I98O yearlings were scarce because of
excessively high water temperature (mean temperatures were I8 to 21 C from 6
to 15 m) . During July 1977 however, despite a cold-water upwelling (Fig. 22),
catches of yearlings were relatively low (Fig. 38).

Yearling catches in the study area continued to decline during August and
September. Catches of yearlings per trawl haul ranged from 7 to 36
individuals during these 2 mo. High catches were generally found in cool
water (Figs. 22,38). Unlike June and July results, however, few yearlings
fol lowed cold-water upwel lings to the inshore area. Low temperatures were
observed during August I98O and during September 1977 and 1979 (Fig. 22), but
only relatively low catches of yearlings were obtained during these sampling
periods (Fig. 38). As has been indicated, yearlings were scarce in the
shallow area. Most were caught from 6 to 15 m during July, August and
September. Yearlings were scarce during fall. Small numbers of yearlings
were found during October, November and December I98O. During fall 1977-1979
yearlings were almost absent from the study area.

Adults —

Seasonal di str i but ion —

April — Adult smelt migrate inshore to spawn during spring. In Lake
Michigan spawning takes place mostly during April and May (Daly and Wiegert
1958; Van Oosten 19^0). In the study area the spawning run probably started
around mid-April during I978-I98O. No adults with spent gonads were caught
during 15-17 April 1979 and only a few adults with spent gonads were collected
during 23-27 April 1978 and 21-29 April 198O (Fig. 39). Daly anc Wiegert
(1958) reported smelt spawning starts only when water temperature increases to

137

above 4.5 C during spring. Spawning reached a peak at a water temperature of
10 C (Euers I96O; Jude et al. 1975)- Near Ludington, Michigan, smelt spawning
takes place at water temperatures of 5"7 C (Liston et al. I98O) . In the study
area ripe-running and spent adults were observed in water temperatures of k to
7.8 C during April 1978 and I98O suggesting that spawning occurred at this
temperature range. High catches of adults with ripe-running and spent gonads
during late April I978 and 1979 (Fig* 39) suggested peak spawning of smelt in
the study area takes place around the end of April e

Rainbow smelt generally spawn in shallow water (Jude et al. 1979b; Rupp
1959; Van Oosten 19^0). Adults with well developed, ripe-running and spent
gonads were abundant from the beach zone to 3 "^ during April suggesting
spawning took place at these depths. Largest catches during April, however,
were observed at 6 and 9 ni. A few adults in spawning condition also occurred
at 12 and 15 m. Although rainbow smelt also migrate upstream to spawn, no
spawning run was observed in Pigeon Lake or Pigeon River during I978-I98O. No
spawning was found in Little Pigeon Creek, a small tributary to Lake Michigan
approximately 6 km north of the Campbell Plant. These data indicated that in
the vicinity of the Campbell Plant smelt spawning takes place mostly in Lake
Michigan.

May — Adult smelt move offshore soon after spawning. Wells (I968) found
most adult smelt at 27 m by 5 Way and at 36 m by the end of May in eastern
Lake Michigan off Saugatuck, Michigan. In Lake Erie, Ferguson (I965) recorded
increasing catches of adult smelt in deep water during May. In our study area
catches of adult smelt were lower during May than during April I978 and I98O
(Fig. 38). In 1979» however, adult catches were higher during May than during
April because April sampling was conducted before the major spawning run of
smel t.

Spawning was still in progress during May during I978-198O as some smelt
with ripe-running and well developed gonads were found in May catches. Most
adult smelt collected during May, however, showed spent gonads (Fig. 39),
suggesting that the spawning peak was over before mid-May.

As was observed during April, in May adults were caught from the beach
zone to 15 m. During 1978, approximately the same number of adults were
collected in shallow water (beach and 3 m) and at 6 and 9m. A few adults
were found at 12 and 15 m. Adults were most common at 6 and 9 m during May
1979 and at 12 and I5 m during May 198O. Occurrence of large numbers of
adults with ripe-running and spent gonads from 6 to 15 nft, also observed during
April, suggested that some spawning takes place at these depths. Smelt
spawning was reported to occur in water 9 to 12 m in Lake Heney, Gatineau
County, Quebec (Legault and Del isle I968) and in water 9 to 22 m in Lake Erie
(MacCallum and Regier 1970). Because water temperature was generally lower in
deep water (Fig. 22), incubation of eggs deposited in deep water was slower
than eggs spawned in shallow water. Capture of newly hatched larvae during
late June and early July (see RESULTS AND DISCUSSION, Rainbow Smelt , Larvae)
substantiated spawning in deep water.

138

50

300

Q
UJ

H 250-

O

O
O

CO
UJ

tr

3

200-

150

100

50

Ll.
O

50

tr

UJ

150

3

100

50

NO

Ns356

N«t2

Ns229

NO

N«203

N*89

N>II8

APR MAY

N«89

N«4

1977

■ »WELL DEVELOPED AND
RIPE-RUNNING GONADS

n^SPENT GONADS

Ns24 N03

N:I44

1978

M.I93 N.ST

n N'^'

1979

N«79 N««76 N«35l

1980

Ns2

N>I8

N«I8

[^ N.O N.I2S ^*« 'J^I^

JUN JUL AUG SEP OCT

SAMPLING PERIOD

NsO

N«I7

N«0

N«28

N«I8

Nsi4

NOV DEC

Fig. 39. Number of mature rainbow smelt with well developed, ripe-running
and spent gonads collected monthly during June-December 1977 and April-
December 1978-1980 near the J. H. Campbell Plant, eastern Lake Michigan.
N = total number of mature rainbow smelt caught per month.

139

June-December — Most adults probably live in deep water during June.
Adult smelt were scarce and were found only from 6 to 15 ni during this month.
No adults with ripe-running or well developed gonads were collected. A few
adults collected in June showed spent gonads. Adults moved offshore probably
because of the warming of inshore water. They were never observed in the
study area in large numbers during June even during cold-water upwel lings
which occurred during June 1977 and I98O (Fig. 22).

Catches of adults varied considerably during July, August and September
(Fig. 37). Unlike June findings, adults often followed the upwel ling of cold
water to the inshore area during these 3 nio. Relatively high catches of
adults were observed during upwel lings of cold water as was found during July
1978, August and September 1979 and I98O, and September 1977 (Figs. 38,22).
During I978 substantial catches of adults were observed during July when mean
bottom temperature ranged from 7*6 to 12.2 C (Fig. 22). During 1979 high
catches of adults occurred during August and September. Mean bottom
temperatures from 6 to 15 m were 14 to 14.9 C during August and from 10. 5 to
13.0 C during September. In 1977 adults were common during September when
mean bottom temperatures were 6.5 to 10.0 C from the beach zone to I5 ^*
Although water temperature was relatively high (Fig. 22), adults were also
caught in substantial numbers during August and September I98O (Fig. 38).
Adults were scarce in the study area during fall. No adults were caught
during October, November or December 1977* A few adults were collected during
fall 1978-1980.

Smelt populations in the study area appeared to increase during the
period 1977-1980 (Table 28). During 1977 yearling and adult catches were
substantially lower than in other years due to the lack of sampling during
April and May, times when two size groups were most abundant. Adult catches
were relatively low and did not vary greatly during I978-I98O. Low catches of
adults during 1979 were due to a poor spawning run during the April and May
sampling periods. Yearling catches fluctuated widely during 1977*1980 (Table
28). High catches of yearlings observed during I978 may have resulted from a
strong year class and from favorable temperatures in i nshore water . The
increasing abundance of YOY during I977-I98O made up the major portion of the
increase in total catches of rainbow smelt.

Plant Effects —

During May and June 1978 mean densities of smelt larvae were slightly
higher at the south reference than the north transect. During early July and
early August 1978, however, smelt larvae appeared to be more common on the
north than the south transect (Table 27). The Wilcoxon signed ranks test (a
= 0.05) showed no significant difference in larval smelt densities between
the north and south transects during 1978.

During 1979 smelt larvae were more abundant at the north than the south
reference transect during all sampling periods (Table 27» Wilcoxon signed
ranks test, a= O.O5) . This difference resulted mainly from the high catches
of larvae at the north transect during May and late June (Table 27). As was
found during 1979, larval densities were significantly higher at the north

lifO

Table 28. Number of rainbow smelt caught by all gear types
during June-December 1977 and Apr i 1 -December I978-I98O.

Year

Life stages

320

n55

987

1369

lit52

lit368

6271

i»285

11131

9838

22770

26043

1977 1978 1979 1980

Adults
Year 1 i ngs
YOY

Total 12903 25351 29028 36697

than the south transect during I98O (a* 0.05. Wilcoxon signed ranks test).
Smelt larvae were more abundant at the north transect during all sampling
periods in I98O. Largest difference in mean densities between the two
transects, however » was observed during May.

Higher catches of smelt larvae at the north transect than at the south
reference transect during 1979 and I98O may be related to the construction of
offshore intake and discharge structures for Unit 3* During 1979 and I98O
rock riprap made of 10- to 20-cm diameter rubble was laid on the bottom from
shore to 11 m to cover the underground pipelines. More adult rainbow smelt
may spawn on this rubble than on the sandy bottom. Smelt eggs laid on rocky
substrate have a survival rate 10 times greater than those laid on sand
because sand has a grinding effect on eggs under the influence of the surf
(Rupp 1965)- Higher larval density at the north transect may in part be due
to a higher survival rate experienced by smelt eggs laid on rocky substrate.
Bottom dredging and the rocky riprap may cause an increased food supply for
smelt larvae at the north transect during 1979"1980.

Catches of smelt in trawls at the reference station (6 m, south) and the
plant transect station (6 m north) were not significantly different during

1977 (Judeetal. 1978). The ANOVA results for trawl data for 1977-1980
showed that the STATION and AREA effects were highly significant (Tables 29
and 30). Geometric mean abundances of smelt at 6 and 9 ^ were significantly
higher at the plant transect than at the reference transect. While during

1978 geometric mean catches were only slightly higher at the plant transect
than at the reference transect, substantially higher catches were observed at
the plant transect than at the reference transect during 1979 and I98O
(Fig. 40). Trawl catches included mostly YOY and yearlings. Adult smelt were
generally caught in low numbers in trawls. Higher catches of rainbow smelt at
the north transect during 1979 and I98O resulted mainly from greater abundance

141

of YOY and yearlings in this part of the study area. Preparation of the
bottom for construction of the intake and discharge structures may have caused
an increased food supply which attracted yearlings and YOY to the north
transect. During spring more yearlings were caught at the reference transect.

Table 29. Analysis of variance summary for rainbow smelt caught in
trawls at stations C (6 m, south) and L (6 m, north) near the J. H.
Campbell Plant, eastern Lake Michigan, 1977 through 1980. Data for
June through December were analyzed.

Attained

Source

of

significance

variation

df

Mean square

F-statistic

level

Year

3

0.1351

1.0336

0.3806

Month

6

6.28U8

48.0957

<0.0001**

Station

1

1.5421

11.8014

0.0008**

Time

1

7.0490

53.9445

<0.0001*«

Y X M

18

2.7432

20.9928

<0.0001**

Y X S

3

0.1163

0.9055

0.4409

M X S

6

0.1655

1.2668

0.2784

Y X I

3

0.3292

2.5194

0.0616

M X I

6

0.7237

5.5379

<0.0001««

S X I

1

0.1700

1.3007

0.2565

Y X M X

S

18

0.2116

1.6190

0.0669

Y X M X

T

18

0.4774

3.6532

<0.0001*«

Y X S X

T

3

0.3999

3.0607

0.0312

M X S X

T

6

0.1572

1.2028

0.3101

Y X M X

S X T

18

0.2181

1.6693

0.0554

Within cell

error

112

0.1307

«* Highly significant (P < 0.001) .
« Significant (P < O.Ol) .

Spottai ] Shiner

I ntroduction —

Spottai 1 shiners are benthic minnows of shallow areas of large lakes and
rivers. They are found in all the Great Lakes and are abundant in Green Bay
and the southeastern region of Lake Michigan (Wells and House 197^)
study found them to be very abundant in the vicinity of the
Plant during preoperational study years. Numerically they were
abundant fish in 1977-1980 comprising 10, 14, 12 and l8% of the
1977, 1978, 1979 and I98O respectively (Table 10).

This
J. H. Campbel I
the third-most
total catch in

Spottai 1 shiners were collected in all months that sampling was
performed. Typically spottai Is began a shoreward migration in April and May,
which was complete by June. Spawning occurred in June and July and was
usually completed by early August. During spawning fish were concentrated in
the beach zone; when water temperatures were warm enough (> 15«0 C) they were

142

Table 30. Analysis of variance summary for rainbow smelt caught in
trawls at stations C (6 m, south), D (9 m, south), L (6 m, north) and N
(9 m, north) near the J. H. Campbell Plant, eastern Lake Michigan, 1978
through 1980. Data for May through December were analyzed.

Attained

Source

of

significance

variation

df

Mean square

F-statistlc

level

Year

2

2.2289

16.6865

<0.0001««

Month

7

7.5611

56.6052

<0.0001««

Area

1

2.3919

17.9065

<0.0001*«

Depth

1

3.1837

23.8346

<0.0001*«

line

1

3.2010

23.9639

<0. 0001*4

Y X H

in

4.6116

34.5246

<0.0001«*

Y X A

2

0.2093

1.5668

0.2114

M X A

7

0.4339

3.2481

0.0028*

Y X D

2

0.9564

7.1598

0.0010*

M X D

7

0.4726

3.5377

0.0013*

A X D

1

0.4170

3.1217

0.0788

Y X T

2

0.5750

4.3050

0.0148

M X T

7

1.4513

10.8649

<0,0001**

A X T

1

0.0067

0.0503

0.8228

D X T

1

3.4375

26.1089

<0.0001*«

Y X M

X

A

14

0.7281

5.4506

<0.0001**

Y X M

X

C

1*.

0.5299

3.9671

<0.0001*«

Y X A

X

D

2

0.3804

2.8476

0.0604

M X A

X

D

7

0.2327

1.7417

0.1014

Y X M

X

I

14

1.0962

8.2068

<0.0001**

Y X A

X

T

2

0.4926

3.6879

0.0268

M X A

X

T

7

0.2601

1.9474

0.0643

Y X D

X

T

2

0.7006

5.2450

0.0061*

H X D

X

T

7

0.3210

2.4033

0.0222

A X D

X

T

1

0.1684

1.2609

0.2629

Y X H

X

A X

D

14

0.1406

1.0527

0.4033

Y X M

X

A X

I

14

0.3623

2.7126

0.0012*

Y X M

X

D X

T

14

0.1647

1.2331

0.2540

Y X A

X

D X

I

2

0.2216

1.6589

0.1931

M X A

X

L X

r

7

0.0850

0.6363

0.7255

Y X M

X

A X

D X T

14

0.0885

0.6624

0.8089

Withlr

1 cell

error

— *■ — — — ^ —

192

0.1336

** Highly significant (P < 0.001).
* Significant (P < 0.01) .

found out to 6 m. Peak numbers of adult spottails were found in the study
area from late June through August. By August adults vacated the beach zone
and migrated to deeper water with concentrations at 6 and 9 m. Spottail
larvae were concentrated between the beach and 3 m during June through August.
Upwel lings have a profound effect upon spottail spawning and hatching success.
Highest larval densities occurred when spawning was not interrupted by
upwel lings (e.g., I98O) . Spottail larvae were rarely caught at depths
exceeding 3 m. Larval spottails in our samples seldom exceeded 15 mm TL. The

1^3

75 RAINBOW SMELT stations c and d

y» (REFERENCE)

/ ^ STATIONS L AND N

/ (PLANT)

< +
UJ

5 X50
O

^%

a: o

LlI _j
O <

UJ a:

o I-

1978 1979 1980

YEAR

Fig. kO. Geometric mean number plus one of rainbow smelt caught in
trawls at stations C (6 m, south), D (9 m. south), L (6 m, north) and N
(9 m, north) near the J. H. Campbell Plant, eastern Lake Michigan, 1978
through 1980. Graph illustrates the YEAR x AREA interaction.

beach zone is a very important spawning and nursery area for spottails as
evidenced by the high larval and YOY densities found there. YOY spottails
remained in the beach zone through September and began a migration to deeper
water by October, following the outward migration of adults. By November and
December adults were beyond 15 m; YOY fish were at 12 m or deeper.

Larvae —

Introduction — Cyprinids were the most difficult fish larvae to identify
and most were classified as unidentified minnows in 1977 and 1978. Increased
expertise in larval fish identification eliminated most unidentified minnows
from 1979 and I98O samples. Since we felt from 1979 and 1980 data that most
unidentified minnows in 1977-1978 were spottails, we designated all
unidentified minnows collected in 1977-1978 as spottails.

Seasonal di str ibution —

April and May — During I98O, no spottail larvae were collected during
April and May and only a few were caught at the north transect during this
period in 1979. Early spring water temperatures were usually too cold for

spottail spawning and hatching, which occur at water temperatures of
approximately 15-20 C for this species (Heufelder and Fuiman in press). No
spottail larvae were collected during April-May, 1978.

June — The first major occurrence of spottail shiner larvae in the
vicinity of the Campbell Plant during the preoperational period was always
noted in June (Figs. 41-53)- During June of preoperational years spottail
larvae were primarily distributed at depths of 3 "i or less and were 5 ^^ or
less in length, indicating that they were newly hatched. During early June
1977. 1979 and I98O, spottail larvae were collected at the north transect, but
not at the south, while in early June 1978 mean densities at north and south
transects were comparable. Mean densities in early June over the k yr study
were less than 1000 larvae/1000 m^ and larvae were caught primarily i n 3 ni of
water or less. Larval densities in late June were generally less than 1000
larvae/1000 m^ (except at the north transect in late June 1979) » suggesting
some spawning occurred during late May and early June of these years. No
spottail larvae were caught in June 1978. In June of all years, maximum
densities of spottail larvae were collected when water temperatures were
warmest.

July — Mortimer (1975) gave a detailed description of upwel lings which we
have found can have a pronounced effect upon the distribution of larva!
spottail shiners as well as other species in Lake Michigan through the
mechanism of depressing spawning activity. The contrast in larval spottail
shiner densities during early July 1979 and I98O clearly demonstrates the
effect of this phenomenon. A cold-water upwel ling in early July 1979 caused
an interruption in spottail spawning and substantially reduced densities of
spottail larvae. In late June 1979. when mean water temperature was about
14.5 C at north and south transect beach to ^-m stations, mean densities of
1400 and 300 larvae/1000 m^ respectively were recorded. During early July,
mean water temperature was about 10.0 C and mean densities were only 100
larvae/1000 m^ or less at beach to 3""'" stations. During early July I98O when
no upwel ling occurred, mean density of spottail larvae was 7000/1000 m^ at the
south transect beach to ^-m stations when the mean temperature was 16. 9 C.
During periods of upwel lings, densities of spottail larvae were higher at the
north transect beach to 3*ni stations than at the south transect. For example,
mean densities of 20 larvae/1000 m^ were observed at the south beach to 3-m
stations vs. mean densities of 100 larvae/1000 m^ at north beach to 3"^
stations in early July 1979- Although Lake Michigan waters were too cool for
spottail spawning and hatching, spottail spawning may have continued in the
discharge channel and larvae washed into Lake Michigan at the north transect.

During early July 1977 and I98O, when no upwel lings occurred, high mean
densities of spottail larvae were observed at both north and south transect
beach to 3"""^ stations. During early July 1977 mean densities ranged from 1400
larvae/1000 m^ to 3500 larvae/1000 m^ at beach to 3-m stations. In early July
1980 mean densities at beach to 3-ni stations ranged from 3OOO larvae/1000 m^
at the north transect to 8OOO larvae/1000 m^ at the south transect. Water
temperatures were approximately I7.O C at both north and south transect beach

145

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OCNSITY TRANSECT TEMP.

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LAKC MCHnAM
STATIOM 6-9M
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20-28 JUL

8| 20- 2« JOLT l»7'7
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20-21 JULY 197
LAKE MCHKAN
STATION 6-»M
S TRANSECT
0AY4>NIGHT
X-tl.4 (2 t)
M- 5

10 15 20

TOTAL LENGTH (MM)

5 10 15 20 25

Fig. 42. Density (no./ 1000 M^ plotted on log scale) of larval spot tail shiners
collected during April to September 1977 at 6 and 9 m (all contours, depth
strata and diel periods pooled) near the Campbell Plant, eastern Lake Michigan.
Horizontal line across each bar denotes mean density while height of bar re-
presents ± 2 S.E. Midpoint of water temperature range (vertical line) at time
of collection is shown. Length-frequency histograms for all larvae collected
during each period are also shown. N » number of larvae collected, x = mean
length of larvae, S.E. given in parentheses.

147

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DENSITY TRANSECT TEMP.

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3 10 15 20 25

5 10 15 20 25

TOTAL LENGTH (MM)

Fig. 43. Density (no-/ 1000 M^ plotted on log scale) of larval spottail shiners
collected during June to September 19 77 at 12 and 15 m (all contours, depth
strata and diel periods pooled) near the Campbell Plant, eastern Lake Michigan.
Horizontal line across each bar denotes mean density while height of bar re-
presents ± 2 S.E. Midpoint of water temperature range (vertical line) at time
of collection is shown. Length-frequency histograms for all larvae collected
during each period are also shown. N = number of larvae collected, x = mean
length of larvae, S.E. given in parentheses.

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5 10 15 20 25 5

10 15 20 25 5 10 15 20 75
TOTAL LENGTH (MMi

Fig. 45. Density (no./ 1000 M plotted on log scale) of larval spottail shiners
collected during April to September 1978 at 6 and 9 m (all contours, depth strata
and diel periods pooled) near the Campbell Plant, eastern Lake Michigan. Horizon-
tal line across each bar denotes mean density while height of bar represents ± 2
S.E. Midpoint of water temperature range (vertical line) at time of collection
is shown. Length-frequency histograms for all larvae collected during each period
are also shown. N = number of larvae collected, x = mean length of larvae, S.E.
given in parentheses.

150

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DENSITY TRANSECT TEMP.

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SOUTH

1978

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111-

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LAKE MCHK:aN
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TRANSECT
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17-21 JULY 1978
LAKE MICHK^AN
STATION 12-15M
S TRANSECT
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LAKE MCHIGAN
STATK}N 12-15M
S. TRANSECT
DAY ■»■ NIGHT

X- 4 5 (0 0)
N- 1

30
20
10

5 1C i5 20 25 5 10 15 20 25 5 10 15 20 25

TOTAL LENGTH (MM)

Fig 46. Density (no./lOOO M^ plotted on log scale) of larval spottail shiners
collected during April to SeptenAer 1978 at 12 and 15 m (all contours! depthT
strata and diel periods pooled) near the Campbell Plant, eastern Lake Michigan.
Horizontal line across each bar denotes mean density while height of bar re-
presents ± 2 S.E. Midpoint of water temperature range (vertical line) at time
of collection is shown. Length-frequency histograms for all larvae collected
during each period are also shown. N = number of larvae collected, x = mean
length of larvae, S.E. given in parentheses.

151

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STATION S-tM
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20-22 AUG

20-22 AUGUST 1979
LAKE MCHIGAN
STATION 6-9M
N TRANSECT
OAV-t-NtGHT
X- 3 (0 2)

Hm 3

1-2 AUOUST 1079

STATION •-»!
S. TRANSECT
DAY •»■ NIGHT
X- 3.0 (0.0)

20-22 AUGUST 1979

LAKE yiCHIGAN

STATION •-9M

S TRANSECT

0AY>NN»4T

X. 4 3 (0 0)

N« 1

5 10 15 20

5 10 15 20 25 5 10 15 20 25

Fig<

TOTAL LENGTH (MM)
48. Density (no./ 1000 M^ plotted on log scale) of larval spottail shiners

collected during April to September 1979 at 6 and 9 m (all contours, depth
strata and diel periods pooled) near the Campbell Plant, eastern Lake Michigan.
Horizontal line across each bar denotes mean density while height of bar re-
presents ± 2 S.E. Midpoint of water temperature range (vertical line) at time
of collection is shown. Length-frequency histograms for all larvae collected
during each period are also shown. N » number of larvae collected, x » mean
length of larvae, S.E. given in parentheses.

153

ANO IS M

40

30

20

10

I

14-16 MAY

14-16 MAY 1979

LAKE MICHIGAN
STATION 12-15M
N. TRANSECT
OAY+NIGHT

X- 5.0 (0.0)
N- 1

1-2 AUG

20-22 AUG

I

20-22 AUGUST 1979
lAKC MICHIGAN
STATION 12- ISM
N. TRANSECT
OAY+NIGHT

X- 4.8 (0.0)
N- 1

5 10 15 20

30

20

10

1-2 AUGUST 1979
LAKC MCHIGAN
STATION U-ISM
S. TRANSECT
OAY+NIGHT

X- S.8 (1.1)
N- 3

I

20-22 AUOUST 1979
LAKE MCHIGAN
STATION 12- ISM
S. TRANSECT
OAY+NIGHT

X- 6.0 (0.0)

Hm 1

5 10 15 20 25 5 10 15 20 25

TOTAL LENGTH (MM)

Fig. 49. Density (no./ 1000 n plotted on log scale) of larval spottail shiners
collected during April to September 1979 at 12 and 15 m (all contours, depth
strata and diel periods pooled) near the Campbell Plant, eastern Lake Michigan.
Horizontal line across each bar denotes mean density while height of bar re-
presents ± 2 S.E. Midpoint of water temperature range (vertical line) at time
of collection is shown. Length-frequency histograms for all larvae collected
during each period are also shown. N = number of larvae collected, x = mean
length of larvae, S.E. given in parentheses.

154

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TRANSECT TEMP.

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1980

+ 25

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16-18 JUN

1-2 JUL

14-16 JUL

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40
30
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LAKE MCHICAN
STATtON 6-9M
N TRANSCCT
OAY-fNiCMT

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LAKE MICHICAN
STATION 6-9M
N TRANSECT
OAr-t' NIGHT
X- 5 1 (0.0)
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1-2 JULY 1980
LAKE MCHRAN
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LAKE MICHIGAN
STATION 6-9M
M. TRANSECT
DAY •»■ NIGHT

14-16 JULY I98(
L>KE MCHIGAN
STATION 6-9M
S TRANSECT
OAY-f NIGHT
X- 5 2 (0.1)
N- 21

= 1 4-6 AUGUST 1980
21 LAKE MICHIGAN
^LSTATION 6-9M

Th. TRANSECT

^ oay+nk;ht

4-6 AUGUST 191
LAME URHKMN
STATION 6-9M
S. TRANSECT
DAY ANIGHT
X- 5 5 (00)

5 10 15 20 25 5 10 15 20 25 5 10 15 20 25
TOTAL LENGTH (MM)

Fig. 51. Density (no./ 1000 M plotted on log scal^) of larval spottail shiners
collected during April to September 19 80 at 6 and 9 m (all contours, depth
strata and diel periods pooled) near the Campbell Plant, eastern Lake Michigan.
Horizontal line across each bar denotes mean density while height of bar re-
presents ± 2 S.E. Midpoint of water temperature range (vertical line) at time
of collection is shown. Length- frequency histograms for all larvae collected
during each period are also shown. N = number of larvae collected, x = mean
length of larvae, S.E. given in parentheses.

156

300

100 .-

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O
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%

$ 10

12 *N0 IS M
OgWSITT TRAW8ECT TgMP.

1980

D

I

NORTH
SOUTH

•• 25

-■ 20

n

15 g

-• 10

•• 5

2-4 JUN

16-18 JUN

U2 JUL

14-16 JUL

4-6 AUG

40
30
20
10

2-4 JUNC 19M

LAKE MICHIGAN
STATIOM 12 -OM
N TRANSECT
OAT-^NKNT
X- 4 (0.0)
N- I

SIS M-w <

STATION 12- ISM
N. TNANSeCT
OAY-fMGHT

1-2 JULr ISM
LAKE MCHMMN
STATION 12- OM
N TRANSECT
OAT-fMCMT
X- 5.2 (0 0)
N- 127

UJ
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5 10 15 20 25 5 10 15 20

30

20 ^

10

1-2 JUtY IMO

LAKE MOHICAN
STATION 12 -ISM
S TRANSECT
0AY4MGHT
X- 3.0 (0 1)

u

5 14-» JULY IMO
CAKE MCHICAN
STATION 12- ISM
N. TRANSECT
OAr-t>NICHT

L

LAKE MCHKAN
STATION 12- ISM
S TRANSECT
0AY4MCHT

f

4>« AUGUST IM
LAME MCHRAN
STATION 12- OM
N TRANSECT
OAT-t-NKMT
X- 3.0 (0 5)
N- 2

H 4-«

n LAKE

U STAT

7 5 T'

-• AUGUST IMO
LAKE MCHRAN
STATN}N 12-ISM

5 10 15 20 25 5 10 15 20 25 5 10 15 20 25
TOTAL LENGTH (MM)

Fig. 52. Density (no./lOOO M plotted on log scale) of larval spottail shiners
collected during April to September 1980 at 12 and 15 m (all contours, depth
strata and diel periods pooled) near the Campbell Plant, eastern Lake Michigan.
Horizontal line across each bar denotes mean density while height of bar repre-
sents ± 2 S.E. Midpoint of water temperature range (vertical line) at time of
collection is shown,. Length-frequency histograms for all larvae collected
during each period are also shown. N » number of larvae collected, x = mean
length of larvae, S.E. given in parentheses.

157

1977

3000--

-fl5» _,,^"'* ,..>-''- ,,..>-^^ „,..>■'- .^-

SAMPLING PERIOD

NORTH TRANSECT

3000- -

-=^15

.^^.^>;,^^^''

SOUTH TRANSECT

SAMPLING PERIOD

Fig. 53. Mean density (no./ 1000 m ) of larval spottail shiners for
north and south transect stations in Lake Michigan near the J. H.
Campbell Plant, 1977 to 1980. Mean densities were calculated by
averaging densities over all gear (plankton nets and sleds), strata
and diel periods (day and night) sampled. O = no sampling performed.

158

1978

^>o-

,.^^^^ ^-^'^\..^^^^\.^'''Z^

NORTH TRANSECT

SAMPLING PERIOD

„.'-",...>-=" ..'*,„.'* .v^''.^-^'

SAMPLING PERIOD

SOUTH TRANSECT

Fig. 53- Continued.

159

1979

4519 9577

2 000

O
O

o

> lOOO-

<

SAMPLING PERIOD

NORTH TRANSECT

9337

2000

o
o
o

^ 1000 ■-

<

^-i:i5

,>"^'"..«^''.^>''" «'-'\.^^^\

SAMPLING PERIOD

SOUTH TRANSECT

.^'^'

F ig . 53. Cont inxied-.

160

1980

4176 5162 10028

NORTH TRANSECT

SAMPLING PERIOD

3000 ■

2000-

<
>

<

O

!0I2B

18099
I

9zoe

I

'■W

^15

SAMPLING PERIOD

Fig. 53. Continued.

SOUTH TRANSECT

161

stations. During early July of all k yr spottail larvae were most
concentrated i n 3 "^ of water or less (Figs. 41-52); nearly all were newly
hatched larvae approximating 5 ^^ in length.

Larval spottail distribution in late July was closely related to water
temperature prior to and during sampling. In 1977 densities remained
comparable from early July to late July. Water temperatures (Figs. 41-52)
were not as high in late July as earlier in the month; consequently, lower
densities were found in late July. Mean densities at beach to 3-m stations
during late July were from 2500 larvae/1000 m^ to 3000 larvae/1000 m^ with
little variation between transects. Outside the ^-m depth contour in late
July 1977 larval fish densities were low. From 6 to 15 m mean densities were
less than 10 larvae/1000 m^ at both transects. In late July 1978 water
temperatures declined from those observed in early July and a concomitant
decline in spottail larvae densities was also observed (Figs. 44-46). Spottail
larvae were almost exclusively restricted to 3 m of water or less in late July
1978. Modal length of those caught in late July was 8 mm suggesting that
spawning and hatching was suppressed during late July 1978 due to depressed
water temperatures. As water temperatures warmed during late July 1979 there
were increased densities of spottail larvae at all Lake Michigan stations 3 m
and less (Fig. 47); mean size of larvae caught at this time was 5.3 mm,
suggesting that most were recently hatched. As has been typical in all years
sampled, when spottail larvae were present at north and south transects, they
were more abundant at north stations near the discharge. Mean spottail larvae
densities were very low (< 30 larvae/1000 m^) at depths greater than 3 m of
water (Figs. 41-52) .

The intensive spawning and hatching activity observed in early July I98O
continued into the latter part of the month due to a lack of interruption of
the summer warming trend. Mean densities of larval spottails exceeded 2000
larvae/1000 m^ at beach to 3-m stations at both transects. During late July
mean densities of 20-70 larvae/1000 m* were found at 6- to 9"ni stations at the
north and south transect, but densities declined somewhat at greater depths.
Mean length of larvae caught at the beach to I5 m in late July I98O was 5-4 mm
(Fig. 51) f suggesting spawning and hatching was ongoing between the beach and
15 m* Data from 198O suggest that if an upwelling does not occur in July,
permitting an uninterrupted warming trend, intensive spawning and hatching
activity will occur from the beach to 9 ni for the entire month.

August — During 1977f sampling was performed only once during August and a
pronounced decline in densities from July levels was noted. Highest mean
densities at any station were less than 30 larvae/1000 m^ with maximum
densities found at beach to 3*ni stations (Figs. 41-43). No spottail larvae
were caught beyond the 3""^ depth contour. A mean length of 15^3 nini in August
1977 Indicated that spawning and hatching subsided after July.

During early August 1978 the only appreciable densities of spottail
shiner larvae were at depths of 3 ni or less (Figs. 44-46). Highest mean
densities were found at south transect beach stations and length-frequency

162

data showed a high percentage of recently hatched larvae (mean length « 5.7
mm, SE « 0.3) indicating that spottail spawning had continued until at least
late July during 1978.

Highest mean densities of spottail larvae collected during 1979 were
noted in early August. Spottail larvae at this time were primarily distributed
from the beach to 3 m (Figs. 47"^9) » although sporadic occurrences of lower
mean densities at deeper stations were observed. Length-frequency data
indicated that many larvae caught in early August 1979 (over 50%) were 6 mm or
less and probably recently hatched, indicating that spottail hatching
continued through late July 1979*

During early August I98O mean densities of spottail shiner larvae
remained very high at beach to 3"'" stations. Mean densities between 4000 and
5000 larvae/1000 m^ at both south and north beach to 3-m stations were found.
These were the highest densities of spottail larvae noted for early August of
any study year. Larvae were concentrated in I-3 m of water; all station
groupings deeper than 3 m had mean densities less than kO larvae/1000 m^.
Length-frequency data showed that over 50% of the spottail larvae caught in
early August were around 6.0 mm indicating that hatching and spawning
continued through late July I98O. High densities of larvae noted in early
August 1980 were presumably due to the lack of upwel lings in I98O allowing
spawning to continue uninterrupted. Late August collections during all years,
except 1978 when mean densities from early to late August were comparable,
showed a marked decrease from early August densities of spottail shiner
larvae. As in previous months densities were greatest at beach to 3-m
stations (Figs. 41-52) with sporadic low densities at deeper stations. During
all if yr few larvae less than 6.5 mm were collected in late August which
suggests that spottail spawning and hatching does not occur past early August
in Lake Michigan in the vicinity of the Campbell Plant, even when optimal
conditions exist for the entire summer, as occurred during 198O.

During September 1977-1979 no spottail larvae were collected in Lake
Michigan, probably due to growth of fish and net avoidance. A few spottail
larvae were caught at north transect beach stations during I98O, most likely
because of optimal conditions which existed during that spawning season.

Young-of- the- Year —

Spottails may become sexually mature when they are 1-yr old (Wells and
House 1974). Jude et al. (1979a) reported a size range of 35-74 mm by April
for yearlings. Wells and House (1974) found that spottail growth did not
begin until June in southeastern Lake Michigan; therefore, yearlings would be
the same length range (35*74 mm) from late fall the year before into June. By
July few fish under 50 mm were caught, demonstrating that considerable growth
occurs in June and July. By August yearlings cannot be distinguished from
smaller adults in length-frequency plots.

163

Seasonal di str i but ion --

August — YOY spottails first appeared in mid-August in the study area.
Due to yearly fluctuations in water temperatures during spawning, sizes of YOY
spottails varied by month depending upon spawning time. Jude et al. (1979b)
found that in 1973 and 197^ YOY spottails had grown to 15""^^ nim by August,
25-5^ fnfn by September and 25-64 mm by October in southeast Lake Michigan.
Wells and House (197^) found an average length of 79 ^^ ^or spottails at the
end of their first year of growth in southeastern Lake Michigan. From their
data a maximum length range of 65-79 ^^ would be achieved by November and
December. These length ranges will be used to define YOY spottail (by month)
in the following discussion of YOY spottail distribution in our study area.

In 1977 YOY spottails first appeared in August beach seine hauls
(Fig. 54) and were caught mostly during the day. Although little water
temperature variation existed among beach stations, most were caught at the
north transect beach stations in August 1977* August 1978 distribution of YOY
spottails was quite similar to that observed during the same period in 1977*
Nearly all were caught during the day, with equal distribution between north
and south transects. Water temperatures ranged from 23-0 to 25-7 C at beach
stations. No YOY spottails were caught in trawls during August 1978
indicating that YOY spottails were concentrated in I.5 m of water or less.

YOY spottails were nearly absent from our catches in August 1979; ^^ss
than 10 were collected. Upwel lings, which interrupted spawning during 1979»
apparently precluded the development of spottail larvae to the YOY stage by
August in 1979-

Because there was no interruption in spottail spawning and hatching in
1980 (due to lack of upwellings), YOY spottail shiners had grown to ^5 nim by
mid-August. In stark contrast to their near absence during August 1979f
nearly 250 YOY spottails were seined in August I98O. Most were seined during
the day at the north transect where the water temperature was slightly warmer
(22.6 C) than at the south transect (20.2 C) . During August of all years, YOY
spottail shiners were caught during the day in 1 .5 m of water or less. The
diel catch difference observed may be explained by YOY spottails feeding in or
near the beach during the day. At night YOY move out beyond the 1 .5-ni depth
contour. Price (1963) found that spottails in Lake Erie fed mostly in the
morning with feeding activity decreasing throughout the day. Absence of YOY
spottails from depths greater than 1 .5 m suggests a preference by smaller
spottails for shallower water. Wells and House (197^) noted that in Lakes
Erie and Michigan, spottails preferred shallow, warm water and that smaller
fish tended to inhabit shallower water than larger fish.

Septembei For reasons not entirely known (e.g., photoperiod, water

temperatures, feeding behavior, etc.) spottail shiner densities seemed to
increase with depth during September. Adults were the first to move offshore,
while YOY spottails were concentrated in the beach zone. During September
1977» the largest YOY catch of any year (nearly 3900) was collected in beach
seine hauls; nearly 80% of these were caught at north discharge beach station
R. Warm water from the plant's onshore discharge apparently attracted

161+

spottails to the north transect beach station. Water temperature at the north
station was 15*6 C compared to 11.1 C at south reference beach station P.
Schooling behavior may also have caused this large catch of YOY spottails. No
YOY spottails were caught in trawls during September 1977-

Nearly half the spottail shiners collected in September 1978 were YOY
fish 25"55 nfim; 209 were caught in beach seines, IO5 were trawled at the 9"ni
north transect station and 104 at the 3"ni south transect station. These data
suggest that, although YOY spottails were concentrated in 3 "i of water or
less, there was also a movement to deeper water as evidenced by the large
catches at trawling stations. The seasonal movement to deeper water had begun
by September in 1978.

The lowest September catch of YOY during the preoperational study
occurred in 1979- Approximately 90 YOY spottails were seined at north
transect beach stations; none were caught in trawls. Because cold water
temperatures occurred during the 1979 spawning season (see RESULTS AND
DISCUSSION, Spottai 1 Shiner , Larvae), high egg and larval mortality and
disrupted adult spawning behavior most likely resulted in low recruitment of
YOY spottails in September 1979-

September I98O catches were the second largest for that temporal period
during the 4-yr preoperational study (Fig. 5^) • Trawls (mostly night)
accounted for 38I YOY and day seines collected SkU (79 were seined at night).
Trawl data indicated that YOY spottails were concentrated at 6 and 9 ni. YOY
spottails were consistently found in the beach zone during the day during all
k yr. The large catch at 6 and 9 ^ indicated that the annual migration to
deeper water was in its initial stages in September I98O.

Spawning and hatching apparently continued uninterrupted in I98O which
resulted in large numbers of YOY spottails being present in September I98O
collections. This is in contrast to the near absence of YOY from samples
taken during the same period in 1979 when upwel lings occurred during the
spawning season.

October — October catches of YOY spottails during all years (Fig. 54) of
the preoperational study were influenced by the annual fall migration of
spottails to deeper water in Lake Michigan as was described by Wells (I968)
and Jude et al. (1979a, 1979b). YOY spottails are nearly absent from the
beach zone in October (Fig. 5^) . Never more than 52 YOY spottails were seined
in October of any year, a drastic reduction from numbers of fish seined in
September. In all years except I98O, few YOY spottails were caught in October
and those caught were concentrated at 6 m and 9 ^* The large year class of
spottail shiners produced in I98O, possibly due to optimal water temperatures
throughout the entire spawning period, is evidenced by October I98O trawling
data (Fig. 54). YOY spottails in large numbers (for October) were trawled at
6, 9, 12 and I5 m (II6, 424, l82 and 200 fish, respectively). Because of
warmer water temperatures during 198O the migration to deeper water was most
likely delayed and fish remained in the study area for a longer period of time
than in other years.

165

'YL

^ia_

AD

NORTH TRANSECT
1977

JUN

YL

•AO'

<
u
en

S
o
o

o

UJ
03

3

10' -f

.,3__ h- YOY

xlO^-f
xlO' -j-
xlO*^= ^

YL-f.

YOY

U u U Li i4i L

AD

I, I . .1 ,

YUAO-

.YOY— '

YLSAD-

fiUC

'xlO' -j-

I

' X ; J*'

•x:C'

'x;g*
:xiG'
1x:g^

—14 Ll U Li J4.

-YOY 1-

• YLSAD-

h I lL

•YOY-

YL&AD-

—4- ± - -ti

4C 50 80 :cn 20 lao

TOTAL LENGTH (MM)

160

180

_ NCV

COG

Fig. 54. Length-frequency histograms for spottail shiners collected
during June - December 1977 and April - December 1978-1980 at north and
south transects. Stations were combined into two groups for the north
transect: beach and 3 m; 6 and 9 m and into three groups for the south
transect: beach, 1.5 and 3 m; 6 and 9 m; and 12 and 15 m. Diel periods
and gear types were pooled. YOY = Young-of-the-year; YL = Yearling; AD =
Adult .

166

<
o

CO

S
o

X
CO

Z

1x10^-
:xlO' -

1x10*-
1x10*-
1x10^-
1x10' -

1x10*-
1x10'-
1x10'-
1x10' -
1x10* =
1x10'-
1x10'-
1x10'-

IxIO*-
IxfO'-
1x10'-
1x10' -

1x10*-
1x10'-
1x10'-
1x10' -

1x10*^
1x10'^
1x10'-
1x10' -

lo-3n l5-9n :'2-:5r

SOUTH TRANSECT
1977

YL

— AD

— AD

HYOY-f

•YL

AD-

• YOY -

YUAD

YOY —

YUAD

-+-

YOY

YL5A0

YOY

YLSAD

-+-

-f-

■^

-^

■¥-

-f-

JUN

JUL

AUG

SEP

OCT

NOV

DEC

10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160
TOTAL LENGTH (MM)

Fig. 54 . Continued.

167

xlQ^

xiG'

xlO'

x10'

xlO'

xlO'

xlQ'

xlO^

xlO^

xlQ'

1x10*

UJ

-J
<
o

CO

1x10'
1x10'
1x10'

2

3

1x10*
1x10'

i

1x10'

q:

Ui
(S

D
Z

xlO'

1x10*
1x10'
xlO'

xlO'

xlO*

xlO'

xlO'

xlO'

xlO*

xlO'

XlO'

xlO'

xlO*

x10'

xlO'

xlO'

•YL

lo-3r is-en

-AD NORTH TRANSECT

1978

I L

•YL

■AD

■AO

_Y Y Y Y 1 r-

YL

AO

YOY

YL

AO

•YOY

AO

►YOY

YLSAO

YOY

YL&AO

YOY

-V ^-

_j J J 1 1

RPR

nPY

JUN

JUL

RUG

SEP

OCT

NOV

10 20 30 40 50 60 "'0 8C 90 100 HO 120 130 140 150 I'SO
TOTAL LENGTH (MM)

Fig . 54 . Cont inued .

DEC

ib8

. AO .

SOUTH TRANSECT
1978

YL-

AD-

fiPR

IxiC*

1x10'

<

1x10'

CD

o

'x'O'

= 1x'0'

X

<2 Ix'O' —
a.

o

_ 1x10*

CD

'^

YL-

AD-

^

1

!

1

— ~

1

1
1
1

;

}
1

II
i;

V

ll

YL

AD.

AD'

•YOY

YUAD

nPY

YOY

YLSAD-

JUN

ill

I i; I

I i: I

. i: i: I

I I , I !; ii !.

JUL

RUG

SEP

'xlQ' -f

IX.u

! X 1 u'

Ir I U I, ij: lii Ij : J i i l ii

'YOY

YL&AD •

-ii ll .;• I! I|: h'

YOY-

-YUAD.

OCT

NOV

Fig. 54. Continued,

20 40 6C 80 100 120 140

TOTAL LENGTH (MM)

160

180

169

NORTH TRANSECT
1979

l-VL

I0-3.

i6-9^'

AD

<
u
en

2
o
o

u.
o

CD

IxiO'
1x10'

IxiO'

ixlO'

IxiQ'

1x10*

1x10'

1x10'

1x10'

1x10'

1x10'

1x10'

1x10'

1x10*

1x10'

1x10'

1x10'

1x10*

1x10'

1x10'-

1x10' ■

1x10*"
1x10'-
ixlO'-
1x10' -

1x10*-
1x10' ■

1x10'-
1x10' -

4 U

^

»YL

-*! T r

AD —

PPR

— T f T r-

I YL •

-1 1 1

AD

YOY

■ YUAD-

4 L

YOY

YUAD

YOY

YUAD

-r ^ V f

-r ] r

I^YOY

YLSAD -

I I I

-r f r

HflY

-t

-r

i

1

1 i

1 1
1 1
i ■

—

-

1 1 ! 1
1

1 1

YL —

1

AD

—

-

l!

1 1!

1

i

i

i
1

1

1

1 1
1 1
1 1

1 1

~

^, ^,.._

1—— YOY

, ■. , 1,

•

■

An .

' ' ■ r'' — -I*'- T h

_|

-

I u

!

y '

1

r n

^

1
1
1

1

L

ii

^ — 4 — I — I — 1

JUN

JUL

RL/G

SEP

OCT

MCV

10 20 30 40 50 50 70 80 90 100 nO 120 130 '40 '5C :5:!
TOTAL LENGTH (MM)

Fig. 54. Continuea.

170

unr

ixlQ'

1x10*
-xlO^
IxlO'
IxlO'
1x10'
IxiO'
1x10'
IxIC
ixIC
1x1C'
S 1x10'
U 1x10-

o

i 1x10'
X 1x10'

CO

^ 1x10^
O 1x10*

£ 1x10'

CD

i 1x10'
Z

1x10'

1x10*
1x10*
1x10'
1x10'
1x10*
1x10'
1x10'
1x10'

1x10*
1x10'

1x10'
1x10'

SOUTH TRANSECT
1979

lo-3n !6-9n :i2-i5n
— AD -

n 1 1 T-

— YL

n — ^-

AD

AD

YL

— AD -

— AD

_, , Y-

•YOY

YUAD

YOY

YUAD

YOY

YL&AD

IP IJ. i.
li: lii 1:-

YOY

YUAD

-P

RPR

nPY

JUN

JUL

RUG

SEP

OCT

I I

NOV

DEC

10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160
TOTAL LENGTH (MM)

Fig. 54. Continued.

171

q:

UJ
(D

Z

,X !u ■

■xlO' ■

ix id' ■
1x10'-
ixlO^-
1x10' ■
IxlQ*-
IxiC-
1x10'-
ixlO' ■

1x10*^
1x10'-
1x10^-
1x10' ■

1x10*:
1x10'-
1x10'-
1x10' -
1x10*-
1x10'-
1x10'-

:xio' -

ix10* =
1x10'-
1x10'-
ixlO' -

1x10* =
1x10'-
1x10'-
1x10' -

1x10* =
1x10'-

1x10'-
1x10' -

YL

AD

lo-3r l5-9r

NORTH TRANSECT

1980

YL

• AD —

I .1

J — M — i;-

AD

YL •

AD

n 1 1 1 r

'YOY -

T T T T T

YLSAD

'] 1 T"

•YOY

-I T T 1'

YL&AO

-jj.

■YOY

r T Y Y V ' l ' f

YL6AD

-r '] V

YOY

YLSAD

-T 1 1*-

YOY

— YLSAD

RPR

flRY

r ^ , , JUN

JUL

n 1 1

flUu

SEP

OCT

-f 1 1

NOV

10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160
TOTAL LENGTH (MM)

Fig. 54. Continuea.

DEC

172

AD

SOUTH TRANSECT
1980

AD-

<
o

CO

fi
o

o

X
CO

a:

OB

2

3

...t , , ll* 1

'■ i- I- i:
u L li: U:

i:
i:

i:
i:

1:

i:

1-

li
i:
1-

iL 111

1x10'-^
1x10^ -J-
1x10' -|-
1x10* =1^
1x10'— 1-

;xio'-|-

1x13' — L
1x13' =k-
1x10' -f

MO' -^

;xio'4-

1xlO'-h
1x10^ —
1x10' ■
1x10*-

IxIO'

'x!C^

'xlO*:
IxIO'-
1x10'-

YL-I-

AD-

I— YL An -

1

, li

ii

1-

1*: 1

1

1.
i:

1;
1 =

i:
1:

1
1-

1

1

i'

ii
P 1

j — YOY f— YL

AD-

YOY

YUAD-

■ YOY-

■ YUAD-

• YOY —

-YUAO-

-YOY-

-YLSAO-

2C

40

60

80 'CO 120 140

TOTAL LENGTH (MM)

Fig. 54

Continued,

1 i
— I— , 1 l'

1.
i:

u: IL 1

1

1

1

j

1

i.
1-

ii

i^

I: li

^RY

JUN

JUL

flUC

, NCV

•80

173

November and December — Catch data from November and December of all
preoperational years showed that YOY spottails were the last group to migrate
to deeper water. Two YOY were caught in the beach zone in November; most were
at 9 m or deeper. December trawl data for all years showed that YOY spottails
were present at 12 m and deeper. No unusual trends were apparent for YOY
spottails during the November-December study period.

Adults —

Seasona 1 d i s tr i but i on —

April and May — Spottail shiners were collected in very low numbers during
April 1978, 1979 and I98O. No sampling was performed during April 1977- The
low density of spottail shiners in the study area during April is typical of
their spring distribution in southeastern Lake Michigan. Wells (I968) found
that spottails moved to shallower depths during summer (6-10 m) and deeper
water (6-5O m) during winter. In Lake Michigan near the Campbell Plant the
inshore migration began in May, as evidenced by the large numbers of large
adults (85-135 mm) caught: 425. UU and 565. respectively, in 1978, 1979 and
1980. During May 1978, 1979 and I98O, densities of adult spottails were
highest in the beach zone out to 6 m. Although sporadic catches occurred at
all sampling depths, between 50 and 7(>% of the May adult spottail catch was
collected from 6 m or less of water from 1978-1980 (Fig. 55).

June — By June, spottails have completed their movement to the inshore
area. Most fish were found in 6 m of water or less, with sporadic occurrences
out to 15 m. Gonad development data (Fig. 55) along with larval fish data
(see RESULTS AND DISCUSSION, Spottail Shiner , Larvae) showed that spottail
spawning occurred during June of all years. The distribution of ripe-running
adults as well as newly hatched larvae and fish eggs strongly suggests
spottails spawn in water 6 m or less. June adult spottail catch increased
each successive year during the 4-yr study. Only 559 were caught in 1977 in
contrast with 3083, 3^42 and 3889 fish for 1978. 1979 and I98O respectively.
Night gill nets were not set in June 1977 resulting in less sampling effort
for that year. During 1977 and I978 beach seines and bottom gill nets caught
most adult spottails with relatively few caught in bottom trawls. During
those years north transect beach stations accounted for most of the fish
caught in seine hauls. Warmer water temperatures at north transect beach
stations than at the south transect beach station were most likely responsible
for the catch difference among these stations (Fig. 22). In contrast to the
low numbers of adult spottails caught in trawls during June 1977 and 1978,
70-72% of the June 1979-1980 catch was collected in bottom trawls. As would
be expected most were trawled at night from 6-m contours or less. During June
1980 water temperatures were warmest at 3 m (14.5 C) and decreased with
increasing depth (7.9 C at 15 m) . Nearly one-half of the June I98O trawl
catch was taken at the 3"^ south station. This large catch (1372 fish) was
most likely due to warmer water and spawning activity. The lowest June beach
seine catch of the entire study period occurred in I98O.

174

480

320-

160-

0-'

Q

UJ

K 480-

O

UJ

NO

O
O

(f)

320-

160

Ns9

UJ 480-

cr

< 320-

o '«o

or

li^

QD

5 480-

320-

160

N:29

ND

Ns|94

N = 665

N=I24

APR MAY

N = 408

L

N3I36

L

Ms 596

N«76l

Ns725

JUN

1977

■ »WELL DEVELOPED AND
RIPE-RUNNING GONADS

n»SPENT GONADS

N»I34 N = I27 Nal77

1978

N»270

^

N:284

N«I27

N=75 Ns44 Ns44

N«328 Ns277

Jl Jl

I I

1979

N*IOO N36I

N«900 N«228 ^ .^,

^^_^ Ns365 N«I67

1980

N3402 Ns443 N « 99

JUL AUG SEP OCT

SAMPLING PERIOD

NOV

N«26

Nsl06

Nsl5

DEC

Fig. 55.- Number of mature spottail shiners with well developed, ripe-
running and spent gonads collected monthly during June-December 1977
and April-December 1978-1980 near the J. H. Campbell Plant, eastern Lake
Michigan. N = total number of mature spottail shiners caught per month

175

Some general trends observed during June of the preoperational study show
that adult spottails are found almost exclusively from the beach zone out to 9
m with densities increasing with decreasing depth. Numbers of fish caught in
beach seines were greater during the day, while bottom gill net and trawl
samples were largest at night. Most of the adult spottails ranged in size
from 100 to 135 nim.

July — The distribution of adul t spottai 1 shiners during July 1977. 1978
and 1979 was quite similar among years, being characterized by large numbers
of fish in beach seine hauls, moderate bottom gill net catches (except 1977
when fishing time was reduced and a low catch resulted), and few caught in
bottom trawls.

During July 1977. 97% of the catch was collected in beach seines. Night
seine hauls at the south beach station contained the most fish, but moderate
catches were also recorded at north transect beach stations. Very few
spottails were caught in water deeper than 1 .5 m in July 1977-

July was the month of peak abundance for spottails during 1978 with beach
seines collecting 58% of the monthly total and bottom gill nets k]%. Few

(<]%) were caught in trawls. Day seines at the north transect, where the
water temperature was 19-0 C, contained the most spottails, while at the south
beach station few spottails were caught and the water temperature was I6.O C.
The largest night catch in July 1978 was taken in bottom gill nets at the 9""'
south station; these were all large adults 105'135 nim. Some small spottails

(95"120 mm) were taken at 1.5* and ^-m south transect stations. Occurrence of
ripe-running fish (Fig. 55) indicated that spawning was ongoing during July.

During July 1979 a cliel activity pattern was observed in beach seine
hauls where 98% of the catch was collected during the day. As in 1978 most of
the catch was taken at north transect beach stations. Warmer water during the
day at these stations (12.5 C in contrast to 10. 5 C at night) and spawning
activity may account for this diel catch difference. Anderson and Brazo
(1978) reported finding high densities of spottails in the beach zone during
the day in June in east central Lake Michigan. it is possible that spottails
spawn primarily during the day in Lake Michigan. Bottom gill net catches
during July 1979 were largest during the day and almost all spottails (89%)
were caught in 6 m of water or less. These were large fish ranging in size
from 105 to 135 mm. As in July 1977 and 1979. ^ew spottails were trawled in
July 1980 and gonad development data (Fig. 55) showed that spawning was
occurring during this time.

The largest monthly catch of spottails in I98O was taken in July. In
contrast to the July catches of 1977"1979. when the majority of the catch was
seined and few were trawled, k7% of the July I98O catch was collected in
bottom trawls, while less than 1% was caught in beach seines. The remainder
of the fish were taken in bottom gill nets. Mostly large fish were collected;
size range was 105-1^5 nim. Trawl data showed that spottails were concentrated
at 6 and 9 m during July I98O; 79% of the trawled fish were caught there.
Trawl catches were nearly equal during day and night. Bottom gill net catches
showed a nocturnal activity pattern with 77% of the spottails caught at night.

176

Largest catches were at 6 m with moderate numbers of fish caught at 1.5» 3 and
9 m. Very few spottails were gillnetted at 12 m. Isothermal waters during
July 1980 were most likely responsible for the difference in catch during this
year, in contrast to the first 3 /^ of the preoperational study, when periods
of upwel lings tended to concentrate spottails in the warmest water in the
study area. However, in July I98O, the mean water temperature from the beach
to 9 m was 21.0 C and the fish moved throughout this zone, while avoiding
cooler waters at 12 and 15 m (mean temperature of I8.I C) . Gonad development
data (Fig. 55) showed that spottails spawned during July I98O; lack of
upwel lings during I98O should produce a strong year class in I98I and I982.

August — By mid-August, when sampling was performed, spottail shiner
spawning was completed in the study area and large adults were dispersed
throughout the area. As spawning ceased in late July or early August
(Fig. 55), fewer adults were found at beach stations. During August of all k
yr of the study, adults were randomly distributed throughout the study area
with peak catches occurring anywhere between I.5 and 15 m; a decline in total
number of fish caught in August was observed in 1979 and I98O. Because water
temperatures were usually quite stable in August and spawning was complete,
spottails may have moved about the lake much more than during other months.
During 1979 and I98O spottails were more dispersed than in 1977 and I978 which
apparently resulted in the lower August catches observed.

September — During September 1977 few adult spottails were in the beach
zone as evidenced by their absence from beach seine hauls. Day and night
trawl hauls caught few adult spottails. Bottom gill net data showed adult
spottails at 1 .5 to 6 m during the day, with largest catches at 1.5 and 3 m.
At night spottails extended their depth range out to 12 m and probably deeper
(few were trawled at 15 ni) .

September 1978 beach seine hauls contained no adult spottails, while
bottom gill net data showed concentrations at 1.5 and 6 m during the day.
Night bottom gill nets showed a scattering of adults throughout the study
area, with the largest catch at 12 m and some at 15 m* Few adult spottails
were trawled in September 1978. Bottom gill nets accounted for the largest
catch of adult spottails in September 1979 (217 fish); 83% were caught at 6 m
or less. No adults were seined in September 1977"1980 and few were caught in
bottom trawls in 1977"1979- The largest catch of adult spottails in September
for the entire study period occurred in I98O (Fig. 5^) • Apparently the annual
fall migration to deeper water by spottails, as described by Jude et
al. (1978, 1979a), Anderson and Brazo (1978) and Wells (I968) had not yet
begun to any substantial degree by mid-September I98O. The stable water
temperatures noted all year in I98O (i.e., no upwel lings) may have prolonged
spottail use of the study area. In contrast to the period 1977"1979> when few
adults were trawled in September, moderate numbers of adult spottails were
trawled during September I98O (853 fish). Nearly 93% of these fish were
trawled at 9 ^f while the remainder were trawled at 6 m; only a few were
trawled deeper than 9 ^* Bottom gill net data showed concentrations of adult
spottails at 3 and 6 m with largest catch {kkk fish) at 3 ni*

177

Generally during September, adult spottails were absent from the beach
zone and were often concentrated between 3 and 9 ni of water. The annual fall
migration to deeper water usually begins by mid-September. Climatic
conditions of the preceding summer may be a determining factor in triggering
the migration to deeper water in the study area.

Octobei — In October 1977"1979 no adults were caught in beach seines or
day trawls. At night some smaller adults (95"1^5 "im) were trawled at 6 and 9
m. Gill nets were not set in October 1977* Eighty-three percent of the
modest bottom gill net catch (53 fish) in October 1978 was caught at 6 m or
deeper. Bottom gill net catches showed larger adults (110-145 mm) uniformly
distributed among 1.5" to 15"nfi stations. The largest catch (60 fish) was
taken at 6 m north. Water temperatures in October 1979 were nearly the same
as September (11.0-13.5 C) , resulting in a delay of the annual migration to
deeper water by all adult spottails.

A few adult spottails were seined at north beach stations in October I98O
when water in the study area was nearly isothermal (9.5"n.5 C) . All seined
fish were caught at night and may have moved in to forage for food. Trawl
data showed concentrations of adults at 6 and 9 ^ with lesser numbers of
adults at 3» 12 and 15 ^* Bottom gill net catches showed that adult spottails
were absent from the study area during the day, while at night adult fish were
concentrated at 6, 9» 12 and 15 ni with the largest catch at 12 m.

In general during October adult spottails were absent from the beach zone
and may have migrated from the study area as was observed in 1977 and 1978.
When climatic conditions remained stable from September into October, as
observed in 1979 and I98O, adults may remain in the study area for a longer
period of time.

November and December — Catches of adult spottails decreased dramatically
in November and December of all years of the study. Sporadic catches of small
adults (100-130 mm) occurred throughout the study area in November and at 12
and 15 m in December. By mid-November the majority of the adult spot tail
population had migrated out beyond the 15"ni depth contour. The largest adults
were the first to leave, followed by smaller adults, yearlings and YOY
spottai Is.

Plant Effects—

The primary difficulty in assessing the impact of Units 1 and 2 on
spottai 1 shiner distribution is our inability to dismiss coincident
construction activity as a probable cause of reference and treatment area
differences. Both the timing of construction activity and resulting rTprap
placement strongly correlate with significant changes in trends observed since
1977» however, there are a few anomalies to this general scheme. During 1977»
when the discharge of Units 1 and 2 was onshore, no significant abundance
differences between north and south transects existed for either larval or
juvenile spottai 1 shiners, except for abundance of juvenile and adult spottai 1
shiners based on seine data. Abundance at the beach station group (Q, R) at
the plant transect was significantly greater than that at reference station P;

178

this transect difference was fairly consistent for years 1977 through I98O
(Fig. 56, Table 31). Bottom gill net data for juvenile and adult spottail
shiners showed no significant differences between stations (or areas) for
years 1977 through I98O (Fig. 56, Tables 32-3^). However, trawl data showed
significantly greater abundance at the north plant transect than at the south
transect (Fig. 57, Tables 35 and 36). Substantially higher abundance of
juvenile and adult spottail shiners was observed at the plant transect during
1979 and I98O, coincident with construction activity (Fig. 57). During
1979-1980 larval abundances were significantly higher at north transect
stations compared with the south reference transect, as revealed by a Wilcoxon
signed ranks test (attained significance level a « 0.0011 and O.OOO6
respectively). Our data thus indicate that, especially during I979 and 198O,
when riprap was being constructed and was available to varying degrees, all
age-groups of spottail shiners were more abundant along the north transect.

Reasons for greater abundance of spottails at the north transect are
unknown; however, two obvious correlations exist. The construction itself may
have provided increased food by displacing benthic organisms during dredging.
The concentration of adults in the area coincident with their spawning season
may have also resulted in a concentrated spawning effort there. This is
substantiated in part by our larval spottail comparisons which show that north
transect spottail larvae densities significantly exceeded those of the south
transect during I979 and I98O (attained significance level a « 0.0011 and
0.0006 respectively). In addition. Dorr and Miller (1975) have documented
spottail spawning on the riprap around the Cook Plant intake structures, which
are located in 9 m of water. Another attractive influence of the intake and
discharge area may be the riprap itself. It is possible that the riprap
attracted spawning adults to the area, especially in 1979 and 1980, due to a
preference for increased cover or food. In all years we could find no
temperature correlation to explain distributional or abundance differences
between the north and the south transect. We thus feel that no definitive
statements regarding the influence of the thermal plume of Units 1 and 2 on
spottail shiner distribution or abundance can be made. If the riprap remains
exposed and if it has an attractive influence on spottail shiners, we would
expect increased numbers of spottails in the north transect area. This may
preclude definitive statements of thermal effect in the future and make
tenuous the validity and utility of only 1 additional yr of study.

Trout-perch

I ntroduction —

Trout-perch inhabit all the Great Lakes and a few of the larger inland
lakes (Hubbs and Lagler 1958). In Lake Michigan this species occurs most
commonly in shoal areas, but may range into water as deep as 94 m (House and
Wells 1973)* This species is considered benthic as most fish are caught near
or at the lake bottom. Most trout-perch mature at age 2, although our data
and other sources (House and Wells 1973; Magnuson and Smith I963; Kinney I950)
show some yearlings are sexually mature.

179

SPOTTAIL SHINER

1977

t978 1979
TERR

1980

SEINES

STATION P

STATION Q

STATION R

10

J-^

••

^

♦

/ ^

/

8

/

>-

/ -^

c

o

/ X

►-

/ y/^

I4i

X

8

-J

/ y^

^

/ y^

"^

o

U

z

cc

Ui

s

o

2

oc

H-

Ul

z

a

Ui

u

1 1 1

1978

1979
YEAR

1980

BOTTOM GILL NETS

STATION C (REFERENCE)

STATION L (PLANT)

Fig. 56. Geometric mean number plus one of spottail shiners caught
in seines at beach stations P (south reference) , Q (south discharge)
and R (north discharge) and in bottom gill nets at stations C (6 m,
south) and L (6 m, north) near the J. H. Campbell Plant, 1978
through 1980« Graphs illustrate the YEAR X STATION interaction o

ISO

Trout-perch was consistently one of the most common fish species in Lake
Michigan in the vicinity of the Campbell Plant from 1977 through 1980. Trout-
perch comprised approximately 1.1% of the total adult and juvenile catch in
Lake Michigan in 1977» slightly more than 2% of the catch in both 1978 and

1979 and about 3*5% of the catch in I98O. Catch of trout-perch adults and
juveniles over the years 1977 through I98O totaled 737^ fish. About 35% (2600
individuals) of this total was comprised of yearlings and about 64% (4727
individuals) of these fish were adults (age 2 or older); a few YOY {kj fish)
were also caught. All YOY and over 90% of the yearlings and adults were
caught in trawls; remaining adults were caught in seines or gill nets, while
the rest of the yearlings were seined.

Larvae —

Although trout-perch yearlings and adults were very common, trout-perch
larvae were relatively uncommon in the study area. The trout-perch is not a
very prolific spawner and has relatively low fecundity, which undoubtedly
partially explains the low catch of larval trout-perch. Egg counts per female
performed by Lawler (1954) ranged from 240 to 728 with a mean of 349- A
prolonged spawning season for trout-perch may also contribute to relatively
low larvae densities of this species. Trout-perch larvae apparently are
demersal; of the 44 specimens collected during 1977 through 1980, 37 (or about
84%) were collected in sled tow samples. These larvae were apparently not
susceptible to the majority of our sampling gear. Larvae were mainly
collected at depth contours of 6 m or deeper; only seven were collected
inshore (beach to 3 »") •

The first 2 yr of sampling effort (1977-1978) yielded only five trout-
perch larvae from Lake Michigan. In 1979f H larvae were collected, while in

1980 28 were taken. The higher incidence of larval trout-perch in 1979 and
1980 may be related to construction activity as well as the resultant riprap
structures providing suitable spawning habitat.

In 1977 three larvae were collected, all with the sled. A 15"mm specimen
was caught at station F (15 m, south) in late July. A 6-mm larva was caught
at station J (3 m, north) and a 10-mm one at station L (6 m, north), both
during September 1977* Jude et al. (1979b) and Fish (1932) reported the
length of hatching of trout-perch to be between 5-5 and 6.0 mm. Eggs hatch in
a few days after fertilization (Scott and Crossman 1973)- Thus in 1977 trout-
perch were still spawning in the study area during September. In I978 two
larvae were collected in Lake Michigan: a 6.8-mm larva at station W (I5 nt,
north) in late August and a 6.0-mm larva at station B (3 m, south) in
September. Appearance of this newly hatched trout-perch indicates trout-perch
spawning extended into September of 1978 as well.

In 1979 two trout-perch larvae were captured in April (each between 6 and
7 mm TL) ; one occurred at the south transect beach station and one was found
at station D (9 m, south). In early August three larvae (7-5 to 12.8 mm) were
caught at station L (6 m, north), and a 5«7-nim larva was captured at station E

181

Table 31. Analysis of variance summary for spottail shiners caught in
seines at stations P (south reference), Q (south discharge) and R (north
discharge) near the J. H. Campbell Plant, eastern Lake Michigan, 1977
through 1980. Data for June through November were analyzed.

Attained

Source

of

significance

variation

df

Mean square

F-statistic

level

Year

3

U.5163

22.9732

<0.0001«<^

Month

U

8.1834

41.6263

<0.0001*«

Station

2

2.5752

13.0994

<0.0001*=>

lime

1

0.0744

0.3787

0.5395

Y X M

12

1.6998

8.6463

<0.0001«*

Y X S

6

0.1385

0.9591

0.4560

M X S

8

>0.919 5

4.6775

0.0001«=»

Y X 1

3

0.0942

0.4793

0.6973

M X T

U

1.5958

8.1175

<0.0001*«

S X T

2

0.0806

0.4099

0.6646

Y X M X

S

2U

0.6206

3.1580

<0.0001*«

Y X M X

T

12

1.8110

9.2122

<0.0001*«

Y X S X

T

6

0.5325

2.7087

0.0168

M X S X

T

8

0.5808

2.9544

0.0047*

Y X M X

S X T

2U

0.4537

2.3077

0.0016*

Within cell

error

120

0.19C6

«« Highly significant (P < 0.001)
« Significant (P < 0.01) .

Table 32. Analysis of variance summary for spottail shiners caught in
bottom gill nets at stations C (6 m, south) and L (6 m, north) near the
J. H. Campbell Plant, eastern Lake Michigan, 1977 through 1980. Data
for July through September and November were analyzed.

Attained

Source

of

significance

variation

df

Mean square

F-statistic

level

Year

3

2.0248

39.4046

<0.0001**

Month

3

2.1267

41.4259

<0.0001*«

Station

1

0.2334

5.5147

0.0220

Tine

1

9.2305

179.6337

<0.0001«

Y X M

9

0.8959

17.4341

<0.0001«*

Y X S

3

0.5269

10.2533

<0.0001«

K X S

3

0.1464

2.8481

0.0444

Y X T

3

1.0723

20.8680

<0.0001«

M X T

3

0.1874

3.6469

0.0171

S X T

1

0.0062

0.1193

0.7303

Y X M X

S

9

0.4005

7.7943

<0.0001**

Y X M X

T

9

1.7038

33.1580

<0.0001«=»

Y X S X

T

3

0.1215

2.3651

0.0792

M X S X

T

3

0.2504

4.8734

0.0041*

Y X M X

S X T

9

0.4015

7.8130

<0.O001«

Within i

sell

error

64

0.0514

«* Highly significant (P < 0.001).
« Significant (P < 0.01) .

182

Table 33. Analysis of variance summary for spottail shiners caught in
bottom gill nets at stations C (6 m, south) and L (6 m, north) near the
J. H. Campbell Plant, eastern Lake Michigan, 1978 through 1980. Data
for May through October were analyzed.

Attained

Source

of

significance

variation

df

Mean square

F-£tatistic

level

Year

2

0.7'4U3

13.3654

<0.0001**

Month

c

1,692U

30.4347

<0.0001«

Station

1

0.0556

0.9994

0.3208

Time

1

18.0707

324.9602

CO.OOOl**

Y X M

10

0.86S1

15.5572

<0.0001««

Y X S

2

0.0257

0.4625

0.6315

M X S

5

0.4105

7.3811

<0.0001**

Y X T

^
^

0.aao3

7.9170

0.0008>>«

M X T

5

0.7529

13.5399

<0.0001**

S X T

1

0.0322

0.5794

0.4490

Y X M X

S

10

0.4300

8.6323

<0.0001**

Y X M X

T

10

2.2130

39.7958

<0.0001«*

Y X S X

T

2

0.0389

0.6998

0.5000

M X S X

T

5

0.247U

4.4493

0.0014*

Y X M X

S X T

10

0.3387

6.0909

<0.0001**

Within cell

error

72

0.0556

»>« Highly significant (P < 0.001).
* Significant (P < 0.01) .

Table 34. Analysis of variance summary for spottail shiners caught in
bottom gill nets at stations C (6 m, south), D (9 m, south), L (6 m,
north) and N (9 m, north) near the J. H. Campbell Plant, eastern Lake
Michigan, 1980. Data for May through October were analyzed.

Attained

Source

of

significance

variation

df

Mean square

F-statistic

level

Month

5

2.7195

47.8277

<0.0001«

Area

1

0.0689

1.2115

0.2765

Depth

1

1.1206

19.7076

0.0001«

Time

1

10.1230

178.0341

<0.0001**

M X A

5

1.0045

17.6657

<0.0001*«

M X D

5

0.5675

9.9815

<0.C001**

A X D

1

0.0658

1.1580

0.2873

M X T

5

0.7420

13.0499

<0.0001**

A X T

1

0.0420

0.7380

0.3946

D X T

1

0.0512

0.8996

0.3476

M X A

X

C

5

0.0798

1.4033

0.2400

M X A

X

T

5

0.1542

2.7114

0.0309

M X D

X

T

5

0.2982

5.2445

0.0006'»«'

A X D

X

T

1

0.0014

0.0242

0.8771

M X A

X

D X T

5

0.2731

4.8029

0.0012*

Within

I cell

error

48

0.0569

««• Highly significant (P < 0.001).
* Significant (P < 0.01) .

183

9n

us T

= X 6-1

I-
uj tr

SPOTTAIL SHINER

STATIONS C AND D
(REFERENCE)

STATIONS L AND N

(PLANT)

1978

1979
YEAR

1980

Fig. 57. Geometric mean number plus one of spottail shiners caught in
trawls at stations C (6 m, south), D (9 m, south), L (6 m, north) and N
(9 m, north) near the J. H. Campbell Plant, eastern Lake Michigan, I978
through I98O. Graph illustrates the YEAR x AREA interaction.

(12 m, south). Five larvae, ranging in length from 6.8 to I9.O mm, were
identified in samples from September 1979? one at the south transect 9-m
station and one each at 3, 9, 12 and 15 m on the north transect.

In 1980 10 larvae (7.5 to 9-5 mm TL) were collected during early July in
sled tows from 6 to I5 m along the north transect. In late July six larvae (6
to ]k mm) were captured at 6- to 9-m contours at the north transect. Eight
trout-perch larvae (lengths of 6.2 to 20 mm) were identified in early August
samples from 6 to 12 m from both transects. In late August one larva (7.0 mm)
was collected from station A (I.5 m, south) and a 7.0-mm specimen from station
B (3.0 m, south). A 10-mm specimen was collected from beach station Q (south
of discharge) and an 8.5"»nm larva was collected from station B; both were
caught in sleds in September. As for 1977 through 1979, larvae data for I98O
indicate the spawning season for trout-perch extended through late August and
probably early September. Densities of trout-perch larvae in Lake Michigan
ranged from 8 to 337 individuals/1000 m^ for the years 1977 through I98O.
Trout-perch larvae appear to be avoiding sampling gear during the day as only
6 larvae were caught during the day while 38 larvae were caught at night.

184

Table 35. Analysis of variance summary for spottail shiners caught in
trawls at stations C (6 m, south) and L (6 m, north) near the J. H.
Campbell Plant, eastern Lake Michigan, 1977 through 1980. Data for June
through December were analyzed.

Attained

Source

of

significance

variation

df

Mean sc^uare

F-statistic

level

Year

3

1.3414

22.9666

<0.0001**

Month

6

1.9620

33.5935

<0.0001«*

Station

1

1.9105

32.7109

<0.0001««

lime

1

33.1955

568.3696

<0.0001«*

Y X M

18

1.8135

31.0513

<0.0001**

Y X S

3

0.2255

3.8608

0.0114

M X S

6

0.0750

1.2848

0.2700

Y X T

3

0.5961

10.2058

<0.0001*«

M X T

6

2.0880

35.7500

<0.0001**

S X T

1

0.2809

4.8095

0.0304

Y X M X

r

18

0.1645

2.8171

0.0005**

Y X M X

i

18

0.4901

8.3912

<0.0001*«

Y X S X

T

3

0.0241

0.4129

0.7441

M X S X

I

6

0.0477

0.8174

0.5586

Y X M X

S X I

18

0.1179

2.0193

0.0139

Within cell

error

112

0.0564

«♦ Highly significant (P < 0.001).
* Signif icani- (P < o.oi) .

Thirty-three of the kk trout-perch larvae were collected from the north
transect. The Wilcoxon signed ranks test for larval density data for I98O
showed a tendency for densities of trout-perch larvae at the north transect to
be higher than those at the south transect; this difference in densities
between transects was significant at a * .05 (the attained significance level
for the test was .0229). Trout-perch may have been attracted to the riprap
for spawning and thus larvae were more concentrated along the north transect
than at the south transect. Most riprap was deposited by the close of the

1979 season.

In summary, trout-perch larvae are relatively uncommon in the study area.
They were collected from April to September, with most being caught in June
and July. They were collected mostly in water 6 m deep or deeper and almost
all were caught in sleds. Larvae apparently are benthic. More were caught in

1980 than any other year. More trout-perch larvae were caught at the north
transect than at the south transect.

Although no fry were collected in 1977 or 1978, 21 trout-perch fry (30-57
mm) were captured during 1979 and I98O in Lake Michigan. All but one of these
fry were caught in sled tows (one was caught in a plankton net towed near

185

Table 36. Analysis of variance summary for spottail shiners caught in
trawls at stations C (6 m, south) , D (9 m, south) , L (6 m, north) and N
(9 m, north) near the J. H. Campbell Plant, eastern Lake Michigan, 1978
through 1980. Data for May through December were analyzed.

Attained

Source

of

significance

variat;

ion

df

Mean square

F-statistic

level

Year

2

4.8385

61.5432

<0.0001**

Month

7

2.0410

25.9607

<0.0001««

Area

1

1.9598

24.9282

<0.0001*«

Depth

1

0.4217

5.3642

0.0216

Time

1

60.6212

771.0713

<0.0001*«

Y X M

la

2.8509

36.2619

<0.0001««

Y X A

2

0.3047

3.8757

0.0224

M X A

7

0.0526

0.6687

0.6984

Y X D

2

0.7045

8.9614

0.0002**

M X D

7

0.3367

4.9192

<0.0001*«

A X D

1

0.6874

8.7431

0.0035*

Y X T

2

0.5597

7.1188

0.0010*

M X T

7

2.4579

31.2633

<0.0001**

A X T

1

0.3091

3.9314

0.0488

D X T

1

0.7413

9.4295

0.0024*

Y X M

X

A

14

0.2295

2.9196

0.0005**

Y X M

X

D .

14

0.5620

7.1478

<0.0001**

Y X A

X

D

2

0.1741

2.2141

0.1120

M X A

X

D

7

0.0465

0.5915

0.7624

Y X M

X

I

14

0.4619

5.8749

<0.0001**

Y X A

X

T

2

0.0119

0.1518

0.8593

M X A

X

T

7

0.1915

2.4355

0.0206

Y X D

X

T

2

0.5335

6.7860

0.0014*

M X D

X

I

7

0.8882

11.2980

<0.0001**

A X P

X

T

1

0.0234

0.2978

0.5859

Y X M

X

A X

D

14

0.2452

3.1185

0.0002**

Y X M

X

A X

T

14

0.2312

2.9413

0.0004**

Y X M

X

D X

T

14

0.4661

5.9279

<0.0001**

Y X A

X

D X

I

2

0.0082

0.1042

0.9011

M X A

X

X

I

7

0.1888

2.4016

0.0223

Y X M

X

A X

D X T

14

0.0664

0.8445

0.6202

Uithir

I cell

error

192

0.0786

«* Highly significant (P < 0.001) •
* Significant (P < 0.01) •

bottom). These fry were all yearling trout-perch. All were caught between
May and late July. Densities ranged from 17 to 133 fry per 1000 m^. These
"fry" yearlings were not included in any yearling catch statistics.

186

Young-of- the- Year —

A few YOY trout-perch have been caught each year from I977 to I98O
(Fig. 58); all were caught in bottom trawls from August through November.
Catch varied from 3 in 1979 to I6 in I98C. Since YOY trout-perch move
offshore during the summer (Magnuson and Smith I963) , it is likely that most
YOY had already entered offshore water (outside the study area) by the time
they grew to a size at which they were susceptible to the trawl.

First occurrence of YOY trout-perch during our 1977 study was in
September when nine (15-^4 mm) were caught in water 9 to I5 m at the south
transect (Fig. 58), The following month two YOY trout-perch (15-3^+ mm) were
trawled at station F (I5 m, south) and in November 1977 another three (15-34
mm) were caught at station E (12 m, south). Similarly in I978, nine YOY
(15-24 mm) were trawled in September from deeper water stations (9 to 12 m) at
the south transect. That same year in October two YOY (I5-34 mm) were caught
at station F (I5 m, south) and in November three (25-34 mm) were caught at the
9- to 12-m contours at the south reference transect.

In 1979 only three YOY trout-perch were collected; all three (25-44 mm)
were caught at station F (I5 m, south) in October (Fig. 58). Growth of YOY in
1979 may have been slower than in other years of the study because of the
major upwel lings during July; YOY may not have been susceptible to the trawls
unti 1 October.

In 1980 YOY were collected as early as August when six specimens (15-34
mm) were caught: one at station C (6 m, south), one at station D (9 m, south)
and four at station N (9 m, north) (Fig. 58). Growth of YOY was probably more
rapid during July and August in I98O than during those 2 mo in any other year,
since there were no upwel lings observed during those months in 1980, unlike
the 3 previous yr. In September I98O another eight YOY (25-44 mm) were
trawled from 9- to 15-m deep water. In October, another two YOY (35-44 mm)
were captured: one at station E (12 m, south) and one at station F (I5 m,
south) .

All YOY trout-perch were collected at night. These fish may be
effectively avoiding the net during the day.

Year 1 ings —

Yearlings comprised a substantial portion of the total number of trout-
perch collected; over 35% (or 2598 fish) of the 7374 specimens caught during
1977 through I98O were yearlings. Growth of yearlings was analyzed by
examining length-frequency data through the year.

Seasonal distr ibution —

April—During I978 and I98O yearlings (15^74 mm) were collected in the
study area as early as April. Three yearlings were caught in April I978 and
in April I98O, four yearlings were collected.

187

<
o
w

o
o

X
CO

o

q:
yj
ffi

3

1X10^

1x10'
1x10'
1x10^
1x10^
1x10'
1x10'
1x10^
1x10=
1x10'
1x10'
1x10^
1x10=
1x10'

1x10'
1x10=
1x10=
1x10'
1x10'
1x10=
1x10=
1x10'

;5-9n

■YL

- AD-

— AD-

■YL

YL

AO"

— r-
AO

YL

NORTH TRANSECT
1977

JUN

JUL

AUG

SEP

OCT

NOV

DEC

10

20 30 40 50 60 70 80 90 100 110 120 130 140 150 160
TOTAL LENGTH (MM)

Fig. 58. Length-frequency histograms for trout-perch collected during
June - December 1977 and April - December 1978-1980 at north and south
transects. Stations were combined into two groups for the north transect:
beach and 3 m; 6 and 9 m and into three groups for the south transect:
beach, 1.5 and 3 m; 6 and 9 m; and 12 and 15 m. Diel periods and gear
types were pooled. YOY = Young-of-the-year; YL = Yearling; AD = Adult.

188

iG-sn l6-9n ■.i2-i5n

UJ

-J
<

2
o
o

o

UJ

m

1x10*
1x10^
1x10^
1x10' —

10'

ixl
1x10'-

1x10'

1x10'

1x10' =p

1x10'

1x10^-
1x10'

1x10* =p
MO' —
1x10' —
1x10' ■

1x10*-
1x10'-

1x10'

1x10' •
1x10*-

1x10'

1x10^-
1x10' -

1x10*-

1x10'

1x10'-

<10'

1

SOUTH TRANSECT
1977

•YL

AD-

YL

AO

'YL

AD

-YOY

YL

AD-

YOY

YL-

AO-

AO-

JUN

JUL

RUG

SEP

OCT

NOV

10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160
TOTAL LENGTH (MM)

Fig. 58. Continued.

DEC

189

IxiQ'

1x10'

xio' -r

xlO*
xlO'
xlO'
xlO'

<
o

CO

o

X
CO

o

(E
ffi

x10*=F
xlO'-
xlO'-
xlO'

X10*=T=~

xlO'

xlG*-
xlO'-
xlO'-
xlO' -
x10* =
xlO'-
xlO'-
xlO' -
xlO*^
xlO'-
xlQ'-
xlO' ■
xlO*-
x10'-
xlO'-
xlO'-

xlQ*-
xlO'-
xlQ'-
xlO' ■

l-YL h

• AD—)

lo-3n l5-9n

NORTH TRANSECT
1978

1 S *i 'i 1 r

-1 1 r

YL

AD-

-I 1 T T

AD

J J M X

n 1* Y-

.YL

-f T

I

n T-

AD -

YL-

■AD

-| 1 1 T T T-

YL-

.AD

I I

T 1 -T r r r

> AO

-T n \ ! 1 1 1 r

- AD

-r r T r

AD

RPR

^ Y f- , r

HRY

n \ r

JUN

-T r r 1 1 1

■JL

flUG

SEP

OCT

NOV

10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160

DEC

Fig. 58. Continued,

TOTAL LENGTH (MM)

190

1x10' -
MO'-
1x10'-
1x10' -

1x10* =
1x10'-
1x10'-
1x10' -
1x10* =
IxlO^*-
1x10'-
1x10' -
1x10*^
1x10'-
1x10'-
1x10' -

1x10*-

1x10'-

1x10'-

1x10'-

1x10*"

1x10* •

1x10*

1x10'

1x10*^

1x10*-

1x10'-

1x10" ■

1x10*-
1x10'-
1x10'-
1x10' •
1x10*-
1x10'-
1x10'-
1x10' ■

- h-

' AD-

lo-3n l6-9n ii2-i5n
SOUTH TRANSECT
1978

YL

AD.

AO

4L_J^

ii—lt-

AO

AD

-f — ^^

-f — p-

YOY

-YL

AO

■^ ^

[— YOY

YL

,AD--

n ] 1 1 1 r

4 — ^

AO-

-i 1 1 r

l-YU

-¥ H^

AD-

flPR

nflY

JUN

JUL

AUG

SEP

OCT

NOV

DEC

10 20 30 40 50 60 70 80 90 100 110 120 130 140 150
TOTAL LENGTH (MM)

Fig. 58 . Continued.

160

191

'^^^ NORTH TRANSECT

MG^^ 1979

IxlO' —

<
o

O
O

1x10*-
1x10'-
1x10^-
1x10' ■
1x10*-
1x10'-
1x10'-
IxlQ' -

1x10*-
1x10'-
1x10'-
1x10' -

10* =r

X

Ix
1x10'
1x10'
1x10'-

1x10*-
1x10'-
1x10'-
1x10' ■

1x10*-

1x10' —
1x10' —
1x10' —
1x10*

1x10' —
1x10'
1x10'
1x10*

lo-3n i6-9n

1x10'

1x10'

1x10'

AD

1 1 1 r

YL-

-AO-

-r r r f

.YL

AD-

-T r r r 1 r r

I YL -- •

AD

.YL

AD>

i» r^

- YL

- AD-

n 1 r

I

.YL

. ? I I
! i i I

-I r 1*^ r* 1*-

YL

AD

~T I I 1 1 1* r* r-

YL

RPR

4 HflY

JUN

JUL

AUG

-T r 1 r

AD

SEP

..I ^ OCT

T r 1

NOV

AD-

— ' ■' \ \ \ 1 1 1' 1 1* 1 ] ^ ^ ^ , DEC

10 20 30 40 50 50 70 80 90 100 110 120 130 140 150 160
TOTAL LENGTH (MM)

Fig. 58. Contimied.

!92

:x]G'

:xio'

IxlG^
IxlC

<
o

CO

o
o

X

en

UJ

s

1x10' =r
1x10^

1x10' -f
1x10'

1x10* =y
1x10' —
1x10'
1x10'

1x10*-
1x10'-
1x10'-
1x10' -

1x10* =j
1x10' —
1x10'-
1x10' -

1x10* =r"
1x10' —
1x10' —
1x10'
1x10* =T^

1x10'

1x10'-
1x10' —

1x10* =r
1x10'-
1x10' —
1x10' —

3n i5-9n :i2-i5n

lo-

AD 1 SOUTH TRANSECT

1979

AD-

AO'

-YL

AD-

YL

AO

1 1 ! r

YL

4—4

AO

■^ H^

J— YOY

YL

AO

-YL

AD

-1 1 1 r

-AO

RPR

riRY

JUN

JUL

flun

SEP

OCT

: NOV

10 20 30 40 50 60 70 80 90 100 110 120 130 140 150
TOTAL LENGTH (MM)

Fig. 58 . Continued.

193

DEC

160

:o'=r"

YL 1-

_J 1 J—

. AD-

H

NORTH TRANSECT
1980

YL-

. AO

PP=

J I L

YL H

AD

, rq-'

Ix'O'-

YL

AO

u Ix _

CO

9 'xlG'

3 1x^0'

X 'y:c

CO

_> h-YOY

U]Q'--

YL

AO.

-Hi • * 1 |l 1 A 1 A ■ ,'

0^ -i l-YOY

01 ■' -

I ix'C

:x:o'-

1x10'-

hYL

YL 1 AO I

AO

-I J Li ij

|-YL AO

._ RUG

IxiG'

^ 20 40 50 80 :00 '20 140 160 180

TOTAL LENGTH (MM)

Fig. 58. Continued.

19^

<
o
en

2
o

o

-J

;xio' ■

IxlC-
1x10' -^-
1x10*-
1x10'-
1x10'-
1x10' -

ixlO*-
IxlO'-
;xlO^-
1x10' —

;xlO*=T="
1x10' —
1x10' —
1x10'
1x10* =p"

1x10'

1x10'
1x10' —
1x10* =
1x10'-
1x10'-
1x10' —

1x10* =p

1x10'

1x10' —
1x10*
1x10* =p"

1x10'

1x10'

1x10' —

1x10* =r
1x10'-
1x10' —
1x10'

SOUTH TRANSECT
1980

lo-3n !5-9n ;i2-i5n

K

YL

-AD

n 1 1 H

-f 1 1 f-

I r

►YL

AD

YL

AO

YL

AD

YOY

YL

AD

(—YOY

YL-

AD

fYOY

YL

AD

i_x

.YL

AD-

10 20 30 40

50 60
TOTA L

-T —

70

RPR

nflY

JUN

V JUL

RUG

.: SEP

DCT

NOV

Fig. 58 • Continuea.

80 90
L PNGT H

195

100 lie

(MM)

-S f ^ r-

12c 130 140 150 160

DEC

May — Catch of yearlings was fairly high during 1979 and I98O (with 99 and
li+8 fish caught, respectively), but low throughout 1978. The 1977 year class
was apparently relatively weak. Yearlings ranged in size from 25 to 5^ ^^
(modal -length interval of 30 mm) in 1978, 15 to 5^ nfim (modal -1 ength interval
of 40 mm) in 1979 and 1 5 to 64 mm (modal -length interval of 50 "im) in 1980.
Almost all yearlings were trawled; only a few were seined during the k yr
study. Gill net meshes are too large to catch yearlings, as none were taken
in this gear from 1977 through I98O.

In 1978-1979 yearlings were caught mainly at 9 ni or deeper (Fig. 58); in
1979 some were caught at station L (6 m, north). They were caught during the
day from 6 to 15 ni and at night from 3 to 15 ni- In I98O yearlings were again
most common at 9 ni and deeper and at station L (6 m, north); during the day
trout-perch yearlings were caught from 12 to 15 m and at night from the beach
to 15 m. About half the yearlings (76 individuals) in May I98O were caught at
station N (9 m, north) .

Substantial populations of yearlings during the k yr 1977 through I98O
were just entering the inshore area during May. Yearlings seem to accompany
adults inshore during the spring and summer. Some trout-perch yearlings are
sexually mature so their movement in the study area could be associated to a
limited extent with spawning.

During May, as throughout the study period 1977 through I98O, trout-perch
exhibited a pronounced diel migration characterized by a movement to shallow
areas at night and a return to deep water during the day. Night catches were
consistently higher than day catches. This migration was consistent for both
adults and yearlings throughout the period of study; there were few exceptions
to this pattern. Indeed, the difference between day and night catches was
more pronounced for trout-perch than for any other major species, and the
ANOVA test (see RESULTS AND DISCUSSION, Trout-Perch , Plant Effects) for diel
period differences in trawl catches for trout-perch showed this time-of-day
factor to be the most significant of all the factors tested for all major
species. Net avoidance may also be partially responsible for low day catches.

Few trout-perch were caught in seine hauls throughout 1977~1980. Trout-
perch did not prefer the beach zone, but seemed to prefer 6- to 12-m water.
Trout-perch (yearlings and adults) feed chiefly on benthos, particularly
chironomid larvae and amphipods (Jude et al . 1979b). Mozley (1975) found that
chironomid larvae and amphipods were sparse in the 0- to i^m zone compared
with populations of these organisms farther offshore. Perhaps trout-perch
were most common between 6 and 12 m when occupying the inshore area during
spring and summer in response to location of food. Competition for food from
spottail shiners and yellow perch in the beach zone may also limit trout-perch
abundance there.

June — Catch of yearlings (25-64 mm, 50-mm modal-length interval)
increased from 149 in May I98O to 205 in June 1980. Catches in June for both
1978 and 1979 were lower than the respective May catches with 59 yearlings
caught in June of each year; however, in 1977 yearling catch was near a peak
in June at 152 fish. Yearlings ranged in size from 25 to 64 mm in June for

196

all 4 yr. The June modal -length interval was 50 mm for all k yr except in
1979 when it was kO mm. Yearlings were generally caught from 9 to 15 m during
the day and from the beach to 15 m at night, except for a total of 10
yearlings caught during the day in the beach zone in 1978 and I98O.

In June yearlings were most common between 6 and 12 m. Again, high night
catches and very low day catches indicated a migration of trout-perch into the
study area at night and back to deeper water during the day. Net avoidance
probably also contributed to low day catches.

July — July marked an influx of yearlings into the study area during 1977»
1979 and 1980, Catch of yearlings peaked in July I98O at 351 individuals, at
275 fish in July 1979 and at I92 fish in July 1977; the 1978 yearling catch
(25"64 mm, 40-mm modal-length interval) was relatively low throughout the
year. In both 1979 and I98O lengths ranged from 35 to 7^ nim with a 50-mm
modal -length interval, while in 1977 yearlings (^5"7^ 'nni, 60-mm modal -length
interval) were slightly larger than in 1979 or I98O. Yearlings were caught
from 6 to 15 ni during the day and night with most trawled between 6 and 12 m
(Fig. 58). High catches of yearlings occurred at station N (9 m, north) in
1979 and at station L (6 m, north) in I98O. Reasons for these relatively high
catches of yearlings are not clear. The high catch in 1979 occurred during an
upwelling, while in I98O the catch was taken at a fairly high water
temperature (21.0 C) . Yearlings may have been attracted to the north transect
to feed on organisms stirred into the water column by construction activity.

August — Catch of yearlings declined considerably from July to August with
148 individuals caught in 198O, 146 in 1979 and 58 in 1977- In 1978 catch of
yearlings (35*7^ nwn TL, 50-mm modal -length interval) increased slightly from
kS individuals in July to 62 individuals in August. During August yearlings
ranged in length from 35 to 84 mm in 1979 (60-mm modal-length interval), and
the modal -length interval was 70 mm in 1977 and I98O. Yearlings in I98O grew
substantially from July to August with the modal-length interval increasing
from 50 mm to 70 mm; this was the highest growth of yearlings shown for any 2
consecutive mo during the 4-yr study. In I98O no upwel lings were observed
between July and August, while upwel lings occurred in July during 1977 through
1979* A major upwelling occurred in July 1979f followed by somewhat lower
than average water temperatures for August 1979; this may explain the lower
growth shown by yearlings during 1979-

Yearlings in August were caught from 6 to 15 m during the day and from
the beach to 15 m at night. In August as for most months during 1979. most
trout-perch (both yearlings and adults) were caught at 9- to 12-m stations on
the south transect and at 6 to 9 m on the north transect. For the other 3 yr
(1977. 1978 and 1980) most trout-perch were caught at stations mentioned above
plus the 6-m station on the south transect. Yearlings migrated toward shore
at night and toward deeper water during the day; the only exception to this
pattern was a relatively high day catch of yearlings at station N (9 m, north)
in 1979.

197

In August 1980 substantially more trout-perch (yearlings and adults) were
caught at the south transect 6- to 9"ni stations than at the complement of
those stations at the north transect (Fig. 58). Reasons for this difference
are not clear. During most of 1979 (including August) catch at north transect
stations was substantially higher than at south stations (see RESULTS AND
DISCUSSION, Trout-Perch , Plant Effects).

September — Catches of yearlings (45-9^ niin, 70-mm modal-length interval)
continued to decline through September 1979 when 8l individuals were caught
(Fig. 58). However, catch increased from August to September both in 1977 and
1980. Of the 309 yearlings (i+5"'9^ nim, 80-mm modal-length interval) caught in
September 198O most were trawled at 12- and 15"ni stations on the south
transect, particularly at 15 m- During September 1977 most of the 101 trout-
perch yearlings caught were captured at the south transect at depths of 9 and
12 m (Fig. 58). High catches in deeper water in 1980 indicate that offshore
migration of trout-perch yearlings may possibly have begun by sampling time in
September. Abundance of yearlings and adults in the Cook Plant study area
declined in September in southeastern Lake Michigan (Jude et al . 1975)* The

1979 catch data for the Campbell Plant area indicated a movement toward
offshore beginning in August and continuing through September. Apparently in
1977 offshore migration of yearlings started in late September or October. In
September 1978, the yearling (45-7^ »nni) migration probably began in September.
In 1978 and 1979 most yearlings were caught between 6 and 12 m (note that in
1977 two yearlings were trawled in water between I8 and 21 m at the south
transect) .

Yearlings grew substantially through September. House and Wells (1973)
found mean lengths of yearlings were 49 mm in June and 83 nim by the end of
their second year of life in southeastern Lake Michigan. For our study area
in both 1977 and I98O yearlings reached a mode of 50 mm in June and 80 mm in
September. In 1979 yearlings reached a modal -length interval of 40 mm in June
and 70 mm in September. In July 1979 and I98O the modal -length interval was
50 mm. Growth apparently was slightly lower in 1979 than I98O due to lower
water temperatures in July and August 1979-

October, November and December — Most yearlings had left the study area by
October. Catch declined drastically from September to October during 1977 and

1980 when only eight yearlings (65"'94 mm) were caught in October during each
of those years. In 1979 catch of yearlings (55"9^ mm) also declined in
October with 43 individuals caught, while in 1978 no yearlings were caught in
October. It appeared that migration to the offshore area was more gradual in
1979 than in other years. Yearlings were chiefly caught from 9 to 15 m during
the day and 6 to 15 m at night. One yearling in 1979 was caught in a seine
haul at beach station P (south reference) and six were trawled at station H
(21 m, south) in 1977-

Only a few yearlings were caught in November and December indicating that
almost all yearlings had left the study area by November. Only I3 yearlings
were caught during these 2 mo over the 4-yr study period. All were collected
in 6 m or deeper water.

198

Adul ts--

Adults (2-yr or older) comprised about 64% of the total adult and
juvenile catch for the years 1977 through 1980 pooled. Annual adult catch was
in general greater than that for yearlings. Adults include several age-groups
while yearlings include just one; this partially explains the difference in
catch between yearlings and adults. Furthermore adults are in the inshore
waters (and thus susceptible to our sampling effort) by May; whereas, the
yearling population does not show peak occurrence inshore until July. Also a
small population of adults tends to stay in the inshore waters through fall,
while almost all yearlings have migrated from the study area by October.

The annual total adult catch was highest in 1978 and 1980 with 1626 and
1694 trout-perch caught, respectively. Adult catch was lower in 1979 (1043
fish) and substantially lower in 1977 (366 fish). The annual yearling catch
was highest in I98O (1175) and lowest in 1978 (only 201 fish). Yearling fish
catch in 1977 was 5^3 fish, and 709 yearlings were caught in 1979. Total
adult and juvenile catch was highest in 1980 (2885 fish); the I98O total catch
was considerably greater than that for I978 (l84l fish), I979 (1755) or 1977
(893 fish). However, this increase in I98O total catch does not imply a trend
of increasing trout-perch populations in the Campbell Plant vicinity of Lake
Michigan but rather a high catch year in a series of fluctuating catches.
Note that adult catches for 1978 and I98O were about equal.

Seasonal distr i but ion —

April — April marks some adult trout-perch spring migration inshore in
Lake Michigan. Catch data indicate only a few trout-perch migrated into the
study area by sampling time in April for 1978 through I98O (Fig. 58). Eight
adults (65-114 mm) were caught in I978 and four adults (95-124 mm) were caught
in 1979; seven of these adults were seined, two were trawled and one was
caught in a bottom gill net. In I98O, 2 adults were caught in bottom gill
nets between 6 and 9 m and 25 were trawled between 3 and 12m.

All adults collected in April had well developed gonads, except for two
in 1978. These two, a ripe-running male and a ripe-running female, indicated
trout-perch began spawning that year in April. In April I979 a trout-perch
larva (6.5 mm TL) was collected in a larvae tow sample indicating that
spawning also began in April during 1979-

May — Migration of adult trout-perch inshore increased dramatically from
April to May. Indeed catch of adults was at its peak in 1979 and I98O (catch
of 341 and 322, respectively) and near its peak in I978 (308 adults). Adults
(65-164 mm) were caught from the beach zone to I5 m with most trawled from 6
to 12 m (Fig. 58) .

Spawning activity increased during May from April levels as more fish
with well developed and ripe-running gonads were caught; this was consistent
for 1978 through I98O (Fig. 59). Spent individuals were also collected in May
from 1978 through I98O.

199

120-

80-

40

Q

UJ

O

120

O 80-
O

^ 40-

3

2 80i

O 40

UJ
CD

120

80

40

NO

N>3

Ns4

N = 2I

NO

N=303

1977

■ 'WELL DEVELOPED AND
RIPE- RUNNING GONADS

n«SPENT GONADS

Nsl37

Ns94

N = 54 H_ Ns8l

■-. In tfn

Ns34

1978

N:266

N«I73

1979

Ns205

N«79

L

N = 236 Ns260|98

Ns234 N = I42

Ns40

I

N*20 N'S3 N'I9

N:I2I N<I02 N'TO

N<44 N<3

APR MAY JUN JUL AUG SEP OCT NOV DEC

SAMPLING PERIOD

Fig. 59. Number of mature trout-perch with well developed, ripe-running
and spent gonads collected monthly during June-December 1977 and April-
December 1978-1980 near the J. H. Campbell Plant, eastern Lake Michigan.
N - total number of mature trout-perch caught per month.

200

Length of age-2 fish ranged from approximately 65 to ]0k mm and age-3
fish ranged from 95 to 124 mm each May during 1978 through 1980, Age-2 fish
were separated from age-3 fish based on length-frequency data and by
comparison with data from the study by House and Wells (1973) t who aged fish
by reading scales.

Numbers of adults caught in May during 1977 through I98O were similar;
however, the percentage that age-2 adults comprised of the total number of
adults caught, varied considerably among years. In 1978 over 80% of the
adults were 2-yr-old fish. These fish were members of the strong 1976 year
class noted by Jude et al. (1978, 1979a)- This year class was apparently the
strongest year class observed during the 4-yr study. The 1979 adult catch
consisted largely (about 50%) of 3"yr-old fish which again were
representatives of the strong 1976 year class. Evidently the 1976 year class
survived the 1978-1979 winter well and was present in relatively high numbers.
The number of age-2 fish collected in 1979 was not as high as in 1978; these
1979 age-2 fish represented the relatively less abundant 1977 year class.
Whereas the yearling age-group was relatively small in 1978, there was a high
catch of yearlings in 1979 suggesting a relatively more successful 1978 year
class compared with 1977* Most trout-perch mature at age 2 (House and Wells
1973) so the 1976 year class was probably the major parent stock for this 1978
year class. In May I98O age-2 adults represented over 55% of the total adult
catch. As in 1979» age~3 adults were well represented in I98O suggesting high
survival of age-2 fish over the 1979"1980 winter. Although there seemed to be
some correlation between parent stock and year-class strength, Magnuson and
Smith (1963) found environmental conditions, such as water temperature and
wind velocity, more important than size of the parent stock in determining
year-class strength of trout-perch in Red Lakes, Minnesota.

June — High adult catches were recorded in June during 1977 (17^ adults),
1978 (393 fish) and I98O (3 15 fish). Both yearling and adult catch declined
from May to June during 1979 with only 78 adults caught in June 1979* Reasons
for this decline are not known. There was no upwelling at sampling time which
could have affected trout-perch distribution. Bottom temperatures for
trawling ranged from ]k to 17 C.

Adults {65 nim or greater) were caught from 3 to I5 ni during the day and
from the beach to 15 m at night (Fig. 58). Most adults were trawled, but 30
were seined in June and 22 were caught in bottom gill nets during 1977 to
1980. Most trout-perch were caught at night in bottom gill nets, when
migrati ng i nshore.

In June trout-perch (adults and yearlings) were most common between 6 and

12 m; however, in I98O a substantial adult catch was taken from station B (3
m, south). Similar to the pattern exhibited by yearlings, high night catches

and very low day catches illustrated a migration of trout-perch into the study
area at night and into deeper water during the day. Again, there may be some

net avoidance during the day. Three adults were trawled at stations I8 to 21
m at the south transect in June 1977.

201

June was the peak spawning month each year from 1977 to 1980, which
coincides with peak catch or near peak catch (in the case of I98O) for all
years except 1979 (Fig- 59)* During all years except 1979 more trout-perch
with well developed or ripe-running gonads were caught in June than any other
month of the sampling year. For 1979 gonad data suggest a spawning peak in
June despite the unusually low number of adults caught (Jude et al . 1980). The
spawning peak in 1979 "lay have occurred just before our sampling period in
June with most adults leaving the vicinity immediately after spawning.

Adults can suffer high mortality after spawning (Scott and Grossman
1973); however, age-3 fish were well represented in I98O so this die-off
probably did not occur in 1979- Scarcity of individuals 3""/^ old or older
(100-160 mm) in May in the 1977 and I978 collections tended to corroborate
high mortality of adult trout-perch (age 2 or older) in 1976 and 1977* We
have not observed die-offs of trout-perch nor have die-offs been observed in
southeastern Lake Michigan (Jude et al . 1975)-

July—Adult trout-perch catch was high in I978 (308 fish), in 1979 (239
fish) and 1980 (275 fish). Adult catch was low in July 1977 (29 fish) as it
was throughout 1977* Adults were caught from 6 to 15 m during the day and
from 3 to 15 ni at night (except for three adults in the beach zone in 1978).
Few trout-perch were caught in bottom gill nets in July.

Most trout-perch were trawled at stations 6 to 15 ni at the south transect
and 6 to 9 m at the north transect (Fig. 58). In July 1979 adult catch at
station C (6 m, south) was relatively low. Again catch data indicate a
migration of adults and yearlings shoreward at night and into deeper water
during the day. However, there were relatively high adult day catches at
station N (9 m, north) in 1979 and at station L (6 m, south) in I98O.

Spawning activity appeared to be high through July, but had declined
somewhat from June levels (Fig. 59). For 1979* data showed a secondary
spawning peak in July. In June 1979 a higher percentage of mature (well
developed, ripe-running or spent gonads) fish were collected than in July
1979; however, the number of mature fish collected was greatest in July during
1979* Peak spawning occurred in July in the Cook Plant vicinity during 1973
and 197^ (Jude et al . 1979b).

August— Catch of adults was high in August 1978 (338 fish) and 198O (275
fish). Catch in 1977 was low (7I fish). In 1979 adult catch declined
substantially between July and August; apparently migration offshore had begun
as early as August. A major upwelling in July followed by comparatively cool
water temperatures in August (Fig. 22) may have triggered this earlier
migration offshore. Adults were collected from the beach to 15 ^ at night
(with two adults caught between I8 and 21 m in 1977) and from 9 to 15 m during
the day. Again most were caught from 6 to 12 m at the south transect and 6 to
9 m at the north transect. In August I98O there was a considerable catch of
trout-perch from station B (3 m, south) (Fig. 58). Also during August 198O
there was a substantially greater catch of trout-perch at the south transect
than the north. Reasons for this difference are unclear.

202

Spawning activity declined from July to August during I978 through I98O
(Fig. 59). During 1977 a secondary spawning peak occurred in August with a
few ripe-running individuals caught. Gonad data were not strong indicators of
continued spawning in August 1978, 1979 and I98O. However, newly hatched
larvae collected during August and September suggest spawning continued
through late August and probably early September.

Again adults migrated shoreward at night and towards deeper water during
the day; however, there were a few relatively large day catches of adults.
These included day trawls at 9 and 12 m at the south transect during I98O.

September — Adult catches declined from August to September during 1977
through 1979- Migration offshore had begun by sampling time in September. In
1979 migration of adults offshore was well underway in September, probably
having begun in August. This movement offshore appeared to have just started
by September during I98O. Although adult catch increased slightly from August
to September in I98O (293 adults caught), most fish (over 50%) were caught at
station F (15 m, south) and about 35% were taken at station E (12 m, south) .
These high catches from deeper water signalled the start of the adult
migration offshore. Generally, in September adults were found from 6 to 15 m
during the day and from the beach to 15 m at night during all years 1977
through I98O (Fig. 58) .

October, November and December — Apparently a small population of adult
trout-percn remained in the study area during fall months (Fig. 58). Monthly
catches of adult trout-perch ranged from 20 to 139 fish during the 4-yr study
for October and from kO to 68 fish for November. Adults were caught only at
15 m during the day and from the beach to 15 ni at night. Their movement
inshore at night and offshore during the day was still evident in October and
November. In I98O bottom gill net catch peaked in October with 67 adults
caught. In 1977, I978 and 1979 bottom gill net catch peaked in November with
21, 2k and 39 adults caught, respectively. All trout-perch caught in bottom
gill nets were adults* Five adults were caught in a surface gill net at
station C (6 m, south) at night in November 1979 (one adult was caught by this
gear in May 1978). The trout-perch is considered a benthic species; however,
some move upward in the water column. By December most adults remaining
inshore through fall had left the study area.

Other Cons i derat i ons —

Trout-perch were not found to be an important forage species in various
areas of southeastern Lake Michigan (Jude et al. 1979b; House and Wells 1973) •
During our study from 1977 to I98O, trout-perch were seldom found in stomachs
of predatory fishes. Trout-perch may act as a nutrient transporter in the
study area since they move Into shallow water at night and back into deeper
water by day (Scott and Grossman 1973) •

203

Temperature-catch Relationships —

Trout-perch appeared to tolerate a wide range of water temperatures.
During 1977 through I98O most trout-perch were caught at water temperatures
between k and 22 C i n the study area.

Response of trout-perch to changes in water temperature varied
considerably. In 1977 trout-perch catches i ncreased wi th increasing water
temperatures. In July 1978 an upwelling may have caused a decline in the
number of adults collected compared with June 1978. However, in 1979
increasing water temperatures from May to June did not lead to an increase in
trout-perch catch. Also, when an upwelling occurred in July, more trout-perch
were collected than in June; water temperatures at times of trawling were
considerably lower in July than in June. SCUBA divers observed that trout-
perch seemed unaffected by an internal seiche in Georgian Bay, Lake Huron, and
that the fish continued to feed while moving slowly just above the bottom
(Emery 1970) . These SCUBA observations further support the lack of
temperature preference of trout-perch. In southeastern Lake Michigan, trout-
perch tended to move to warm-water areas at times, but remained indifferent or
were attracted to cool water at other times (Jude et al. 1979b). In 1977
yearling trout-perch tended to occur in cooler water than adults in the
Campbell Plant study area; however, from 1978 through 198O no pattern of
temperature preference was apparent in catch data.

Plant Effects—

To help evaluate Campbell Plant effects on trout-perch, ANOVAs were
performed on trawl data for adult and juvenile trout-perch caught in Lake
Michigan from 1977 to I98O. An ANOVA for just 1977 data, for only the 6-m
stations at the north and south transects (stations L and C, respectively)
showed no significant difference in catches between these two stations (Jude
et al. 1978). The ANOVA for 1977 through I98O trawl data for stations C and L
showed average catch at station L (6 m, north) was significantly greater than
that for 6 m south transect station C (Table 37) • Another ANOVA was performed
on trout-perch adult and juvenile catch data for both the 6- and 9"ni stations
at both transects for I978 to I98O. Results showed that AREA was a
significant main effect and that the YEAR x AREA interaction was significant
(Table 38). Apparently the considerably greater catch at the plant vicinity
than at the reference area in 1979 contributed to the significant AREA effect
and the significant YEAR x AREA interaction (Fig. 60) . Catch in the plant
vicinity was significantly greater than at the reference area, mainly due to
the 1979 catch difference.

During 1979 there was much construction activity in the discharge area
(plant vicinity) and most of the riprap was also being deposited. This
activity may have stirred organisms from the lake bottom making them more
available to yearling and adult trout-perch to feed upon, thus attracting
trout-perch to the plant transect area. With construction activity completed
there probably will be no substantial difference in adult and juvenile catch
between areas in I98I, unless the riprap remains attractive to trout-perch.

20i*

Table 37. Analysis of variance sunnnary for trout-perch caught in
trawls at stations C (6 m, south) and L (6 m, north) near the J. H.
Campbell Plant, eastern Lake Michigan, 1977 through 1980. Data for
June through November were analyzed.

Attained

Source

of

significance

variation

df

Mean square

F-statistic

level

Year

3

0.2522

8.3536

0.0001**

Month

5

2.4533

81.2655

<0.0001**

Station

1

0.3915

12.9682

0.0005**

Time

X

37.6511

1247.1904

<0.0001**

Y X M

15

o.aa32

14.6813

<0.0001**

Y X S

3

0.1520

5.0361

0.0028*

M X S

5

0.2020

6.6696

<0.0001**

Y X T

3

0.2970

9.8379

<0.0001**

M X T

5

0.9659

31.9946

<0.0001**

S X T

1

0.0011

0.0349

0.8522

Y X M X

S

15

0.1306

4.3275

<0.0001**

Y X M X

I

15

0.3139

10.3964

<0.0001*«

Y X S X

T

3

0.1404

4.6507

0.0044*

M X S X

I

5

0.0491

1.6254

0.1606

Y X K X

S X T

15

0.0494

1.6365

0.0782

Within cell

error

96

0.0302

** Highly significant (P < 0.001).
* Significant (P < 0.01) .

Trout-perch larvae data suggest that trout-perch may be attracted to the
riprap vicinity to spawn (see RESULTS AND DISCUSSION, Trout-Perch , Larvae).
Most larvae collected were caught in I98O (28 larvae); many (23 larvae) were
caught at the north (plant) transect. The numbers of larvae caught were too
low to draw a conclusion. If trout-perch tend to spawn near or on the riprap,
operation of the offshore intake will increase the 1981 entrainment loss for
trout-perch over levels observed for Units 1 and 2 during 1978 through I98O.
Losses due to entrainment were relatively low during I978 and 1979-

Un i dent i f i ed Coreqon i nae

I ntroduction —

Throughout the 4-yr study of fish abundance and distribution in
southeastern Lake Michigan the population of fishes in the subfamily
Coregoninae has shown a dramatic increase. Although unidentified Coregoninae
has always been between the fourth- and sixth-most abundant species/group in
our catches, the overall catch has increased from 460 fish in 1977 to 893^ in
1980. The increase in abundance has been accompanied by a change in the
length-frequency distribution of fishes collected. In 1977 unidentified
Coregoninae ranged from about 35 to 29^ nim. Three groups were apparent, those
in the 70* and 80-mm length intervals, those in the 100 to 150-mm length

205

Table 38. Analysis of variance summary for trout-perch caught in trawls
at stations C (6 m, south), D (9 m, south), L (6 m, north) and N (9 m,
north) near the J. H. Campbell Plant, eastern Lake Michigan, 1978 through
1980. Data for May through November were analyzed.

Attained

Source

of

significance

variation

df

Mean square

F-statistic

level

Year

2

0.U669

11.3316

<0.0001**

Month

6

U.3418

105.3659

<0.0001«*

Area

1

0.5383

13.0634

0.0004**

Depth

1

1.4526

35.2512

<0.0001«*

Time

1

57.3189

1390.9978

<0.0001**

Y X M

12

0.3387

8.2191

<0.0001««

Y X A

2

0.5675

13.7713

<0.0001**

M X A

6

0.2125

5.1579

0.0001**

Y X D

2

0.3498

8.4889

0.0003**

M X D

6

0.1619

3.9289

0.0011*

A X D

1

0.2147

5.2111

0.0237'

Y X T

2

0.3600

8.7357

0.0002**

M X T

6

1.0786

26.1754

<0.0001**

A X T

1

0.0217

0.5258

0.4694

X T

1

1.2634

30.6588

<0.0001**

Y X M

X

A

12

0.2657

6.4469

<0.0001**

Y X M

X

D

12

0.4569

11.1365

<0.0001**

Y X A

X

2

0.1327

3.2211

0.0424

H X A

X

D

6

0.0565

1.3709

0.2291

Y X M

X

T

12

0.4022

9.7608

<0.0001**

Y X A

X

T

2

0.0024

0.0574

0.9442

M X A

X

I

6

0.U25

2.7289

0.0148

Y X D

X

1

2

0.1769

4.2940

0.0152

M X D

X

T

6

0.3784

9.1821

<0.0001**

A X D

X

I

1

0.1418

3.4404

0.0654

Y X M

X

A X

D

12

0.2416

5.8626

<0.0001*«

Y X M

X

A X

T

12

0.1009

2.4480

0.0058*

Y X M

X

D X

T

12

0.1459

3.5419

0.0001**

Y X A

X

D X

T

2

0.2101

5.0975

0.0071*

M X A

X

D X

T

6

0.1386

3.3645

0.0037*

Y X M

X

A X

D X T

12

0.0851

2.0641

0.0218

Uithin .

=ell

error

168

0.0412

*<c hUghly significant (P < O.OOl) .
* Significant (P < 0.01) .

intervals and those in the 200- to 250-mm length intervals (Fig. 61). In 1978
most unidentified Coregoninae were between 65 and Sk wm and almost no fish
greater than iSO mm were collected (Fig. 6l) . During 1979 two groups of
unidentified Coregoninae were collected, those in the 70- to 120-mm length
intervals and those in the l60- to l80-mm length intervals. Very few fish
greater than 2i*0 mm were caught (Fig. 6l) . Finally in I98O most fish
collected were within the 60- to 80-mm length intervals, t^.e 17O- and l80-mm
length intervals and, for the first time since 1977, a substantial number of

206

< +

UJ-I

SI

6-1

4-

2-

TROUT-PERCH

STATIONS C AND D

(REFERENCE)

-.STATIONS L AND N
(PLANT)

1978

1979
YEAR

1980

Fig. 60. Geometric mean number plus one of trout-perch caught in trawls
at stations C (6 m, south), D (9 m, south), L (6 m, north) and N (9 m,
north) near the J. H. Campbell Plant, eastern Lake Michigan, 1978 through
1980. Graph illustrates the YEAR x AREA interaction.

fish in the 270- to 310-mm length intervals were collected (Fig. 6I) . The
increase in abundance and the increased number of larger individuals collected
over the 4-yr period are clearly shown in Figure 62.

Trawling was the most effective gear in collecting unidentified
Coregoninae, however each gear used was size-selective and trawl hauls tended
to collect YOY or yearling unidentified Coregoninae in the 30- to 280-mm
length intervals {Tables 39 and 40). Gill nets retained fewer fish but those
that were netted were usually larger, in the 90"" to 310-mm length intervals.
Seining collected numerous small unidentified Coregoninae between kS and Mk
mm (Table kO) . Catches of unidentified Coregoninae were usually greater
during the night than during the day for ail gear types except the seine which
had greater catches during the day. Surface gill net catches of Coregoninae
were made only during the night (Table 39)* Unidentified Coregoninae were
caught at a wide range of water temperatures, 1 to 23 C. This was
particularly true for those fish caught by trawl or bottom gill net. Seining
and surface gill net sets captured fish only when water temperatures ranged
from 9 to 19 C, even though these gear were deployed at temperatures between 3
and 25.7 C.

207

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Q8>N M
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9991 »N H
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8:N HM

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(uiuj) H19N31 IVIOI

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208

1977

*I978

« 1979

»I980

100
TOTA

300

LENGTH

Fig. 62 . Total number of unidentified Coregoninae collected within
each length-frequency interval (pooled over months) in the vicinity
of the J. H. Campbell Plant, eastern Lake Michigan, 1977 to 1980.

209

Table 39- Total number of unidentified Coregoninae collected
by each type of sampling gear in the vicinity of the
J. H, Campbell Plant, eastern Lake Michigan, 1977"1980.

Year
1977 1978 1979 1980
Gear Day Night Day Night Day Night Day Night

Seine 7 3 2 10 250 2

Surface

gill net 07 7 5

Bottom

gill net 37 I8 2 9 87 HO 17^ ^60

Trawl 193 199 1020 2085 1755 371^ 3^67 ^576

Total

catch 237 223 1025 2096 1852 3861 3891 5043

% of

Total 52% kB% 33* 67% 32% 68* kk% 56%

Total

yearly

catch 460 3121 5713 893^

During the 4-yr study period 1,738 unidentified Coregoninae were
collected at beach and nearshore stations less than 3 m deep; 12,3^2 were
collected at 6- and 9-ni inshore stations and 4,124 at 12- and 15"ni stations
(Table 41). These numbers are biased due to differences in sampling gear used
at each station. However, throughout the 4-yr period collections at stations
3 m or less were always less than those at deepwater stations 12 to 15 ni, and
deepwater station catches were always less than those at 6- and 9"ni inshore
stations (Table 41). During I98O all sizes of unidentified Coregoninae were
collected offshore, while collections inshore contained mostly small (less
than 80 mm TL) Coregoninae (Fig. 63). The exceptions occurred in May and
June, when a few larger individuals strayed inshore due to continued cool
water temperatures there (Appendix 8) .

210

Table kO. Length-frequency intervals (mm) of unidentified
Coregoninae collected by each type of gear in the vicinity of the
J. H. Campbell Plant, eastern Lake Michigan, 1977-1980.

Year

Gear

1977

1978

1979

1980

Seine

50-80

50-70

60-100

50-120

Surface

Gin Net

130-280

110-130

120-190

Bottom

Gill Net

150-290

110-240

90-240

100-310

Trawl

40-280

30-200

40-280

50-260

Total 40-290 30-240 40-280 50-310

Gonad condition evaluations revealed that approximately 13% of all fish
collected in 1980 were male, 16% were female, 64% were immature and for 7% of
the fish, gonad condition could not be determined. In I979 and I978 the
respective gonad conditions were: 6% and 1.5% male, 8% and 0.5% female, 82%
and 79% immature and for 4% and 19% of the fish, gonad condition could not be
determined. The population of Coreqonus spp. sampled in the vicinity of the
J. H. Campbell Plant does not seem to be dominated by either sex, however,
mature fish were not abundant until I98O.

Larval Coregoninae have been rare in samples collected near the J. H.
Campbell Plant. Only one larva was collected in 1977, two in I978 and eight
in 1979. However, during I98O, 49 larval Coregoninae were recovered.

Difficulty in identifying species of the genus Coreqonus , particularly
individuals less than I80 mm, has been discussed (Jude et al. 1975, 1978).
Apart from the easily identified Coreqonus clupeaformis . the lake whitefish,
other fish in the genus Coreqonus caught in the vicinity of the J. H. Campbell
Plant are believed to be bloaters, Coreqonus hoyi . Due to problems with
identification, some of these individuals may have been lake herring,
C. arted i i .

In the Great Lakes region Coreqonus hoyi has been reported to spawn
during February and March, usually in water deeper than 36 m (Scott and
Crossman 1973) • Coreqonus arted i i spawn between mid-November and mid-December

211

Table k] . Numbers of unidentified Coregoninae collected (various
stations combined) in the vicinity of the J, H. Campbell Plant, eastern
Lake Michigan, 1977"1980. Station depth is given in parentheses.

^ ta t 1 nn

Depth
Range (m)

Year

Groupings

1977

1978

1979

1980

By transect

A (1.5 m),B(3 m)

1.5-3

36

319

298

811

C (6 m) , D (9 m)

6-9

128

987

1508

2199

E(12 m) ,F(15 m)

12-15

216

522

1016

2370

L{6 m) ,N(9 m) ,U(6 m)

6-9

59*

1288

2881

3302

P(l m),Q(1 m) ,R(1

m)

1

7

5

10

252

By depth

6-9

187*

2275

^♦389

5501

12-15

216

522

1016

2370

18-21

1i»

•

.

.

A (1.5 m),B(3 m),P(1 m)

Q(l m),R(l m) I-3 43 324 308 IO63

C(6 m) .0(9 m) .L(6 m)
N (9 in) . U (6 m)

E(12 m),F(15 m)

G(l8 m) ,H(21 m)

Total number of

fish collected it60 3121 5713 893^^

% of total of

a1 1 species of

fish collected 0.59 5-^2 7-31 10.62

^Stations N and U were not sampled.

212

NEflRSHORE

OFFSHORE

N=

N= 7

N= 776

N=

N=

UJ ^
CJ

cr S

LU
CL

N» 238

46

I

N« 42

i

N=

N»

I ♦ >■■

RPR

♦ > » I >>«♦»<■

nflY

JUN

JUL

I » > »■ I I

AUG

It > I ■ » I > > I

SEP

OCT

NOV

* ♦ t > t t

DEC

N= 2

N= 734

A^

N» 2294

N« 710

N- 595

49

N- 610

N- 1345

54

1

N- 687

S4

N» 894

464S

i

RPR

nflY

JUN

JUL

RUG

SEP

OCT

NOV

DEC

80 160 240 320 400

TOTAL LENGTH (mm)

80 160 240 320 400

TOTAL LENGTH (mm)

Fig. 63. Length-frequency distribution of unidentified Coregoninae
collected by all gear at nearshore stations (beach, 1.5 m, 3 m) and
offshore stations (6-15 m) in the vicinity of the J. H. Campbell
Plant, eastern Lake Michigan, 1980.

213

usually in shallow water less than 10 m (Koelz 1929). The small Coregoninae
(60 to 90 nfim) collected from September to December (Fig. 6I) are most likely
YOY Coreqonus hoy i , resulting from early spring spawning. Since sampling for
adult fish was not conducted in the early months of February and March, adults
with well developed or spent gonads were not collected (Table 42).

Table 42. Gonad conditions of unidentified Coregoninae collected in the
vicinity of the J. H. Campbell Plant, eastern Lake Michigan, 1980.

Gonad Condition Apr May Jun Jul Aug Sep Oct Nov Dec

SI ight development 26 2^+5 5 2 62

Mod. development 52 1 58

Males Well developed 3

Ripe-running
Spent

Slight development 6 258 12 2 42 2
Mod. development I6I 3 72

Females Well developed 3 4

Ripe-running

Spent 1

Absorbing

Immature 2 336 481 240 I88 257 373 190 226

Unable to

distinguish 82 82 31 8 38

Larvae —

Occurrence of larval Coregoninae during the 4-yr study has been rare.
During 1977 and 1978 only three larval Coregoninae from 11 to 14.5 mm TL were
collected. These were taken in June, at deepwater stations F (I5 m, south)
and W (15 m, north). In 1979 eight larval Coregoninae were caught, four in
April at shallow water station A (1.5 m, south) and in Pigeon Lake (Jude et
al . 1980) and four during July and August at stations 3 to 15 ni. Those caught
in April were large, 14 to 24 mm TL, while those obtained in July and August
ranged from 11 to I3 mm TL. Jude et al. (I98O) hypothesized that two species
of Coreqonus larvae were present, those collected in April possibly being
Coreqonus clupeaformis or C. artedi i , while those collected in June, July and
August were believed to be Coreqonus hoy i . This is a reasonable conclusion
since C. clupeaformis and C. artedi i spawn in late fall; whereas, C. hoy i
spawn in early spring. Eggs of C. hoy i therefore hatch later and larvae grow
more slowly than those of C. clupeaformi s or C. artedi i which were spawned and
hatched earlier. During I98O, there were again two groups of Coreqonus

214

larvae. In April, 45 larval Coregoninae, averaging 13.2 mm TL, were collected
from all three beach stations at temperatures of k.h to 13*8 C. Four others,
taken in June and July, were only 12.2 to 13.5 "im TL and were taken at water
temperatures between 12.2 and 25.1 C. Larvae taken in April were believed to
be either C. clupeaformis or C. artedi i . while th2 four captured later in the
year were most likely C. hoy i .

Young-of- the- Year —

As previously mentioned small individuals (60 to 100 mm) collected from
September to December were most likely YOY C. hoyi (Fig. 6l) . Lengths of YOY
collected during these months have remained fairly consistent throughout the
4-yr period (Table 43), even though water temperature and abundance varied.
YOY Coregoninae were most susceptible to seines and trawls and were captured
at all stations, beach to 15 m. YOY were most often caught when water
temperatures were between 5 and 17 C^.

Table 43. Average total length (mm) and standard error of YOY Coregoninae
collected in the vicinity of the J. H. Campbell Plant, eastern Lake
Michigan 1977 to I98O. Sample size is given in parentheses.

Month

Year

September

October

November

December

1977
1978

1979
1980

7311.74 (27)
7114.23 (9)
7510.42(334)
6710.29(334)

7010.59 (234)
7710.22(1666)
7510.40 (391)
7210.19(1387)

7210.99 (61)
8310.38 (475)
7710.28(1430)
7610.25 (687)

7214.79 (4)
8612.31 (18)
8214.01 (9)
7610.21(894)

Yearl ings —

Yearling unidentified Coregoninae have been observed during every year of
the study and ranged in length from 85 to I50 mm (Fig. 6I) . These individuals
were often caught from June to September usually in bottom gill net sets and
trawl hauls predominantly in 6 to 15 m of water. Water temperatures at time
of capture were usually between 3 and 21 C.

Adults—

Age-2'^ fish (age assigned using length-frequency histograms) ranged in
length from I60 to 210 mm. These fish were captured in both surface and
bottom gill net sets as well as trawl hauls at all stations. Fish older than
2 yr, most probably mature adults, ranged from 210 to 320 mm TL (Fig. 6I) .
These fish were almost exclusively caught in bottom gill nets set at stations

215

6 m or deeper, usually during either June or September, and most often at
water temperatures between 6 and 19 C. Adult Coregoninae were noticeably
absent from catches during 1978 and 1979 (Fig. 6l) , which could be due to poor
survival of the 1975 and 1976 year classes. The commercial fishery for this
species was closed in 1976. Over the h-yr period year classes were easily
followed by using length-frequency data. Close examination revealed that fish
collected in May 1978 and 1979 and April I98O did not fit a consistent growth
pattern, since YOY individuals caught in December were smaller than yearlings
observed the following May or June. Unidentified Coregoninae collected in
April 1980 were also much smaller than those observed the previous December.
These individuals are not abundant, as only I5 have been collected over the ^-
yr period; however, these smaller individuals may actually be YOY
C. clupeaformi s or C. artedi i . These species, which spawn in late fall and
whose eggs hatch in early spring, have been collected as larvae in April
plankton net tows and also as YOY in April or May trawl hauls. These few fish
may be stragglers from a population which utilizes cool water farther
offshore.

Plant Effects—

Larvae — Few larval Coregoninae have been collected in the vicinity of the
J. H. Campbell Plant over the past 4 yr; 11 were taken in 1977-1979 and kS in
1980. Therefore plant operational effects upon larval populations of this
family cannot be determined accurately. However, of the kS larvae collected
in 1980, most were collected in April with almost twice as many observed at
the south reference beach station compared with the plant transect beach
stationso

Juveniles and adults — Seines and surface gill nets were less effective at
capturing unidentified Coregoninae than bottom gill nets or trawl hauls (Table
61), therefore only the latter two were compared for a determination of plant
effects. Day and night trawl catches at 6- (C, L) and S'-m stations (D, N)
showed a large increase in abundance of unidentified Coregoninae between I978
and 1980 (Fig. 64). Bottom gill net data for 198O (Fig. 65) do not show
greater catches for stations in the vicinity of the plant, in fact, catches at
station U (6 m, north discharge) were below those observed at reference
station C (6 m, south) . Catches during the day were, however, greater at the
north transect in the vicinity of the plant than at the reference transect.
ANOVA results for 1977*1980 showed that trawl catch of unidentified
Coregoninae was significantly greater at the plant transect than at the
reference area (Tables kk and kS) * This difference was most pronounced in
1979 when construction activity in the discharge area was at its peak
(Fig. 66). Increased turbidity in the discharge area due to the construction
may have decreased net avoidance, thus causing greater catches.
Alternatively, Coregoninae may have been attracted to the discharge by
organisms made more available to fish in the water column by the construction
activity. Note that trawl catches mainly include YOY and yearlings.

Summary — Although the unidentified Coregoninae catch has increased
significantly from 1977 to I98O, construction and operation of the J. H.
Campbell Plant has affected the distribution and abundance of the species in

216

Q
Ui

O
UJ

1000

o
o

X
(£

u.

u.
o

(T
UJ
CD

500

1978

□ » DAY
H > NIGHT

6M

1979

1980

6M

9M

9M

C L ON

6M

9M

C L ON

STATION

C L ON

Fig. 64, Total number of unidentified Coregoninae caught in trawl
hauls (pooled over months) at reference stations C (6 m, south) and
D (9 m, south) and plant-affected stations L (6 m, north) and N (9 m,
north) during the day and night in the vicinity of the J. H. Campbell
Plant, eastern Lake Michigan, 1978-1980,

the immediate vicinity of the plant. However, this effect does not seem to
have produced an adverse impact on local unidentified Coregoninae populations.
Strong year classes, evidenced by the abundance of YOY during September to
December, have been produced each year and subsequent survival of these year
classes has also been documented. During I98O mature adult Coregoninae
appeared in the area, which is the first time this occurred since 1977.
Unidentified Coregoninae were caught most often at depths of 6 to 9 m,
particularly at night. Catches of larval Coregoninae have also increased from
a low in 1977-1978 of 3 to a high of 45 in I98O.

Yel low Perch

Introduction —

Yellow perch is a widespread and highly adaptable percid fish, occurring
throughout most of North America. In Lake Michigan, yellow perch are most
abundant in protected bays, notably Green Bay, and are moderately abundant
along the shoreline at depths less than 40 m (Wells and McLain 1973).

217

80

-

1 60

<

-

D
6M

1 40
li.

O 20

-

•

o

-

— ^

_^

M.'

NIGHT
6M 9M

DAY

C L U

9M

D N
STATION

C L U

D N

Fig. 65. Total number of unidentified Coregoninae caught in bottom
gill net sets (pooled over months) at reference stations C (6 m, south)
and D (9 m, south) and plant-affected stations L (6 m, south discharge),
U (6 m, north discharge) and N (9 m, north) during the day and night in
the vicinity of the J. H. Campbell Plant, eastern Lake Michigan, I98O.

Yellow perch have been important in Lake Michigan as a commercial species
since the l880s and as a sport fish since at least the 1920s (Wells 1977)-
Yellow perch abundance in Lake Michigan declined abruptly in the early and
mid-1960s due to displacement and interference by alewife and due to an
intensive fishery (Wells 1977). Perch populations increased in some areas of
the lake during the 1970s (Wells 1977). Seasonal depth distribution of yellow
perch in east-central and southeastern Lake Michigan has been described by
Wells (1968), Brazo et al . (1975) and Jude et a). (1975. 1978. 1979a, 1979b,
1980) .

During our 4-yr study in Lake Michigan near the J. H. Campbell Plant,
yellow perch was the fourth-most abundant species captured in adult sampling
gear during 1977, while during 1978, 1979 and 1980, perch were sixth in
abundance. Total yearly catch of yellow perch ranged from 605 to 1715 fish

218

Table 44. Analysis of variance summary for unidentified Coregoninae
caught in trawls at stations C (6 m, south) and L (6 m, north) near the
J. H. Campbell Plant, eastern Lake Michigan, 1977 through 1980. Data
for June through November were analyzed.

Attained

Source

of

significance

variation

df

Mean square

F-statistic

level

Year

3

4.9421

57.0422

<0.0001*«

Month

5

3.722B

42.9690

<0.0001«*

Station

1

1.0683

12.3302

0.0007*«

Time

1

3.9996

46.1637

<0.0001*«

Y X M

15

2.1017

24.2585

<0.0001**

Y X S

3

0.6458

7.4537

0.0002««

M X S

5

0.4004

4.6217

0.0008**

Y X T

3

0.8769

10.1208

<0.0001**

M X I

5

0.6507

7.5099

<0.0001**

S X T

1

0.6708

7.7428

0.0065*

Y X M X

S

15

0.4132

4.7687

<0.0001**

Y X M X

T

15

0.3590

4.1441

<0.0001**

Y X S X

I

3

0.2479

2.8616

0.0408

M X S X

T

5

0.2021

2.3329

0.0480

Y X M X

s X r

15

0.2583

2.9810

0.0006**

Uithin cell

error

• «»«B<a»^«>«B«a^«a

96

0.0866

*« Highly significant (P < O.OOl) .
« Significant (P < 0.01) .

representing 0.8 and 2.
col lections. Ye 1 low
field samples from May

0* respectively of the total yearly Lake Michigan
perch larvae were generally present in Lake Michigan
through August.

Larvae —

Yellow perch eggs generally incubate in approximately 10 days and larvae
are about 5 nwn at hatching (Scott and Grossman 1973). Young perch usually
grow beyond the yolk-sac stage in about 5 clays and are demersal at about 30 mm
(Wong 1972). Larval perch swim well relative to other fish, and exhibit
notable ability to avoid larval sampling devices at lengths exceeding 9 mm
(Houde 1969; Jude et al . I98O) .

Seasonal di str i but ion —

May — Sampling was not performed during May 1977, but during mid-May
1978-1980, yellow perch larvae were collected at densities considerably
greater than at any other time of a given year (Figs. 69-78). Mean lengths of
fish sampled in May (5-7-7.2 mm) indicated that these perch were spawned in
early May. Perch spawning in early May does not generally occur in cold Lake
Michigan water but does occur in warmer waters of inland lakes, rivers and
streams, some of which run into Lake Michigan. Perch larvae sampled in mid-

219

Table 45. Analysis of variance summary for unidentified Coregoninae caught
in trawls at stations C (6 m, south) , D (9 m, south) , L (6 m, north) and
N (9 m, north) near the J. H. Campbell Plant, eastern Lake Michigan, 1978
through 1980. Data for June through November were analyzed.

Attained

Source

of

significance

variation

d£

Mean square

F-statisUc

level

Year

2

1.8997

13.3865

<0.0001«*

Month

5

5.5961

39.4348

<0.0001*«

Area

1

2.1497

15.1486

0.0002**

Depth

1

6.2450

44.0070

<0.0001**

Time

1

11.8938

83.8132

<0.0001*«

Y X M

10

3.0556

21.5323

<0.0001««

Y X A

2

0.7992

5.6317

0.0044*

M X A

5

0.7066

4.9804

0.0003**

Y X D

2

0.4491

3.1644

0.0452

M X D

5

0.7016

4.9438

0.0003**

A X D

1

0.1643

1.1577

0.2837

Y X T

2

1.4033

9.8885

0.0001**

M X I

5

1.0213

7.1970

<0.0001*«

A X T

1

0.9196

6.4814

0.0120

D X T

1

0.4672

3.2921

0.0717

Y X M

X

A

10

0.8671

6.1104

<0.0001**

Y X M

X

D

la

0.5683

4.0049

0.0001**

Y X A

X

D

2

0.5271

3.7142

0.0267

H X A

X

D

5

0.2794

1.9692

0.0867

Y X M

X

T

10

0.6306

4.4435

<0.0001**

Y X A

X

T

2

0.0S46

0.3846

0.6814

M X A

X

T

5

0.2361

1.6636

0.1471

Y X D

X

I

2

0.3016

2.1256

0.1231

M X D

X

T

5

0.5681

4.0030

0.0020*

A X D

X

T

1

0.0736

0.5185

0.4726

Y X M

X

A X

D

10

0.1382

0.9740

0.4687

Y X M

X

A X

T

10

0.5690

4.0098

0.0001**

Y X M

X

D X

T

10

0.1275

0.8982

0.5367

Y X A

X

D X

T

2

0.3232

2.2778

0.1062

M X A

X

D X

I

5

0.3029

2.1342

0.0647

Y X M

X

A X

D X T

10

0.2309

1.6273

0.1043

Within cell

error

IHH

0.1419

♦« Highly significant (P < O.OOl).
» Significant (P < 0.01) .

May in our study area probably originated from these inland waters (e.g., the
Grand River, Pigeon Lake and Lake Macatawa) and were carried into Lake
Michigan to our sampling area by currents (Jude et al. I98O) .

Larvae were always most concentrated in water less than or equal to 3 ni
during May sampling, and highest mean densities (220-300/1000 m^) for any
given year were found at the south reference transect. The higher mean
densities of yellow perch at the south transect might be expected since Pigeon

220

21 UNIDENTIFIED COREGONINAE

/ N. STATIONS C AND D

_ ^ / ^^ (REFERENCE)

2 t ,>. / ^N STATIONS L AND N

5 g "* / N (PLANT)

I- /

/

UJ 0^

o «-

1978 1979 1980

YEAR

Fig. 66. Geometric mean number plus one of unidentified Coregoninae
caught in trawls at stations C (6 m, south), D (9 m, south), L (6 m, north)
and N (9 m, north) near the J. H. Campbell Plant, eastern Lake Michigan,
1978 through I98O. Graph illustrates the YEAR x AREA interaction.

Lake, which is the closest potential inland spawning ground, is a well
documented area for perch reproduction (Jude et al. 1978, 1979a, I98O, 198la)
and fish carried out from Pigeon Lake to Lake Michigan would likely be carried
along the shoreline. Liston and Tack (1976) reported that current direction
in Lake Michigan in the vicinity of the J. H. Campbell Plant was usually
parallel to the shoreline (either north or south) and directions were
sustained at times over several days. Currents from the north would sweep
larvae from Pigeon Lake into our south reference transect where they would be
vulnerable to our larvae sampling gear. Relatively warm water (12-1^ C)
occurred in the beach zone in May 1979» and comparatively high mean densities
of perch larvae were collected (I5O/IOOO m^ from the north transect and
300/1000 m^ from the south transect). Perch reproduction in Pigeon Lake was
exceptional in 1979 (Jude et al. I98O) and probably contributed heavily to
these high densities.

Early June — Abundance of yellow perch larvae in early June samples varied
from year to year in our study. No perch larvae were collected during this
period in 1977 (Figs. 67-68). Relatively low water temperatures (7-17 C) in

221

BEACH — 3 M

o
o
o

>^

<

a:

40

30-

20-

10

17-22 JUN

40

30

20

10

17-22 JUHC 1»77
LAKE MICHtGAN
BCACH-3M
S TRANSECT
OAY-I^ NIGHT
X- 5.S (0.0)
N« I

1977 „

T

t

-- 30

• 25

.. 20

" 15

• 10

• . 5

s

a:

UJ

2

13-14 JUL

818

O-H JULY 1i77
UU(C hNCHICAN
M*CM>3M
N. TRANSeCT
MV-fMCMT
X- 4.7 (0.2)
M- 2

20-28 JUL

20-28 JULY »7;
LAKE MICHICAM
BEACH- 3M
N. TRANSECT
OAY-fNK:HT
X' 6 2 (0.0)
N- 1

5 10 15 20 25 5 10 15 20 25

5 10 15 20 25
TOTAL LENGTH (MM)

Fig. 67. Density (no-/1000 M^ plotted on log scale) of larval yellow perch
collected during June to September 19 77 at beach -3m (all contours, depth
strata and diel periods pooled) near the Campbell Plant, eastern Lake Michigan,
Horizontal line across each bar denotes mean density while height of bar re-
presents ± 2 S.E. Midpoint of water temperature range (vertical line) at time
of collection is shown. Length-frequency histograms for all larvae collected
during each period are also shown. N = number of larvae collected, x = mean
length of larvae, S.E. given in parentheses.

222

100 -•

ro

O
O

o

u) 10

<
>

a:

<

o

z

I

40
30
20
10

JS 40

a. 30

DENSITY TWAWSgCT TgMP.

D

NORTH
SOUTH

7\

T'
4

11 U

/
/
/
/
/
/
/

T
1

/
/
/

/

17-22 JUN

. \A

7-9 JUL

1977 .

12

ANO 19 M

OCNSITY TWAWSCCT

D

NORTH
SOUTH

/

/
/
/
/

/
/

.- 25

20 G

UJ
(S

15 <

UJ
Q.

2

UJ
•• 10

-. 5

I7>22 JUN

7-9 JUL

17-22 JUNC If77
LAKE MtCMQAM

STAriON e-w

N rRANSCCT

OAr-fNMmr

i- 8.0 {O.t)
N- 2

M77

17-22

LAKC MCHMSAH
STAriOM I2-15W
S TRANSCCT
OAV-*: NIGHT
X- c.a (0.2)
N- 1%

II 7-»

II OKI

7 $. Tl

JULY 1077

LAKC MCHM2AN
STAnON t3-tSM
$. TRANSECT
OAYfNICMr
SO (0.0)

20-

10-

-22 JUNC «77
LAKC MCHKAN
STATION C-Mt

: TUANSCCT
0AY4-NICNT

J

»| 7-9 JULY »77

ll LAKC yKHKUkN
L STATION ft-MI
7 S TRANSCCT
^ OAYi-MCNT
i« S.S (0.0)

10 15 20 25 5 10 15 20
TOTAL LENGTH (MM)

5 10 15 20 25 5 10 15 20 25
TOTAL LENGTH (MM)

Fig. 68. Density (no./lOOO M plotted on log scale) of larval yellow perch
collected during June to September 1977 at 6 and 9 m, 12 and 15 m (all contours,
depth strata and diel periods pooled) near the Campbell Plant, eastern Lake
Michigan. Horizontal line across each bar denotes mean density while height of
bar represents ± 2 S.E. Midpoint of water temperature range (vertical line) at
time of collection is shown. Length-frequency histograms for all larvae
collected during each period are also shown. N » number of larvae collected,
X = mean length of larvae, S.E. given in parentheses.

223

BEACH — 3 M

600 t

ro

o
o
o

'»^
u

%

IT

<

z

40

30

20

10

K
Z
UJ

g 40

Q,

30

20

10

1 20

IS H

UJ

tr

<

UJ
UJ

10

15-18 MAY

15-18 MAY 1978

LAKE MICHIGAN
BEACH-3M
N. TRANSECT
DAY+NIGHT
X- 6.3 (0.1)
N- 45

5-tO JUN

SI 5-10 JUNE 191
SI LAKE MK^HKUN
**tBEACH-3M

/n. transect
^ day+nksht

X- 7.8 (2.6)
N- 3

ini

A

rl

15-18 MAY 1978

LAKE mk:hk;an

8EACH-3M
S. TRANSECT
DAY-t-NIGKT
X- 6.3 (0.1)
N- 58

^1

I

19.23 JUN

19-23 JUNE 1978
LAKE MICHIGAN
BEACH- 3M
N. TRANSECT
DAY+NIGHT

X- 6.0 (0.0)
N- 4

!

ii ■ , ■

5 10 15 20 25

5-10 JUNE 1978
LAKE MCHKAN
BEACH-3M
S. TRANSECT
DAY+NIGHT

X- 5.5 (0.0)
N- 1

19-23 JUNE 1978
LAKE MCHMAN
BEACH-3M
S. TRANSECT
DAY -ANIGHT

X- 6.2 (0.2)
6

N>

5 10 15 20 25 5

TOTAL LENGTH (MM)

10 15 20

Fig. 69. Density (no./lOOO M plotted on log scale) of larval yellow perch
collected during April to September 1978 at beach -3m (all contours, depth
strata and diel periods pooled) near the (Campbell Plant, eastern Lake Michigan,
Horizontal line across each bar denotes mean density while height of bar re-
presents ± 2 S.E, Midpoint of water temperature range (vertical line) at time
of collection is shown. Length-frequency histograms for all larvae collected
during each period are also shown. N = number of larvae collected, x = mean
length of larvae, S.E. given in parentheses.

22^

50

ro

o
o

" 10 --

q:

<

40 1
30-
20
10 ^

o 40

Ui

°-30

20
10

•25

a

+ 20^j
■I- I5<

UJ

• 5

15-18 MAY

tS-» MAT 1078
LAKE MOMAM
STATION f-9M
N. TRAMSecr
OAV-fNttHT
X- 5.« (Of)

5-10 JUN

S>n JUNC 1«7t

LAKC MCHMMN
STATIOM ff~9M
M. TKAMSeCT
OAY>NN;Mr
X- 8.7 (0 2)
H» f

1-3 JUL

tt-23 MM »?•

STAriON •-._
N. TftAHSCCT
MV-»MGHr

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TOTAL LENGTH (MM)

t-J JULT W7S

lAKC mcHKAm

STATION §-m
S TRANSCCr
0AY4-NM»«r
i- 9.4 (0 t)
N- 23

10 15 20 25

5 10 15 20 25

Fig. 70. Density (no./lOOO M^ plotted on log scale) of larval yellow perch
collected during April to September 1978 at 6 and 9 m (all contours, depth
strata and diel periods pooled) near the Campbell Plant, eastern Lake Michigan.
Horizontal line across each bar denotes mean density while height of bar repre-
sents ± 2 S.E. Midpoint of water temperature range (vertical line) at time of
collection is shown. Length • frequency histograms for all larvae collected
during each period are also shown. N = number of larvae collected, x « mean
length of larvae, S.E. given in parentheses.

225

O
O

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AND 19 M

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OENSITY TRANSECT TEMP.

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30
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15- tS MAY 1978
LAKE MICMIGAN
STATION !2-15M
S TRANSECT
DAY > NIGHT

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CAKE MICHIGAN
STATION t2-t5M
N TRANSECT
OAY^ NIGHT

W-23 JUNE 1978
lAHC IMCHICAN
STAriON 12- ISM
S TfUHSeCT
DAY ♦MCHT

»-3 JULY »978
LAKE MICHlCAN
STATION 12 -ISM
N TRANSECT
DAV-fNiGHl
i- S 2 (0

K3 JU.Y 1878

LAKE mchm;an

STATIOM 12-15M
S TRANSCCI
OAT^MCHT

|§ 17-21 JUIY 1978

« LAKE MHJIMGAN

Lr STAllOI* 12 ISM

/ N TRANSECr

OAY^NIClIf

X- 8 3 (0 3)

17-21 JIM « M/S
CAKE MWIWaW
STATIOM 12 ISM
S TRAMSEC1
OAVtNICHf
i- S« (0 3)

5 10 15 20 25 5 10 15 20 25 b 10 15 20 25 5 10 15 20 25
^"'^' TOTAL LENGTH (MM)

Fig. 71. Density (no./lOOO M plotted on log scale) of larval yellow perch
collected during April to September 1978 at 12 and 15 m (all contours, depth
strata and diel periods pooled) near the Campbell Plant, eastern Lake Michigan.
Horizontal line across each bar denotes mean density while height of bar re-
presents ± 2 S.E. Midpoint of water temperature range (vertical line) at time
of collection is shown. Length-frequency histograms for all larvae collected
during each period are also shown. N = number of larvae collected, x = mean
length of larvae, S.E. given in parentheses.

226

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S. TRANSECT

0AY4^4ICMr

X- 7.0 (0.0)

Hm 1

5 10 15 20 25

5 10 15 20 25 5 10 15 20 25 5 10 15 20 25
TOTAL LENGTH (MM)

Fig. 73. Density (no./lOOO M"^ plotted on log scale) of larval yellow perch
collected during April to September 19 79 at 6 and 9 m (all contours, depth
strata and diel periods pooled) near the Campbell Plant, eastern Lake Michigan,
Horizontal line across each bar denotes mean density while height of bar re-
presents ± 2 S.E. Midpoint of water temperature range (vertical line) at time
of collection is shown. Length-frequency histograms for all larvae collected
during each period are also shown. N = number of larvae collected, x = mean
length of larvae, S.E. given in parentheses.

228

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LAKE MICHIGAN
BCACH-3M
H TRANSeCT
DAY ♦NIGHT
X- 7 2 (0 2)
N- 25

i

19-20 MAY 19M
LAKE MICHICAN
BCACH-JU
S TRANSECT
DAY > NIGHT
X- 7 (0 3)

Ui

2-4 JUN

8j 2-4 JUNE 1980

ol LAKE mchk;an

ljBEACH-3M

7h transect

DAY ♦MGHT

' 9S (0 0)
N« 1

16-18 JUNE 1980
LAKE MICHIGAN
BEACH- 3M
N TRANSECT
DAY ♦NIGHT
X- 3 5 (0 0)

5 10 15 20

1 I I '

18-18 JUNE 1880
LAKE MiCHiGAN
BEACH-3M
S TRANSECT
DAY ♦NIGHT
X- 6 5 (0 0)

1-2 JULY 1980
LAKE MICHK^AN
BEACH- 3M

n transect
oay>nk;ht

X- 8 2 (0 2)

14-16 JUL

oj 14-16 JULY 1980

§1 LAKE MICHtGAN

"L8EACH-3M

7n TRANSECT

DAY ♦NIGHT

X- 8 (0 0)

I

1-2 JULY 1980

LAKE mk:higan

BEACH- 3M

s transect
day>nk;mt

X- 5.8 (0 3)
N- 7

5 10 15 ^L) ZS

5 10 15 20 25

5 10 15 20 25 5 10 15 20 25
TOTAL LENGTH (MM)

Fig 75 Density (no,/1000 M^ plotted on log scale) of larval yellow perch
collected during April to September 1980 at beach -3m (all contours, depth
strata and diel periods pooled) near the Campbell Plant, eastern Lake Michigan.
Horizontal line across each bar denotes mean density while height of bar re-
presents ± 2 S.E. Midpoint of water temperature range (vertical line) at time
of collection is shown. Length- frequency histograms for all larvae collected
during each period are also shown. N - number of larvae collected, x = mean
length of larvae, S.E. given in parentheses.

230

- 25

20 3

UJ

-• 15

-• 10

- 5

40 1
30
20-
10-

19-20 MAY

t9-20 UAY 1960
UKC MICHiGAN
! STATION S-9M v
TRANSECT
0AY4NIGHT
X- 7.1 (0 6)
M- 3

-18 JUN

1-2 JUL

14-16 JUL

W-18 JUNC 1980
LAKE MICHIGAN
STATION •-9M
N TRANSECT
DAY -f NIGHT
X» 5.5 (0.0)
M- 3

U

K
UJ

a

5 10 15 20 25 5 10 15 20

30-

20

10-

1-2 JULY 1960
LAKE IMCHKAN
STATION «-9M
N. TRANSECT
OAY-fNIGHT
X- 9.0 (0 2)
N- 57

J .

;?| 1-2 JULY I6M

«| LAKE MCM6AN

^L STATION %-m

7 S TRANSECT

\

16 JULY 16«
UKE MCHIGAN
STATION S-6y

TRANSECT
DAY •►NIGHT

7 ♦ (0.4)

OAY-t-MGHT
6 (0 1)

H-W JULY ««
LAKE MICHKAM
STATION 6-IM

S. TRANSECT
OAY-l^NIGMT
X- 6.1 (0 6)

5 10 15 20 25
TOTAL LENGTH (MM)

5 10 15 20 25

Fig. 76. Density (no./lOOO M plotted on log scale) of larval yellow perch
collected during April to September 1980 at 6 and 9 m (all contours, depth
strata and diel periods pooled) near the Campbell Plant, eastern Lake Michgian.
Horizontal line across each bar denotes mean density while height of bar repre-
sents ± 2 S.E. Midpoint of water temperature range (vertical line) at time of
collection is shown. Length-frequency histograms for all larvae collected
during each period are also shown. N = number of larvae collected, 5c « mean
length of larvae, S.E. given in parentheses.

231

80 4

fO

o

o
o

>^
UJ

%

<

12 ANO 19 M

DENSITY TRANSECT TEMP.

Q NORTH

2 SOUTH

1980

10

.. 25

-• 20

-• 15

- 10

- 5

D

cr

Q.

UJ

40
50
20
10

19-20 MAY

19-20 MAY mo
LAKE MICHtGAN
STATION I2-15M
N TRANSECT
DAY+NICHT

16-18 JUN

o

UJ
0.

t«-ia JUNE 1960
LAKE WNCHtCAN
STATK>N 12-13M
N TRANSECT

DAY ^nn:ht

X- 7 J (0 7)

1-2 JUL

1-2 JULY 1980
LAKE MCKHCAN
STATION 12- ISM
H TRANSECT
OAY-t-MGHT

14-16 JUL

y.

14-16 JULY 19S0

LAKE mk:hk;an

STATION 12-15M
N TRANSECT
OAr ♦NIGHT
X=.10 4 (16)

5 10 15 20 25 5 10 15 20

30

20

'°U1

1-2 JULY 1M0

LAKE MiCHiCAN
STATKW 12-15M
S TRANSECT
OAY+NKtHT
X- 5 9 (0 1)
N- 41

o| 14- )• JULY 19«0
ol LAKE MICHKMN
•"LSTATION 12-15M
71 TRANSECT

5 10 15 20 25 5 10 15 20 25
TOTAL LENGTH (MM)

Fig. 77 . Density (no./lOOO >r plotted on log scale) of larval yellow perch
collected during April to September 1980 at 12 and 15 m (all contours, depth
strata and diel periods pooled) near the Campbell Plant, eastern Lake Michigan.
Horizontal line across each bar denotes mean density while height of bar re-
presents ± 2 S.E. Midpoint of water temperature range (vertical line) at time
of collection is shown. Length-frequency histograms for all larvae collected
during each period are also shown. N = number of larvae collected, x = mean
length of larvae, S.E. given in parentheses.

232

Inshore water in 1977 probably delayed perch spawning until mid-June in Lake
Michigan, and fish spawned in inland waters were apparently large enough by
early June to avoid our sampling gear.

In contrast, unusually warm beach zone temperatures (17"21 C) in I978
resulted in late May - early June spawning by yellow perch in Lake Michigan
(Figs. 69-71) • Perch larvae collected were represented by a combination of
fish spawned in Lake Michigan (length less than 7-0 mm) and a few fish spawned
in inland waters which ranged in length from 7*5 to I3.O mm. Collection of a
13.0-mm larva was unusual, since perch larger than about 7.5 mm were generally
able to avoid our nets.

Low mean densities (1 - i*. 5/1000 m^) of perch larvae recently hatched in
Lake Michigan were estimated from early June collections in I979
(Figs. 67-77) • As in 1977* perch spawned in early May were apparently large
enough to avoid our nets.

A 9.5-mm yellow perch larva that was probably spawned in inland waters
was collected on 2-4 June I98O (Fig. 75). Our early June sampling period
apparently preceded perch spawning in Lake Michigan in I98O since no newly
hatched larvae were collected.

After the first sampling period of June I98O, perch that were spawned in

early May and collected then in high densities were not collected in fish

larvae sampling gear. Perch from this cohort were not caught again until

August when they became vulnerable to adult and juvenile sampling gear.

Late June — Perch spawning in Lake Michigan generally occurs in late May -
early June, and yellow perch larvae that were spawned in Lake Michigan were
collected at relatively high densities during late June of each sampling year
(Fig. 67-77). Mean length of perch ranged from 4.0 to 7.3 mm. Although
larvae were distributed at all sampling depths, highest fish larvae densities
occurred at contours less than or equal to 3 m during all years, except 1977.
in 1977 perch larvae densities were highest at 6 and 9 m. Larvae were
collected at both transects in all years, but in I979 and I98O, fish larvae
densities were greater at the north transect than at the south reference
transect, perhaps because areas of riprap were available to spawning perch at
the north transect during those years.

July — Length-frequency data for early and late sampling periods in July
indicated that scattered perch spawning continued into late June (Fig. 67-77).
Samples collected in July therefore included some newly hatched larvae along
with larvae that were hatched in early June. Some fish from early June
spawning were large enough in July to exhibit net avoidance behavior.

Yellow perch larvae densities were roughly comparable for July 1977-1979
despite the upwelling which occurred in July 1979. The effect of the
upwelling upon perch YOY was not evident until August and September. During
July of all 4 yr, larval perch densities were generally lowest in water 3 m
deep or less.

233

I50--

O

o

o

Ixl
<
>

cr

< 50

1978

,.*'";.-" ,,^'

NORTH TRANSECT

SAMPLING PERIOD

«sri5

^>^ i^^

.A^"^ ^^^ ^.i>

svi^

SAMPLING PERIOD

Fig. 78. Mean density (no./lOOO m ) of larval yellow perch for north
and south transect stations in Lake Michigan near the J. H. Campbell
Plant, 1978 to 1980. Mean densities were calculated by averaging
densities over all gear (plankton nets and sleds) , strata and diel
periods (day and night) sampled.

Ilk

1979

307 195

SAMPLING PERIQD

W

NORTH TRANSECT

r.^^'

^15

^^^ ' ^0^^ ^;5^''^ "^ w^ ^^ ^

SAMPLING PERIOD

SOUTH TRANSECT

^-^^ -^ ,^^^^ V^ x1'^^ -^^ ^O''^''

Fig. 78. Continued,

235

o
o
o

<

> SO-

<

1980

NORTH TRANSECT

SAMPLING PERIOD

SAMPLING PERIOD

SOUTH TRANSECT

Fig. 78. Continued,

236

Water temperatures rose gradually but steadily from April through July
1980 (Fig, 22), and perch spawning may have been concentrated over a
comparatively short time period in mid-June when temperatures were favorable.
This would explain the relatively high mean densities (e.g., about 50/1000 m^
at depths from 6 to 15 m) of yellow perch larvae estimated from samples
collected in early July I98O.

August — During 4 yr of sampling, yellow perch larvae were collected in
August only in 1979 (Figs. 67-77). In other years (1977. 1978 and I98O) a few
YOY were caught in adult sampling gear (Fig. 79). but perch were able to avoid
fish larvae sampling gear. Larvae collected in August 1979 were small
relative to other years (6.0-10.5 mm) possibly due to the July upwelling which
could have retarded perch growth. Net avoidance could also explain this
f i nd i ng .

Young-of- the- Year —

YOY comprised from 30 to k]% of the total number of yellow perch caught
in trawls, seines and gill nets during the 4-yr study. Catch was lowest in
1979 (183 fish) when an upwelling and persistently low temperatures (Fig. 22)
apparently limited perch reproductive success and perch catches in general.
In contrast, 696 YOY perch were captured in I98O when water temperatures were
mild and no upwel lings were observed.

Seasonal di str ibut ion —

July and August — Except for five perch (30- and 40-mm length interval)
caught in July 1977. YOY were not vulnerable to adult sampling gear until
August. In general YOY exhibited length modes at 30 and 60 mm. The upper end
of this size range represents fish that were spawned during mid-May in major
streams and lakes which flow into Lake Michigan (see RESULTS AND DISCUSSION,
Yel low Perch , Larvae). These fish were probably carried to the sampling area
from their nursery grounds by shoreline currents (Jude et al. I98O) . Smaller
fish captured in August were spawned in the inshore regions 'of Lake Michigan
during late May or early June. Although YOY were caught at all sampling
depths, most were caught from the beach zone to 9 ni (Fig. 79)* Catches of YOY
in 1977 (62 fish) and in I98O (224 fish) were notable. Perch fry also
appeared in August larvae samples in 1978 and 1980 at densities from
16-53/1000 m^. No YOY perch were caught during August 1979 probably due to
cold water temperatures which limited YOY growth and numbers. Clady (1976)
reported that survival of larval yellow perch is adversely affected when fish
are exposed to a temperature of 10 C. Temperatures between 2.5 and 10 C were
prevalent from July through early August in 1979-

September — By September a few YOY had grown into the 90-mm length
interval. Fish distribution was still skewed towards shallower sampling
depths (beach to 9 m) even though IO9 perch (representing 28% of the YOY
catch) were captured at 12 and 15 m in I98O. September catches of YOY were
high in 1977 (283 fish), 1978 (268 fish) and I98O (385 fish). Only one YOY

237

<
o

s
o
o

a:

UJ
CD

IX IG' ■

1x10*=^

1x10'-

1x10' —
1x10' —
1x10' —

1x10* =r

1x10' —
1x10' —
1x10' —
1x10*

1x10'

1x10'
1x10'

hYL

► p^O - -

lo-3n l6-9n

NORTH TRANSECT
1977

h-YOY-

<10' —
1x10' -

1x10*-

1,10' 4- HOY-

1x10'-
1x10'

1x10* =r
1x10'-
1x10'

1x10'

1x10* =r

•YL

J L

— r \

-AD

-J — u — I — u — U — J — I. ,1 .

YL

AD

I I

I I

-I j_

|.YOY-

YL

AO

V-LJx

1,1 t 1.1

li I,

• YOY

•YL

•YOY-

AO

YOY.

.AD — I

JUN

JUL

AUG

SEP

OCT

NOV

DEC

20 40 60

30 120 140 160 180 200 220 240 260 280 300 320
TOTAL LENGTH (MM)

Fig. 79 . Length-frequency histograms for yellow perch collected during
June - December 1977 and April - December 1978-1980 at north and south
transects. Stations were combined into two groups for the north transect:
beach and 3 m; 6 and 9 m and into three groups for the south transect:
beach, 1.5 and 3 m; 6 and 9 m; and 12 and 15 m. Diel periods and gear
types were pooled. YOY = Young-of-the-year; YL = Yearling; AD « Adult.

238

. YL

AD-

SOUTH TRANSECT
1977

_^H , - • , JUM

. _ KOY-I

•YL-

AO-

<
o

o

o

1x10'

,x lu
IxlQ'

MO*
■xlO'
^x-J'

:x;o'
:x:o'

1x10'
•xlQ'
N-0'
1x10*
1x10'
1x10'
1x10'
Ix'O*
1x10'
IxlC
IxlC

-t

'^

L i li I i |i li J

-YOY-

•YL

_j L

AD-

I ■ I ij Jilllll lM i l i l . ll

YOY-

•YL

AD

. I' I' i' !• I i ' |! <! IM' • i •

u ll u ll ll 11 li u ll u h Ii « ' t ■

YOY-

+-YL-^

AO

•YOY

YL 1-

AD'

-j 1_

ll I I I 1} I li t! li

YOY-

. YL

AD-

i : l l I - I — :-

PUG

SEP

.^ OC"

NOV

DEC

40 80 120 160 200 240 280 320 360

TOTAL LENGTH (MM)

400

Fig. 79 . Continued.

239

AD

NORTH TRANSECT
1978

-YOY , YL-

• AO-

RPP

'4

<
o

CD

o

e

UJ

ffl

2

1x10'
lx-10'
1x10'
1x10'
1x10'
1x10'
1x10'

1x10*

1x10'
ixlQ'

-r

1x10'
IxlO'
IxiC
1x10*
1x10'

1x10'
1x10'

v:o'

YL-+

AD-

YL

AO.

JLU

YL-

AD<

i i . Ill
III III

-I I L_)l i I L.

YOY [-

YL

AO

.^j I I ij ■ ■ i' '

YOY 1 YL— f-

AO

—I i i' '

YQY-

-YL

■YOY-

YL'

40 80 '20 160 2C0 240 280 320 360

TOTAL LENGTH (MM)

Fig. 79. Continuea,

^RY

JUN

JUL

AUG

SEP

OCT

NOV

DEC

400

240

|_YL_|-

■ AO-

YL '

A0<

SOUTH TRANSECT
1978

RPR

noY

YL— f

A0<

Ixlj'-i-
I

<

CO

S
o
o

X
CO

o
a:

s

s

1x13'
IxiO'

IxiG'

]x;q^

1x10'
"xlQ*

-r

1x10'-
1x10^-
1x10' -
1x10* =

Yl

-AO-

. Jl , .1 I

I YOY— ^ YL 1-

AO-

-YOY

YL

AD<

'I • I* i> |i. • is . ! Ii' I. S I !•-

•YOY-

YL-H-

•AO-

YOY 1 YL.

•AD

JUN

RUG

, SEP

OCT

1x10'
IxlC^

'xlC

■ I t. L

YOY-

YL-

.AD-

N'CV

^ 40 8G 120 :5Q 200 240 280 320 360 400

TOTAL LENGTH (MM)

Fig. 79 . Continued.

GEC

241

<
o

CO

o
d"
O

X

IX lU -
1x10'-
1x10' -
1x10*-
1x10'-
1x10^-
1x10" -

1x10'-
1x10'-
1x10^-
1x10' ■
1x10*^
1x10'-
1x10'-
1x10' -

1x10*-
1x10'-
1x10'-
1x10' -

1x10*-
1x10'-
1x10'-

1x10' ■

1x10* =r"
1x10' —
1x10'-
1x10' -

1x10*-
1x10'-
1x10' —
1x10' —

1x10*-
1x10'-
1x10' —
1x10' —

NORTH TRANSECT
1979

|_YL 1-

lo-3n l6-9n

• AD-

-T— ' — r
YL —

-1 — ' — I 1 r

AD

n 1 — — r

— YL

AD

-I 1 — ' — r 1 — — r

YL

AD

_^ ^ — . — ^

YL

AD

n 1 1 1 r

_j — J — I — i

' YL

AD

II I I I I I

I r^

YL

AD

-1 1 1 1 \ r

AD-

1 1 r

-T — ■ — r 1 \ r

YOY.

YL

-AD-

-I 1 — I

-! 1 1 1 1 r-

RPR

HRY

-i 1 1 — ■ — \ \ 1 1

JUN

-T r r 1 \ 1 1

JUL

f — ' — r — ' — r ! ! 1 1

AUG

n 1 1 1

SEP

1 1 1 1 \ 1

OCT

NOV

20 40 60 80 inn 120 140 160 180 200 220 240 260 280 300 320

DEC

TOTAL LENGTH (MM)

Fig. 79 . Continued.

242

l:-3: i = -

YL-

AO.

SOUTH TRANSECT
1979

!x;3'— [-

<

O
CO

o
o"

o

2

i
1x10' -^

1x10'
Ix.lO'
1x10'

1x10'

ix1G'-|-

1x10'—^

Ixlu' — h

I

1x10' =y

1x10' -|-
]^:r\' — H

YL-

YL-

YL.

AO

AO-

-;— I — : L.

AD

YL-

AO

f— YOY-

I! Ii r

r ! • 1: I II

YL-

AO

PPR

_. npY

_ JUN

JUL

_ PUG

1x10'-+
■x10' —
1x10' —
1x10' =F

\:o' —

1x10'

'XiO'

-YOY-

: . Ill

-J uL-L li r ! i{- !■ !• . I f .

•YL

AD<

ix:o'-

1x10'-
■x'O' -

j YOY— ^ YL — ^

AD-

i ■ ' '- ' ■•• 'l i I

YOY 1 YL-

AD

SEF

OCi

^^ 90 120 160 20n 240 280 320 360 4C0

TOTAL LENGTH (MM)

Fig, 79 . Continued.

243

YL

AD

NORTH TRANSECT
1980

s

o

o

Ix^C
"x IC*
ix "C
IxiC'
; X 'C'
Ix IC*
1x10'
ixlO'
]xlO'
1x10*
1x10'
IX 10*
1x10'
1x10*
1x10'

T

YL

AO

YL— H AD

_i — I—, — t 1 — jk 1_

YL

AD

-ii I > I

f-YOY

YL

AD

03

3

I I I I

YOY-

- YL

AD<

I I ii I •

J — I ii III — I I , I

-YOY HYL

AD

PPR

jUN

_ JUL

RUG

SEP

iQ*

1x10^

YOY-

-YL'

•AD

-YOY

ylH

40

16C 200 240

TOTAL LENGTH (MM)

280 520 360

Fig. 79. Continued,

Ihk

<10' -4-

ixlQ* ■
1x10'-
1x10'-
1x10' -

1x10*"
1x10' -
1x10' —
1x10'

IxIO'^
^ 1x10'-

Ui

;J 1x10'-

O

^ 1x10' -

1x10*-
1x10'-
1x10'-
1x10' -

O 1x10*

IaJ
ffi

Z

1x10' —

1x10' —
1x10'

1x10*^

lQ-3n !6-9n :i2-i5n

YL .

-AD-

SOUTH TRANSECT
1980

I r

RPR

'YL

AD

I I I

-| 1 1 1 1 1 r

.AD—

nRY

-• — 1 — ■-

-J-:

■n 1 — ' — I — ■ — I — '— *T 1 — ■ — I 1 \ 1 r

• AD

JUN

•YL

I. I; .i J Ij

■i >' ij \' i ir

JUL

J—YOY 1-

•YL

-AD-

I. I ., I» I. \\\\\ \ Ij .1 .i I.

nuc

•YOY

YL

AD

j ■■• I! I Ij- I I IJ: Ij IJ- . { l| : Ij - I ;: 11 . j-

SEP

OCT

fviOV

1 I ^ \ 1 1 1 1 1 1 \ 1 1 , 1 , L

20 40 60 80 100 120 140 150 180 200 220 240 260 280 300 320
TOTAL LE-NGTH (MM)

Fig. 79 . Continued.

2^5

DEC

was caught in September 1979 again illustrating a possible detrimental effect
upon perch reproductive success brought about by the upwelling which occurred
in July of that year.

October, November and Decembei — in general YOY perch were caught less
frequently after September and fish growth slowed down or was arrested. Perch
began moving to deeper water for winter. However, the number of YOY caught in
December rebounded in 3 of the k yr of sampling (the exception was I98O) .
Most remarkable in this regard was the 1979 catch. Only five YOY were caught
from April through November 1979* then I78 fish were caught in December.
These fish may have migrated to our sampling area from a different part of the
lake which was not affected by the upwelling we observed in July 1979« in
December, YOY perch measured between about 35 and 104 mm.

Year 1 ings —

Near the J. H. Campbell Plant, yearling perch between kS and 9^ ^^ were
caught in April. This was the same length range as YOY perch caught in
December, so it is evident that little if any growth occurred during winter.
Other investigators, working at northern and southern ends of Lake Michigan,
have reported roughly similar sizes for yellow perch at the end of one growing
season (Toth 1959; Jude et al. 1979b)-

Compared with other life stages, yearling perch were numerically of least
importance during each sampling season except 1978* Relatively low catches of
yearlings were probably due to high mortality of YOY during their first winter
of life and to yearlings spending a relatively greater proportion of their
time in deep water, out of the range of our sampling gear. Yearling perch
generally did not move into sampling depths (1-15 ^) until July and they
retreated to deeper water after September. They were therefore susceptible to
sampling gear for only about 3 nio of the year.

A weak year class of YOY (such as that observed in 1979) results in an
impoverished class of yearlings the following year (seen in 1980) . Yearlings,
following the strong 1977 YOY population, however, were prominent in 1978
samples. From these data it is reasonable to assume that yearling perch will
be important in I98I field collections since YOY produced in 1980 were
relatively numerous.

Seasonal di str i but ion —

April, May and June — Few yearlings were collected in April, May or June

during our k-yr study (Fig. 79)* it appears therefore that yearlings lag

behind adults in their movement toward shallower water after wintering at
greater depths.

July, August and September — Increased numbers of yearlings, over early
spring levels, were observed in July, August and September catches in all
years except 1979- Fish were in length intervals from kO to I60 mm, although
most were between 70 and 120 mm. Yearling perch generally occupied water less
than or equal to 9 ni from July through September.

246

Largest numerical catches of yearlings for any given year came in July,
August and September 1978 when 110, 117 and I3I fish were caught respectively.
Concentration of yearling perch in I978 shifted from the north plant transect
in July to the south reference transect in August and September. During July
96% of the yearlings collected was collected at north transect stations.
However, south transect stations accounted for 76% of the yearling catch in
August and 77% in September. These data may suggest that perch actively seek
warmer temperatures in their environment. During July, the warmest inshore
water occurred at the north transect, while in August, temperatures were
relatively equal between the two transects. In September, south transect
water was slightly warmer than at the north transect (Fig. 22).

October, November and December — Presence of yearling perch in sampling
areas diminished after September of all years. No yearlings were caught
October through December 1977. and catches were negligible for this time
period during other years (Fig. 79). It appears that yearlings precede adults
in their fall migration to deeper water. Size range of yearling yellow perch
in December was between 105 and 15^ mm. Yearling perch reaching or exceeding
150 fimi were somewhat exceptional in our samples, but were more frequently
collected by other investigators in different parts of Lake Michigan. Brazo
et al. (1975) reported that yearling perch from Lake Michigan near Ludington
had an average standard length of about I60 mm at the end of their second year
of growth; Jude et al. (1979b) documented that yearling perch caught during
October and November, in Lake Michigan near the D. C. Cook Nuclear Power
Plant, had a modal size of I5O-I6O mm.

Adults-
Adults dominated yellow perch catches during all study years. This is
reasonable since adults were present in our sampling area during a relatively
greater proportion of the year compared with YOY or yearlings and, in
addition, our adult classification is comprised of several year classes (any
fish beyond yearling). Adult perch caught ranged between II5 and 324 mm.
According to age-length data presented by Brazo et al. (1975), Lake Michigan
(Ludington) fish measuring 313 mm are 7-yr old. Thus, our samples at least
included adult yellow perch from 2- to 7-yr old. Lowest numbers of adults
were caught in I979 which we attributed to an upwelling and overall low
temperatures (Fig. 22).

Seasonal distr i but ion —

April and May — Adult perch overwinter at depths beyond our deepest
sampling station (15 m) , but during April and May a few perch began moving to
shallower water. Male perch (many with well developed gonads) are generally
the first to come inshore where they congregate and await the arrival of
females (Scott and Crossman 1973). Apparently fish are fully occupied by pre-
spawning behavior during this time and generally do not feed (J. Dorr III,
personal communication. Great Lakes Res. Div., Univ. of Mich., Ann Arbor,
Mich.). Most fish caught were in water greater than or equal to 6 m. Perch
concentrate inshore toward the end of May at which time spawning may commence
if temperatures are favorable.

2i*7

June — Perch were collected from all sampling depths in June, but were
most abundant at 12- and 15"^ stations in 1977 and I98O. In the vicinity of
the Campbell Plant, perch spawning has been most prevalent during early to
mid-June 1977"1980. Scott and Grossman (1973) give 8.9-12.2 C as predominant
perch spawning temperatures; temperatures within this range were recorded
during June each sampling year (Fig. 22). Male and female perch that were
sexually spent were first seen in June, but some fish were found with well
developed gonads indicating that spawning was not yet complete (Fig. 80) .

When possible, perch prefer to spawn over gravel, rocks or even somewhat
obscure crevices in bottom substrate (J. Dorr iii, personal communication,
Great Lakes Res. Div., Univ. of Mich., Ann Arbor, Mich.). Egg deposition in
such locations may help stabilize eggs so that they remain in a favorable
environment with fairly stable temperatures until eggs hatch (usually after
about 10 days) rather than drifting randomly because of currents and wave
action. Gravel or rocky substrates may also serve as underwater landmarks
where fish may gather in concentrations favorable for spawning. Obviously
riprap deposited over the Campbell Plant's offshore discharge and intake
structures could serve the purpose described. To date, however, adult perch
have not been documented as concentrating at the north transect (near the
riprap) when compared with the south reference transect during May, June or
July. Dredging and construction activities during 1977~1980 probably
discouraged congregating perch, but it is likely that perch will be found in
greater densities at the north transect in I98I. At the Palisades Nuclear
Power Plant, perch were caught in greater abundances at the plant (riprap)
station than at the reference (sand) station (WAPORA 1979)*

July — Compared with June, perch in July were more abundant in water less
than or equal to 9 ni. Perch with spent gonads were collected in July of all k
yr indicating that limited spawning activity continued beyond the period of
intense spawning in June (Fig. 80) . More perch were collected in beach zones
during July than in previous months as fish apparently sought warmer water
temperatures and food.

August — From 1977 to 1979» catch of adult perch was higher in August than
in any other month. In I98O the August catch was second only to that of
September. The relatively larger catches of yellow perch in August probably
relate to water temperature. Preferred temperature for yellow perch is
approximately 20 C (Scott and Grossman 1973) ; from 1977 through 1979* water
temperatures at any given sampling depth were more consistently near 20 G
during August than during any other month. In August 1977f most perch were
caught (all gear) in water less than or equal to 3 nfi where the mean
temperature was 19*8 G. In 1978, adults concentrated from 6 to 9 »" where mean
temperatures were 20.1 G (north transect) and 19*5 C (south transect). Water
in the beach zone was 15*1 G when field work was performed in 1979 and most
adults may have been in deeper water. In I98O mean temperatures of 18. 3 G
were recorded in water less than or equal to 3 ni and many adults were
collected. However, more perch were caught in water from 6- to 9"ni deep
during August I98O when water temperatures were only 14.9""15*5 G.

248

60

40

20

UJ 60

O
UJ
-I 40H

-J
o
o

20-

X

en

60

40

Ul 20-
O

GO 60

3
2!

40-

20

NO

Ns6

Ns9

NO

N*3

N«8

N>62

N«5

N«22

N«35

1977

n

N«I93

1978

N>2tO

N»70

d1

1979

N*34

-p.

1980

Nsi89

N«IO I

APR

MAY

JUN

JUL

N<266

Ml

AUG

H * WELL DEVELOPED AND
RIPE-RUNNING GONADS

□ «SPENT GONADS

N<I62

Ns39

N*245

N«76

NS32 9

SEP

SAMPLING PERIOD

N«3

N*I4

N*IO

Ns(9

OCT

Nsi4

Ns38

N«7

NOV

N:2

N«6

N<22
I

N=0

DEC

Fig.* 80. Number of mature yellow perch with well developed, ripe-running
and spent gonads collected monthly during June-December 1977 and April-
December 1978-1980 near the J. H. Campbell Plant, eastern Lake Michigan*
N = total number of mature yellow perch caught per month.

2^9

Septembei — Adult perch were prominent in our sampling area in September
of all years. Water temperature dropped rather drastically between August and
September 1977 (Fig. 22), yet relatively large numbers of adults were captured
in September. During 1978-1980 September temperatures were not greatly
different from those in August, and perch were caught primarily at depths less
than or equal to 9 ni.

October, November and December — Catches of adult perch dropped
precipitously after September. In general, falling temperatures and
decreasing catches were observed from October through December. Perch
appeared to move to deeper water during fall and remained outside our sampling
depths through winter.

Plant Effects —

From 1977 through 1980, yellow perch (larvae-adults) were sampled in
varying numbers at both north (plant) and south (reference) transects. No
consistent yearly catch pattern was evident for either transect. Results from
the Wilcoxon signed ranks test indicated that greater densities of perch
larvae were present at north transect stations than at south transect stations
in 1979- A relatively high mean larval perch density (60/1000 m^) at beach-3
m at the north transect in June accounted for the difference between
transects. Considering all 4 yr however, overall densities of perch larvae
were not significantly different according to the Wilcoxon test. Spawning
perch are attracted to rocky areas such as that present near the Campbell
intake and discharge structures, yet adult perch were not observed to
concentrate in this area during spawning season, probably due to dredging and
construction activities. However, perch were found near the riprap in
relatively large numbers at other times of the year, most notably during 1979*
Bottom gill net data for juvenile and adult yellow perch showed a higher
abundance of perch at the plant transect than at the reference transect during
1979 clue to an unusually low catch at station C (6 m, south) during that year
(Fig. 8l, Tables kG-k8) . In 1979f ^or trawl data, significantly greater
numbers of yellow perch were caught at the north transect than at the south
transect, due mostly to yearlings and adults which were captured in August and
September trawls (Fig. 82, Tables ^9 and 50). It was felt that these fish were
feeding on benthic organisms which were dislodged and suspended in the water
column by the dredging activity (Jude et al . I98O) . Relatively large YOY
catches at the south transect in August and September contributed to a
difference between catches at the two transects in I98O (Fig. 82). However,
this difference was felt to be due to spurious catches from the south
transect.

Since construction activities at intake and discharge structures were
completed during early I98O, it is likely that perch will be attracted to the
riprap area to spawn in I98I. If this occurs, perch spawning effort could be
influenced by plant operation. Perch spawning largely takes place at depths
from 5 to 9 ni, but may well extend to deeper water in the Campbell riprap area
due to the presence of suitable rock substrate. Campbell intake structures
are situated at about 11 m. Eggs deposited near intake structures would
probably not be affected by the low intake currents observed by SCUBA divers

250

YELLOW PERCH

ts

5 12

UJ

9

o

ii 3

Ul

tiJ

BOTTOM GILL NETS

STATION C
(REFERENCE)

STATION L

(PLANT)

1978

1979
TERR

1980

Fig. 31 . Geometric mean number plus one of yellow perch caught
in bottom gill nets at stations C (6 m, south) and L (6 m, north)
near the J. H. Campbell Plant, eastern Lake Michigan, 1978 through
1980. Graph illustrates YEAR X STATION interaction.

since perch would anchor their gelatinous rope- like egg masses in rocks.
Additionally perch larvae are fast growing and good swimmers at early ages.
Thus perch larvae at about 7 mm would be able to avoid both entrainment and
impingement at offshore intake screens. However, newly hatched perch or those
retaining their yolk sacs are inactive and passive so perch hatched near
intake structures may be subject to entrainment loss during their first few
days of life. Additionally, it is possible that larger larvae will be
entrained if they are attracted to intake structures to seek cover.

251

Table 46. Analysis of variance summary for yellow perch caught in
bottom gill nets at stations C (6 m, south) and L (6 m, north) near
the J. H. Campbell Plant, eastern Lake Michigan, 1977 through 1980,
Data for July through September were analyzed.

Attained

Source

of

significance

variation

df

Mean square

F-statistic

level

Year

3

0,85Ua

15.0814

<0.0001«*

Month

2

O.UGtiS

8.5522

0.0007«

Station

1

0.2996

5.2877

0.0259

Tine

1

0.3118

5.5043

0.0231

Y X K

6

0.4560

8.0486

<0.0001«

Y X S

3

1.2978

22.9065

<0.0001**

M X S

2

0.3587

6.3317

0.0036*

Y X T

3

'0.13U3

3.2531

0.0296

M X T

2

0.353U

6.2385

0.0039*

S X I

1

0.ia31

2.5252

0.1186

Y X M X

S

6

0.2565

4.5271

0.0010*

Y X M X

T

6

0.2603

4.5944

0.0009**

Y X S X

T

3

0.0600

1.0586

0.3755

M X S X

T

2

0.1342

2.3688

0.1044

Y X M X

S X T

6

0.2852

5.0345

0.0004**

Within cell

error

US

0.0567

** Highly significant (P < 0.001)
* Significant (P < 0.01) .

Table 47. Analysis of variance summary for yellow perch caught in
bottom gill nets at stations C (6 m, south) and L (6 m, north) near
the J. H. Campbell Plant, eastern Lake Michigan, 1978 through 1980.
Data for August and September were analyzed.

Attained

Source

of

significance

variation

df

Mean square

F-statistic

level

Year

2

1.1007

14.2074

O.COOl**

Month

1

0.1657

2.1391

0.1566

Station

1

1.5171

19.5817

0.0002**

Time

1

0.0316

1.0536

0.3149

Y X M

2

0.0747

0.9636

0.3958

Y X S

2

0.6156

7.9461

0.0022*

H X S

1

0.2640

3.U077

0.0773

Y X T

2

0.1537

1.9839

0.1594

M X T

1

0.0017

0.0224

0.8824

S X T

1

0.0262

0.3384

0.5662

Y X M X

S

2

0.1434

1.8516

0.1787

Y X M X

T

2

0.0342

0.4412

0.6484

Y X S X

T

2

0.1194

1.5418

0.2345

M X S X

X

1

0.2107

2.7200

0.1121

Y X M X

S X T

2

0.2351

3.0345

0.0668

Within cell

error

24

0.0775

** Highly significant (P < 0.001).
* Significant (P < 0.01) .

252

Table 48. Analysis of variance summary for yellow perch caught in
bottom gill nets at stations C (6 m, south) , D (9 m, south) , L (6 m,
north) and N (9 m, north) near the J, H. Campbell Plant, eastern Lake
Michigan, 1980. Data for August and September were analyzed.

Attained

Source

of

significance

variation

df

Mean square

F-statistic

level

Month

0.1721

2.6400

0.0920

Area

0.2102

3.2238

0.0852

Depth

3. 2142

49.3060

<0.0001«

Time

0.89O8

13.6650

0.0011*

M X A

0.5626

8.6302

0.0015*

M X D

0.1195

1.8338

0.1815

A X D

0.0021

0.0328

0.8578

M X T

*0.055U

0.8498

0.4400

A X T

0.36U3

5.5885

0.0265

D X T

0.1223

1.8763

0.1834

M X A X

D

o.oaa9

0.6885

0.5120

M X A X

T

0.0998

1.5316

0.2366

M X D X

T

0.1580

2.4243

0.1099

A X C X

T

0.0018 .

0.0283

0.8678

M X A X

D X T

0.7732

11.8615

0.0003**

Within cell

error

2«*

0.0652

** Highly significant (P < 0.001)
* Significant (P < 0.01) .

Table 49. Analysis of variance summary for yellow perch caught in
trawls at stations C (6 m, south) and L (6 m, north) near the J. H.
Campbell Plant, eastern Lake Michigan, 1977 through 1980. Data for
July through September were analyzed.

Attained

Source

of

significance

variation

df

Mean square

F-statistic

level

Year

0.6112

17.1218

<0.0001**

Month

1.2567

35.2626

<0.0001**

Station

0.2269

6.3579

0.0151

Time

0.3179

8.9070

0.0045*

y X M

1.3690

38.3528

<0.0001**

y X s

0.4011

11.2374

<0.0001**

M X S

0.2239

6.2724

0.0038*

y X T

0.4833

. 13.5393

<0.0001**

M X T

0.2604

7.2957

0.0017*

S X T

0.0081

0.2260

0.6367

y X M X

c

0.5006

14.0234

<0.0001**

y X M X

i

0.2892

8.1030

<0.0001**

y X s X

T

0.0649

1.8169

0.1567

H X S X

T

0.1672

4.6831

0.0139

y X M X

S X T

6

0.3279

9.1869

<0.0001**

Within cell

error

48'

0.0357

** Highly significant (P < 0.001).
* Significant (P < 0.01) .

253

Table 50. Analysis of variance summary for yellow perch caught in trawls
at stations C (6 m, south), D (9 m, south), L (6 m, north) and N (9 m,
north) near the J. H. Campbell Plant, eastern Lake Michigan, 1978 through
1980. Data for July through September were analyzed.

Attained

Source

of

significance

variation

df

Mean square

F-statistic

level

Year

2

0.7058

18.2942

<0.0001«*

Month

2

1.2840

33.2792

<0.0001**

Area

1

0.3126

8.1015

0.0058*

Depth

1

0.2623

6.7988

0.0111

Time

1

0.0266

0.6890

0.4093

Y X M

4

2.0707

53.6723

<0.0001««

Y X A

2

1.1452

29.6831

<0.0001*«

M X A

2

0.2370

6.1416

0.0034«

Y X D

2

0.5090

13.1926

<0.0001««

M X

2

0.0647

1.6760

0.1943

A X

1

0.1152

2.9847

0.0883

Y X T

2

0.3456

8.9568

0.0003**

M X T

2

0.0375

0.9729

0.3829

A X T

1

0.0135

0.3488

0.5566

D X T

1

0.5532

14.3384

0.0003**

Y X M

X

A

4

0.1778

4.6074

0.0023*

Y X M

X

D

u.

1.0807

28.0113

<0.0001**

Y X A

X

D

2

0.0690

1.7877

0.1747

M X A

X

D

2

0.1190

3.0849

0.0518

Y X M

X

T

4

0.0714

1.8508

0.1285

Y X A

X

T

2

0.0553

1.4324

0.2455

H X A

X

T

2

0.0685

1.7764

0.1766

Y X D

X

T

2

0.4713

12.2148

<0.0001**

M X D

X

T

2

0.4967

12.8737

<0.0001««

A X D

X

T

1

0.0016

0.0419

0.8384

Y X M

X

A X

D

4

0.9327

24.1762

<0.0001**

Y X M

X

A X

r

4

0.3546

9.1902

<0.0001**

Y X M

X

X

T

4

0.4625

11.9875

<0.0001**

Y X A

X

D X

I

2

0.1965

5.0922

0.0085*

N X A

X

D X

T

2

0.2970

7.6992

0.0009**

Y X M

X

A X

D X T

4

0.5201

13.4819

<0.0001**

Within

\ cell

error

72

0.0386

*« Highly significant (P < O.OOl) .
* Significant (P < 0.01) .

25^

6 YELLOW PERCH

STATIONS C AND D

(REFERENCE)

5 ~ STATIONS L AND N

i3 + (PLANT)

o

QJ <

1978 1979 1980

YEAR

Fig. 82. Geometric mean number plus one of yellow perch caught in

trawls at stations C (6 m, south), D (9 m, south), L (6 m, north) and N

(9 m, north) near the J. H. Campbell Plant, eastern Lake Michigan, I978

through I98O. Graph illustrates the YEAR x AREA interaction.

LESS ABUNDANT SPECIES

Lake Trout

I ntroduction —

Lake trout- are naturally occurring and widely distributed throughout
northern North America. Southern Lake Michigan marks the southern-most
extension of the species' natural range, although they have been widely
introduced (Scott and Crossman 1973). Lake trout are characteristically found
in the cooler, hypolimnetic region of cold-water lakes. In the Great Lakes
this species is usually most abundant at depths between 30 and 9I m at or near
the bottom, but may occur in open water (Eschmeyer 1957). Midsummer movement
of lake trout into nearshore areas of southeastern Lake Michigan has been
observed when upwelling conditions prevail (Jude et al . 1979a, I98O) .
Spawning occurs in the fall. Historically, mature fish migrated to their
native reefs, typically rocky, current-swept shoals at depths of up to 30. 5 m
(Eschmeyer 1957) .

255

Attempts to reestablish lake trout in Lake Michigan following their near
extinction due to combined effects of overfishing and lamprey predation during
the 1930s and 1940s, resulted in the planting of yearlings in shallow,
nearshore areas. Consequently, fall spawners of late (1969 to present) are
believed to be returning to spawning areas that are shallower and possibly
less suitable for natural reproduction than historical spawning reefs (Rybicki
and Keller 1978; Dorr et al. I98I) .

During I98O, 513 lake trout were collected in Lake Michigan near the J.
H. Campbell Plant including kk2 adults (330-950 mm), 10 juveniles (110-280 mm)
and 61 larvae and fry (22-62 mm). This represents a two-fold increase over
previous annual catches of 201, 258 and 222 in 1977t 1978 and 1979
respectively (Jude et al. 1978, 1979a, I98O) .

Larvae —

Collection of 6I lake trout fry in our study area during spring and
summer I98O documents successful reproduction in southeastern Lake Michigan
for the first time since the species was reintroduced from hatchery stocks in
1965 (Jude et al. 198lb) . Presumably hatched in late February-March 1980, fry
(26-27 mm) (some were sac fry) were first collected in April at station (12
m, north) (one) and W (15 m, north) (one) in the immediate vicinity of the
riprap-covered intake pipe (Fig. 83). In May greater numbers of fry were
collected (^7) . Their occurrence at both north and south transects, in 3 to
15 m of water indicates dispersal of fry up to 5 km away from the presumed
site of incubation (Jude et al. 198lb) . The greatest number of fry were
captured at station N (9 m, north) (19) and station E (12 m, south) (17) in
both trawls and larval sled tows. Four fry (37-^3 »™) were collected in June,
all at the south transect at 3-t 12- and 15-m stations. Mean July water
temperature at 12 and 15 m, which exceeded 15 C (Fig. 22), was sufficiently
high to force fry in the vicinity to seek deeper colder water. Lower offshore
water temperatures in August (7.0-7-5 C) permitted reentry of fry into our
study area as three (55-62 mm) were captured at station F (15 m, south) .

Juveni les —

Juvenile lake trout (kk fish, 110-276 mm) occurred infrequently within
our study area during all years (1977-1980). Most (40) were col lected in
trawls and a few (4) were gill netted. Seventy-three percent were captured at
depths of 9 m or greater. A size-depth relationship has been evident for lake
trout in southeastern Lake Michigan with average length of fish decreasing
with depth (Great Lakes Fishery Laboratory 1972).

The preferred temperature for yearling lake trout (11.7 C) is thought to
be about 2 C warmer than the temperature at which lake trout are most often
caught in thermally stratified lakes (McCauley andTait 1970). Young lake
trout were present inshore (1.5-"3 m) during spring months (May and June, Fig.
84) in 1980 and 1979. Temperatures at the time of capture were 12.7 C at
station A (1.5 m, south) in May 1979 and 14.5 C at station B (3 m, south) in
June 1980. Juveniles were also captured nearshore at station L (6 m, north)
in July 1978 and 1979 (Fig. 84), when water temperature data (Fig. 22)

256

1980
FRY

,.^^'

.^^

\P^^^^^^^^^^^^^^'^

' ;J^^>^^ ^^""^ ;ov^^>i<^'-s^^^oC'^^^o>i^ o^^

° .<^

Fig. 83. Numbers of lake trout fry collected in trawls and larval sled
tows for each month and station during I98O, near the J. H. Campbell
Plant, eastern Lake Michigan.

indicated upwel lings existed. Unlike adults, young lake trout remain in
deeper water during the fall and are therefore not as susceptible to capture
in our study area during that time.

Adults-
Adults comprised 91% of all lake trout collected over the i*-yr study
period. Eighty-seven percent of the II67 adults collected were captured at
night, with annual percentages ranging from 80 to 90%. Jude et al . (1979b)
reported night catches of lake trout in southeastern Lake Michigan near the
D. C. Cook Nuclear Plant ranging from 83 to 91% (1973-197^) • The authors
attributed these high percentages to fall spawning activity which is known to
be a nocturnal event for this species (Scott and Crossman 1973)* This
explanation seems plausible here since the majority of all adult lake trout
captured in our study area were collected during the spawning season, from
September to November.

Gill nets were responsible for catching over 97% of adult lake trout in
each of the 4 yr studied. At stations where both surface and bottom gill nets
were set [stations C (6 m, south); L (6 m, north); U (6 m, north) set only in
I98O; and D (9 m, south) set only in 1977]. 67 to 71% of the catch occurred in
bottom gill nets. Two adult lake trout were trawled in I98O, one at station E
(12 m, south) in April and one at station B (3 m, south) in October. Three
were collected in trawls during 1979» none in 1978 and one in 1977- Few lake
trout were collected in seine hauls: I98O (0); 1979 (0); 1978 (10); 1977 (3).

257

1977

MONTH

1978

MONTH

< ,>-% ►-' r . .*t^J^^lifl^*^ _.

MONTH

Fig. 84. Numbers of adult and juvenile lake trout collected in all gear
for each month, station and year near the J. H. Campbell Plant, eastern
Lake Michigan, 1977 through 1980. D = juveniles, ■ « adults, O =
standard schedule gillnetting not performed, ^ = surface gill net, dashed
line indicates no sampling performed. Refer to METHODS (Tables 1 and 2)
for standard sampling schedule.

258

MONTH

MONTH

Fig. 84 . Continued.

259

Temperature is a major factor influencing the distribution of lake trout.
Spigarelli (1975) determined the preferred temperature for adults of this
species in the nearshore area of Lake Michigan in the vicinity of a power
plant discharge to be 11.8 C. In I98O over 95% of the lake trout caught in
our study area were in water 15 C or less (Appendix 2) . Comparable
temperature-catch relationships were observed from 1977 through 1979 (Jude et
al. 1978, 1979a, 1980) .

During spring of all study years, monthly mean water temperatures at
6- and 9"n» gin net stations ranged from 2.4 to 5*9 C in April, 6.6 to 11.5 C
in May and 6.3 to 14.0 C in June (Fig. 22). Temperatures at 1.5" and 3"^ gill
net stations for the same period were somewhat higher, yet within a range that
lake trout would be likely to occur, 6.8 to 9-9 in April; 8.3 to I3.8 in May
and 9*9 to 17-3 C in June. Few adult lake trout however, were captured during
these months (Fig. 84). Largest catches occurred in I978 when 82 fish were
collected, while abundances in I98O and 1979 were 41 and 24 fish respectively.

Analysis of stomach contents indicated lake trout were actively feeding
in the study area from April through June, as 80% of those examined contained
food. Rainbow smelt were present in 42% of the stomachs containing food in
April; this percentage dropped to 6% in June. Alewives increased in abundance
as a food item from I8 to 62% for the same period. The relatively low spring
catch of lake trout in 1979 may have been influenced by the relatively low
abundance of forage fish in the study area. Numbers of rainbow smelt (305)
and alewives (0) collected in April 1979 were low compared to a greater
abundance in I978 (1093 rainbow smelt, 21 alewives) and I98O (2089 rainbow
smelt, 152 alewives) (Table 10). Furthermore, the offshore movement of lake
trout into deeper water, necessitated in late spring by rising nearshore water
temperatures, may have been initiated earlier in 1979 than in 1978 or I98O
because of the rapid warming of inshore water from April to May (Fig. 22).

Lake trout were present inshore during the summer (July and August) when
suitable temperatures were available. Cold-water upwel lings in July 1977.
1978 and 1979 permitted nearshore residence of lake trout. Rising
temperatures from July to August all but eliminated lake trout from the area
in 1978 (five fish captured) and 1977 (one fish captured), while large catches
in 1.5- and 3"'" gill nets attested to the availability of suitable
temperatures in 1979- Mean July water temperatures of 19*9 and 21.0 C at
6- and 9""^ stations excluded lake trout from our study area in I98O (Fig. 22,
Fig. 84). A sparse August catch of three fish reflects limited inshore
movement, as bottom temperature dropped within a more tolerable range for the
species.

The fall spawning migration of lake trout into shallow, nearshore areas
produced seasonal high abundances during all study years. The combined
September, October and November catch of 836 represented 77% of all adults
collected. Fifty-seven percent of these fish were found to be in spawning or
near spawning condition as indicated by gonad condition data. Examination of
stomach contents suggests that most of these fish were not feeding in the
area. Greatest catches occurred at 1.5''» 3" and 6-m stations. Shallow,

260

inshore areas have been reported to attract large concentrations of spawning
lake trout presumably as a result of stocking yearlings in such areas to which
planted stocks "home" as adults (Rybicki and Keller 1978),

During I98O, 387 adult lake trout were collected from September through
November. Notably fewer fish were captured during this period in 1979 (U6)
and 1978 (146). The aggregation of mature fish over nearshore spawning areas
appeared to begin in September, peaked in October and declined in November
when spent individuals began to appear (Fig. 85). The large number of lake
trout collected in September 1977 suggests that the cumulative fall catch for
this year may have equalled that of I98O. However, gill net sampling
necessary to confirm this contention was not performed in October 1977.

Successful lake trout spawning and reproduction in our study area during
fall 1979 was evidenced by the occurrence of lake trout fry in spring and
summer samples the following year (Fig. 83). Stomach analysis of 10 round
whitefish collected in fall I98O disclosed the occurrence of lake trout eggs,
ranging in abundance from 1 to 50 eggs per individual. One of these fish was
captured in October. The remaining nine were caught in November at both north
and south transects, suggesting that lake trout spawning had occurred in the
vicinity of our study area during I98O. There have been other reports of lake
trout spawning in nearshore areas of southeastern Lake Michigan. An estimated
100,000 lake trout eggs were observed along the Lake Michigan shoreline in the
vicinity of the D. C. Cook Plant in November I975 (Jude et al. 1979a).
Occurrence of these eggs followed an intense storm that passed through the
area the day before.

Examination of lake trout for lamprey scars revealed an overall decline
in the frequency of attacks from I977 through I98O. Twenty-three percent of
i*28 fish examined in I98O had lamprey scars (Table 51). This value along with
the 2k% observed in I979 substantiated a downward trend in scar frequency from
1978 (36%) and 1977 (27%) (Jude et al. 1980, 1979a, 1978). Other authors have
reported scarring rates of 25% in Indiana waters of Lake Michigan (McComish
and Miller 1975) and 22% near the D. C. Cook Plant (Jude et al . 1979b).
Occurrence of fresh lamprey wounds on only 2% of the lake trout examined in
1980 suggests low lamprey activity within our study area.

Plant Effects-
Several noteworthy observations on the distribution and abundance of lake
trout during the k yr of preoperational data collection deserve special
mention. Most significantly has been the unique occurrence of lake trout fry
in 1980. It is believed the newly laid riprap covering the intake pipe
provided a suitable environment for egg incubation during the previous winter
(1979-1980). This type of substrate is similar in structure to historical
spawning reefs, protecting the indiscriminately dispersed eggs from severe
wave action and ice scour, which could otherwise damage unprotected eggs
occurring on sand bottoms.

261

160

1977

^^i □'SPENT GONADS

80

40

Q

LU

h- 160

O

LU

-J I20^

-J

o

^ 80-1

X

UJ 160

cr

ZD

H 1201

<

80-1

o

40

LU
CD

UJ

^ 160
^ I20H

80

40

»WELL DEVELOPED AND
RIPE-RUNNING GONADS

N3II9

Ns40

L

NO HO N.2 ■_ ^" ■ '^" N«l

1

1978

Ns92

Ns93

Ns29 N:32 f^^'d N'lO '^^ l^'l H N«0

1979

Ns87

Ns24

Ns35
N'lO Ns8 '^ N*I3 ■ fM NsO

I

Ns207

1980

Nsll9

Nsl6 Ns7 N«I7 N«5 '*'* H H^ NsQ

N<6i

I

APR mIy JUN JUL AUG SEP OCT NOV DEC

SAMPLING PERIOD
Fig. 85. Number of mature lake trout with well developed, ripe-running
and spent gonads collected monthly during June-December 1977 and April-
December 1978-1980 near the J- H. Campbell Plant, eastern Lake Michigan.
N = total number of mature lake trout caught per month.

262

Table 51* Occurrence of sea lamprey scars on lake trout caught near
the J. H. Campbell Plant, eastern Lake Michigan, I98O.

Length

Total

No.

scars

per fish

1 nterva 1

Number

Number

P&rr^nt

1 1 1 !• ^ 1 vol

(mm)

1^ \Jlllh/ W 1

Examined

1^ will V ^ 1

Scarred

Id W wl 1 1.

Scarred

1

2

3 4

900-949

1

850-899

5

3

60

3

8OO-8A9

15

8

53

4

1

3

750-799

74

26

35

18

6

1 1

700-749

105

32

30

29

2

1

650-699

147

25

17

22

2

1

6OO-6A9

52

3

6

2

1

550-599

17

1

6

1

500-549

4

450-499

2

400-449

350-399

300-349

250-299

1

200-249

150-199

1

100-149

4

Total

428

98

207

79

12

6 1

Differences in the fall abundance of lake trout between plant (north) and
reference (south) transects were evident in I978 and 1979 (Table 5I) .
Consistently greater catches from September through November at north transect
stations occurred while there was a high level of construction activity in the
area, including dredging for the deposition of riprap. However, during the
years of greatest lake trout abundance (I98O and most likely 1977),
construction activity in the vicinity of the plant transect was absent and
catch differences between transects were not as obvious. Temperature
differences in November I98O between stations U (6 m, north) and L (6 m,
north), which lie north and south of the offshore discharge, revealed the
presence of the thermal plume. These water temperature differences appear to
have influenced the distribution of lake trout in the immediate vicinity
(Table 52). Colder water (5 C) at station U (6 m, north) attracted greater
numbers of lake trout (31) than plume-i nf 1 uenced station L (6 m, north) (15
fish, 9 C) . An intermediate catch (19) was observed at reference station C (6
m, south) where water temperature was 5.8 C.

263

Table 52. Number of lake trout collected in bottom and surface gill nets
set in Lake Michigan in September, October and November 1977-1980 at
stations L (6 m, north) designated as north and C (6 m, south)
designated as south. Day and night catches were pooled. Water
temperature, in degrees Celsius, at time of capture is enclosed in
parentheses. # denotes operation of 6-m offshore discharge; ##
denotes operation of onshore discharge; ** denotes presence of
introduced substrate such as riprap in the discharge area; ###
denotes construction activity in the discharge area. ND denotes
no data.

Transect

Month

Year

Sep

Oct

Nov

Total

1980

#
**

North (plant)

South (ref.)

Total

13
(16.2)

7
(15. 2-13.0)

39
(12.0)

(10.5)

15*
(9.0)

19
(5.8)

67
80

147

1979

North (plant)

5

21

10

36

it*

(14.0-11.7)

(13.7-13.0)

(8.5-6.9)

###

South (ref.)

2

11

1

M*

##

Total

(14.5)

(13.5-13.0)

(7.2)

-50

1978

North (plant)

1

24

12

37

**

(13. 5)

(12.9-12.0)

(9.0)

###

South (ref.)

11

2

13

##

Total

(19.8-15.6)

(12.5-11.7)

(8.5)

50

1977

North (plant)

25

ND

1

26

##

(10.6-6.0)

(15. 3)

South (ref.)

23
(9.0-7.3)

ND

k
(10.6)

27

Total

53

* November gill net catch of lake trout at station U (6 m, north) was
31; water temperature was 5 C.

264

White Sucker

I ntroduct ion —

White sucker was the eighth-most abundant species taken in Lake Michigan
during 1980, There were 392 individuals collected, representing 0,^7% of the
total catch. During the k yr of the study the importance of white suckers in
the total catch was between 0.3 and 0.6% (Jude et al. 1978, 1979a, 198O) . In
1977. 294 white suckers were collected; 319 were taken in I978 and ^13 in
1979. White suckers comprised only 0.1% of the catch in 1973-197^ «n
southeastern Lake Michigan near the D. C. Cook Nuclear Power Plant, Bridgman,
Michigan (Jude et al. 1979b).

Larvae —

In April, adult white suckers in the study area migrate into streams to
spawn. Sucker larvae were captured infrequently in the Campbell Plant
vicinity because they spend at least 1 mo in streams before moving down to the
lake (Geen et al. I966) . In the early years of the study, sucker larvae could
not be identified to species; however, since white suckers are the most common
catostomid .in the study area, most sucker larvae collected were probably white
suckers. During our study, only two sucker larvae were captured in Lake
Michigan; one in April and one in July 1979 at depth contours of 1 and 3 m
respectively. These larvae were 10.0 and 12.0 mm TL. Sucker larvae were also
taken in entrainment samples at Units 1 and 2 during May I978 and 1979.
indicating spawning took place during April and early May in the Pigeon River.
The larva caught in July 1979 may have been spawned during an upwelling which
took place that year, although spawning in Lake Michigan is not documented for
white suckers. This larva more likely originated from a late spawning in the
Pigeon River.

Young-of-the-Year and Yearlings —

Growth rates of white suckers vary considerably among studies, making
separation of year classes difficult. Koehler (1978) found that white sucker
YOY near Ludington averaged 100 mm and yearlings averaged 225 mm. Other
studies (Car lander I969; Hubbs and Creaser 1924) found YOY no larger than 70
mm by August. Few small white suckers have been collected near the Campbell
Plant. In 1977. 1978 and 198O, a few fish smaller than 7^ rnm (probably YOY)
were captured, all in beach seines in July and August. White suckers 75"244
mm (probably yearlings) were also infrequent and scattered in catches, being
captured both in seines and in bottom gill nets from the 3" to 12-m contours.
At the D.C. Cook Plant all white suckers less than ]kk mm were col lected with
beach seines, and no ]h5^2kk-mm fish were taken (Jude et al. 1979b).

YOY white suckers collected near the Campbell Plant and the Cook Plant
had newly emerged from streams, as evidenced by their small size (most were
50-65 mm) and restriction to the beach zone. Scarcity of YOY and yearlings,
compared with adults, suggests most young white suckers remain in streams up
to 1 yr before moving downstream to Lake Michigan. Those white suckers

265

emerging from streams in their first year inhabit the beach zone only briefly
before moving offshore out of our sampling area, or undergo considerable
mortal i ty .

Adults-
Adult white suckers were captured most effectively by bottom gill nets
during the k yr of our study and near Ludington (Liston and Tack 1973)* This
was probably due to this species' benthic habits and physical structure.
Demersal fish are not usually caught in surface gill nets, while trawls and
seines are more easily avoided by large fish. White suckers ranged from 25 to
GOk mm in samples from all gear, but most fish caught were between 300 and 500
mm.

White sucker adults were not captured during April from 1978 to I98O (in
1977» sampling did not begin until June). In April white suckers spawn in
streams, and thus might not be expected to occur in Lake Michigan samples
(Fig. 86). By May, 1977"1980, many adults had emerged from the streams and
many had spent gonads. The greatest catches during May were at stations C (6
m, south) and D (9 m, south) .

June catches of white suckers during the 4 yr were similar in number to
May; a greater proportion of fish had only slightly developed gonads,
indicating spawning was largely finished by that time. In 1977 and 1979* July
catches were high (Fig. 86), particularly at stations A (I.5 iri, south) and B
(3 m, south). Upwel lings of cooler water occurred in July of both years and
possibly led to an inshore movement of suckers. In 1978 and I98O catches of
adult white suckers in July were similar to June catches.

In August the number of white suckers captured appeared to vary
inversely with water temperature; in 1977 and I98O August catches were high at
lower temperatures, while in 1979 water temperatures were warmer in August
than in July and catches decreased (Figs. 86, 22). From I978 to I98O, highest
catches of white suckers occurred in September, with relatively high numbers
observed in 1977 as well. In 1977 the September catch was highest in the
nearshore zone (beach to 3 m) , while in other years white suckers were more
abundant at 3-12 m. Fish with well developed gonads generally began to appear
more frequently in September.

In October, November and December white suckers appeared to have moved
offshore, beyond our sampling stations. In all k yr the numbers of white
suckers taken during these months were much lower than in September (Fig. 86).

White suckers were captured much more frequently at night than in the
daytime. Water temperatures at which suckers were captured ranged from 4.0 to
25.9 C; in 1980 highest catch was at 14 to I6 C, while in 1979 large catches
were observed at somewhat lower temperatures, 9"13 C. In I978 white suckers
were captured at higher temperatures with most caught at 18-19.9 C. In 1977f
white suckers were captured primarily at water temperatures of 6-12 and 18-22
C; fish of the same size were caught at both temperature ranges. Relative

266

75-

25-

75-

X

o

= 25-1

o

<2

Ul

125-

UJ

m

3
Z

75

25-

75-

25-

1977

□ day

■ NIGHT

NO

NO

I

J

1978

rai rl

1979

I

,1

1980

APR

MAY

J

JUN

JUL

SEP

OCT

NOV

DEC

AUG
MONTH

Fig. 86 , Number of white suckers collected by all gear during day
and night sampling once per month June to December 1977 and April to
December 1978-1980, near the J. H. Campbell Plant, eastern Lake Michigan.

267

scarcity of fish caught between 12 and l8 C in 1977 may be due to less
frequent occurrence of these temperatures during 1977 sampling periods, rather
than actual temperature preference by white suckers.

In the vicinity of the D. C. Cook Power Plant, more female than male
white suckers were collected (62% females in 1973 and 69% in 197^) (Jude et
al. 1975). However, in the Campbell Plant study areas the sex ratio was more
balanced, with 50 to 53% females collected during 1977-1980.

Neoplastic lesions have been observed on the heads, usually the lips, of
white suckers in southeastern Lake Michigan (Jude et al. 1979b). Lesions were
found infrequently on fish caught in our study; six were observed in 1979 and
one in I98O.

Plant Effects-
Plant impacts were difficult to assess, since the number of white
suckers caught was insufficient for statistical analysis. Sucker larvae were
so seldom encountered in field sampling that no comparisons can be made
between transects. However, data for all k yr show five times as many adult
white suckers were caught at south reference transect station C (6 m) as at
north transect station L (6m). Also, studies in the vicinity of the
D. C. Cook Plant indicated that more white suckers were caught at the
reference transect than in the vicinity of the plant (Jude et al. 1979b).
White suckers usually prefer cooler waters; however, water temperatures were
not consistently higher at the north transect. In the latter years of the
study, construction activity may have caused white suckers to avoid the north
transect area, but we feel that the south transect area was in some way more
attractive to white suckers than the plant transect.

Johnny Darter

I ntroduction —

Although not classified as a major species in terms of numbers of fish
caught, johnny darters were among the top 10 species in numerical abundance
during the period 1977-1980. This demersal species was caught almost
exclusively in bottom trawls in Lake Michigan during the preoperational study
period, mostly at night. Because of their size and shape they are not caught
by our gill nets. Their near absence from beach seine hauls during 1977-1980
suggests little use of the beach zone.

Larvae —

During the 4-yr preoperational study, adult johnny darters were quite
common in the study area; however, collections of darter larvae were
infrequent compared with adult catches. Winn (1958) reported that johnny
darters spawn under rocks, logs and other objects and that the young are
guarded by the adults. Therefore, the larvae may not be very susceptible to

268

our sampling gear. One larva each was caught in 1977 and 1978, 9 in 1979 and
105 in 1980. Distributional patterns of larval johnny darters were only
evident in I98O, the year of their greatest abundance.

The first occurrence of johnny darter larvae in I98O was during early
June at the 6-m south station. Densities of 32 larvae/1000 m^ were noted at
this time (Appendix 9). During late June, I98O, nearly 70 larvae/1000 m^ were
found at the north transect beach station Q (Appendix 8). In early July,
1980, densities of 30-70 johnny darter larvae/1000 m* at the 9-, 12- and 15-m
north transect stations were observed (Appendix 8). Late July sampling in
1980 revealed johnny darter larvae again at north transect 6-, 9"t 12- and 15"
m stations; the highest density (87 larvae/1000 m^) occurred at the 9"ni
station. Water temperatures were nearly equal at all of those stations,
ranging from 20.3 to 25-3 C. Johnny darter larvae were also caught at south
transect 9*" and 12-m stations with densities of 57 and 267 larvae/1000 m^
respectively at this time. Water temperatures were approximately 21 C at the
bottom stratum where johnny darter larvae were collected at both stations.

During early August 1980, johnny darter larvae were caught at both
transects with the highest density of the year occurring at 9 m, north (I7OO
larvae/1000 m^) . Concurrently, densities of 828 larvae/1000 m^ were found at
the 9"n» south station. Although johnny darter larvae were caught at both
transects in late August I98O, highest densities were found at north transect
stations; 625 larvae/1000 m^ at 9 m north in contrast to 197 larvae/1000 m^ at
9 m south. During September 1980 low densities (87 and 26 larvae/1000 m^) of
johnny darter larvae were found at 1 .5- and 6-m north stations.

Johnny darters in Lake Erie hatched at 5.0 mm TL (Fish 1932). Our data
showed that johnny darter larvae caught in early June had a mean length of 5*6
mm indicating they were newly hatched. Occurrence of 6.2-mm larvae in early
July indicates that hatching and spawning were taking place at that time. A
median length of 6.2 mm in mid-July suggests that spawning and hatching
continued through July I98O. By mid-August I98O median size of johnny darter
larvae had reached 11. 7 mm, suggesting that spawning had halted by that time.
By mid-August the median size had reached 16. 5 mm and increased to 24.5 mm by
September.

Adults—

Seasona 1 d i s tr i but i on —

Introduction — During the study period (I977-I98O) a predictable pattern
of inshore and offshore movement was exhibited by adult johnny darters. A
pre-spawning movement to inshore waters was quite evident by May. Jude et
al. (1975» 1979b) documented that johnny darters spawn during late May, June
and July in southeastern Lake Michigan. After spawning, a movement to deeper
water was observed. The majority of johnny darters during July and August
were caught at 6- and 9"ni depths during the 4-yr study period. As autumn
approached, a movement to deeper water began. Most fish collected during
September and October were trawled at the 9- and 12-m contours. Catches

269

declined during November and December with most caught at 12 and 15 m.
Although collections were not attempted during January-March, it is suspected
that johnny darters inhabit water beyond the 15~ni depth contour.

April — During 1978 no johnny darters were caught in April. Small catches
of johnny darters occurred during April 1979 and I98O; less than 25 fish were
caught. These fish were trawled at 9 and 12 m indicating that the bulk of the
population was in water deeper than 15 ni.

May — Increased numbers of johnny darters entered the study area in May.
During I98O, May was the month of maximum catch for the entire year; 80 fish
were caught and all but one were adults (3^""57 mm), most likely moving inshore
to spawn.

June and July — After spawning, johnny darters move into deeper water
overlying sand and gravel (Winn 1958). This pattern appeared to be exhibited
near the Campbell Plant. During June 1977» II6 johnny darters were collected;
of theses 86 were trawled at 6 and 9 n). During June I978-I98O the largest
catch was also at 6 m with a few caught at 9 "^ and none beyond 12 m. July
catches during 1977"1980 were much like June with concentrations at 6 and 9 ni.
Jude et al. (1975) found a similar distribution of johnny darters near the
Cook Plant in southeastern Lake Michigan. All fish caught in June and July
were adults.

August-Decembei — During August johnny darters were noted at 6, 9 and 12
m. None were caught at 15 ni during 1977"1980. Densities of johnny darters
increased with depth from September to December. During September catches
were almost all at the 9" and 12-m contours. The bulk of the October and
November catch during 1977*1980 was collected at 12- and ]5^^9 while in
December largest catches occurred at 15-ni.

Johnny darters were caught primarily at night (85% of the 1977*1980
catch) and most (95^) were adult fish 40-70 mm. Johnny darters were caught at
water temperatures from 4 to 23 C in Lake Michigan during the period
1977*1980. This wide range of temperatures indicates johnny darters exhibit
no distinct preferred temperature. Movement to a preferred seasonal depth in
contrast to distribution governed by temperature preference is indicated by
data collected from 1977 to I98O. Gonad development data collected over the
preoperational period showed a near equal sex ratio of 317 females to 271 male
johnny darters.

Plant Effects—

The large increase in johnny darter larvae observed in I98O was most
likely the result of the riprap at the north transect where darter larvae
densities were markedly higher. The riprap is ideal habitat for adult johnny
darters providing both foraging and spawning habitat. SCUBA observations
confirmed the increased abundance of johnny darters on the riprap; they are
one of the most frequently observed fish. Preliminary observations in I98I
noted densities as high as 40 johnny darters/m* on the riprap. Jude et
al • (1979b) reported an increase in johnny darters on the riprap at the Cook

270

Plant In southeastern Lake Michigan. There surely will be an increase in
numbers of johnny darters in the study area due to the riprap. Additionally,
the spawning habitat in the area immediate to the intake may result in
considerable entrainment of johnny darters by Unit 3.

Emerald Shiner

I ntroduction —

The emerald shiner is a pelagic species inhabiting lakes and large
rivers. Emerald shiners are characterized by considerable fluctuations in
abundance (Scott and Grossman 1973). In Lake Michigan emerald shiner
populations drastically declined from extreme abundance in the 1950s to
scarcity in the 1960s, coincident with the increase in alewife populations
(Wells and McLain 1972). Emerald shiners and alewives are both shallow-water
planktivores, thus their population interactions may be due to competition for
food (Smith 1970) or predation by alewives on the eggs and larvae of the
shiner (Crowder I98O) .

Emerald shiners spawn from June to August in Lewis and Clark Lake, South
Dakota (Fuchs I967) and western Lake Erie (Flittner 1964). Spawning in Lake
Erie occurred inshore, over clean sand and hard, mud bottoms. First evidence
of spawning was not observed until lake surface temperatures exceeded 22 C
(Flittner 1964) .

Emerald shiners exhibit schooling behavior with schools of YOY moving
inshore in autumn. Groups of adults stay offshore in summer and overwinter in
deep water (Scott and Grossman 1973) .

In our study emerald shiners were uncommon in Lake Michigan, comprising
less than 0.06% of the catch from 1977 to 1979. In I98O, however, the
proportion of emerald shiners increased to 0.29% of the total, catch. Two
hundred forty-seven were collected in adult sampling gear in 1980, compared
with 1 in 1977, 50 in 1978 and 7 in 1979.

Spawning of emerald shiners in Lake Michigan was not documented by our
study, though it undoubtedly occurred in times of population abundance, prior
to i960. Areas of Pigeon Lake influenced by Lake Michigan offer suitable
habitat for emerald shiner reproduction (Jude et al. I98O) . Many YOY were
collected in October 1978 and yearlings were collected In spring I979 in
Pigeon Lake, indicating a strong year class was produced in I978. This timing
coincides with a relatively low catch of alewives in 1978, while in I977 and
1979 alewives were abundant and YOY emerald shiners less so. This suggests
possible competition between the two species. Size of the Lake Michigan catch
may also reflect the strong I978 year class produced in Pigeon Lake. However,
the characteristic irregularity of emerald shiner abundance and their
schooling behavior may account for this apparent increase. At times, schools
of emerald shiners may have inhabited the study area but were not captured.

271

Larvae —

Analysis of emerald shiner larvae data is complicated by the difficulty
of identification at early stages. In 1977 and 1978, all minnow larvae less
than 9 ni"i (except carp) were classified as unidentified Cyprinidae. By 1979»
characters were defined for separating emerald shiners, spottail shiners,
golden shiners and bluntnose minnows. Therefore in 1979 and I98O more emerald
shiner larvae were identified from our collections than in 1977 and 1978.

In 1977 no emerald shiner larvae were identified. A few were collected
from late June to late July, 1978, at the south transect, to a depth stratum
of 8.5 m at stations 1 to 15 m in depth. In 1979 and 1980, I7 emerald shiner
larvae were collected, providing more data for interpretation than the first 2

yr.

In 1979 emerald shiner larvae were taken from Pigeon Lake on ]k May,
somewhat earlier than in Lake Michigan. The earliest in the season an emerald
shiner larva was collected from Lake Michigan was on 3 June I98O at beach
station R (north discharge). The specimen was 5-2 mm, collected soon after
hatching. Newly hatched emerald shiner larvae were also collected 20 June
^979. 2 July 1980 and I8 August I98O at north transect stations 1 to 9 m in
depth. This indicates a spawning season from June to August, which is similar
*o that found by Fuchs (19^7) and Flittner (1964). The highest densities were
at beach station R (north discharge), up to 585 larvae/1000 m^. Older larvae
were collected from beach stations out to IS^m stations F and W, but at deeper
stations the larvae were found at the surface or in strata above the
thermocline. Slightly more larvae were collected at night than during the
day. Emerald shiner larvae were collected at water temperatures from 8.9 to
24.5 C. Since many were captured at water temperatures below 22 C, and such
cool temperatures are not conducive to spawning (Flittner 1964), larvae found
in Lake Michigan may have originated in Pigeon Lake or the discharge canal.

Young-of-the-Year —

Emerald shiners less than 50 mm in August through November were assumed
to be YOY from age-growth data presented by Fuchs (19^7) and Flittner (1964).
YOY emerald shiners were captured by seine in Lake Michigan in 1978 and 198O.
During the 4 yr, no YOY emerald shiners were taken in trawls or gill nets. In
1978 most were found at beach station Q (south discharge), while in I98O most
YOY were at beach station R (north discharge). Only one YOY was collected at
beach station P (south reference) during the 4 yr. YOY were found from August
to November in our study. August or September was the earliest that YOY
shiners were large enough to be susceptible to seining; the smallest emerald
shiner collected by seine was 28 mm.

Most YOY emerald shiners were captured at water temperatures from 6 to I9
C. Cooler temperatures at time of collection may reflect abundance and
schooling of young shiners during autumn months, rather than a temperature
preference.

272

In 1978 YOY emerald shiners were abundant in Pigeon Lake (Jude et
al. 1980), particularly at sandy beach station S (influenced by Lake
Michigan). Connecting inland waters may provide a suitable habitat for growth
of young emerald shiners.

Year 1 i ngs —

In Lake Erie* approximate minimum size at maturity is 5O-6O mm and most
emerald shiners spawn in their second summer (Flittner 196^). Therefore fish
larger than about 60 mm might be expected to spawn. However, in our study
many emerald shiners smaller than 80 mm showed no gonadal development. There
are two possible reasons for this: (1) emerald shiners deteriorate rapidly so
that gonads may not be easily seen; and (2) emerald shiners may take longer to
reach maturity in Lake Michigan than in Lake Erie. Evidence for slow growth
was provided by observations in April and May of numerous emerald shiners
20-44 mm in Pigeon Lake and in Little Pigeon Creek, 6 km north of the Campbell
Plant. Emerald shiners this size cannot be YOY so early in the season so they
were assumed to be yearlings. These yearlings overwinter at a smaller size
than emerald shiners studied in other areas (Fuchs 1967; Flittner 1964).

Few emerald shiners of any size were collected in the spring in Lake
Michigan during our study. Most yearlings may remain in connecting inland
waters during the spring. Three emerald shiners 63""64 mm collected in June
1978, one in April 1979 (50 mm) and one in April I98O (42 mm) were probably
yearlings. By August, when emerald shiners occurred more frequently in our
samples, yearlings would have attained sufficient growth to be
indistinguishable from 2- and 3" year-old fish.

Adults —

As was observed with YOY and yearlings, adult emerald shiners were
collected exclusively by seine during our study. They ranged from 70 to 104
mm in length. Few were found in our samples from April to July; they were
most abundant August and September and in I98O continued to be common in
October and November. Since fish larvae data indicate spawning was mostly
prior to August, the late summer-fall aggregations were not for the purpose of
spawning. Indeed, their gonads showed only slight to moderate development,
although those in poor condition or classified as immatures could have been
spent. In I98O, for example, only about 20% of the emerald shiners captured
in seines showed visible gonad development and most of those were only
slightly developed. Presumably, then, adult emerald shiners spawn in June and
July elsewhere than in Lake Michigan, probably Pigeon Lake or other inland
waters. Spawning grounds in our study area have not been discovered, although
high densities of larvae were noted at station S in Pigeon Lake (Jude et
al. 1979a). During the 4 yr, 23 females and 27 males were collected in Lake
Mi chi gan.

Emerald shiners usually spend summer months offshore, schooling near the
surface (Scott and Crossman 1973) • Thus they may not be susceptible to our
sampling gear at deeper stations (beyond 6 m) . Even if emerald shiners are

273

present offshore in the summer, they probably do not spawn there, since water
temperatures are cool and Flittner (1964) reports they spawn in 3-6 m of
water .

From 1977 to 1979, approximately as many emerald shiners were collected
at night as in the daytime. In I98O, however, almost three times as many
shiners were taken at night.

Emerald shiners were collected at water temperatures from 7-3 to 25-7 C.
Abundance seemed to be related more to season and habitat than temperature.

Plant Effects-
More emerald shiners were captured at beach stations R (north discharge)
and Q (south discharge) than at beach station P (south reference) during the
study. This is more likely due to the use of Pigeon Lake for a spawning and
nursery area than attraction of emerald shiners to the thermal plume.
However, it may be that emerald shiners are attracted to the warmer water as
wel 1 .

Ninespine Stickleback

Introduction —

The ninespine stickleback is widely distributed in fresh and salt waters,
and is common in the Great Lakes basin (Scott and Grossman 1973)* Jt is,
however, not as abundant in southeastern Lake Michigan as it is farther north

(Wells 1968; Griswold and Smith 1973). Its distribution in the more northerly
sections of Lake Michigan may be due to its preference for cooler, deeper
water (Wells I968; Nelson I968; Dryer I966) . Although ninespine sticklebacks
frequently nest in vegetation, they have also been observed spawning in areas
devoid of rooted aquatic plants. In such cases they may use bits of algae and
detritus to build nests (McKenzie and^ Keen ley side 1970). Spawning occurs from
April to August in Crooked Lake, Indiana (Nelson I968) , and in June and July
near the Apostle Islands, Lake Superior (Griswold and Smith 1973). Studies of
ninespine stickleback seasonal distribution show variation by study area;
however, in most areas ninespine sticklebacks overwinter in deep water

(Griswold and Smith 1973; Nelson I968) .

Ninespine sticklebacks spawn in two different habitats in the Campbell
Plant vicinity: Pigeon Lake (Jude et al. 1979a) and Lake Michigan,
demonstrating that spawning requirements were met in both environments. The
extent to which the inshore area of Lake Michigan near the Campbell Plant was
used for a spawning and nursery area is thought to be slight due to the
scarcity of larvae in our samples. Ninespine sticklebacks comprised between
0.1 and 0.5% of the total adult and juvenile catch during the k yr. In adult
sampling gear 133 were collected in 1977* ^1^ in 1978, 373 in 1979 and 236 in
1980. No trend in abundance could be detected.

274

Larvae —

Ninespine stickleback larvae were more frequently collected in 1980 than
in previous years, possibly due to utilization of Campbell Plant riprap for
spawning. Two unidentified sticklebacks taken in 1977 (Jude et al. 1978) are
now known to be ninespines, based on our increased expertise at identifying
larval sticklebacks. Abundance of ninespine stickleback larvae found in our
samples gradually increased during the study to 26 in I98O. The nest building
habit of adult sticklebacks as well as the protection of the eggs and larvae
by the adult male stickleback is probably in part the cause for generally low
densities of larval sticklebacks in our samples. Additionally, we feel that
the inshore area (beach to 15 m) of Lake Michigan near the plant is not used
extensively as a spawning and nursery area.

Ninespine stickleback larvae were most effectively collected by sled
tows. During the study 17 sled tows contained stickleback larvae, compared to
only 7 net tows. This probably reflects the demersal habit of larvae.
Densities ranged from I9 to 1^52 larvae/1000 m^ for sleds and from 9 to 370
larvae/ 1000 m^ for net tows.

Larval ninespine sticklebacks were collected from the beach zone (station
P, south reference) out to IS"*" stations F (south) and W (north). However,
shallow water appeared to be inhabited only by larger, older individuals
(7.5-20 mm). Small larvae soon after hatching (4.7-6.0 mm) were collected at
deeper stations (12-15 "») but were taken infrequently, probably because the
male keeps :he young in the nest for up to 2 wk (Scott and Grossman 1973) •
Older larvae were collected at a variety of depths. These data indicate
spawning in 12-15 nn (and deeper) water and subsequent dispersal of larvae.
Lengths of stickleback larvae in our samples ranged from k.J to 20.2 mm.

Ninespine stickleback larvae were collected from 1 July to 19 September,
most frequently in July. Sizes of larvae indicate probable spawning from late
June to late August. Water temperatures at time of collection ranged from 4.7
to 25.2 C, including temperatures over 20 C for newly hatched larvae.
Griswold and Smith (1972) found temperatures 11-12 C triggered spawning in the
laboratory; however, in our study the temperature at which sticklebacks
spawned could not be determined.

Young-of-the-yeai —

Length of ninespine sticklebacks after one growing season is
approximately kS mm in Lake Superior (Griswold and Smith 1973) and 35 nrnn i n
streams in Europe (Jones and Hynes 1950). Therefore, fish less than 35 nwn in
late summer and less than 45 mm in autumn were considered YOY. A few YOY were
collected each year of the study, 15 in all. They were captured in trawls
from July to November, mostly at south transect station F (15 m) and some at
stations N (9 m, north), D (9 m, south) and E (12 m, south).

275

Adults —

Ninespine sticklebacks may spawn after 1 yr of life (Jones and Hynes
1950). During our study yearlings could not be distinguished from older age-
groups by size or distribution. For these two reasons yearling ninespine
sticklebacks will be discussed together with adults.

Most ninespine sticklebacks were collected May through August, which
includes their spawning time. This species spends winter in deep water and
moves inshore to spawn (Griswold and Smith 1973) • >n our study, few were
collected in April (Fig. 87» Appendix 7) » probably because they were farther
offshore than our deep stations. By May an inshore movement had begun.
Catches at north transect stations L (6 m) and N (9 m) resembled those of
south transect stations C (6 m) and D (9 m) respectively.

in May ninespine sticklebacks were distributed uniformly among our
sampling stations (Fig. 87). Most sticklebacks in May showed only slight to
moderate gonad development (Fig. 88), although in May 1978 ripe-running
ninespine sticklebacks were collected in Pigeon Lake (Jude et al. 1979a) • In
June and July a large proportion of fish had well developed or ripe gonads.
Spent fish occurred mostly in July and August (Fig. 88). In June and July
ninespine sticklebacks were collected from the beach zone to 15 ni; however,
they were most numerous from 9 to I5 ^ (stations D, E, F and N) . This
observation correlates with collection of ninespine stickleback larvae at
12-15 m, indicating spawning in Lake Michigan's open water. During the k yr,
ninespine sticklebacks were most abundant at station E (12 m, south).

In all k yr ninespine sticklebacks apparently moved out of our study area
after spawning. The occurrence of ripe-running or spent fish was followed a
month later by their near disappearance from our samples. In 1977 abundance
dropped sharply after June; in 1978 and 1980 after August and in 1979.
ninespine stickleback abundance decreased after July (Appendixes 7f 27* 28 and
29). There was a tendency for ninespines to be more concentrated at deeper
stations from late summer through fall (Fig. 87). They were scarce at all of
our stations from September to December, 1977 to I98O. None were collected in
December at the south transect. However, two were taken at north transect
stations L (6 m) and N (9m) in December 1979 and I98O respectively.

Nearly all ninespine sticklebacks collected during our study were taken
by trawl, but a few (20) were collected by seine at beach stations. Their
preference for deep water and their small size makes them most susceptible to
capture by trawl. Ninespine sticklebacks collected by trawl and seine ranged
from 15 to Sk mm in total length, although fish from 1 5 to 44 mm were
considered to be immatures. Ninespine sticklebacks were more frequently
collected at night than during the day; 82% of all sticklebacks were taken in
night samples during the k yr.

Ninespine sticklebacks were collected at water temperatures from 1.0 to
22 C. The July 1979 upwelling, which depressed water temperatures below 5 C,
did not immediately decrease catches. It may, however, have depressed
spawning, since in the following month (August) sticklebacks were scarce and

276

80-

40-

F - 15 M

Q
UJ

H 80
O

O 40
O

X

en

E- 12 M

tr

UJ
CD

80

•

D - 9 M

40

-

,1 , , . ,

20

20-

C- 6 M

— I I =f=

B- 3 M

APR

MAY

NOV

DEC

JUN JUL AUG SEP OCT

SAMPLING PERIOD

Fig. 87. Total catches of ninespine sticklebacks by month for south
transect stations B (3 m) through F (15 m) near the J. H. Campbell Plant,
eastern Lake Michigan, 1978-1980. The 1977 data are not included
because sampling was not conducted in April and May.

277

80

40

a

NO

1977

NO

I

'WELL DEVELOPED AND
RIPE-RUNNiNG GONADS

□ 'SPENT GONADS

Ns70

I

N<5

— I —

o

UJ

o
o

X

80

40

80

U. 40
O

CC
CD

80

40

N«4

I

N*2

I

N*3

APR

1978

N*28

1979

N«92

1980

N»a7

I

MAY

N«II7

N*II9

N«76

I

JUN

N«9S

In

N«39

N«i06

N«0

I

NsiS

N<3

JUL

AUG

SAMPLING PERIOD

Fig. 38. Number of mature ninespine sticklebacks with well developed,
ripe-running and spent gonads collected monthly during June-December
1977 and April-December 1978-1980 near the J. H. Campbell Plant, eastern
Lake Michigan. N = total number of mature ninespine sticklebacks caught
per month.

278

had probably moved offshore as they do after spawning. Preferred temperatures
appear to be 6-14 C from our data. There was no apparent spatial separation
related to water temperature.

An unusual sex ratio was observed in our study. Females far outnumbered
males, 663 to l84. Since ninespine sticklebacks are small fish, the poor
condition of gonads may have resulted in some males with small gonads being
classified as immatures. However, if all immature and deteriorated fish are
added to the male category, the total is still only 372, which would still
result in a skewed sex ratio. This sex ratio may be related to the spawning
habits of the species. Males construct and guard nests, while up to seven
females may deposit eggs in a single nest (Scott and Grossman 1973).

During our study eight ninespine sticklebacks were found to be infected
by an acanthocephalan, probably Leptorhynchoides thecatus. Six of the fish
were females and two were males. They ranged from 65 to 74 mm in length.

Plant EffectS"

As previously stated, catches of ninespine sticklebacks at the north
transect were similar to catches at stations of equal depth at the south
transect. A minimal difference of two fish captured in December near the
plant while none were taken in December at the reference transect was
observed. It is unknown whether the intake structures themselves and
associated riprap will encourage additional spawning of ninespine sticklebacks
there in the future. However, any algal growths and trapped debris on the
riprap would supply additional nesting material. If the availability of
additional nesting material causes increased use of the area for spawning,
larval sticklebacks may become more common near the Campbell Plant.

Longnose Sucker

Introduction —

Longnose suckers were the twelfth-most common species captured in I98O;
166 individuals were taken, comprising 0.20% of the total catch (Table 10).
Of the k yr, longnose suckers appeared to be most abundant in the study area
in 1979, when 208 were captured (0.27% of the total catch). In I977 and I978
they were more scarce; only 36 and 73 were captured respectively (O.05 and
0.08% of the total catch) . These data imply an increase in abundance over the
last k yr. A slight increase in numbers of longnose suckers was also observed
in the vicinity of the D. C. Cook Plant between 1977 and I98O (unpublished
data. Great Lakes Research Division) .

Longnose suckers in Lake Michigan, like white suckers, usually spawn in
April in tributary streams (Becker 1976). Few catostomid larvae were captured
during this study, and white suckers were more abundant than longnose;
therefore longnose sucker larvae were probably not captured in Lake Michigan
during this study (see RESULTS AND DISCUSSION, White Sucker) .

279

Young-of-the-Year and Yearlings —

Age-growth data (Koehler 1978) for Lake Michigan near Ludington were used
to separate YOY (10 to approximately I50 mm) and yearling (150 to 264 mm)
longnose suckers from adults. Eleven YOY longnose suckers were captured from
1978 to 1980. They were caught from June through September in trawls and
seines from the beach to the 6-m contour. YOY ranged in size from 35 to Mk
mm. Three yearling longnose suckers, 155 to 17^ nim, were captured at the 6-m
contour in September and October 1978 to I98O. A probable yearling,
approximately 80 mm in May, was seined in 1978 at beach station Q (south
di scharge) .

Adults-
Adult longnose suckers were captured most effectively by bottom gill nets;
fish 225 to 624 mm were caught during the 4 yr. A few longnose suckers were
captured in trawls, seines and surface gill nets, but adult suckers can often
avoid trawls and seines, and their benthic habit prevents many from being
caught in surface gill nets.

Longnose suckers were generally scarce in April samples, due to spawning
migrations to streams. By the May sampling period, longnose suckers had
returned to Lake Michigan and in some years showed peak abundance during that
month. Many of these had spent gonads. In summer months, abundance of
longnose suckers fluctuated during the 4 yr. By late fall longnose suckers
moved offshore and few appeared in our samples.

Longnose suckers, like white suckers, were most abundant in our samples
collected near the 6-m contour. Exceptions to this distribution pattern
occurred during midsummer upwel lings of cooler water in 1977 and 1979- 'n
those years longnose suckers moved inshore with the cool (8-12 C) water and
were captured at the 1.5" and 3"ni contours. Longnose suckers were found at
water temperatures ranging from k to 2k C, and appeared to prefer temperatures
between 8 and 16 C. Night samples yielded larger numbers of longnose suckers
than day samples.

More male longnose suckers were collected during the study than females
{2kk males, 204 females). However, this difference was not consistent during
the 4 yr. Individuals with spent gonads were observed as early as April
(1980) and as late as July (1979).

Plant Effects—

Longnose suckers were more abundant at reference station C (6 m, south)
than at station L (6 m, north). Total bottom gill net catch from 1977 to 1980
at reference station C (6 m, south) was 104 longnose suckers, while at station
L (6 m, north) catch was only 24. This catch difference existed all 4 yr of
the study; possible reasons for lower catch at plant stations include
construction activity and presence of riprap at the plant structures. Fish
may also prefer south transect habitat over that available in the vicinity of
the plant. However, water temperatures at times of sampling were not

280

consistently warmer at the north transect (see RESULTS AND DISCUSSION,
White Sucker ) . Interestingly a similar relationship (more fish at the south
transect) was also documented for white suckers.

SI imy Sculpi n

I ntroduction —

The occurrence of slimy sculpins in the inshore zone of Lake Michigan
near Port Sheldon was highly correlated with water temperature. Our study
indicates that slimy sculpin were rarely caught at water temperatures
exceeding 10 C, and were most frequently caught at water temperatures of 7 C
or less. These results compare well with those of Rottiers (I965) who
indicated a preferred water temperature of 6 C for slimy sculpin and Wells
(1968) who reported that this species was most frequently caught at
temperatures of 4-5 C. Additional data from Wells (I968) suggest that even
during winter and spring months, the bulk of the slimy sculpin population
inhabits depths greater than I8 m, and thus our sampling effort collected only
from the fringes of the slimy sculpin populations of Lake Michigan. The major
occurrences of adult slimy sculpin in the inshore zone were during April, May,
December and periodically during summer months when cold-water upwel lings
occurred, which accommodated the thermal preference of this species.

The present importance of the slimy sculpin as forage for the salmonid
fishery in Lake Michigan is difficult to determine. Prior to the invasion of
the alewlfe. Van Oosten and Deason (1938) indicated that cottids comprised 72%
by volume of the food of lake trout in southern Lake Michigan. The most
dominant items in the stomachs of lake trout in the present study were smelt
and alewives (see RESULTS AND DISCUSSION, Lake Trout ) . Thus, it appears that
there is diminished importance of this species as forage since the invasion of
the smelt and alewife, at least in the inshore zone. Our observations do
confirm, however, at least some importance of sculpins in the diet of brown
and lake trout during spring months when these species both occur inshore.
Slimy sculpins in the area of Port Sheldon were reported to have an extremely
high infection rate of the acanthocephal an Leptorhynchoides thecatus
(Heufelder and Schneeberger I98O) ; however individual fish seemed unaffected
by their presence.

Larvae —

Effective sampling of larval sculpins is made difficult by the nesting
and protective behavior of the adults. Slimy sculpins have been observed
spawning on the undersides of objects at depths to 12 m in the study area.
When larvae hatch, they remain close to the protected nest area until
approximately the time of yolk absorption. Remaining close to a protected
area often affords protection from conventional sampling gear and explains the
absence of newly hatched larvae (6-6.5 mm) in our samples.

Occurrences of larval slimy sculpins in our samples over the 4-yr period
were sporadic and exhibited no evident trends. During I977 only three slimy
sculpin larvae (12-19 mm) were captured, all in late July. The occurrence of

281

slimy sculpin larvae in the S-S" and 15"ni strata of station H (21 m, south)
resulted in estimated larval sculpin densities of 13"20 larvae/1000 m^ and
suggested that larval sculpins may be less demersal than adults. No larval
slimy sculpins were captured in the study area during 1978. During 1979»
sculpin larvae (8.5 - l6.5 nf^ni) were sporadically present at various depth
strata of the 9" to 15-ni stations during both July sampling trips as well as
during early August (Jude et al. I98O) . There were no significant differences
in the densities of larval sculpins between transects (13"l67 larvae/1000 m^)
in 1979 and water temperatures at times of capture did not exceed 8.0 C.

Late June sampling during I98O indicated a large dispersed aggregate of
slimy sculpin larvae at the four surface-most strata of station (12 m,
north) (15-37 larvae/1000 m^) and the two surface-most strata of station N (9
m, north) (21-40 larvae/1000 m^) (Appendix 9). These larvae were small, 7-9
mm, and suggest that even larval sculpins with some remaining yolk may
occasionally migrate toward surface strata. The remaining sporadic
occurrences of slimy sculpin larvae in early July to late August I98O were all
recorded from sled tows at depths of 9 ni or greater and resulted in densities
of 29-240 larvae/1000 m^.

Over the 4-yr period the majority of sculpin larvae were caught at night.
This concurs with studies by Liston et al . (I98I) , near Ludington, Michigan
and suggests either increased daytime net avoidance or a movement to
protected, less accessible areas during the day.

Adults-
Si imy sculpins were most abundant in the inshore area during April and
May 1978-1980. Greatest abundance was at the deeper 12- and 15-m stations,
with progressive decline in abundance with shallower depths to 3 ni* Slimy
sculpins were rarely caught in the beach zone. Sculpins collected ranged in
size from I5 to 114 mm.

The occurrence of slimy sculpins in the inshore zone is probably related
to two factors, spawning instinct and water temperature. Gonad data for
April-June, I978-I98O indicate that spawning of slimy sculpins in the area of
Port Sheldon occurs in April or May (Fig. 89). The exact date of spawning is
probably temperature dependent. Slimy sculpins were reported to spawn at 5"10
C in New York (Koster 1936) and 8 C in the Montreal River (Van Vliet 1964).
Rottiers (I965) observed that in Lake Michigan spawning occurred prior to
early May in 1964, however, no water temperatures were given. A mass of slimy
sculpin eggs was taken from a log which was trawled at station E (12 m, south)
on 14 May 1979 at a water temperature of 11.2 C, however it is probable that
these eggs were actually spawned at a lower water temperature. Thus it
appears that the inshore zone is used by at least some sculpins as a spawning
area. It is probable that although the bulk of the sculpin population is at
greater depths during April and May, as indicated by Wells (I968) , the search
for suitable substrate on which to spawn causes some sculpins to disperse into
areas not normally inhabited. This dispersal into the inshore zone is allowed
by colder water temperatures in April and May of most years (generally below

282

10 C) . Slimy sculpins generally prefer water temperatures less than 10 C
(Rottiers 1965; Wells I968) . With the warming of inshore water in June, and
the continuance of this trend in July - August, slimy sculpins were rare in
the inshore zone. The exceptions to this trend were observed during times of
upwelling, and times when bottom water temperatures at the deeper inshore
stations were still within the temperature preferendum of the slimy sculpin.
At these times varying catches of slimy sculpins were observed. There was
also an occasional and sporadic occurrence of sculpins at inshore stations at
warmer (greater than 10 C) water temperatures. The majority of these slimy
sculpins caught at warmer water temperatures were smaller immature sculpins
which we feel have a higher tolerance for warmer water compared with adults
over 70 mm.

40

O

U

CO

^'20

1978
103

1979

■^WELL DEVELOPED
^^ AND RIPE-RUNNING
GONADS

□=SPENT GONADS

1980

APR MAY

JUN APR MAY JUN Af^R

SAMPLING PERIOD

JUN

Fig. 89* Number of mature slimy sculpins with well developed, ripe-running
and spent gonads collected monthly during Apr i 1 -December I978-I98O near the
J. H. Campbell Plant, eastern Lake Michigan.

The next major occurrence of slimy sculpins in the area of the Campbell

Plant was typically during December when water temperatures were again within

the temperature preferred by slimy sculpins. It is likely that throughout the

winter months some slimy sculpins persist in the inshore zone; however. Wells

(1968) suggests that the bulk of the population remains offshore.

Data from all years 1977"I980 showed that the majority of slimy sculpins
were caught at night. Although the reasons are unclear, aquarium as well as
diving observations indicate that sculpins exhibit a negative phototaxis, and
often seek areas of cover during daylight hours. Slimy sculpins can also bury
themselves in sand when no cover is provided.

283

Plant Effects--

Diving observations confirmed that the protective riprap area of the
intake and discharge structure has provided a considerable expanse of spawning
substrate for slimy sculpins. This increased spawning substrate in the area
of the Campbell Plant structures may be responsible for the increased
occurrences of sculpin larvae in 1979 and I98O field samples compared with
those taken prior to the placement of riprap in 1977 and 1978.

The increased spawning substrate provided near the intake structure as
well as the occasional migration of larval sculpins off the bottom is expected
to result in considerable entrainment of larval slimy sculpins during Unit 3
intake operation. The magnitude of the entrainment loss of slimy sculpin
larvae is difficult to predict and will depend largely on the extent of
continued use of the area by slimy sculpins as a spawning and nursery area.
There is some indication, based on diving operations, that fewer sculpins
utilized the area for spawning in I98O compared with 1979*

The maximum entrainment loss of larval sculpins is expected to occur from
June to July, based on a hatching time of late May - early June. Yolk-sac
larvae remain relatively near the nest and are subject to less entrainment
loss, so we expect the primary loss to be in larger larvae (larger than
approximately 7*5 mm). Eggs of sculpin should not be entrained to any great
degree since they are adhesive and laid in nests guarded by the mal'e sculpin.

Round Whitefish

Introduction —

The round whitefish is widely distributed in North America and into
northeastern Asia, primarily in deep lakes (Scott and Grossman 1973)- It
inhabits relatively shallow water, from surface to 25 m in Moosehead Lake,
Maine (Cooper and Fuller 19^5) and to about U5 m in the Great Lakes (Koelz
1929)- Like lake whitefish, round whitefish have decreased in abundance in
Lake Michigan since the early 1900s (Mraz 1964).

Round whitefish usually spawn in November in the Great Lakes region
(Scott and Crossman 1973)* Spawning habits are similar to those of lake
whitefish (Machniak 1975)- Spawning occurs in relatively shallow water, on
silt-free substrate.

Collections of round whitefish in the Campbell Plant vicinity have
increased during our study. In 1977» 8 were captured; in 1978, 10; in 1979.
Uk and in 1980, 115- Percentage of round whitefish in the total catch
likewise increased from 0.01% to 0.14% (Jude et al . 1978, 1979a, 1980).
Spawning evidently occurs in our study area; spent fish, and greater abundance
of round whitefish, have been observed in the fall.

Larval Coregoninae are difficult to identify to species. Possibly some
round whitefish larvae have been collected in our study. For a discussion of
this, see RESULTS AND DISCUSSION, Unidentified Coregoninae , Larvae.

284

Young-of ~the-Year and Yearlings —

Great variation exists in growth rates of round whitefish throughout its
range. Lake Michigan populations appear to grow faster than in other areas
(Mraz 1964). Age-growth data from the Ludington area (Armstrong et al . 1977)
and western Lake Michigan (Mraz 1964) were used to estimate age of our
specimens. YOY round whitefish were collected only in July and August I98O.
Ten fish 50-97 n»m were trawled from depths of 3 to I5 m. All but one were
from the south transect; however, this may be due to less trawling at the
north transect. Nearly all YOY round whitefish were collected at water
temperatures of 18-21 C, which was warmer than temperatures at which adults
were col lected.

Several fish 101-130 mm collected in fall may also have been YOY. These
were taken at stations 6-15 ni in depth, at the north and south transects, at
cooler water temperatures than those taken in summer (6.8-12 C) . There was no
clear separation between lengths of YOY and yearling fish. Round whitefish
138 to 173 nin™ collected in late fall 1977 and I98O may also have been
yearlings. These were trawled (one was gill netted) at north and south
transect stations 6-12 m in depth, most at water temperatures of 4-5.5 C.

Adults-
Round whitefish were collected from April to December during our study at
all stations where trawling or bottom gill netting was conducted. in April and
May they were found at a variety of depths. From June to August, however,
round whitefish appeared to prefer deeper waters, primarily 9 to 15 m. From
April to September round whitefish were not abundant; however, in October and
November abundance increased dramatically, particularly at depths of 3 to 9 m
(Appendix 6). During October and November, fish with well developed and spent
gonads were collected, indicating spawning occurred inshore. In December
mature round whitefish were nearly absent from our collections, apparently
moving from their spawning grounds to deeper water.

Round whitefish usually mature sexually at approximately 340-36O mm (Mraz
1964). Immature fish older than yearlings were generally distributed with
adults in our samples, except that they remained inshore in December, after
spawning ended. Several round whitefish 225 to 350 mm had slight gonad
development in the fall and probably would have spawned the following year.

More females (68) than males (46) were collected during our study. Sex
ratios are usually 50:50 for round whitefish (Armstrong et al. 1977;
Normandeau 1969)* Our resulting 60:40 ratio may simply be due to small sample
size.

Most round whitefish were collected by bottom gill net, and some by
trawl. Trawls were more effective in capturing small fish, especially YOY.
Total size range of round whitefish was 50 to 515 mm. Studies at Ludington
(Armstrong et al. 1977) and western Lake Michigan (Mraz 1964) yielded round

285

whitefish up to 528 mm and 515 ^^ respectively; however, researchers in New
Hampshire and Great Slave Lake seldom found round whitefish over ^50 mm
(Normandeau 1969; Rawson 1951) •

Round whitefish were collected at water temperatures from 1,0 to 20.8 C,
most between 5 and 14 C. At temperatures above 16 C only immatures (< 215 mm)
were found. Most round whitefish were collected during the night; however,
this trend was not as marked as for lake whitefish.

Round whitefish are benthic feeders, primarily consuming insect larvae
and small gastropods (Armstrong et al. 1977; Rawson 1951). Stomach contents
from round whitefish examined during our study included chironomid and
caddisfly larvae, gastropods, amphlpods and lake trout eggs. Round whitefish
are known to consume their own eggs (Normandeau I969) ; however, during our
study trout eggs were prevalent in stomachs. From size, coloration and season
these were judged to be lake trout eggs (Jude et al . I98O) . In 1979 a few
instances of egg predation occurred and in I98O eight round whitefish were
found with trout eggs in their stomachs, up to 50 eggs per individual.

During our study several round whitefish examined had parasitic copepods,
which were probably Salmincola edwardsi i (Hoffman 19^7) f attached to their
gill filaments. In I98O two fish (immatures I69 and 262 mm) were found to
harbor acanthocephalans.

Plant Effects—

In 1977 through 1979 the number of round whitefish collected were
approximately equal between north and south transects. However, in I98O,
especially in autumn, more were collected at north transect stations L (6 m,
south discharge), N (9 m, north) and U (6 m, north discharge) than reference
stations C (6 m, south) and D (9 m, south). Bottom gill net catches for these
stations were: C, 8; D, 8; L, 21; N, 13; and U, 10. The riprap laid down for
the new offshore intake and discharge serves as spawning habitat for lake
trout (Jude et al. 198lb) and round whitefish may be attracted to it for
various reasons, including food (lake trout eggs), cover and spawning habitat.

Gizzard Shad

I ntroduction —

Gizzard shad utilize, at least seasonally, all of the types of aquatic
habitat available near the Campbell Plant. Prior study of impingement samples
at Units 1 and 2 (Jude et al . 1979a) indicated the year-round presence of
gizzard shad in the discharge canal. The field catch of adult and juvenile
gizzard shad in Lake Michigan near the Campbell Plant was 17^ in 1977» I89 in
1978, 35 in 1979 and 111 in 1980, which accounted for less than 0.5% of the
catch by number in any year. It is difficult to assess the degree to which
gizzard shad utilize the area of the Campbell Plant as a spawning or rearing
area. Our estimates of larval gizzard shad abundance are probably low due to
the difficulty in distinguishing them from larval alewives at that point in
development from after yolk absorption to fin formation. Observations in the

286

Pigeon Lake-Pigeon River system as well as Lake Michigan and the discharge
canal lead us to believe that the primary site of shad reproduction is the
discharge canal itself. Larvae found in Lake Michigan near the plant probably
originated in the discharge canal or the Grand River.

Larvae —

The first occurrence of gizzard shad larvae in years 1979 and I98O
corresponds to our increased expertise in identifying them, rather than a
sudden appearance in these years. Gizzard shad larvae were sporadically
present from May or June to July in I979 and I98O. Densities of larval
gizzard shad at these times were low, not exceeding I50 larvae/1000 m^ at any
time. Field sampling of adults in Lake Michigan revealed no spawning activity
of adults in the area, so an inland source of larval gizzard shad was
implicated. Supplemental sampling in the discharge canal in May 1979 revealed
high densities of larval gizzard shad and strongly suggests that the discharge
canal was the source of larval shad sampled in Lake Michigan.

Young-of-the-Year, Yearlings and Adults —

YOY gizzard shad (up to 134 mm) over the if-yr period occurred
sporadically from August to December (Table 53). No distributional trends,
however, were evident.

Yearling and adult gizzard shad were present in the area primarily from
August to November, but occasional catches in all months except December were
observed. During the entire study period the majority of yearling and adult
gizzard shad were caught at depths of 6 m or less. Nearly all adult gizzard
shad collected exhibited only slight or moderate gonad development. Fish with
spent gonads occurred rarely during the study, appearing in July and August.
These observations provide further evidence for spawning in the canal, rather
than in Lake Michigan.

Gizzard shad were collected in all gear types utilized. Large gizzard
shad were collected primarily by gill nets, while trawls and seines accounted
for most smaller fish. Most were taken at night, at water temperatures
exceeding 10 C.

Plant Effects —

Due to the low abundance of gizzard shad near the Campbell Plant, it is
doubtful whether plant operation (Unit 3) will significantly affect their
population or that the discharge of Units 1 and 2 was affecting their Lake
Michigan distribution. Bodola (1966) has noted a tendency for shad to be
attracted to warm-water discharges even during winter months; however, we have
not seen any inordinate concentrations of gizzard shad near the Lake Michigan
discharge thus far.

We feel that the substantial production of shad larvae in the discharge
canal will undoubtedly continue in future years. Since warm water will be
discharged at 6 m, some gizzard shad larvae will be discharged into Lake

287

Table 53- Summary of gizzard shad catch by age-groups in the vicinity of the
J. H. Campbell Power Plant, eastern Lake Michigan, 1977"1980, Gizzard shad
were assigned to age-groups based on Bodola (1966). ND=no data.

Age-
Year Group Apr May Jun Jul Aug Sep Oct Nov Dec

1977

1978 YOY 16 10 32

1979

1980

YOY

NO

NO

year 1 ing

and adult

NO

NO

YOY

yearl ing

and adult

YOY

yearl ing

and adult

3

1

YOY

yearl ing

and adult

22

35

12

3

li*

15

1

91

16

10

65

42

5

18

2

10

1

2

11

1

28

21

23

6

k

if

Michigan at this contour. It is quite possible that under certain conditions
these gizzard shad larvae, which came from the discharge canal, could be
entrained by the 11-m depth intake structure at a later time or live and
complete their life cycle in Lake Michigan.

Chinook Salmon

Chinook salmon catches during our study have increased steadily from k in
1977 to 32 in 1978, 67 in 1979 and 99 in 1980. During the last 3 yr,
collections were dominated by recently smolted fish. Smolts comprised from 66
to 75% of the catch between 1978 and I98O. However, chinook spring
fingerlings stocked by the Michigan Department of Natural Resources have
decreased (from 700,192 in I978 to 500,200 in I98O) in counties immediate to
our sampling area (i.e., Ottawa, Allegan and Newago) , so our progressively
greater catches are not easily explained. It is possible that natural
reproduction by chinook near our study site has increased during the last few
years, since more fish with well developed and spent gonads were caught in
1979 and 1980 than in previous years. Mature males (18 total) have
consistently outnumbered mature females (9 total) in our samples.

In general, chinook were present in our sampling area from April through
November in water temperatures from 5 to 21 C. Jack salmon (200-^20 mm)
usually were gillnetted in spring, while smolts (70-120 mm) were seined in
beach zones mostly during June and July. Adult chinook migrate from deep

288

water to spawn and mature salmon (up to 1010 mm) were most commonly captured
in gill nets from September through November. Chinook were taken at all
sampling depths (beach-12 m) . Night catches surpassed day catches in earlier
sampling years, but diel catch differences were not observed in later years.
No consistent differences were noted between Chinook catches at north and
south transects.

Coho Salmon

During 1977"1980, 18 to 75 coho salmon were caught per year in the study
area. Coho salmon collected ranged from k] to 850 mm, most being small
individuals <200 mm (Appendixes 7. 27» 28 and 29)- Patriarche (I98O) reported
that 9-3% of coho salmon caught in Lake Michigan during 1979 were naturally
spawned. Coho salmon planted in the spring were 100-152 mm (M. Patriarche,
personal communication. Institute for Fisheries Research, Michigan Department
of Natural Resources, Ann Arbor, Mich.). Juvenile coho salmon 41-99 nrni, which
occurred in small numbers in the study area during 1977"1979f probably
originated from natural reproduction. In the spring of 1978 all coho salmon
planted by the four states bordering Lake Michigan were marked by fin clips.
Seven fin-clipped coho were caught in 1978 and six in 1979» Of these 13
marked fish, seven came from the Grand or Muskegon Rivers, two from Little
Manistee River, two from the St. Joseph River, one from the Platte River and
one from Indiana.

Coho salmon 41-190 mm occurred from May to October, with most being found
during May, June and July (Appendixes 7» 27f 28 and 29). Most of these
smaller coho salmon (9^^) occurred in night beach seines. These data agreed
with Tody and Tanner (I966) who reported young coho salmon remained close to
shore upon first entering the sea. Small coho salmon moved offshore during
summer; a few were caught in bottom gill nets at 6 and 9 ni during July, August
and September.

Larger coho salmon 240-820 mm migrate inshore during spring and fall.
Most were collected in night bottom gill nets. Approximately 25% of larger
coho salmon were caught during April and May; most were found during
September, October and November. A few larger coho salmon were also collected
during June and July 1978. A few coho salmon collected during fall were from
240 to 410 mm. Based on age-length data for coho salmon collected in Lake
Michigan during the fall (Patriarche 1980), these coho salmon were 2-yr old.
Most coho salmon collected during fall were adults (420-820 mm), several of
which showed well developed gonads. Coho salmon migrate upstream to spawn.
Jude et al. (198la) found adult coho salmon in Pigeon River during the
spawning season and suspected that some spawning could occur in this tributary
stream. Small coho salmon (41-190 mm) were found in relatively warm water
(11-21 C) . Most larger coho (300-820 mm) occurred in water temperatures of
5-13 C. These data agreed with Tody (1973) who reported coho salmon preferred
temperatures around 11.6 C. Several adult coho, however, were caught in water
temperatures of I8.5-23 C during September I978. During 1980, 50% of larger
coho salmon were found in water temperatures of 5"9 C and 50% in water
temperatures 15"17 C.

289

Catches of larger coho salmon (>200 mm) at north and south transects were
similar during the k-yr period. Smaller coho (<200 mm) were more common at
beach station Q or R (plant transect) than at beach station P (reference
transect) in 1978. During I98O more small coho were seined at the south
reference transect than at north transect stations Q or R. Reasons for these
catch differences are not known. Seine catches of small salmon at the two
transects were similar during 1979-

Lake Whitefish

I ntroduction —

The lake whitefish is widely distributed in the fresh waters of North
America, especially in large lakes and rivers. It is an important commercial
species. Populations in Lake Michigan have been reduced in recent years due
to environmental deterioration and depletion of stocks (Scott and Grossman
1973)* Lake whitefish tend to inhabit deep waters in the Great Lakes. Van
Oosten et al. (1946) found them most numerous at depths exceeding 25 m in
Lakes Huron and Michigan. Thus most lake whitefish in the Campbell Plant
vicinity have probably been outside the range of our sampling stations.

During our study there has been an increase in the number of lake
whitefish collected. In 1977 and 1978, 11 and 9 were captured respectively;
however, in 1979, 27 were collected, and 75 were taken in I98O. This trend
was not observed in studies at the D. C. Cook Plant, where lake whitefish
catch remained low from 1973 to 198O.

Lake whi tef ish usually inhabit shoal areas in spring, deep water in
summer, and return to the shallows in fall to spawn (Scott and Crossman 1973)*
They usually spawn in November through December at water temperatures between
0.5 and 10 C, over silt-free substrates such as rocks, gravel or sand
(Machniak 1975). In the Ludington area, whitefish spawn in October and
November on a rocky reef (Listen et al. I98I) . Larval Coregoninae are
difficult to identify to species. Some of the coregonine larvae collected
during our study may be lake whitefish (see RESULTS AND DISCUSSION,
Unidentified Coregoninae , Larvae) . They were taken so infrequently that the
Campbell Plant vicinity is probably not an important spawning area for lake
whitefish. No YOY lake whitefish were collected during our study.

Year 1 ings —

Great variation exists in growth rates of lake whi tef i sh in various
populations. In northern Lake Michigan Roelofs (1958) found age-1 lake
whitefish varied from IO8 to I7I rnm. Two areas in Lake Superior yielded age-1
fish 180 - 200 mm (Dryer I963) , and Lake Erie age-1 whitefish were I65-I8O mm
(calculated length) (Van Oosten and Hile 19^9). From these data, lake
whitefish less than about I70 mm TL at the beginning of the growing season
were assumed to be yearlings. Only a few were collected. In 1979 anci I98O
three yearlings were taken in April, July and November at stations 6 m and
deeper. All three were captured at relatively cold water temperatures,

4.7-5.5 C.

290

Adults-
Lake whitefish were collected from April to November during our study,
most frequently in summer months. In 1977 and 1979 ^3^ke whitefish were most
abundant in June and July. In 1978 their occurrence was scattered from April
to August, and in I98O they were most abundant in June, August and September
(Appendix 7) • Inshore-offshore movement was not traceable due to generally
low abundance of lake whitefish. Scarcity of whitefish during fall, and
complete absence of ripe-running or spent fish from study area collections,
indicate that lake whitefish spawn elsewhere. Few fish were collected that
had more than moderate gonad development. Somewhat more males (60) than
females (35) were collected. Lake whitefish sex ratios usually approximate
1:1; however, males and females do not appear at the spawning grounds
simultaneously, so uneven ratios are often observed (Machniak 1975)*

Only one lake whitefish was captured in less than 3 ni of water: in June
1980 a 222-mm fish, probably 2-yr old, was seined at beach station Q (south
discharge). Most lake whitefish were collected in bottom gill nets during our
study (85 fish), while 35 were trawled and 1 was taken in a surface gill net.
Station E (12 m, south) exhibited the highest catch and was the deepest gill
net station. However, trawl catches of lake whitefish at stations E and F (12
and 15 m, south) were similar, so peak abundance at station E may be a
function of our sampling scheme. As, in other studies (Van Oosten et al. 19^6;
Machniak 1975) t lake whitefish may be found offshore from the Campbell Plant
in deeper water.

Lake whitefish collected ranged from 142 to 700 mm TL. The majority of
these were >390 mm, by which length most lake whitefish are sexually mature
(Van Oosten 1939). Collection of lake whitefish occurred at water
temperatures from 3.3 to I9.3 C. Temperature preference from our data
appeared to be 7 to 15 C. Nearly all lake whitefish collected were taken at
night.

Lake whitefish are primarily bottom feeders, consuming benthic
macroinvertebrates and small fishes (Scott and Crossman 1973). Stomach
contents of whitefish we collected included chironomid larvae, amphipods and
gastropods. One lake whitefish 175 rnm TL was infected with an
acanthocepha 1 an .

Plant Effects —

During most of our study, catches of lake whitefish were too low to draw
any conclusions about plant effects. However, in August I98O, 23 whitefish
were taken in bottom gill nets at station N (9 m, north), while only 5 were
caught at station D (9 m, south). Water temperatures were similar: U.O C at
station D and I5.O C at station N. It is unlikely that lake whitefish would
be attracted to the thermal plume, since they were usually found at
temperatures below I5 C in our study, indicating a preference for cool water.
Since increased catch at the north transect occurred only once, it is probably

291

not an important plant effect. Also, lack of adult fish sampling at 12- and
15-m north transect stations prevents us from comparing whitefish abundance at
these preferred depths.

Brown Trout

Brown trout were first introduced to Lake Michigan in I883 (Brynildson et
al. 1973) • Natural reproduction, occurring both in the lake and in inflowing
streams, and subsequent plantings of several hundred thousand fish have
resulted in the firm establishment of this species in the Lake Michigan basin
(Becker 1976). Movements of brown trout can be fairly extensive. One year
after being planted in Lake Michigan, some specimens were found up to 323 kni
from the point at which they had been released, though most recovered fish
were found less than 2k km away (Becker 1976) .

Variable numbers of brown trout were collected during the course of our
study. Yearly catches were 49, 114, 88 and 50 fish respectively from 1977 to
1980. During all h yr, juvenile brown trout (106-200 mm) were caught
predominantly in the beach zone where warmest water temperatures existed.
Brown trout were captured at a wide range of water temperatures (3"21 C) , but
most fish were caught in water between 6 and 15 C. Larger fish (up to 707 mm)
were generally found in water less than or equal to 6 m.

Brown trout are largely piscivorous (Brynildson et al. 1973)- Stomach
content data from our study indicated that brown trout fed heavily upon slimy
sculpins and smelt during spring, and upon alewives during summer.

Although brown trout were generally present in our sampling area from
April through November, greatest numerical catches of trout occurred during
spring and fall. Fish probably move into sampling depths to feed during
spring, then move back out to cooler water in summer. Diel movements by brown
trout were also noted; more fish were caught at night than during the day.
Many brown trout captured during fall had well developed gonads. Brown trout
spawn in the fall when water temperatures are between 6.7 and 8.9 C (Scott and
Grossman 1973) •

Brown trout were more prevalent in south transect reference samples than
in north transect samples. Differences were due to deployment of gill nets at
1.5 and 3 m (where many brown trout were collected) in the south while these
contours were not sampled in the north. Gill nets were the most effective
gear for catching brown trout during all sampling years.

Rainbow Trout

Rainbow trout were first introduced into the Lake Michigan watershed in
1880 (Smiley I88I) and by I906 the population supported a commercial fishery
with fish averaging about 0.45 kg in weight (MacCrimmon and Gots 1972). The
next 20 yr would see a commercial fishery thriving on stocks thought to be
sustained primarily by natural recruitment of anadromous fish spawning
exclusively in Michigan streams. Coincident with the arrival in I936 of the
sea lamprey, numbers of rainbow trout declined and continued to do so through

292

the 1940s and 1950s, As efforts to control sea lamprey (initiated in 1948)
were intensified for Lake Michigan tributaries during the early 1960s, greater
numbers of rainbow trout were stocked. In I966 254,000 rainbows were planted
in Lake Michigan tributaries and by 1973 the total annual planting had risen
to over 3 million. Since 1973 annual plantings have ranged from I.3 to I.9
mill ion f i sh.

During I98O, 26 rainbow trout (270-840 mm) were collected in the vicinity
of the Campbell Plant (Appendix 7) as compared to previous catches of 29, 9
and 8 in 1979* 1978 and 1977 respectively (Jude et al. 198O, 1979a, 1978).
The substantial rise from I978 to 1979 might be attributable to an increase in
the number of rainbow plantings in Pigeon Lake from 5,038 in 1975 to 20,275 in
1976 and 10,000 in 1977 (Great Lakes Fish Commission I978, 1979, I98O) .
Stocked as 2- to 3-yr olds, these fish should have matured by age 5, and
returned to our study area within 3 yr (1978, 1979, I98O) . Two of the 26
rainbows collected in 1^80 were caught in the spring. One was captured in a
bottom gill net at station A (I.5 m, south), and the other was seined in May
at beach station P (south reference). The remaining 24 fish were caught with
increasing frequency from late summer to late fall. Most rainbows were found
at 6-m depths or less and all were gillnetted, with surface outnumbering
bottom net catches 44 to 10. Water temperatures at time of capture ranged
from 3 to 17 C. Over the 4-yr study period, 90% of the rainbow trout were
collected at night, indicating diel inshore and offshore movements.

During 1979 rainbow trout were most abundant in the spring when I7 fish
were collected in April. One rainbow was gillnetted in May and the remainder
were taken in October (five) and November (five) . Of the nine rainbow trout
captured in 1978, four were collected in the spring and five in the fall.
Sampling began in June 1977; consequently, all rainbows collected that year
were caught in the fall.

Populations of both spring- and f al 1 -spawn i ng rainbow trout have been
planted in Lake Michigan (Daly et al . 1975). Gonad data suggest that
individuals of both stocks have been encountered in our study area. Fifty
percent of the fall I98O catch was found to have well developed gonads;
whereas, spring spawners prevailed in 1979 (Jude et al . I98O) . Few rainbows
were collected in I978 and 1977; however, sexually mature individuals were
present in September and November samples.

Supplementary sampling and visual observation indicate that adult rainbow
trout were utilizing the discharge canal during winter I979 and spring I98O
(Jude et al. I98O) . Stomach analysis of these fish revealed an abundance of
gizzard shad and alewives, presumably consumed while in the canal. Seasonal
high densities of forage fishes near thermal discharges into Lake Michigan
(Romberg et al. 1974) could attract salmonid fish and may provide energetic
advantage to plume residents.

293

Golden Shiner

Golden shiners were collected from Lake Michigan only in I98O in our
study. They prefer weedy, quiet water with extensive shallow areas (Scott and
Grossman 1973). They are common in Pigeon Lake, particularly areas influenced
by the Pigeon River (Jude et al. 198la) . It is likely that those golden
shiners observed in Lake Michigan originated from Pigeon Lake. Seine hauls at
beach stations P (south reference) and Q (south discharge) in October 1980
yielded 15 golden shiners. Eleven of these were immatures from 37 to 53 ^^f
probably YOY. They were collected during the day and night at water
temperatures of 10.5-11.0 C. The four remaining shiners were 84-90 mm, all
adults. These four were collected during the day at beach stations P and Q
along with the YOY. Three were females with slight to moderate gonad
development and one was in such poor condition that sex could not be
determined. No golden shiner larvae were collected from Lake Michigan during
our study.

Common Carp

I ntroduction —

The common carp, a native of eastern Asia, was widely introduced in North
America in the late iSOOs. It has become abundant in many locations,
particularly where both shallow marsh habitat for spawning and deeper water
for overwintering are available (McCrimmon I968) . These requirements are met
in our study area. Pigeon Lake is bordered by several small marshes and
deeper water for overwintering is provided by both Pigeon Lake and Lake
Michigan.

Adult carp were occasionally collected during our study. In 1977f 7 were
captured; in 1978, 13; in 1979. 10; and in I98O, 14.
the total catch was about 0.01% in each of the k yr.
about 0.01% of the catch in studies at the D. C. Cook
al . 1979b). Carp are common in warm waters (Becker
abundant in inland waters than in Lake Michigan.

Percentage of carp in

Carp also comprised

Nuclear Plant (Jude et

1976) and are more

Larval carp were collected more frequently than would be expected from the
occurrence of adults. Spring spawning presumably occurs inland, not in Lake
Michigan, due to cold water temperatures. However, spawning has occurred
regularly in Lake Michigan at the Cook Plant after startup of Unit T,
presumably due to the warm-water discharge (Jude et al. 1979b). Swee and
McCrimmon (I966) reported that spawning did not occur below I7 C in Lake
St. Lawrence, and optimum spawning temperatures were between I9 and 23 C.
Water temperatures above 19 C did not occur in Lake Michigan until at least
early July in our study, yet carp larvae were collected in May 1979 and in
mid-June I98O. Later spawning may occur in Lake Michigan, but preferred
spawning habitat is not present; therefore lake spawning is probably less
successful .

294

Populations of carp exist in Pigeon Lake and the intake and discharge
canals of the Campbell Plant (Jude et al, 1979a)' The warm water of the
discharge canal is conducive to early spawning, although little vegetation was
present even before construction of Unit 3 began. Carp larvae captured early
in the year in Lake Michigan may have been produced by the discharge canal
population. Reproductive contributions of carp populations in Pigeon Lake and
the intake and discharge canals occur at different times, explaining the
capture of larvae at widely separated times throughout the year.

Larvae —

First occurrence of carp larvae in Lake Michigan was in mid-May to June
during the study. These larvae were thought to be from intake or discharge
canal spawning in 1979 and I98O, while in I978 they probably originated from
Pigeon Lake. These conclusions are based on samples in the intake canal,
Pigeon Lake and entrainment samples from Units 1 and 2. Densities of larval
carp collected in Lake Michigan in May and June were somewhat higher at the
north plant transect compared with the south transect. For example, in May
1979 carp larvae were collected at north transect stations Q (beach, south
discharge), I (1.5 m, north), J (3 m, north), L (6 m, north) and (12 m,
north), with estimated densities of 15 to 195 larvae/1000 m^. At the south
reference transect carp larvae were captured only at stations P (beach, south
reference) and B (3 m, south) with estimated densities of 21 and 63
larvae/1000 m^ respectively (Fig. 90). These differences are evidence for
intake or discharge canal spawning. Similarly, Waybrant and Shauver (1979)
found much higher densities of carp larvae in backwater or vegetated areas
compared with open waters of Lake Erie. Carp larvae in their study area were
captured relatively close to the mouth of the Huron River, which was probably
the source of carp larvae rather than Lake Erie.

In the k yr of the study, carp larvae were always collected during July
except in 1979* August and September catches included some larval carp in
1979 and 1980 respectively (Fig. 90). The discontinuous, apparently sporadic
occurrence of carp larvae can be attributed to spawning of separate
populations.

Carp larvae were collected at water temperatures from 9*5 to 24.2 C.
Although larval carp were captured from the beach to 15~ni stations, they were
more abundant inshore (Fig. 90) and remained above the thermocline when in
deeper water (never deeper than the 8.5"^" stratum). Densities of carp larvae
in Lake Michigan during the study ranged from 15 to 591 larvae/1000 m^, with
greatest densities occurring at beach stations and the 1.5-ni contour. These
values compare with densities of 1 to 103 larvae/ 1000 m^ obtained by Cole
(1978) from Lake Erie.

Carp larvae collected during our study were mostly between k.O and 7-0 mm
TL and were recently hatched. The largest carp larva, 10.5 n^ni, was taken 28
July 1977 at station I (I.5 rn, north) at a water temperature of 11.8 C.
Larger larvae were captured infrequently, perhaps due to mortality or net

295

^^ iO>^' iNi^*^ iNi'^' ^Ni^*^ >.^^ S^^

SAMPLING PERIOD

Fig. 90- Mean density (no./lOOO mO of larval carp for north and south
transect stations in Lake Michigan near the J. H. Campbell Plant, 1977 to
1980, Mean densities were calculated by averaging densities over all gear
(plankton nets and sleds), strata and diel periods (day and night).

avoidance, so a pattern
detected. Carp larvae
pattern was apparent.

of length distribution with depth could not be
were captured in both day and night samples; no diel

No YOY or yearling carp were collected in Lake Michigan during our study.
Absence of age-groups of carp between larvae and adult suggests that Lake
Michigan near the Campbell Plant does not serve as a favorable nursery area.
Absence of YOY at any time during the study further suggests that those larvae
spawned in Lake Michigan or those which drifted from inland sources, do not
survive. It is likely, therefore, that adult carp captured in Lake Michigan
near the Campbell Plant were spawned and reared in inland waters connected to
Lake Michigan, which are more conducive to spawning and successful rearing of
carp. Some of these carp then disperse from their rearing areas into Lake
Michigan as adults. The nearest successful rearing area to the Campbell Plant
is Pigeon Lake as indicated by observations of YOY there in 1977 and 1978
(Jude et al. 1979a). In Lake St. Lawrence, YOY carp were found in shallow
marshes until at least mid-autumn (Swee and McCrimmon I966) .

Adults-
Seasonal distribution of adult carp in Lake Michigan near the Campbell
Plant showed no obvious trends. A slight movement offshore from spring to
fall was suggested, since in April carp were collected only from beach
stations to 6 m, while in late summer and fall carp were sometimes collected
at stations E (12 m, south) or F (15 m, south). Throughout the year, however,
carp were most frequently found nearshore (to 6m). In 1978 peak catch of

296

carp occurred in August; however, in other years the catch of adult carp
remained relatively constant from April to October or November. None were
collected in December of any year.

Adult carp in our samples ranged in length from 515 to 78O mm. They were
most effectively sampled by bottom gill net (29 fish); however, some carp were
also collected by seine (10 fish) and trawl (5 fish). More carp were found in
night samples than day samples. Carp were collected at water temperatures
from 3*9 to 2k C, but the greatest catch occurred at temperatures from 8 to 17
C.

Carp with well developed gonads were observed from April to November in
the study area; however, the only ripe-running fish was a male in July I98O.
Occurrence of carp with well developed gonads from spring to fall may be due
to repeated spawning by individuals, or spawning at widely differing times.
In the vicinity of the D. C. Cook Nuclear Plant, carp with well developed or
ripe gonads were observed May through July (Jude et al. 1979b). During our
study somewhat more females {2k) than males (20) were collected.

Plant Effects—

From 1977 to 1979 adult carp showed no particular trend in catch
difference between reference and plant transects. In I98O, however, catch of
carp (five fish) was greatest at station N (9 m, north); two were the most
collected at any other single station. Temperature preferences of carp are
known to be above 25 C (Reutter and Herdendorf 197M . Pitt et al. (1956)
found final preferred temperature to be 32 C for YOY carp. Carp may therefore
be attracted to the vicinity of the thermal plume emitted by the Campbell
Plant. However, so few adult carp were caught that their attraction to the
warm-water plume cannot be confirmed at this site.

In the vicinity of the D. C. Cook Plant near Bridgman, Michigan,
occurrence of carp larvae at plant transect stations indicated carp spawning
in the thermal plume (Jude et al . 1979b). This may occur at the Campbell
Plant as well, although spawning in the intake and discharge canal is thought
to be more important. The Wilcoxon signed ranks test showed that for 27 cases
during the k yr, there was a tendency for carp larvae to be more abundant at
the north transect than at the south reference transect (significant at a «
0.05) .

The Campbell Plant has provided favorable habitat for carp spawning in the
intake and discharge canals. More sheltered and warmer than Lake Michigan,
the canals provide optimal water temperature, food and habitat for early
spawning. Larvae produced there may survive and contribute to carp
populations in Pigeon Lake and Lake Michigan.

Si Iver Redhorse

The silver redhorse is uncommon in the Lake Michigan basin, and primarily
inhabits moderate to large rivers and reservoirs (Becker 1976). Like other
redhorses, it was collected infrequently in the Campbell Plant vicinity.

297

Twelve were captured in 1977; ^ in 1978; 3 in 1979; and 14 in 1980, One
juvenile (57 nrm) and three adults were caught in a July, 1977 night seine haul
at beach station R (north discharge). All other silver redhorses collected
were adults taken in bottom gill nets. Water temperatures at time of
collection ranged from 8 to 2k C; most fish were caught at 12 to 20 C. Adult
fish ranged in length from 3^5 to 595 n^m.

Silver redhorses were captured from June to November from the 1- to 6-m
depth contours. Most were collected in late summer through fall. More were
collected at night than in daylight. No trends between reference and plant
transects were apparent.

Eighteen male and 13 female silver redhorses were collected. Well
developed gonads were observed from July through September; no ripe-running or
spent fish were captured, so spawning time is unknown for our study area.

Channel Catfish

Although the catch of channel catfish in any year did not exceed 10 fish,
our data indicate that during August and September channel catfish exhibit a
migration to some extent into Lake Michigan, possibly from large river
systems. With the exceotion of one channel catfish caught in April I98O, all
occurrences of channel catfish in Lake Michigan samples were observed from
August to October. Since channel catfish are not common in Pigeon Lake, it is
possible that those individuals caught in Lake Michigan originated from Lake
Macatawa (I5 km south of the plant) or the Grand River (17 km north of the
plant). While it is possible that the intake and discharge riprap may be an
attractive influence for channel catfish as was suggested to occur at the Cook
Nuclear Power Plant (Jude et al . 1979b), it is doubtful that plant operation
will cause any impact on channel catfish populations in adjacent areas.

One YOY channel catfish (60-mm length interval) was trawled at station D
(9 nfi, south) in December 1979* The remaining channel catfish collected were
mature adults, 285-73^ nwn in length, including I8 males and 7 females. All
had slightly or moderately developed gonads, another indication that they do
not spawn in Lake Michigan in our study area. Adults were taken in bottom or
surface gill nets, mostly at depths of 6 m or less. Channel catfish appeared
to prefer warm (>15 C) water temperatures. Most were collected at night.

Shorthead Redhorse

The shorthead redhorse occupies a wider range of habitats than other
species of Moxostoma , being present in lakes and in moderate to large streams
(Becker 1976)* Shorthead redhorses are uncommon in the vicinity of the
Campbell Plant; from 1977 to I98O, only I3 adults were collected. No larvae,
YOY or yearlings were observed during the study. In I98O seven were captured,
which was more than in any previous year. During the study all redhorses were
taken in bottom gill nets, mostly at night. Water temperatures at time of
capture ranged fror 10 to 21 C. Fish collected were between 3^0 and 700 mm in
length.

298

Shorthead redhorses were collected from June to October, most frequently
at station A (1 .5 m, south), but a few were caught at 6- and 9-m stations.
There were no apparent differences in catch between reference and plant
transects.

More females (eight) than males (four) were collected during the k yr .
Most had slight to moderate gonad development; individuals with well developed
gonads were observed twice, in August and October. One spent female was
collected in June 1979f indicating spawning during spring.

Burbot

I ntroduct ion —

The burbot is widely di
waters of lakes and large, cool
18.3 C and spawns in midwinter,
Grossman 1973). At the Campbell
because they inhabit deep water
spawn in winter, when sampling i
burbot larvae have been col lee
been observed in Pigeon Lake in
appeared in Pigeon Lake and
Therefore, Pigeon Lake, in add it
site for burbot.

stributed in North America and Eurasia in deep
rivers. It prefers water temperatures I5.6 to
under the ice, in shallow water (Scott and

Plant adult burbot are infrequently collected
during our sampling season and move inshore to
s not conducted. Because of inshore spawning,
ted more often than adults. Adult burbot have
December and February, and larval burbot have

in entrainment samples from Units 1 and 2.
ion to Lake Michigan, is a likely spawning

Larvae —

Burbot larvae first appeared in Unit 1 and 2 entrainment samples on 11
April 1978. Field larvae samples from Lake Michigan usually contained burbot
larvae from mid-April to mid-June. Many newly hatched (3.6 to 5.O mm) larvae
occurred in samples from April through June.

Seasonal distribution varied from year to year. In I977 no burbot larvae
were collected, probably because sampling commenced in June. In I978 burbot
larvae were most abundant in April at the north transect, particularly at
beach stations R and Q. Estimated densities in the nearshore zone ranged up
to 56A larvae/ 1000 m*. High densities at beach stations indicated spawning
may have taken place there.

In 1979 no larval burbot were collected in April, but some were taken in
May and more in June. Unlike other years, burbot larvae occurred at mid-
depths and not at beach stations. Estimated densities were low, I6 to 48
larvae/1000 m^. Perhaps hatching occurred after our April sampling and larvae
had begun to disperse by May.

In 1980 burbot larvae were most abundant during May at beach stations R
(north discharge) and P (south reference), at densities as high as 843
larvae/1000 m^. Larvae were less abundant in deeper water, but they were
found from 1 to I5 m at the north transect and 1 to 12 m at the south
transect, which was similar to the April I978 distribution. Our data suggest

299

spawning near the beach and subsequent dispersal of larvae to deeper waters.

Larger larvae (to 7-5 nini) were generally found in 6-15 m of water; this was

the only trend in distribution by size. A later peak of abundance in I98O
than 1978 suggests later hatching.

Burbot larvae usually were slightly more abundant at or near the bottom
than in surface tows. More larvae were found in night samples than day
samples, particularly larger larvae, to 7-5 'nm. Burbot larvae were collected
at water temperatures from 4.5 to I6.O C, however, most newly hatched larvae
were taken at cooler temperatures, from 4.5 to 10 C.

Young-of-the-Year and Yearlings —

Burbot undergo rapid growth, especially in their first year (Muth 1973;
Scott and Grossman 1973) • Three immature burbot 95""144 mm trawled in late
summer and fall 1978 were probably YOY. All were collected at station E (12
m, south); water temperatures were 10 to ]k C. One male burbot with slightly
developed gonads was trawled in October 1978 from station C (6 m, south); it
was in the l60-mm length interval and was probably a yearling. All four of
these fish were collected at night.

Adults-
Few adult burbot were collected during our study, due to their preference
for deep water. In December 1977 a female with well developed gonads was
trawled at station D (9 m, south). No mature burbot were collected in 1978 or
1979* Five burbot, all females, were collected In 198O by bottom gill net and
trawl at stations 3 to 9 ti in depth. One, collected in April, was spent; the
others, taken during October and November, exhibited moderately to well
developed gonads. Most adult burbot were collected at night. Water
temperatures at time of capture were 1 to 12 C. The six fish ranged from 3^9
to 618 mm. Stomach contents of several burbot examined included alewives,
rainbow smelt, gizzard shad and sculpins.

Plant Effects—

Al though in 1978 burbot larvae were more abundant at the north transect
than the reference transect, a Wilcoxon signed ranks test showed this was not
statistically significant at a « O.O5. Larvae were evenly distributed between
transects in 1979 and I98O. Adult burbot exhibited no particular difference
in abundance by transect. Preliminary SCUBA observations did indicate that
burbot were attracted to the intake and discharge areas, presumably due to the
increased cover afforded by the riprap.

Mottled Sculpin

During preoperational years 1977"'1980, the mottled sculpin only
occasionally occurred in Lake Michigan near the Campbell Plant. Only four
mottled sculpins were caught during 1977* while one was caught in 1979 and
five were taken in I98O. Mottled sculpins were not collected in Lake Michigan
near the Campbell Plant in I978.

300

Mottled sculpins were collected only by trawling, mostly at night, during
our study. They were taken at stations 9 ni or deeper, at water temperatures
from k to 1^ C. Sculpins ranged in size from 25 to 9^ fnm; adults had only
slight gonad development.

While the typical habitat of mottled sculpin does not include the open
water area of Lake Michigan, construction of artificial reefs in the inshore
zone has often resulted in the establishment of local populations there,
similar to what occurred at the D.C. Cook Plant (Jude et al. 1979b). It is
likely that a similar situation will develop at the Campbell Plant structures
as mottled sculpins from adjacent Pigeon River occasionally disperse into Lake
Michigan, take refuge in and colonize the riprap area. Mottled sculpins will
probably remain in the intake area throughout the summer months when slimy
sculpins exhibit an offshore distribution (see RESULTS AND DISCUSSION,
SI imy Sculpi n ) , and may gain importance as forage for some of the warm-water
species of fish (i.e., yellow perch).

Golden Redhorse

The golden redhorse usually inhabits streams (Becker 197^); it was
uncommon in the Campbell Plant vicinity during our study. In our 1977
sampling none were captured in Lake Michigan; in 1978, k; in I979t 10; and in
1980, 4. No golden redhorse larvae, YOY or yearlings were collected. All
fish collected in Lake Michigan were caught in bottom gill nets at water
temperatures from 8 to 22 C. Lengths ranged from 400 to 636 mm.

Golden redhorses were caught during June to October from the 1.5" to 6-m
depths, somewhat more frequently at shallower depths. Unlike other suckers,
golden redhorses were not collected in greater numbers at night than in
daylight. No trends in catches between reference and north transects were
apparent.

Ten male and eight female golden redhorses were collected; most had slight
to moderate gonad development. In July 1979 three fish with spent gonads and
two females with reabsorbing eggs were caught, which indicates some spawning
occurred before 17 July.

Longnose Dace

Longnose dace are found in swiftly flowing streams, lakes and inshore
waters of the Great Lakes (Scott and Crossman 1973)- Although they are widely
distributed, they are uncommon in our study area. Apparently the beach zone
near Ludington, north of the Campbell Plant, provides more favorable habitat
as Anderson and Brazo (1978) seined dace in sizable numbers during 1975-

Three dace were collected in 1977 and three in I98O during our study.
Their benthic habit should make them susceptible to trawling, but only one was
captured in our trawls, probably because of their preference for the beach
zone. No longnose dace larvae were collected. Two fish 45-5^ mm seined in
November 1977 at beach stations P (south reference) and Q (south discharge)
were probably YOY. A 49-mm longnose dace seined in July I98O at station Q was

301

probably a yearling; it had undeveloped gonads. Two adult longnose dace,
55""105 nim, were seined in October 1977 and July I98O respectively, at beach
station P. One was a spent female and one a male with slight gonad
development. The only fish captured by trawl was 82 mm, taken in July 1980 at
station C (6 m, south). Longnose dace were collected at water temperatures
from 10 to 21.5 C. Most were captured at night. It is unlikely that plant
operation will affect this species, since it is uncommon in the Campbell Plant
vici ni ty .

Wal leye

Walleyes are planted in the Muskegon River system (47 km north of the
Campbell Plant) and in Lake Macatawa (19 km south of the Campbell Plant).
Walleyes also spawn naturally in eastern Lake Michigan (R. Lincoln, personal
communication, Mich. Dept. Nat. Res., Grand Rapids, Mich.). However, walleyes
are uncommon in Lake Michigan in the vicinity of the J. H. Campbell Plant.

No walleyes were observed in Lake Michigan field samples in either 1977
or 1979* In 1978, seven YOY walleyes were collected, six in beach seines in
August when water temperature was between 22 and 25*7 C and one in a trawl
haul at 6 m in December when water temperature was 1.0 C. Whether these fish
migrated from their planting site or originated from natural reproduction is
not known.

Three walleyes between 415 and kkk mm were gill netted in fall I98O at
water temperatures between 9 and 11 C. All three fish were males with
moderate to well developed gonads. These fish were all caught from the north
transect and may have been attracted to the riprap in the area. Becker (I976)
reports that walleyes prefer clear water with gravel, rock, sand or hard-clay
bottoms. It is possible that greater numbers of walleyes will concentrate
around the Campbell riprap in future years, since several species which serve
as forage fish for walleye (e.g., alewife, trout-perch, rainbow smelt and
yellow perch) may also concentrate near the riprap.

Central Mudminnow

The central mudminnow inhabits small creeks and isolated ponds (Scott and
Crossman 1973) • its presence has been noted in small creek tributaries of the
Pigeon River within about 12 km of the J. H. Campbell Plant (Jude et
al. 1981a), and one specimen was caught in Pigeon Lake in May 1978 (Jude et
al . 1979a). The collection of an immature mudminnow and a male with well
developed gonads in Lake Michigan (12 m, south) in May I98O was therefore
considered unusual.

Several mudminnows (many with ripe-running or well developed gonads) have
been collected from traveling screens at the D. C. Cook Plant, southeastern
Lake Michigan, always during spring (Jude et al. 1979b)* Central mudminnows
spawn in mid- to late April (Scott and Crossman 1973) so their presence in
Lake Michigan may be related to spawning behavior.

302

Ye] low Bullhead

Only two yellow bullheads were caught in Lake Michigan during the entire
study period. They were collected at stations B (3 m, south) and L (6 m,
north). Both fell in the l80-mm length interval. Their occurrence in July
1980 suggests that they only rarely enter Lake Michigan, and thus have little
ecological importance in this system.

Qui 1 Iback

Populations of quillbacks inhabit the Grand and Macatawa rivers (Becker
1976); from these sites north and south of the Campbell Plant this species may
spread to the plant vicinity. Quillbacks were observed in our Lake Michigan
samples in 1978 (two) and I98O (four). An 8.2-mm qui 1 Iback larva was
collected at night on 27 f<pr\]f 1978 at beach station Q (south discharge).
The calculated density was 282 qui 1 Iback larvae/1000 m^. This larva may have
originated from spawning in the discharge canal, since quillbacks have been
observed there.

Adult quillbacks were occasionally caught during our studies from June to
October and during studies at the D. C. Cook Plant (Jude et al. 1979b). They
were collected most frequently in bottom gill nets at 1 .5- and ^-m depth
contours in both studies. One individual at the Campbell Plant was captured
in a seine haul in June, 1978 at beach station Q (south discharge). All
quillbacks were collected at night when water temperatures were 10 to 2k C.
These fish ranged in size from 415 to 50^ nfwn and included two males and four
females. None had ripe-running or spent gonads. There were no apparent
differences in catch between reference and plant transects.

Deepwater Sculpin

Introduction —

Prior to I98O, some confusion over the taxonomy of fourhorn/deepwater
sculpins existed. Recent changes have been made, such that fourhorn sculpins
( Myoxocephalus quadr icorni s ) previously reported from the Great Lakes region
were probably deepwater sculpins ( Myoxocephalus thompsoni - Robins et
al. 1980). Deepwater sculpins inhabit deep lakes of North America. Not much
is known concerning the biology of this species because it is seldom found
inshore (Scott and Grossman 1973) • Jacoby (1953) determined deepwater
sculpins in Lake Superior to be most abundant from 100 to 240 m; larger fish
tended to inhabit deeper water. in Lake Michigan deepwater sculpins were
distributed from approximately 50 to 200 m (Deason 1939)- Previous studies
have indicated spawning occurs in summer or early fall (Scott and Grossman
1973)* For the closely related fourhorn sculpin ( Myoxocephalus quadr icorni s ) .
males guard nests until hatching; development took 55 to 100 days in the
laboratory at temperatures below 5 C (Westin 1969)* Larval sculpins from the
Campbell Plant vicinity which were identified as fourhorn sculpins in 1978 and
1979* and reported in previous Special Reports, are now designated deepwater
sculpin larvae because of this recent taxonomic change.

303

Larvae —

Deepwater sculpin larvae (9"10 mm) were first collected in early February
entrainment samples. Eggs producing these larvae were probably spawned the
previous November or December. Deepwater sculpin larvae were most abundant in
field samples taken during April and May, occasionally appearing until mid-
August. Estimated densities were low, 11 to 71 larvae/1000 m^. Larvae as
small as 9*5 nrmi were taken in July, indicating a prolonged spawning period or
slow growth. Deepwater sculpin larvae were collected at water temperatures
from 2.3 to 10.2 C, most below 8.0 C. Cool water temperatures and small
maximum size of adults imply slow growth of larvae; thus it is difficult to
infer spawning time from presence of larvae. In Lake Superior deepwater
sculpins are believed to spawn from November to mid-May (J. H. Selgeby,
personal communication, U. S. Fish and Wildlife Service, Ashland, Wise).
Near Ludington deepwater sculpin larvae were present in collections from 17
April to August; however, highest densities were in April and May. Larvae
collected during the summer were larger (13"22 mm) and occurred during
upwel lings of cooler water (Liston et al . I98I) . These data in addition to
our studies indicate spawning from early winter possibly to early spring in
eastern Lake Michigan.

Deepwater sculpin larvae were collected at stations from 6 to I8 m in
depth and at depth strata of 2.5 to 17 m. Larvae tended to be in the lower
part of the water calumn. Although there was no month-by-month trend in
abundance at various stations, absence of deepwater sculpin larvae during late
summer and fall is probably due to offshore movement of YOY from our study
area. Further evidence for this is the virtual absence from our trawl samples
of YOY, yearling or adult deepwater sculpins.

Larval deepwater sculpins 9*0 to I8.3 mm were collected in field samples.
Somewhat more larvae occurred in night samples than day samples.

Supplemental sampling in May 1981 at 80 and 100 m by M. Evans (Great
Lakes Research Division) yielded a few deepwater sculpin larvae less than 10
mm. This indicates probable spawning offshore in addition to possible
spawning at 6 to 15 m^ Liston et al • (I98I) found abundance of deepwater
sculpin larvae increased with depth, to a sampling limit of 12.1 m. Larval
deepwater sculpins occurring in our sampling area were most likely carried
inshore by currents. Their pelagic existence as larvae makes them vulnerable
to surface water movements. Also, adults are common in deep water (as shown
by supplemental trawling at 80 and 100 m) , but virtually absent from inshore
waters. These two factors suggest offshore spawning and subsequent dispersal
of pelagic larvae. Higher densities of sculpin larvae than those we found
would probably result if significant spawning occurred inshore.

Yearlings and Adults —

A 22-mm deepwater sculpin was trawled at station N (9 m, north) in May
1980. This fish was somewhat larger than most larvae captured in May,
suggesting it was spawned the previous summer. A 90-mm female with moderate

304

gonad development was trawled at station E (12 m, south) also in May I98O.
Both fish were collected at night, at water temperatures 6.0 to 6.1 C. These
were the only deepwater sculpins other than larvae collected during our study.

Supplemental trawling in May 1981 by M. Evans at 80 and 100 m captured
several adult deepwater sculpins 111 to 143 mm in length. As was found by
previous studies, deepwater sculpins prefer deeper water than we normally
sample. Thus, deepwater sculpins are not subject to much impact by power
plants except by occasional entrainment of larvae. Even larvae ranging
inshore did not exhibit a difference in abundance between transects.

Black Crappie

Common residents of adjacent Pigeon Lake, adult black crappies rarely
disperse into Lake Michigan near the Campbell Plant. In the k-yr period,
1977"1980, only one adult black crappie was caught; it occurred at beach
station P (south reference) in June I98O. Data indicate however that larval
black crappies hatched from inland sources may drift into the adjacent Lake
Michigan area. During May and June 1979» sporadic densities as high as 1^9
larvae/lOOO m^ were reported at beach station P (south reference) with
decreased densities out to station F (15 ntf south) (13 larvae/lOOO m^) . Water
temperatures when larvae were collected ranged from 9*0 to I6.5 C. The
discharge canal, in which crappies have been observed spawning, may serve as a
periodic source of black crappie larvae in the future.

Freshwater Drum

Freshwater drums are rare in the area of the Campbell Plant as only two
specimens were collected at Lake Michigan stations, one (460 mm) in September
1978, and one (63O mm) in November 1980. Their occasional presence in
impingement samples at Campbell Units 1 and 2, as well as Pigeon Lake (Jude et
al. 1979d) indicate that there may be a small population in the Pigeon Lake
area. As would be expected from the low density of adults, no larval drums
were collected in the area of the plant. The species appears to have little
ecological significance in the vicinity of the Campbell Plant.

Lake Herring

Lake herring, also known as Cisco, occurred infrequently in our study
area. One individual (153 mni) was collected in June I98O during night
trawling at station N (9 m, north). The only other appearance of this species
over the 4-yr study occurred in August 1977 when a 389-mm female was
gill netted in Pigeon Lake (Jude et al. 1978).

Lake herring is a member of the subfamily Coregoninae which has shown a
dramatic increase in abundance during the k yr of sampling (see RESULTS AND
DISCUSSION, Unidentified Coregoninae ). Difficulty in identifying species of
the genus Coregonus allows for the possible inclusion of some lake herring
( Coregonus artedi i ) into this large taxonomic group, although bloater
( Coregonus hoy i ) are believed to comprise the majority of unidentified
Coregoninae collected in our study area.

305

Northern Pike

Northern pike is a common species in Pigeon Lake (Jude et al. 1978,
1979a» 1980, 1981a), They sometimes migrate into Lake Michigan, often moving
alongshore for great distances. Northern pike tagged in Pigeon Lake have been
recaptured as far south as Lake Macatawa (15 km south of Port Sheldon) and as
far north as Muskegon Lake (37 km north of Port Sheldon). In Lake Michigan
two northern pike were collected in 1978 and one was collected in I98O. They
were gillnetted at south transect stations 1.5"6 m in depth, in August and
October. These pike ranged in size from 255 to 77^ nint. Their rare occurrence
in Lake Michigan near the Campbell Plant suggests that Unit 3 operation will
not have any adverse affect on this species, and that Units 1 and 2 are not
affecting their distribution.

Bluegi 1 1

Bluegills were common in Pigeon Lake, but were rare in Lake Michigan near
the J. H. Campbell Plant. Several YOY bluegills 25*50 mm were collected in
Lake Michigan during 1977. 1978 and I98O. One yearling bluegi 11 (84 mm) was
caught in 1978. Most bluegills collected in Lake Michigan were seined at
north transect stations R and Q during September and October (Appendixes 7»
27* 28 and 29). One YOY bluegi 11 was trawled at 15 ^ at the south transect
during September 1978 and one YOY occurred in a larval sled tow during
September 1977* Water temperatures at time of capture ranged from 10. 3 to
19*0 C. All bluegills collected in the Lake Michigan study areas probably
originated from Pigeon Lake or the discharge canal.

Lepomis spp. larvae were collected at the north and south transects
during 1977. 1979 and I98O In densities varying from 48 to 267 larvae/1000 m^
(Appendixes 9. 10, 33. 35. 36 and 39)- Unidentified Lepomi s spp. collected in
the study area were probably bluegi 11 or pumpkinseed larvae. Since no sunfish
spawning occurred in Lake Michigan near the J. H. Campbell Plant, these
Lepomi s spp. larvae were probably carried to Lake Michigan via the discharge
canal .

Lake Sturgeon

The lake sturgeon has suffered the most abrupt decline of any species in
Lake Michigan (Wells and McLain 1973)- This species is rare in the area of
the Campbell Plant as only two were captured, one (584 mm) in July 1977 and
one (795 ni^ni) in May 1979 at stations Q (beach, south discharge) and L (6 m,
north) respectively. Water temperatures were 21 and 13 C. It is doubtful
whether plant operation will in any way effect a further demise of lake
sturgeon.

306

Brook Si Iverside

Only one brook si Iverside was captured in Lake Michigan during the study
period (October, 1977 at south reference beach station P) . Their occasional
but very rare occurrence in open water of Lake Michigan was corroborated by
Cook Power Plant collections (unpublished data. Great Lakes Research
Di vi si on) .

Green Sunfish

Green sunfish occurred in impingement samples taken at the J, H. Campbell
Plant in 1978. This species has, however, never been collected in Pigeon Lake
(Jude et al. 198la) . One YOY green sunfish (39 mm) was trawled at 9 m in Lake
Michigan during 1979* No adult or larval green sunfish have been collected in
Lake Michigan during the 4-yr study. These data suggest that this species
rarely enters the Lake Michigan habitat near the Campbell Plant.

Pumpki nseed

Pumpkinseed is a common species in Pigeon Lake. During the i*-yr study no
adult pumpki nseeds were observed in Lake Michigan samples. One YOY
pumpkinseed {kO mm) was seined at north transect beach station R during
October 1977 in a water temperature of 10 C and one YOY pumpkinseed was caught
in a larval sled tow at 1.5 m, north transect during September 1977 in a water
temperature of 17-5 C. These pumpkinseeds probably came from Pigeon Lake or
the discharge canal. Unidentified Lepomis spp. larvae collected in Lake
Michigan during 1977, 1979 and I98O (see RESULTS AND DISCUSSION, Blueqi II )
were probably pumpkinseed or bluegill larvae. These larvae were probably
transported by currents from the discharge canal to Lake Michigan.

Loqperch

Logperch was scarce in the study area. A few logperch were collected in
Pigeon Lake during 1979- A larval logperch was collected in Lake Michigan at
the 12-m contour on the south transect during I978. No juvenile or adult
logperch were caught during the 4-yr study. SCUBA divers, however, observed
logperch near the riprap of the jetties at the mouth of Pigeon Lake during
1978 and 1979 and near the riprap of the Unit 3 intake during I98I,

Smal 1 mouth Bass

Over the k yr, only two smallmouth bass were collected in Lake Michigan
near the Campbell Plant; both were collected in late summer I978 at stations
1-1.5 ni in depth. Additional sporadic sightings of this species near the rock
base of the Pigeon Lake - Lake Michigan jetties occurred in I978-I98O. As was
observed at the D. C. Cook Power Plant (Jude et al. I98O) , occasional
transient smallmouth bass will probably be attracted to the rocky substrate
near the intake and discharge area; however, no adverse plant impact on this
species was observed or is expected.

307

Bluntnose Minnow

The bluntnose minnow occurs in lakes, ponds, rivers and creeks (Scott and
Grossman 1973)- Although it is common inland (Becker 1976), it was not
frequently collected in Lake Michigan during our study. Bluntnose minnows are
common in Pigeon Lake (Jude et al. 198la) , but only 19 have been taken in Lake
Michigan: 15 in 1978 and k in 1979-

Of the 19 bluntnose minnows captured, 12 (25"^^ mm) seined in September
1978 at beach stations R (north discharge) and P (south reference) and three
fish 37"^2 mm seined at station P (south reference) in October 1979 were
probably YOY (Westman 1938). The remaining four fish, ^5-74 mm, were
yearlings or adults; three were seined from the three beach stations and one
was trawled at station D (9 m, south). All bluntnose minnows were collected
from August to November; most during the night. Water temperatures at which
fish were collected ranged from 12.8 to 26 C; the largest single catch of
bluntnose minnows was in September 1978 at station R at 19 C (12 fish). All
bluntnose minnows collected were immature or sex could not be determined. No
bluntnose minnow larvae were collected in Lake Michigan during our study.

Goldfish

The goldfish is an east Asian species which has been introduced in North
America. it has become abundant in shallow, vegetated, warm-water areas of
the Great Lakes region such as Lake St. Clair and Lake Erie (Scott and
Grossman 1973)- Only one goldfish was collected in Lake Michigan during our
study. In July 1978 a 73"nim immature goldfish was seined at beach station Q
(south discharge) at a water temperature of I9.O C. A few goldfish have been
collected from Pigeon Lake, but they are not common there (Jude et al. 198la) .

Fathead Minnow

The fathead minnow occurs in a variety of habitats, including lakes,
ponds and small streams (Scott and Grossman 1973) • However, they were rare in
our collections in Lake Michigan as only two were captured there, one each
during August 1978 and April 1979 (the latter one a fry taken during larval
fish sampling). Their occurrence in the area appears to be incidental.

Damaged Larvae

I ntroduction —

In the course of sample collection there are a number of factors which
may result in damage to larval fish specimens. The primary cause of larvae
damage is abrasion, which occurs when sand and other debris grind against
specimens during net tows and the subsequent sample processing. With few
notable exceptions, highest densities of damaged larvae occurred at the beach
and 1.5*m sampling stations. These areas have the greatest turbulence which
cause suspended sand and debris to be in highest occurrence in the samples
where they exhibit maximum abrasive effect. Another component of the damaged
larvae classification may be those larvae which died prior to our sampling and

308

were subsequently collected during sampling. These dead larvae probably
exhibit varying degrees of decomposition, often making them impossible to
distinguish from larvae which were subjected to abrasion.

When damage does occur to a larva, all practical methods were employed to

identify the larva to species. In some instances, however, elimination of

body parts or obscuring of pigmentation patterns precluded larva

identification. Hereafter, use of the term "damaged larvae'* will refer to
those larvae which were unidentified due to excessive damage.

When larvae are damaged beyond recognition, we can speculate as to their
identity based on the identity of larvae caught coincidental ly in the same or
adjacent samples. A summary of those larvae caught coi ncidental ly with
damaged larvae is presented in Table S^* Adjustment calculations to known
species caught coi ncidental ly with damaged larvae can be made assuming that
all species were equally susceptible to damage. Thus each species would be
represented among the damaged larvae in approximately the same proportion that
they existed in the identified component. The other assumption is that
damaged larvae belong to a species which was represented in the sample. It
was not possible to test the strength of each of these assumptions, however,
there was a clear indication that, based on length-frequency data, in some
instances, these assumptions were violated.

The following is a year-by-year summary of the occurrences of damaged
larvae in our samples. Although there are instances when considerable
adjustments of known larvae densities would result if damaged larvae were
assigned to species based on their proportional occurrence in the samples,
each case was carefully reviewed and it was determined that over the k yr
these adjustments, if made, would not have affected our results or conclusions
about any known species of larval fish in the area.

1977"

During 1977f 18 samples contained damaged larvae. In eight of these
samples, the only identifiable larvae present were alewives, thus making it
highly probable that damaged larvae were also alewives. Despite projected
adjustments of up to 100% on the reported densities of larval alewives (Table
5^), we feel that these adjustments would not have significantly altered
reported larval alewife distributional trends. The highest percent
adjustments for larval alewives would have been made on the lowest larval
alewife densities. Eight samples collected in 1977 contained more than one
identifiable species of larvae coincident with damaged larvae. In six of
these cases the resultant adjustments to all species present would have been
less than 10%, while the remaining two cases would require adjustments of 31-2
and 76.8%, involving both alewives and spottail shiner larvae. There were
only two samples collected in 1977 which contained only damaged larvae. In
each of these cases, assignment to alewife, spottail shiner or yellow perch
was feasible; however, the low densities reported would not have altered
observed trends for these species.

309

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316

1978-

Of the 81 samples collected in 1978 containing damaged larvae,
adjustments to known categories in the samples would have resulted in less
than 10% increases in 39 cases. In I9 of the remaining samples, alewife was
the only concurrently captured, known species, thus it is highly probable that
damaged larvae in these samples were alewives. Yellow perch was the only
concurrently caught species in three of the samples, while smelt was the only
concurrently captured species in one sample. It seemed warranted, based on
time of occurrence and concurrently caught larvae, to designate the damaged
larvae in the former sample as yellow perch. The identity of the larva in the
latter sample, which concurrently contained only smelt larvae, was probably an
alewife. This larva was 4.0 mm in late June, which was considered too small
for a smelt hatched during spring 1978.

Of the 19 remaining 1978 samples containing damaged larvae, 15 samples
contained a mixture of known species, making determination of the identity of
these damaged larvae difficult. Proportionally assigning damaged larvae to
species, based on the proportion each of the known species made up of the
sample would not result in any significant alteration of the results for these
species with two notable exceptions. The sample taken at beach station Q
(south discharge) on 7 June would have contained an inordinate density of
yellow perch i,f 66.7% of the damaged larvae were speculated to be yellow
perch. Length-frequency data show that larvae causing the high density of
damaged larvae were 5*0 mm and were more likely unknown minnow or spottail
shiner larvae. Additionally, the size range of 3*0-5»0 mm of damaged larvae
caught at station N (9 m, north) at the 2-m depth stratum in early July 1978
makes it more probable that they were alewives and precludes their
classification as smelt.

Four samples collected in 1978 contained only damaged larvae. With the
exception of the larva caught in late June at station F {I5 m south), which we
believe was a smelt based on its total length of 19 nftm, all remaining damaged
larvae in these samples were probably alewives.

1979—

Of the k2 samples collected in 1979 which contained damaged larvae, I8
samples would require adjustments of less than 10% if damaged larvae were
proportionally assigned to concurrently captured species. Thirteen of the
samples contained a single concurrently caught, known species, and assignment
to that respective species would not have altered our conclusions about these
species. Similarly, proportional assignment of damaged larvae in samples
which concurrently contained a mixture of known species would not have
significantly affected our conclusions about the distributional and abundance
trends of these species.

There were only four samples collected in 1979 in which only damaged
larvae were found. It is probable that those damaged larvae observed in early
June 1979 were smelt; whereas, those observed in early July were alewives.

317

1980—

Of the 2k samples containing damaged larvae in 1980, only 5 would require
adjustments of more than 10% if damaged larvae were proportionally assigned to
species. In four of these cases, alewives were the lone or predominant
species, and it is probable that damaged larvae in these samples were mostly
alewives. In the single case of the sled tow at beach station R (north
discharge) on l6 June I98O, there appeared to be equal probability that the
damaged larvae were yellow perch or alewives. In all cases where damaged
larvae alone were caught in the sample, the resultant densities were too low
to cause a significant change in our results.

FISH EGGS

I ntroduction

Occurrence of fish eggs in the study area gives added support to the
contention that the inshore zone near the Campbell Plant is used as a spawning
site for a number of Lake Michigan species. While the nondescript appearance
of many fish eggs precludes their identification, we can, based on our
knowledge of the biology of indigenous species, make some speculation on the
identity of eggs collected.

We feel that the majority of fish eggs in our samples were those of
spottail shiners and alewives. Additional species which are thought to spawn
in the study area are yellow perch, trout-perch, smelt, emerald shiner,
burbot, slimy sculpin, ninespine stickleback, johnny darter, white sucker,
longnose sucker, gizzard shad, lake trout and coregonids. Due to the fact
that slimy sculpins and ninespine sticklebacks lay their adhesive eggs within
nests and johnny darters lay their adhesive eggs on the bottom of submerged
objects, it was unlikely that we sampled the eggs of these species. White
suckers and longnose suckers were more apt to spawn in streams, and also have
comparatively larger eggs which would facilitate identification. Trout-perch
eggs contain an oil globule which would aid in distinguishing it from alewife
or spottail shiner eggs. Burbot eggs were eliminated from consideration due
to their occurrence in late winter. No field sampling was conducted in
January-March when the eggs of this species might be expected. Burbot eggs
were collected during December at the D. C. Cook Plant (Jude et al. 1979b).
Eggs of emerald shiners have a large per ivi tel 1 ine space which would
facilitate separation from all other eggs. Eggs of yellow perch and smelt are
highly characteristic and could easily be identified. Gizzard shad eggs could
possibly be in our samples; however, absence of spawning adults in the area
diminishes the possibility, with the exception of those eggs originating in
the discharge canal. Lake trout eggs were observed in the stomachs of round
whitefish collected in gill nets in November I98O, and SCUBA divers \n a non-
project dive found lake trout eggs within the newly laid riprap.

318

Undoubtedly the most effective gear for sampling fish eggs was the
benthic sled. This gear was only consistently used during 1978-1980, The
less consistent use of the benthic sled in 1977 is a reason for the lower mean
fish egg densities reported and precludes inclusion of I977 data in meaningful
year to year comparisons.

Seasona 1 D i s tr i but i on

Apr! 1 —

Fish eggs first occurred in April of only one of the k yr sampled (I978)
(Figs. 91-100). Since these eggs were found only at the north transect during
April 1978, we suspect the origin of the fish eggs was the discharge canal.
Warmer water temperatures there undoubtedly facilitated early spawning of
resident species. It is possible that these eggs were those of gizzard shad
which are known to spawn in the discharge canal. Mean densities of eggs
present (less than 2 eggs/1000 m^) suggested either very limited spawning, or
an extremely high dilution of the discharge water with Lake Michigan water in
the sampl ing area.

May—

During all years when sampling was conducted in May, fish eggs were only
collected at the north transect; densities were less than 50/1000 m^. Again
this may suggest a contribution of eggs from the discharge canal or it may
reflect some limited initial spawning in Lake Michigan near the discharge. If
eggs we collected were the result of spawning occurring in Lake Michigan
during May of these years, it was likely that alewife or spottail shiner were
the species involved.

Early June —

The first occurrence of fish eggs at both transects occurred in early
June of all years sampled. In all years at all depth groups, except 12-15 m
during 1978, north transect fish egg densities exceeded those of the south
transect, which further suggests either a contribution of fish eggs from the
discharge canal or a higher level of spawning activity In the area of the
discharge canal compared with the reference transect. With few exceptions,
the difference In mean water temperature between transects was generally less
than 1.5 C. A comparison of mean egg densities among years indicates there
was more intense spawning activity in early June I978 and I98O compared with
1979. which appeared to be related to water temperature. The highest inshore
water temperatures were present in I978 coincident with highest early June
fish egg production, while lowest early June fish egg production in I979
corresponded to generally lower water temperatures. With the exception of the
high mean density of fish eggs at the 12- and 15-m south transect stations in
early June 1978, there was a distinct trend toward decreased mean egg
densities with increased water depth (Figs. 91-100).

319

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3
Fig. 92. Density (no./lOOO m plotted on log scale) of fish eggs

collected during June to September 1977 at 6 and 9 m, 12 and 15 m

(all contours, depth strata and diel periods pooled) near the J. H.

Campbell Plant, eastern Lake Michigan. Horizontal line across each

bar denotes mean density while height of bar represents ± 2 S. E.

Midpoint of water temperature range (vertical line) at time of

collection is shown.

321

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depth strata and diel periods pooled) near the J. H. Campbell Plant
eastern Lake Michigan. Horizontal line across each bar denotes meai
density while height of bar represents ± 2 S. E. Midpoint of water
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325

1979

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326

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Late June — •

Trends in mean egg densities in late June of any year closely paralleled
trends in larval alewife abundance (see RESULTS AND DISCUSSION, Alewife ,
Larvae, Seasonal Distribution). During late June of the k yr sampled, highest
mean fish egg densities were reported in 1979 and I98O coincident with the
highest reported late June larval alewi f e densi ties. Higher inshore water
temperatures probably stimulated increased spawning activity in late June
1979t compared with early June of that year. Generally comparable early and
late June water temperatures in I98O allowed for increased spawning activity
in late June of that year. Decreased fish egg densities in late June I978
compared with early June of that year were probably caused by depressed
nearshore water temperatures. The reason for continued low mean densities of
fish eggs during late June 1977 despite generally increased water temperatures
was lack of use of the benthic sled; plankton tows alone were unable to
demonstrate trends in egg abundance.

As was found during early June, the highest mean densities of fish eggs
were in the nearshore (beach - 3 ni) area, with substantial declines with
increased depths (Figs. 91-100). An extraordinarily high mean density of fish
eggs (1.05 x lOVlOOO m') was observed in late June 1979 at the south transect
nearshore station group, which indicated that more substantial egg deposition
had occurred in this area than during late June of any year at either
transect.

Early July —

Considerable fish egg deposition was indicated in early July I978-198O.
Again, lack of sled tow samples in early July 1977 was the primary cause of
low egg densities in our samples at this time. The upwelling in early July
1979 may have caused low mean egg density (175 eggs/ 1000 m^) at the south
transect; however, the north transect beach to 3"ni stations seemed unaffected.
Uninterrupted contribution of eggs from the discharge canal to the north
transect stations even during times of upwelling may explain this.

In all years, mean densities of fish eggs at north transect stations in
early July exceeded those of the south transect. The distribution of fish
eggs in the study area continued to be primarily nearshore (beach - } m) at
both transects in all years (Figs. 91-100).

Late July —

The level of spawning activity of alewives and spottail shiners in late
July varied considerably from year to year. During these years, no
correlation between water temperature and spottail shiner larvae, alewife
larvae or egg abundances was observed. During late July 1977" 1979. mean
densities of larval alewives and spottail shiners (see RESULTS AND DISCUSSION,
Alewife and Spottai 1 Shiner , respectively) diminished compared with early July
of these years, apparently in response to cold-water upwel lings.
Coincidental ly during these years, densities of fish eggs were generally
higher in the nearshore zone during late July compared with early July

330

(Figs. S^'^OO) . As in early July of all years, north transect stations had
higher mean densities of eggs compared with south transect stations.
Additionally, eggs were primarily distributed at the beach to 3"""i stations;
however, densities at the 6- to 9""ni stations of both transects in late July
1980 were the highest reported at this station grouping of all years or time
periods. This may be related to eggs spawned in the discharge canal being
pumped out to the 6-m contour by the offshore discharge, which began operation
in December 1979* We are unsure, however, whether the discharge of eggs at
the 6- and 9~(n north station grouping would cause increased egg densities at
south transect stations at this contour. Densities of larval spottail shiners
exhibited similar trends: mean densities at the 6- and 9""^ station grouping
in 1977-1979 were less than 100 larvae/1000 m^, while densities at these
stations in I98O often exceeded 100 larvae/1000 m^. This may be supportive of
the contention that eggs and larvae from the discharge canal are being
transported offshore by the discharge system, or may simply indicate that
there was increased spawning activity in the area of the 6- and 9~»n station
grouping compared with other years.

August and Septembei —

The first sampling period of August in I978-I98O showed continued
spawning activity with mean densities of eggs exceeding 2500 eggs/ 1000 m^
during all years at the beach-3*'" station grouping. Again north transect egg
densities exceeded south transect densities, and eggs were markedly more
concentrated nearshore.

Later August sampling in I978-I98O indicated that spawning activity had
appreciably diminished in the area as mean densities greater than 20 eggs/1000
m^ were not observed in any year. This trend continued into September, when
no densities exceeding 5 eggs/ 1000 m^ were observed in any year. Although
these data might indicate very little spawning activity, presence of newly
hatched larval alewives in September of 1979 (see RESULTS AND DISCUSSION,
Alewi fe ) indicates that spawning does occur to some degree in late August and
September .

Plant Effects

A Wilcoxon signed ranks test combining data from 1977 to I98O indicated
that densities of fish eggs were very significantly higher at the north
transect compared with south transect stations ( a» less than .001). There
are a number of possibilities which might explain the observation of higher
egg densities at north transect stations. Foremost, our observations in the
discharge canal lead us to believe that there are resident populations of fish
which are able to spawn there successfully. We believe that eggs spawned in
the discharge canal were a major component of the eggs in our samples taken at
the north transect. This contention is, in part, supported by the higher
densities of larvae found in samples from the 6- and 9"ni contours when the
discharge was moved offshore in I98O. There is also a possibility that the
offshore warm-water discharge or associated riprap and current encouraged more
spawning to occur in the area of the discharge canal, and thus more eggs were
found there. This contention is supported by the fact that larval, juvenile

331

and adult spottail shiners were generally more abundant at the north transect;
however, alewife abundances were not significantly different between
transects.

SCUBA OBSERVATIONS

1977

I ntroduction —

SCUBA dives were performed in August 1977 prior to construction of the
Unit 3 water intake system. Diving was conducted to evaluate the potential
site for the presence of important spawning and nursery grounds. A complete
description is given in Jude et al . (1978); a brief summary of findings will
be repeated here.

Results —

SCUBA observations at each of the transects swum in the vicinity of the
Campbell Plant on 9"10 August 1977 are summarized below in three categories:
physical, limno logical and biological.

Physical Observations —

(1) Bottom sediments in the vicinity of the transects swum consisted
exclusively of sand, primarily fine-grained and of homogeneous size.

(2) In all instances, grain, size of substrate increased with decreasing
depth. A distinct transition zone (from fine to coarse sand) occurred at
approximately the 7-5*ni contour. Coarse sand and occasional pebbles
extended from the 7-5" to the 6.0-m contour.

(3) A few areas of fine sand overlain by several millimeters
encountered, primarily offshore from the 7»5-n! contour,
concentrated in troughs of ripple marks.

of silt were
Silt was often

{k) Substrate was entirely shifting-sand; rocks, gravel, clay and heavy
were not encountered.

si It

(5) Ripple marks at stations deeper than 7*5 ni were generally small (2-5 cm
trough-to-crest, 10-20 cm crest-to-crest and 30""60 cm long) and were not
consistently developed from any specific direction. Larger and more
pronounced ripple marks were observed from the 7-5"'n^ contour shoreward.

(6) Bottom profile was flat and even; rises, depressions and sudden drop-off s
were not encountered.

332

Limno log leal Observations —

(1) Slight variations (1-4 C) in water temperature were noted between
locations. Highest water temperature recorded (25 C) was at the 5^2-m
station in front of the jetties, and may have resulted from heated
discharge water flowing south and being deflected offshore by the
jetties. Vertical temperature stratification was not encountered.

(2) Secchi disc readings remained relatively constant ranging from 3.0 - 4.0
m. Generally, horizontal visibility along the bottom increased with
decreasing depth as a function of increased light penetration. An
exception occurred at the jetties (dive no. 3) where visibility increased
from 2 m to 3 ni despite increasing depth. No explanation of this
occurrence was apparent.

(3) Suspended material was finely particulate in nature; composition of
particulate matter was indiscernible to the unaided eye.

Biological Observations — .

(1) Loose algae were not found.

(2) Macroscopic accumulations of per iphy ton were not observed except when an
occasional large substrate (e.g., tree branch, rock, trash) was
encountered.

(3) Small (2-10-cm diameter) clumps of loose aquatic plant material were
infrequently observed. A consistent pattern of occurrence was not
determined but clumps appeared to occur more frequently at deeper (6-12
m) stations. Composition of clumps appeared to be similar. One sample
was collected and found to be primarily the aquatic vascular plant
Myr iophyl lum sp. and associated algae.

(4) Several tree branches and one log were encountered at isolated locations.

(5) Small aggregates (1-cm thick - approximately one handful in volume) of
organic debris were occasionally observed. Debris was composed primarily
of unidentified decayed material and pieces of terrestrial vegetation.
Material was concentrated in troughs of ripple marks. Organic debris and
floe were more abundant offshore from the 7-5"n^ contour; very little was
observed at shallow (6.0 m) stations.

(6) Thousands of snails ( Valvata sp.) were seen on the bottom within the
south reference transects (dives no. 2 and 7) between the 11.6- and 9-l-ni
contour. Density of snails was estimated to be 100-300/m^. Large
concentrations of snails were not observed at other stations; often none
were seen.

(7) Other macroinvertebrates were not observed; however, pieces of sphaeriid
and gastropod shells were abundant, concentrated in troughs of ripple
marks.

333

(8) Young-of-the-year alewives (20-30 mm TL) were observed at many but not
all locations. Numbers were estimated to range from 1 to 30/m^ for the
water volume examined. Fish were most frequently seen in schools,
although larger numbers of fish may simply have been more highly visible.
During other underwater studies we have observed that YOY alewives tended
to school together during daylight hours. Fish appeared to remain
predominately within 2 m of bottom, but a few schools were noted higher
in the water column.

(9) Other species of fish were not observed,

1978-1979

No SCUBA observations were made in Lake Michigan during 1978 or 1979*
Efforts were directed at the intake canal of Units 1 and 2.

V

I ntroduction —

The underwater observation program In I98O was designed to facilitate
monitoring of the J. H. Campbell Plant's Unit 3 intake structures and
associated riprap areas. Observational methodologies have been devised to
allow divers to qualitatively and quantitatively assess and describe physical
and biological characteristics of the study area, both spatially and
temporally, and explore the relationship of observed changes with operation of
the power plant.

Discussion of visual observations will occur in the following format:
sediment, turbidity, per iphyton, loose algae, invertebrates (attached
invertebrates, mollusks, and others), fish, eggs and other observations.

Results —

Sediment — Encroachment of sand onto the riprap area was observed in I98O.
The layer of sand had increased from a trace (barely detectable) in July to
about 1 mm by October. Dorr (unpublished data. Great Lakes Research Division)
reported an average floe layer of 2-3 mm on the Cook Plant riprap near
Bridgman, Michigan during I974-I98O.

Ripple marks were often observed in the sandy areas adjacent to the riprap
and at the south reference station. Generation appeared to have occurred from
the west, southwest or northwest. Ripple marks observed were small with wave-
length less than 22 cm, amplitude less than 6 cm and length along crests less
than 25 cm.

Turbidi ty — Visibility within the study area during any particular dive
series varied little between the south reference station and the intake
station. Secchi disc readings ranged from 1.5 to 3-5 m at the intake and

33^

south reference station. There appeared to be no increased turbidity
associated with the Unit 3 intake risers* The least turbid conditions were
associated with periods of warmest water temperatures.

Periphyton and loose algae — One 5"cm diameter piece of riprap was
collected from the intake area to analyze composition of periphyton. Twenty-
six periphytic algal taxa were identified during sample analysis including 21
diatom taxa, 3 green algal taxa, and 2 blue-green algal taxa. The algal
component of the periphyton analyzed was relatively depauperate and lack of
the green alga Cladophora was noted. The riprap associated with the D. C.
Cook Nuclear Plant located farther south in Lake Michigan is similar in
location and composition to that of the Campbell Plant. Although Cook Plant
riprap was placed in 1972, luxurious growths of Cladophora were not noted
unt i I summer 1975*

The Campbell Plant riprap was basically uncolonized and free of periphyton
during I98O. In the upcoming years increased periphyton colonization on the
Campbell Plant riprap is expected. Because of the intake manifold depth (11
m) at Campbell, potential for growth as luxuriant as that seen at the
D. C. Cook Plant is diminished.

Small clumps (3-25-nim diameter) of loose algae were observed periodically
at the sou^h reference station and at the sand/riprap interface (densities
ranged from zero to k clumps/m^) . Large accumulations (i.e., masses or mats)
of algae were not observed. Algae appeared to be the major constituent of
most clumps. Macrophytes were not observed.

Invertebrates — Sphaerids (fingernail clams) were observed frequently at
the south reference and intake reference stations. Live specimens were not
encountered, probably because only the exposed surface of the bottom was
examined, not the underlying strata. Winnell and Jude (1979) found that in
1978 Sphaer ium spp. were numerous at 9-, 12- and 15-m depths, but were most
abundant at I5 and 20 m in 1977* Valvata sp. (snail) were observed on the
intake risers during August. The large interstices caused by the large size
of the limestone comprising the riprap could contain many more unattached
invertebrates but it was not physically possible to examine these areas. One
Baetidae (mayfly) nymph was observed in July on the intake manifold riprap.
No evidence of bryozoan or freshwater sponge colonies on the riprap was found.
The attached invertebrate Hydra showed a notable increase during the period
July through October 198O. Hydra were observed on the fine-mesh screens, the
intake risers, and on the riprap. Although Hydra did not clog up screen
openings, the potential for biofouling by Hydra exists. Colony height reached
1.5 mm by October. Lack of any heavy algal growth may facilitate the growth
of Hydra . Dorr (unpubl i shed data. Great Lakes Research Division) reported
that heavy algal growth precluded the growth of attached invertebrates at the
D. C. Cook Plant; Hydra were observed in large numbers on sides and undersides
of rocks where algal growth was reduced.

Fish eggs — Slimy sculpin eggs were collected from the riprap of the intake
line during preliminary dives in June. These eggs were in an advanced stage
of embryonic development and hatching began within 15 min of collection.

335

These eggs were collected from small, 2-5"cm diameter riprap. The present
riprap overlies this smaller-sized stone, and should provide good nesting
sites for slimy sculpins. Fish eggs were observed on the sand at the south
reference station in July and August. They were most likely alewife eggs and
were not viable (decomposition was beginning). During July, fish eggs were
also observed at the sand/riprap interface near the intake manifold.
Densities were low (3"5/nrt*) . During a non-project dive in December lake trout
eggs were collected from the intake line riprap i n 9 n' of water. Several were
in the early stage of embryonic development.

Based upon these observations, the riprap substrate should provide good
spawning and incubating habitat for demersal spawners such as slimy sculpin,
johnny darter, lake trout and yellow perch.

F i sh — Nine species of fish were observed during the study period (July-
October 1980) and listed in descending frequency of sightings (measured as
presence or absence, not as numbers of fish) during dives were: alewife,
johnny darter, yellow perch, spottail shiner, trout-perch, slimy sculpin,
ninespine stickleback, mottled sculpin and burbot. Lake trout were observed
during December (non-project) dives. Multiple sightings of all species,
except burbot gnd mottled sculpin, often occurred during a dive; usually less
than five were seen. YOY alewives and adult spottails were often seen in
schools (alewife 20-250, spottail IO-3O) . Schools of YOY alewives were
observed in September and adult spottails in July. Seasonal occurrence and
abundance of adult and juvenile alewives and spottail shiners in field catches
were coincident with diver observations.

More fish species and greater numbers were observed at night than during
the day. Fish abundance and species diversity was highest In July and August;
seven of the nine species encountered during the study were observed in July
and August. Number of fish observed was highest in August due to the large
schools of YOY alewives. Very few fish were observed during October. Yellow
perch were more active during the day, but rested on the riprap at night and
could be easily grasped. Sculpins were more active and visible at night
coming out of the rock interstices to rest on the riprap. During a
preliminary dive in June large numbers of sculpins (10 per m^) were observed
guarding nests on the smaller (2-5~cm diameter) riprap which underlies the
present strata of large (l-2.5~nt diameter) riprap, which will make
observations of fish very difficult in the future because of the cryptozoic
nature of slimy sculpins. Although yellow perch spawning was not observed in
1980, (spawning was probably completed before SCUBA observations began) perch
most likely will use the riprap as a spawning substrate. Johnny darters were
more active during the day than night but were more alert than yellow perch at
night. Schooling was observed for alewives and spottail shiners; sculpins and
johnny darters were randomly distributed.

Numbers of fish observed were much higher in the riprap area of the intake
manifold than either sand substrate reference area. Dorr and Jude (I98O)
reported similar observations at the D. C. Cook Plant. Only one johnny darter

336

was observed at the reference station south of the plant. Spottails, trout-
perch, and smelt were observed at the reference area adjacent to the intake
mani fold, all at night.

Other observations — During July and August large numbers of dead and live
adult alewives were observed inside the intake risers. These fish were
obviously residents of the discharge and intake channel. They apparently swam
through the intake line into the risers; quillbacks and spottails were also
observed. Dives in the intake channel revealed a large population of adult
alewives was present. They were observed orienting themselves against the
flow from the intake pipe, apparently feeding. Alewives were observed well
i nto the i ntake 1 i ne.

Summary and Conclusions —

Twelve dives were performed during the period July-October I98O: three
during each month. Both sand and riprap substrates were examined. The sand
and floe covering the riprap was about 1 mm thick by the end of October.
Periphyton growth was sparse with a notable absence of Cladophora .
Disturbance of the area due to construction activity (mechanical scour) and
the 11-m depth probably limited Cladophora growth. Sphaeriid shells were
frequently observed on the sand substrate, but not on the riprap. Unattached
invertebrates were rarely observed in the riprap area. The attached
invertebrate Hydra became increasingly abundant during the study period. They
were most noticeable on the intake risers and screens. Alewife, spottail
shiner, slimy sculpin and lake trout eggs were observed on the riprap in I98O.
Nine species of fish were observed during the study period. Listed in
descending order of frequency of observation they were: alewife, johnny
darter, yellow perch, spottail shiner, trout-perch, ninespine stickleback,
slimy sculpin, mottled sculpin and burbot. Lake trout were observed during
December (non-project dive). Young-of-the-year alewives were abundant during
September. They occupied the upper one third of the water column over the
intake manifold. Large numbers of slimy sculpins were observed nesting on the
riprap during preliminary dives in June, but dumping of additional (larger)
riprap over nesting sites most likely decreased successful incubation of their
eggs. Numbers, species diversity and activity of fish were highest at night
and were much higher in the riprap area than in sand substrate areas.
Seasonal abundance of alewives and spottail shiners, as determined from diver
observations, coincided with field collections of these species. Due to
construction activities this study did not begin until July and therefore
complete seasonal trends in biological activity and abundance could not be
documented by diver observations. A more intense sampling effort will be
undertaken during I98I. Observations will be made from April to November and
a complete pattern of biological activity will be documented.

In conclusion, compared with the surrounding inshore zone of the lake (I5
m or less), the riprap area has created an atypical, more diverse and more
sheltered habitat which attracts fish and other biota. The riprap area is now
in its early successional stages. With the passage of time, this area should
exhibit increased species diversity and abundance.

337

SUMMARY AND CONCLUSIONS

INTRODUCTION

This report summarizes k yr of preoperational fishery data for Lake
Michigan, with emphasis on the last year, I98O, which had not yet been
discussed in detail as had the previous 3"yr, 1977*1979* 't was our intent to
document the variability in the spatial and temporal distribution of larval,
juvenile and adult fish near the J. H, Campbell Plant, eastern Lake Michigan.
Data from the k-yr study were examined for each life stage for each species.
A description of spawning times, nursery areas and location of concentrations
of each appropriate age-group was made. Catch differences between transects,
among depth contours and years as well as whether plant operation has affected
the abundance of fish species were elucidated. We prepared distribution
graphs, length-frequency histograms, water temperature plots, statistical test
data and summarized our findings in preoperational years. These data sets and
conclusions will eventually be used as background data to evaluate any effects
of 1 full year of operation of Unit 3 on the Lake Michigan ecosystem,
particularly as it relates to fish.

TOTAL CATCH

During our if-yr study, 48 species of fish representing 17 far! lies, were
collected or observed in Lake Michigan near the J. H. Campbell Plant. They
included a wide range of species, including marine forms (alewife, smelt,
salmon, sea lamprey), a threatened species (lake sturgeon), sport fish (yellow
perch, trout), commercial fish (bloaters, lake whitefish) and forage species.

The yearly catch of juvenile and adult fish during 1977" 1980 was
dominated by alewives in 1977 (69%) and 1978 (^9%) t while rainbow smelt
assumed dominance in 1979 (38%) and I98O (44%) . Alewives were the second-most
abundant fish caught in I979-I98O.

Large alewife fluctuations were attributed to YOY abundance changes over
the years; the adult catch has remained relatively stable over the 4 yr.
Rainbow smelt produced strong year classes in 1979 ancl I98O, which contributed
to the large trawl catches of YOY and yearlings observed in these years.
Spottail shiner catch was relatively stable over the 4 yr ranging from 10% of
the total catch in 1977 (not a full year of sampling) to l8% in 1980. They
were the third-most common fish collected in Lake Michigan.

Trout-perch were the fourth- or fifth-most common species collected
during the study years, with I98O being the year of maximum catch. This year
was marked by a strong yearling age-group and good survival of adults from
1979.

Yellow perch comprised between 1 and 2% of the total catch each year,
usually ranking sixth in abundance (fourth in 1977)- Large year classes were
produced in 1977 and I98O, while cold inshore water temperatures in 1979t due
to frequent upwel lings and cold air temperatures, caused depressed yellow
perch catches.

338

The catch of unidentified Coregoninae, believed to be mostly bloaters,
rose dramatically during the course of the study from 1% of the catch in 1977
to 11% in 1980- They rose from the sixth-most often caught fish to fourth.
The increase is a lake-wide occurrence attributed to banning of commercial
harvest by gill nets and a decline or at least stabilization in alewife
populations.

A number of lesser-caught species, such as lake trout, carp and gizzard
shad, exhibited some catch differences over the 4-yr period. Lake trout were
caught in much higher numbers during I98O (after the newly laid riprap for the
Unit 3 intake was in place) than in previous years. However, lake trout were
abundant at both plant and reference stations. Slimy sculpins and johnny
darters (which are known to be attracted to riprap) and carp and gizzard shad
(documented as being attracted to thermal plumes), were not collected in
larger numbers in the vicinity of the plant.

Of the four gear types used for collecting juvenile and adult fish
(trawls, surface and bottom gill nets and seines), trawls collected the vast
majority of fish. Surface gill nets caught the least number of fish. This
gear was the only gear that fished directly in the thermal plume.

ALEWIFE

Alewife was the most abundant species in our catches during 1977^^978 and
second in abundance in 1979""1980 (Table 55)- Alewife larvae are the most
abundant larval fish during most of late spring and summer. Larval fish
abundance is strongly linked to favorable water temperatures; during 1979» a
year of frequent upwellings, alewife larvae catches were considerably reduced.
Statistical testing of larval fish densities pooled over the k yr showed no
significant differences existed between the reference and pi ant- influenced
transects. Examination of alewife density data for differences between
transects revealed that in 1978 more alewives were collected at the south
reference transect, in I98O more were observed at the north transect and for
1977 and 1979 no differences in larval density between transects were found.
Because of the yearly variability in preoperational alewife larvae densities,
a single year comparison in 1981 probably will be inconclusive. For trawl
catches of juvenile and adult alewives, no significant differences between
transects were detected.

Highest entrainment of alewife larvae will clearly occur during peak
alewife hatching times, usually July. During years of extensive upwellings
these peaks could be delayed until August.

RAINBOW SMELT

Rainbow smelt was the dominant species in our 1979-1980 catches. Many
YOY and yearlings were present in our trawl catches during these latter years
of our study. Smelt are an introduced marine species. Adults spawn in the
spring and then move offshore, returning inshore only during upwellings (Table
56). YOY inhabit the inshore zone during most of the summer and fall, while
yearlings are present during spring and early summer. Densities of smelt

339

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larvae were low compared to other major species in the area. A statistically
significant catch difference (more caught at plant transect stations) between
transects was documented for larval smelt in 1979"1980. Since rocky substrate
from construction of the offshore intake and discharge system existed during
1979 and 1980 from near shore to 1 1 m, smelt were thought to have spawned
there. Survival rates were also expected to be higher in this habitat, thus
contributing to the higher larval densities recorded there.

Adult and juvenile trawl catch statistical analyses revealed no
significant catch differences in 1977 between transects; however, in I978-I98O
significantly more smelt were consistently taken in the vicinity of the plant
along the north transect.

Trawl catches were comprised of mostly YOY and yearlings, which were
present in higher abundances in the plant area. Construction of the intake
structures during 1979" ^980 corresponded with years of maximum catch
differences. In 1978, when no intense disruption of the study area by
construction activities occurred, catches were similar between transects.
Increased food supply, the riprap or currents in the vicinity of the plant
apparently attract YOY and yearling smelt.

SPOTTAIL SHINER

Spottail shiners are benthic minnows commonly found In the vicinity of
the Campbell Plant. They were consistently the third-most abundant fish in
our catches, being caught during every month sampling was conducted.
Spottails migrate shoreward from deep water starting in April and May, spawn
during June and July and remain inshore, usually in the beach zone to 9 nn of
water, until late fall when they migrate offshore (Table 57) • Larval
spottails are abundant in the beach zone to 3 nn where most spawning occurs.
YOY migrate to deep water in October. Spottails feed on benthic organisms,
but are seldom eaten by piscivorous fish in our study area.

Timing of construction activity in Lake Michigan was correlated with
statistical differences in catches noted for larval, juvenile and adult fish,
making definitive statements about plant effects difficult. In 1977. when the
thermal discharge from Units 1 and 2 was onshore, no catch differences between
transects were noted for larval or adult fish. From 1 979*1980 however,
coincident with initiation and near completion of intake and discharge
structure construction in Lake Michigan, larval, juvenile and adult fish were
statistically more abundant in the vicinity of the plant. Reasons for the
increased abundance of all age-groups of spottails at the plant transect are
not clear; however, increased food supply, because of bottom disruptions in
the area and increased spawning substrate provided by the riprap (which
extended all the way to shore) are two possible causes.

Entrainment of larval spottails during future years is expected to be
limited to fish which spawn on the riprap in the vicinity of the intakes. To
date, the overwhelming majority of spawning occurs in the nearshore (beach to
3 m) zone, where larvae were most abundant. Since YOY spottails are generally
demersal and most often found inshore, they probably will not come in contact

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with the Unit 3 intake screens, which are situated off the bottom in 11-m
water. However, some movement off bottom was documented for juveniles and
adults, as between 0.1 and 9«8% of surface gill net catches during 1977"1980
was comprised of spottails. In addition, spottails may be vulnerable in the
fall during seasonal movements offshore.

TROUT-PERCH

Trout-perch was the fourth-most abundant species collected during the 4-
yr study period comprising from 1 to 3% of the total catch. They are a
demersal species, which reach a length of 160 mm. They feed primarily on
benthos and are seldom fed on by piscivorous fish in the study area. Trout-
perch have an extended spawning period from April through August (Table 58).
Most fish were caught by trawls. Trout-perch were caught mainly at night and
they exhibited a diel horizontal movement toward shore during the night and
back to deeper water during the day. We have not collected large numbers of
trout-perch larvae because we believe so few adults spawn during a given month
that their larvae are never very abundant. Entrainment potential of trout-
perch is expected to be negligible because of their demersal habit. We
statistically compared the juvenile and adult catches between the reference
and plant transect 6-m stations in 1977 and found no significant difference.
In 1978-1980, a significantly greater catch was registered at the plant
transect station L (6 m, north) compared with reference station C. One year
(1979). contributed to the significant AREA and YEAR X AREA interaction.
During 1979f maximum construction activity on the new intake system in Lake
Michigan was transpiring. Food stirred into the water column or decreased net
avoidance may have caused the higher catch at plant transect stations. Trout-
perch larvae data also suggest that the riprap may be attracting spawning
trout-perch as almost two-thirds of the kk larvae caught during the i*-yr study
were taken in I98O, the first year the riprap area was completed during the
trout-perch spawning season.

YELLOW PERCH

Yellow perch are one of the important sport fish in our Lake Michigan
catches. They comprised from 1 to 2% of the catch, usually ranking sixth in
abundance. Yellow perch are offshore during the winter, migrate inshore
during spring and usually spawn sometime in late May or early June (Table 59) •
Exact spawning areas are unknown in the Campbell vicinity. Some spawning may
occur on the jetties and on the newly laid riprap, as these types of areas
appear to be optimal habitat. Larval perch are not common in our collections,
but do occur in modest densities during June. They quickly grow to a size
(around 10 mm) where they avoid all our sampling gear, until late July-August
when many YOY are seined in the beach zone. In the fall perch migrate
offshore.

Catches of yellow perch during the 4-yr study varied considerably
depending on water temperatures in the study area. During 1979» a year of
frequent upwel lings of cold water, yellow perch apparently sought warmer
temperatures elsewhere, thus depressing total catch for that year.
Statistical evaluations of juvenile and adult catch data showed no significant

344

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346

differences between transects in 1977 and 1978. In 1979 more fish were caught
at the north transect; however, as noted, 1979 was a year of low catches and
the low sample size at 6-m stations decreased the validity of inferences about
results. In I98O, more fish were caught at the south reference transect.
Again, catch differences between transects for I98O were not consistent and
one spurious high catch in September was thought responsible for the
significant catch difference result. Therefore, it was our belief that no
valid and consistent differences in catch were present for yellow perch. A
similar finding was rendered for larvae; no overall catch difference was
apparent between transects. However, more were collected in June 1979 at the
north (plant) transect. Depending on the extent spawning perch use the
riprap, we may see consistently higher numbers in these areas in future years.
Entrainment potential for yellow perch could be high as a result, since newly
hatched larval perch (5-6 mm) move passively with^ water masses. Once they
reach about 10 mm (growing at a rate of about 0.1 mm/day), they are very
mobile and we rarely collect them in plankton nets. Depending on how these
larger larvae react behavioral ly to the intake screens, even perch this size
have the potential to be entrained, for example, if they perceive the
structures as escape or concealment habitat.

UNIDENTIFIED COREGONINAE

Members of the subfamily Coregoninae are very difficult to separate
consistently; therefore, we use the subfamily designation. Most are believed
to be bloaters. Members of this group were part of the historical complex of
whitefish species, which inhabited all parts of the lake. With invasion of
the sea lamprey, overfishing and introduction of exotic species, most members
of the "chub complex'* became extinct. The bloater is one species, the
smallest in size, which has survived the upheaval in low numbers. Recently,
due to banning of commercial harvest with gill nets and a long term decline
and stabilization in alewife populations, this group is expanding. They went
from 460 in our collections in 1977 to 893^ in I98O. We sample only the
fringes of this offshore population (they prefer cold water) and most fish
collected have been YOY and yearlings. Bloaters are inhabitants of the deep
basins of Lake Michigan and they are only found inshore during upwel lings
(Table 60) . They also spawn in very deep water during winter (72-108 m) , but
we have collected some of their larvae inshore. Bloaters feed on benthos and
zooplankton and traditionally were the mainstay of lake trout diets. We have
not found any fish we could identify as bloaters in the stomachs of
piscivorous fish collected to date.

Larval bloaters were collected in highest numbers during I98O (^9), while
combined catch for 1977-1979 was only 11 larvae. These were too few fish for
definitive statements, but larval densities on the south transect were twice
those of the north in the beach zone during April, the month of highest catch
in 1980. For juveniles and adults, trawl catches in I978-I98O on the north
transect were statistically greater than those on the south transect. This
difference was most pronounced during 1979 when construction activity in Lake
Michigan was at its peak. Increased turbidity may have decreased net

347

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348

avoidance leading to the higher catch or increased densities of suspended food
organisms in the water column may have attracted fish. Most fish trawled were
YOY and year 1 i ngs.

FISH EGGS

Collection of large numbers of fish eggs in the inshore zone of Lake
Michigan emphasizes the importance of this area as nursery grounds. Most eggs
we believe to be those of alewife and spottail shiner, but a number of other
species are not precluded. Other species, such as sculpin and johnny darter,
lay their eggs on the undersides of rocks and only SCUBA observations
confirmed their presence. Yellow perch egg masses are also suspected to be
laid in areas of rocks that we cannot sample with our standard gear. The
benthic sled was the most efficient gear for sampling eggs. June was the
first month when high densities of fish eggs occurred; maximum densities
occurred in late June. September was the last month in which eggs were
observed. However, lake trout eggs were discovered by SCUBA divers in
November. Highest densities of eggs were found in the beach to 3""^ zone, with
diminished quantities farther offshore. Considerably more eggs were found at
the plant transect than at the reference area during 1977"1980. Source of
these significantly higher quantities of eggs are thought to be the onshore
and offshore discharge of eggs spawned in the intake and discharge canals.
Undoubtedly, the offshore discharge of warm water, currents and riprap
encouraged spawning in the vicinity of the plant in I98O.

SCUBA OBSERVATIONS

Underwater observations of the Unit 3 intake and discharge area during
1980 were designed to qualitatively and quantitatively assess the physical and
biological characteristics of the area. We also assessed how the wedge-wire
screens and their associated structures and riprap were used by the ecological
community, monitored colonization of the screens by algae and invertebrates
and documented what fish frequented the area for cover, food and spawning. We
found that sand had encroached onto the riprap area in I98O. Regarding
visibility (water clarity), no differences between transects were observed. A
rock examined for per iphy ton contained 26 species of diatoms, 3 species of
green algae and 2 species of blue-green algae. No Cladophora was observed,
which was unexpected, since Cladophora is a common green alga which attaches
itself to plant intakes, breakwaters and other solid objects in the photic
zone of Lake Michigan. The riprap was newly laid in 1979 and early I98O, and
we found that it was basically uncolonized and free of extensive periphytic
growth. Fingernail clam shells were frequently observed at both transects,
and a snail ( Valvata sp.) was observed on the intake risers in August. Hydra ,
a coelenterate, showed an increase over the period July-October I98O. They
were found on the wedge-wire screens, intake risers and riprap. Slimy sculpin
eggs were collected from the riprap in June, while suspected alewife eggs were
found on the sand at the reference station in July-August. Lake trout eggs
were collected from the riprap in December I98O. Nine species of fish were
observed during the study including: alewife, johnny darter, yellow perch,
spottail shiner, trout-perch, slimy sculpin, ninespine stickleback, mottled
sculpin and burbot. Lake trout were seen in November. Higher abundance and

349

diversity of fish were observed at night. More fish were on the riprap than
at comparable sandy areas on the south transect, demonstrating the well known
fact that fish are attracted to these rocky areas. During July-August, many
dead and live alewives along with with live spottails and quillbacks were
observed within the intake risers. These fish are believed to be residents of
the intake canal .

350

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359

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362

INDEX TO FISH SPECIES

Alewife, 55

Black crappie, 305
Bluegill, 306
Bluntnose minnow, 308
Brook silverside, 307
Brown trout, 292
Burbot, 299

Central mudminnow, 302
Channel catfish, 298
Chinook salmon, 288
Coho salmon, 289
Common carp, 29^

Deepwater (fourhorn) sculpin, 303

Emerald shiner, 271

Fathead minnow, 308
Freshwater drum, 305

Gizzard shad, 286
Golden redhorse, 301
Golden shiner, 29^
Goldfish, 308
Green sunfish, 307

Johnny darter, 268

Lake herring, 305
Lake sturgeon, 306
Lake trout, 255
Lake whi tef ish, 290
Logperch, 307
Longnose dace, 3OI
Longnose sucker, 279

Mottled sculpin, 3OO

Ninespine stickleback, 27^
Northern pike, 3O6

Pumpkinseed, 307

Qui 11 back, 303

Rainbow smelt, 103

363

Rainbow trout, 292
Round whi tef ish, 284

Shorthead redhorse, 298
Silver redhorse, 297
SI imy sculpin, 281
Smallmouth bass, 307
Spottai 1 shiner, 142

Trout-perch, 179

Unidentified Coregoninae, 205

Walleye, 302
White sucker, 264

Yellow bullhead, 303
Yellow perch, 217

364

APPENDIXES
TO

ADULT, JUVENILE AND LARVAL FISH POPULATIONS
IN THE VICINITY OF THE J. H. CAMPBELL POWER PLANT,
EASTERN LAKE MICHIGAN, 1977-1980.

DAVID J.JUDE, HEANG T. TIN, GEORGE R. HEUFELDER,
PHILIP J. SCHNEEBERGER, CHARLES P. MADENJIAN,
THOMAS L. RUTECKI, PAMELA J. MANSFIELD,
NANCY A. AUER, GEORGE E. NOGUCHI

Under contract with Consumers Power Company

David J. Jude, Project Director

Great Lakes Research Division
The University of Michigan
Ann Arbor, Michigan 48109

November, 1981

Al

A2

APPENDIXES

Appendix 1

Appendix 2,

Appendix 3'

Appendix 4<

Appendix 5,

Appendix 6.

Append i x 7 «

Append i x 8 .

Appendix 9*

Alphabetical listing of code letters and common names

of all fish species and species groups captured in

the vicinity of the J. H. Campbell Plant, eastern

Lake Michigan, 1977 to I98O A9

Meteorological and limnological parameters measured

during gillnetting, April to November I98O near the

J. H. Campbell Plant, eastern Lake Michigan.

* « surface gill net AlO

Meteorological and limnological parameters measured
during seining, April to November I98O near the J. H.
Campbell Plant, eastern Lake Michigan ^]k

Meteorological and limnological parameters measured
during trawling, April to December I98O near the J- H.
Campbell Plant, eastern Lake Michigan AI5

Meteorological and limnological parameters measured

during fish larvae sampling by plankton net, April to

September I98O near the J. H. Campbell Plant, eastern

Lake Michigan AI8

Meteorological and limnological parameters measured

during fish larvae sampling by sled, April to September

1980 near the J. H. Campbell Plant, eastern Lake

Michigan A42

Monthly length-frequency distributions of species

caught during April to December I98O in the J. H.

Campbell Plant study area, Ottawa County, Michigan.

Catches from all gear were pooled. Length intervals

given represent the mid-point of a 10-mm length

group A48

Monthly length-frequency distributions of most abundant

species caught in Lake Michigan during I98O in the

vicinity of the J. H. Campbell Plant, Ottawa County,

Michigan. Distributions were segregated by gear type.

Length intervals given represent the mid-point of a

10-mm length group A66

Number of fish larvae and eggs per 1000 m^ for north

transect stations in Lake Michigan near the J. H.

Campbell Plant, April to September 1980. D « day,

N « night, * = sled tow. See Appendix 1 for species

code identification A76

A3

Appendix 10,

Number of fish larvae and eggs per 1000 m^ for south
transect stations in Lake Michigan near the J. H.
Campbell Plant, April to September I98O. D « day,
N = night, ^^ « sled tow. See Appendix 1 for species
code i dent i f i ca t i on

.A9^

Appendix 11

Appendix 12.

Appendix 13«

Appendix ]k.

Appendix 15 .

Appendix l6.

Appendix 17-

Appendix I8.

Appendix 19 .

Appendix 20.

Number of fish fry per 1000 m^ caught during fish

larvae sampling near the J. H. Campbell Plant, eastern

Lake Michigan, April to September I98O. D « day,

N « night, * « sled tow. See Appendix 1 for species

code i dent i f i cat i on A 1 09

Meteorological and limnological parameters measured
during gillnetting, June to December 1977 near the
J. H. Campbell Plant, eastern Lake Michigan.

* « surface gill net Al 15

Meteorological and limnological parameters measured
during gillnetting, April to November I978 near the
J. H. Campbell Plant, eastern Lake Michigan.

* « surface gill net AII8

Meteorological and limnological parameters measured
during gillnetting, April to November 1979 near the
J. H. Campbell Plant, eastern Lake Michigan.

* » surface gill net A 122

Meteorological and limnological parameters measured
during seining, June to November 1977 near the J. H
Campbell Plant, eastern Lake Michigan A125

Meteorological and limnological parameters measured
during seining, April to November I978 near the J. H.
Campbell Plant, eastern Lake Michigan A128

Meteorological and limnological parameters measured
during seining, April to November 1979 near the J. H.
Campbell Plant, eastern Lake Michigan A131

Meteorological and limnological parameters measured

during trawling, June to December 1977 near the J. H.

Campbell Plant, eastern Lake Michigan A132

Meteorological and limnological parameters measured
during trawling, April to December I978 near the J. H.
Campbell Plant, eastern Lake Michigan A137

Meteorological and limnological parameters measured
during trawling, April to December 1979 near the J. H.
Campbell Plant, eastern Lake Michigan c..Al45

A4

Appendix 21 .

Appendix 22.

Appendix 23*

Meteorological and limnological parameters measured

during fish larvae sampling by plankton net, June to

December 1977 near the J. H. Campbell Plant, eastern

Lake Michigan A 1^9

Meteorological and limnological parameters measured

during fish larvae sampling by plankton net, April to

September I978 near the J. H. Campbell Plant, eastern

Lake Michigan A 15^

Meteorological and limnological parameters measured

during fish larvae sampling by plankton net, April to

September 1979 near the J. H. Campbell Plant, eastern

Lake M i ch i gan A 1 6 1

Appendix 2k.

Appendix 25*

Appendix 26.

Meteorological and limnological parameters measured
during fish larvae sampling by sled, July to October

1977 near the J. H. Campbell Plant, eastern Lake

Michigan AI67

Meteorological and limnological parameters measured
during fish larvae sampling by sled, April to September

1978 near the J. H. Campbell Plant, eastern Lake

Michigan AI69

Meteorological and limnological parameters measured
during fish larvae sampling by sled, April to September

1979 near the J. H. Campbell Plant, eastern Lake

M i ch I gan • • A 1 76

Appendix 27 «

Appendix 28.

Monthly length-frequency distributions of species

caught during June to December 1977 in the J. H.

Campbell Plant study area, Ottawa County, Michigan.

Catches from all gear were pooled. Length intervals

given represent the mid-point of a 10-mm length

group ...* o. .AI83

Monthly length-frequency distributions of species

caught during April to December I978 in the J. H.

Campbell Plant study area, Ottawa County, Michigan.

Catches from all gear were pooled. Length intervals

given represent the mid-point of a 10-mm length

group * A 197

Appendix 29 <

Monthly length-frequency distributions of species

caught during April to December I979 in the J. H.

Campbell Plant study area, Ottawa County, Michigan.

Catches from all gear were pooled. Length intervals

given represent the mid-point of a 10-mm length

group A21 1

A5

Appendix 30.

Appendix 31

Monthly length-frequency distributions of most abundant
species caught in Lake Michigan during 1977 in the
vicinity of the J. H. Campbell Plant, Ottawa County,
Michigan. Distributions were segregated by gear
type. Length intervals given represent the mid-
point of a 10-mm length group o.

»A226

Monthly length-frequency distributions of most abundant
species caught in Lake Michigan during 1978 in the
vicinity of the J. H. Campbell Plant, Ottawa County,
Michigan. Distributions were segregated by gear
type. Length intervals given represent the mid-
point of a 10-mm length group

.A23^

Appendix 32.

Monthly length-frequency distributions of most abundant
species caught in Lake Michigan during 1979 in the
vicinity of the J. H. Campbell Plant, Ottawa County,
Michigan. Distributions were segregated by gear
type. Length intervals given represent the mid-
point of a 10-mm length group

.A2if5

Appendix 33 «

Number of fish larvae and eggs per 1000 m^ for north
transect stations in Lake Michigan near the J. H.
Campbell Plant, June to December 1977- ■ clay, N
N « night, * « sled tow. See Appendix 1 for species
code i dent i f i ca t i on «

.A260

Appendix 3^<

Number of fish larvae and eggs per 1000 m^ for north
transect stations in Lake Michigan near the J. H.
Campbell Plant, April to September 1978, D « day,
N « night, * « sled tow. See Appendix 1 for species
code i dent i f i cat i on

.A268

Appendix 35 «

Number of fish larvae and eggs per 1000 m^ for north
transect stations in Lake Michigan near the J. H.
Campbell Plant, April to September 1979- * clay,
N ■ night, * « sled tow. See Appendix 1 for species
code i dent i f i cat i on

.A286

Appendix 36.

Number of fish larvae and eggs per 1000 m^ for south
transect stations in Lake Michi.gan near the J. H.
Campbell Plant, June to November 1977* D = day,
N » night, * « sled tow. See Appendix 1 for species
code i dent i f i cat i on • o

.A30i*

Appendix 37. Number of fish larvae and eggs per 1000 m^ for south
transect stations in Lake Michigan near the J. H.
Campbell Plant, April to September 1978. D « day,
N = night, 3i5: = sjed tow. See Appendix 1 for species
code identi f i cat ion ,

,A3l8

A6

Appendix 38.

Number of fish larvae and eggs per 1000 m^ for south
transect stations in Lake Michigan near the J. H.
Campbell Plant, April to September 1979* D « day,
N » night, * = sled tow. See Appendix 1 for species
code identification

.A333

Appendix 39-

Number of fish fry per 1000 m^ caught during fish
larvae sampling near the J. H. Campbell Plant, eastern
Lake Michigan, July to October 1977* D " clay,
N « night, * « sled tow. See Appendix 1 for species
code i dent i f i cat i on

.A348

Appendix 40.

Number of fish fry per 1000 m^ caught during fish
larvae sampling near the J. H. Campbell Plant, eastern
Lake Michigan, April to September 1978- D « day,
N « night, * « sled tow. See Appendix 1 for species
code i dent if i cat ion

.A352

Appendix k] •

Number of fish fry per 1000 m
larvae sampling near the J. H.
Lake Michigan, April to September 1979
N « night, * « sled tow. See Appendix
code identification

^ caught during fish
Campbell Plant, eastern

1

D -
for

day,
spec i es

► A355

A7

A8

Appendix 1. Alphabetical listing of code letters and common
names of all fish species and species groups captured in Lake
Michigan near the J. H. Campbell Plant, 1977 to I98O.

Code

Common name

Code

Common name

AL Alewife MA

BC Black Crappie MM

BG Bluegill MS

BM Bluntnose Minnow NP

BL Bloater NS

BR Burbot PM

BT Brown Trout PP

CC Channel Catfish PS

CH Chinook Salmon QL

CM Coho Salmon RT

CP Common Carp RW

ES Emerald Shiner SB

FD Freshwater Drum SM

FS Deepwater Sculpin SP

GF Goldfish SR

GL Golden Shiner SS

GN Green Sunfish SV

GR Golden Redhorse TP

GS Gizzard Shad UC

JD Johnny Darter WL

LD Longnose Dace WS

LG Lake Sturgeon XC

LH Lake Herring XG

LP Logperch XL

LS Longnose Sucker XM

LT Lake Trout XP

LW Lake Whitefish XS

XX Unidentified Pisces YB

YP Yellow Perch

Si Iver Redhorse
Central Mudminnow
Mottled Sculpin
Northern Pike
Ninespine Stickleback
Unidentified Pomox i s spp.
Fathead Minnow
Pumpk i nseed
Qui 1 Iback
Rainbow Trout
Round Whitefish
Smal 1 mouth Bass
Ra i nbow Sme 1 1
Spottai 1 Shiner
Shorthead Redhorse
SI imy Sculpin
Brook Si Iverside
Trout-perch
Unidentified Cottidae
Walleye
White Sucker

Unidentified Coregoninae
Unidentified Stickleback
Unidentified Lepomis spp.
Unidentified Cyprinidae
Damaged Larvae
Unidentified Catostomidae
Yel low Bui Ihead

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