ADULT AND JUVENILE FISH, ICHTHYOPLANKTON AND BENTHOS POPULATIONS IN THE VICINITY OF THE J. H. CAMPBELL POWER PLANT, EASTERN LAKE MICHIGAN, 1977 By D. J. Jude, B. A, Bachen, G. R. Heufelder, H. T. Tin, M. H. Winnell, F. J. Tesar, J. A. Dorr III Under contract with Consumers Power Company David J. Jude, Project Director Great Lakes Research, Division The University of Michigan Ann Arbor, Michigan 1978 November ACKNOWLEDGEMENTS This study was funded by a grant from Consumers Power Company (Jackson, Michigan) through their Environmental Services Department. We are indebted to Dr. John Z. Reynolds, Dr. Ibrahim H. Zeitoun and John Gulvas for their congenial treatment through all phases of contract negotiation and consummation. Nelson Navarre from the Great Lakes and Marine Waters Center was also very helpful during these phases. We would like to acknowledge the help and assistance that John Hartig, author on an earlier version of this report, provided us before his departure to another position. Sharon Klinger contributed to this report by writing drafts on the distribution of minor fish larvae and some on common adult fish. Laura Breen, in addition to coordinating the major task of figure production, also wrote a number of drafts concerning one major and some common adult fish species. Philip Schneeberger also contributed significantly to the final completion of this report by synthesizing and writing about a number of adult fish species and the larval fish total length-body depth relationship. Charles Madenjian compiled most of the statistical data for adult fish and wrote a draft of these results for this report . Paul Rago reviewed and edited the entire report, after rewriting many unruly sections. Our deep thanks for his perseverence is extended. Nancy Auer drew the awesome task of putting the final version of this report together, checking for errors and consistency, inserting figures and coordinating editing efforts. Special thanks are extended for her interest and concern. John Gulvas receives special thanks for help with plant personnel, in obtaining living facilities, help with setup and functioning of our on-site work area, scheduling and use of Consumers Power boats, ordering equipment and ironing out the many problems associated with the initial commencement of this project. John also assisted us in the field work in early phases of the study. Frank Hallman, construction foreman, is thanked for the many favors he did for us and Joe Azzerello is thanked for the frequent use of his aluminum boat to do work on Pigeon Lake. Metal and wood shop employees on the site were very cooperative in solving equipment problems as they arose; these workers deserve our gratitude. Herbert Norder provided us hospitality and access to our north Lake Michigan beach station through his property. Norman VanWagner, Roger Zimmerman and Bruce Rasher, all Consumers Power employees, are gratefully acknowledged for the contributions they made in assisting us with the field work. Great Lakes Research Division fisheries personnel, associated with another project, were pressed into service to help get the field work done before we were able to hire people specifically for this project. Nancy Thurber, in addition to helping with the field work, was 112. responsible for much of the equipment ordering and organizaton. Other fisheries personnel who helped with the field work despite other project commitments were: Bruce Pollard, Mary Ellen Fallon , Tim Miller, Bill Ziegler, Greg Godun, Larry Epskamp and Henry Tucker. Roger LaDronka, Kathy Zawacki, Melinda Bartholomae and Bill locum,, in similar situations, helped with benthos field trips . We would also like to thank our summertime assistants Jim Wojcik, Chuck Madenjian, Tom Rutecki, Dick Crone and Tom Zdeba. We are especially grateful to Dr. John Ayers and Dr. Erwin Seibel for granting us permission to use other project equipment without charge, without which we could not have completed this study. Sherry Stapleton and Judy Farris are thanked for their efficient handling of travel requests, requisitions and time cards. Sam Mozley guided us out of the endless quagmire of possiblities available for the benthos sampling design. Special thanks are extended to Jarl Hiltunen, who aided in the identification of some of the oligochaetes and to Dr. David White who identified Pigeon Lake Trichoptera and provided expert editing for benthos text. Cliff Tetzloff, Richard Thibault, Edward Dunster (captains of the R/V Mysis) and Earl Wilson are to be thanked for their dedication in tirelessly executing the long hours of day and night work off the R/V Mysis. We would like to thank Greg Godun for consultation on computing and statistical problems that arose; Ann Amundsen, for her outstanding and expeditious work in writing plot programs and obtaining computer-drawn graphs and figures used throughout most of this report, and George Te for his work in helping run many of the programs. Melanie Cunningham, Debbie Brooker, Ron Gamble, Nancy Auer and Cora Rubitschun served us through various phases of report preparation. Loren Flath, Sheryl Corey and David Waxman deserve accolades for the many excellent figures prepared for this report. Patty Braun and John Reutter together bore the brunt of our unceasing demands for getting endless tables and pages of text into typewritten form. We thank them for their enthusiasm and for caring about the quality of this report. Steve Schneider helped us meet publication deadlines. Jane Yeargain deserves a special thank you for the time and effort spent, in our behalf typing drafts and final copy, Our fish larvae sorters werei Jim Tetreault, Robert Tucker, Cora Rubitschun, Martin Vincent, Chuck Wyman, Sherry Middlemis, Loren Flath, Walter Rainboth, Henry Tucker and Tom Rutecki. We thank them for their patience, endurance and care in executing their sometimes tedious tasks * xv TABLE OF CONTENTS ACKNOWLEDGEMENTS - iii GENERAL INTRODUCTION . . '. . 1 STUDY AREA . . . 3 METHODS 8 Seining 3 Gillnetting 3 Trawling ". . . . 3 Additional and Missing Samples ........... 10 Mark and Recapture Study 11 Fish Larvae Tows 12 Sled Tows 16 Entrainment 20 Fish Larvae Processing 21 Fish Larvae Total Length-Body Depth Relationship 21 Laboratory Analysis of Juvenile and Adult Fish 22 Data Manipulations and Calculations . . 23 Definition of Terms 24 Benthos , 255 SCUBA Observations 30 RESULTS AND DISCUSSION ....... 33 Statistics ........ 33 Adult and Juvenile Fish 52 Major Species ............ 63 Alewife ....... 63 Rainbow Smelt 91 Spottail Shiner . 107 Yellow Perch 128 Golden Shiner 148 Bluntnose Minnow 154 Trout-perch 16C Largemouth Bass 177 Pumpkinseed 184 Common Species 190 Unidentified Coregonid ... 190 Johnny Darter 192 White Sucker 195 Lake Trout 197 Black Crappie 199 Bluegill 201 v Gizzard Shad 202 Rock Bass . . 205 Brook Silverside 207 Ninespine Stickleback . . . . . 209 Brown Bullhead . ... #. ..... . 211 Northern Pike .....' 213 Minor Species . . . . . . 215 Bowfin 215 Coho Salmon . . . . . 218 Tadpole Madtom 219 Slimy Sculpin ...... 220 Grass Pickerel . . . . 223 Brown Trout 224 Lake Chubsucker 226 Longnose Sucker . . * 227 Yellow Bullhead ........... 228 Carp . . . . 229 Black Bullhead ............ 231 Silver Redhorse ........•....•••. 231 Lake Whitefish . 232 Rainbow Trout . . 233 Round Whitefish 233 Channel Catfish ...••...•.•...... 234 Warmouth ......••.....•.•.•.. 234 Smallmouth Bass . . . . . . . . . . . . „ . . . . 235 Mottled Sculpin .... ............ . 235 Chinook Salmon ........ .... 236 Longnose Dace . . . . . . ........... . 237 Emerald Shiner ................. 237 Banded Killifish ........... 238 Goldfish .................... 238 DUi DUU eee.eeooooe.ceeoo.c*. fc, .J ^ Shorthead Redhorse ..... ......... . 239 Lake Sturgeon . ........... 239 Golden Redhorse . 239 Bigmouth Shiner ............ 239 Cisco ...................... 240 Blacknose Shiner ..•••••.... 240 Pirate Perch . ........... 240 Quillback ..... ......... 241 Creek Chub 241 Fathead Minnow ....... 241 Northern Hogsucker 241 Logperch . ......... .......... 241 White Crappie ...... . ... ....... . 242 wai.JLeye e........*©****.....© c^c* Gar 242 Chestnut Lamprey ......... 242 Sea Lamprey .................. • 242 VI Tiger Muskellunge 243 Freshwater Drum 243 iMark and Recapture Study 243 Fish Larvae and Entrainment Study 247 Alewife 248 Cyprinidae Complex 275 Spottail Shiner 277 Bluntnose Minnow > 295 Golden Shiner 297 Carp 298 • Emerald Shiner 305 Unknown Cyprinids 306 Yellow Perch 324 Centrarchidae Complex 333 Pumpkinseed 333 Green Sunfish ..... 334 Largemouth Bass 334 Smallmouth Bass 336 Rock Bass 337 Black Crappie . . 337 Unidentified Lepomis spp. 337 Unidentified Pomaxi? sp. 338 Unidentified Centrarchidae 341 Bluegill Fry 342 Rainbow Smelt 342 Johnny Darter ..... 347 Brook Silverside 349 Ninespine Stickleback 351 Slimy Sculpin 352 Fourhorn Sculpin 352 Trout-perch ........ 353 Unidentified Coregonidae .... 353 Unidentified Ictalurus sp 354 Tadpole Madtom Fry 354 Unknown Pisces 354 Damaged Larvae 354 Fish Larvae Total Length-Body Depth Relationship 361 Benthos . 372 Lake Michigan . . . 372 Community Structure . 372 Statistical Analysis 423 Pigeon Lake 451 VI 1 Western Basin . . . . . . . . . . . 452 Eastern Basin . . . ...... . . . . . . . . . 468 SCUBA Observations . . . . . . . . . . . . . . . . . . . . 475 GENERAL CONCLUSIONS . ... . . . . . . . . . . . . . . . . . . . 490 LITERATURE CITED ......................... 495 fi £ JET JLifi Ls.L.A>.. .«...*«». ceo»«cs ceo eeooo.ee 3 > 3 V1XX GENERAL INTRODUCTION Due to the recent proliferation of power plants on Lake Michigan, much concern has risen from ecologists and the general public as to possible effects of these plants on the indigenous biota. The present report , which presents fish and benthos monitoring data collected during May-December 1977 in the vicinity of the J. H. Campbell Plant (fossil fuel: 647 mw) located on Pigeon Lake near Port Sheldon, Michigan (Ottawa County), should provide necessary data to help answer these questions. The Campbell Plant is owned and operated by Consumers Power Company of Michigan and at present, has two generating units on line. The plant is being expanded to three units with a combined capacity of about 1,400 mw and will utilize an offshore intake and discharge structure in Lake Michigan for the third unit (Consumers Power Company 1975)* The primary purpose of this study was to gather background data on the indigenous fish and benthos populations in the vicinity of the J. H. Campbell Plant. These 1977 data will also establish baseline information against which postoperational (offshore intake and discharge of Unit 3) fisheries and benthos data can be compared.. The study was designed to answer a number of questions relating to the distribution of benthos and larval, juvenile and adult fish in the waterways potentially affected or to be affected by the once-through cooling mode of operation at Units 1, 2 and 3 of the Campbell Plant. For Units 1 and 2, water passes from Lake Michigan, through Pigeon Lake and then out to Lake Michigan again; Unit 3 will be cooled by water drawn directly from Lake Michigan through offshore intakes. We established two transects of stations in Lake Michigan. One, the north transect, was established to monitor possible effects in the area now affected by the thermal discharge of Units 1 and 2 as well as establishing baseline data so evaluation of the offshore intake and discharge systems (now under construction) can be made. The second transect served as a reference and was established south of the plant out of the influence of any present or projected thermal plume. Adult and larval fish data were collected at these transects on a regular basis. The benthos sampling program in Lake Michigan was a pilot study designed to establish the number of replicates (based upon sampling variability) required for the regular monitoring program, as well as some baseline data. In Pigeon Lake, stations were located in three distinct areas: Lake Michigan-influenced stations, those in adjacent, but undisturbed areas and those in the remote part of Pigeon Lake near Pigeon River. Stations were chosen in an attempt to establish the origin of entrained larvae, and whether or not Pigeon Lake acted as a spawning and nursery area. Stations were also established to determine if Lake Michigan species utilized the lake and to gain knowledge about the distribution of benthic organisms by habitat type. To ascertain relationships between fish larvae present in the various locations and those entrained, a station was set up in the intake canal* Entrainment samples were collected in the discharge canal using a plankton net which allowed us to establish the magnitude of larval fish losses under the following optimal conditions: little or no net avoidance was expected and only a short time was required to sample a large volume of water because of the high water velocity in the canal* A significant number of replicates (4) could be collected each diel period due to the short sampling time. Large volumes of water could more easily be filtered using a plankton net so pumps were not used in this study. To assess the likelihood of Lake Michigan being an important spawning area for fishes in the area of the Unit 3 intakes and discharges, SCUBA observations were also conducted in the area. A mark and recapture study of piscivores (largemouth bass, northern pike) was also conducted in order to estimate the numbers of these important sport fish in Pigeon Lake. These data can then be used to determine the impact impingement of these fish had on native fish stocks in Pigeon Lake. STUDY AREA The J. H. Campbell Power Plant is located on the eastern shore of Lake Michigan in Port Sheldon Township (T6N, R6W) Ottawa County, Michigan (Fig. 1). Land immediately surrounding 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 used primarily 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 nr/sec to Pigeon Lake (Water Resources Commission 1968) • The power plant water usage of 18.7 m /sec for cooling condensers causes the natural flow of Pigeon Lake into Lake Michigan to be directed through the plant. Lake Michigan water is thus used to supplement Pigeon Lake water which is then drawn into the plant and discharged (after being heated 9-10 C) by way of a canal approximately 1 km north of the entrance of Lake Michigan to Pigeon Lake. Two stone jetties (366 m long) were constructed at the entrance of Lake Michigan to Pigeon Lake to insure adequate flow of intake water to the plant. During winter months., this channel is kept from icing by recirculation of discharge water from the plant. Heated water is piped along the north jetty and released into the canal. The shoreline of Pigeon Lake reflects the general use of the lake as a recreational resource. A public access boat ramp maintained by the Michigan Department of Natural Resources (MDNR) , as well as privately-owned ramps and docks are used extensively during spring, summer and fall. Undoubtedly much of the navigational use of Pigeon Lake as a safe harbor (Port Sheldon) is due to its access to Lake Michigan. The depth of Pigeon Lake (0.3-1-2 m for more than one-third of its area) as well as its extensive aquatic vegetation precludes extensive use by all but shallow draft vessels. The deepest part of the lake, located in the western portion, is 7*5 m; there is a moderately deep channel (2.1-5.7 m) following the southern shoreline, which accomodates many docking facilities. Lake surveys conducted by MDNR as well as sporadic newspaper accounts indicate that Pigeon Lake is heavily fished in winter months with notable success. The river above Pigeon Lake also sustains a sport fishery. In October 1964, the river and its tributaries were treated to control sea lampreys. Stream surveys conducted by the MDNR in 1972 on Pigeon Creek (T7N,R16W) indicated a population of brown trout and some brook trout were present. Our sampling stations were established so netting was performed in all major habitat types. Two stations in the far eastern section of AR6A LOCATION MAP < o 8 Q m X O U- UJ Q 0 XXX) 2000 3000 4000 5000 CO cu •H U •H rH 44 0) M 42 O -P 44 T3 T3 cs O rH 42 03 A Pd H a « cd C rH P«* «% fa tH rH A 0) 53 42 a * s h4 cd u •0 SJ a u &3 44 •» o © cd « S * 42 a * a cd M 4J fa CO GO c •H o 4J •H C O Pigeon Lake were chosen because of their proximity to the entrance of the Pigeon River. Station Y (Fig. 2) is an openwater station approximately 1.8 m deep. Aquatic vegetation in this area was extremely dense in summer and autumn and bottom- type was composed of soft peat (Consumers Power Company 1975). Beach station T (Fig. 2) was of similar bottom and vegetation type. Depth at this station ranged from 0.3 to 1 m with large obstructions (logs, branches, etc.) common. The "undisturbed" part of Pigeon Lake was characterized by beach station V (and openwater station X). Vegetation density was notably less at these two stations when compared with stations Y and T, which had a similar bottom type. Openwater station (X) in this area ranged in depth from 1.2 to 2.1 m. Two additional stations (M and S) , influenced by inflowing Lake Michigan water were also located in Pigeon Lake. Openwater station M (Fig. 2) was approximately 7 m deep and lacked dense vegetation observed at other Pigeon Lake openwater stations. Beach station S (Fig. 2) had a fine-sand bottom and steep slope, which restricted the width of seinable shoreline. One openwater station was located in the intake canal (station Z - Fig. 2) which connects Pigeon Lake with the plant's present (Unit 1 and 2) cooling water system. This station was established to monitor fish larvae and eggs just before they are drawn into the power plant. The intake canal is approximately 670 m long and 21 m wide, .with a maximum depth of 3 mo Directly west of the plant is the shoreline of Lake Michigan. Again, this water resource finds extensive recreational and navigational use. Limited public entry to the Lake Michigan beach was possible through an access facility adjacent to the south side of the discharge canal . Fishing in the area of the discharge canal is popular throughout winter months due to attraction of fish to the discharge area. Swimming in the area of the discharge canal is prohibited due to unpredictable currents. Lake Michigan depth contours run roughly parallel to shore in the immediate area. Eight openwater stations were chosen at a sequence of increasing depth contours 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 the "normal" trends in fish distribution occurring in Lake Michigan. Stations A-H (south transect) ranged in depth from 1.5 m at station A to 21 m at station H, with intervening stations B-H separated by 3 m depth intervals. Of the three Lake Michigan beach stations established, one (station P - Fig. 1) was chosen in the vicinity of the south openwater transect V >1 o - c -3 6 0 * r^> •H *-» r^ 4J C ON ct5 ~> iH a o D &o r-4 -C C «J •H T3 ^ ,«•» pw a cd c T3 •v> c U Cd /-* a CGH cd •H tH pC * 04 a > •H rH S * rH X 01 0) ,Q & .* a CO > a >«3 cd #> CJ C3fl>3 G 0) •H « ^5 U UW CO 02 O S.*' 4=J tH C 0) cd 03 ^ £ iH C2 ce P"4 (aw. a rH C a) h a &Q *• cd c o cd s «H R e — » CD cd CO 03 (approximately 3.1 km south of the plant) to act as a reference station in the shoreline area* The two additional stations in the vicinity of the present 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) aided in monitoring the present thermal plume and its effect on shoreline fish movements. METHODS SEINING Seining was performed using a 0*6 cm (.25 in) mesh nylon seine, 15.2 m x 1.8 m (50 f t x 6 ft) including a 1.8 m (6 ft) bag. The seine was hauled parallel to shore for a distance of 61 m (200 ft)* Duplicate non- overlapping hauls were performed both day and night at all seining stations. Monthly seining was performed from June through November at three beach stations in Lake Michigan and three beach stations in Pigeon Lake (Table 1 and Figs. 1,2). In Lake Michigan 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. Pigeon Lake stations had very little current, and the direction of seining was northwest to southeast at station T, southwest to northeast at station V and north to south at station S. GILLNETTING Nylon experimental gill nets 36.6 ra x 1.8 m (120 ft x 6 ft) were set once a month for approximately 12 hrs during daylight and 12 hrs during the night. Each gill net was composed of 12 panels, with each panel starting at 1.3 cm (.5 in) bar mesh and proceeding in 0.6 cm (.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 in Lake Michigan and perpendicular, to shore in Pigeon Lake. In Lake Michigan, bottom gill nets were set at the 1.5, 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 present discharge channel (Table 1 and Fig. 1). Surface gill nets, which were identical to bottom gill nets except for additional floats, were set in Lake Michigan at the 6 m depth contour at the south transect and off the present discharge channel. In Pigeon Lake, bottom gill nets were set at openwater stations Y (1.5 ni) and M (6.0 m) (Table 1 and Fig. 2). TRAWLING . Bottom trawling was performed monthly from June through December in Lake Michigan using the University of Michigan's R/V Mysis. All trawls were made at an average speed of 4.8 km/hr (3 mph) . Duplicate 10»min hauls were performed at the 6, 9, 12, 15, 18 and 21 m depth contours on a transect 3.1 km south of the plant and at the 6 m depth contour TABLE 1. Proposed monthly sampling series for adult fish at selected stations in Pigeon Lake and Lake Michigan near the J. H. Campbell Power Plant, south of Grand Haven, Michigan, 1977. Maximum Beach Surface Bottom Bottom Station Depth (m) Seining Gillnetting Gillnetting Trawling Pigeon Lake M 6.0 X S 1.5 X T 1.5 X V 1.5 X Y 1.5 X Lake Michigan A 1.5 B 3.0 C 6.0 D 9.0 S 12.0 F 15.0 G 18.0 H 21.0 L 6.0 P 1.5 X Q 1.5 X R 1.5 X X X X X X* X X* X X X X X X X X X X X = duplicate sampling (seines, gill nets or trawls! * = monthly sampling deleted after August a transect 3.1 km south of the plant and at the 6 m depth contour between the present discharge channel and the Pigeon Lake entrance to Lake Michigan (Table 1 and Fig. 1). Hauls were performed at 3 m at the south transect during periods of reduced wave height* Trawling was done once during the day and once at night at all stations except the 18 and 21 m stations where only day trawling was done* A semi-balloon nylon otter trawl having a 4.9 m (16 ft) headrope and a 5*8 m (19 ft) footrdpe 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 interliner was 0.63 cm (0.25 in) stretch 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 then trawling north to south. ADDITIONAL AND MISSING SAMPLES The proposed monthly sampling series for Pigeon Lake and Lake Michigan consisted of 28 trawl hauls, 24 duplicate gill net sets, 8 duplicate surface gill net sets and 12 beach seine hauls. While it was hoped that proposed series fishing could be performed every month , this was not always possible due to equipment failure and inclement weather. Following is a summary of samples missing from the proposed monthly sampling series in 1977 (number .of missing observations in parentheses) i 1. June - night bottom gill nets at A, B, C, D, E and L (12), night surface gill nets at C and L (4). 2. August - night surface gill nets at C and L (4). 3. October - day and night bottom gill nets at A, B, C, D, E and L (24), day and night surface gill nets at C and L (8). When feasible, additional samples beyond those of proposed monthly sampling were collected. Supplemental surface gill nets were set at 9 and 12 m stations along the south transect during the day in June and August and during both day and night in July. Supplemental day bottom gill nets were set in December at the 6 m stations on the south transect and off the present discharge canal. Also during December in Pigeon Lake, we set bottom gill nets at stations M and Y during the day and at station M at night. Additional trawling at the 3 m, south transect station was done during the day in August, September, and November. Supplemental trawling was also performed at the 3, 6 and 9 m stations on the south transect and at the 6 m station off the discharge canal in December. 10 MARK AND RECAPTURE STUDY To assess the population and relative loss due to impingement of game fish in Pigeon Lake a mark and recapture study was conducted* Species considered for the study included yellow perch, largemouth bass, smallmouth bass, northern pike, bluegill and black crappie. Since Pigeon Lake is an open system, a major factor in selecting species to study was to consider the amount of potential interchange between Lake Michigan and Pigeon Lake, Since fairly large numbers of yellow perch live in Pigeon Lake, too many would have to be marked to supply a good estimate; therefore this species was not studied* Migration of fish from or into Pigeon Lake would violate a basic assumption used in population estimates (Ricker 1975). The primary species employed in this mark and recapture study were northern pike, largemouth bass and smallmouth bass. From baseline survey work performed on Pigeon Lake b3^ our research group, it was determined that bluegill and black crappie were present in fairly low numbers and thus could not be adequately assessed. Grass pickerel were marked because they were inadvertently collected along with northern pike. An electrofishing boat (Coffelt Electronics Company Inc. -Model VVP-15) was used to collect most fish in the study. The generator was designed to deliver 300 V pulsating DC current to minimize the number of deaths due to shocking. Stunned fish were brought aboard by dip net and held in a live-well for recovery. Other gear used to capture fish were gill nets and seines. Fish from gill nets that were judged to be in good condition (i.e. able to swim away) were marked and released. Some fish from seines were also tagged and released. Fish taken by seine and gill net were included in the catch of that period along with the electrofishing catch. Northern pike greater than 299 mm total length and largemouth bass greater than 219 mm total length were tagged with spaghetti tags. The smaller northern pike and largemouth bass, along with all grass pickerel and smallmouth bass, were fin clipped using a different pelvic or pectoral fin for each period. Spaghetti tags (Floy Tag & Manufacturing, 4616 Union Bay Place Northeast, Seattle, Washington 98105) were individually numbered and contained the address of the Consumers Power Company in Jackson, Michigan. Tags were inserted in the epaxial muscle below the dorsal fin. Fish were marked during four periods between 21 September 1977 and 3 November 1977* These periods ranged from 2-4 days long. Most . shocking was done at night because of higher catch-per-unit-effort . Each trip lasted 4-9 hrs. Shallow areas (less than 1 m) of Pigeon Lake were thoroughly covered during the first two periods. From this experience it was learned where pike and bass were commonly found in the lake. These areas were covered during electrofishing from then on and no effort was expended in areas containing few or no pike and bass. Areas which contained high concentrations of fish varied from one 11 collection period to the next and were heavily fished when encountered* Because Pigeon Lake gradually narrows at its upstream end to become Pigeon River and the distinction is by no means exact, an arbitrary upper boundary was designated (Fig, 3). Fish may have moved in and out of the area designated as Pigeon Lake into the Pigeon River or vice versa, but this effect was assumed to be minimal. Pigeon Lake was divided into nine areas depicted in Fig. 3* When fish were tagged the species, length, weight and area of capture were noted. Recaptured fish were examined for tag number and this information recorded with the area of capture. To assess angling mortalities, a collection box was established at the MDNR launching area to recover tags in fish caught by fishermen. No tags were found in the box, but the box had been vandalized . Observations made during the study period in the Pigeon Lake area indicated no fishing success among the few fishermen seen. Thus, it was assumed that fishing mortality was low enough to satisfy assumptions necessary to make a population estimate (Ricker 1975). FISH LARVAE TOWS Fish larvae, arbitrarily defined as any fish less than 2.54 cm total length, were collected using a 0.5 m diameter,, nylon plankton net of No. 2 mesh (351 micron aperture). Larvae were sampled in Pigeon Lake, Lake Michigan and the intake canal of the Campbell Plant. Entrainment samples were taken from the discharge canal of the Campbell Plant. 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 determined volume of water sampled. When flowmeters were not available or stopp'ed functioning, average flowmeter values were computed from readings available from the same station at other times or from stations of comparable depth. Suspect flowmeter readings were deleted when accuracy was questionable. Out of 1,084 fish larvae samples collected in 1977, 162 either had no flowmeter readings or readings were suspect and required the computation and insertion of an average flowmeter reading. Many of the suspect or lost readings were from beach tows collected in Pigeon Lake. These stations were choked with aquatic macrophytes during most of the summer making net towing without fouling by plants extremely difficult. Missing flow meter readings fell into three broad classes. The first class consisted of Pigeon Lake samples in which the flowmeter became clogged. The second class consisted of Lake Michigan samples for which no flowmeter was available. The third class consisted of duplicate tows for which no flowmeter was available for one of the two nets; however a meter was available for. the other replicate. Missing readings for these classes were handled as follows: 12 13 (1) Class I: A grand average of flowmeter readings observed during early summer and late fall sampling in Pigeon Lake was substituted for the inaccurate flow meter readings. (2) Classes II and III: A grand average of flowmeter readings taken over all months from Lake Michigan stations and openwater stations in Pigeon Lake was substituted for the missing flowmeter reading . All meter revolutions were converted to volume filtered by letting 1 revolution = 15 liters. Duplicate surface tow samples were collected at the seining stations in Lake Michigan (P, Q and R - Fig. 1) and Pigeon Lake (S, T and V - Fig. 2). Three people simultaneously hand-towed two nets for a distance of approximately 61 m (200 ft) once during the day and once at night. Beach tows were performed twice in June, three times 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 the remaining three stations in Pigeon Lake (Mf X and Y) , 13 stations in Lake Michigan (A, B, C, D, E, F, G, H, I, J, L, N and 0) and one station (Z) in the intake canal (see Table 2 for actual depths sampled at each station). Sampling at stations I, J, N and 0 was initiated on 13 July. Openwater fish larvae samples were collected from these selected stations in Lake Michigan during day and night twice in June, three times in July and once in August and September. One surface tow was collected at station L in December. Additional Lake Michigan samples were collected on 13 July by Consumers Power personnel at north beach station R (n. discharge) as well as north transect stations I (1.5 m - n) to 0 (12 m - n) . Samples taken at this time however, were taken at different depth intervals than our standard sampling (Appendix 7). Openwater tows were collected from selected stations in Pigeon Lake twice in June, three times in July and once in August, September, October, November and December. Equipment failure and inclement weather occasionally prevented completion of this sampling schedule. Missing samples included day and night tows at station X between 7-10 July and night tows at stations G and H between 19-23 September. Larvae tows from • Pigeon Lake and the intake canal were collected, from a 6 m long outboard motor boat. Openwater fish larvae tows in Lake Michigan were collected from the University of Michigan's R/V Mysis as follows : 1) plankton net with attached mason jar and depressor lowered to desired depth (average ship speed: 3-6 kph or 2-4 mph) Ik !° U cd CD C P Cd bO •H .G O CD cd cd on rH (D ^ •> cd p i-q cd G «H O .C CD O ft •H P CD en > G cd O K •P cd •P 03 *0 c cd Ih CD CD ft •P O O CD ,C H -P CD 3 03 O a — o !h P ft O --d a r-4 H cd r-\ H CD 43 ft 03 g ft o CD •P c cd bO O •H CD cd CD cd o CD b0 •H ft O ft w E>3 >H LA d o en O o CN O H H o CM r- i LA d LA CM LA LA o LA 00 o ON LA C o cm c LA LA O VO* LA LA o d OJ 00 LA LA d H LA Q o LA o d c LA H o CD CM O H CM LA d O ON O H O H O CO* H LA d LA -3- LA CO LA rH O H O LA H LA, d o on c O ON O H H O CM H LA d LA LA LA LA CO O ON LA d o CM o LA • LA O LA LA o d cm on LA LA O H LA LA • c o CM LA • o LA LA • • o CM LA • c 03 4^> p ft O CD Q *P cd £ ^> O CQ Eh o on o CM o vo LA e H 03 -P ft CD Q a p a •H cd S 15 2) plankton net towed horizontally for 5 min starting at the desired depth which was obtained by measuring wire angle and geometrically calculating the amount of cable to be released to reach desired depth 3) plankton net hauled to surface and washed using a hose from the Mysis 4) contents rinsed into the wide-mouth glass (0*47 liter) mason jar, formalinized (40 ml buffered formalin), 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 Figure 4. The method consists of sequential subtraction of larvae from lower water depth levels based upon concentrations 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 from calculations of total larvae present* We assumed that contamination occurring while the net was being lowered was negligible . The effects of differential vertical distribution due to larvae size was mitigated be stratifying each sample into 0-5 mm length intervals . A total of 51 length intervals were defined for fish larvae. Vertical net hauls, conducted in a 2.6 m deep swimming pool, were used to estimate the volume of water filtered per meter of vertical tow. Mean volume filtered was 0*48 m3 (28 ± 0*52 S,E<> revolutions) yielding a correction factor of 0.18 m water filtered/m of vertical haul* An example of this adjustment procedure is presented in Table 3« SLED TOWS Bottom tows were performed with a benthic fish larvae sled equipped with a flowmeter (Fig. 5). A single 5 min sled tow was performed once during the day and • once at night at all stations in Lake Michigan when time and weather permitted. Day and night sled tows were conducted at priority stations (those permitted). Day and night sled tows were conducted at priority stations (those closest to the present discharge) in July and September. Only day sled tows were performed at these stations in August and October. 16 ST It ATA 1 • ' T, — -1 *t Tj, STHAT/. 3 «4 T3 STCAT A 4 T4 *» STRATA k .4 / V CALCULATION PROCEDURE: 1. Convert current meter reading to volume filtered (V.) 2. Stratify total larval (T.) catch for each sample depth interval, into n 0.5 mm length intervals denoted by N. n Thus, T. - Z N. m=l 3. Calculate average concentration of larvae of length class m in the first stratum for all m. Thus, C. - (N. /V,) 1000 l,m l,m 1 4. Begin interative calculation of adjusted average concentrations of larvae for each depth stratum where i-1 i,m 1000[N. - trc (0.18(Z d. C. )/1000)] i,m 1 j j,m 'J i-F V. - 0.18 Z d, J-l J a if a > 0 0 otherwise rtical dep D » total depth of water column where d = vertical depth of water in the i-th water stratum 5 Z d± i-1 T. = total uncorrected catch of larvae in the i-th water stratum. N. = total uncorrected catch of larvae of the m~th size 9 class caught in the i-th water stratum. V. = estimates volume of water filtered by net towed in stratum i. (0.18) = correction factor expressed in terms of volume of water filter per meter of vertical tow. i.e. units H20m - H20m trc(-) * function which truncates argument to nearest non-negative integer number. Ci - adjusted average concentration of larvae of the m-th * length class in the j-th depth stratum. FIG. 4. Schematic representation of adjustment calculations for upper level contamination in larvae samples. Blocks represent varying quantities of water filtered in 5 different water strata. 17 CD > Q) H U o Q) »H a, cd a a a •H > rH .C a s CD cd M 03 cd CD CO cd cu > 3 *-j rH cd cd rH > u cd o u 0) cd ^ Q M o a • CO © e 4-J u CD T3 ■u a) 03 «H 3 o 03 CJ CD o U •H 3 4J TJ •H CD c a •H o ^ iJN, n c * o a) g o y 3 3 - S3 O «H CJ z *v-/ cd > n g cd H! « rH °H Cd M-} 2- 3 O 4-1 4J a j-i x: < <3) 50 -2 3 g cd 3 CJ 5S 00 M c cu g CD -U h4 c M cd cd > rH u u cd cd ^ 3 h3 M-H u , 3 H a rH Cd < cd cj 4J o H rl-drs CD a) cdco B 4JH g 3 cd puw rH 5s S O cd -h > <+4 03 > o "O si cd CO ^ •H U *s cd c/3 g 33 "w' J2 £ -U /-N O O- g £h cd w Q vo co co co vo co m co vO CO CO CO v© CO CO CO vo co co co vO CO CO CO ^o co ro co ^O CO CO CO o o o o o o < 0) H3 C CO «H 0 CO 3 rH >n 0) no C g 0 » •H rH O < g 4J 4J 3 CJ «H CD CD • CO CS rH *C CO *J CO CD g -U •H ^S M O 4J ^ -O O Cfl CO CD -U CO rH 4-J C rH c »h a rH 3 co o oc cd co g c .a M 'H H CD CD £ S M CD 0 cd a m h -o 3 a c CO «H 4J M cj a >, T? cu u ,c cd rH C > HT3 O O ra C u g CO CO CD CD CO U CO 4J CD 6 m) . Fish larvae - any larval fish less than or equal to 25-4 mm in total length. Fry - any fish greater than 25*4 mm in total length caught in plankton nets. Fish were usually 25-100 mm. Inshore - refers to that area of water between the shoreline and 21 m. Larval fish length intervals - for length-frequency histograms for larval fish, a specimen was assigned to 0.5 mm intervals based on total length. For example larvae 0.3 aim would be assigned to the interval 0.5 mm, one 5.6 mm would be assigned to the interval 5-6-6.0 mm. Littoral zone - the portion of the lake from the shoreline to the deepest extent of rooted aquatic macrophytes (0-4 m) . Nearshore - refers to that area of water less than or equal to 3*0 m* Offshore - another term for that area of water, not beach zone, 21 m deep or greater. 2U Openwater - refers to that area of water which is not beach zone and includes all stations 1.5 m and deeper which were usually sampled by boat and which usually had no or very few aquatic macrophytes present. Sublittoral zone - the portion of the lake from the deepest extent of the rooted aquatic macrophytes to the regular occurrence of mud deposits (4-6 m) . 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. BENTHOS Benthic samples were collected in Lake Michigan near the J. H. Campbell Plant on 4-5 June 1977* Seven transects parallel to shore in each of three 1.6 km (1.0 mile wide) regions (north, middle and south) were established in Lake Michigan in the vicinity of the Campbell Plant (Fig. 6). The middle region was centered on the present discharge channel and extended south and north a distance of 0.8 km (0.5 mile) from that point. The north and south regions were centered on a distance of 4.8 km (3-0 miles) from the discharge channel* These regions extended 0.8 km (0.5 mile) north and south of their central axis, Each transect (Fig. 6) was sampled ten times at evenly spaced intervals 0.18 km (0.11 mile) apart. Parallel transects were established at the following depth contours: 3, 6, 9? 12, 15, 20 and 25 m (10, 20, 30, 39? 49, 66 and 82 ft). Transects extended to a maximum of 4.3 km (2.7 miles) offshore into Lake Michigan. Seventy samples were taken in each region, while in all, 210 samples were taken in the survey area in June 1977. An additional 105 samples per month were taken in August and October 1977. Five replicates were taken at the center of each depth zone in each region. Data for August and October can be found in Appendices 12,13* Samples were collected using a triplex Ponar grab sampler (Mozley and Chapelsky 1973)* Only one chamber of the Ponar (one-third Ponar) was used for a given sample. Once collected, samples were washed through a 0.35 mm mesh net. The concentrated samples were preserved with 456 formalin and returned to the Great Lakes Research Division laboratory for sorting and identification. Sorting and identification of organisms were performed using a dissecting scope. Specimens unidentifiable at the genus/species level in the initial sorting (Chironomidae, Naididae and Tubificidae) were 25 0) c -• •H /-\ O u H o G CO CO CO s a CO a M •H 4-» •c u il C 0) H ,a N—> j-» f^» o P** <4-{ as iH fl o U H 0) J3 ■M U CO 0) CD N—4 CO u. ^ 28 Benthos samples were collected with a modified Wildco Ponar grab sampler, modified so that the side plates extended up to the central axis that rotates the jaws for cocking and closing. Extension of the side plates prevented loss of material. Upon collection, samples were washed through a 0.35 mm mesh net. The portion retained in the net was stored in 1 quart mason jars and preserved in 4$ buffered formalin solution. Samples were returned to the Great Lakes Research Division laboratory in Ann Arbor, Michigan for sorting and identification. Two methods of sorting were employed. Sugar flotation was used in sorting samples from the following stations with their designated replicates in parentheses: PLX1 (A-C), PLX3 (B), PL52 (A-C) and PL53 (A-C). In the ten samples floated using the sugar solution it was necessary to pick the entire sample residue since it was found that about 6-20? of the total animals present in a sample would not float . As a result, the remaining 29 samples were subsampled when necessary. In the remaining samples a 1/2-1/32 subsampled portion was extracted from the whole sample. The only exception to this procedure was PLX2 (A-C) where subsampling was not necessary. The entire contents of the subsample were then picked under a dissecting microscope. Because aquatic macrophytes were present in nearly all remaining samples in tangled, clumped masses, subsampling had to be modified from standard techniques. Since aquatic macrophytes could not be effectively subsampled, they were washed and removed from the whole sample before subsampling. The remaining sample residue was then subsampled to an appropriate volume using a Folsom plankton splitter. In order to determine the number of organisms /grab, numbers of animals occurring in the subsampled portion were multiplied by the appropriate inverse of the subsample fraction which ranged from 2-32. Organisms occurring in the macrophytes were sorted separately from the subsample fraction. The number of organisms found in the macrophytes after identification was added to the appropriate taxon in the subsampled portion. Therefore, the number of animals per grab was the addition for any taxon of 1 . ) the subsample fraction total multiplied by the inverse of the subsample; plus 2.) the number occurring in the macrophyte portion of the sample. Number of organisms per square meter was obtained by multiplying the number of animals in a taxom in a grab by 19 • 9-4 - Due to the large number of tubificids present in some samples, tubificid species determination required subsampling. When the number of tubificids exceeded 200 in a sample, a subsample of tubificids was extracted from the whole. Tubificids were placed in a gridded pan and evenly distributed. From a table of random numbers individual squares were selected. Tubificids occurring in the selected square were mounted for identification. This process was repeated until 100 tubificids were mounted. The number for each tubificid species in the sample were 29 estimated by multiplying each subsampled tubificid species total by the ratio of the total number of tubificids present in the sample divided by the total number of tubificids present in the subsample. SCUBA OBSERVATIONS During 9-10 August 1 977 9 daylight underwater observations were made in the vicinity of the J. Ho Campbell Plant using SCUBA. A 6 m Boston Whaler served as the support vessel* Seven transects (referred to as dive no. 1-7) were swum during this period (Fig. 8). Photographs were taken periodically at various stations along each transect and a description of physical and biological characteristics of the bottom were recorded on a slate. These observations were later transcribed. Two transects (dive no. 1 and 3) were swum perpendicular to shore between the 6 and 12 m depth contour (Fig. 6). 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 400 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 the 6 m contour, a distance of approximately 800 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 (dive 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. Station locations along each transect were selected according to a loosely systematic design with approximately 5 min of swimming time between stations allotted. However, if an unusual feature was noted observations at that station were taken. Station observations were generally subdivided into the following categories; description of bottom type, presence of organic detritus and biological notes. General between-station observations during swims were also recorded. One diver took photographs, the other diver made and recorded observations. Since visual observations tend to be subjective, the following terms used in this report are defined: few = 1-10, many = 11-50, numerous = 51-100 and abundant = more than 100. Bottom composition was described by one of three relative categories : fine sand, medium sand and coarse sand. "Organic detritus" refers to fragmented pieces of terrestrial vegetation and aquatic debris (dead phytoplankton, mollusc shells, etc). "Floe" refers to the loose 30 -P 0 V -P SO •H O .-3 ON -P CO b£> fcifl C 3 •H J3 0-3 -P c cd 0. H ft O I i? ca U o Ph o -p s o ffi -p o O O ■C -P P -H C '4H O o g f« o 4J -p (5 g 3 9 a co CO -p • a 0 CO cj *H •p GO CD 31 accumulation of fine particulate material (consisting primarily of sediment, some periphyton and diatomaceous material) « Diving observations, which are macroscopic in nature, were limited primarily to demersal organisms and did not include organisms living within the sediment* In addition to the above observations, the boat tender recorded water temperature, transparency (secchi disc), and wave and weather conditions at each station. 32 RESULTS AND DISCUSSION STATISTICS Introduction Fish populations were sampled using replicate trawls and gill nets at each sampling location and time* All statistical analyses were based upon abundance indices since quantitative estimates of abundance are not possible given the gear employed in this study * Catch per unit effort (CPE) is defined as the total catch in numbers per unit of standard fishing effort. Each sample represented one unit of effort* One unit of trawling effort was defined as a 10 min tow, and one unit of gill net effort was defined as one lift of the net adjusted to a standard 12 hr fishing period. Abundance indices for different gear types are not directly comparable due to different biases of each gear type* The unknown relationships among CPE values derived from different gear require independent analyses of each data set* However, the different gear types provide overlapping and complementary information about fish populations. For example, individual fish which might avoid trawls might be caught by gill nets* Conversely, fish which are too small to be captured in gill nets are likely caught by seines and trawls. Consequently, one must envision the pattern presented by the aggregate of gear types when statistically analyzing the results for each gear* Design and Analysis Considerations Statistical analyses were performed for each of the five most abundant species of fish in the field sampling: spottail shiners, alewife, rainbow smelt, yellow perch and trout-perch* Differences in fish abundance between the control and experimental stations were examined using analysis of variance (ANOVA). The experimental designs outlined in the methods section were analyzed as completely crossed factorial models with MONTH, STATION and/or TIME OF DAY as design variables* All factors were considered fixed* The response variable was either number of fish per unit effort or a transform thereof. We transformed raw data by taking the natural logarithm of CPE plus one. The addition of one insured nonnegativity in transformed data* This transform is designed to reduce the variances of data so that the ANOVA assumptions might be more closely met* The factorial ANOVA models were modified according to species, gear type and presence of zero data* A summary of the models analyzed is given in Table 4* All models included the design variables MONTH and STATION * The MONTH factor was expected to explain a considerable amount of variation attributable to seasonal changes in abundance of inshore 33 U I ■^ 03 -^ o < JN S H CD Sh > a) •H XI «4-l s OJ 0) a x: l cd rH rH cd P* c cd H iH 0 a) u XI cu T> e > O o rH a) o-x: & 4J a) MH 03 o CS 00 >> •H 4J 03 •H a) C T3 •H a rH •H Cd > AJ cs 0) 0) XS a 4J •H M cs * $H 03 cd CD •H g a d CD Cfl a. 03 • u j cs « 3 H cd t3 o c a e 03 as a> x CO w G 03 o u 03 U o o cd O CD 1-3 0) C •H X co CO •H 03 J* <3 U4 O U «H J3 W 5 C O 0) «H 0*«H C3 a x 6 u i 3 U O 3 «-H O rH Vt 03 CO < « H >« CO 25 S 6 u NO vO 03 «W *»• X a a »4 4 K9 OS Xk s o & >* U-j 3 O «< Q) •-3 ^ Q M I O «-3 J2 O 01 (^ 01 ^ o CD «H 01 f~4 CX 6 cd 09 00 f-i cs *•• *v >% 01 iH £4 C >% O iH ca 03 c CD cd r-4 Oe » m & CD «» u U 0) 03 ^3 3 S 3 > CO 25 i ! B S O *3 I O o u & «k u •o CD CD 2 N >% to • *H CD 01 cd •H *H e a ^3 cd 0) crj flU*H CD 03 M ^s cd CJ) j- > 2 CD J3 N 03 4J »-« oc «H »M «H 2 o ^s 01 rH 03 «T3 cd CD £ x cd >* o ^ •H u ^ g d o O U e-8 r-4 U 3 0) M g JS 0) CB • 0) s u JS oj » CJ * 03 r-«. > >< *W 3 O < 01 a 03 03 14 03 03 03 >s CD > J3 rH H-H 4Jtf a ^ o oo s % 03 CS XH 0) d 00 CS J3 •H. O U 5 (3 U O » d h e* ^3 Q >^ 03 O eH N O CS >% • w O iH "O CS 03 0) 03 C N M C3 c^ >» 0) rH «H ^ o C* U Cd 01 S O C3 C8 rH a c cd a A 03 «H cd 03 03 a •H >» M M 03 U C3 03 03 Qs <8 > § fe 25 O O M H CO «» $-1 s~s^ u 03 CO 25 03 •° 1 L 3 a a a 3 vo \o 00 3 > WW < O s a o >* « CO «© r-J U 03 03 3 a u to »-J & G U §25 CD «u oi a C a.<*4 as 3 03 03 -H »-3 w k-d 1 H CO 09 o Cd rH CQ <*4 rH W U *H 03 5OS5 3U fish populations. The STATION factor is supposed to account for differences between the control station C (6 m - s.) and the discharge station L (6 m - n.). TIME-OF-DAY was employed as a design factor for three of the five models examined- This factor was intended to account for diel migrations into and out of the study area. All statistical tests for significance of main effects and interactions were conducted at the 99$ probability (« = 0.01) level. Assumptions for the ANOVA model are: 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 ANOVAs are robust to the assumptions of normality and homogeneous variances. In other words, moderate departures from these assumptions do not invalidate results of the model. Violation of the independence assumption may have more serious consequences. Given that these assumptions are met, sensitivity of the ANOVA model to detect the alternate hypothesis can be calculated. In this study we are interested in detecting significant differences between stations. The least detectable true change (LDTC) is the minimum difference in mean abundance levels between stations that can be detected by our experimental design. The formula for LDTC, as presented by Jude et al. (1975) 6 = s(2/n)1/2(tttjV + t2(.,_p)5v) where: 6 = least detectable true change 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 = significance level t = student's t statistic v = degrees of freedom P = power (the probability that a true difference will be judged significant by ANOVA) . Methods BMD8V was used to perform the analyses of variance (Statistical Research Laboratory 1975). 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 the actual data value, can be examined to determine how well the ANOVA model meets its assumptions (Draper and Smith 1966). An ALGOL program was written to compute the LDTCs. 35 TABLE 5* Descriptive statistics used for analyses of variance for sample data collected at stations C (6 m - s«) and L (6 m - n.) near the J. H. Campbell Plant, eastern Lake Michigan, June - December 1977. Sample data are number of fish* Gear N Maximum X Standard Deviation Percentage of Zero Catch Data TRAWL (Jun - Dec) Spottail shiner 56 Alewife 56 Rainbow smelt 56 Trout-perch 56 Yellow perch 56 46 683 698 29 22 5.1 56.2 71.8 4.3 1.9 9.3 133.9 120.1 7.2 3.7 44,6 33.9 7.1 51.8 44.6 BOTTOM GILL NET (Jul, Aug, Sep, Nov) Spottail shiner 32 Alewife 32 Yellow perch 32 17 2.5 4.3 59.4 195 12.0 39.5 56.3 21 4.8 5.5 25.0 BOTTOM GILL NET (Jul-Sep, Nov, Dec) Alewife 24 195 15.3 45.1 58.3 Yellow perch 24 21 3.5 6.0 62.5 SURFACE GILL NET (Jul, Sep, Nov) Alewife 24 71 17.0 21.8 37.5 SURFACE GILL NET (Jun, Sep, Nov) Alewife 20 195 19.0 45.4 55.0 All AN0VA models listed in Table 4 were computed using both raw and log transformed data. Data for all species and gear types were initially screened by calculating mean catch, its variance and percentage of zeroes in the design matrix* Summary statistics for those data sets considered amenable to further statistical analyses are presented in Table 5* Note that the percentage of zero catches for these data usually exceeded 35?. Consequently distribution of values was generally bimodal with modes at zero and near the geometric mean* The transformation did however yield residuals which were slightly 36 closer to meeting ANOVA assumptions than residuals from raw data values. Unless stated otherwise, future references to abundances in this section will refer to geometric mean abundance derived from log transformed data. Geometric means for various partitions of the data are derived by back transforming cell means from log transformed data. For example if x represents the mean catch for log transformed data, then xf = e 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 of the original data. If so, the geometric means will also differ in ranking order since the exponential function is monotonic. The least detectable true change is modified whenever log transformed data are used. LDTC or 5 is expressed as the change in the logarithm of fish numbers and not in terms of the actual numbers of fish. Back transforming 5 yields e5 which represents the ratio of the mean number of fish per unit effort plus one for control station C as compared with experimental station L. In the transformed coordinate system (i.e. log transformed system) changes will be detectable if "C x. j > d where xp and x. refer to the log transformed mean catches a stations C and L respectively. When we return to the original coordinate system differences are detectable whenever: -0 L 5 e > — > e Results Results for analyses of variance trawl data are summarized in Table 6. Month effects were significant and station effects were insignificant for spottail shiners, rainbow smelt and trout-perch but not for alewife or yellow perch- Night catches generally exceeded day catches for these species. Significance of a particular factor is confounded whenever that factor enters into a significant interaction term. In these cases, the main factor must be interpreted in relation to all significant interactions involving that factor. Geometric mean abundance is plotted against month for each species in Figure 9. Spottail shiner abundance was high in June, October and December and low in July and August . Alewives were most abundant in October when young-of-the-year were recruited into trawl catches. Peak catches of rainbow smelt in August and September were also related to recruitment of YOY. Trout-perch abundance peaked in July and then declined through December. The geometric mean abundance of yellow perch was greatest in August. 37 o CO es 3 o O SH °H *-i o U rC mh CO 4J -5 •H i Sh CO m i j CO rH a > S CO co 60 M-4 u •H O u 42 a • CO a •H fH eu •H S O CO • >> 4J 0) iH X 4*S i! CO 60 CO <2 3 h3 8 CO CO a C •U y-i *h CO o 43 a) a 4J u >> u CO C j-j 0) co CO CO a* ! cu O g •U « 25 O 4J H «« H « W CO >» www 25 ooon ooco o o m rH O CM WWW 25 25 cm m en QOOcn m H •W »-J (3 a 00 s •H W W 3: o • co u 23 cfl 2 fa c CO W s « 3 ■U fa I p Cg u* w •H 25 d H4 CO 32 •H W W H M < U £-» CTJ H U O W fa w fe w s bi o W Ck Q CJ a 25 O CJ H csi < 3 b H o o « w -< > www 25 rH CM 00 ON OS CI ^ o o www 25 25 CO CO CM vO O O w W W 25 rH vO O vO »H CO »H 00 o\ w w w w 25 25 25 Hi^HO w w w w 25 25 25 25 cm m m cm O O CM v^ fH CM CO iH w w w w 25 25 25 25 m co o cm m in p*» rv. O CM O O w w w w 25 25 25 25 m- v© CM cu y •H \o 4J 5 >-• a, u cd a) cq r-» J en as u *d « e a c •U CQ CO CQ cq a M 3 -H CD /—s 00 4-4 c « 3 -H •H CO > CQ rH rH •H vO 3 4J 03 %«• p-3 O 4J PS +J a a o a ii a CO CQ 03 c 00 CO 0 •H 25 M •H ^S O 4J CJ * 4-4 CQ •H iH 4-J S o 0) CQ a CD G 4J ^ II CQ CQ CQ •H •J a M CO CO 4J cs -w > CD JU CQ £ CD 4-! -U 4J O rH CO C rH CQ CQ CO •H cu a CD 00 •H CO * m >, a 4-J -H rH o a c CQ u CQ 00 c u rH «H cd o PU CO 4-4 rH II =o c H •H CD CO >% •o U 4J a CQ ^2 a • £j 00 cq r^» g 3 O r** 3 CQ ON CO a * rH SB pC U 0 CJ • cu M •-3 ^ • CO a p^ a CU CD X > $ U Q LxJ o 25 -J rH H CD rH cQ T3 >^ CS CQ 32 c a 00 ctf •H w CO Pw 5s • o u pj CQ >H 4J to co >* 4-4 •H £ 00 w •H to CO M (J 4J m ir> a\ vO ON CM CM CO CO CO CO !25 CO ON CN H CO H CO vO Mooom CO CO CO 25 25 h oo s H ^ k2 £3 \ / \ / \ / \ / \ / «, --— NIGHT JUL AUG SEP OCT NOV MONTHS FIG* 14* Geometric mean number (plus one) of spottail shiners caught in bottom gill nets at stations C (6 m - s«) and L (6 m - n.) near the J. EL Campbell Plant, eastern Lake Michigan, July, August, September and November 1977. Month - time interaction for spottail shiners. reflection on the adequacy of the experimental design, but rather indicates the high variable abundance of alewives within the inshore zone . Discussion Future judgements concerning the effect on fish of the current and/or proposed intake and discharge operations at the Campbell Plant must consider the limitations of the data assembled and analyzed herein. Many factors argue forcefully that any sampling program conducted in the inshore waters alone, regardless of intensity or duration, is necessarily more descriptive than comparative or predictive. The dynamic character of inshore fish populations, limited sampling technology, unknown effects of environmental variations and the strong link between spawners and recruits clearly suggest the difficulties associated with assessing the effects of a single factor (i.e. the power plant) on community structure and function. Furthermore, ongoing lakewide biological, chemical and physical processes are likely to supercede and mask potential effects due to operation of the Campbell Plant. For example, species introductions (both accidental and planned) have resulted in a nonequilibrium community structure in which relationships among populations are continually changing (Smith 1968). Similarly, chemical contaminants have altered food sources (e.g. benthos community) and possibly changed the reproductive behavior of some fish such as lake trout (Burdick et al. 1964).. Determining the role of the Campbell Plant, acting in U6 TABLE. 8. Summary of analyses of variance for alewives and yellow perch caught in bottom gill nets during the day only at stations C (6 m -s#) and L (6 m -n.) near the J. H. Campbell Plant, eastern Lake Michigan, June, July, August, September, November and December 1977. S = significant at * = .01, NS = not significant at « » .01. SOURCE DEGREES ALEWIFE YELLOW PERCH OF OF VARIATION FREEDOM F. Stat. Signif . F. Stat. Signif. Main Effects: Month (M) 5 15.98 S 92.65 S Station (S) 1 1.58 NS 56.77 S Interaction: MxS 5 4.58 NS 41.55 S Within Cell Error 12 concert with numerous other factors, upon the biota of Lake Michigan is a seemingly hopeless task. The ensuing paragraphs address some of these problems and suggest possible alternative analyses. The dynamic character of inshore fish populations refers not only to the seasonal use of the inshore zone for spawning and recruitment but also the population's ability to respond to imposed stressors. We know a priori that most species are not year-long residents in the inshore zone. Also, we know that some relation exists between the numbers of spawners and recruits observed. In addition, diel, vertical and horizontal movements are known for many species. These factors suggest that catch data might be more effectively modeled with time series techniques rather than analyses of variance. Murarka et al. (1976) have proposed the use of time series techniques for impact analysis which are based upon the methods of Box and Tiao (1965, 1975). Unfortunately, these methods require relatively large data sets extending over several years . For this study, we have less than 1 yr of data. In view of these constraints, interpretations of statistically significant main effects and interaction terms remain somewhat speculative and tenuous. However, in spite of the complexity and variability in the nearshore system several general patterns emerged. The significant effects due to month are undoubtedly related to the seasonal use of the inshore zone by adult fish for pre-spawning, k7 JUN YELLOW PERCH JUL AUG SEP OCT MONTHS -J- -L. NQV DEC ALEWIFE JUN JUL AUG SEP OCT MONTHS NOV DEC YELLOW PERCH - MONTH X STATION INTERACTION — — STATION C --— STATION L JUN JUL HUG SEP OCT MONTHS NOV OEC FIG, 15. Geometric mean number (plus one) of alewives and yellow perch caught in bottom gill nets at stations C (6 m - s.) and L (6 m - n.) near the J. H. Campbell Plant, eastern Lake Michigan, day only, July, August, September and November 1977. spawning and in some cases, post-spawning activitesc Subsequent recruitment of young-of-year fish is the other major factor underlying the seasonal effect, Diel differences resulted from three possible causes: 1) horizontal movements within or out of the sampling area, 2) vertical movements within the water column or 3) avoidance of fishing gear during daylight* Station differences may reflect habitat preferences but without corroborating evidence this is difficult to support. Interpretations of significant interations are even more difficult to analyze. kd TABLE 9. Summary of analysis of variance for alewives caught in surface gill nets at stations C (6 m - s.) and L (6 m - n.) near the J. H. Campbell Plant, eastern Lake Michigan, July, September and November 1977. S » significant at * = .01, NS = not significant at « = .01. SOURCE DEGREES ALEWIFE OF OF VARIATION FREEDOM F. Stat. Signif . Main Effects: Month (M) 2 14.32 S Station (S) 1 0.08 NS Time (T) 1 5.92 NS Interactions: MxS 2 0.36 NS MxT 2 2.11 NS SxT 1 0.09 NS MxSxT 2 0.03 NS Within Cell Error 12 TABLE 10. Summary of analysis of variance for alewives caught in surface gill nets during the day only at stations C (6 m - s.) and L (6 m - il) near the J. H. Campbell Plant, eastern Lake Michigan, June, July, August, September and November 1977. S - significant at * » .01, NS « not significant at « » .01. SOURCE DEGREES ALEWIFE OF OF VARIATION FREEDOM F. Stat. Signif. Main Effects: Month (M) 4 4.45 NS Station (S) 1 5.27 NS Interaction: MxS 4 3.72 NS Within Cell Error 10 49 12 r B - it V * N. s 10 X u \^ •~ 9 \ u \ H- • \ UJ \ 3 ? \ -J \ 2 8 \ m S \ as \ oe ii \ X \ X^^Nw o 3 \ / N. JE 8 \/ \ UJ V \ a o —J 1 1 1 « ' » JUN JUL bug sep MONTHS OCT NOV FIG* 16. Geometric mean number (plus one) of alewives caught in surface gill nets at stations C (6 m - s.) and L (6 m - iu) near the J. H. Campbell Plant, eastern Lake Michigan. A » July, September and November. B - June, July, August, September and November, day only. Statistically significant interaction terms are probably related to changing fish behavior over months (e.g. spatial movements related to temperature) and variable size class structures over time* Each species is considered a single- entity, however catch records over a year likely include spawning adults as well as recruited young -of -year . Since behavior, habitat preference, food habits etce change with age as well as size and time, significant interaction terms are highly probable. Moreover, the underlying mechanism(s) for these effects are unlikely to be attributed to a single factor. In summary, the analysis of variance models provide some insight into the biology of the species being investigated. ANOVA models should be regarded as an evolving working tool rather than as definitive answer to the questions of power-plant related impacts. Alternative analyses may be employed as additional data become available. Meeting the ANOVA assumptions of normality, homogeneous variances and particularly statistical independence remains the fundamental impediment to their applicability. To our knowledge, there have not been any systematic and unequivocal investigations of alternative analysis methods. Thomas (1977)i McCaughran (1977) and Murarka et ale (1976) have addressed these difficult problems but more work is needed. 50 u cd 3 •H T3 Xi 3 CO 03 •H • O co en «h i a o a e CO ! U a CO out? CO CO M a c o cox CO T3 3 3 CO 3 CO e cj u a o) V4 I co 3 4J <4H CO 4J O CO u-i X 0) 4J 0) 0) 3 cn o 3 CO cd a o > X o * • 4J »n CD rH 3 cd a) w 8 X 4J CO 4J o CD CO 3 4J «H cj CO , CD J-) CD * T3 CD CO £ vO CO CD w CD fH t-4 CO h4 W ►J PQ < 33 W frt 1 m on ^ <• cn m »H fH *H tH H o ON • H is en ON ^ cn cn cm s • • • S3 »n u on est w a. s o h-3 on U S ON ss o M ON 2 ON «< o ON 8 55 tO M ON 33 cn o CO o ON ON sO O vO -4" <■ >r n •^ » m cn fH NNM W co cn cn oo h» vo «n -I *»N CUTD 003303 O O O fH • • • c I fc TITO 003303 o^>n on oo h O m3 m -^ »^ oo «h o m >o CD O X 25 a CD T3 > 3 o CO S5 r» H M CD • CD ,n r^ X a r-. a CD ON CD 4J rH 4J a Cu CD CD cn M Cn • CD r- I X 1 r>. a ON CD CD CD rH 3 > s 3 O 3 ^ 25 «n cd a •2 a ^Q O G O a h CO M CD MH MH > u O CO CD CO 21 0) X CD X a x "d o CD a 3 4J 4-) u cO CO a. co a cd a u GQ CD >, >sX rH « rH a 3 *J 3 CD O • CO o 4J r^» 3 CU >, r>» 50 >s CD CO ON 3 cO cn T3 H ^ Q) M >n CD tH T3 CD fH T3 3 3 pQ 3 3 ►-) H 6 •-3 rH CJ CD a U 3 a U 3 O -H CD O -H m Q 4-4 CO CO CO 4J I CO CD CD a a a a rH o o CO CO £ U U 4-1 IW CO u u JU M U o o 3 3 Eh PQ PQ cn cn »h cn m -^ m 51 ADULT AND JUVENILE FISH This section contains adult and juvenile fish data from collections made during 1977 in the vicinity of the Campbell Plant. Due to the complexity of the systems, analyses of data from Lake Michigan and Pigeon Lake were presented separately* A systematic list of all species collected or sighted during this study (Table 12) showed that 49 species were recorded from Pigeon Lake; 31 were observed from Lake Michigan. Table 12 also includes common and scientific names organized by family, our designated species codes and in which lake each species was caught or observed. Sixty- four species of adult fish representing 21 families were collected from the study area. An overview of the catch in Lake Michigan is presented in Table 13. Species are ordered by total catch (all gear types combined) and individual species catches are segregated by month <> A similar presentation of Pigeon Lake data can be found in Table 14. Alewife was the most frequently captured fish, representing 68.5? numerically of all fish caught in Lake Michigan and 34 -3% of the total catch in Pigeon Lake. Species caught in specific gear types and their catch abundance in Lake Michigan (Tables 15-18) and Pigeon Lake (Tables 19-20) showed that seines were responsible for capturing the most fish in both environments. In Lake Michigan bottom gill nets and surface gill nets were responsible for the capture of 3252 and 844 fish respectively, trawls caught 30541 fish and as noted seine catches were highest with 43971. Alewives comprised numerically the highest percentage of the catch from all four gear types used in. Lake Michigan. For Pigeon Lake (Tables 19-20) only two gear types (bottom gill nets and seines) were employed. Seine ' samples contained 20206 fish of which 35*0? were alewives and 22.5? were spottails. Bottom gill nets only captured 465 fish; most caught (32.5?) were yellow perch followed by bowfin and northern pike (each 14.4?). For purposes of our analyses, a species was designated major if it represented more than 1? of the total catch for either lake,. Lake Michigan major species included alewife, rainbow smelt, spottail shiner, yellow perch and trout-perch. In Pigeon Lake, alewife, spottail shiner, golden shiner, yellow perch, bluntnose minnow, largemouth bass and pumpkinseed were considered major species. Remaining species in the catch for each lake were designated as common when 100 or more specimens were collected and minor if fewer than 100 were taken. Species were treated differently, depending on abundance in our samples. Discussions of major species included seasonal, spatial and diel distributions of various size and age groups. We attempted to 52 TABLE 12. Scientific name, common name and abbreviations for all species of fish captured from Campbell Plant study areas from June through December 1977. An X denotes presence in either Lake Michigan or Pigeon Lake. Names assigned according to Bailety et al. 1970. Pigeon Lake Scientific and Common Name Abbreviation Lake Michigan Acipenseridae Aoipenser fulvescens Raf inesque LG X Lake sturgeon Amiidae Amia oalva Linnaeus BF X Bowfin Aphredoderidae Aphredoderus say anus (Gilliams) PR X Pirate perch Atherinidae Labidesthes sioculus (Cope) SV X X Brook silverside Catostomidae Carpiodes ayprinus (Lesueur) Quillback Erimyzon sucetta (Lacepede) Lake chub sucker Catostomus aatostomus (Forster) LS X Longnose sucker Catostomus zorrmevsoni (Lacepede) WS X X White sucker Hypentelium nigricans (Lesueur) Northern hog sucker Moxostoma aniswpum (Rafinesque) MA X Silver redhorse Moxostoma macrolepidotum (Lesueur) SR X Shorthead redhorse Moxostoma erythrurum (Rafinesque) Golden redhorse Centrarchidae Ambloplites rupestris (Rafinesque) Rock bass Lepomis gibbosus (Linnaeus) Pumpkinseed Lepomis gulosus (Cuvier) Warmouth Lepomis macrochirus Rafinesque BG X X Bluegill 53 QL X ER X LS WS X HS* X MA. SR GR X RB X PS X WM X BG X TABLE 12. (continued). Scientific and Common Name Pigeon Lake Abbreviation Lake Michigan Centrarchidae [ continued] Mioropterus dolomieui Lacepede Smallmouth bass Mioropterus salmoides (Lacepede) Largemouth bass Pomoxis nigvomaaulatus (Lesueur) Black crappie Pomoxis annularis Rafinesque White crappie Clupeidae Alosa pseudoharengus (Wilson) Alewife Doroeoma oepedianum (Lesueur) Gizzard shad Cottidae Cottus bairdi Girard Mottled sculp in Cottus aognatus Richardson Slimy sculp in Cyprinidae Coras sius auratus (Linnaeus) Goldfish Cyprinus oarpio Linnaeus Carp Notemigonus orysoleucas (Mit chill) Golden shiner Notropis atherinoides Rafinesque Emerald shiner Notropis dorsalis (Agassiz) Bigmouth shiner Notropis heterolepsis Eigenmann and Eigenmann Blacknose shiner Notropis kudsonius (Clinton) Spottail shiner Pimephales notatus (Rafinesque) Bluntnose minnow Pimephales promelas Rafinesque Fathead minnow Rhiniahthys oataractae (Valenciennes) Longnose dace Semotilus atromaaulatus (Mit chill) Creek chub SB X LB X BC X wc AL X X GS X X MS X X SS X X GF X CP X X GL X ES X X BS X NH X SP BM X X X pp LD CR X X 5h TABLE 12. (continued). Scientific and Common Name Pigeon Lake Abbreviation Lake Michigan Cyprinodontidae Fundulus diaphanus (Lesueur) Banded killif ish BK X Esocidae Esox amerioanus vermioulatus Lesueur GS X Grass pickerel Esox lueius Linnaeus NP X Northern pike Esox lueius x masqwinongy Tiger muskellunge TM Gadidae Lota lota (Linnaeus) Burbot BR X X Gasterosteidae Pungitius pungitius (Linnaeus) Ninespine stickleback Ictaluridae Iotalurus melas (Rafinesque) Black bullhead Iotalurus natalis (Lesueur) Yellow bullhead Iotalurus nebulosus (Lesueur) Brown bullhead Iotalurus punotatus (Rafinesque) Channel catfish No turns gyrinus (Mi t chill) Tadpole madtom Lepisosteidae Lepisosteus ooulatus (Winchell) Spotted gar Lepisosteus osseus (Linnaeus) Longnose gar Osmeridae Osmerus mordax (Mitchill) Rainbow smelt NS X BB X YP X BN X CC X Ml X SG* LR SM 55 TABLE 12. (continued). Scientific and Common Name Pigeon Lake Abbreviation Lake Michigan Percidae •kit Stizostedion vitreum vitreum (Mit chill) WL X Walleye Etheostoma nigrum Rafinesque JD JL X Johnny darter Perca flavesoens (Mi t chill) IP X X Yellow perch & Percina oaprodes (Rafinesque) LP Logperch Percopsidae Peroopsis omiscomayous (Walbaum) Trout-perch Petromyzontidae Iohthyomyzon castaneus Girard Chestnut lamprey Petromyzon marinus Linnaeus Sea lamprey Salmonidae Coregonus artedii Lesueur Cisco or lake herring Coregonus alupeaformis (Mit chill) Lake whitef ish Onoorhynahus kisutah (Walbaum) Coho salmon Onoorhynahus tshawytsoha (Walbaum) Chinook salmon Prosopium oylindraoeum (Pallas) Round whitef ish Salmo gairdneri Richardson Rainbow trout Salmo trutta Linnaeus Brown trout Salvelinus namaycush (Walbaum) Lake trout TP CL SL X X LH X LW X CM X X CH ** X X RW X RT X JL BT * X X LT X X Sciaenidae Aplodinotus grunniens Rafinesque Freshwater drum FD* * Not observed in 1977 standard sampling series <> ** Based on observation made while electroshocking, 1977. X 56 w c a 5- >* jj AJ CO co co 00 4J c rH CO rH rH CO fX, >*rH .J3 rH 0) • AJ *Q r^ •C a. r^ 00 s c^ a co rH 03 o a A • V4 03 X a a •a •H «. s a »-5 rH c C CO CO CO 00 00 > •H •H U s X CO S 4 CO < H!w^3'Own»-'wnr«nrl>rs»<,N*-OoOOOOOOOOOOOOOOOOOO ft*jco vr? o r- Osflr-'- *-oooooooooooooo©ooooooooooo r?CP'^*W*-C3.f'"*'^^C»*^MOODCOf,«»vO* i/: co cs a rsi co <*■» 9 HOMTJ O^ O CP H (»N ♦" o ■ O f> CO ST ST vO •■" •,«>*••*•0000<,^0000',"OOOOOOOOOOOv•'*, CM <"* • CC zT C\| ST ST r" r* r»Q i? fMOOCNOOCNOOOOOO**1! co 10 *■" U** O o r^ vo ^ r-1 C| <*>moo *- O O O «- O CO O o UJJ— 04 t4 ^-l C ^ u « AJ «H •M a. u 4J C « U "O V JS 00 cy « u 3 (fl 0! p O 3 c; iJ UJ -»«l u cn n -o TJ U3 Wi > u W Q. W C Vj 5 O a> o -4 QJ O u JZ\ f-« CQ •H « c a p; « j; >% S a » "3 c o « *-« c 0) u fl ^ O c *-» U V4 - i— ♦ o «H a ^J C «« jS JZ —» O o •H -C a crj 3 3 n 3 H u 2 C-? CQ CO H v: «3 ac X, O ^ u S3 35 H CO C/3 W H a* as 57 TABLE 14. Summary., of all fish species caught by all gear types in Pigeon Lake near the J. H. Campbell Plant, eastern Lake Michigan, June-December 1977. Alewife Spoetail Golden shiner Yellow perch Bluntnose minnow Largeaoueh bass Puapkinseed Black erappie Bluegill Rock bass Silverside Brown bullhead Northern pike Johnny darter Bowfln Tadpole mad too Grass plckeral Lake chub sucker Yellow bullhead White sucker Black bullhead Carp SI lay sculp in Rainbow smelt Gizzard shad Waroouth Soallnouth bass trout-perch Emerald shiner Banded killlfish Rainbow trout Goldfish Golden redhorse Bigmouth shiner Cisco Coho salsaon Blacknose shiner Lake trout Pirate perch Burbot Longnose dace Qulllback Mottled sculpln Channel catfish Nine spine stickleback jaw JUL AUG 15 3 18* 357 174 273 31 3 4 32 9 7 14 12 4 10 7 18 3 0 1 0 0 0 0 1 3 0 0 0 0 0 0 1 0 0 0 1 0 0 0 0 0 0 1 1169 SEP 6758 1557 1648 941 582 174 39 85 9 77 24 48 17 34 1 10 9 9 1 4 0 3 0 4 1 3 0 0 1 0 0 0 0 0 0 0 0 9 0 0 0 0 0 0 0 12039 183 527 630 398 653 136 54 37 41 46 31 25 16 20 9 1 14 3 15 2 3 3 1 1 2 0 0 0 1 0 0 2* 0 0 0 0 0 0 0 0 0 0 0 0 0 2854 OCT 133 23 33 151 3 87 110 107 25 34 58 9 79 6 12 7 14 7 3 0 2 9 2 1 1 4 2 0 0 1 0 0 0 0 0 1 0 0 0 0 0 1 0 0 0 0 3512 4 118 0 146 5 16 38 9 33 6 10 19 7 13 17 8 6 6 13 5 0 2 5 0 0 0 0 0 0 0 0 0 1 0 0 0 1 0 1 0 0 0 0 0 0 489 yov o 9 2 224 36 54 45 6 33 3 5 15 29 23 9 12 7 7 3 2 4 1 2 1 0 0 2 2 0 2 2 0 0 0 0 1 0 0 0 0 0 0 1 1 0 546 DEC 1 0 0 6 0 0 0 9 0 0 0 0 18 0 17 0 0 0 0 3 0 4 0 0 0 0 0 2 0 0 0 0 0 0 0 0 0 0 0 1 0 1 0 0 0 62 SOS XOP TOTAL 7094 4547 2615 2459 1560 760 232 183 178 173 158 120 113 109 70 55 50 46 35 18 17 15 9 7 7 6 5 4 3 2 2 2 34* 21o 12o 11o 7* 3c 1e 0, 0« Oo Oo 0. 0* Oo 0. 0. 0c 0o 0. 0. Oo 0. Oo 0c Oo 0. Oo 0. Oo Oo Oo 0o Oo 0* 0„ 0. Oo 0. Oo Oo 0o Oo 0. Oe 20667 "TW 997 651 896 547 677 122 885 861 837 764 581 547 527 339 266 242 223 169 087 082 073 044 034 034 029 024 019 015 010 010 010 005 005 005 005 005 005 005 005 005 005 005 005 005 explain the results of the study on the basis of biological and physical considerations and compared our findings with those available in the literature. Gonad data were used to identify spawning periods and explain distribution and were only presented for major and common species . Numbers presented in the table reflected the number of fish actually processed. Due to our subsampling procedures, gonad data could be biased since the most numerous size intervals were underrepresented. For each major species data concerning the water temperatures where a particular size fish was most often caught are presented. Using length-frequency histograms, we were able to separate Y0Y from adults and compare each group's distribution and behavior . Biological aspects related to temperature preference, predation and feeding habits were 58 TABLE 15. Summary of all fish species caught by bottom gill nets in Lake Michigan near the J, H. Campbell Plant, eastern Lake Michigan, June-December 1977. Jtin JUL AUG ST.? OCT 50V DSC StJ.1 %o? irsTU Alevife 67 327 325 435 0 1 0 1155 35. S 17 Yellow perch 58 111 368 146 1 37 0 721 22.171 Spoctail shiner 26 40 14a 349 0 31 0 590 18.HO White sucker 2 48 150 82 0 4 1 287 8.8;»5 Lake trout 2 42 1 101 0 Id 0 164 5.043 Gizzard shad 0 a 12 3 0 71 0 86 2.645 lain bow smelt 0 3 7 S3 0 0 0 63 U9:i7 Unidentified coregoaid 34 16 0 5 0 0 0 55 io6<:ii Longnose sucker 0 15 13 6 0 0 0 34 1.046 Trout-perch 0 2 8 3 0 21 0 34 1.046 Brown trout 2 3 3 11 0 10 0 29 0,892 Silver redhorse 0 2 2 3 0 1 0 8 0.246 Channel catfish a 0 6 0 0 0 0 6 0.1 RS lound whlteflsh 0 1 0 3 0 2 0 6 3.1«5 Coho saloon 0 0 0 1 0 4 0 5 0.154 SLainbov trout 0 a 0 0 0 4 0 4 0-123 Lake vhitef iah a 1 0 1 0 0 0 2 0.062 Carp 0 0 2 0 0 0 0 2 0.062 Sborthead redhorse 0 0 1 0 0 0 0 1 0.031 191 611 1042 1202 1 204 1 3252 TABLE 16. Summary of all fish species caught by surface gill nets in Lake Michigan near the J. H. Campbell Plant, eastern Lake Michigan, June-December 1977. jp* Alevlfe lainbbv sow It Lake trout Gizzard shad Brown trout Unidentified coregonid Vhite sucker Chinook salmon Coho saloon Spoctail shiner Longnose sucker 278 0 0 0 0 0 0 0 0 0 0 278 JUL *ua 251 1 12 0 2 7 1 0 0 1 1 276 0 0 0 0 0 0 0 0 0 0 0 0 SEP 205 34 17 0 4 0 2 1 2 0 0 265 OCT 0 0 0 0 0 0 0 0 0 0 0 0 KCV 0~ 0 0 19 4 0 0 2 0 0 0 25 otc 0 0 0 0 0 0 0 0 0 0 0 SU.T %OF TOTA 734 ' ad.3*>> 35 4. 147 29 3.136 19 2.251 10 l.lttS 7 0.829 3 0.3S5 3 0.355 2 0.237 1 0.1 '(3 1 0.VI8 844 59 TABLE 17. Summary of all fish species caught by trawls in Lake Michigan near the J. H. Campbell Plant, eastern Lake Michigan9 June--. December 1977. J UN JUL AUG SEP OCT NOV DEC sun %QT TOTAL Aiewife 743 195 2137 794 6557 4765 0 15191 49.740 Rainbow socle 1046 545 7395 2590 348 69 732 12725 41.665 Trout-perch 322 213 119 130 36 22 5 853 2*793 2*236 Spottail shiner 98 0 2 33 314 33 198 633 Unidentified coregonid 40 23 4 26 234 61 4 392 1.284 Johnny darter 116 13 17 73 68 * 9 1 297 0o972 Yellow perch 34 5 66 32 6 4 54 201 0.658 Sinespine stickleback 86 16 11 14 3 2 0 132 0.432 Slimy sculpin 12 S 0 0 3 1 23 44 0. 144 Lake whitefish 7 1 0 0 0 9 0 8 0.026 Lake trout 2 2 0 0 0 0 1 5 0*016 Mottled sculpin 4 0 0 0 0 0 0 4 0*013 Bound whitefiah 0 0 0 0 1 0 1 2 ©•007 White sucker Burbot 1 0 0 0 1 0 0 0 0 0 0 0 0 1 2 1 0*007 0*003 Longnose sucker 0 0 0 0 0 1 0 1 0.003 2511 1024 9752 3697 7570 4967 1020 30541 TABLE 18. Summary of all fish species caught by i seines in Lake Michigan near the Je Ho Campbell Plant, eastern Lake Mic higans , June - December 1977, Species JUS JUL AUG SEP OCT JfO? DSC S0«! %Of T0T1L Aiewife 1110 5077 11218 14880 2856 1643 0 36784 83.655 Spottail 435 1166 1298 3634 52 24 0 6609 15.030 Yellow perch 0 31 14 285 0 2 0 332 0.755 Rainbow smelt 19 5 16 29 5 1 0 75 0o171 Gizzard shad 0 3 2 47 13 4 0 69 0.157 Coho salmon . 47 0 0 0 0 0 0 47 0o107 Brown Trout 9 1 0 0 0 0 0 10 0-023 Unidentified coregonid 0 0 0 7 0 0 0 7 0.016 Trout-perch 4 0 2 0 0 0 0 6 0.014 Carp 0 4 0 1 0 0 0 5 0.011 Bluegill 0 0 0 0 4 0 0 4 0.009 Rainbow trout 0 0 0 1 3 0 0 4 0.009 Silver redhorse 0 4 0 0 0 0 Q 4 0.009 Longnose dace 0 0 0 0 1 2 0 3 0*007 Lake trout 0 0 0 2 1 Q 0 3 0.007 Vhite sucker 0 2 0 Q © 0 0 2 0.005 Silvers ide 0 0 0 0 1 © © 1 0*002 Johnny darter 0 0 0 0 0 1 Q 1 0.002 Lake sturgeon 0 1 0 0 0 0 Q 1 0.002 Emerald shiner 0 0 1 0 0 0 © 1 0.002 Puapklnseed 0 0 0 0 1 0 © 1 0.002 Chiaook salmon 1 0 0 0 0 0 Q 1 0.002 Hinespine stickleback 1 0 0 0 0 0 0 t 0.002 1626 6294 12551 18886 2937 1677 0 43971 60 TABLE 19. Summary of all fish species caught by bottom gill nets in Pigeon Lake near the J. H. Campbell Plant, eastern Lake Michigan, June - December 1977. Species Yellow perch Bovfln Northern pike Brown bullhead Alewlfe Black crappie White sucker Yellow bullhead Carp Golden shiner Gizzard shad Largetnouth bass Spottail shiner Black bullhead Trout-perch Pumpkinseed Rainbow trout Smallmouth baas Warmouth Lake trout Burbot Cisco Crasa pickerel Qulllback Golden redhorse Coho saloon JUN JU AUS SEP OCT NOV DEC sua %OF TOTAL U73- 53 4 2 6 12 1 0 2 0 0 0 0 0 0 0 0 0 0 0 1 0 1 0 0 0 0 79 0 3 0 0 0 0 0 3 0 0 0 0 3 0 0 33 35 6 11 2 3 2 2 0 1 3 2 3 0 3 0 0 0 0 0 0 0 0 1 0 0 0 79 21 13 7 1 6 4 2 0 2 7 4 3 X) 2 0 2 0 0 1 0 0 0 0 0 0 75 9 17 7 9 3 5 4 6 2 0 0 0 2 3 0 0 0 0 0 0 0 0 0 0 1 0 65 17 9 19 13 0 1 1 2 1 0 0 0 0 0 2 2 2 2 0 0 0 0 0 0 0 1 72 6 17 18 0 1 9 3 0 4 0 0 0 0 0 2 0 0 0 0 0 1 0 0 1 0 0 62 151 67 67 32 31 25 16 11 11 11 7 6 5 5 4 4 2 327 14. 14. 6. 6. 5o 409 409 382 667 376 441 3 66 366 366 505 290 075 075 360 360 430 430 215 215 215 215 ,215 ,215 • 215 • 215 465 TABLE 20. Summary of all fish species caught by seines in Pigeon Lake near the J. H. Campbell Plant, eastern Lake Michigan, June - December 1977. Species JOH JUL AUG SEP OCT sov DEC -SIL3 ?Q? TQTik. Alewifc 3 6757 175 127 1 0 Spoccall 3 1554 527 2333 116 9 Golden shiner 180 16 47 6 27 144 0 2 Yellow perch 307 928 363 366 137 207 Bluntnose minnow 174 582 653 110 5 36 Largemouth baaa 273 174 133 104 16 54 Pumpkinseed 31 39 54 23 38 43 Bluegill 4 9 41 58 33 33 Rock bass 32 77 46 9 6 3 Silverside 9 24 31 79 10 5 Black crappie 2 82 35 30 4 5 Johnny darter 12 34 20 7 ^3 23 Brown bullhead 1 47 23 5 10 2 Tadpole mad Com 10 10 1 14 8 12 Grass pickerel 7 9 13 7 6 7 Lake chubsucker 18 9 3 3 6 7 Northern pike 12 14 5 5 0 10 Yellow Bullhead 1 0 15 0 7 1 Black bullhead 1 0 0 7 0 4 Slioy sculpln 0 0 1 1 5 2 Rainbow smelt 0 4 1 1 0 1 Varaouth 1 3 0 1 0 0 Carp 0 0 0 0 0 3 Smallmouth bass 3 0 0 0 0 0 Bow fin 0 0 3 0 0 o Emerald shiner 0 1 1 1 0 o Banded kllllflsh 0 0 0 0 0 2 Goldfish 0 0 2 0 0 0 White sucker 0 0 0 0 1 t Blgmouth shiner 1 0 0 0 9 o Blacknose shiner 0 0 o o 1 o Nine spine stickleback 1 0 0 0 0 o ?lrate perch 0 0 0 0 1 0 Kottled sculpln 0 0 0 0 0 1 Channel catfish 0 0 0 0 0 T longnosa dace 0 0 0 1 0 0 090 12006 2775 3437 424 474 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 7063 4542 2604 2308 1560 754 228 178 173 158 158 109 88 55 49 46 46 24 12 9 7 5 3 3 3 3 2 2 2 34 22o 12. 11. 7. 3. 1. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0 0 955 478 837 422 720 732 128 881 856 ,782 782 539 436 272 243 223 228 119 059 045 035 025 20206 0.015 0.015 0.015 0.015 0.0 10 0.010 0.010 0.005 0.005 0.005 0.005 0.005 0.005 0.005 61 discussed when pertinent* Statistical analyses were done for major species in Lake Michigan to determine differences between months, stations C (6 m - s.) and L (6 m - n.) and time of day (see STATISTICS) . Common and minor species discussions include the size range, spatial and diel behavior patterns, spawning times and catch-temperatures when enough data were available* Several appendices contain data supplementary to the data presented in this section. Limnological and weather data collected during each sampling period are presented by gear type in Appendices 1-3. Length-frequency tables for all species caught during 1977 are presented by lake and month (Appendix 4), while Appendix 5 includes length-frequency tables for major species by gear type, month and lake* 62 Maior speoies Alewife — Introduction — The alewife is indigenous to the Atlantic Coast and was unknown in Lake Michigan prior to 1 9^9 (Brown 1972). Its arrival in the Great Lakes has been attributed to passage through the Erie Canal (Smith 1968). The numbers of alewives in Lake Michigan increased dramatically during the 1960fs until 1967 when a lakewide mass mortality decimated the population (Brown 1972). The cause of the dieoff remains undetermined, although many theories have been offered (Smith 1968). The alewife remains the most abundant species in Lake Michigan. Alewives are a major prey resource for the large numbers of salmonids in Lake Michigan (Wells and McLain 1 973) * Commercially, alewives are important in fish meal and pet food production (Scott and Crossman 1973). Alewives were the most abundant species captured by our sampling gear in both Lake Michigan and Pigeon Lake. This species accounted for 685S of the total catch by number in Lake Michigan (Table 13) and 34? of the total in Pigeon Lake (Table 14). In Lake Michigan, large seine catches of YOY alewives constituted most of the alewife catch (69?) (Appendix 4 and Table 18). Trawls contributed 28? of the total (Appendix 4 and Table 17) with 91? of the trawl catches containing YOY. The remainder of the alewives collected in Lake Michigan were caught in bottom gill nets (2?) (Appendix 4 and Table 15) and surface gill nets (1?) (Table 16). Most of the gill net catch was comprised of adults. Virtually all alewives caught in Pigeon Lake were YOY, except for a few adults caught in seines and bottom gill nets. According to Reigle (1969) and Wells ( 1 968) most alewives in Lake Michigan concentrate in deep water from January until mid-April. During May a massive shoreward migration occurs and alewives can be found over many depths. This migration occurs first at the southern end of the lake and proceeds northward. Spawning begins around mid-May in the southern end of Lake Michigan. Seasonal Distribution — June — In Lake Michigan more adult alewives were caught during June than any other month (Appendix 4). Gonad data indicated that some spawning had occurred by the first week of June (Table 21) based on the occurrence of spent alewives. Most fish caught in the study area had moderately or well developed gonads. During the day the largest trawl catches occurred at station C (6m - s.) and station L (6 m - n.); 297 and 334 respectively (Figs. 17 and 18). The only other day trawl catch containing alewives was taken at station H (21 m - s.). No trawling was done any closer to shore than 6 m, but higher concentrations would be expected there based on gill net data. Relatively few alewives o3 TABLE 21. . Monthly gonad conditions of alewives caught in Lake Michigan near the J. He Campbell Plant, eastern Lake Michigan, during 1977. All fish examined in a month were included except poorly received specimens. Males Gonad condition Jun Jul Aug Sep Oct Nov Dec Slight development 25 52 Mod. development 54 46 Well developed 88 5 Ripe-running 2 Spent 25 12 96 143 15 3 8 10 11 3 1 Females Slight development 6 30 Mod. development 32 45 Well developed 108 35 Ripe-running 1 Spent 40 19 Absorbing 47 110 14 4 23 Immature 71 227 400 647 778 500 Unable to distinguish were caught in bottom gill nets, but the highest catch (36) occurred at station A (1.5 m - s.) and declined with greater depth (Figs. 19 and 20). Despite some problems encountered when setting surface gill nets in June these nets caught large numbers of alewives (278) at station L (6 m - n.), but none at stations C (6 m - s.)> D (9 m - S*), or E (13m - s.) (Fig. 21 and Table 22). Based on gill net and trawl data, adult alewives seemed to be concentrated between 3 and 6 m during the day. While bottom gill net and trawl catches of alewife at station C (6 m - s.) and L (6 m - n.) were similar, surface gill net catches were not. Considerable numbers were caught at station L (6 m - n.) but none were caught at station C (6 m - s.) (Fig. 21). This could have been due to water temperature as surface water at station L (6 m - n.) was 12.0 C, 3*5 C warmer than station C (6 m - s.). The lake was calm that day and the warmer discharge water, being less dense than the lake water, was creating localized stratification. This difference may also have been due to problems encountered in setting srface gill nets during the first month of use* There are several possibilities why trawls were so effective in catching alewives compared to bottom gill nets. The most plausible 6k Station 1000 L (6m-N) 500. 0 □ day ■ night ND = no data Qi JUKE JULY AUGUST SEPTEMBER OCTCi^iH MOVfcMfcKii DECEKSSh 1000 H(21m-S) 50° JURE * Ml2 NO ND JULY AUGUST SEPTEMBER OCTOBER NOVEMBER 1000 * G(l8m-S) 5oo- jzi * n ND TO TO AUGUST SEPTEMBER OCTOBER NOVEMBER DECEMBER 1000 ' F(l5m-S) 500- d ■ o. 55 H O looo- H E(l2m-S) 50°- JULY AUGUST SEPTEMBER OCTOBER KOVEMBER DECEMBER XE JULY AUGUST -E?TEt:.E3 OCTCSEh S0VE:3£R SECETSER 1000 1 D (9m-S) 500 AUGUST SEPTEMBER OCTCci.t 30'.a:^i« SECSKasa 1000 C (6m-S) 5oo 0 1C00, B (3m-S) 50° 0 I — nn AUGUST SEPTEMBER OCTOtUH SOVEKfcER ND ND ND ND ND ND ND CD ND JULX AUGUST CEiTEMbER OCTOBER SOVE-fttR DECEMBER FIG. 17* Total number pf alewife caught in duplicate trawl hauls in Lake Michigan near the J. H. Campbell Plant, eastern Lake Michigan, June - December 1977, 65 1 1 al i -a CD jz 3 a* e s- 2 p i § i i HSU 'ON * k LDoo 5 + - i33 e to 3 op— «3 JZ JZ u •f— p— 35 £ (O c r© !U U CD Of-o +J P—D ^ GL f6 3 <3U T3 JZ 4-> •r- C § § CM 3 HSU 'ON CD oo a s t»i JZ CL OS 3 r- fO i— U JZ e W in T3 _r. •r- jz CU P JZ «3 E Z UW ^n s- ^ § >>-f- o -^ ^ O JZ M- • -5 JZ u S- T3 < (U *r- S-= OJ JZ CL CL 4-> JZ ii E en •r- «3 en sz ■ 1/1 JZ cu r*- «P"" «j r^ 4=> «— c^ JZ Q- ,«»> CD E » >> •p- 03 » s- n ii ii ■a a 2 I I I i HSU 'ON -55 S 4-8 I 1 1 1 i °1 § 1 1 HSU *OM I 1 1 I i 0) 4-> o 00 o 67 1 - - 1 ! ! i ! ' • ■ 1 [ f r 1 - i c cz - ■ . CN S 8 8" < 8 CN ss HSII "ON I i "1 I -8 -fl 1 i HSI£ 'ON 1 i 1 I O 00 + f Q3 2 CD 68 Station L (6m-N) E(l2m-S) D (9m-S) C (6m-S) B (3m-S) A(l.5m-S) 250 200 150 100 50-1 o. 250. 200- 150. 100. 50 JUHE 55 »e* ^ 20O-| < H 150- O H 100 250* 200. 150- 100 ' 50" 0. 250 150 50- s D day night ND = no data CEFTK'BER OCTOBER AUGUST SEPTEMBER SEPTEMBER OCTOBER J 1 250" JUNE JUI .1 AUGUST SEFTEMBER OCTOBER NOVB43ER DECEMBER 200. 150- 100^ 50- 0 _. l!D HD TO KD ND SEPTEMBER OCTOBER HOVEMBER Dn SEPTEMBER OCTOBER FIG. 190 Total number of alewife caught in duplicate bottom gill nets in Lake Michigan near the J. H. Campbell Plant, eastern Lake Michigan, June - December 1977. 69 - -8 HSU "ON PQ s •5? HSU 'ON 3 rmD a* c op— SL, 13 -o in .p O) c • c r— fO i— o> «r"° °?~ 0>JZ o E t- o s: 4J 4-> OJ O «^ J3 (T3 =-J CD •M C fO S. o op- C fO 4-3 p— J= O* en 3 p— (G e— S- >>»r- o O oC <4- C CJ S- a; -r- QJ =5 S£ • ex CT 4-> J= r° O) ^ 0J"O «p- JQ O . s » Z I! .8 C c < S HSU 'ON OQ S d O cj> HSU *0N O CM CD 71 (6m~N) (12m-S) (9m-S) 8S 35 0 fo 130 -I c 6m- S) 6 ■z 85- 130 - B 3m-S) 65- 130 - (1.5m-S. S5j i 0i- TOTAT LENGTH (mn) FIG. 20. (Continued) NOVBTBEH explanation seems to be that alewives were moving parallel to shore and would not be vulnerable to a gill net set parallel to shore . It is noteworthy that trawling done with the current during the day at stations C (6 m - s.) and L (6 m - n.) accounted for 98$ of the total catch. This may indicate that fish were moving parallel to shore against the current* No alewives were caught in day seines at Lake Michigan beach stations, which demonstrated that alewives were probably concentrated between the beach zone and the 9 m contour during the day. Daytime net avoidance may also be an important factor. At night adult alewives were found in the beach zone indicating a nocturnal shoreward movement as has been noted by Jude et al (1975). Large numbers (192-495 per station) were caught in seine hauls performed at Lake Michigan beach stations P, Q and R (Figs. 22 and 23). Differences between stations could have been due to schooling behavior 72 E -§ i s a "i s ai 3 °g 3 HSTJ 'ON -I •a ■.§ j i & HSli 'ON ' 3 3 ° § 3 HSU 'ON CD C 3 r"3 en c •p— s- 3 T3 CO ■M £Z CD T3 C Cin •p- r— JZ r— CJ •r» •p" ens: cd a cj -i^ fO nj <+- -J S- 3 ZZ CO S- cu CD 4-> 4-> o-J trs «3 a aj •r p~D *» Q.4-* 3 c: ~o ai P-- C Q. • •r* "O l^ia 0) +-> r— £= jz a; L. cnj:* 0 3 CL M~ *3 £= C CJ CO CD O C_ CD <+- • CD C '5 ""' • — CD • "~" r— T) CL ra E a) (0 s- jc: OT o +■> <+- T~ S-. JZ CO fll$ CD £ a> — res c: CI i. en c: 0 O ret z: 4-> O CO «P~ ii •r- jz: JZ c> * •P"' >>2: CJ • c a' "O CD J* CD 3 JC CL. en 3 ,— U CD CD CL M~ E •r— rO CD "fQ zc s- • O »-D CD CO JC E -M V~ c o CD -r- cr -m CD CD JC s» «i£ cn 1 -J C 4-* C !! £ ■ CD f^. c?> CO CD "O jQ si D 76 jlIL TOTAL LENGTH OCTOBER FIG. 23. (Continued) TOTAL LENGTH (as distribution at night. One adult was caught by seine at beach station V (undisturbed Pigeon Lake) during the day. Alewife spawning was observed in Pigeon Lake during this period. A 35 mm alewife was seined at beach station T (influenced by Pigeon River) on 1 June. Origin of this YOY fish is open to conjecture. It was either the result of very early reproduction (1 April) or very late reproduction from the previous year. July — Fewer adult alewives were caught during July in Lake Michigan compared to June; while, YOY appeared in great numbers, particularly in seine catches (Appendix 5)* Fewer adults with well developed gonads were caught in July than during June (Table 21). A high percentage of females had gonads in the well developed state compared to males. During the day adults along the bottom were concentrated near 3 m and 18 m, based on trawl and gill net data. Few adults were taken in seines and bottom gill nets set at station A (1.5 m-s.); and station C (6 m - s.) bottom gill nets contained fewer fish than those set at station B (3 m - s.). Few alewives were caught in bottom gill nets or trawls between 6 and 15 m (Fig. 17? 18, 19? and 20) . The explanation for the daytime distribution of these two groups of alewives at 3 and 18 m could be related to gonadal maturity. The inshore group contained many spent individuals, while the offshore group was composed of fish with developing gonads. Day surface gill nets from stations C (6 m - s.) and L (6 m - n.) contained the most alewives, 46 and 15, respectively (Fig. 21 and Table 22) among the four stations where nets were set. More alewives were caught at station C (reference) than L (near the discharge) despite the fact that station C was 4.2 C cooler than station L. It appeared that differences in catch of this magnitude were due to different size schools encountering the nets rather than any increased population of 77 TABLE 23. Monthly gonad conditions of alewives caught in Pigeon Lake near the J. H. Campbell Plant, eastern Lake Michigan, during 1977* All fish examined in a month were included except poorly received specimens . Gonad condition Jun Jul Aug Sept Oct Nov Dec Slight development 2 4 2 1 Mod. development 12 2 Males Well developed Ripe- running Spent 2 Females Slight development 1 Mod. development 1 Well developed 4 Ripe-running Spent 2 Absorbing Immature 1 79 17 22 Unable to distinguish alewives because of attraction to -warmer water. Day seine catches of alewife in July ranged from 250 to 1115 fish per station in Lake Michigan (Figs. 22 and 23) . YOY', ranging in length from 20 to 50 mm, comprised 9&% of the seine catches . Highest catch (1115) was at beach station P.(s. reference)- Station Q (s. discharge), which was 6 C warmer than the other two stations, yielded 372 alewives. Again water temperature did not appear to be an important factor in the determination of distribution. Bottom gill net catches showed that alewives were present more at station B (3 m - sj during the day than at night (Fig. 19 and 20). The highest catch (30) observed in bottom gill nets occurred at station A (1.5 a - s.) at night. Few adults were caught in seines during July. Four alewives were caught in all trawls at night in July, although no data were collected at stations B (3 m - s.), G (18 m - s.) or H (21 m - s.) (Fig. 17 and 18). Night surface gill net catch of alewives did increase over day catches at all stations with most being caught at stations C (6 m - s.) and L (6 m - n.) (Fig. 21). Apparently alewives moved into surface water during the night and spread out over a large area since increases in surface gill net catches from day to night occurred from 6 to 12 m. 78 •s - ^ CO HSU ■ H HSU *P\ HSU 'ON CD C 3 o> •r— S- 3 T5 C/> CD • c c SZ c •f- (T3 +-> ol JZ CHr— 3 r— Id CD U JD CL 0) E <♦- rd -s - -a f-S HSU "ON E (d s. S- ra CH CD o c CD •r- J* jz > CJ c c o CD CD 3 CD CT*«- • CD Q- . S- *+- C 4-> r^. c o> CD «-* -J i- CD -0 C3 U. *J CD E SL. O CD CL SZ CD en c •r» •!■— C r— CL II E ■ 00 cn rd c O ii 2: D " 79 -a HSU 'ON 4- -S - g | | ° 1 1 HSii -(»N 3 § HSTi 'ON o 4-3 CD C 3 •"D cn cr Of-O s- 3 T3 V) p-» 6 3 c: 03 «{■» CD JZ £ u •p° 'P" cd s CO CD CU «^ 4J fO fi3 _J «3 Q~ O p» CD r-» ^ CD of""8 jQ 3: Q. CD E r— ° A3 A3 o £- o O zn t}» > CD U «^ C A3 CD -J 3 0 crcp CD O -C &- cd cn <4~ OVr— I »»- c <£z cl, 4J SI C7> £ CD *" ■ _j r^ r^» CT> « ?-i >j in ff3 CM &~ ~o CD -O ii « O LL o 80 TOTAL LENGTH (mm) OCTOBER FIG. 25. (Continued) Our sampling in mid-July occurred during an upwelling when water temperatures were approximately 10 C lower than in early July* Apparently ale wives did not move into the inshore zone during night as normal which may have caused a temporary cessation in spawning. This hypothesis was strengthened by August larval alewife data which showed unusually low numbers of 12-19 mm alewife larvae in samples collected* Further analysis may indicate that absence of the 12-19 mm larval group coincided with those larvae which normally would have been spawned during the upwelling period. Nocturnal movement was apparently more vertical than shoreward. Surface waters were 4.3-8.0 C warmer than bottom waters which may at least partially explain why alewives sought surface waters during the night. There were large differences in seine catches at Lake Michigan beach stations during July at night. Catches at stations P (s. reference), R (n. discharge), and Q (s. discharge) were 183, 42, and 3115, respectively (Figs. 22 and 23). Station Q was 3-4 C warmer than station P and R during the night which may account for the highest seine catch at station Q, yet station Q during the day was 6 C warmer than the other beach stations, but accounted for far fewer alewives (372) than station P (1115). Therefore temperature did not appear to be a good explanation for catch differences between stations as results were conflicting. In Pigeon Lake during July only one adult alewife, a female with well developed gonads (Table 23), was caught in a gill net set at openwater station Y, (influenced by Pigeon River) (Fig. 24). Spawning in Pigeon Lake may therefore occur into July. More alewives (YOY) were caught during July in Pigeon Lake than in Lake Michigan despite greater effort with different gear in Lake Michigan. Most YOY seined in Pigeon Lake were caught at beach station V (94?) (Fig. 26). These YOY probably resulted from early spawning that took place in Pigeon Lake. The catch of alewives from beach station S (influenced by Lake Michigan) 81 250 -j 200 - ISO 100 - 50 - 0 J UN □day 6324 [y^ Station V night JUL AUG SEP OCT NOV 250 . 200 -| o 25 150 - < H 100 O H 50 Station T JUN Station S JUL AUG SEP OCT NOV 250 i 200 150 -} 100 50 0 428 C3 ™ JUN JUL AUG SEP MONTH OCT NOV FIGe 26c Total number of alewife caught in duplicate seine hauls in Pigeon Lake near the J, H. Campbell Plant9 eastern Lake Michigan , June - November 1977, 82 constituted 6% and that from station T (influenced by Pigeon River) represented < 1% of" the total alewife catch for July (Fig. 25). YOY caught during July ranged from 30-50 mm. The area surrounding station V (undisturbed Pigeon Lake) is very shallow and quite productive, an area where young alewives would probably find abundant food, and cover for protection from predators as well as preferred water temperatures . Concentrations of alewife larvae at station T in early June were among the highest recorded in Pigeon Lake , yet few YOY (five) were seined there at the end of July. It seems possible that growing YOY would migrate downstream as they do in spawning streams along the Atlantic Ocean (Cooper 1961). Drastic differences occurred between seine catches of alewife during the day and night in Pigeon Lake, which were unlike those observed at beach stations in Lake Michigan. Despite catching thousands of alewife YOY at beach station V (undisturbed Pigeon Lake) during the day, no alewives were caught there at night. This phenomenon was true for the other Pigeon Lake beach stations as well. Apparently, YOY moved offshore at night. An offshore movement from beach stations at night was documented for YOY alewives in Lake Michigan at the Cook Plant (Jude et al 1975). Entrainment of alewife fry at Campbell also increased at night during July. In addition, plankton nets collected large numbers of fry at night along beach station S (influenced by Lake Michigan), while the seine, collected none. The reason for this is not understood. August — General daytime distribution of adult alewives in August appeared similar to that of July with most adults concentrated around the 3 m contour. High numbers of adult alewives (205) were taken in bottom gill nets at station B (3 m - s.), while fewer (44) were caught at station A (1.5 m - s.), and none were caught at stations C (6m- s.), D (9 m - s.), or E (12 m - s.). Only five adult alewives were caught at station L (6m - n.) No surface gill nets were set. Day seine catches were high during August (Fig. 22) with all alewives caught being YOY (Fig. 23). Numbers of alewife caught ranged from 189 at beach station Q (s. discharge) to 3167 at station R (n. discharge). As water temperatures at the three beach stations were all 25 C + 0.5, catch differences between stations were probably due to the size of the alewife school that happened to be in the area at the time of sampling. Very few adult alewives were caught by trawls during the day probably due to net avoidance. Nine adult alewives were caught at station E (15 m - s.), four at station H (21 m - s.) and three at station L (6 m - s.) . YOY alewives appeared to be concentrated from the beach zone out to 6 m during the day. Large numbers of YOY alewife (1947) were trawled at station B (3 m - s.) during the day, while few (43) were caught at station C (6 m - s.) (Fig. 18). Only one YOY was caught at station D (9 S3 m - s.) and none were caught at deeper stations. At night, seine data showed that numbers of YOY alewives in the beaoh zone remained high. Catches of YOY ranged from 121 at station R (n. discharge) to 5395 at station P (s. reference). Again water temperatures were nearly the same' (+ 1 C) and differences in catches seemed attributable to natural variation rather than any real differences in distribution . Low numbers of adults (4-23) were present in night seine catches at the three beach stations. A few adults were also caught at each trawling station with the most (14) caught at the deepest station, station F (15 m - s.). Night trawl catches were greater than day catches at stations C (6 m - s.), D (9 n - sj, F (15 n - s.) and L (6 m - n.) (Fig* 17). Higher night catches were probably due to an offshore movement of YOY, more widespread distribution of adults and less net avoidance. No YOY were caught deeper than station E (12 m - s). Bottom gill net catch of adults at station A (1.5 m - s.) and B (3 m - s.) dropped dramatically from 44 and 205 during the day to 18 and 11, respectively, at night. All catches of adults in bottom gill nets set between 6 and 12 m increased at night compared to day samples. Gill net and seine data, indicated that adult alewives were widely distributed at night in August over an area including the beach zone to at least the 12 m contour . Few alewives with well developed gonads were caught in August indicating that the spawning period was over or nearly so by this time (Table 21 )• Many fish showing slight gonad development could have been spent individuals as the gonads look similar in the two cases . Water temperatures in Pigeon Lake in July were probably at their maximum, particularly at beach station T (influenced by Pigeon River) which may have inhibited movement of spawning alewives into these areas. Limited information exists about temperature preference of alewife (Carroll 1973, Otto et al. 1976), but water temperatures above 19 C may be avoided. Only one alewife was caught in August during the day in Pigeon Lake; a YOY seined at beach station T (influenced by Pigeon River) (Appendix 5). At night eight adult alewives were caught in a bottom gill net at 6 m openwater station M (influenced by Lake Michigan) (Fig. 24 and Table 24). Adult alewives in Pigeon Lake either showed slight or moderate gonadal development (Table 23)? so that spawning appeared to be minimal during August in Pigeon Lake. At beach station S (influenced by Lake Michigan) there was a dramatic increase at night in the number of YOY alewives caught which was not seen at other Pigeon Lake beach stations. Normally, YOY alewife catches are higher at beach stations during the day than at night because of nocturnal offshore movement (our data from other months and Jude et al 1975). August seemed to be an TABLE 24. Total number of alewife caught in bottom gill nets fished during day and night once per month June through December 1977 in Pigeon Lake (Port Sheldon, Michigan). ND = no data. Month Station June July August September October November December day 9 0 0 0 0 0 0 M (6m) night 3 0 8 6 3 0 1 day 0 0 0 0 0 0 0 Y (1.5m) night 0 1 0 0 0 0 ND exception since only Lake Michigan beach station R (n. discharge) seine catches followed the pattern. Seine catches at stations P (s. reference), Q (s. discharge) and S (Pigeon Lake - influenced by Lake Michigan) were higher at night than during the day* This deviation from the other months results is difficult to explain. The total absence of YOY during the. day at station S and lower numbers at stations P and Q could have been the result of patchy distribution of YOY and our nets missing the schools, but this seems unlikely. Net avoidance may have been a factor in reducing day seine catches, but it is difficult to understand why this would have only affected certain stations and months (i.e., August). September — Large numbers of YOY alewives were seined in the beach zone of Lake Michigan during September. Numbers caught ranged from 2893 at station R (n. discharge) to 6570 at station Q (s. discharge) (Fig. 23). All alewives caught in day seines were YOY. Spawning had ceased in September according to our gonad data (Table 21). No individuals with well developed, ripe or spent gonads were found. Trawl catches contained a mixture of YOY and adults during September (Fig. 17). The largest trawl catch at station B (3 a - s.) contained 229 YOY and 91 adults (Fig. 17)* Low numbers of YOY were also caught at stations C (6m- s.), D (9m- s.), G (!8m-s.) and L (6 m - n) . The most adults (260) were trawled at station G. The other sizable catch of adults (52) occurred at station L. Adults were scattered throughout the study area since they were caught at all stations except D (9 m - s.) and F (15 m - s.). September data indicates a gradual movement toward deeper water by both YOY and adult alewives. 85 Bottom gill net catches, ranging from 3 to 32 fish, were fairly uniform along south transect stations' (Figs* 19 and 20). Most alewives caught were adults, but a few YOY greater than 100 mm in length were caught . A very large catch (322) at station L (6 m - n.) was ten times larger than any gill net catch along the south transect; 95% of the catch was adults. No water temperature difference existed between the two 6 m stations, C and L; apparently larger numbers of adult alewives were present in the area of the thermal discharge. Day surface gill net catch at 6 m station L was higher than that of the reference station C which corresponded with results from bottom gill nets (Figs* 20 and 21). No significant difference in bottom gill net catches was apparent at night between stations C and L. The largest night catch in bottom gill nets occurred at station A (1.5 m - s.) where 26 alewives were caught. All were adults but one. Other catches along the south transect ranged from one to six fish. Only two alewives were caught at station L (6 m - n.). Compared to day catches, night surface gill net catches increased at both stations C (6 m - s.) and L indicating that adults were moving off the bottom at night . Numbers of alewives caught in seines at night were lower than day catches. This decline in number was due to decreased catch of YOY. This age group began to migrate offshore at night. A few adults were caught at night in seines indicating some movement by adults toward shore „ Night trawl catches of YOY were larger than day catches at station C (6 m - s.)i additional evidence for an offshore movement of YOY. There was a slight increase at night in the number of YOY caught in trawls at' station L (6 m - n.). Data from three stations, C (6 m - s.), D (9 m - s.) and E (12 m - s.), were compared for differences in mean length of YOY alewives for day and night trawl catches . These stations were selected because data were available for both day and night. Mean length of alewives in day samples collected at the three stations ranged from 73 • 2 to 75*3 mm while mean lengths for night samples ranged from 40.1 to 49.6 mm* YOY alewives found in deeper water at night are thought to come from the beach zone since numbers caught in seines were lower at night than during the day. Larger YOY found on the bottom during the day migrated upward at night as shown by the occurrence of larger YOY in night surface gill net catches in September. No alewives were caught in bottom gill nets in Pigeon Lake during September. At beach station S (influenced by Lake Michigan) numerous YOY were caught by seines both during the day and night. Like Lake Michigan, fewer were caught during the night than during the day. 86 Adults caught during September showed only slight gonadal development (Table 23). October — The most striking change in the distribution of alewives between September and October was the general disappearance of adult alewives from the Lake Michigan study area. Only one adult male (moderate gonadal development) was taken during our sampling and that was from a night seine haul at beach station Q (s. discharge) (Fig. 23). During the day, YOY alewives were prominent in all trawl catches (Fig. 18). The largest catch (1847) was made at the deepest station, H (21 m - s.), showing the offshore movement by YOY alewives. Large differences in seine catches occurred during the day, ranging from zero at station Q (s. discharge) to 2588 at station R (n. discharge). Only six alewives were seined at station P (s. reference). The water temperature difference between stations was only 2.8 C so it was unlikely that this factor was responsible for the large variability observed. At night in October, seine catches were as low as they were in September, ranging from four at station R (n. discharge) to 252 at station Q (s. discharge) (Fig. 22). Numbers of alewives (YOY) caught in trawl hauls increased at night when compared with day catches at all stations except L (6 m - n.). Catches ranged from 397 to 591 along the south transect. Larger YOY were found in trawl catches during the night than during the day, which was opposite to the pattern observed in September. Mean lengths of YOY caught at stations C (6m- s.), D (9 m - s.), E (12 m -■ s.) and P (15 m - s). were calculated. Mean length of alewife YOY increased with increasing depth and ranged from 40.8 to 50.2 mm. This phenomenon has also been observed by Wells (1968). At night no increasing trend in YOY lengths was observed and mean lengths ranged from 61.4 to 65.7 mm. Net avoidance is a possible explanation for catching larger fish at night than during the day, but does not appear to be the best explanation for this situation. The alewives in question (the larger of the YOY around 70-100 mm) were represented in other day trawl catches throughout the study period (June through November), indicating that at least during these times they were not avoiding the trawl during the day. -Another possible explanation for the diel changes in lengths of alewives in trawl catches was a nocturnal shoreward migration of larger YOY found in deeper water during the day. Alewives with lengths up to 90 mm were caught at station H (21 m - 3.) during the day. Maximum size of alewives decreased with depth in day trawl catches. At night, the maximum size of alewives caught increased at inshore stations when compared with offshore stations approximately to the maximum size found at deeper stations during the day. 87 A few adult alewives were caught in Pigeon Lake during October at station M (influenced by Lake Michigan) in a night bottom gill net (Fig. 24 and Table 24) . YOY numbers dropped considerably from September as only one was caught in a seine at beach station V (undisturbed Pigeon Lake) (Fig* 25)* Adults caught during October showed only slight to moderate gonadal development (Table 23)° November — Results of sampling during November were similar to those observed in October* Very few alewife adults appear to have been in the area as only one male was caught in Lake Michigan , in a bottom gill net set at night at station A (1.5 d - s.) (Fig. 20). All other alewives caught were immature (Table 21). Day seine catches of alewife ranged from ten at station P (s. reference) to 1075 at station R (n. discharge) (Fig. 22 and 23). Trawling data showed that numbers of YOY declined from the beach zone to the 9 m contour. Numbers were low between the 9 and 15 m contours. At deeper stations G (18 m - s.) and H (21 m - So), concentrations of YOY alewives increased to a maximum of 4112 at station H. As in October, maximum length of YOY increased with increasing depth. At night numbers of YOY caught increased at all stations where trawling was performed when compared with day catches. No alewives were caught in surface gill nets indicating that a horizontal rather than . vertical migration of larger YOYs was occurring. YOY longer than 85 mm, present in earlier months, were not caught in November indicating that larger YOY had moved from the study area by this time. No alewives were caught in Pigeon Lake during November. Therefore it appears that Pigeon Lake does not have an overwintering population of alewives . December — . By December nearly all alewives appear to have left the study area. No alewives were caught in day or night trawls in Lake Michigan. No gill netting or seining was done during this month in Lake Michigan. The only alewife caught during December was a YOY taken in a bottom gill net set at openwater station M (influenced by Lake Michigan) in Pigeon Lake (Fig. 24 and Table 24). Temperature-Catch Relationships — In Lake Michigan, YOY alewife appeared to be caught in warmer water than adults. Adults were rarely caught above 18 C while YOY were caught in water as warm as 30 C (Fig. 27). Otto et al. (1976) indicated that YOY had a higher temperature preference than adults and our field results in Lake Michigan seem to provide evidence for this finding. The pattern of YOY being taken at warmer temperatures than adults in Lake Michigan was not observed in Pigeon Lake. Adult alewife in Pigeon Lake were caught at water temperatures up to 21 C and YOY were collected at temperatures up to 23 C, a small difference (Fig. 27) • Unlike Lake Michigan, the range of water temperatures during warmer 88 JU i Pigeon Lake 25 20 < ' o 1 | 1 • • Uj 03 CU a j* •i- 03 r— «J CL =3 C *"0 S- 0) C 4-> •r- co 03 +-> 03 C a 03 4-> O- -I ■8 J , jj -s? — » ' 1 r— D 93 TOTAL LENGTH (ran) OCTCBER FIG. 28. (Continued) TOTAL LZ:;CTH N0VB1BER the day than at night (Fig. 29), clearly not net avoidance. Yearlings collected in June ranged from 50-120 mm in total length and had a modal length of approximately 80 mm (Appendix 4) . Several specimens were caught by night seine (Fig. 28), but most were taken by day and night trawl (Fig. 30). Night distribution of yearlings extended from the beach zone to the 21 m depth with highest concentrations at the 6 m contour. During the day they ranged from 6 to 21 m, being most common at 9 m. Yearlings seemed to move close to shore and into the beach zone at night ? but remained in deep water during the day. Similar nocturnal movements to the shallow areas appeared to also occur during other summer months (Figs, 28 and 29)* These data were in agreement with Emery (1973) who observed a large number of smelt of all sizes in shallow areas during night SCUBA dives in Little Dunkfs Bay in Georgian Bay, Lake Huron. Comparisons of day vs. night catches of yearling smelt suggest that they, like adults, may exhibit diel vertical migration (Fig. 30). The June catch of yearlings was the highest of all monthly catches of this size class. Presence of modest numbers of yearlings near the Cook Plant, in southeastern Lake Michigan during April and May (Jude et. al. 1975) suggests that they also may occur near the Campbell Plant at this time. July — Catch of adult smelt declined sharply in July (Appendix 4).- Small numbers of large smelt were trawled during the day between 12-18 m (Fig. 30). Three adults were caught in day bottom gill nets (Figs. 31 and 32) and one in a night surface gill net at the 6 m contour (Fig. 33). Adult smelt were not collected by seine. Most adult smelt were probably in deeper cooler water by this time* In summer, they were found mostly from 9 to 30 m in eastern Lake Michigan (Wells 1968) and in slightly deeper water ( l6-90m) in northern Lake Michigan (Jaiyen 1975). In Lake Erie however, large numbers of yearlings were found in water 6-9 94 Station □ day ■ night ND = no data 1000 L (6m-N) 50° • 0 1000 «| H(21m-S) 500 o -t 1000 G(l8m-S) 500 1000 F(l5m-S) 500 O o- < .g looo H E(l2m-S) 50°- 0 1000 D (9m-S) -5oo 1000 C (6m-S) 500 a i i M» i i JULY AUGUST SEFTO3EH OCTOBER !MV»«ER PECEMHER JIB MB SD JULY AUGUST SEFTB3ER OCTOBER 30VEMBER DECEMBER TO !ID HO JULY AUGUST SEPTEMBER OCTOBER NOVEMBER DECEMBER JULY AUGUST SEPTEMBER OCTOBER HOYEMBER DECSSER 2582 ml I 1 AUGUST SEPTEMBER OCTOBER S0VE>2ER DECEM5ER JULY AUGUST SEPTEMBER OCTOBER NOVEMBER DECSSER JULY AUGUST SEPTEMBER CCTObER HOVEMBER DECEMBER B (3m-S! 1000 « 500- 0 .ID RO HO NO NO TO TO JULY AUGUST SEPT2SER OCTOBER NOVEMBER DECEMBER MONTH FIG. 29. Total number of rainbow smelt caught in "bottom trawls fished during day and night once per month June through December 1977 in eastern Lake Michigan in the vicinity of the J. H. Campbell Power Plant, 95 , o «M CD E 3 -I /-s 3 . ' = -U3 O 13 co 2 5 3 rc " * * " ' . s (T3 »«- . e tr Mich . . . =. o 4J 1 | re CD V3 V5 ifl "v/3 JZ 2 * S I j_ 'JZ JZ -I —J E r-4 i-i CN c^ s 3 +J ■—' v^ v- • \»/ s—' ^-^ >-' R3 C U S- &- D1 A3 0 CD CO •r- C en c u CD -r- 3 S cr s~ ^ 1 «J «C SZ cu r^ en 4-> en u T3 CD E s- o S-. CD CL S3 S >V li D CD E s- o 4- S- CD Q. en CL E rX3 CO 96 1 j ! j. 200 1 p 1 i -V2 - ■ ■ 1 ' \ a 1-2 w . i ! . . ■ L. i 4 - < 1- j-8 HSII °ON • h ■ • ' - 1 L i ! . . f ! r— i U- ■ 1 • cz c 4^ q 1 1 M U § < § ° § § CO CO CO HSU "0M § § v: c o o o m en 97 Mi •S3 ■1 5 c •a 03 CO 00 HSIi °0N § § Q2 •in o -I 2 b •a 32 r— JO rj hr- O C/3 •z ■=^ »r— »r- « S o^s mi E cd _J O xa c s- a; -o c CO C r— •i~ Qu 4-> r— «C r— CD O O) •12 HSU 'ON £ """3 o JQ cu C «C •r- 4^ fO £~ fO s- cu o c <♦- c CO rO E CD ro •r— S- J= en CJ o •r— 4-> s: CO •f— CD jC «^ rO >>-J a c C CD •r— 3 o crr^ 4-> a; r-. jc s- Cft a> i p— •r- sz £- +-> cu u 0>-jO C E ■ CU CU — 1 4-> CU fc/"> >^ CM ro o -o 4-> (1 # >> C5 1 i 3 G .01 t,6m-i>0 3 " E ^ » (,12ni-S) (9m-S) c (6m-S) (1.5m-3) 1" a B (3m-S) 3 0 6 - ■ I ■ , IIL J8 , I JLHH i 1 ■ i.lin n , n. 50 100 ISO 200 TOTAL LENGTH (mm) SEPTETO FIG. 32. (Continued) smaller numbers during August than in July (Appendix 4). At night, several specimens were collected by trawl in waters up to 15 m deep (Fig* 30) and by beach seine (Fig. 28). They seemed to be evenly distributed in this zone at night. During the day yearlings were caught only from 12 to 21 m and were most common from 15 to 18 m. Compared to previous months, their day range appeared to be steadily shifting toward deeper water. A slightly higher number of yearlings were caught at night than during the day. Largest catches of YOY during 1977 were made in August (Appendix 4)* By this time YOY smelt ranged from 30 to 45 mm in total length with a modal length of approximately 40 mm. In the vicinity of the Dc C. Cook Plant, southeastern Lake Michigan peak catch of YOY approximately the same size also occurred in August 1973 (Jude et al. 1975)* This supported our previously asserted hypothesis that smelt in our study 102 c < ) ( 12m- S.> (. 9m-b; c i hm-S j rl nn fk, ■ ■ I ■ I TOTAL LENGTH (mm) JULY TOTAL LENGTH (mm) SEPTB^BEP FIG. 33. Length-frequency histograms for smelt caught in duplicate surface gill nets during July to September 1977 in Lake Michigan near the J. H. Campbell Plant, eastern Lake Michigan, q = day Is night. + = No sampling performed. area spawned at approximately the same time as those near the Cook Plant. YOY were caught only by trawl during August, suggesting that smelt this size rarely entered the beach zone. During the day YOY were found from 6 to 21 m and were most abundant at the 12 m contour (Fig. 30). At; night YOY were distributed from 6 to 15 m with the highest concentration at 15 m. The large YOY catch at 15 m suggested that YOY smelt probably range into deeper water at night. Night trawling was, however, not performed at 18 and 21 m in August. September — In September catch of adult smelt was higher than any monthly catch during the study (Appendix 4). Adult smelt were present in the area due to an upwelling of cold water (mostly from 5".1 to 10.6 C) . They were caught in all our fishing gear and appeared to be distributed from the beach zone to 15 m or deeper water (Fig. 29)- The September catch provided strong evidence of diel vertical migration by adult smelt. Surface gill nets at 6 m captured several large smelt at night and very few during the day (Fig. 33). Bottom gill nets and trawls, on the other hand, captured more adult fish during the day than at night (Figs. 32 and Appendix 5). Yearling smelt populations in the study area, as revealed by our catch, decreased slightly from the level observed in August (Appendix 4). Cold inshore water may have delayed their retreat to deeper water. Yearlings were caught mostly by trawl (Fig. 30); seines and gill nets captured only a few large yearlings (Figs. 28 and 32). During the day they were found at all depths from the beach zone to 21 m. At night their distribution extended from the beach zone to at least 15 m (no trawling was performed at 18 and 21 m) . 103 Catches of YOY continued to decline in October and November (Appendix 4) as most YOY had probably moved to deeper water by this time. More YOY were caught at night than during the day in these 2 months- In eastern Lake Michigan, Wells (1968) reported catching appreciable numbers of YOY smelt in water 18 to 36 m in October and November . In December YOY catch increased considerably over the previous 2 months (Appendix 4). During the day they were caught by trawl from 3 to 15 m (no trawling was performed at stations deeper than 15 m during the day), and were most common at the 12 and 15 m depths (Fig. 30). At night YOY occurred from 3 to 9 m (no trawling was performed in water deeper than 9 m at night) with the highest concentration at 6 and 9 m. In December more YOY were caught during the day than at night probably because night trawling was performed at fewer stations than during the day. Due to bad weather, no other fishing gear were used* The large catch of YOY in the study area suggested that they may periodically return to shallow water in late fall. These YOY were actively feeding during this month as 94$ had food in their stomachs. Temperature-Catch Relationship — Smelt usually inhabit in cold water. Various size classes, however, have been observed to show different temperature preferences. Ferguson (1965) indicated that adult smelt preferred water temperatures around 6.1 C. Jude et al. (1975) reported catching most adult smelt at water temperatures of 6-8 C and most YOY and yearlings at 12-14 C. In our study area yearlings were caught most often at temperatures ranging from 4-12 C and adults at 6-14 C. These observations agreed with Wells (1968) who found most smelt in water temperatures of 6-14 C. YOY less than 70 mm appeared to tolerate relatively warm water and occurred in waters with a wider temperature range than did larger smelt (Fig. 34). In our study area most YOY were caught in water from 6 to 20 C. In Lake Erie, Ferguson (1965) found large numbers of YOY smelt but very few adults at a water temperature of 21 C. In another study on Lake Erie smelt, MacCallum and Regier (1970) received larger catches of YOY in 18 C water. Based on data from several Maine lakes, Rupp (1959) concluded that there was a marked inconsistency in the timing of smelt spawning runs with respect to water temperature. Both water temperature and weather conditions may influence the smelt spawning run (Van Oosten 1940). In southeastern Lake Michigan, Jude et al. (1975) observed peak spawning in April when water temperatures ranged from 8 to 10 C. Other Considerations — > Although rainbow -smelt occurred in appreciable numbers in several inland lakes, there appeared to be no resident smelt population in Pigeon Lake. Only seven specimens, 104 o r-f C smelt caught by al stern Lake Michiga O cd o 5 0) CM ervals of rainbo Campbell Plant, *—. u O 8 c • m £ •H S — j 42 o CO < 4J i-J C > 60 O cr fi 0) -H LU CD JZ U rH 4J 03 •H S *w > X S O CD J- *U o z UJ o >, rH 4-i T3 •H M M C 03 O -H 'O o mod o •H 03 mean temperatures Michigan in the v represent 4- 2 st o 1 CO U3 FIG. 34. Weighted gear types from Lake 1977. Vertical line (0) 3amvu3dW3i 105 including one, 28 mm long YOY caught at beach station T (influenced by- Pigeon River) , five yearlings and one adult were collected from Pigeon Lake* All these smelt probably immigrated from Lake Michigan. As mentioned earlier, spawning of smelt often takes place in tributary streams. Preliminary observations on the adult fish catch in April and May 1978 and 1977 larval fish data showed no evidence of extensive smelt spawning in Pigeon Lake. Occurrence of a YOY at beach station T (influenced by Pigeon River), however, suggested that some incidental spawning may occur in Pigeon Lake or Pigeon River. YOY from the April-May spawning reached a modal length of 40 mm in August, 50 mm in October and 60 mm in December (Appendix 4). A similar growth rate of YOY smelt was observed in Gull Lake, Michigan (Burbidge 1969). In southeastern Lake Michigan, YOY appeared to grow slightly faster, reaching a modal length of 40 mm in August, 45 mm in September and 54 mm in October (Jude et al. 1975)* A much faster growth of YOY smelt was reported from different areas in western Lake Michigan . The average calculated length of smelt at the end of the first year of life was 86.7 and 84 mm for males and females collected at Zion, Illinois and 83 and 82.5 mm for males and females collected at Two Rivers, Wisconsin (Robinson 1973). Yearlings in our study area attained a modal length of 80 mm in June. This size was comparable to the modal length of 65 mm reached in September by yearlings near the Cook Plant (Jude et al. 1975). Rainbow smelt were reported to serve as food for predatory fishes in Lake Michigan. They occurred in 28$ of the stomachs of immature lake trout collected from this lake (Wright 1968). In our study area, smelt were occasionally found in stomachs of lake trout and brown trout. They appeared, however, to be far less important than alewiv.es as forage for these predatory fish. Catches of smelt at station L (6 m - s.) and at station C (6 m - reference) appeared to be similar throughout the study period (see STATISTICS) . Apparently the present thermal discharge did not affect the distribution of smelt around the 6 m station during the times of our sampling. Summary — Rainbow smelt were the second most abundant species caught in Lake Michigan. There appeared to be no resident smelt population in Pigeon Lake where only a few specimens were collected. Spawning probably took place during April and early May in the shallow areas of Lake Michigan. Pigeon Lake was apparently not utilized as a spawning ground by smelt. YOY smelt occurred mostly between 6 and 18 m and were first caught in July by trawls. A few were also taken in seines. YOY catches peaked in August, then declined through summer and fall probably as a result of L06 offshore movements. High catches of YOY in December suggested that they may periodically return to inshore waters in late fall* Yearling smelt were usually found between 6 and 15 m. Monthly catches were highest in June and declined substantially in July and the rest of summer as yearlings moved offshore. They were relatively scarce in the study area during fall. Adult smelt were caught in small numbers between 6 and 15 m. These low catches may be due to the small adult population in the inshore waters during summer as most large smelt migrated offshore shortly after spawning. Upwelling of cold water may, however, induce them to return to shallow water during summer. Like yearlings, adult smelt rarely occurred in the inshore areas during fall. Adult and yearlings were caught mostly in water temperatures from 6-14 C. Most YOY occurred at water temperatures of 6-20 C. Adults and yearlings exhibited diel vertical migration, being found mostly near the bottom during the day and near the surface at night. Spottail Shiner — Introduction — Spottail shiners are minnows found in shallow areas of large lakes and rivers; in North America they are distributed from portions of Canada south to the United States, from Georgia in the east to Iowa and Missouri in the west (Scott and Crossman 1973). They are found in all the Great Lakes and many of their tributaries (Hubbs and Lagler 1964). In several midwestern lakes, spottail shiners serve as an important forage and bait species. They are the main item in the diet of walleyes in Lake Erie (Parsons 1971) and Lower Red Lake, Minnesota (Smith and Kramer 1964). Spottail shiners are also utilized as food by smallmouth bass (Surber 1939) and northern pike (Hunt and Carbine 1951). Although they are abundant in Lake Michigan, spottail shiners appear to play only a minor role as forage for larger predatory fishes (Wells and House 1974, Jude et al. 1975, Jude et al. 1979). Comprehensive studies on the life history of this species are rare. The first research work on the biology of spottail shiners in Lake Michigan was an investigation on their age, growth and food habits conducted in Little Bay de Noc (Basch 1968). From the results of experimental trawling, Wells (1968) described their seasonal depth distribution in the southeastern part of the lake. More recent studies on spottail shiner biology, life history and distribution were reported by Wells and House (1974) and Jude et al. (1975) in southeastern Lake Michigan. More research is needed to determine the ecological 107 significance of this minnow in the inshore fish community of Lake Michigan. Spottail shiners were numerically the third most abundant fish collected in our study during June to December 1977* In Lake Michigan 7883 spottails (10% of the total fish catch, Table 13) were collected by all gear; while in Pigeon Lake 4547 spottails were caught (22% of the total fish catch, Table 14). Although different fishing gear select for certain species and sizes of fish, the high number of spottails observed illustrates the heavy utilization of inshore waters of Lake Michigan and its tributaries during summer and early fall. Spottail shiners (like several other fish species in Lake Michigan; e.g., alewife, trout-perch, yellow perch) overwinter in deep water, enter the inshore waters in spring when water temperatures are -rising, concentrate in summer to spawn, then return to deeper water in fall (more discussion of this will follow). Jude et al. (1975) and Jude et al. (1979) found similar seasonal movements of spottail shiners off the Cook Plant, southeastern Lake Michigan (108 km south of the Campbell Plant). In Lake Michigan during the Campbell Plant study most spottails (83*8% of the total spottail catch) were collected by seining, while trawling contributed 8.7% and gill nets 7.5% (Tables 15, 17, and 18). This high proportion of the catch from seining resulted from the concentration of spottails along the beaqhes in summer and early fall. Seining also supplied the vast majority (99*9%) of spottails collected in Pigeon Lake (Tables 19 and 20). Although trawling was not performed in Pigeon Lake, seine catches are indicative of the summer. and fall concentrations of YOY spottails in the lake shallows. Small fish are also more vulnerable to seining because seine mesh size (bar measure 0.5 cm) was the smallest of any mesh in the gear we use. Our catch data showed spottails to be a benthic minnow as only one spottail was caught in surface gill nets. Seasonal Distribution — Seasonal distribution of adult and juvenile spottails was analyzed by discussing monthly catches. Because sampling was initiated in June, only summer, fall and early winter catches will be treated. Spottail distribution in southern Lake Michigan during winter and spring can be inferred from data in Jude et al. (1975) and Jude et al. (1979). The following is a brief summary of their winter-spring findings. During winter months (December, January and February) the bulk of the spottail shiner population in southeastern Lake Michigan was in water deeper than 9 m. There appeared to be some movement of spottails to 9 and 6 m during winter. Spottail shiners (162 fish) were impinged at the Campbell Plant during December 1974, and January, February 1975 (Consumers Power Company 1975), also indicating that some spottails remain inshore or in Pigeon Lake during the winter. Wells (1968) reported that spottails were most abundant between 18 and 27 m during February 1964 in southeastern Lake Michigan. Jude et al. (1975) found 108 the spring inshore migration to 9 and 6 m began in March and continued into April, By May most of the population had reached 6 and 9m* We believe a similar winter-spring distribution of spottails occurs in the Campbell Plant vicinity. Discussion of Campbell Plant data can now begin with catches in June. June — Spottails were caught in Lake Michigan in moderate numbers (559) in June. Night seining at station R (n. discharge) produced most of these fish (Fig* 35). At beach stations Q (s« discharge) and P (s. reference) some spottails were caught during night seining, but in much lower numbers. This spatial difference may have been caused by the plant fs discharge warming the water at station R. Water temperatures during night seining in June were 10.6 C at R, 8.0 at Q and 9-5 at P. Wells (1968) and Jude et al. (1979) have indicated that spottails preferred warmer waters in Lake Michigan. In contrast to high night seine catches, only one spot tail was caught in day seines (Appendix 5). All sizes of yearling and adult spottails (40-140 mm) were caught in seine hauls, with the majority being in the 90 to 130 mm range (Fig. 36). While seining indicated spottails were in the shallowest depths at night, gillnetting and trawling at deeper stations in June revealed few fish present. Although all trawl catches were low compared to seine catches, highest trawl catches occurred during the night at 6 m (Fig. 37). Some spottails were trawled during the night at 9 m (four fish) and 12 m (three fish), but no spottails were found at 15 m. During the day spottails were only trawled at 6 m, although there was an incidental day catch of three fish at 21 m (Fig. 37). Like seine catches, all sizes of yearling and adult spottails were caught during June trawling with the majority being adults from 100-120 mm (Fig. 38). The only spottails caught by bottom gill nets in June were at 1.5m (Fig. 39). Night gill nets were not set at any depth in Lake Michigan during June due to weather problems. Size range of gillnetted spottails was 1 10-130 mm, except for one fish in the 40 mm size group (Fig. 40). High concentrations of adult spottails in June at night were probably the result of spawning activities. Gonad development data indicated most spawning in Lake Michigan occurred in June and July (Table 26). Our plankton net catches of spot tail larvae in Lake Michigan were highest in late July; also some larvae were caught in early July (see FISH LARVAE AND ENTRAINMENT STUDY - Spottail Shiner). These larvae also indicated a June and July spawning period. Jude et al. (1979) at the Cook plant also found that spottails during 1973 and 1974 spawned in June and July. In addition, Wells and House (1974) found that spottails spawned in late June and July 1964 in southeastern Lake Michigan (off Saugatuck, Michigan). Fish were at depths from nearshore to 9 m during the spawning season and spawning was heaviest in the shallow portion of the depth range. 109 □ day ■ night Station R June July August September October November 2777 700 «» June July August September October November 700- Station P June August September October November MONTH FIG 35. Total number of spottail shiner caught in duplicate seine hauls in Lake Michigan near the J. Ho Campbell Plant, eastern Lake Michigan, June - November 1977. no I-S 5 23 i -8 1 £ S i HSU -ON c 3 C7> S- 3 TJ CO 3 03 • 03 CD CTJ C -r- •r- -C OJ u CO «r- 2: a; +-> od 03 -^ a «3 a. c 3. i- C CO •i— 03 3 C 03 03 U r— Cu S- ■ fvCVB^BER FIG, 36. (continued) While we caught few spottail larvae in Lake Michigan during June, moderate numbers were caught in early and late June in Pigeon Lake* This early occurrence of larvae causes us to speculate (because no sampling occurred in May) that spottails spawned in Pigeon Lake during May. No adult spottails were caught in Pigeon Lake during June and only five were collected from July to December (Appendix 4). Earlier spawning in Pigeon Lake than in Lake Michigan may have been the result of warmer spring water temperatures available in shallow Pigeon Lake. July — In Lake Michigan twice as many spottails were caught in July (1107 fish) compared to June (559 fish). Most of the July Lake Michigan catch came from seines, 97$, while gill nets contributed 3$. No spottails were trawled in July. As in June, spottails caught in Lake Michigan during July came mostly from night seine hauls. July night seine hauls at station P (s. reference) contained the most fish, but moderate numbers were also caught at Q (s. discharge) and R (n. discharge ) ( Fig . 35 ) . Water temperature was the highest at beach station Q (20.0 C) compared with R (17*0 C) and P (16.0 C) although more fish were caught at station P. It appears that the plant's present discharge was elevating the temperature at Q, but spottails were not attracted to the warmer water in the beach zone as occurred in June. Possibly spottail distribution differences as indicated by seine catches were also influenced by schooling behavior of this species. Schooling by spottail shiners was documented by Nursall and Pinsent (1969) and Nursall (1973) in Beaver Lake, Alberta. Day seine catches in July were lower than night catches, but moderate numbers of spottails were still caught (Fig. 35) « While seine catches showed spottails were in the beach zone during the day and especially at night at all stations, the only other deeper station where spottails were caught was 1.5 m. A night gill net at station A (1.5 m - s.) caught 40 adult spottails (Figs. 39 and 40). 112 Station □ day ■ night ND = no data L (6m-N) 100 « 50 . 100 H(21m-S) 50 ■ 0 AUGUST SEFTE3ER OCTOBEH NOVEMBER DECEMBER 3D »D SO AUGUST SEPTEMBER OCTOBER NOVEMBER DECEMBER G(l8m-S) 50 F(l5m-S) * - E(l2m-S) " o 100 D (9m-S) 50 C (6m-S) » ' B (3m-S) 50 . HO !fO 80 AUGUST SEPTEMBER OCTOBER NOVEMBER DECEMBER O o 55 JW»« JULY AUGUST SEPTEM3ER OCTOBER NOVEMBER DECEMBER 3-' ~ H H M JUBE JULY AUGUST SEPTE3ER OCTOBER NOVEMBER DECEMBER B -. H JUKE JULY AUGUST SEPTEMBER OCTOBER NOVEMBER DECEIVER JUKE JULY AUGUST SEPTEM3ER OCTOBER NOVEMBER DECEMBER HO NO KD ND SO ND NO NO JULY AUGUST ■SEPTEMBER OCTOBER MONTH NOVEMBER DECEMBER FIG 37. Total number of spottail shiner caught in bottom travls fished during day and night once per month June through December 1977 in eastern Lake Michigan in the vicinity of the J. H. Campbell Power Plant. 113 HSU °0K CD s- 3 73 3 (T3 • •r— rd 03 L0 CD JZ JZ CJ ^^ CD CD 3 -*: • CT CD -J JZ S- O) 1 -t- c CD cnr^ c cr> CD t— * CO CO o CD .a >> E «3 CD "O U CD II Q O S-X? CD CD s- en o CM- •i- s- r— CD CL Q. E fO CD •i— en e •t- rd C CO o o S 0a U. -M il II * + llU - - - - - - - I 1 " ( ■ 1 1 . - J- . 1 • 1 c 1 ' cz ' ** 1 1 ! 1 HSU 'OK OQ S -S i-a HSU 'ON o CO CD w CT 115 i ( c i r . ■ - i. 1 ' ! 1 c c 1 - cz (_- HH ' i. 1 ; — , — , — , • .«.. .. < O <_Dc5 HSI1 'ON en V2 * e rS = HSII 'ON C o 00 en LL»^ o 116 Station L (6m-N) E(12m-S) D (9m-S) o < H O H C (6m-S) B (3m-S) 30- 40- 30 20- 10- 30- 40- 30- 20- 10' a 30- 40-| 30. 20- 10- 0- 30- 40 30. 20 10- 0 a day ND _ no data ■I night AUCUST SEPTEMBER OCTOBER NOVEMBER DECEMBER JULT AUCUST SEPTEMBER OCTOBER NOVEMBER DECEMBER AUGUST SEPTEMBER OCTOBER NOVEMBER DECEMBER 50- JOBS JUL' 40- 30- 20. 10. 0 XD A(l.5m-S) JCHI JULY AUGUST SEPTEMBER OCTOBER NOVEMBER DECEMBER MONTH FIG 39. Total number of spottail shiner caught in bottom gill nets fished during day and night once per month June through December 1977 in eastern Lake Michigan in the vicinity of the J. H. Campbell Power Plant. 117 HSU "ON O ! °4 "1 -^ O 03 J2 -J CD C 4-> *« o3 CD U +-> •r- (/> r— 03 CL CD 3 "O * 4-> C C •r- 03 r-"* 4-> Cl. JC C7>r— =5 r- 03 CD U -O cl S- E (D •M =£1 O 4-> CL (/I S- 03 S~ CD o c l*~ sz 00 03 E O 03 «i- $- JC O) o O «r- ■p s: • in T3 •r- CD CD JT -^ E 03 S- >>-J O U H- c c S- CD 't- CD is • CL crr^ 4-> cd r^ -c O) u as o> C <4- t-4 8r— •T-o 1 C J—0 JZ &. Q» 4-> CD II E Cfr-Q 03 C E CD CD ■ 1S) -J > -M O » •r— 2 O T5 C ^ «M O II 2: 2*S □ n LU ^ * us Is i. < HSU 'ON 03 i a B (3m-S) o 60 1 (1.5m-S) 301 too TOTAL LENGTH (ram) novoter FIG. 40. (continued] An interesting aspect of these data is that although spottails were occupying slightly deeper depths at night, seine catches were lower during the day. We suspect that daytime net avoidance was occurring . It seems very unlikely that fish moved along shore away from seine sampling stations. All sizes of juvenile (yearling) and adult spottails were caught by day and night seine hauls in Lake Michigan during this study (Fig. 36). Size distribution was bimodal with a peak at 60-70 mm and one at 100-110 mm. Based on age data given by Wells and House (1974) for Lake Michigan spottails, those captured by seine during the Campbell study would most likely be age-group 1 (60-70 mm) and age-groups 2 and 3 (100-110 mm). One small (22 mm) spot tail was seined during the day in July at beach 120 TABLE 26 . Monthly gonad conditions of spottail shiners caught in Lake Michigan near the J. H. Campbell Plant, eastern Lake Michigan, during 1977. All fish examined in a month were included except poorly received specimens. Gonad condition Jun Jul Aug Sep Oct Nov Dec Slight development 2 36 47 60 33 7 9 Mod. development 23 27 12 20 13 16 11 Males Well developed Ripe-running Spent 8 1 2 1 1 10 Slight development 35 60 56 7 3 8 Mod . development 10 15 5 26 22 4 16 Females Well developed Ripe-running 88 4 1 4 Spent 4 14 3 10 Absorbing 3 Immature 27 92 97 223 69 43 98 Unable Co distinguish 17 37 8 17 1 5 station Q. This fish was obviously a Y0Y. Many small fish (20-40 mm) were seined in Pigeon Lake in July (Fig,. 41) and we believe these fish were also Y0Y. This July occurrence of Y0Y predominantly in Pigeon Lake supports our hypothesis that some spottails spawned in Pigeon Lake in May approximately 1 or 2 months before most spawning occurred in Lake Michigan. Jude et al. (1979) also found some spottail larvae around the Cook Plant in May. In contrast to Lake Michigan seine catches, day seine catches of spottails in Pigeon Lake were larger tham night catches (Fig* 42). Schooling behavior was responsible for some of these catch differences. Approximately 89? of the day seined spottails came from one seine haul at beach station S (influenced by Lake Michigan). Station S was a preferred habitat for Y0Y spottails in Pigeon Lake. No spottails were seined in July at station T (influenced by Pigeon River) and only a few were seined at station V (undisturbed Pigeon Lake). Possibly fish were avoiding areas of Pigeon Lake that had high densities of aquatic vascular plants. August — Total number of spottails caught in Lake Michigan increased in August (1444 fish) compared to July (1207 fish). As in 121 •a -8 ^ HSU 'UK 8 to -5J f-§ H. ON to HSIi "ON o> s- 3 °o to c r— - c 3 03 03 an -C JE a; CJ c •r- Of» s: CD to CD J^ CD 03 -M -J 03 a e °f— s- r° 4-> C JC 03 a> r—" 3 Ol 03 u p— r» S- CD CU -Q G GL op=> E JS H3 to O 1—* . •f-3 3= *3 -M e +j '"D O Q» CD CO JC 4-> £- O &- <+~ 03 CD to C E 03 CD £» -^ CD 03 O _J +J to C •r— O JSZ CD O) >> ««— > u a. c c 3 •1— e CT 4-> cjnx: s- r^ a> tj_ cr> •!- i <-* c -C 4-> S- II CD ^ — C ^ ■ CD E ™ C-J CD > O ©• sz >* r— 03 ^f O "O 4J II • CD o C -- u_ o a 122 1200-1 i 8001 TOTAL LENGTH (mm) OCTOBER FIG. 41. (Continued) NO/EMBER June and July the majority (90?) of fish caught in August were seined. In contrast to June and July, more fish were seined during the day than at night (Fig* 35). Day seines at station R (n* discharge) contained the most fish. These day-night catch differences can be attributed to size-class variation among the fish. At Lake Michigan beach station P more adult and yearlings were caught than at station Q and R where YOY predominated (Fig. 36). Adults and yearlings were caught at night while YOY were caught during the day. Seine catches in Pigeon Lake only occurred at beach station S (influenced by Lake Michigan) where YOY were also more abundant during the day than at night (Fig. 41). Bottom gill net catches of adults (our gill nets do not effectively sample YOY and small yearling spottails) in Lake Michigan showed most were at 1.5 m with a few out at 3 m during the day (Fig. 40). At night, gill nets showed a progressive decline in abundance of adult spottails from 1.5 m to 12 m (Fig. 40). While night gill nets were collecting adult spottails, only two fish were caught by night trawling in August (Fig. 37). It is possible that some spottails can evade the trawl, but we suspect the efficiency of gill nets in capturing spottails was a result of the long fishing time (approximately 12 hr compared to 10 min for trawl hauls). Spottails probably move from shore to deeper water at sunset and back during or near sunrise hours, near the time when gill nets would still be set. September — The September catch of spottail shiners was the largest monthly catch in both Lake Michigan (4018 fish) and Pigeon Lake (2333 fish) during 1977. Day seines made up 90$ of the Lake Michigan total catch with 80$ of this day catch occurring at beach station Q (Fig* 35). Warm water from the plant's discharge apparently attracted spottails to station Q (s. discharge); a similar attraction of spottails to station R (n. discharge) occurred in June. Water temperatures recorded during September day seining were 15.6 C at Q, 12.2 C at R (n. discharge) and 11.1 C at P (s. reference). 123 O day SB night 500 , 400 300 - 200 - 100 J UN Station V JUL AUG SEP OCT NOV 500 . 400 O S5 300 H 200 - O H 100 -^ 0 I_ J UN Station T JUL AUG SEP OCT NOV 1661 500 . 400 - 1321 ijPg Station S 300 - 111 200 - ill 100 - 0 - 9 Hf-1 J UN JUL AUG SEP OCT trov M lONTH FIG. 42. Total number of spottail shiner caught in duplicate seine hauls in Pigeon Lake near the J. H. Campbell Plant, eastern Lake Michigan, June - November 1977. 12k The majority of spottails caught by September day seining in Lake Michigan were smaller fish from 30-90 mm (Fig. 36). Most of these fish were YOY, but some may have been yearlings. Suspected early spawning in Pigeon Lake confounded interpretation of ages from length sizes. YOY from southeastern 'Lake Michigan were 30-60 mm in September 1974, while yearlings were 70-100 mm (Jude et al . 1979)- These data would indicate that in the present study, spottails from 30-60 mm were YOY and those from 70-90 mm were yearlings, but spottails from early hatchings in Pigeon Lake might be in the 70-90 mm range by September. 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 (Figs. 39 and 40). At night, spottails extended their depth range out to 12 m and probably deeper [a few were trawled at 15 m (Fig. 37)]. Day and night trawl hauls caught few adult spottails, but some yearlings were caught at 3 m (Fig. 38). During September only YOY were seined in large numbers in Pigeon Lake at beach station S (influenced by Lake Michigan) (Fig. 41). In contrast to July and August, more YOY were seined at night in September (Fig. 41). We can only conjecture that schooling behavior caused this large night catch, but both night seine hauls contained large numbers of YOY spottails. October — Number of spottails caught in Lake Michigan during October (366 fish) declined drastically compared with the September catch (4018 fish). Part of this decline was the result of less fishing effort in October (gill nets were not set because of storms.) , but most was due to the annual migration of spottails to deeper water. Wells (1968) recorded spottails at 6-31 m in southeastern Lake Michigan during October, with highest numbers at 22 and 27 m. Jude et al. (1979) also indicated that spottails migrated to deeper water in the fall in southeastern Lake Michigan. Few spottails (52 fish) were caught by seining in the Lake Michigan beach zone; most fish were YOY and yearlings (Fig. 36 and Appendix 5). Seining in Pigeon Lake also showed most spottails had left there by October. Most of the population was in the deeper water of Lake Michigan . Trawl samples in October showed no adult spottails were in the sampling depths during the day (Fig. 38). From Wells (1968) trawling study we surmised that adults were in deeper water outside our study area. At night some smaller adults moved into the trawling depths with most being found at 9 and 6 m (no trawling occurred at 3 m) . Yearlings also followed this day-night pattern. Most YOY were apparently in deep water during the day in October; highest day catch occurred at 21 m, but some were caught at 6, 9 and 15 m (Fig. 38). At night some YOY moved 125 into the study depth zones. Night trawl catches occurred from 6-15 m (no trawling occurred at 21, 18 and 3 in) . We suspected that YOY were also at 21, 18 and 3 m during the night. November, December — The November catch of spottails (88 fish) was the lowest of any sampling month. As was found in October, the bulk of the population was in water deeper than 21 m. Some fish did enter the study depths at night (Figs. 37 and 39). Also a few YOY spottails were still found in Pigeon Lake (Fig. 41). This pattern continued in December although more fish were caught ( 198 fish). In Lake Michigan, fish (all sizes but mostly YOY) were caught by day and night trawling in December (Fig. 38). Although the bulk of the population was in deeper water, some individuals entered the inshore waters of eastern Lake Michigan during late fall and early winter. Jude et al. (1979) also found the same spatial distribution of spottails in southeastern Lake Michigan. Impingement data from the Campbell Plant during 1974-1975 (Consumers Power Company 1975) showed some spottails were probably present during fall and winter months in Pigeon Lake. Temperature-Catch Relationships — Smaller spottails were caught at higher temperatures than larger fish in both Lake Michigan and Pigeon Lake (Fig. 43). Apparently age influences temperature selection by spottails. Jude et al. (1979) also found a similar size-temperature relationship for spottail shiners caught in southeastern Lake Michigan. Standard deviations around the mean did indicate large variation among sizes (Fig. 43) . Approximately 69$ of our spottail catch in Lake Michigan occurred between 11-17 C. Jude et al. (1979) found the majority (74?) of their spottail catch in southeastern Lake Michigan at temperatures from 18-27 C. Wells (1968) trawled most spottails at 13-22 C in southeastern Lake Michigan. These differences in relationships of temperature with catches were probably related more to water temperatures available to the fish rather than to strictly temperature preference of the fish. Spottails preferred shallow depths and apparently did not move from the shallows extensively following movements of warmer water. We suspect that spottails preferred warmer temperatures in Lake Michigan. Other Considerations — Spottails were not heavily preyed upon by piscivorous fish in the study areas as no spottails were found in stomachs of predatory fish examined. Jude et al. (1979) also found that spottails were not preyed upon to any great extent in southeastern Lake Michigan . Summary -- . Spottail shiners were the third most abundant fish collected from June to December 1977 in the vicinity of the J. H. Campbell Plant. During summer and especially early fall they were seined in large numbers from Lake Michigan and Pigeon Lake, but all 126 30 T 2 5 I < tr 2 UJ Pigeon Lake • 20 . 15 - • • » 10 - 1 . 1 5 - 0 50 !00 LENGTH INTERVAL (mm) l 50 30 25 2 0 - (Z UJ a. 2 10 + Lake Michigan H- 50 100 LENGTH INTERVAL (mm) i50 FIG. 43. Weighted-mean temperatures for 10 mm length intervals of spottail shiners caught by all gear types from Pigeon Lake and Lake Michigan in the vicinity of the J. H. Campbell Plant, eastern Lake Michigan, 1977. Vertical lines represent + 2 standard deviations. 12? catches declined in late fall and early winter as fish migrated to deeper water . All age groups were caught in Lake Michigan (84? of the catch by seining, 9% by trawling, and 7% by gillnetting) , while predominately YOY were caught in Pigeon Lake (99$ by seining). Gonad data and catch data of larval and YOY spot tails indicated that spottails spawned in Lake Michigan during June and July from 9 m to shore; spawning was probably heaviest in the nearshore area. Early occurrence of larvae (early June) and YOY (July) in Pigeon Lake suggested that spottails spawned there in May. The nearshore area of Lake Michigan and the west side of Pigeon Lake served as nursery areas for spottail shiners. From June through September adults and yearlings were concentrated between 1.5 and 3 m during the day in Lake Michigan . At night fish were dispersed from shore to 12 to 15 m. Only during July, when spawning was probably at a peak, did spottails concentrate day and night in the beach zone . September day catches showed spottails were segregated by size and depth; adults were in the beach zone to 3 ni, yearlings from the beach zone to 1.5 m and YOY in the beach zone. In October, November and December the bulk of the spottail population was in water deeper than 21 m, but some individuals entered study depths at night. Smaller spottails were caught at higher temperatures than larger fish; 69$ of the fish collected in Lake Michigan occurred at water temperatures of 11-17 C. Only one spottail was caught by surface gillnets, which demonstrated the fishes' benthic habits. Spottails in the study area were not heavily preyed upon by picivorous fish. Yellow Perch — Introduction — The yellow perch is a highly adaptable percid fish which occurs throughout most of northern North America. Habitat for this species includes small or large clear lakes with moderate vegetation, as well as quiet rivers (Scott and Crossman 1973)* In Lake Michigan, the yellow perch is abundant in protected bays, notably Green Bay, and moderately abundant in shoreline areas with depth less than 40 m (Wells and Mclain 1973). Historically, the abundance of yellow perch in Lake Michigan fluctuated greatly. Declines in population have been related to the spread of non-native alewife (Wells 1970) and, although the exact mechanisms involved are not understood, Wells (1977) has suggested several possible causes. Generally it is believed that the alewife inhibited the reproduction of yellow perch to some degree. Development of the strong 1969 yellow perch year class following the massive 128 1967-1968 die off of alewives further suggests the interdependency between yellow perch and alewife populations. The commercial and recreational importance of yellow perch has resulted in considerable study of its life history, in other parts of its range (Scott and Crossman 1973) and will not be considered here. Comprehensive studies of the life history of this species in Lake Michigan are notably lacking. Studies by Wells (1968), Brazo et al. (1975) and Jude et al. (1975) elucidated the seasonal depth distribution of yellow perch in east-central and southeastern Lake Michigan, but it is evident that more study of this important species is needed to better understand its role in the ecology of the lake. Yellow perch are common to abundant near the Campbell Plant, comprising 11.9? (2459 fish) of the catch by number in Pigeon Lake, and 1.6% (1254 fish) of the Lake Michigan catch (Tables 13 and 14). Bottom gill nets made up 6% of the catch in Pigeon Lake (Table 14 and 19) and 57% of the catch in Lake Michigan (Table 13 and 15)- Seine hauls comprised 94% of the Pigeon Lake catch (Table 14 and 20) and 26% of the Lake Michigan catch (Table 13 and 18). Trawling, which was only performed in Lake Michigan, accounted for 16% of that catch (Table 13 and 17). Seasonal distribution — June — Sampling near the J. H. Campbell Plant began in early June. At this time, day trawl samples as well as day and night bottom gill net samples from Lake Michigan indicated yellow perch were generally at depths of 12-21 m, with some taken at shallower depths (Figs. 44 and 45). No yellow perch were taken by seine in early June indicating their absence from the beach zone. Wells. (1968) observed that adult yellow perch began to move into shallow water (6, 9 and 13 m) in late May during 1964 in southeastern Lake Michigan. Brazo et al. (1975) found that most yellow perch were in deeper water (24 m) during early April 1972 in east-central Lake Michigan (near Ludington) but migration of male perch into shallow water 6-12 m, had occurred in late May when water temperatures had reached 6-7 C. It is evident from our data that this inshore movement had already occurred in the area of the Campbell Plant prior to initial sampling; in June. Yellow perch present at this time were primarily longer than 150 mm, 2 yrs and older, (Scott and Crossman 1973) but some smaller perch (< 100 mm - probably yearlings) were also observed at 12 and 15 m (Fig. 46). Water temperatures in the area of the Campbell Plant during early June sampling ranged from 7.4-1 1.7 C (Appendices 1-3). Movement of yellow perch into shallow water in spring is usually associated with spawning. We observed ripe and ripe-running perch in our Lake Michigan catches in June (Table 27). Some success of spawning in Lake Michigan near the Campbell Plant was apparent from the presence of larval yellow perch in late June at south 129 Station D day ■ night ND = no data L (6m-N) 10- ■H(21m-S) 10- G(l8m-S) » FU5m-S) 10- ■ H H E(l2m-S) io- 0 D (9m-S) 10' o C (6m-S) w 0 20i B (3m-S) 10 JUM JULY AUGUST SEPTEMUEH OCTCRER HOVEMBFJI SO SO WD JURt JULY AUGUST SEPTEMBER OCTOBER SOVEHBER DECEMBER 5D TO SB AUGUST SEPTEMBER OCTOBER SCVEMBER DECEMBER JU5E JULY AUGUST SEPTEMBER OCTOBER 50VEMSSR DECEMBER JU1E JULY AUGUST SEPTEMBER OCTOBER 50VEM3ER DECEMBER , , 1 fH AUGUST SEPTEMBER OCTOBER SOVEMBSR DECEMBER JULY AUGUST SEPTEMBER OCTOBER SOVEMBSR DECEMBER SD ID SD 3D MD TO SD JULY AUGUST SEPTEMBER OCTOBER SOVEMBER DECEMBER MONTH FIG, 44. Total number of yellow perch caught in bottom trawls fished during day and night once per month June through December 1977 in eastern Lake Michigan in the vicinity of the J. H. Campbell Power Plant 0 130 Station L (6m-N) E(l2m-S) D (9m-S) Sm-S) o z H O H B (3m-S) A(l.5m-S) 30 40 30 20 10 0 . .50 40 D day ■ night ND = no data ^ Al'Wftl SEPTKMBKR OCTOBER NOVEMBER DECEMBER 30 -J 20 10 . 0 30 -, 40 30 . 20 10 0 ho m> MONTH FIG. 45. Total number of yellow perch caught in bottom gill nets fished during day and night once per month June through December 1977 in eastern Lake Michigan in the vicinity of the J. H. Campbell Power Plant 131 HSU *0N C=J S m " HSU 'ON « e o +J CD c 3 ra en c •r> ^-v S- a s 3 -o X C-l CO ^ >-: f— »> 55 ! ID 3 "" — D 03 o _^ sz c < 03 s p— CT 5 S histograms for yellow perch caught in duplicate traw gan near the J. H. Campbell Plant, eastern Lake Michi CD E z LU >>•»- o 5 —"3 O £ <*- 0 J c u 5r "^ O) T- 0) Q) < 3 S © Cl j= 3 CT +J s- 0) poo •r- S» I -J £ •— r^ •r- =-j r^ -M r- cn JZ CL r—4 cn s •■ >> •r- 03 2 *- 03 sz to *3* 0) -o JD O O E n s: 2: ,« ^ CD o a it ii U« Q * + 132 2 °* HSU "OH * k CD do oa s o HSU 'ON CD 133 f-§ HSU *0N 03 : G£ -I CD c o - 2 « HSU e0N <3" 2Q S CD 134 L (6m-N) 18 - 9 - 4 18 - H + (21m-S) 9 • 18 - G + (18m-S) 9 - F* (15m-S) z 18 - 9 - 0- 18 - 9 - (12m-S) n 11 „ 18 • D (9a-S) 9 - T,,r"'" " -»- «— , 18 - c (6m-S) 9 - 0- 18 - B (3m-S) 9 - 0- . 1 , TOTAL LENGTH (mm) DECEMBER FIG. 46. (Continued) transect stations (see FISH LARVAE AND ENTRAINMENT) . In Pigeon Lake during June, both large and small yellow perch were most abundant at beach station T (influenced by Pigeon River). High catches of YOY at station T during June probably reflects the suitability of this densely vegetated habitat for spawning and rearing, and suggested an April spawning period in Pigeon Lake in 1977* Gonad data of yellow perch from Pigeon Lake in June (Table 28) indicated that some spent individuals were present. The majority of adults had slightly developed gonads, indicating that regeneration of gonadal tissue following 1977 spawning was beginning. April spawning in 1978 was indicated by observations of a few masses of yellow perch eggs near beach station T, as well as observations of perch larvae in entrainment samples in April and May 1978. Larger perch ( > 125 mm) at Pigeon Lake openwater stations during early June were more abundant in bottom gill net samples at openwater station M (influenced by Lake Michigan) than at station Y (influenced by Pigeon River). Greater abundance of yellow perch at station M may be due to the reduced amount of vegetation and 135 TABLE 27. Monthly gonad conditions of yellow perch caught in Lake Michigan near the J. H. Campbell Plant, eastern Lake Michigan, during 1977. All fish examined in a month were included except poorly received specimens. Gonad condition Jun Jul Aug Sep Oct Nov Dec Males Slight development 4 48 91 16 2 1 Mod . development 13 6 6 36 1 7 Well developed 11 33 25 Ripe- running 9 Spent 14 5 20 12 Slight development 7 50 68 27 Mod . development 1 27 1 Well developed 1 7 5 Ripe-running 3 Spent 6 8 4 Absorbing Females Immature 10 48 50 4 52 Unable to distinguish TABLE 28. Monthly gonad .conditions of yellow perch caught in Pigeon Lake near the J. H. Campbell Plant, eastern Lake Michigan, during 1977 • All fish examined in a month were included except poorly received specimens. Gonad condition Jun Jul Aug Sep Oct Nov Dec Slight development 25 43 52 17 15 7 Mod. development 14 9 1 49 36 36 Males Well developed Ripe-running Spent 2 6 4 39 1 3 Slight development 50 30 46 29 13 5 1 Mod. development 17 12 4 38 30 38 1 Females Well developed Rip e-running Spent Absorbing 4 15 2 3 16 Immature 30 165 71 48 21 18 1 Unable to distinguish 5 1 3 136 great depth found at this station. Night catches of yellow perch at station M were noticeably smaller when compared with day catches, which may reflect a movement of yellow perch into shallower water at night or decreased nocturnal activity, SCUBA observations reported by Jude et al. (1975) indicated that yellow perch were generally inactive at night and hence had lower probability of being gilled. July — During July, yellow perch in Lake Michigan appeared most frequently at 6 m and less as indicated by bottom gill net samples (Fig. 47). Yellow perch greater than 175 mm were taken in trawls in July at 6 and 9 m (Fig. 46), which suggests inshore movement also confirmed by first appearance of yellow perch at Lake Michigan beach stations in July. At this time some small (25-45 mm) perch were seined at Lake Michigan beach stations P (s. reference) and Q (s. discharge) (Fig. 48). These perch were probably earlier spawned YOY from Lake Michigan. However, most yellow perch observed in seines at this time exceeded 100 mm in length. Bottom gill net data from Lake Michigan in July indicated that yellow perch were found near shallower depths (1.5 and 3-0 m) during the night and greater depths (6m) during the daytime. Jude et al. (1975) found yellow perch in southeastern Lake Michigan exhibited crepuscular movement - inshore at dusk, offshore at dawn. Bottom gill nets from Pigeon Lake in July contained relatively few perch compared with June catches (Fig. 49), however capture of YOY perch in beach seines at this time increased dramatically (Fig. 50 and Appendix 5), reflecting growth of many of the perch larvae observed in late June larval samples (see FISH LARVAE AND ENTRAINMENT) . As in June, catches at beach station T (influenced by Pigeon River) had notably more YOY than catches at other beach stations in Pigeon Lake; however seine catches at stations V (undisturbed Pigeon Lake) and S (influenced by Lake Michigan) exhibited a substantial increase in numbers of YOY yellow perch from June to July (Fig. 50). Highest numbers of larger perch were seined at station S. Decreased catches of larger perch at stations V and T may have been due to the increased vegetation observed there during July. Most adult perch caught at beach stations in Pigeon Lake in June and July ranged in length from 100-200 mm. August — August gill nets at Lake Michigan stations indicated that unusually high numbers of larger yellow perch were present at 3 and 1.5 m during the day (Fig. 47)? while very low numbers were taken in night gill net sets. Low numbers of large perch caught at beach stations during the day in August may have been due to net avoidance. Due to weather, trawl samples at 3 m could not be performed. However, trawls at 6 m in August (day and night) indicated unusually high densities of YOY yellow perch. Thus it appeared that during August the majority of 137 - ! c ■ G C 1 C " 1 I- c ! i • , < t 1 c 1 -8 -a s s 1 «~ s- 3 °o CO +■* CU C f- « r- c •r 03 cn a* "f E .s O o +j *(«*> 4-> S O jD cu o^ 3 CO T3 03 a; C ,,_ * 4-> 4-> C -C 03 O) f"=" 3 Q» 03 U e— p— JZ CD u -a &- a. CU E a «3 O .* HSU -ON cu • >>o s~ cu o sz <*=. 4-> CO $«, E 03 03 CU S- c CJJ o c -M 03 G co cn T3 •r» »r— CU x: jz E a i- >*'*- O a s: q~ - c: S. "O cu cu cu cu 3 j* • Ol E cr 03 +J s~ CU -J JZZ cn O i. a* c h- q- c ep-o .f- i. 1 •r-> c r— . CU JC CL GL +-> r^. 18 E - o^r^ 03 Oi £Z Ch ■ to c CU r-i •r-> -j 4-> r— s- jz: a O) o> E ^c «° >> •r- 03 i s 03 c to ^ CU T3 > o o o u z z: • z CD j-h 0 D H u U. 4J * + 138 - c c ( - 1. 1 . c 1 fi c 1 ! ' 4" fr c=f a < = i 1 i t J c 1 d t t ' • . . • z Ed JZ •r— -C to cd -^ CD 03 4-> -J 03 CJ c •r— s- r— ' • cd CL+J 3 CO T3 CO CD C •r— ♦» 4-> 4-> C JC 03 cn r— • 3 Q- rd U r— r- -C CD u jQ S- CL cd e a. CO O .3 | =3 r = § i § ° s § ° i HSU 'ON SB'S HSIJ 'ON CD • >•>-? i- CD O JC M- 4-> 00 S- E 03 03 CD &_ C a> o CZ +j» 03 to a? Of— •r-° JZ JZ u >> •r— os: c CD CD 3 «*: « Or A3 -M CD -J jz s~ CJ q_ C •r- 1 0r-» C JZ -M f^» II cnr^ JZ CT» ■ CD t-H _J CD .a >> CO fc= 03 ^f CD > 13 O II # 2: CD o a lUl § S 3 *0M HSU *ON HSU 'OK cn c: •r S- 3 "O -^ O fCJ jQ ,^J CD c 4-> s- 03 CD CJ 4J "n -r- 1 *-* C 4-i S- cn «*£ A3 JZ ■ JC CD r— * -J It CD ■ § 01 ra > "O O II Son 1U1+ X 300 -i 300 -i ISO -I TOTAL LENGTH (ma) OCTOBER FIG. 50. (Continued) TOTAL LENGTH NO/EMBER Lake Michigan) had catches comparable to those taken in August- Station T continued to have the highest catches compared with other Pigeon Lake beach stations. Slight decreases in gill net catches were observed at station M (influenced by Lake Michigan) in September when compared with August. Gill net catches of perch at station Y (influenced by Pigeon River) in September were comparable to those recorded in August. October — Dramatic decreases were observed in yellow perch catche;3 from all gear types used at Lake Michigan stations in October. No perch were present in the beach zone since none were caught in beach seine hauls. No gill nets were set in Lake Michigan during October. YOY occurred sporadically in Lake Michigan trawls during October with three being caught at 6 m and one at 15 m. Two larger yellow perch ( 1 60 and 167 mm) were caught at deep (12 and 15 m) stations. It was evident that offshore migration of adults had occurred by the time October sampling commenced. Jude et al. (1975) observed that offshore migration of yellow perch had occurred in September during 1974 in southeastern Lake Michigan . In Pigeon Lake during October station T was again the most productive area for YOY perch (Fig. 50). However these catches were substantially lower than in September. This decline may be due to natural mortality or more likely an age-related dispersal of YOY yellow perch from their rearing area as they grew older. Pigeon Lake beach station V (undisturbed Pigeon Lake) and beach station S (influenced by Lake Michigan) collections showed numbers of perch comparable to September catches. A slight decline in the number of large yellow perch caught in bottom gill nets at Pigeon Lake station M (influenced by Lake Michigan) and Y (influenced by Pigeon River) during October (Fig. 49) was observed. November — Bottom gill net samples taken during November from Lake Michigan indicated that adult yellow perch were most frequently caught in water less than 12 m (Fig. 47). Trawl data for November corroborated this distribution (Fig. 46) as YOY yellow perch were also trawled at 6 and 9m. No night trawling was performed at 3, 18 and 21 m. Beach 145 seine hauls at Lake Michigan stations in November contained some YOY yellow perch at station R (n. discharge), but no adults. These data, in addition to zero catch in beach seines in October, probably indicated that the beach zone was abandoned by yellow perch in colder months* In contrast yellow perch were still moderately abundant at all beach stations (particularly station T) of Pigeon Lake (Fig- 50) o Interestingly enough, adult and yearling perch caught in the densely vegetated, protected habitat of station T, were consistently smaller than perch caught at other Pigeon Lake beach stations* Gill nets in Pigeon Lake contained numbers of perch comparable to October values (Fig. 49). More larger yellow perch were caught at station M (influenced by Lake Michigan) than were caught at station Y (influenced by Pigeon River). December — December sampling in Lake Michigan was restricted to trawling, (out to the 15 m station) and indicated YOY perch were present in the area from 3-12 m. Absence of adult perch at the 3 to 12 m depth contours, with the exception of one caught at station L (6 m - n.), was indicative of their movement to deeper water. Jude et al. (1979) found that while adult yellow perch left the inshore zone and went to deeper water (deeper than 9 m) in winter months, YOY remained in shallower water. Only gill net sampling was performed in Pigeon Lake during December. No yellow perch were caught (only day nets were set) at station Y (influenced by Pigeon River), while some adult perch were collected at station M (influenced by Lake Michigan) (Fig. 49) . Temperature-Catch Relationships ~ Water temperature at time of capture for any one size group of yellow perch varied considerably. Larger fish tended to be captured at lower water temperatures in both lakes (Fig. 51). Findings of McCauley and Read (1973) supported the contention that age played an important role in temperature selection by this species. Older fish selected cooler temperatures than younger perch acclimated to the same temperature. Jude et al. (1979) noted that smaller perch (60-120 mm) were most often caught at water temperatures 16-19 C and larger perch (230-330 mm) at 14-17 C. Other Considerations — Abundance of yellow perch caught by trawling in the area of the Campbell Plant varied according to month, with significantly higher catches in August, September and December (see STATISTICS) . The increased number of perch caught in August was undoubtedly the result of YOYs recruited to the population vulnerable to the trawl samples. Recurrence of increased YOY numbers was observed in December when YOY apparently remained at 3-12 m and possibly overwintered there. Jude et al. (1979) found in southeastern Lake lk6 30 25 20 4 < 10 .. 50 100 Pigeon Lake 150 200 250 LENGTH INTERVAL (mm) 300 350 400 30 , 25 20 x 2 1- i 0 - 5 - 50 100 Lake Michigan 150 200 250 LENGTH INTERVAL (mm) 300 350 400 "**• "• Weighted-mean temperatures for 10 mm length intervals of yellow perch caught by all gear types from Pigeon Lake and Lake Michigan in the vicinity of the J. H.. Campbell Plant, eastern Lake Michigan, 1977. Vertical lines represent + 2 standard deviations. ikj Michigan that the bulk of the YOY remained in water deeper than 9 m in colder months, but some of the YOY population remained inshore in early winter* The increased number of yellow perch observed in September was primarily due to larger fish ( > 150 mm) which were in water 6 m and less at this time. Yellow perch usually exhibit an offshore movement to deeper water in autumn- Jude et al. (1979) suspected that in southeastern Lake Michigan during winter and spring, the bulk of the adult population was at depths somewhat greater than 9 m, but schools of perch enter the shallower depths (6 m or less) during the day. No night trawling was performed in September to compare with day trawls, but schools of perch moving into shallow water (3 m) during daytime may be a reason for the higher catch of adults in day trawls in September . Diel differences in trawl catches of yellow perch in the area of the Campbell Plant during 1977 were not significant. Jude et al. (1975) reported that from June to August in southeastern Lake Michigan yellow perch were more vulnerable to trawls during the day than at night . Summary — Yellow perch were abundant in the area of the J. Ho Campbell Plant ranking fourth numerically in catches of adult fish in both Lake Michigan and Pigeon Lake. Seasonal changes in abundance of yellow perch in the surrounding Lake Michigan area, were similar to those observed by other researchers in southeastern Lake Michigan. Yellow perch moved inshore in late spring for spawning* During summer, there was some indication of a nocturnal offshore movement and an inshore movement during the dayc Perch remained within the sampling depths (0-18 m) until late autumn when there was an apparent movement of adults to more offshore water. December sampling indicated that YOY remained within the sampling area until and possibly throughout the winter. Pigeon Lake appeared to sustain a considerable population of yellow perch. Spawning time of yellow perch in Pigeon Lake was found to occur earlier than in Lake Michigan and probably commenced in April during 1977. YOY comprised the majority of perch caught in Pigeon Lake throughout our sampling period and indicated extensive use of that area for spawing and as a nursery. Adult yellow perch were generally more abundant in the easily seined shoreline compared with the openwater gill net stations . Golden Shiner -~ Introduction — Golden shiners live in clear, weedy quiet water with extensive shallow areas. This species swims actively in schools, covering large areas just off the bottom (Scott and Grossman 1973). They feed at mid-water or the surface and help control mosquitoes to some extent (Becker 1976). The golden shiner is endemic to much of North America east of the Dakotas and Texas and south of the Canadian lk8 Maritime Provinces. It has been introduced to many other areas, especially the western United States. Seasonal distribution — The golden shiner was the third most numerous fish caught in Pigeon Lake making up 12.6$ by number of the fish captured. None were collected in Lake Michigan. In all, 2615 golden shiners were collected from June through November (Tables 13 and 14). These fish ranged in length from 23 to 170 mm, with most between 40 and 100 mm. Only 11 golden shiners were gillnetted in Pigeon Lake (Fig. 52 and Table 19) • All were caught in the Pigeon River area of the lake at station Y; none were collected at station M (influenced by Lake Michigan). Generally only the larger specimens ( > 100 mm) were caught in gill nets. Seining at Pigeon Lake beach stations resulted in the capture of the remaining 2604 golden shiners taken and appeared to be the most efficient means of sampling. Most golden shiners (92$) were seined at station T (influenced by Pigeon River), with the remainder being seined at stations S (influenced by Lake Michigan) and V (undisturbed Pigeon Lake) (Fig. 53). Sampling in June indicated that moderate numbers of adult golden shiners were at beach station T (influenced by Pigeon River). Absence of ripe and ripe-running adult golden shiners in June samples (Table 29) suggested the possibility that spawning of this species had occurred prior to our sampling. Spawning by golden shiners in the area had occurred, since larvae were found in late June and July larvae samples (Appendix 8) . Golden shiners usually spawn from June to August when water temperatures reach 20 C (Becker 1976). Some mature by their second summer when they have attained a length of 64-89 mm (Scott and Crossman 1973)* This species scatters and abandons eggs over filamentous algae (Scott and Crossman 1973)* Rooted vegetation will suffice in the absence of filamentous algae but some type of aquatic vegetation is necessary. YOY golden shiner began to appear in substantial numbers at beach station T (influenced by Pigeon River) in July. As with other minnows (e.g. bluntnose minnow) it appeared that this station was the most suited of the three Pigeon Lake beach stations for spawning and rearing of young. Some spawning at other Pigeon Lake beach stations was indicated by the presence of low numbers of YOY in July (Fig. 54). Catches of YOY declined in August and again in September. These declines were probably due to natural processes of mortality, predation and dispersal. At this time there was also an increase in the size of YOY which may have coincided with an increased ability to avoid our nets. Macrophyte cover in the area had also appreciably declined, a factor which would assist fish in avoiding a net. 1^9 CD C 43 HSU 'ON -a - HSU 'ON tO +J <3J • C C 03 i— CD r— sr— °r- jC CD U Of» E S O 4-J •i— CO r— 03 a. o; 3 -o •» 4-3 c c •i- 03 r*8 =M Q. «C CDr— 3 r— 03 O) U -O CL i- E >Q- = ex O w h 3 C C z a i cu -f- " c 2 3 -J i -j crr^ «m <; y ^ c si 3 CO re • jz c JZ * 3 C 03 03 U r— Q. S- o c: (i ii n 153 TOTAL LENGTH (mm) NO/BEER FIG. 54. (Continued) inshore during the spawning season. No diurnal activity patterns could be determined from our data and little correlation between length of fish and water temperature at which they were caught was observed. Bluntnose Minnow — Introduction — The bluntnose minnow is native to much of central North America, including the Mississippi and Great Lakes drainages (Scott and Grossman 1973)* Although bluntnose minnows are uncommon in the openwater of Lake Michigan, the slow moving, soft-bottom nature of Pigeon Lake provides an excellent habitat for propagation and survival of this species. Spawning of the bluntnose minnow occurs in 0.3-1 ss of water during May or June. Adhesive eggs are laid on the undersurfaces of stones and other objects. Hatching takes place in 1-2 wks (depending on water temperature), and larvae may attain a length of 12 mm within 2 wks (Westman 1938). Preliminary observations of piscivorous fish stomachs in Pigeon Lake indicated the bluntnose minnow served as forage for a number of species including northern pike, largemouth bass, yellow perch, grass pickerel, bowfin and sunfishes* Bluntnose minnows are reported to feed primarily on organic detritus and bottom ooze (Heufelder 1976)* Seasonal distribution — All bluntnose minnows in the present study (1560 fish-7.556 of total catch) were caught by seine at Pigeon Lake beach stations. The apparent absence of bluntnose minnow from deep water stations in Pigeon Lake was probably due to inefficiency of our gill nets to sample this minnow. Bluntnose minnows occurred in collections at all Pigeon Lake beach stations in June (Fig. 56)* At this time, most specimens caught were greater than 46 mm in length; most were caught at night. Higher catches at night during June were probably 15* o ro in CM O OsJ m lT) cd l?S cd 42 •H 4J x: ^c a 60 •H 3 s CO a CD CO cd o 5-i |-3 m 0) c •H n rG a co CO C cd ,n u a 0) S 4-» 03 d a O _ •H o £ £> :s co — E U c CiO • o £j >n «h _j tH • a a cd cc a 0) UJ IM TJ K o C 2 H ^ U 5-4 ■u cd 0 •H X> X M-4 C fi H •h cd CD CO J u Z a •H CO UJ J-4 — < > -J ^j D Cd -= +1 U .J o 0) H a. '3 C m s •H 0) a; CO u o cd 3: «+■» H CO jL| • CJ 0) m a > m 4J • ^ r^ cu cd p^ CD C\ CO H (0) 3aniva3dW3i 155 O day ■I night 250 i 200 150 1 311 Station V k^"^ C5 J UN JUL AUG SEP OCT NOV 250 O 200 -I 5j 15° * H 100 50 0 Station T 250 1 200 - 150 - 100 50 " 0 J UN Station S JUL AUG SEP OCT NOV I L J UN JUL AUG SEP MONTH OCT NOV FIG. 56. Total number of bluntnose minnow caught in duplicate seine hauls in Pigeon Lake near the J. H. Campbell Plant9 eastern Lake Michigan, June - November 1977. 156 TABLE 30. Monthly gonad conditions of bluntnose minnows caught in Pigeon Lake near the J. H. Campbell Plant, eastern Lake Michigan, during 1977 . All fish examined in a month were included except poorly received specimens. Gonad condition Jun Jul Aug Sep Oct Nov Dec Males Slight development Mod . development Well developed Ripe-running Spent 3 4 10 Females Slight development Mod. development Well developed Ripe-running Spent Absorbing 1 2 4 2 2 Immature 13 54 101 24 Unable to distinguish 14 10 related to the nocturnal spawning activity of this species documented by Westman (1938). Presence of bluntnose minnow larvae in our field larvae samples taken in June (Appendix 8) indicated that spawning in Pigeon Lake began in late April. Gonad data (Table 30) suggested that spawning continued through July. Highest numbers of adult bluntnose minnows in June were caught at beach stations V (undisturbed Pigeon Lake) and S (influenced by Lake Michigan), with somewhat lower numbers caught at station T (influenced by Pigeon River) (Fig. 56). July seine hauls were in sharp contrast to June seine hauls as the majority of bluntnose minnows were seined in the daytime. Relatively lower nocturnal catches of bluntnose minnows from beach stations in July may indicate, a nocturnal movement to deeper water. Increased numbers of bluntnose minnows were observed at stations V and T, while lower numbers were observed at station S. Length-frequency data (Fig. 57) indicated that a substantial part of the increased number of bluntnose minnows collected at station V and T in July was due to recruitment of 26-35 mm fish to the population of bluntnose minnow vulnerable to seines. These fish were probably Y0Y. Reasons for the dearth of Y0Y bluntnose minnows at station S (influenced by Lake Michigan) in July are unclear * Station S may not 157 rf cd H I- 3 A 1 2 ° § § HSU "ON ■8 1 2 ° I § HSIi "ON «s HSII *ON d ■« ^ 1 § ° 8 3 ° 8 s HSII 'ON 3 03 JC 01 Jx£ CD 03 C -J •r° 0) c (/) s- c -M S- c: 03 3 CD !»» C J3 £ >>r^. II u en sz f=H ■ > <*- cu 03 1 > "a j£T o 4^ sz 18 OJ £ o a UJ UJ o O m o (0) 3Un±Vtf3dW3± m cd O CO 0 c u-» CL o C gs *H C3 w en o 03 cd • > 3: cd C •H 4J JO s > a a; .u '3 T3 d cd a co >-«. CM o a £ r-i o-| CD £' CO M a> C 0J' M 4-4 x: 0* -u CD CO H 0) C !m •r- CO 3 CD 4-J CD P cd ^ .-^ u cc rH CD H-t a. «H (3 £ cd a; o a 4-> 0) •rt 00 4-J r* •H M cd £* a 0) > f 0 T3 u 6 0) 44 r^ 4-J r^ x: CO a*. &o CD r— } •H a a > * 2: 4J cd i^ c>0 cd •rl • cu x: CO 60 CJ uo •H r—t X r-l • cd ■CD CD JvJ i— «» >% cd u. Xi 1— 4 161 Campbell Plant. They were caught mostly from Lake Michigan and accounted for approximately 1.14? of the total catch from this lake (Table 13). Only a few trout-perch were collected from Pigeon Lake. The major portion of the Lake Michigan catch was obtained by trawl; gill nets and seines contributed only a small portion of the trout-perch catch. Seasonal Distribution — Trout-perch live in deep water during the colder months and migrate to inshore areas in spring and summer. Wells (1968) found most trout-perch in Lake Michigan between 23 and 32 m in February. In Lake Superior, they remained in water deeper than 64 m during winter and early spring (Bostock 1967). The inshore movements in southeastern Lake Michigan began in April, increased through May and reached a peak in June (Jude et al. 1975)- During summer months, trout-perch were found mostly at the 9 and* 12 m contours in Lake Michigan (Wells 1968) and in water less than 27 m deep in Lake Superior (Bostock 1967)* June — As our sampling program did not start until June, data from previous months were lacking. Peak catch of trout-perch occurred in June (Appendix 4 and Fig. 59)- Trawling was the most productive fishing method and captured trout-perch at all stations sampled (Appendix 5 and Fig. 60). Most trout-perch were caught between 6 and 15 m. Only a few specimens were collected at 18 and 21 m (Fig. 60), suggesting that the bulk of the trout-perch population remained within the 15 m contour in June. Trawling was not performed at 3 m, but the catch of four trout-perch by seine (Fig. 61) indicated that the distribution of this fish extended to the beach zone. Because of bad weather no bottom gillnetting was completed at night. The day set did not capture any trout-perch c Compared to the pattern of seasonal migration of trout-perch described in other studies (Bostock 1967, Jude et al. 1975), our data suggested that June was the peak period of trout-perch inshore movements which probably started in April or May* More trout-perch in June were caught at night than during the day at all stations except for station P (15 m - s.). Trout-perch have been observed to move inshore at night to spawn in the shallows of lakes or lower reaches of streams (Magnuson and Smith 1963? Scott and Grossman 1973)o Presence of ripe adults and of larval trout-perch (see FISH LARVAE AND ENTRAINMENT) in the inshore water of Lake Michigan near the Campbell Plant suggested that spawning occurred during at least June in the area. Trout-perch spawned from May to August in Lower Red Lake, Minnesota (Magnuson and Smith 1 963) and from June to August in Lake Erie (Kinney 1950) and in southeastern Lake Michigan (Jude et al. 1975) . In 1972, however, spawning of this species in Lake Michigan was slightly delayed; it started in late June and extended through August (House and Wells lo2 Station D day ■ night ND = no data L (6m-N) H(21m-S) » AUGUST SETTB4BER OCTOBER NOVEMBER DECEMBER G(l8m-S) 5o 0 F(l5m-S) o 100 50 0 E(l2m-S) H 50 100 n D (9m-S) 50 1 0 JUKE C (6m-S) 100 - 50 > 0 B (3m-S) 50-. SEPTEMBER OCTOBER JUKE AUCUST SEPTEMBER OCTOBER ROVEWBER DECEMBER B ■ AUGUST SEPTEMBER OCTOBER HOVEMBER DECEMBER DECEM3ER JULY MONTH FIG. 59, Total number of trout-perch caught in "bottom trawls fished during day and night once per month June through December 1977 in eastern Lake Michigan in the vicinity of the J, H. Campbell Power Plant. 163 " ■ t 1 ■ ' ■ ! 1 i * i 1 1 1 * 1 i 4 " 1 j j «- i 1 . "1 j. "Z H-, — . — i — . — " T ' 1 '" ' i 1 1 I i 1 LS 3 S S S s » HSU 'ON * k S 1 •s 8 ° 3 8 HSU 'ON i I S 2 LL, ^ UJ cm O £ (U c 3 •°D CD c e 3 er» S- 3S 3 Is2 T3 S >~ W —J CO J "> 3 • < (t3 C s J£ 2E 0? 0) 4-> «S*£ CL &- 3 CO C CD C 3 C • CO "O 1? JZ ea E z -u ^ s- Z >>•'- o — s? ui: lf„ o _j c o S» XJ < E 3 S • a= e ^ or 4J s- (V OJ JZ a* o s» ^ C7> C <+- q- SZ IS E - 0)*t- «^5 en £ ■ CO c a> r^ •r «j rv. +J ,— . o JC CL t— i cn E 0 >> «T- *c o *- (Q C CO S a) °o «£J o o E II 2^ Z . 2 C on the day we sampled. Although July was normally the period of fairly high spawning activity of trout-perch (Jude et al . 1975; Magnuson and Smith 1963), our gonad data (Table 31) indicated that very few trout-perch 168 TABLE 31 . Monthly gonad conditions of trout-perch caught in Lake Michigan near the J. H. Campbell Plant, eastern Lake Michigan, during 1977. All fish examined in a month were included except poorly received specimens • Gonad condition Jun Jul Aug Sep Oct Nov Dec Males Slight development 18 25 10 23 4 1 Mod . development 36 11 17 10 11 8 Well developed 19 3 13 6 9 Ripe- running Spent 2 4 Slight development 15 4 16 30 6 Mod. development 32 5 16 5 13 1 Well developed 11 4 8 21 Ripe- running 3 4 Spent 3 2 8 3 Absorbing Females Immature 113 102 10 Unable to distinguish 15 10 spawned in July probably because of the low water temperature. August — In August, the majority of large and small trout-perch were caught at night between 6 and 12 m (Fig. 60). Several specimens over 90 mm in length were caught in night bottom gill nets at 9, 6 and m (Fig. 63) and two adults were collected by night seine (Fig. 61), indicating that large trout-perch once again were distributed in the beach zone. During the day most trout-perch probably returned to 12 m or deeper water. Several specimens were trawled during the day at 12 m and a few at the deeper stations. 3 Although the total August trout-perch catch was lower than that of July, larger individuals, approximately 90-137 mm, were slightly more abundant than in July (Appendix 4, Fig. 60). Spawning activity also appeared to increase slightly, as more adults with ripe and spent gonads were found in August than during the previous month (Table 3D- The low August catch was due exclusively to the decreased capture of trout-perch 90 mm or less. These smaller individuals must have left the study area. September — Migration of trout-perch to deeper water starts in September in southeastern Lake Michigan (Jude et al. 1975) and in late September or early October in Lake Superior (Bostock 1967). A 169 Station L (6m-N] E(l2ta-S) D (9m-S) C (6m-S) B (3m-S) A(l.5m-S) o .H O H 8, 6 4. 8_ 6. *. 2- 2 0 8 ■ 6 " Is - □ day ■ night ND = no data SEPTEMBER OCTOBER SEPTEMBER OCTOBER ■ I AUGUST SEPTEMBER OCTOBER SOVEMBER SEPTEMBER OCTOBER SEPTEMBER OCTOBER SEPTEMBER OCTOBER MONTH FIG. 62. -Total number of trout-perch caught in bottom gill nets fished during day and night once per month June through December 1977 in eastern Lake Michigan in the vicinity of the J, H« Campbell Pover Plant « 170 i HSU 'ON CQ 3 HSU *0N >) rmmm 3 -D C7> C •r— S- 3 -a C CO i +■> o -4 ^ CT < •p— § s a h o •r*" ^-> 21 •p o 03 C CJ S- •r-° 0) r— 4-> CL CO 3 03 -o 4-> 03 -C r- cna. =5 03 r— • O CD -C jQ U a. s- E > *r— § >- OS - = s CD < 3 ^ • 5 cr ro 4-> 5 0) -J -C S*. en <♦- C •r- i •r— £ JZ -m r^ !l cr>r^ SZ CD «— < ■ -J 0) oo -Q >> ^o E 03 a> -a > o 11 o a 171 < H O HSU 'ON Q a PQ S •s a; c c o CO HSIi °0N C3 S 172 relatively large number of trout-perch were trawled in the 6-15 m zone in September in our study area (Fig- 60) indicating that they still remained inshore. No trout-perch were caught inside the 6 m contour. A few specimens were taken by gill net at 6 and 12 m (Fig. 63), but none were seined. The number of yearling trout-perch of approximately 90 mm or less had increased slightly in our catch compared to August collections (Fig. 60). YOY measuring 20-40 mm first entered the trawl catch in September (Fig. 60). In the vicinity of the D. C. Cook Plant, southeastern Lake Michigan, YOY trout-perch of comparable size also were caught in September (Jude et al. 1975). During the previous months these YOY were probably too small to be caught in the sampling gear. YOY apparently exhibited the same nocturnal behavior as the larger fish as they were caught only at night. Of course net avoidance is also a factor. October — Trout-perch catch declined sharply in October at every depth sampled, indicating that most fish had already left for deeper water. Several individuals over 90 mm were still caught by trawl between 6-12 m, but yearlings had almost completely disappeared from inshore water (Fig. 60). Due to bad weather no gill nets were set this month and no trout-perch were caught by seine. YOY, ranging from 25 to 35 mm apparently also started their offshore migration at this time, since they were found in deeper water than- in September (Fig. 60). November and December — No trout-perch were caught by seine in November. Several large individuals, however, occurred in the night trawl catches from 6-12 m (Fig. 60) and in night gill net catches from 1-5-9 m (Fig. 63). The relatively warm water (10.9-12.9 C) in November may have delayed their retreat to deeper water. No yearlings were found inshore in November. A few YOY, 25-30 nim, were also included in the November trawl catch (Fig. 60). By December, practically all trout-perch had left the inshore region. Only a few large individuals were caught by trawl at 6 m (Fig. 60). No trout-perch were caught in surface gill nets during the study period corroborating that they are benthic species. Temperature-Catch Relationships — Catch temperatures for trout-perch ranged from 1 to 21.5 C. The majority of specimens were collected between 6 and 12 C. In southeastern Lake Michigan trout-perch tended to occur in slightly higher temperature ranges. They were mostly found at 10-15 C off Saugatuck, Michigan (Wells 1968) and between 14-20 C near the D. C. Cook Plant, southeastern Lake Michigan (Jude et al. 1975). Trout-perch probably remained active at lower temperatures. Most specimens collected in water as cold as 1 C had food in their stomachs . 173 Although there appeared to be no statistically significant correlation between sizes of trout-perch and the water temperatures at which they were caught, fish larger than 90 mm tended to be found in slightly warmer water than smaller fish (Fig, 64). This difference in temperature preference between sizes of trout-perch may be an important * factor influencing the distribution of various sizes of trout-perch in our study area. Trout-perch 90 mm or less were commonly found on 27 July when water temperatures ranged mostly from 5.3 to 7.2 C (Fig, 60) . The catch decline observed on 15 August (Fig. 60) coincided with higher temperatures which ranged mostly from 15 to 21.5 C* The slight catch increase of trout-perch on 21 September corresponded to a drop in temperature to 5.1-7-3 C. Decline of the catch of trout-perch over 90 mm on 27 July (Fig. 60) and its increase on 15 August also coincided with the low and high water temperatures mentioned above. Decrease in the number of large trout-perch caught in July may in part result from the movement of ripe adults to a more favorable water temperature. Trout-perch generally spawn in relatively warm water. Spawning took place at water temperatures of 16-20 C in Lake Winnebago (Carlander 1969) and 19-21.4 C in western Lake Erie (Kinney 1950). Magnuson and Smith ( 1963) reported that the peak spawning run in Lower Red Lake occurred after the mean air temperature had remained over 10 C for 44 days. In Heming Lake, Manitoba trout-perch spawned at a slightly lower temperature range (6-11 C) (Lawler 1954). Only four trout-perch were caught in Pigeon Lake, all by bottom gill net at station M (influenced by Lake Michigan); two were caught in November and two in December (Appendix 4). This species, however, may enter Pigeon Lake more frequently than our catch suggested. During the period January 1974-March 1975, 174 specimens were found in impingement samples from the Campbell Plant (Consumers Power Company 1975) . Water temperatures may have influenced movements of trout-perch into Pigeon Lake during colder months. In December, water temperature was 1 C in the inshore area of Lake Michigan and 2.4 C at station M (influenced by Lake Michigan). Most trout-perch, however, seemed to enter Pigeon Lake during the fall. Of the 174 fish found in the 1975 impingement samples, 61 were collected in October and 63 in November. Although trout-perch were known to spawn in tributary water (Lawler 1954; Scott and Grossman 1973), 1977 data showed no evidence that spawning took place in Pigeon Lake. Other Considerations — Mortality of trout-perch following spawning reported by Kinney (1950) and Magnuson and Smith (1963) has not been observed in southeastern Lake Michigan (Jude et al. 1975) or in our study area. Growth rates of trout-perch reported in the literature varied considerably in different bodies of water. At the end of their first Ijh o fO r- m CVJ 4- O (0) \a o 3H01VH3dW31 m r-1 03 • CD r^ GO r^ o> rH rH rH 03 *» C >^ crj ^ GO «H H 42 42 a 00 -H -< ^ -' ^ 03 O 00 • O cr a x o UJ D rH K rH • 2 6 0) |3 X 42 o O H .,-( H rH 4J o 4-i -J peratures f he vicinity e *-» O a cn m 16. 64. Weighted-mean t ^pes from Lake Michigan in ^rticril lines represent 4* LL. u > 175 year of life, trout-perch grew to 65-92.5 mm In total length for both sexes in Lake Erie (Kinney 1950), 30*1 and 38.1 mm for male and female respectively in Lake Superior (Bostock 1967) and 51*4 and 50*8 mm for male and female respectively in Lower Red Lake (Magnuson and Smith 1963). Trout-perch in. Lake Michigan seemed to have slower growth than those of Lake Erie and Lower Red Lake, but considerably faster growth than Lake Superior trout-perch . The calculated length of trout-perch at the end of the first year of life in southeastern Lake Michigan was 49 mm (House and Wells 1975)* The age I trout-perch collected in June in the study area ranged in size from 25 to approximately 74 mm and had a modal length of 50 mm (Appendix 4). Near the D. C. Cook Plant, southeastern Lake Michigan, age I trout-perch appeared to grow slightly slower than our yearlings, reaching a modal length of only 45 mm in May and June and 50 mm in July (Jude et al. 1975)* Length-frequency data (Appendix 4) suggested that age I trout-perch reached estimated modal lengths of 60, 70 and 80 mm respectively for July, August and September- Although these data (Appendix 4) showed no length increase by trout-perch in October, growth may continue at a slower rate* House and Wells (1973) reported that at Saugatuck, Michigan, all trout-perch appeared to have completed more than 80%, but less than 100$, of the total growth of the year by October . Although trout-perch were considered an important food of predatory fishes in several lakes, they apparently played a minor role as forage species in Lake Michigan . They seldom occurred in the stomachs of piscivorous fishes like yellow perch, northern pike, lake, brown and rainbow trout , Chinook and coho salmon (Jude et al. 1975). Ale wives which were abundant in our study area appeared to be preferred food for larger predatory fishes . Stomachs of lake trout caught in the study area contained mostly alewives and no trout-perch. Abundance of trout-perch in southeastern Lake Michigan was believed to result from lack of predation (Jude et al. 1975). Trout-perch appeared to be homogenously distributed in the study area. There was no difference between catches at station C (6 m - reference) and station L (6 m - s. discharge) during the study period (see STATISTICS). Summary — Trout-perch were caught mostly in Lake Michigan. Only a few specimens were collected in Pigeon Lake. They remain in deep water in winter and migrate inshore in spring and summer. In the study area, spawning probably occurred in the shallow water of Lake Michigan from June through August. Although trout-perch were known to spawn in tributary waters our data showed no evidence that spawning took place in Pigeon Lake. A small number of YOY measuring 20-40 mm first appeared in the September trawl catches in water ranging from 9 to 15 m. Prior to this 176 month YOY were probably too small to be retained in our fishing gear. A few YOY were again caught in October and November. YOY probably retreated to deeper water in winter. Yearling trout-perch generally occurred between 6 and 15 m. More were caught in June and July than in August and September. They probably moved offshore in October as no yearlings were caught in this month or the rest of the year. Adult trout-perch were caught between 6 and 15 m. Highest catches of adult trout-perch were made in June. A modest adult population appeared to remain in the study area during the summer. Offshore migration generally started in the fall. Several large trout-perch, however, still occurred in October and November catches. The majority of trout-perch were caught between 6 and 12 C. In the summer yearlings tended to be found in slightly cooler water than adults. More trout-perch of all sizes were caught at night than during the day. Largemouth Bass — Introduction — In North America the native range of the largemouth bass extends from southern Ontario and Quebec throughout the Great Lakes and the Mississippi Valley south to Florida and northeastern Mexico (Mraz et al. 1971). Highly regarded as a sport fish, the largemouth bass is often stocked in farm ponds. Such introductions have extended the range of this species westward. Largemouth bass are widely distributed within the Great Lakes basin inhabiting shallow, weedy lakes and river backwashes (Mraz et al. 1971) usually at depths less than 6 m (Becker 1976). Largemouth bass fry selectively feed on limnetic copepods and cladocerans (Elliott 1976) • Immature and mature largemouth bass consume aquatic insects, fish (Bennett and Gibbons 1972), crayfish and frogs (Mraz et al. 1971), seasonally dependent upon the size and availability of food. In the field, largemouth bass preferred water temperatures between 26.6 and 27.7 C (Scott and Crossmann 1973). However, Becker (1976) states that the species is most active between 15.6 and 24.4 C. Spawning occurs from late spring to mid-summer, with a peak noted in early to mid-June (Scott and Crossman 1973). Nesting sites, usually in sand and gravel, are prepared by the male when water temperatures reach 15.6 C and egg laying follows after temperatures reach 16.7 to 18.3 C (Mraz et al. 1971). During the 3 to 7 days it takes for eggs to hatch, the male guards the nest aggressively. Sexual maturity is achieved in 3 to 5 yrs (Scott and Crossman 1973) at which time the fish reach lengths of approximately 300 mm. 177 Seasonal Distribution — All largemouth bass caught in the Campbell Plant area were from Pigeon Lake; they were collected from all stations except openwater station M (influenced by Lake Michigan)* Station M differs from the others primarily because it is deeper and offers less macrophyte cover than other sampling areas. Consequently, absence of largemouths at this station could be due to its physical characteristics. Nearly twice as many largemouth bass were captured during the day (495) as during the night (265) (Appendix 4). Of the total catch, 99% were caught in seines and nearly all were YOY (Appendix 5). The largest monthly seine catch (273) occurred in June (Fig. 65). All fish were YOY, except four which included three yearlings (90-110 mm) caught at station V (undisturbed Pigeon Lake) and one adult (370 mm) caught at station T (influenced by Pigeon River). Mean length of YOY during June was 23 mm (range 17-31 mm). Nearly all YOY were caught at station T with considerably more caught during the day (209) than at night (58) (Fig. 66). The three yearlings and one YOY were caught at station V and two YOY were caught at station S. Observed abundance patterns of bass larvae and subsequent YOY were similar. Highest concentrations of larvae caught in plankton nets and YOY caught in seines both occurred at station T. Apparently the dispersion rates of early life stages of largemouth bass were low during summer months. The one adult captured at station T was a spent female indicating that some spawning occurred prior to 3 June (Table 32). Most largemouths caught in July were YOY (Appendix 5). Only three larger bass (range 115-167 mm) were taken and these were caught at beach stations S (influenced by Lake Michigan) and V (undisturbed Pigeon Lake). More YOY were caught at stations V and S in July than in June. In addition far more YOY bass were caught at station T in July than were caught at the other two beach stations. Numbers of bass caught at station T decreased in July when compared with June. Rapid growth of YOY bass occurred between June and July as mean length increased from 23 mm to 57 mm, over a doubling in length. Length range of bass in July was 29-85 mm. Day catches were approximately equal to night catches. Growth of YOY continued in August, but length did not increase as rapidly. Total catch continued to decrease (Appendix 4) when compared to previous months. Larger numbers of bass were caught at beach stations V and S than in previous months, but YOY remained concentrated at station T (Fig. 66). Two older fish (148 and 170 mm) were caught at station V. Length range of YOY caught in August was 38-109 mm (mean length = 67 mm). One YOY and two adults were caught in a day gill net at openwater station Y (Fig. 67)- In September, YOY ranged from 58-113 mm with a mean length of 78 mm (Appendix 4). Most YOY were caught at station T and some at station V 178 □day night 100 n 75- 50 - Station V JUN 100 J£l JUL Station T JUN JUL AUG SEP OCT AUG NOV SEP OCT NOV 100 ■ 73 Station S 50 25 - JUN JUL AUG SEP OCT NOV MONTH FIG. 65. Total number of largemouth bass caught in duplicate seine hauls in Pigeon Lake near the J. H. Campbell Plant, eastern Lake Michigan, June - November 1977. 179 \* His H» § 3 -i S = ■I 5 3 § 8 § 3 O) c ■8 s duri .8 e haul chigan ■8 £ 5 1 sein e Mi - £ 1 •„. , , , , 4-> C I § si § a § § -C rd Or— HSU -ON s cau ell P => H~ CO CO «jQ -Q E 3 • O 2- £ fT3 0) *■=-=> jC O S- M- (O 0 CO c •r- O z «C >i- U CL, c ^ C s oo ' s- r^ cr> <+- O • 3S >> I § ° g § ° 8 § ^ A3 -iHli 'ON Ii > H— GO Ul„ ^ 180 220 300 *C3 SOQ i'OTAL LENGTH (ram) OCTOBER TOTAL I.ENT.TH IWEMBER FIG. 66. (Continued) TABLE 32. Monthly gonad conditions of largemouth bass caught in Pigeon Lake near the J. H. Campbell Plant, eastern Lake Michigan, during 1977. All fish examined in a month were included except poorly received specimens . Gonad condition Jun Jul Aug Sep Oct Nov Dec Males Slight development Mod c Development Well developed Ripe-running Spent 1 10 14 1 4 11 1 2 Females Immature Slight development Mod . d evelopment Well developed Ripe-running Spent Absorbing 2 1 36 93 78 40 10 20 Unable to distinguish 10 (Fig. 66) 67). Three adults were caught in a gill net at station Y (Fig, Catches of bass in October were the lowest of the study period (Appendix 4), but increased again in November. Mean lengths of largemouth bass YOY in October and November were 73 and 77 mm, respectively. Catch of bass at station S remained low. Catches at beach stations V and T were similar for these 2 months (Fig. 66). 181 ^ 0 -; 2 - TOTAL LENGTH (on AUGUST TOTAL LENGTH (tan) SEPTEMBER FIG. 67. Length-frequency histograms for largemouth bass caught in duplicate bottom gill nets during August and September 1977 in Pigeon Lake near the J. H. Campbell Plant, eastern Lake Michigan, □ s day ■ = night. Length ranges for YOY bass in October and November were 49-126 mm and 57-128 mm, respectively. Temperature-Catch Relationships — Temperatures at time of capture are probably not good indicators of thermal preference due to confounding by the seasonal temperature cycle and unavailability of a large range of temperatures. Largemouth bass YOY remained close to shore and probably would not behaviorally thermoregulate like some Lake Michigan species, due to the limited range of available temperatures. Fish 30-50 mm were caught at low water temperatures in June, while weighted-mean temperatures for other YOY bass intervals reflected summer temperatures ( Fig . 68 ) . Other Considerations — Stomach analyses of YOY largemouth showed that most were eating amphipods which were extremely abundant in the weedy areas of Pigeon Lake. Other prey items included dragonfly nymphs, damselfly adults and corixids (water boatmen). Excellent food supply is clearly responsible for the abundance and good growth of bass in the lake . Summary — . Largemouth bass in Pigeon Lake probably spawned before 3 June and beach station T served as an important nursery area. Few adults were among the 760 caught. Most were taken during June in seines. Declining YOY catches throughout the year at station T probably were indicative of a decreasing population, as high mortality due to predation, disease and other causes would be expected to occur during this life history stage. No largemouth bass were caught at station M (influenced by Lake Michigan) where there was less macrophyte cover. Growth of YOY bass was very rapid through the summer and may slow in October. Amphipods, which were extremely abundant in weedy areas, were the predominant food of YOY largemouth and along with other abundant food clearly responsible for the abundance and good growth of bass in the lake. Adult largemouth apparently avoided seines and gill nets since few adults were caught at any time of the year, yet many were seen during the mark and recapture study. 182 o .= o o I o i o o I o i o < > cc -1 c3 >> c SO ■U -H -£ ,-C CO 1) 3 -H 03 S a a; CO ^ CO crj oj J C 4J CU 3 4J O CO g S3 CD OJ 60 J* - 03 aj rH C O 04 CO rH rH rH 03 CD > & 0) g 4-J 03 C CJ •H so • o C »-3 -H cu 4-i rH CD 03 g *J > g OJ CD 03 JZ U 4J a S 0) T3 03 OJ CU ^1 U a* J-4 CO g fi I o a oo c 4J -H 'H ^ dt H WD •^ g rH CU C 03 3 m a y_ 50 rH 183 Pumpkinseed — Introduction — The pumpkinseed (Lepomis gibbosus) is restricted to the fresh waters of eastern North America (Scott and Grossman 1973). It prefers weedy areas of lakes, ponds and streams, in cool to moderately warm water (Hubbs and Lagler 1958) . In Lake Michigan, it is found in the shallow water of protected bays (Becker 1976)* Pumpkinseed spawn in late spring and summer- Carbine (1942) reported that pumpkinseed spawned from 31 May to 18 July in Deep Lake, Michigan. This species feeds primarily on insects, small molluscs and crustaceans. In addition, larger pumpkinseed may feed on small fish, including their own young (Trautman 1957). Pumpkinseed are valued as a sport fish (although in some overcrowded situations, stunting may occur). The young serve as forage for other game species. They also make attractive aquarium fish due to their colorful markings (Becker 1976). Seasonal Distribution -« Pumpkinseed were collected from Pigeon Lake (232 individuals) and from Lake Michigan, where one was seined at beach station R (n. discharge) (Appendix 4). Pumpkinseed were the second most abundant centrarchid collected (second only to largemouth bass) and represented 1.1 J of the total catch of all species taken from Pigeon Lake (Table 14). Of those collected from Pigeon Lake, 228 were taken with beach seines and four were collected in bottom gill nets (Table 19) set at openwater station Y (influenced by Pigeon River) . Sizes of pumpkinseed caught ranged from 25 to 199 mm, with most (118) found in the 40-60 mm range. According to age-length data from a Michigan pond given by Scott and Crossman (1973) fish we caught would range in age from YOY to age 8. In June most pumpkinseed were caught at beach station T (influenced by Pigeon River) (Fig. 69). They ranged in size from 40 to 130 mm and were probably all adults. The first occurrence of YOY pumpkinseed was in July at beach station T. YOY were not caught at other Pigeon Lake beach stations (S and V) at this time. These areas might not be as suitable for the rearing of young as was station T. The large size of YOY (30-50 mm) caught in July (Appendix 5) suggested that spawning had begun in May prior to the beginning of sampling. Gonad data (Table 33) indicated that spawning was occurring in June. High numbers of YOY pumpkinseed were again found at station T in August. In addition, some- adult pumpkinseed appeared in catches at station V (undisturbed Pigeon Lake). The reason for this movement of adults from station T to station V is unknown but it is possible that 18U- I ■ c I. I C •s CV CO •a HSIi 'ON O* CO CJ HSU 'OK .§b ^ I 1 <• . •a 2f <© CJ w •r- cd o jz •4_> CO CD 0r~ j* =£1 03 >> a jz jz o CD CD 3 en o cr •f— 4-> CD Q. JZ S~ a> q- JZ •i— i Of-K JZ JZ +* rv. 18 cn«^ JZ CT> CD r-« ■ «-J CD e JQ >^ en E 03 CO cd -a o I! 2 oD 185 Jrll Jk_ I -til. TOTAL LENGTH (mm) OCTOBER FIG. 69. (Continued) TOTAL LENGTH (ra NOVEMBER TABLE 33. Monthly gonad conditions of pumpkinseeds caught in Pigeon Lake near the J. H. Campbell Plant, eastern Lake Michigan, during 1977. All fish examined in a month were included except poorly received specimens. Gonad condition Jun Jul Aug Sep Oct Nov Dec Males Slight development 1 6 13 Mod. development 4 8 2 Well developed 2 1 Ripe-running Spent 1 5 Females Slight development 1 Mod development 5 Well developed 2 Ripe-running 3 Spent Absorbing 1 3 9 3 2 1 1 1 2 Immature 10 27 15 Unable to distinguish 30 27 aquatic vegetation at station T became too thick and discouraged movement of adult fish in the area. During September there was an apparent movement of adult fish from areas seined. Gill nets set at openwater station I (influenced by Pigeon River) (Fig. 70) indicated the presence of some adults in deeper water; none were caught there during August. YQY remained in shallow water (Fig. 71 ) . .36 ■^ Of- ~ 2 - JU rOTA„ LENGTH SEPTEMBER TOTAL LENGTH NOVB1BER FIG. 70. Length-frequency histograms for pumpkinseed caught in duplicate bottom gill nets during September and November 1977 in Pigeon Lake near the J. H. Campbell Plant, eastern Lake Michigan. □ - day ■ = night. October seine catches showed a similar trend as was found in September. YOY were still found in shallow areas. November sampling again indicated that some adults were in deeper water, while YOY still inhabited the beach area. Adult pumpkinseed probably overwinter in the relatively deep water near station Y, while YOY probably overwinter in an area closer to shore than adults. Temperature-Catch Relationships — A summary of water temperatures at time of capture for different size pumpkinseed did not indicate any clear relationship between temperature and size of fish (Fig. 72). However, Pigeon Lake, in the vicinity of the Pigeon River, is shallow and probably seldom stratifies, causing a very narrow range of water temperatures to be available to fish. Other considerations — Pumpkinseeds preferred the weedy, shallower habitat of the eastern end of Pigeon Lake as opposed to the more open, deeper western end of the lake. No pumpkinseed were collected at 6 m station M (influenced by Lake Michigan). Only one pumpkinseed larva was collected in Pigeon Lake during the entire sampling period (see FISH LARVAE AND ENTRAINMENT) . However, small centrarchid larvae are extremely difficult to identify and many of the Lepomis spp. larvae found in Pigeon Lake samples could be pumpkinseed . Summary — Pumpkinseed were collected almost exclusively from Pigeon Lake and appeared in catches during every month sampled. They seemed to prefer the weedy, shallow eastern end of the lake near the Pigeon River. As winter approached, adults appeared to move to deeper water, while YOY stayed inshore. 187 □ day ■ night 50 40 H 30 20 10 0 Station V JUN JUL AUG SEP OCT NOV 50 -i Station T IhhlLjB JUN JUL AUG SEP OCT NOV 50 i Station S 40 - 30 - 20 - 10 - JUN JUL AUG SEP MONTH OCT NOV FIG. 71. Total number of pumpkinseed caught in duplicate seine hauls in Pigeon Lake near the J. H. Campbell Plant, eastern Lake Michigan, June - November 1977. 188 © o cm o 10 o CVJ (0) m o 3an±vu3dW3± rH CJ 03 cd GO >> «H & X\ O U «H ^ 2! &o 3 ai cd ^; a cci H-l CO T3 ff 0) *-, a> a; CO 4J C -a o •H Ct m ^ 0) » g « 3 4J a c cd 4-4 ^ u a* E oj g •«— • *j cn a cj -J •H < • • > x: EC cn q: u a ^ iii 50 • o o £ C *n -h O 2 0) 4-1 rH CD Cd ,n -h X g oj <4-4 "d O O O 2 H "3 UJ >, M -J M 4J Cd O -HTJ «+^ a c •h cd cn a 4J a -h cn u > .3 Lake trout are native to North America and have been widely introduced (Scott and Crossman 1973)- This species is mostly found in large, cold lakes. In the Great Lakes, most live in water less than 110 m although they have been caught at 230 m (Van Oosten 1944). Inshore spawning migrations occur during fall with spawning occurring over rocky reefs. During winter, lake trout are distributed throughout the lake. As water warms, lake trout tend to move offshore; however, lake trout are occasionally caught inshore during summer upwellings in southeastern Lake Michigan (Jude et al. 1979) . Prior to the 1950fs lake trout populations in Lake Michigan were sustained by natural reproduction. The precipitous decline in the lake 19T trout population during the 1950fs has been attributed to predation by the sea lamprey and to overexploitation by the commercial fishing industry (Smith 1968, Eschmeyer 1956) . Current stocks in Lake Michigan are maintained by extensive stocking programs and reasons for the general failure of stocked fish to reproduce are under investigation (Rybicki and Keller 1976). Recent annual catches by sportsmen amounted to more than 4,5 x 10 kg (Wells and Mclain 1973) . Commercial fishing for lake trout is currently banned in Lake Michigan. Lake trout (201) were caught in Lake Michigan during all months of the study period (Table 13). Most were caught during July, September and November. One lake trout (640 mm) was caught in Pigeon Lake during June in a bottom gill net (Appendix 4). Five small lake trout (120-330 mm) were caught in trawls in Lake Michigan. No larger fish were caught by trawling which was possibly due to net avoidance. Three lake trout (640-750 mm) were caught with seines in September and October. Surface gill nets caught 29 lake trout (420-810 mm) during July and September. During upwellings lake trout were apparently more evenly distributed in the water column than during the mid-fall to winter months, since in later months no fish were caught in surface nets. Lake trout were caught in much greater numbers at night (86$) than during the day. This compares closely with findings from research done near the Donald C. Cook Plant where 91$ of the lake trout were caught at night (Jude et al. 1979) and indicates a nocturnal inshore migration particularly during fall when most trout were caught. Significant day catches of lake trout occurred only at stations A (1.5 m - s.) and B (3 m - s.) in September, which may have been due to more favorable water temperatures there (8.2 C) compared with deeper stations (C7-3 C) . The preferred temperature for lake trout has been described as 10 C by Daly et al. (1969) and 12 C by Ferguson (1958). Temperature is a major factor determining lake trout distribution. Our data showed that 95$ of the total catch of lake trout was in water temperatures of 7-13 C; the overall temperature range at capture was 1.5-19-5 C. Data on sea lamprey attacks were collected for lake trout. Of the 187 examined, 27$ had lamprey scars or wounding, which was comparable to findings by McComish and Miller (1975) who determined that 25$ of lake trout sampled in Lake Michigan in Indiana waters had scars or wounds. Jude et al. (1975) reported 22$ of the lake trout captured had sea lamprey scars. In the Campbell vicinity, 4$ of the scars were fresh indicating some lamprey activity in the area. Preliminary 1978 impingement data showed that sea lampreys are present around the Campbell Plant. The smallest lake trout with a lamprey scar or wound was 432 mm, but this fish had a deformed spine. Probability of lamprey attack for this fish would have been increased due to its age and perhaps due to impaired swimming ability. 198 There was a positive correlation between length and occurrence of lamprey attacks when data on the number of lake trout with lamprey scars or wounds were examined by length interval (Table 37). These trends were also apparent for lake trout captured in southeastern Lake Michigan near the Cook Plant (Jude et al. 1979)* No correlation between the presence of multiple attacks and total length of lake trout was apparent. Examination of lake trout stomachs showed that this species fed predominantly on alewives when inshore which agreed with findings of McComish and Miller (1975) who found alewife amounted to 9355 by volume of lake trout stomach contents. Other prey items they found included smelt, gizzard shad, slimy sculpin, spot tail shiner and chironimids. Near the Cook Plant in Lake Michigan alewives were also a primary component of the diet of lake trout (unpublished data, Great Lakes Research Division). Lake trout spawn in the fall so most fish would be expected to show increasing development over summer and early fall and in fact most males and females caught in November were ripe-running (Table 38). Due to the myriad of questions involved with the success of lake trout reproduction, it is not known whether lake trout successfully reproduce in the area. Of the 185 fish examined for fin clips, eight had no clips. Some evidence exists for lake trout homing (Lawrie and Rahrer 1973), but these eight fish were caught during July and September when the fish had probably not "homed11 in on a spawning area. Lake trout maintain themselves in a relatively stenothermal environment by moving to areas best suiting their temperature preferences. Consequently localized warming in the present and future discharge area could alter distribution during colder months. Our present data from stations L (6 m - n.) and C (6 m - s.) in November showed that catches at these two stations were low and essentially equal, Black Crappie — Black crappie are common throughout their range in the Lake Michigan basin (Becker 1976). Their fine flavor makes it quite popular among pan fishermen . This species .is taken commercially in gill and trap nets and is an important sport fish over its whole range « Spawning by crappies usually takes place in May and June, but may be delayed until July during a colder season (Becker 1976). Male black crappie clear shallow nests in water 0.3-0.6 m, then guard and fan eggs that the females lay (Scott and Crossman 1973)- Temperatures favorable for spawning lie between 17.8 and 20 C (Schneberger 1972b). According to Schneberger (1972b), black crappie preferred clear, 199 TABLE 37. Occurrence of sea lamprey scars on lake trout caught near the J, .H. Campbell Plant, eastern Lake Michigan, 1977. Length Total (mm ) no . c No. scarr ed Percent scarred No. scars per fish interval 1 2 3 k+ 800-8U9 6 k 67.0 2 2 150-199 25 11 Uluo 9 1 1 700-7^9 72 21 29.0 17 3 1 650-699 51 12 2U.0 9 3 600-6U9 18 1 6.0 1 550-599 3 0 0 500-5^9 5 0 0 450-U99 1 0 0 k0Q-kk9 2 1 50.0 I Gizzard shad, a member of the herring family, inhabit eastern North America (Scott and Crossman 1973)- In the Lake Michigan drainage basin, 202 they are most abundant in the eastern and southern areas (Becker 1976). This rapidly growing species serves as a forage fish only until the middle of its second year (Bodola 1966) • Gizzard shad are often considered a pest species because of their attraction to inlets and outlets of industrial plants and their occasional spring, fall or winter die-offs (Bodola 1966). Their flesh is soft, tasteless and bony but can be used as fertilizer and livestock feed (Miller 1960) . Spawning occurred in Lake Erie during early June into July, being most intensive in mid- June when water temperatures reached 19.5 C (Bodola 1966). Miller (1960) reported spawning taking place in the U.S. from mid-March through most of the summer although the bulk of the population in warm temperate areas spawned during April, May and June. He also reported that gizzard shad generally spawn with rising water temperature within the range of 10 to 21.1 C. Gizzard shad (age II) spawn in masses at the surface of sloughs, ponds, lakes and large rivers while rolling and tumbling around each other. Eggs sink and adhere to plants or any other object they contact (Miller 1960). Inspection of gonads of gizzard shad captured near the Campbell Plant gave no clear indication when spawning occurred in the area (Tables 40 and 41). One spent male was captured in August- Specimens with well developed gonads from Lake Michigan were captured in November. No ripe-running individuals were captured. YOY were collected as early as July at Lake Michigan beach stations Q (s. discharge) and later at stations R (n. discharge) and P (s. reference) which is indicative of spawning before July in Lake Michigan. Ripe-running gizzard shad were not captured in Lake Michigan near the D. C. Cook Power Plant either (Jude et al. 1979)- In Pigeon Lake all seven gizzard shad captured had either moderately developed (four fish) or slightly developed (three fish) gonads (Table 41 ) . Gizzard shad inhabit a wide variety of habitats such as large rivers, reservoirs, lakes, swamps, borrow pits, bayous, estuaries and temporary flood water pools (Miller 1970). They are essentially an openwater planktivore although benthic organisms have been found in their guts (Scott and Crossman 1973, Jude 1973)- In Lake Michigan and Pigeon Lake near the Campbell Plant 181 gizzard shad, ranging from 57 to 506 mm, 0.1 to 1990 g, were captured by seine and gill net. No gizzard shad were trawled; Jude et al. (1979) report large adults seem to avoid trawl nets. The length-frequency distribution was bimodal with peaks at 60 mm and 420 mm (Appendix 4). Most sha.d (105) were captured in gill nets set at the 1.5 to 9 m contours in Lake Michigan. Eighty-six were captured in bottom gill nets. Most (146) gizzard shad were captured at night, as they were near the Cook Plant (Jude et al. 1978). Along the southern transect in Lake Michigan, shad were captured at stations P (beach), A (1.5 m) , B (3 m) , C (6 m), D (9 m) , where 6, 40, 21 , 1 1 and 6 fish were caught respectively. Directly off the Campbell Plant, gizzard shad were captured at beach stations R and Q (s. and n. discharge), and 203 TABLE 40. Monthly gonad conditions of gizzard shad caught in Lake Michigan near the J. H. Campbell Plant, eastern Lake Michigan, during 1977 • All fish examined in a month were included except poorly received specimens • Gonad condition Jun Jul Aug Sep Oct Nov Dec Males Slight development Mode development Well developed Ripe-running Spent 4 4 6 22 12 Females Slight development Mode development Well developed Ripe-running Spent Absorbing 1 4 7 2 11 35 Immature 32 11 Unable to distinguish TABLE 41 . Monthly gonad conditions of gizzard shad , caught in Pigeon Lake near the J. Ho Campbell Plant, eastern Lake Michigan, during 1977 . All fish examined in a month were included except poorly received specimens. Gonad condition Jun Jul Aug Sep Oct Nov Dec Males Slight development Mod « d evelopment Well developed Ripe-running Spent Females Slight development Mod . d evelopment Well developed Ripe-running Spent Absorbing Immature Unable to distinguish 20U station L (6 m coutour) where 34, 30 and 27 fish respectively were taken- More were seined at the thermally influenced beach stations Q and R (63 fish) than at the reference station P (6). We feel that significant spawning and production of gizzard shad is occurring in the Grand River. We observed thousands of 2-3 cm gizzard shad along the docks in Grand Haven during the summer of 1977- The Campbell discharge canal is also thought to be prime spawning habitat for shad. Most YOY and many of the adults are thought to have been derived from one of these two sources. Jude et al. (1979) reported seine catches during 1973 and 1974 consisted of immature gizzard shad that seemed to congregate in the beach zone in May and June and from October through December. No gizzard shad were captured during June near the Campbell Plant. Most (144) were caught during September (50 fish) and November (94 fish) when gizzard shad characteristically move into shore or school around the mouth of rivers (Scott and Grossman 1 973) - Jude et al. (1975) reported along shore movement of gizzard shad at least from August to October. At the Campbell Plant gizzard shad were impinged primarily during October through December. Gizzard shad captured during field sampling were most abundant during November as were impinged gizzard shad. In Lake Erie near Detroit Edison's Monroe Power Plant, peak impingement of gizzard shad during certain periods has been attributed to: 1) turbidity, 2) changes in water temperature, 3) schooling behavior and 4) variations in intake pump speed (Eisele and Malar ic 1976). Only seven gizzard shad were captured in Pigeon Lake bottom gill nets during the entire sampling period, six fish at 6 m station M (influenced by Lake Michigan) and one fish at 1 m station Y influenced by Pigeon River. Many more gizzard shad must pass through Pigeon Lake, possibly in the surface layer or in areas not sampled * They may also school around the intake canal as they do around other industrial inlets and outlets (Miller 1960). Eighty-one percent of the gizzard shad were captured at water temperatures between 11 and 15 C with the range being from 9 to 21 C. Near the Cook Plant in southeastern Lake Michigan most gizzard shad were captured in water that ranged from 11 to 19 C. Captures during these periods probably reflected seasonal migration of gizzard shad rather than water temperature preference. Rock Bass — Rock bass, a member of the sunfish family, is native to the freshwaters of eastern central North America (Scott and Grossman 1973) » Within the Lake Michigan drainage basin, rock bass are common (Becker 1976). They are fished commercially in the Great Lakes and Mississippi River, and are a sport fish elsewhere (Scott and Crossman 1973). 205 TABLE 42. Monthly gonad conditions of rock bass caught in Pigeon Lake near the J, H. Campbell Plant, eastern Lake Michigan, during 1977. All fish examined in a month were included except poorly received specimens. Gonad condition Jun Jul Aug Sep Oct Nov Dec Slight development 1 10 7 3 11 Mod. development 14 11 Males Well developed Ripe-running Spent Females Slight development 2 10 10 Mod. development 2 Well developed 1 Ripe-running 2 Spent Absorbing Immature 20 22 20 Unable to distinguish This common pan fish prefers clear, cool water over a gravel or rocky bottom with some vegetation although it inhabits many types of water (Becker 1976). Rock bass spawn in late May and early June at water temperatures between 15-6 and 21.1 C (Becker 1976). In Pigeon Lake near the Campbell Plant, immature (66) and mature (61) specimens were caught from June through November (Table 42) . Two "ripe-running" females were captured in June when spawning probably occurred • Rock bass, like most centrarchids, are nest builders. Coarse gravel is the preferred bottom type for nest building although marl, bedrock and dense beds of aquatic plants have also been reported as nesting sites (Breder and Rosen 1966) . In our study all rock bass (173) were captured in Pigeon Lake at beach stations S (influenced by Lake Michigan), T (influenced by Pigeon River) and V (undisturbed Pigeon Lake). About twice as many rock bass were seined at station T, which is more influenced by the Pigeon River than stations S or V. The majority (128) of the rock bass captured were 45 to 94 mm long, weighed between 1.9 and 18.6 g and were probably age I and II rock bass (Carlander 1977) . One 40 mm YOY was captured in October. The range in length of all rock bass collected was 33 to 199 mm; weights were between 1.1 and 16 1 g. The weights from size classes are similar to other specimens from Michigan and Wisconsin (Hile 1941, 1942, Beckman 1948). 206 Rock bass in the present study were captured predominately at night (149 night captures, 24 day captures). Other studies have shown that this species was equally nocturnal and diurnal (Keast and Welsh 1 968) or inactive at night (Emery 1973)- Net avoidance may have caused lower catches in our day nets. Most (145) rock bass were seined at water temperatures between 15 and 23 C, although the range was between 9 and 23 C. Smaller fish (45-94 mm) were captured during warmer months (June through September) at temperatures of 15-23 C. Brook Silverside — The brook silverside is widely distributed throughout the freshwaters of central North America (Scott and Grossman 1973)- The silverside is commonly found within the southern two-thirds of the Lake Michigan basin, although here they approach the northern limit of their range (Becker 1976). Brook silversides are small forage fishes having a 1 yr life cycle (Hubbs 1921). Spawning usually occurs during early summer when water temperatures reach 20 to 22.7 C (Hubbs 1921, Becker 1976). Eggs, having a long adhesive filament, become attached to aquatic vegetation such as Scirpus and Potamogeton (Bailey 1968) • Spawning may also occur over gravel areas (Hubbs 1921). During our study 159 brook silversides were collected; all but one were collected in Pigeon Lake. Many (59) of the specimens captured from the Campbell area were immature (Table 43). One female with well-developed gonads was captured in June. The date of spawning cannot be estimated from these data. Silversides reside in the upper water layers of lakes, rivers and large streams (Hubbs 1921, Becker 1976).. In the vicinity of the Campbell Plant all (159) brook silversides were seined at Pigeon Lake beach stations T (influenced by Pigeon River), V (undisturbed Pigeon Lake), S (influenced by Lake Michigan) and Lake Michigan beach station P (s. reference) where 92, 42, 24 and 1 were captured respectively. Fifty-eight percent of all silversides were seined at station T which is a very productive, weedy area near the Pigeon River. At Pigeon Lake beach station V, 26? of the silversides were captured, while at station S, which is influenced by Lake Michigan, only ]5% of the silversides were captured. In Lake Michigan only one fish (40 mm) was caught (Appendix 4). Pigeon Lake, a more productive and less harsh environment than Lake Michigan, appeared to be a more suitable habitat for the brook silverside. Jude et al. (1975) did not catch brook silversides during 1973 in the inshore waters of TABLE 43. Monthly gonad conditions of brook silver sides caught in Pigeon Lake near the J. H. Campbell Plant, eastern Lake Michigan, during 1977. All fish examined in a month were included except poorly received specimens. Gonad condition Jun Jul Aug Sep Oct Nov Dec Males Slight development Mode development Well developed Ripe-running Spent 2 2 2 1 1 Females Immature Slight development Mod . development Well developed Ripe-running Spent Absorbing 24 26 Unable to distinguish southeastern Lake Michigan. A few were caught in later years. Silversides captured ranged from 28 to 102 mm and 0*1 to 4.1 g. The distribution of lengths appeared normal with a peak at 60 mm. Most (136) silversides were between 35 and 84 mm long and weighed 0.4 to 2.8 g. Growth of silversides is extremely rapid (Scott and Grossman 1973). Average YOY growth rates from modal lengths were estimated to be 0.81 mm/day from July through September in the vicinity of the Campbell Plant. A higher rate (1.07 mm/day) was estimated for the period July through August, than for the August-September period. More brook silversides were captured at night (124) than during the day (35) (Appendix 4). Perhaps silversides are more easily captured at night as Hubbs (1921) reported that at night adults lie quiescently below the surface while during the day they swam about surface waters . Most of this diel difference in catch is undoubtedly attributable to daytime net avoidance. Silversides (134 of 159) were captured primarily from July through September. Water temperature at capture sites ranged from 9 to 27 C although more (87) silversides were caught between 16 and 17.9 C than at any other temperature. 208 Ninespine Stickleback — The ninespine stickleback is distributed throughout the northern hemisphere in both fresh and salt water (Scott and Grossman 1973). In Lake Michigan, this species is more common in the northern part of the lake, with some indication of an increased abundance in the southern and east central portions in recent years (Wells and McLain 1973). Ninespine stickleback reportedly prefer a cool, quiet water habitat (Becker 1976). Spawning of ninespine sticklebacks is reported to occur in June and July in Lake Superior (Griswold and Smith 1973) and Crooked Lake, Indiana (Nelson 1968b). These authors suggested a spawning season of approximately 8 wks. Multiple spawning within a season occasionally occurs (Scott and Crossman 1973). Maturity in most ninespine sticklebacks was reached by age II in Lake Superior, although earlier maturity at age I was quite common (Griswold and Smith 1973). Reproductive behavior similar to the other gasterosteids is reported. The male constructs a nest of vegetation and debris which is held together by a kidney secretion that hardens on contact with water (McKenzie and Keenleyside 1970). After the female is enticed into the nest and deposits the eggs, they are fertilized by the male who then guards the nest. The present study indicated that ninespine sticklebacks were common in the area of the Campbell Plant, since 134 specimens were caught during 1977 sampling. Nearly all (132 out of 134) ninespine sticklebacks were trawled from Lake Michigan; one was also seined. Only one 60 mm specimen was collected in seine hauls in Pigeon Lake in June. This species was apparently most abundant during June since 87 sticklebacks were trawled in Lake Michigan at depths ranging from 6 to 18 m. Subsequent lower catches from July-December (Appendix 4) may indicate movement of sticklebacks offshore to deeper waters during these months. Monthly gonad condition data summarized in Table 44 suggested the possibility that presence of sticklebacks in the area during June and July may be due to spawning. Many female sticklebacks caught in June and July had well developed to moderately developed ovaries. Except for the occurrence of a single stickleback seined at Lake Michigan beach station Q (n. discharge) in June, the ninespine stickleback was notably absent from the nearshore (less than 6 m) waters of Lake Michigan near the Campbell Plant. Temperatures at time of capture ranged from 4-24 C, with 94 % of all sticklebacks caught between 4 C and 12 C, which agreed closely with findings from Crooked Lake, Indiana where adults were caught in 5-25 C waters with most caught from 6-12 C (Nelson 1968b). In agreement with observations by Jude et al. (1975) and Griswold 209 TABLE 440 Monthly gonad conditions of ninespine sticklebacks in Lake Michigan near the J. H. Campbell Plant, eastern Lake Michigan, during 1977 . All fish examined in a month were included except poorly received specimens. Gonad condition Jun Jul Aug Sep Oct Nov Dec Males Slight development 13 Mode development 7 Well developed 2 Ripe- running Spent 1 2 5 5 Females Slight development Mod . d evelopmen t Well developed Ripe-running Spent Absorbing 11 36 1 1 3 Immature Unable to distinguish and Smith (1973) lower catches of ninespine stickleback occurred during day sampling, with only 23 of the 134 specimens in the present study caught during the day (Appendix 4). This observation, along with the absence of sticklebacks from water less than 9 m during the day, suggested a limited offshore movement- during daylight hours . Although 1977 data suggested that Pigeon Lake was seldom utilized by ninespine sticklebacks (only one caught), preliminary observation of 1978 data as well as 1975 impingement data (Consumers Power Company 1975) showed that sticklebacks were quite common in Pigeon Lake during spring. The reason for their presence is not yet certain, but the debris-covered bottom of Pigeon Lake as well as its protected nature, may make it an optimum spawning area. Spawning in Pigeon Lake was evidenced by the occurrence of stickleback larvae in June at Pigeon Lake beach station S (influenced by Lake Michigan). Spawning probably occurred sometime in May. In situations where they are abundant, ninespine sticklebacks are important as forage for other game species (Scott and Crossman 1 973) - In the area of the Campbell Plant this species has been found in the stomachs of yellow perch, however its importance to other species is yet to be determined. 210 Brown Bullhead — The native distribution of brown bullhead is restricted to fresh waters and, rarely, brackish waters of eastern and central North America (Scott and Grossman 1973)- It is dispersed throughout the Lake Michigan basin (Becker 1976) and generally inhabits weedy and deeper waters of lakes and sluggish rivers (Hubbs and Lagler 1964). The brown bullhead makes up the major portion of the commercial catch of all bullhead species and may provide some sport for fishermen as it readily takes bait (Scott and Crossman 1 973) • It is well adapted to pond culture, but has not been commercially raised because of low demand (Bardach et al. 1972). The brown bullhead was a common species in Pigeon Lake where it accounted for approximately 0.58? of the total catch* None were caught in Lake Michigan. Of the 120 specimens collected, 82 were caught at beach station T (influenced by Pigeon River), 23 at openwater station I (undisturbed Pigeon Lake), 9 at openwater station M (influenced by Lake Michigan) and 6 at beach station V (undisturbed Pigeon Lake). Located in areas of soft bottom with abundant aquatic vegetation near Pigeon River, stations T and Y were the most preferred habitats for the brown bullhead in Pigeon Lake. Beach station V which consisted of extensive shallow water with moderate aquatic vegetation was only sparingly used by this species . A small number of large brown bullheads seemed to remain during most of the sampling period in the relatively deep waters of station M. One or two specimens were collected at this station every month except in July. Beach station S (influenced by Lake Michigan) with a sandy bottom and relatively deep water close to the shoreline, was apparently not used as a spawning or nursery ground. No brown bullheads were collected there. YOY brown bullheads ranging from 23-79 mm were restricted to shallow areas and were collected only by seine. Of the 34 adults, 32 were caught by bottom gill nets and two by beach seine. Raney and Webster (1939) reported that adult brown bullheads moved at night from deeper waters into shallow bays. Similar movements probably occurred in Pigeon Lake, but large fish often successfully avoided the seine. Brown bullheads spawned from March to May in Florida and in June in Michigan and Wisconsin (Carlander 1969). Spawning may continue through September in Alabama (Swingle 1957). Both parents guard the nest and young (Breder and Rosen 1966). Our gonad data (Table 45) showed that spawning in Pigeon Lake took place in May and June in areas not influenced by Lake Michigan, with beach station T apparently being the most important spawning ground. YOY first appeared in the July collection which included 30 specimens measuring from 23-62 mm in total length (Appendix 4). This 211 TABLE 45 m Monthly gonad conditions of brown bullheads caught in Pigeon Lake near the J. H. Campbell Plant, eastern Lake Michigan* during 1977 . All fish examined in a month were included except poorly received specimens • Gonad condition Jun Jul Aug Sep Oct Nov Dec Males Slight development Mod . d evelopment Well developed Ripe-running Spent 3 3 1 1 Females Slight development Mod . d evelopment Well developed Ripe-running Spent Absorbing 2 1 3 4 2 Immature 30 22 Unable to distinguish sample represented the highest monthly catch of YOY brown bullheads during our study. Catches of YOY generally continued to decrease from August to November as these fish became less abundant and less vulnerable to the seine . Twenty- two YOY were caught in August, five in September, ten in October and two in November (Appendix 4). Dispersal of YOY following a change in schooling behavior may partially explain the sharp decline in catch observed in September . In Cayugua Lake, New York, YOY brown bullhead spawned in June grew to an average length of 36.9 mm by late July, 42 mm in August and 68.0 mm in October (Raney and Webster 1939). The Pigeon Lake YOY showed comparable growth reaching an average length of 380 2 mm, 44.0 mm and 66.0 mm for the above three months respectively. The five YOY caught in September were larger fish, ranging from 67 to 82 mm in size. Adult brown bullheads were found in all monthly collections from Pigeon Lake. Catches of adults in June (7 specimens), in October (9) and in November (13) were higher than those of July (2), August (2) and September (1) (Appendix 4). This change in seasonal distribution may be related to parental care activity. In July, August and September, adult brown bullheads which were guarding their young were probably less active and therefore less likely to be caught in our fishing gear. High catches of brown bullhead at night (112 out of 120 specimens) agreed 212 with the known nocturnal habit of this species (Scott and Crossman 1973). Only two brown bullheads in the 100-200 mm size group were represented in our collections (Appendix 4). Size segregation between intermediate and large brown bullheads may occur with intermediate sized fish in well protected and less sampled areas. Brown bullheads were never collected in Lake Michigan. Water temperatures at the time of capture for brown bullheads ranged between 8.0 and 23.4 C. YOY were mostly collected at higher temperatures (16-23*4 C) , while adults were caught at water temperatures between 8.0-12.0 C. Twenty- five of the 35 adults and YOY collected between 8.0-12 C contained food in their stomach, indicating they were actively feeding at this temperature range. Brown bullheads appeared to have sucessfully dominated the other two species of bullheads in Pigeon Lake (see Black and Yellow Bullhead sections), probably because browns are best suited for this type of habitat. In a study on the fishes of Ohio, Trautman (1957) indicated that the black bullhead was unable to invade cool, deep waters inhabited by the brown bullhead, and that abundance of the yellow bullhead in an area may be limited by the presence of the other two species. The brown bullhead was reported to hybridize with the black bullhead in western Lake Erie and in small impoundments in Ohio in areas where only submarginal habitats existed for one or both species (Trautman 1957)- Hybridizaton probably also occurred in Pigeon Lake as we occasionally found specimens possessing intermediate characters between the two species. Northern Pike — The northern pike is found throughout the northern hemisphere, being widely introduced from its native North America (Scott and Crossman 1973)- It is common throughout the Lake Michigan basin (Becker 1976). Northern pike are frequently found in cool to warm lakes, ponds and sluggish rivers. They often prefer shallow, weedy areas during the spring and fall and deeper, cooler water during summer (Hubbs and Lagler 1958). Most of the Pigeon Lake/Pigeon River area represents excellent habitat for northern pike and in addition, it offers large, shallow, weeded areas and the Pigeon River floodplain which pike undoubtedly required for successful spawning. Our catch data combined with results from the mark and recapture study (see MARK AND RECAPTURE) showed that a large population of northern pike existed in Pigeon Lake. Michigan Department of Natural Resources personnel have collected northern pike for spawning stock from Pigeon Lake because of the abundance of this species in the lake (John Trimberger. Personal communication, Michigan Department Natural Resources, Grand Rapids, Michigan). 213 Pike were caught during every month of the study period, June through December. Although none were caught in Lake Michigan, Campbell Plant personnel reported that ice fishermen caught northern pike near the jetties during winter months. Heated water is pumped to the jetties to keep the intake area ice-free and pike might be attracted there because of higher water temperature or a more abundant food supply. Pike were caught at all stations in Pigeon Lake. Similar numbers of pike were caught at the two openwater gill netting stations, M (influenced by Lake Michigan) and I (influenced by Pigeon River), while more pike were caught at beach stations S (influenced by Lake Michigan) and T (influenced by Pigeon River) than at V (undisturbed Pigeon Lake)c Station V is located in a large shallow area, while at the other two stations the bottom is steep with dropoffs. The reason for higher catches at beach stations S and T could be a preference for habitat near deep water. Pike were caught by electrofishing in large numbers at station V between the seining area and the deeper water offshore. Total catch of northern pike using seines and gill nets during the study was 113 fish; monthly catches varied from 7 to 29 fish (Appendix 4). More pike per month were caught in gill nets from September-December than from June-August. This could indicate greater activity as water temperature cools, but does not support the idea that pike move to cooler water during summer months. Large pike were caught throughout the year in both seines and bottom gill nets. Although no age determinations were done, it is possible to make reliable estimates of growth during the study period based on catch data. Five pike (40-84 mm) were caught in June which were probably YOY. Other pike caught in June were at least 300 mm. Carbine (1945) found pond-reared YOY pike as large as 446 mm by October 14 c It was more likely that the 300 mm pike caught in June was a yearling. Size ranges for YOY northern pike in Pigeon Lake were as follows: July: 82-177 mm; August: 129-232 mm; September: 209-252 mm; October: 246 mm (one fish); November: 170-330 mm. High growth rates found by Carbine were probably due to warmer water temperatures, abundant food and a lack of large predators. Growth values obtained for Pigeon Lake pike were high relative to Carbine's data. Rapid growth by Pigeon Lake pike could be due to an abundant supply of food and warm water temperatures . Pigeon Lake served as a spawning area for some typical Lake Michigan species (alewives, spottails) as well as for resident Pigeon Lake species and does have large numbers of small prey fish suitable for YOY pike. Two YOY northern pike (102, 124 mm) caught during July were feeding on alewives. Larger northerns find a seasonal supply of food from migrating salmonids entering Pigeon Lake. An unidentified salmonid (375 mm, 300 g) was eaten by a pike (835 mm) caught on 18 October. 2lU Females TABLE 46 # Monthly gonad conditions of northern pike caught in Pigeon Lake near the J. H. Campbell Plant, eastern Lake Michigan, during 1977. All fish examined in a month were included except poorly received specimens. Gonad condition Jun Jul Aug Sep Oct Nov Dec Slight development 4 7 4 2 111 Mod. development 3 3 4 8 Males Well developed 1 1 Ripe- running Spent Slight development 2 16 1 Mod. development 1 4 4 2 3 Well developed 1 6 Ripe- running Spent 1 Absorbing Immature 5 7 12 1 Unable to distinguish 111 18 3 Pigeon Lake species eaten by pike included: grass pickerel, lake chubsucker and largemouth bass. Northern pike up to 933 mm were caught during regular sampling. The largest individual weighted 5300 g. Age analysis for large pike is being considered for the 1978 study. Northern pike gonads were found to be at some stage of sexual development from June-December (Table 46). Spawning generally occurs just after the ice leaves and has been reported during April in Michigan (Carbine 1942). All adult pike captured had spawned by the time the study began in late May-early June. Some YOY showed such gonadal development in November that they would be expected to spawn the following year. This rapid development has been noted by Navratil (1954), Calderon-Andreau (1955) and Fedin (1958) (as cited in Machniak 1975) and is regarded as exceptional. Northern pike appeared to be growing and propagating well in Pigeon Lake. Minor Species Bowfin— - The bowfin is the only surviving member of an ancient fish family that has long been extinct (Hubbs and Lagler 1964). Bowfin occur only 215 in North America and inhabit swampy, vegetated bays of warm lakes and rivers (Scott and Grossman 1973)- In Michigan, the northern limit of their distribution reaches the southern portion of the Upper Peninsula (Becker 1976). Seventy bowfin were collected in this study, all from Pigeon Lake. Of these, 3^ were caught by gill net at Pigeon Lake openwater station M (influenced by Lake Michigan), 33 by gill net at Pigeon Lake openwater station Y (influenced by Pigeon River) and three by seine, one from each of the three beach stations. Although the bowfin was mostly caught in deeper parts of the lake, it also frequented shallow areas. During electrofishing several individuals were seen in the shallow areas, but evidently most were quite successful in escaping the beach seine. Our catch included mostly larger fish with a size range from 358 to 720 mm (Appendix 4). Young bowfin are believed to remain in deep water or in areas with dense vegetation and are therefore rarely seen after the schools disperse (Scott and Grossman 1 973) • Bowfin were caught over a broad range of water temperatures (2.4-26.9 C) with most catches occurring between 8.0 and 19*0 C. Station M, which remained relatively warm during colder months, served as a winter refuge for the bowfin. Fifty per cent of the bowfin catch at this station was made in December at water temperatures between 2.4 to 3.2 Co No bowfin were collected in our day gill net set in December at station Y (influenced by Pigeon River) where water temperature was only 0.5 C. Station Y and probably other areas not disturbed by the inflow of Lake Michigan waters were preferred habitats during warmer months . The bowfin, which represented 0.34$ of the Pigeon Lake catch, was one of the important predators in this lake. Since bowfin are not a popular game fish (Hubbs and Lagler 1964), we believe their population has remained high in Pigeon Lake. This species was reported to prey on all kinds of fish and may become a serious competitor and predator of sport fishes (Scott 1938, Scott and Grossman 1973)- Our data, however, did not permit any evaluation of the influence of this species on the sport fishes of Pigeon Lake. Most bowfin collected (67$) had empty stomachs, while stomach contents of the remaining 33% included alewives, gizzard shad, spot tail shiner, unrecognizable fish and remains of other animals. Aquarium observations suggested that bowf ins used scent as much as sight for feeding (Scott and Grossman 1973)- Carlander (1969) reported that the bowfin often feeds at night. Our data, which included 47 fish caught at night and 23 during the day (Appendix 4), indicated that the bowfin tended to be more nocturnal than diurnal . In December, however, for unknown reasons, more bowfin were caught during the day (10) than at night (7)- 216 TABLE 47. Monthly gonad conditions of bowfins caught in Pigeon Lake near the J. H. Campbell Plant, eastern Lake Michigan, during 1977. All fish examined in a month were included except poorly received specimens. Gonad condition Jun Jul Aug Sep Oct Nov Dec Males Slight development Mod . d evelopmen t Well developed Ripe- running Spent 1 3 2 2 3 6 1 1 6 3 Females Slight development Mod. development Well developed Ripe- running Spent Absorbing 2 1 1 1 2 1 4 3 1 8 7 6 2 Immature Unable to dis stinguish 1 2 Bowfin spawn in April in Illinois, in June in Ontario and from April to July over its entire range (Carlander 1969)- The male builds the nest in shallow, vegetated areas of lakes and streams and guards the young until they reach approximately 102 mm in length (Scott and Crossman 1973)- Our gonad data (Table 47) indicated that spawning in Pigeon Lake probably took place in June and July* The bowfin was represented in all monthly samples (Appendix 4). Low catches in June and July were perhaps related to spawning activities. During this period most bowfin likely remained in well protected areas guarding their nest or young and were therefore able to avoid gill nets and seines. Monthly catches ranging from 9 to 17 fish during the period August-December (Appendix 4) increased markedly over those of the previous 2 months. Adult bowfin probably left their young in August, September and October and became more vulnerable to our fishing gear during this period and later months as they resumed a more active search for food. Bowfin probably rarely entered Lake Michigan. No bowfin were caught in Lake Michigan near the Campbell Plant and only one specimen was collected in 1973 in a similar study at the Cook Plant in the southeastern part of the lake (Jude et al. 1975). 217 Coho Salmon — Coho or silver salmon naturally occur in the Pacific Ocean and tributaries from Montery, California to Point Hope, Alaska (Scott and Grossman 1973)- The introduction of coho began in Michigan during 1966 when 660,000 smolts were planted in three Lake Michigan tributaries (Wells and Mc Lain 1973* Becker 1976) • Coho were selected to provide a put-and-take sport fishery and to prey upon the abundant alewives (Tody and Tanner 1966, Parsons 1973). The Campbell Plant is located 21 km from the Grand River, 47 km from the Muskegon River and 19 km from the Black River where 210,000, 175,000 and 100,000 smolts respectively were released during 1977- Most of the released coho were between 100 and 152 mm (M. Patriarche, personal communication, Institute of Fisheries Research, University of Michigan, Ann Arbor, Michigan) . Although a 1933 planting of coho in Lake Erie failed to establish a self-sustaining population, natural reproduction of coho in Lake Michigan tributaries has been documented (Parsons 1973) - Studies are under way to determine the extent of natural reproduction (M. Patriarche , personal communication). Normally, adult coho return to their natal streams to spawn after 18 months in the Great Lakes or ocean. Upstream migrations of adults begin during early fall with actual spawning beginning in October and November in swift, shallow gravelly areas (Godfrey 1 965) - From early March to late July fry emerge from gravel beds (Tody and Tanner 1966) « A few may migrate downstream but generally they reside in shallow gravel areas of the natal stream for 1 yr. Yearling coho smolt then begin their downstream migration in March or April. The upper reaches of the Pigeon River in the vicinity of the Campbell Plant have not been examined for presence of coho fry« Six mature adults were captured during the spawning season (September and November), but only one coho, a male with slightly developed gonads, was captured in Pigeon Lake. The other coho were captured in Lake Michigan with bottom gill nets at depths of 3, 6, 9 and 12 m. Two factors may account for the low number of adults caught near the Campbell Plant: ( 1 ) the area is not particularly close to any of the tributaries where coho are planted annually and (2) the Pigeon River has an organic, muddy bottom which may not be conducive to successful spawning* Fifty-five coho salmon were caught during 1977. Of these, 85? were caught during June at all Lake Michigan beach stations (P, Q and R) during night sampling. Coho caught during the June period were small immature fish (88-113 nam, 5.5-11-9 g) . Tody and Tanner (1966) reported that for the first few months of summer coho remained close to shore where they fed on small forage fish and crustaceans. June data showed evidence of inshore habitation by small coho* Although these coho (88-113 mm) were smaller than the average planted coho (100-152 mm), 218 most coho probably originated from stocking of the Black, Muskegon and Grand Rivers. However, natural reproduction is possible, A current cooperative multi-state tagging program should clarify the origin of coho in the vicinity of the Campbell Plant (M. Patriarche, personal communication) . When coho are approximately 100 mm, they move offshore following the thermocline (Phillips 1977). In the present study, no coho were captured during July and August but in September and November eight coho (140-421 mm, 126-825 g) were captured in offshore bottom gill nets at depths of 3 i 6, 9 and 12 m- Capture sites and dates show evidence of the characteristic movement of this species: inshore activity during early spring to early summer, offshore movement following the thermocline as summer progresses and return to inshore water in the fall as the thermocline disintegrates (Engel and Magnuson 1971). Movement of salmon seems to be correlated with temperature- Adult coho preferred a water temperature of about 11.6 C (Tody 1973). Edsall et ai. (1974) found that peak rate of food conversion occurred at 12 C for coho, although highest growth rate occurred at 15 C. In this study, smallest coho (mean length 97 mm) were captured at 13 C water temperatures, while the majority of coho (mean length 129 mm) were captured at 10.6 C. The largest coho (mean length 198 mm) were captured in 9 C range. In comparison, during 1974 near the Cook Plant (Jude et al. 1978), smallest coho (70-90 mm) were caught at warmer water temperatures (23 C) near the upper lethal limit (25.1 C) (Brett 1952). Yearlings (100-170 mm) were captured at temperatures between 11-17 C while larger fish were taken from water temperatures of 11 C or less. Their data showed small fish inhabited warmer inshore waters during early summer, while larger fish inhabited cooler offshore waters. Night captures predominated near both the Cook Plant and the Campbell Plant . Tadpole Mad torn — The tadpole raadtom is distributed throughout the Lake Michigan basin except for its extreme northern portions (Becker 1976). Tadpole madtoms inhabit slow moving streams and shallow areas of lakes with soft, muddy bottom and abundant aquatic vegetation (Scott and Grossman 1973). All 55 tadpole madtoms were seined in Pigeon Lake (Appendix 4). Pigeon Lake beach station T (influenced by the Pigeon River) and V (undisturbed Pigeon Lake), both similar to the typical habitat of tadpole madtom, were more productive than beach station S (influenced by Lake Michigan) contributing respectively 36 and 17 specimens. Only two madtoms were seined at station S. This species made up approximately 0.21% of our Pigeon Lake catch. Like young bullheads, tadpole madtoms 219 were never taken in bottom gill nets. The tadpole madtom was represented in all monthly samples during the summer and fall (Appendix 4). We lacked sufficient gonad data (Table 48) to determine spawning time for this species . Tadpole madtoms were reported to spawn during May in Wisconsin (Becker 1976), July in Illinois and Iowa (Carlander 1969) and late June or early July in Canada (Scott and Crossman 1973)- Our samples included only seven mature fish from 74 to 89 mm in total length, all of which had poorly or moderately developed gonads. Among the 44 immature tadpole madtoms collected, those caught in June and July (40-68 mm) were on the average larger than those caught in August, September, October and November (size range 29-58 mm) . Comparison with the age-length data reported by Carlander (1969)* suggested that the first group was composed of yearlings while the second group was mostly YOYo The madtom is known to be active nocturnally and to seek cover such as holes under logs or empty cans during the day (Scott and Crossman 1973) . In our study more fish were caught at night (35), but an appreciable number (20) were collected during the daye Water temperatures at the time of capture ranged from 8.0 to 23 c9 C; most tadpole madtoms were caught between 10 and 19 C. Although tadpole madtoms were reported to be eaten by larger fishes (Scott and Crossmann 1973), they have not been found in stomachs of predatory fish examined in our study . Slimy Sculpin — Aside from occasional use as bait by trout fishermen (Dymond 1926) the slimy sculpin is a little known species common to Lake Michigan (Becker 1976)- Slimy sculpins in Lake Michigan are reported to occupy the nearshore habitat to a depth of approximately 90 m (Deason 1939) • Spawning of this species is typical of the genus Cottus > Eggs are deposited on the undersurfaces of rocks, logs or other structures and fertilized by the male who then guards the nest (Koster 1936). Temperature at time of spawning for this sculpin was reported as 5-10 C from different localities in New York (Koster 1936) and 8 C in the Montreal River (Van Vliet 1964). Spawning occurred in Lake Michigan before early May in 1964 (Rottiers 1965); however, no temperatures were given, A monthly summary of gonad conditions for slimy sculpins caught in the present study (Table 49) showed that a few sculpins caught in June and 22 caught in December had moderate to well developed gonads. However, our collections were taken after the spawning season of this species, so exact time of spawning in the area of the Campbell Plant can not be confirmed using 1977 data* Most slimy sculpins from Lake Michigan reached sexual maturity at 220 TABLE 48. Monthly gonad conditions of tadpole madtoms caught in Pigeon Lake near the J. H. Campbell Plant, eastern Lake Michigan, during 1977. All fish examined in a month were included except poorly received specimens. Gonad condition Jim Jul Aug Sep Oct Nov Dec Males Slight development Mod, development Well developed Ripe-running Spent 2 1 1 Females Slight development Mod. development Well developed Ripe-running Spent Absorbing 1 2 Immature 8 10 1 9 4 12 Unable to distinguish 1 2 1 . — TABLE 49* Monthly gonad conditions of slimy sculp ins caught in Lake Michigan near the J. H. Campbell Plant, eastern Lake Michigan, during 1977 o All fish examined in a month were included except poorly received specimens. Gonad condition Jun Jul Aug Sep Oct Nov Dec Males Slight development Mod* development Well developed Ripe-running Spent 7 9 Females Slight development Mod . d evelopmen t Well developed Ripe-running Spent Absorbing 1 1 2 4 Immature Unable to distinguish 221 age III (Rottiers 1965). Rottiers also noted that all fish shorter than 55 mm were immature; whereas, all fish longer than 70 mm were mature . This agreed well with results of the present study which found all fish longer than 66 mm mature. Out of 53 slimy sculpins caught in the present study, 44 were trawled from Lake Michigan. The remaining nine specimens were all seined at Pigeon Lake beach station S (influenced by Lake Michigan). It is apparent from our data that slimy sculpin preferred the Lake Michigan habitat, since none were caught at other stations in Pigeon Lake. Apparently this species remains offshore in deeper water during summer and fall months. Six slimy sculpins were caught at depths of 15 to 21 m during June and July and two were caught at 15 m between October and December; none were caught at depths exceeding 15 i. Most slimy sculpins caught in trawls (40 out of 44) were taken at water temperatures less than 7 Co This value closely agreed with the reported preference of 6 C for this species (Rottiers 1965). Wells (1968) noted that trawled slimy sculpins from Lake Michigan were most frequently caught in water that was 4-5 C. Temperatures at time of capture of specimens seined at Pigeon Lake beach station S ranged from 11.0 to 21.8 C. Only two sculpins there were taken at water temperatures exceeding lie 2 Co Symons et al. (1975) indicated that in laboratory studies individual sculpins varied widely in their choice of water temperature, although none preferred the extremes (3 or 21 C) . A monthly summary of catch by size group and diel period (Appendix 4) showed that there was a tendency to catch smaller sculpins in June - July compared with October - December. Absence of sculpins from Lake Michigan samples in August and September may be indicative of an offshore movement during these months with subsequent return of larger (mature) specimens to the area in October - December, followed by return of smaller sculpins in early spring and summer. The nocturnal behavior of this species suggested by Jude et al. (1975) and Hubbs and Lagler (1964) concurred with observations of the present study. Forty-three of the 53 slimy sculpins caught in the area of the Campbell Plant were taken at night. Slimy sculpin in the area of the Campbell Plant are undoubtedly an important food for sport fish, particularly brown trout and lake trout for at least part of the year6 One lake trout examined from this area contained 17 slimy sculpins. In addition many brown trout caught in the area (30) had eaten slimy sculpins. We expect the slimy sculpin will behave in a fashion similar to that observed at the Cook Plant, where after installation of intake and 222 discharge riprap, they colonized the area and developed large populations. Many adults were impinged and larvae were entrained. The same pattern is expected for the future offshore intake and discharge structures at Campbell if a similar apron of riprap is used for the structures . Grass Pickerel — A close relative of the northern pike, the grass pickerel, is a common resident of the quiet, weedy waters of the lower half of the Lake Michigan drainage basin (Becker 1976). This species is a smaller member of the pike family with a maximum reported size in the United States of 381 mm, 397 grams (Trautman 1957) • Due to its size, the grass pickerel has little importance as a sport fish, and no importance commercially. Grass pickerel are known to hybridize in nature with northern pike, producing infertile offspring (Scott and Crossman 1 973) - Spawning usually occurs during April in Ontario (Crossman 1962) and Wisconsin (Kleinert and Mraz 1966), but there is evidence of low intensity fall spawning (Scott and Crossman 1973). No. fish collected in the present study during late summer or early fall exhibited the advanced state of gonad development which necessarily preceeds spawning (Table 50). This leads us to believe that spring spawning was more likely in our area. Grass pickerel build no nests, but rather abandon their eggs after spawning (Scott and Crossman 1 973) • These authors report that the eggs are demersal and slightly adhesive. Sexual maturity in grass pickerel occurred at a minimum of 157 nun in males and 141 mm in females in Jones Creek, Ontario (Crossman 1962). Our data suggest similar length-at-maturity values. Specimens captured ranged in length from 70 to 290 mm (Appendix 4). The grass pickerel is a fairly common inhabitant of Pigeon Lake, being recorded from all months in which seining was performed. Most (14) were collected in August. There is an apparent preference for shallow nearshore habitat as 48 of the 50 grass pickerel were seined in areas of gradual slope, stations T (influenced by Pigeon River) and V (undisturbed Pigeon Lake). Only one grass pickerel was seined at station S (influenced by Lake Michigan), which has a steep slope, and one was gillnetted at station Y (influenced by Pigeon River). No apparent preference for either diurnal or nocturnal activity was noted (Appendix 4). None were taken in Lake Michigan. Catch temperature ranged from 8.0 to 26.5 C. Preferred temperature of grass pickerel is reported to be 25*5 C (Crossman 1962), indicating that this species is tolerant of relatively high temperatures. Grass pickerel in Pigeon Lake function ecologically as both predator and prey. Grass pickerel have been found in the stomachs of 223 TABLE 50. Monthly gonad conditions of grass pickerel caught in Pigeon Lake near the J. H. Campbell Plant, eastern Lake Michigan, during 1977 . All fish examined in a month were included except poorly received specimens <, Gonad condition Jun Jul Aug Sep Oct Nov Dec Males Slight development Mod. development Well developed Ripe-running Spent 3 4 1 2 2 1 1 2 Females Slight development Mod. development Well developed Ripe-running Spent Absorbing 2 1 1 2 1 1 1 2 1 1 2 Immature 1 4 6 1 Unable to distinguish 1 2 1 northern pike. In turn, grass pickerel stomachs have contained yellow perch, lake chubsucker, bluntnose minnow and golden shiners. The habitat of Pigeon Lake, as well as the abundant food supply is highly conducive to the survival and propagation of this species. Brown Trout — Brown trout were first introduced to Lake Michigan in 1883 (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). Little has been written on brown trout habitat requirements in lake environments, but in streams, this species is more tolerant of warmer waters and lower oxygen levels than the brook trout, and as such is able to survive in relatively marginal habitats (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 km from the point at which they had been released, though most of the recovered fish were found less than 24 km away (Becker 1976) . A total of 49 brown trout were captured from June to November in Lake Michigan during this study; none were ever collected from Pigeon 12k TABLE 51. Monthly gonad conditions of brown trout caught in Lake Michigan near the J. H. Campbell Plant, eastern Lake Michigan, during 1977. All fish examined in a month were included except poorly received specimens. Gonad condition Jun Jul Aug Sep Oct Nov Dec Males Slight development Mod. development Well developed Ripe-running Spent 2 1 3 3 2 7 5 Females Slight development Mod . development Well developed Ripe- running Spent Absorbing 1 1 1 1 1 1 4 1 1 1 Immature Unable to distinguish Lake (Appendix 4). Most fish were collected during September (15), November (14) and June (11). Thirty-nine of the fish (measuring 200 to 680 mm) were caught by gill net and ten (mostly between 130 and 200 mm) were collected by seine. Seventy-seven percent of the fish were caught at night, which concurred with Brynildson et al. (1973) who noted peak periods of activity for brown trout occurred during the evening, night and early morning . All but three brown trout were taken in water 6 m deep or less. Similar numbers of brown trout (10-14 per station) were captured at U5, 3 and 6 m. Our gonad development data (Table 51) suggested that spawning took place from the latter part of September to November, which is consistent with the findings of Jude et al. (1975), Scott and Grossman (1973) and Becker (1976)- Spawning generally occurs in water temperatures of 6.7 to 8*9 C (Scott and Crossman 1973) and seems to be induced by the shortening periods of daylight during fall (Brynildson et al- 1973). Approximately 60$ of the brown trout captured had food in their stomachs. Fish were found most often in the stomachs of larger (greater than 600 mm) specimens. One 668 mm individual had ingested 12 alewives averaging 35 mm in length. In fact, during June - December 1977 alewives were the only recognizable fish found in brown trout stomachs. During April 1978 however, slimy sculpins predominated the diet, while rainbow smelt were also found in some stomachs. Brynildson et al. 125 (1973) reported that the diet of brown trout larger than 228 mm was composed largely (up to 70$) of fish. The number of seined brown trout less than 254 mm increased with increasing water temperature at Lake Michigan beach stations during June; at stations Q (8*0 C), P (9-5 C) and R (10.6 C) , zero, one and six brown trout respectively were caught. In a comparable 1973 study of Lake Michigan near the Cook Plant by Jude et al. (1975), brown trout were found most frequently at water temperatures from 6 to 16 C, which coincided closely with our findings where most brown trout were caught in 7 to 13 C waters. The brown trout is one of the more wary game fish, and as such is challenging to catch. Thus, because of its good growth (up to 242 mm/yr, Becker 1976) and excellent eating quality, brown trout are a popular species among Lake Michigan anglers. Lake Chubsucker — . The lake chubsucker is a common species in the southern half of lower Michigan where it occurs in lakes, ponds, rivers and quieter streams (Becker 1976)* This species is apparently near the northernmost limit of its range in Michigan. Although this species is of little or no direct importance as a commercial or sport fish, it undoubtedly serves as a forage species and has been observed in the stomachs of both northern pike and grass pickerel in Pigeon Lake. A small resident population of lake chubsuckers, does exist in Pigeon Lake. All 46 lake chubsuckers (50-210 mm) in the present study were seined at beach stations in Pigeon Lake (Appendix 4). Most (18) were collected in June. The capture of 43 chubsuckers at station T (influenced by Pigeon River) suggested a preference by this species for a more riverine habitat. Of the three remaining chubsuckers, two were caught at station S (influenced by Lake Michigan) and one was caught at station V (undisturbed Pigeon Lake). Water temperature range at time of capture was 8.0-23.4 C. Most lake chubsuckers were 45-95 mm (about 2 yr old, Carlander 1969), but some larger fish up to 210 mm were also captured (Appendix 4). Age growth data summarized by Carlander (1969) indicated extreme variability in growth of this species. Spawning occurs from May to June. Whether this species spawned in Pigeon Lake or in the further reaches of the Pigeon River is unknown . Due to rapid deterioration after death, the sex and gonad conditions of most lake chubsuckers were difficult to distinguish. Hence we have no clues as to spawning time or location in Pigeon Lake* 226 Longnose Sucker — The longnose sucker is restricted to the northern portion of North America, Lake Michigan being the southern edge of its range (Becker 1976). Although this species sometimes occurs in large numbers, its contribution to the commercial catch of all sucker species in the Great Lakes is low (Bailey 1969). Thirty-six longnose suckers were collected, all from Lake Michigan; 16 in July, 13 in August, 6 in September and 1 in November (Appendix 4). This species appeared to be relatively uncommon near the Campbell plant, compared to other areas in Lake Michigan,, Jude et al. (1975), with greater fishing effort, collected 85 specimens in 1973 in the vicinity of the Cook Plant (southeastern Lake Michigan), With the exception of one specimen trawled in November, all longnose suckers were caught in gill nets, 23 at night and 12 during the day. Of the gillnetted specimens all were caught in bottom gill nets except one taken in a surface net set in July- Of the 23 fish collected in gill nets at night, 4 were caught between the 9 and 12 m depths, 19 between 3 and 6 m and 1 at 1.5 m. All day catches were made at the 6 m contour. Although large numbers of longnose suckers were found at greater depths in other areas (Harris 1962, Jude et al. 1975, Listen and Tack 1975), they seemed to prefer the 3-6 m contours near the Campbell Plant. These data also indicated that longnose suckers tended to be more active and occupied a wider inshore area at night than during the day. Longnose suckers probably seldom enter Pigeon Lake as none were collected there and only one was reported impinged at the Campbell Plant during the period January 1974 - March 1975 (Consumers Power Company 1975) . However, adults may use the Pigeon River for spawning in spring. Longnose suckers collected ranged in size from 249 to 570 mm in total length, the majority being large individuals (Appendix 4). This species was reported to spawn in spring in streams or shallow areas of lakes when streams were not available (Scott and Grossman 1 973) «> Near the Cook Plant, southeastern Lake Michigan spawning probably took place in late March, April or May (Jude et al. 1975). In 1977, our study started after the reported spawning season of longnose sucker and gonad condition data from 1977 (Table 52) were inconclusive. Preliminary observations of gonad conditions of fish caught in spring 1978 indicated that longnose suckers spawned in early April or May. The low catch of longnose suckers in April 1978 (only one specimen collected) suggested that spawning occurred outside the study area. As the longnose sucker normally spawns in streams, it was suspected that it may utilize Pigeon River as a spawning ground. No longnose suckers, however, were collected in Pigeon Lake in this study. 227 TABLE 52. Monthly gonad conditions of longnose suckers caught in Lake Michigan near the J. H. Campbell Plant, eastern Lake Michigan, during 1977c All fish examined in a month were included except poorly received specimens. Gonad condition Jun Jul Aug Sep Oct Nov Dec Males Slight development Mod* development Well developed Ripe- running Spent 4 3 Females Slight development Mod* development Well developed Ripe-running Spent Absorbing 1 1 1 2 Immature Unable to distinguish The longnose sucker is a cold water species • Only one individual was caught at water temperatures above 15 C. The majority were collected between 7 and 12 C. Yellow Bullhead— The yellow bullhead is widely distributed throughout the Lake Michigan basin (Becker 1976). It usually occurs in slow-moving streams, shallow bays of lakes and in ponds with abundant aquatic vegetation (Trautman 1957)- This species has little commercial importance and comprised only a small fraction of the total catch of all bullhead species in the United States (Scott and Grossman 1973) • In the vicinity of the Campbell Plant, yellow bullheads are probably restricted to Pigeon Lake as none were caught in Lake Michigan. The 35 specimens collected made up approximately 0*17$ of the total Pigeon Lake catch (Table 14 and Appendix 4). Yellow bullheads appeared to be less abundant than one of its interspecific competitors, the brown bullhead, of which 120 were observed in our collections. Eighteen of the yellow bullheads collected were YOY from 19 to 61 mm in total length (Appendix 4). All were captured by seine: 11 at Pigeon Lake beach station V (undisturbed Pigeon Lake), 6 at Pigeon Lake 228 beach station T (influenced by Pigeon Elver) and 1 at Pigeon Lake beach station S (influenced by Lake Michigan). Of the remaining 17 fish which ranged from 94 to 421 mm (Appendix 4), 11 were gillnetted at Pigeon Lake openwater station M (influenced by Lake Michigan) and 6 were seined at the three beach stations in Pigeon Lake (S, T and V)- These data indicated that YOY yellow bullheads avoided areas influenced by Lake Michigan, while larger individuals seemed to occupy several types of habitat in Pigeon Lake. The nocturnal activity (including feeding) of yellow bullheads reported by Scott and Grossman (1973) was also observed in this study- With the exception of one individual, all specimens were collected after dark (Appendix 4). Yellow bullheads spawn in May and June in Illinois (Carlander 1969). The male guards the nest and the brood of young until they are approximately 51 mm in length (Scott and Grossman 1973)- Gonad data from our study (Table 53) suggested that spawning of yellow bullhead in Pigeon Lake also occurred in May or early June. Yellow bullheads were caught every month during the sampling period except September (Appendix 4). Relatively large number of adults were collected in October (10 of 18). Young-of-year, with an average size of 36 mm, first appeared in August samples . Catches of YOY declined substantially in October and November as YOY grew to larger sizes (Appendix 4). Reasons for the complete absence of adult and YOY yellow bullheads from our September collections are not known. Water temperatures recorded at time of capture for yellow bullheads varied from 8.0 to 23.0 C. The majority of adults were caught at 8.0 C and no large individual was taken in water warmer than 19*2 C. Most young yellow bullheads were caught at water temperatures around 23 C in August and 8 C in October. Carp — Carp were first introduced to North America as a food resource in 1877 (Johnsen and Heitz 1975) and were first stocked in Michigan waters in 1880 (McCrimmon 1968) . Habitat requirements for this species include shallow marshy areas where feeding and spawning take place, and deeper waters to retreat to during colder months (McCrimmon 1 968) • The carpfs highly tolerant, adaptive and prolific nature has allowed it to successfully occupy and sometimes dominate a wide range of aquatic habitats (McCrimmon 1968). In this study, 15 carp were captured in Pigeon Lake (three in July) while seven were caught in Lake Michigan (four in July) (Appendix 4). All but one carp were caught at night. Carp are generally most active 229 TABLE 53. Monthly gonad conditions of yellow bullheads caught in Pigeon Lake near the J. H. Campbell Plant, eastern Lake Michigan* during 1977 . All fish examined in a month were included except poorly received specimens* Gonad condition Jun Jul Aug Sep Oct Nov Dec Males Slight development Mod. development Well developed Ripe-running Spent Females Slight development Mod . d evelopment Well developed Ripe-running Spent Absorbing 3 2 Immature 13 Unable to distinguish at night and spend days in shallow protected bays (Johnsen and Heitz 1975) • In the present study 13 carp were collected in gill nets set along shorelines in water 6 m deep or less, while nine were captured in seines- Water temperatures at the time of capture ranged from 2.4 to 23.0 C. The entire sample of carp, consisted of ten males, eleven females, and one immature; length range was 32 to 768 mm. Of the 22 carp captured, 14 had ripe gonads and some of these fish occurred in each sampling month from late July to early December. Carp spawning is triggered mainly by water temperatures, and is most prominent between 15 and 26 C in May and June, but extended spawning may occur intermittently through the summer and early fall depending on water temperatures (McCrimmon 1968). Adhesive eggs are laid on aquatic vegetation in shallow water less than 1.2 m deep (Jester 1974) . In- Lake Michigan, carp were only found in nearshore waters. Three carp were seined at beach station Q (s. discharge), two at station P (s. reference) and two were caught in bottom gill nets at nearshore stations A (1.5 m - s.) and B (3 m - s.). In Pigeon Lake eight of the 15 carp collected were caught in gill nets at station M (influenced by Lake Michigan); the size range (516-768 mm) of these carp (Appendix 4) was similar to those caught in Lake Michigan (515-758 mm). Of the remaining carp caught in Pigeon Lake, three (527-591 mm) were gillnetted at 230 openwater station Y (influenced by Pigeon River), two (32 and 203 mm) were seined at station T (influenced by Pigeon River) and two (405 and 407 mm) were seined at station V (undisturbed Pigeon Lake). Carp are generally not popular as either a food or a sport fish. They are accused of disrupting aquatic environments with their feeding behavior, and of crowding out other more desirable species of fish* However, carp are sought by some with hook and line, spear and bow and arrow, and carp meat products are becoming increasingly acceptable (Becker 1976). Black Bullhead— The black bullhead is widespread in the freshwaters of North America (Scott and Crossman 1973)- In Michigan it is commonly found in lakes, warm streams and rivers. This species has limited commercial importance, but has significant value in the sport fishery of Wisconsin (Becker 1976). All of the 17 black bullheads from the present study were captured in Pigeon Lake (Appendix 4). Presence of eleven YOY black bullheads seined between August - November 1977 suggested that Pigeon Lake was utilized as a nursery area. YOY were captured during day and night sampling and ranged in size from 49 mm (1.7 g) to .91 mm (9*6 g). Temperature range at time of capture was 10.9 - 17.8 C. In agreement with findings by Darnell and Meierotto (1965) indicating nocturnal activity of large black bullheads, all large specimens in the present study were also caught at night . Large black bullheads ranged in size from 289 mm (365 g) - 321 mm (590 g) . All adult bullheads were caught in gill nets, except one which was seined; temperature range at time of capture was 15-0 - 21.0 C. Black bullheads were fairly common in past impingement samples, with 43 impinged between January 1974 and March 1975 (Consumers Power Company 1975). Black bullheads are usually not present in areas where brown or yellow bullheads live (Scott and Crossman 1973)- This may help explain their low abundance in Pigeon Lake since 134 brown bullheads were caught there during the present study. Silver Redhorse-- The silver redhorse is distributed throughout the central portion of the Lake Michigan basin (Becker 1976).. It has little recreational or commercial importance except for an undetermined quantity caught and marketed with other species as suckers (Scott and Crossman 1973) • In Iowa spawning takes place in streams in April and May when water temperature reaches 13. 3 C (Becker 1976). 23] This species was apparently uncommon near the Campbell Plant. Of the 11 silver redhorse collected 5 one was an immature individual 57 mm and the others were adults (seven males and three females) ranging in size from 486 to 595 mm* The majority of these fish had moderate or well -developed gonads . All specimens were caught in Lake Michigan (six in July, two in August, three in September and one in November), at water temperatures between 8.2 and 21 . 5 C* Four were seined at night at beach station R (n. discharge) and seven were gillnetted both during the day and at night at reference stations A (1.5 m - s.) and B (3d- s.). The 1977 sampling program started after the reported spawning season of silver redhorse, so we are not able to determine if this species uses the Pigeon Lake-Pigeon River system for a spawning ground. Lake Whitefish — The lake whitefish occurs commonly in the nearshore waters of Lake Michigan (Becker 1976). It is a cold-water species which descends into the cooler water of the hypolimnion during summer months over most of the southern part of its range (Scott and Grossman 1973)- Eleven lake whitefish were captured in the course of this study, all during night sampling* All but one of the fish were caught during June and July in cold water temperatures ranging from 6.0 to 8«2 Co Nine of the fish were trawled at stations 6, 12 and 15 m deep, and two were gillnetted at a depth of 6 m. Fish ranged in size from 261 to 466 mm (Appendix 4). Most lake whitefish are mature at 36O mm (Machniak 1975). Spawning for this species normally takes place in November and December at depths less than 7.6 m (Scott and Crossman 1973) • Lake whitefish spawn randomly (no nest construction) over sand or stone bottoms (Becker 1976) in areas where wave action and water currents keep the spawning site free of silt (Machniak 1975). The fact that no lake whitefish were observed during the fall months of this study may have been due to lack of optimum temperatures during the times of our field sampling. Water temperatures were 10.5 to 12.3 C during October and November, then dropped to 0-1.5 C in December at the stations where lake whitefish had been captured during the summer. Spawning is normally delayed until water temperatures drop to approximately 7-8 C (Lawler 1965). Lake whitefish are exploited commercially and have been a valuable food fish in the Great Lakes. Their numbers have declined in the last 125 years due principally to over-exploitation and degradation of the environment (Wells and McLain 1973). 232 Rainbow Trout — The rainbow trout is native only to the west coast of North America, but has been successfully introduced to many other parts of the world (Scott and Grossman 1973). Rainbows were first planted in Lake Michigan in 1880 (Smiley 1881, cited in MacCrimmon and Gots 1972) where it became established via further plantings and natural spawning in several Michigan streams (McCrimmon and Gots 1972). Spawning was impaired somewhat in the early 1900fs by the construction of hydro-dams on major spawning streams. In the 1940fs and early 1950fs, sea lamprey predation caused a serious decline in rainbow trout populations, since lampreys were selective for the largest members (hence the largest potential spawners) of the population (Borgeson 1974). Chemical control of lamprey, some dam removal and fish ladder construction, as well as increased plantings of rainbows, have replenished the population. Of the ten rainbow trout caught in the present study (300-587 mm), eight were taken from Lake Michigan and two from Pigeon Lake (Appendix 4). All rainbows were collected between late September and November, and eight contained ripe sex products. The gonad of one 58 1 mm male was found in the ripe-running condition in Pigeon Lake in early November. This species mainly spawns between January and March but a less pronounced fall spawning run occurs (Becker 1976) . Rainbow trout spawn in gravel bottom streams with temperatures from 10 to 15.5 C (Scott and Crossman 1973). Temperatures in the lakes when specimens we caught were taken ranged from 10.5 to 12.9 C. Rainbows may spawn three or four times before dying (Becker 1976). All but one of the fish were caught at night . Six fish were caught in gill nets set at 3 and 6 m and four fish were seined « Rainbow trout in Lake Michigan ate mostly alewives leading to average growth of 76 mm/yr over the first 3 yrs (Stauffer 1972). Becker (1976) recorded growth from 1 13 g to 7.3 kg in 5 yrs. Rainbow trout are very popular among sport fishermen, both for their fine flesh and fighting ability. Round Whitefish — Round whitefish are distributed in North America southward from rivers and lakes near the Arctic Ocean to the lakes of the St. Lawrence-Hudson Bay drainage basins and all the Great Lakes except Lake Erie (Armstrong et al. 1977). In Lake Michigan, round whitefish are found in decreasing numbers from north to south as water temperatures become warmer, and are found only occasionally in the more southern portions of the lake (Armstrong et.al. 1977). 233 In this study, eight round whitefish were collected, in July (1) and from September through December (7). All were collected from Lake Michigan in water depths of 3-9 m. These fish, ranging from 141 to 182 mm in length (Appendix 4), were caught by gill nets (6) and trawls (2) in equal numbers during the day and night. Three individuals captured in the latter part of September had well developed gonads . Spawning usually occurs before mid-December when fish have reached age 3 (Mraz 1964). One round whitefish was caught in 1 C water in December, and during other months sampled, specimens were found in water with temperatures of 6.6 to 11.0 C. Round whitefish are highly esteemed as a food fish and are commercially valuable though they are not found in great abundance anywhere over their range. Channel Catfish — The channel catfish is native to streams and lakes of eastern United States and southern Canada and has been widely introduced in the western states . It is an important sport species throughout its range and is exploited commercially in Lake St. Clair, Lake Erie and the Mississippi River (Scott and Crossman 1973)- There is, however, no commercial catch in Lake Michigan (Becker 1976)* This species adapts readily to pond conditions and is now the most commonly raised food fish in warm-water ponds in the United States (Bardach et al. 1972) . Six adult channel catfish (five males and one female) ranging in size from 337 to 663 mm (Appendix 4) were caught in bottom gill nets at 3 to 9 m stations in Lake Michigan, all during the August sampling period. One YOY (58 mm in total length) was seined in November at Pigeon Lake beach station S (influenced by Lake Michigan). All channel catfish were caught at night, confirming the nocturnal feeding activity of this species noted by Finke (1964). Water temperatures at fishing time were between 18.5 and 20.5 C. Although our data seem to indicate that channel catfish preferred the Lake Michigan habitat, movement of this species into Pigeon Lake was established by the occurrence of 161 channel catfish in impingement samples collected between January 1974 and March 1975 (Consumers Power Company 1975). Warmouth — The warmouth is a centrarchid common to many of the lakes and rivers bordering eastern Lake Michigan, particularly those south of the White River (Becker 1976). Lower Michigan appears to be near the northern limit of its range (Larimore 1957). Although this species is of no commercial importance, it is caught in the Lake Michigan drainage basin by sport fishermen along with the other sunfishes. The habitat, available in Pigeon Lake is particularly suited for the warmouth due to abundant growth of aquatic vegetation and a soft, debris-covered bottom 23^ which this species prefers (Hubbs and Lagler 1964)- Five of the six warmouth (four males and one female) in the present study were caught from June-September at beach seining stations S, V and T in Pigeon Lake. One female warmouth was caught in September in a gill net at openwater station Y, Pigeon Lake, Specimens ranged in size from 154 mm (72.4 g) to 192 mm (150.2 g) (Appendix 4). Water temperature at time of capture ranged from 11.5 to 19.0 C. Warmouth appeared to have a small resident population in Pigeon Lake. Small mouth Bass — Smallmouth bass, originally restricted to east-central North America, now occur everywhere in the United States following extensive introductions which began in the mid 1800?s (Scott and Grossman 1 973) - It is a prized sport fish throughout its range and an excellent food fish (Becker 1976). Spawning takes place from late May to early July in nests built on sandy, gravelly or rocky bottoms usually near the protection of rocks or logs (Scott and Grossman 1 973) - Five smallmouth bass ranging in size from 165 to 435 mm were collected in this study (Appendix 4). Of these, three were seined during the day; two at Pigeon Lake beach station T (influenced by Pigeon River), one at Pigeon Lake beach station. V (undisturbed Pigeon Lake). The remaining two were gillnetted during the day at Pigeon Lake openwater station M (influenced by Lake Michigan). Water temperatures at fishing time were between 11.1 and 16.6 C. Two males, one with moderate and the other with little gonad development and one female with slight gonad development were caught in June. The other two, caught in November, were released and therefore not examined. Although our catch in 1977 was relatively low, smallmouth bass appeared to be a common species near the Campbell Plant as a total of 156 individuals were found in weekly impingement samples during the period January 1974 - March 1975 (Consumers Power Company 1975)* Mottled Sculpin — The mottled sculpin is a common inhabitant of Lake Michigan (Becker 1976) where it reportedly occupies the nearshore areas and mouths of shallow tributaries (Deason 1939 ) • Spawning activity of this species is similar to the slimy sculpin (See Slimy Sculpin). Temperature at time of spawning was reported as 10 C in New York (Koster 1936), 8.9-13-9 C in Wisconsin (Ludwig and Norden 1969) and 6-7 C in Maryland (Savage 1963). Of the five mottled sculpins caught, four were trawled in June in Lake Michigan. Water temperature ranged from 4.5 to 6.1 C. The occurrence of this species at stations F (18 m) and G (21 m) indicates that this species may be less of a near shore inhabitant than suggested 235 by Deason (1939)- One additional mottled sculpin was seined in November at Pigeon Lake beach station S at a water temperature of 11.0 C. The two largest specimens (80 and 94 m) were both males with little gonad development* The remaining three (38, 40 and 55 mm) were all immature (Appendix 4) . Due to the difficulties in distinguishing this species from the slimy sculpin (See METHODS-LABORATORY ANALYSIS OF JUVENILE AND ADULT FISH) the mottled sculpin in the vicinity of the Campbell Plant may be more abundant than indicated by our data. Mottled sculpins may serve as forage for some of the game species in the area, but the degree of importance is unknown. Chinook Salmon — The chinook salmon was the first Pacific salmon to undergo widespread introduction outside of its native range (Scott and Grossman 1973). This species was first stocked in Lake Michigan in 1967 and by the end of 1970, 4.1 million fingerlings had been released (Wells and McLain 1973) • Chinook salmon usually spawn at age III or IV and die after spawning (Mercer Patriarche, personal communication, Institute for Fisheries Research, Michigan Department of Natural Resources, Ann Arbor, Michigan) . Preliminary results of a study of chinook salmon indicate that some natural reproduction takes place in Michigan's trout mainstreams (L. Carl, personal communication, Institute for Fisheries Research, Michigan Department of Natural Resources, Ann Arbor, Michigan). Chinook reach a large size (10-20 kg) in the lake and their voracious feeding helps contain the prolific alewife population (Becker 1976). In the present study, three -adult and one immature chinook salmon were collected from Lake Michigan (Appendix 4). The immature fish, which measured 92 mm, was taken in a night seine haul performed in early June in 8.0 C water at beach station Q (s. discharge). The three adults were all captured in night surface gill nets set at 6 m stations C and L. One was an 8 18 mm male collected in September in 6«1 C water and the other two were a male and female (378 and 571 mm respectively) caught in November in 12.3 C water. The two largest fish had well developed gonads. Spawning time for chinook salmon varies according to how far upstream they migrate, but generally occurs in the fall (Becker 1976), Although no chinook salmon were collected during regular monthly sampling in Pigeon Lake, a large adult was taken during electrofishing on 5 October 1977 opposite Station T (influenced by Pigeon River) . Apparently some chinook enter the Pigeon River area to spawn in the fall. Many chinook salmon were also observed in the discharge canal during autumn 1978. 236 Longnose Dace — The longnose dace is widely distributed in north-central North America (Hubbs and Lagler 1 964) . It is often associated with gravel and boulder bottoms of fast flowing streams and inshore waters of large lakes (Scott and Crossman 1973)- Jude et al. (1975) found the occurrence of longnose dace relatively constant for all months, in southeastern Lake Michigan near the Cook Plant- Longnose dace accounted for 0.02? (41 fish) of the total number of fish captured in their standard series fishing in 1973* Anderson and Brazo (1978) studied the distribution and feeding habits of longnose dace in the beach zone of Lake Michigan near Ludington. In the present study four longnose dace (38-59 mm) were collected, all by seine (Appendix 4). Two dace came from Lake Michigan beach station P (s. reference) in October and November, one came from beach station R (n. discharge) in November and one came from Pigeon Lake beach station S (influenced by Lake Michigan) in September. The largest individual (59 mm caught at station P in October) was a male in an early stage of gonad development. All other specimens were immature. Longnose dace were caught in water temperatures of 11.2-17-0 C. Although Simon (1946) remarked that this species is of great value as a forage fish in Wyoming, its low abundance indicates little possibility of this in. the area around the Campbell Plant. Emerald Shiner — The emerald shiner is a planktivorous open-water minnow (Flittner 1964) which, until the early 1960fs was very abundant in Lake Michigan (Wells and McLain 1973) • The sharp decline and near demise of emerald shiners in Lake Michigan noted by shoreline residents and bait dealers during this period was apparently linked to an increase in alewife abundance (Smith 1970). Emerald shiners were still "highly conspicuous ,f in the harbor at Grand Haven, Michigan in 1970 (Wells and McLain 1973), but our visual observations at Grand Haven during 1977 showed that only gizzard shad were present in large concentrations. Emerald shiners were notably absent from the inshore waters of Lake Michigan in the vicinity of the Campbell Plant, with only one specimen caught during our August seining activities at beach station R (n. discharge). This finding corresponded well with a similar low occurrence of emerald shiners around the Cook Plant in southeastern Lake Michigan (Jude et al. 1975 and Jude et al. 1979)- Three emerald shiners were caught in Pigeon Lake, indicating the possiblity of a small resident population there. These fish were seined at beach stations S and T during July to September. This species probably has little value as a forage species in the area. Emerald shiners were caught at temperatures from 17 to 24 C and ranged in size from 63 to 81 mm (Appendix 4) . 237 Banded Killifish— The banded killifish is common and widely distributed throughout the eastern shore of Lake Michigan and its tributaries (Becker 1976). It prefers quiet waters, and is usually found in small schools over sand, gravel or detritus-covered bottoms having patches of submerged vegetation (Scott and Grossman 1973)- Only two banded killifish were captured in the present study. These specimens were caught by seine at Pigeon Lake beach station V (undisturbed Pigeon Lake) in November when water temperature was 12.6 C. The first was a female, 43 mm long while the second was a 40 mm male (Appendix 4). Although this species may serve as important food for game fish in areas where killifish are abundant (Scott and Grossman 1973), they are probably an unimportant forage species in Pigeon Lake because of their scarcity. Goldfish— The goldfish is an East Asian species widely introduced into all parts of the United States (Scott and Grossman 1973)- Goldfish occur sporadically throughout the Great Lakes basin (Hubbs and Lagler 1964). This species prefers small, warm lakes and streams, but can survive in relatively cold water. Two YOY measuring 22 and 24 mm (Appendix 4) were caught in seines during August at Pigeon Lake beach station S (influenced by Lake Michigan) at a water temperature of 22 «8 C« Apparently some reproduction of goldfish occurred in Pigeon Lake. A few adult goldfish were also sighted while electrofishing in the area. Goldfish appeared to be an uncommon species in the Campbell Plant vicinity. Burbot — The burbot is a common species in Lake Michigan (Becker 1976) . Only two burbot were caught during the present study . One male (401 mm, 550 g) with well developed gonads was caught in a gill net at Pigeon Lake openwater station M (influenced by Lake Michigan) in early December 1977 (Appendix 4). Water temperature at time of capture was 2.5 C. In Lake Michigan, a female burbot (358 mm, 382c 3 g) with well developed gonads was also captured during December at station D (9 ni - s.) in a gill net. Water temperature at time of capture was 1.0 Co Occurrence of these burbot with well developed gonads along with the entrainment of a single burbot larvae in February 1978, suggested the possibility that Pigeon Lake or this vicinity of Lake Michigan may serve as a spawning area for burbot. Jude et al. (1975) also documented the inshore area in the vicinity of the Cook Plant, southeastern Lake Michigan as a spawning and nursery area for burbot. Movement of burbot into river mouths for spawning has been reported in Lake Simco, Ontario (McCrimmon and Devitt 1954). More winter collections would be necessary to establish whether Pigeon Lake is used extensively by burbot as a spawning area. 238 This species comes into inshore waters during the colder parts of the year and is not generally abundant in the area around the Campbell Plant. However one was impinged during June 1974 (Consumers Power Company 1975). Shorthead Redhorse — One male shorthead redhorse, (438 mm, 900 g), was caught in the area of the Campbell Plant (Appendix 4). This specimen was gillnetted at station A (1.5 m - s.) in Lake Michigan in August, at a water temperature of 12.5 C. Shorthead redhorse inhabit shallow, clear waters of lakes and rivers and are intolerant of heavy silt (Scott and Grossman 1973). They are uncommon to common in widely disjunct locales in the Lake Michigan basin (Becker 1976). Apparently shorthead redhorse were uncommon in the area around the Campbell Plant during 1977. Lake Sturgeon — The lake sturgeon has exhibited the most abrupt decline of any species in Lake Michigan (Wells and McLain 1973). A single lake sturgeon was seined in the study area at Lake Michigan station Q (s. discharge) at a water temperature of 20 C, confirming its scarcity in the area as reported by Becker (1976). The specimen collected was 584 mm (Appendix 4) and was returned to the water unharmed. Age-at-length estimates given by Scott and Crossman (1973) suggest that this sturgeon was approximately 9 yrs old. The lake sturgeon is currently listed as a threatened fish species (U.S. Dept„ Interior 1973) « Golden Redhorse — The golden redhorse is reportedly common to the lower two-thirds of lower Michigan (Becker 1976). This species is apparently better adapted to rivers, where they inhabit slower moving reaches, probably avoiding heavily weeded areas (Trautman 1957). The only golden redhorse caught in the present study was a male (465 mm, 120 g) gillnetted in October at station M (6 m) in Pigeon Lake (Appendix 4). Water temperature was 9.7 C. This species was scarce in the Pigeon Lake area of the Campbell Plant, possibly due to the dense vegetation. Bigmouth Shiner — Only one bigmouth shiner (63 aim) was collected in the present study (Appendix 4). This specimen (sex undetermined due to poor condition of fish) was seined at station V (undisturbed Pigeon Lake) during June at a water temperature of 13.5 C. This species is common in small to medium-sized streams, preferring sandy bottoms frequently interspersed with gravel (Becker 1976). Bigmouth shiners probably have limited value as a forage species in Pigeon Lake due to its sparsity. 239 Cisco — Cisco or lake herring was an important commercial species in Lake Michigan during the period 1890« 1 908 • The initial decline of catch after 1 908 resulted mainly from heavy exploitation by commercial fishermen (Wells and McLain 1973)- Population explosions of introduced rainbow smelt in the 1930fs and of smelt and alewives in the 1950?s, were believed to cause the drastic reduction in lake herring populations in Lake Michigan (Wells and McLain 1973, Smith 1970)- Cisco were rarely found at temperatures above 16.7-17.8 C or at dissolved oxygen concentrations below 3-4 ppm at the deeper limit of their distribution (Becker 1976). Spawning takes place in the fall, usually in shallow water over gravel or stone but may occur in water as deep as 9-12 m (Scott and Grossman 1 973) - The only cisco collected in this study was caught in a gill net at Pigeon Lake openwater station M (influenced by Lake Michigan) in June when the water temperature was 11.2 C. Age-length data of cisco from the Great Lakes region (Carlander 1969) suggested that the 389 mm (425 g) female we caught was approximately 8 or more yrs old* This species is apparently rare in the inshore waters of southeastern Lake Michigan. Jude et al* (1975) caught only one adult specimen in 1973 in the vicinity of the Cook Plant, southeastern Lake Michigan . Blacknose Shiner— Blacknose shiners vary in abundance from common to uncommon throughout the Lake Michigan basin (Becker 1976). In the present study one specimen (63 mm) was captured during June by seining at Pigeon Lake beach station V (undisturbed Pigeon Lake) (Appendix 4). Water temperature at time of capture was 13.5 C. The clear, weedy habitat of Pigeon Lake, preferred by blacknose shiners (Scott and Grossman 1973) should provide a suitable environment for this species. Ten blacknose shiners were impinged at the Campbell Plant between January-May 1974 (Consumers Power Company 1975). Since no early spring sampling was done during the 1977 field season, 1978 field sampling during this time may show this species to be more abundant than indicated by 1977 data. Pirate Perch — Pirate perch is the only living species of the family Aphredoderidae; the remaining members of the family are known only from fossil records (Hubbs and Lagler 1964) « Pirate perch are found in Michigan as far north as the Pere Marquette River system in Mason County (Becker 1976). The reported preferred habitat of soft muck bottoms covered with organic debris (Becker 1976) described Pigeon Lake beach station T (influenced by Pigeon River) where the only specimen recorded 240 from our study was seined. This 72 mm male was caught during October when water temperature was 8.0 C. One pirate perch was also observed while electroshocking near station T. Ecological importance of this species is not known. This species is not abundant in the Great Lakes region, where it is near the northernmost limit of its range (Hubbs and Lagler 1964). Quillback — Localized populations of quillbacks exist in Lake Michigan; the concentration nearest the Campbell Plant is reported to be in the Grand River, Michigan (Becker 1976). One male quillback (465 mm, 1325 g) was caught at 6 m station M (Pigeon Lake) by gill net during December at a water temperature of 3.2 C. Quillbacks live in habitats as varied as clear lakes and turbid rivers (Scott and Crossman 1973). Although only one quillback was captured, preliminary examination of 1978 impingement data suggested the possibility of a local population in Pigeon Lake- also, initial 1978 observations in the discharge canal indicated that some quillback also utilized this habitat. Creek Chub — The creek chub was observed during April 1978 in Pigeon Lake, but none were caught during 1977 sampling. Creek, chubs are widely distributed in the Lake Michigan basin, but are more common in streams than rivers (Becker 1976). Fathead Minnow — Although no fathead minnows were captured during 1977 sampling, this species was observed during supplementary sampling near Pigeon' Lake beach station S (influenced by Lake Michigan) , when approximately five were collected in one seine haul during April 1978- Fathead minnows are reported to be common in the Lake Michigan watershed (Becker 1976). Northern Hog Sucker — One northern hog sucker was observed in April 1978 in a non-sampled lot of impinged fish. No northern hog suckers were caught during our 1977 sampling efforts. This species was apparently uncommon in the are* of the Campbell plant. Northern hog suckers prefer clear parts of streams and rivers, especially in riffle areas where the bottom is gravelly (Becker 1976). Logperch — Logperch have been observed in impingement samples in 1977 (Zeitoun et al. 1978) and 1978 on two occasions. Although they have not been 241 collected during our lake sampling, there are some indications that this species remains just offshore in 1-1.3 m of water outside the seining zone (Scott and Grossman 1973)- These authors noted that this offshore distribution often leads to the species being mistakenly called uncommon in an area. Logperch prefer those regions of lakes, streams or rivers with sand and gravel bottoms (Becker 1976). White Crappie — White crappie have been observed by Consumers Power Company personnel in impingement samples (Consumers Power Company 1975, Zeitoun et al. 1978), although no white crappie were caught during our 1977 sampling* A widely disjunct population of this species is distributed through the southern half of the Lake Michigan Basin (Becker 1976). Walleye— One walleye was observed during electrofishing operations in Pigeon Lake during 1977. Populations of walleye are scattered throughout the Lake Michigan basin where its status is uncommon to common (Becker 1976). It is apparently uncommon in the area of the Campbell Plant. Gar— Gars have been observed at various times throughout the 1977 sampling period- Most sightings have been at distances too great to allow positive species identification . One longnose gar was observed maintaining a fixed position in the discharge canal in October 1977- An additional sighting of a gar, which may have been a spotted gar, was made while pulling a gill net in Pigeon Lake in September. Data for 1977 suggest that gars are uncommon in the area of the Campbell Plant. Chestnut Lamprey — One chestnut lamprey was observed during initial spring impingement sampling 1978. This species is parasitic on fishes and is generally found in large rivers (Becker 1976). Becker reported that there are numerous records of chestnut lamprey from lower Michigan. Since most nets are ineffective for sampling lamprey, its status in the area of the Campbell Plant is unknown. Sea Lamprey — This species of lamprey was also observed in impingement sampling in 1977 (Zeitoun et al. 1978) and in the spring of 1978* It has been observed in the Pigeon River prior to our sighting, but this area is considered marginal for sea lamprey production (personal communication, Bob Mormon, U.S. Fish and Wildlife Service, Ludington, Michigan). The Pigeon River was treated only once for sea lamprey in October 1964. 2U2 Tiger Muskellunge — The tiger muskellunge is the result of hybridization of the northern pike with the muskellunge. One specimen was observed in September 1977 near Pigeon Lake openwater station Y (influenced by- Pigeon River) during electrofishing. Freshwater Drum — The freshwater drum is occasionally found in the lower portions of tributaries to Lake Michigan (Becker 1978). Although absent from standard sampling in 1977, drum were observed in the area of the Campbell Plant in 1978. One drum was caught in a bottom gill net at station L (6m - n.) in September 1978. An additional drum was caught by hook and line in August 1978 near station X (undisturbed Pigeon Lake). Mark and Recapture Largemouth bass (>. 220 mm) and northern pike were recaptured in large enough numbers to allow reliable estimates of population size in Pigeon Lake to be made . Northern pike were divided into two groups according to size, the smaller group being 177-300 mm, the larger being greater than 300 mm. Small largemouth bass (<220 mm), smallmouth bass and grass pickerel were marked, but insufficient recaptures prevented making a reliable population estimate. An estimate of the population of northern pike (_>300 mm) in Pigeon Lake was made based on four recapture periods during late September-December using the Schumacher/Eschmeyer Method (Ricker 1975). This method requires that the population remain constant throughout the sampling period. Fishing mortality by anglers was low and probably nonexistent. Few anglers were observed on the lake during this period and no fish were caught by anglers during our observations. Natural mortality for fish of this size is usually low so this factor was discounted. Our monthly sampling, responsible for 13 northern pike deaths, probably caused more mortality than that due to angling or natural causes, however, it is believed that fish killed during this period will not invalidate the population estimate. During the mark and recapture experiments, 157 large northern pike t>300mm) were marked with individually numbered spaghetti tags. Total recaptures numbered 24 and only two fish were recaptured twice. Number of fish marked over the four periods varied from 18 in the December period to 49 in the November period (Table 54)* Using the Schumacher/Eschmeyer equation, the estimated population within Pigeon Lake was 672 northern pike (95? confidence limits: 610, 749). This was felt to be a large population for a lake of this size. 243 Northern pike apparently moved around within Pigeon Lake rather than staying within a smaller home territory. Of the large northern pike recaptured, 63$ were caught in a different area from that into which they were released, which provided good evidence that thorough mixing of marked individuals with the rest of the pike population had occurred . The estimate for small northern pike (177-299 mm) was also based on four recapture periods. Again, fishing mortality can probably be discounted because of low fishing pressure and sublegal size. Natural mortality might have been higher than for larger pike, but was still probably insignificant. The smallest fish marked during the study was 177 mm and a fish this size should be beyond the point where high mortality would be significant . During the mark and recapture period 97 small pike were marked with fin clips. Of these fish, six were recaptured (Table 55). Using the Schumacher VEschmeyer equation, the estimate for the number of small northern pike in Pigeon Lake was 628 with a 95$ confidence interval of 589-670* The population estimate for largemouth bass (>.220 mm) also involved four recapture periods and no angling mortality was observed. Natural mortality was felt to be negligible. No largemouth bass of this size were caught in our sampling gear during the mark and recapture efforts, a good example of gear bias. Spaghetti tags were affixed to 147 largemouth bass during the study. Fourteen largemouth bass were recaptured, none of them twice . Results for each sampling period are presented in Table 56 . The Schumacher /Eschraeyer equation yielded an estimate of 471 fish with 95$ confidence limits of 349-724. There appears to be a large population of largemouth bass in Pigeon Lake. Largemouth bass also appeared to move about within Pigeon Lake. Of the largemouth bass recaptured, 65$ were caught in a different area than where they were released. Largemouth bass under 220 mm total length were marked with a different fin clip during each period. Thirty-one were marked, but none were recaptured. Many more small largemouth bass were seen and not captured. The population of largemouth bass in this size range was very large, based on observations during electrofishing and from seine hauls. Marking sufficient numbers of fish to ensure recaptures would have taken too much time away from effort expended in capturing larger northern pike and bass. Therefore less time was spent dealing with small largemouth bass; consquently no estimate was made. Seven smallmouth bass were marked during the period 21 September to 2 November 1977* Nearly all fish (265-459mm) were caught in November. No smallmouth bass were recaptured. The population of smallmouth bass appeared to be low based on our observations . During this experiment 42 2hh TABLE 54. Population estimate data for northern pike (^.300 mm) in Pigeon Lake near the J.H. Campbell Plant, fall, 1977. M^ = total number of marked fish at the start of the period. Ct = total number of fish captured during the period and Rt = number of fish recaptured during the period. PERIOD (t) DATE Mt Ct Rt I 9/21 - 9/28 0 II 10/5 - 10/6 47 III 10/18 - 10/20 89 IV 11/2 - 11/3 123 V 12/7 157 47 0 47 5 47 7 49 8 18 4 TABLE 55 # Population estimate data for northern pike (<300 mm) in Pigeon Lake near the J.H. Campbell Plant, fall, 1977. Mt » total number of marked fish at the start of the period, Ct » total number of fish captured during the period and Rt m number of fish recaptured during the period. PERIOD (t) DATE Mt Ct Rt I 9/21 - 9/28 0 15 0 II 10/5 - 10/6 15 29 0 III 10/18 - 10/20 44 35 3 IV 11/2 - 11/3 67 30 3 2U5 TABLE 56. Population estimate data for largemouth bass (£.220 mm TL) in Pigeon Lake near the J.H. Campbell Plant, fall, 1977. Mt = total number of marked fish at the start of the period, Ct » total number of fish captured during the period and Rt - number of fish recaptured during the period, PERIOD (t) DATE Mt ct Rt I 9/21 - 9/28 0 24 0 II 10/5 - 10/6 24 48 i III 10/18 - 10/20 71 36 2 IV 11/2 - 11/3 105 42 12 grass pickerel (105-282 mm) were marked. Grass pickerel were caught and marked throughout the study, but only one fish was recaptured. Grass pickerel seemed to be fairly abundant in Pigeon Lake based on our electroshocking results. The number of fish species observed while electroshocking in Pigeon Lake generally paralleled results from seining and gillnetting in Pigeon Lake. There were two species caught while electroshocking that were not captured with any other gear during sampling. A walleye (522 mm total length; 1700 g) was caught off the intake canal on 5 October 1977. A tiger muskellunge (263 mm total length; 75 g) was caught on 29 September near the upstream side of the bridge near Pigeon River. Both fish were marked and released. lk6 FISH LARVAE AND ENTRAINMENT STUDY Fish larvae are undoubtedly the most important life history stage of all fishes. Since the strength of year classes in adult fishes is ultimately controlled by the egg and larval stages, it becomes extremely important to understand the factors which affect the growth and survival of larval fish. As of 1975, there were 45 power-generating plants on Lake Michigan which draw water from the lake for cooling purposes (Lake Michigan Federation 1975). It is common knowledge that most fish species use the inshore zone of the Great Lakes as a spawning ground and nursery area. Consequently, every power plant, domestic or industrial intake on the lake has the potential for entraining large numbers of fish larvae and eggs. Many larvae suffer severe stress and mortality. The primary purpose of this part of the study was to gather enough data to determine what impacts were being made on fish larvae populations by the J. H. Campbell Power Plant's present and proposed cooling water system. The secondary objectives of this section included: 1) describe what species were present and in what abundances, as well as their spatial (vertical and horizontal) and temporal (seasonal and diel) distribution 2) determine which species utilized the Port Sheldon area as spawning and/or nursery grounds 3) gather information to correlate the appearance of fish larvae in field samples with occurrence in entrainment samples 4) completion of information about life cycles including spawning times and locations Fish larvae were defined as any fish less than 25.4 mm in total length for simplicity in data manipulation. Periodically, fish greater than 25.4 mm were caught in net and sled tow samples. These fish were called fry for our purposes and analyzed separately from larvae. Larval fish data in this section were discussed by taxonomic group. Within a given species or group, seasonal distribution by month was discussed. A standard unit of concentration, no./ 1000 m , was used to compare densities at the various stations and times. Actual densities obtained were biased because of differences in efficiencies of the net in the diverse habitats sampled, with more and longer larvae captured at the more densely vegetated and turbid Pigeon Lake stations . More larvae were usually collected at night because of daytime net avoidance. These differences were taken into consideration when data were discussed. Another data compilation which we used to display differences in length of larvae collected from the various habitats was the length-frequency histogram. Many times we were able to separate from which lake entrained larvae were derived by examination of these histograms. These 2k'J data were also useful for determining growth relationships of the larvae in the two ecosystems. Stations were established in Lake Michigan along two transects, which were identical to those used for adult fish (Fig, 1). One transect was in the area of the present onshore discharge (north transect) and one, the reference transect, was south of the plant* Sampling locations in the openwater of Pigeon Lake were also established (Fig. 2). Pre- and post-operational data comparisons were and will be made on the basis of these data. Beach stations were established in a similar manner for the above discussed comparisons as well as to determine the distribution and abundance of larval species at inshore stations. Sampling was also conducted in the intake canal to determine what fish larvae were present just prior to entry of water into Campbell's cooling-water system. Entrainment sampling, using the same 0.5 m diameter nets used in field collections, completed sampling the circuit that larvae were expected to travel. Two types of gear were used to sample larval fish; regular plankton nets and a benthic sled-towing device (Fig. 5)- These gear were able to sample the entire inshore aquatic habitat from surface waters to just off the bottom and from the beach zone out to 21 m (as far as we chose to go). These gear, which covered most areas of the physical habitat, combined with day and night sampling and more frequent collections during months of peak larval abundance, should provide a well-balanced understanding of the densities and distribution of fish larvae in the area of the Campbell Plant. A discussion of each taxonomic group (see Table 57 for a species list and our larval codes) follows. Ale wife The most abundant species of larval fish in the area of the Campbell Plant was the alewife. Spawning of this species occurred in June-early August in southeastern Lake Michigan during 1973 (Jude et al. 1975) and in late June 1963 near Saugatuck (Allegan Co. Michigan - Edsall 1964). Studies on Lake Ontario suggested that actual time of spawning was temperature dependent (Pritchard 1929) . Eggs are reportedly broadcast at random, demersal and essentially nonadhesive (Scott and Grossman 1973). Female alewives from Lake Michigan produced from 11,000 (from 160 mm fish) to 22,000 (192 mm fish) eggs (Norden 1967). Examination of Pigeon Lake larval collections showed alewife larvae first appeared in early June suggesting that alewife spawning in this small inland lake occurred sometime in May. All locations of alewife spawning sites in Pigeon Lake are not known. However, on several occasions at night during late June and July, alewife were thought to have been observed spawning off beach station V (undisturbed Pigeon 2U8 TABLE 57. Scientific name, common name and abbreviations for all species of larvae captured from Campbell Plant study areas from June through December 1977. An L denotes presence of larvae in either Lake Michigan or Pigeon Lake, and an F represents fry. Names assigned according to Bailey et al. 1970. Scientific and Common Name Pigeon Lake Abbreviation Lake Michigan Entrainment Atherinidae Labidesthes siaaulus (Cope) Brook silverside SV L,F Centrarchidae Ambloplites rupestris (Rafinesque) Rock bass Lepomis eyanellus (Rafinesque) Green sunfish Lepomis gibbosus (Linnaeus) Pumpkinseed Lepomis maorochirus Rafinesque Bluegill Lepomis spp. Unidentified Lepomis Miaropterus dolomieui Lacep&de Smallmouth bass Miaropterus salmoides (Lacepede) Largemouth bass Pomoxis nigromaaulatus (Lesueur) Black crappie Pomoxis spp. Unidentified Pomoxis Centrarchidae spp. Unidentified centrarchid RB L,F GN L PS L F BG F F XL L,F L SB L LB L,F L BC L,F PM L L CT L Clupeidae Alosa pseudoharengus (Wilson) Alewif e Dorosoma aepedianum (Lesueur) Gizzard shad AL GS L5F L,F L,F F Cottidae Cottus cognatus Richardson SS Slimy sculp in Myoxooephalus quadricomis (Linnaeus) FS Fourhorn sculpin L L ikg TABLE 57. (continued), Pigeon Lake Scientific and Common Name Abbreviation Lake Michigan Entrainment Cyprinidae Cyprinus oarpio Linnaeus Carp Notemigonus crysoleucas (Mitchill) Golden shiner Notropis atherinoides Rafinesque Emerald shiner Notropis hudsonius (Clinton) SP L,F L,F L,F Spottail shiner Pimephales notatus (Rafinesque) Bluntnose minnow Cyprinidae spp. XM - L,F L9F Unidentified cyprinid Gasterosteidae Pungitius pungitius (Linnaeus) Ninespine stickleback Gasterosteidae spp. Unidentified stickleback Ictaluridae Iotalurus nebulosus (Lesueur) Brown bullhead Iotalurus spp. Unidentified bullhead Noturus gyrinus (Mitchill) Tadpole madtom Osmeridae Osmerus mordax (Mitchill) SM L,F L5F L,F Rainbow smelt CP L,F GL L,F ES F SP L,F BM L,F XM- L,F NS L XG L BN F XB L,F MT F Percidae Etheostoma nigrum Rafinesque JD L,F Johnny darter Etheostoma spp.. XE L Unidentified Etheostoma Perca flavescens (Mitchill) YP LSF Yellow perch Percopsidae Peroopsis omiscomayous (Walbaum) TP Trout-perch L L 250 TABLE 57 « (continued) Pigeon Lake Scientific and Common Name Abbreviation Lake Michigan Entrainment Larvae damaged beyond recognition XP L L L,F Unidentified Pisces - XX L L L Lake) and around openwater station M (influenced by Lake Michigan) in Pigeon Lake. There was periodic splashing heard in. a large area around the boat which we identified as spawning alewives. From our other Lake Michigan work experience and because we observed large quantities of larval alewives in the water at night with flashlights offshore from beach station V, we are confident that large numbers of alewives were spawning in Pigeon Lake. Spawning in the Escanaba area of Lake Michigan (Delta Co. Michigan) occurred in 0.6-0.9 m of water over mud, sand and organic, debris-covered bottom (Joeris and Karvelis 1962). If selection of similar habitat occurred in Pigeon Lake, this would explain the increased numbers of alewife larvae observed at beach stations S and T when compared with openwater stations (Fig. 73)* A length-frequency histogram of all alewife larvae caught during June in Pigeon Lake (Fig. 74 ) shows that most larvae ranged between 4-11 mm (average = 7.2, S.E. = 0.3). Norden (1967) reported that newly hatched larvae averaged 3.8 mm. If the growth rate of 0.5 mm per day reported by Lam and Roff (1976), or 0.56 mm per day reported by Heinrich (1977) was experienced by alewife larvae in Pigeon Lake, most larvae captured there in early June hatched within 10 days prior to capture. A length-frequency histogram for alewife larvae captured in the intake canal (station Z) during June (Fig. 74 ) showed all larvae there were between 3.5-5.0 mm (undoubtedly newly-hatched). These smaller larvae were probably entrained at higher rates than longer larvae which were present in Pigeon Lake, because newly-hatched larvae appeared to have a species-specific length below which they are apparently semi-planktonic and thus susceptible to intake currents, Once they are larger than that length, larvae appear to exert more control over their movements and therefore their distribution. Behavioral movements in response to food, light, currents and other factors then determine their future vulnerability to being entrained. Our data indicate that Pigeon Lake serves as an important area for early spawning of alewife. No alewife larvae were present in Lake Michigan samples collected in early June with the exception of 73 larvae/ 1000 m3 observed at beach station R (n. discharge) (Fig. 75). The larva observed was 4.5 mm and 251 M 0.5 - £ 3T 0.5 - ■in ' Q 0.5 - -f f 500 1000 1500 aooo 2500 NO. LARVAE/ 1000 m 0.5 - ZZ3 0.5 -1 i £ V-X X h- j i ■ i CL UJ O 0.5 - 2.5 - 4.5 - i n ; i 200 400 600 NO. LARVAE/ 1000 m w 0.5 & 2L.5 -i Q 100 200 300 400 NO. LARVAE/ 1000 m 80C 500 fig. 73. Number of alewife larvae per 1000 m3 for beach, openwater and intake canal stations in Pigeon Lake near the J. H. Campbell Plant, eastern Lake Michigan, 31 May - 3 June 1977. D = Day ■ = Night 252 JUNE Digeon Lake Stations MXY ST V "X= 7.2(0.3) N = '24 V- 10 15 20 25 47. 62 «> Intake Canal 7= 4.4(0.!) N= 21 " "T 1 1 ' "1 ' 5 10 15 20 25 30 - LaKe Michigan 20- Pooied X=6.3 (0.4) N = i7 10- I JULY 30- intake Canal 20- X= 8.6(0.1) 10- N=I092 ililfllL 10 15 20 25 10 15 20 25 JO-i Entrained 20- X= 7.7(0.1) N=2786 10- 1 I. .J llllllihhlllll.i.l.l,. ... ... JULY Pigeon Lake station M X = 8.7 (O.l) N* 1170 jak. Pigeon Lake Beach Stations STV X«I9.0 (0.3) N*247 .,. ,1-jJj Pigeon L~*e Openwater Stations MXY X = 9.5 (0.1) N= 1242 aMk^ 30 Digeon Lake Stations MXYSTV X = ll.l (0.2) ■ N*!489 20 a: *o uJ Q. J jUllllllhil,, , j ..i-j. Jd.i., 5 10 15 20 25 Sled Tows Inshore Lake Michigan Stations PQRA8IJ X*I5.2 (0.2) . 10-1 H'Z9i I jUuililL. Jlllliki.,,. , Li W 15 20 25, „ 30 t Sled Tows Offshore Lake Michigan Stations C-H . L N 0 20- X=7.2 (0.4) N'lOO 5 10 15 20 25 nsnore i-cke Michigan Stations PGPASi J X=9.8 tG.2) N- 1944 lllij.ul i.i.lilliiimi 1— II 30- Offshore Lake Michigan Stations C-H.LNO 2 X = 5.6 (0.0) N=5857 llllt«lliii>ililm«i) )■' i i 10 15 20 25 inshore Lake Michigan South Transect Stations PA8 X* 6.2 (O.l) N= I033 llli.nlij.tiin ,i i.| iHii 40- 5 10 15 20 25 30- Inshore Lake Michigan * 20- North Transect Stations 0 I J X = il.3 (0.3) 10- N = 584* III llllli.i . , . . , ■...,.. Ji lllllll L_._4 10 15 20 25 JO- u:Ke Mich.g :n 20- Poi..iei 7=6 ?'C .) I N± 730I 10- . jl |!l... -i^ 5 10 15 20 25 5 10 15 20 25 AUGUST 10 15 20 °igeon Lake Openwater Stations MXY X*I0.5 (0.6 N*I23 Pigeon Lake Beach Staticns STV X*2 2.3 (0.4) N=78 30-i Pigeon Lake stations MXYSTV Entrapment X = I8 : , J \ N=2C34 .,iiiilliiii>.niimumliinili»lHllH 10 15 20 25 10 15 20 25 SFPTFMBER Lake Michigan Pooled X -= 2 1 . t 02) 1 \ Sled Tow-, J Lake Micnigjn 1 Pooied -ML '°1 1 X--i92 H- ?3 ililllL ILL 10 15 20 25 10 15 20 25 10 15 20 TOTAL LENGTH (mm) FIG. 74. Length-frequency histogram for larval alewife caught at selected pooled stations in Lake Michigan and Pigeon Lake near the J.H. Campbell Plant, 1977. All tows were net tows unless sled tows were specified. (X^riean, N-total number of larvae used in the comparison, standard error is given in parenthesis.) 253 Y M IT - - 23 June 0,5 - i i j. X Q 0.5- « i " "'» r ' i 2o5 - 4.5 - 40 80 120 160 200 NO. LARVAE/ 1000 rrf R 31 May - 3 June - " ■ ■ .i 0o5 - 6 X 0.5 - 0. Ui 0.5 - 20 40 60 80 NO. LARVAE/ 1000 nrT FIG0 75* Number of alewife larvae per 1 000 m for openwater Pigeon Lake stations (1 7-23 June) and Lake Michigan beach stations (31 May-3 June) hear the J. H» Campbell Plant, eastern Lake Michigan, i977„ D = day ■ = n ight 25^ suggests that alewife spawning occurred in the area of the discharge canal near the same time as spawning occurred in Pigeon Lake. Concentrations of up to 429 alewife larvae/1000 m were noted in the intake canal (station Z) at night in early June, but unfortunately no entrainment samples were taken, which may have clarified the origin of larvae collected at beach station R. Preliminary observations of high densities of eggs in samples taken in the discharge canal in June 1978, coincident with observations of high numbers of adult alewives which appeared to be spawning, suggests the discharge canal as the source of station R alewife larvae. Based on data summarized by Marcy (1975) indicating that the vast majority of power plants inflicted near 100? mortality on entrained larvae (particularly those with long discharge canals), it was unlikely that larvae observed at beach station R (n. discharge) originated in Pigeon Lake and passed through the plant. In late June no alewife larvae were collected at beach stations in Pigeon Lake, and decreased numbers were found at openwater stations M and X when compared with early June densities (Fig. 75). Numbers of alewife larvae at openwater station Y (influenced by Pigeon River) in late June were comparable to concentrations observed in early June (Figs. 73 and 75)* No alewife larvae were collected from the intake canal (station Z) in late June. In general, decreased densities of alewife larvae in Pigeon Lake were probably the result of a tapering off of a spawning peak in Pigeon Lake. This spawning peak undoubtedly was responsible for the high densities of alewife larvae observed in Pigeon Lake in early June. Natural larval mortality, predation, movement from the area, as well as entrainment may also account for the observed reduced alewife densities in late June. Lake Michigan south transect samples in late June showed a sporadic occurrence of alewife larvae at offshore stations 12-21 m (Fig. 76),' with no larvae found at shallower depths. However, at the north transect in late June a concentration of 21 larvae per 1000 m was observed at shallow water station L (6 m) . Average size of larvae in Lake Michigan samples at this time was 6.3 nim, S.E*=0.4 (Fig. 74), indicating these were newly hatched during the previous week. These occurrences of larvae in Lake Michigan in late June were the initial indications of successful alewife hatching in Lake Michigan. Absence of alewife larvae in shallower water where they might be expected to occur first was puzzling. It is possible that water currents produced by winds were responsible for dispersal of alewives to deeper water. Wind was considered to be a dominant factor in bringing about dispersal of haddock larvae in the North Sea (Saville 1965) and walleye larvae in Oneida Lake, New York (Houde and Forney 1970). Weather data at time of sampling alewife larvae in June indicated that winds ranged from 0-15 mph from the south to southwest. Observations on 23 June indicated the longshore current was proceeding north to south. The combination of more immediate wind-driven currents and longshore currents may have 255 0.5 X 0.5 Cl U Q 0.5 500 1000 1500 NO. LARVAE/1000 m 2000 3 ■ 2500 3000 Y M UJ Q 0.5 - 0.5 - 0.5 - i 2.5 J . ' t 4.5 J 2000 4000 6000 8000 10000 12000 14000 3 NO. LARVAE/1000 m £> 0.5 J *"1 X ft 2.5 - '? UJ Q 5000 10000 15000 NO. LARVAE/ 1000 m 20000 25000 FIGc 76 . Number of alewife larvae per 1000 m for beach , openwater and intake canal stations in Pigeon Lake near the J. H, Campbell Plant, eastern Lake Michigan, 7-10 July 1977< D= Day ■ = Night 256-' created subsurface currents offshore, moving larvae in that direction also. It is also possible that alewives had spawned in deeper water. In early July, at both north and south Lake Michigan transects, dramatic increases were noted in the concentration of alewife larvae collected at all stations and depths (Fig. 77) indicating that increased spawning in Lake Michigan had occurred by late June* High average numbers of eggs (0-985 eggs/1000 m ), which were probably alewife, began to appear at Lake Michigan beach stations P (s. reference), Q (s. discharge) and R (n. discharge) in June, High concentrations of alewife larvae in Pigeon Lake in early July (Fig. 78) may be due to spawning by alewife in Pigeon Lake, as well as passage of Lake Michigan water containing larvae into Pigeon Lake. The magnitude of concentrations of alewife larvae decreased with diminishing influence of Lake Michigan on Pigeon Lake stations. Pigeon Lake, station M (6 m) and beach station S (influenced by Lake Michigan) in early July had the highest number of alewife larvae per 1000 wr (over 12,000 and 2500 respectively) with less reported at beach station V (undisturbed by Pigeon Lake) and the least number of larvae reported at stations X and T, which are more removed from the influence of Lake Michigan (Fig. 78). No larvae were collected at station Z (intake canal) in late June, while high numbers of alewife larvae were found in early July both at station Z (intake canal) and in entrainment samples (Fig. 78 and Appendix 10). The high concentration of larvae at these two stations (2066-23,494 larvae/ 1000 nr) was probably the result of peak spawning in Lake Michigan during late June. Entrainment of larvae in early July was the highest observed, with 4.6 million larvae (all species included) passing throught the plant over a 24 hr period (Appendix 10). Examination of length-frequency data for just Lake Michigan field-caught larvae in July (Fig. 74) indicated that over 70? ranged between 3.0-6.0 mm (mean 6.7, S.E. = 0.1). Over 58? of all alewife larvae entrained in July were in this 3.0-6.0 mm range (mean 7.7 S.E. = 0.1), indicating a substantial number of newly hatched, entrained larvae may have come from Lake Michigan. Length-frequency histograms from station Z (intake) and Pigeon Lake station M (influenced by Lake Michigan) in July, representing water which was most immediate to being entrained also showed that substantial numbers of small 3*5-10 mm alewife were present (Fig. 74). A composite histogram for all Pigeon Lake larvae indicated that these larvae were generally larger and probably did not represent a. major portion of larvae entrained at this time. A length-frequency comparison between Pigeon Lake openwater stations and Pigeon Lake beach stations in July (Fig. 74) revealed that smaller larvae (<12 mm) were generally found at the deeper openwater stations, whereas larger larvae (>15 mm) tended to be more abundant at beach areas. The reason for this distribution is unclear but it is undoubtedly related to net avoidance and the fact that smaller larvae were more passively moved by currents into deeper water, whereas larger larvae maintained themselves close to 257 CD z: a 0*0 HidlQ OS -> £ — £ r* O © i/l vO m "rt tf) \n o © iq d w ^ id £» 03 CD C +J C/) JZ c o O •!- •r- 2 o +J a 03 II a C QC 03 < CD _l •*- >> d 2 JC 03 CJ Q •r- • 21 H aiD J*J l~4 03 -J &. • cd r^ -M r-*. 03 CTi ^ i— C CD CD a. c O Z3 -D i- O CO <*- C\] co r^ £ r— O « o c O 03 r— en •r** S~ J= CD CJ CL-r- s CD 03 CD > ^ &» 03 03 —J r" C CD i. <+- CD o •r- 4-3 o 2 crt o CD 03 \ r— CD < 03 £ <+- 4J < O C 03 d S- i— z^ CD Q- -Q ff r— 3 r- 2 CD 03 J3 4-5 Q. 03 « £ T3 f^*. 03 ^ O O c , nr ii CD H-4 • O Lu --D 2 ("0 HldjQ Xg o g Ul. £ a 4 CD i < £ 3 2 258 CD Q o o o (w) Hid3Q cd CO 4-> o en ro +J II c rC CD O £ _ £ < > Q o < r 2 . JC >> i o o ro *" II- CD • 2 en C r— CD Q. >> O r— 3 £0 CO i II rk r; Hi -lU. Jl ML o o o < > < o z in q 0 m' «n moo "f ad j: ■* ■> in m m m vn 0 0 0 D CN «■ -^ i. (O ro J CD S- M- CD •r- +-> S CD ro 1— CD ro O C ro S» «—• cd a. E r- 3 r— 21 CD ro -Q +-> Q. ro • £ -O ro 00 O O • 3: 11 o u. ^ 2: O) Hidsa o s u. e uj g <-> s CD i < £ 259 shore. Most spawning may also occur in the openwater of Pigeon Lake. In Lake Michigan, high concentrations of alewife larvae were observed in early July at s. discharge beach station Q (1635-3151 larvae/1000 nr) and n. discharge beach station R ( 1835-8846/ 1000 nr ) as opposed to openwater tows at the 6 m n. station L (54-2176 larvae/ 1000 nr) (Figs. 77, 79). The difference in concentration of larvae found at beach versus inshore stations may be due to the preference of alewife larvae for warmer water . Water temperatures at beach stations Q and R were 31.5 C and 24.2 C respectively; whereas, at openwater station L (6 m - n.) water temperatures were 17-21 C. Extraordinarily high concentrations of alewife larvae (8846 larvae/ 1000 nr) were noted at beach station R (n. discharge) at night. These high concentrations of alewife larvae at stations R and Q (near the present discharge canal) for both early July and mid- July (Fig. 79) when reference beach station P had low concentrations may possibly be due to recruitment of larvae from adults which spawned earlier in the discharge canal. A length-frequency comparison of south inshore stations P (s. reference), A (1.5 m - s.) and B (3.0 m - s.) with north inshore stations Q, R (discharge), I (1.5 m - n.) and J (3 m - n.) indicated that a substantial portion of larvae at north inshore stations were larger (>15 mm) . These larvae were probably early spawned larvae dispersing from their nursery and spawning area, the discharge canal. Thus the two apparent peaks indicated by the length-frequency histogram at north inshore transect stations probably reflects the difference in spawning peaks between Lake Michigan and the discharge canal. The larger alewife larvae observed during July in Lake Michigan (Fig* 74) were approximately the same length as alewife larvae found at Pigeon Lake beach stations in July, supporting the contention of similar peak spawning peak times for alewife in Pigeon Lake and the discharge canal. Mid-July samples (13 July) were only taken from Lake Michigan north transect stations (1-1 m, J-3 m, L-6 m, R-beach, n. discharge). Results of these collections indicated that high concentrations of alewife larvae, up to 6200 larvae/ 1000 nr were present (Fig. 80). Concomitantly, numbers of alewife larvae entrained on 14 July decreased considerably (Appendix 10), which may be due to larvae reaching such a size that they can more easily stay in a preferred area. Even if larvae do reach the intake canal they can resist or orient to currents and thus maintain themselves there, decreasing their vulnerability. Thus peak entrainment of alewive larvae seems to occur shortly after a hatching peak when small larvae are planktonic and passively moved by currents . Lake Michigan south transect openwater stations experienced significant declines in the concentration of alewife larvae found on 25-28 July when compared with early July (Figs. 77, 81). Interestingly, alewife concentrations at beach station P (s. reference) did not exhibit this decline (Fig. 79)- 260 ■ - • . 1 1 I 3! ' 00 - r I ' i I r| i r! r i 5 o o o Ui < > a: < o 03 CD -p CO JZ O 'I- 03 II JZ o 03 QJ C H3 03 Q •r- It In a; 03 * -J f^ o r— m n ws o o o \ Hi < > < o sz £ «3 en O ••- o -c o o 03 OJ -J 03 > c 03 a; > , 6.0 - 8.0 - j 0.5 - ! I4"0' X £] 8,0 - Q 1 ' ' ' » ' » 0.5 - " ' I 3.0 - 6.0 - "■"' 1 0.5 - r: u 2.0 0.5 4 0.5 6200 1000 2000 — p— 3000 — r — - 4000 5000 NO. LARVAE/ 1000 rrT FIG, 80. Number of alewife larvae per I000 m for Lake Michigan stations (north transect and beach station R - n. discharge) near the J. H. Campbell Plant, eastern Lake Michigan, 13 July I977. Samples were only collected at surface, mid-depth and near bottom at all stations deeper than 3 m. □ = day ■ = night 262 It 1 JJ wO in m m m iri i q q o on V if) (uj) Hld3Q Oe "> £ - (1 ll 0 XL Ik u m o 6 -* oo in m m in o in ^rs! d •+ <6 ~+ 6 o io m iq io in ^ ci « * * < ^9 q tn o cn *» in CD < •r- >> -j JZ 03 d 03 o -J o 03 CT> 2: i— c > CLr— O 3 s- O CO 1 £ cm o * o c O 03 r— cn o •r m Q-T- 03 a> o > -i* o S- 03 03 -J C cu s- E <+- M- 4-> OS o c o o < -J 03 o £ QD i < £ 263 Nearshore waters in late July had temperatures between 15*5-16*0 C and may have been selected by alewife larvae over cooler offshore waters. Stations A (1.5 m - s.) and B (3 m - s.) in late July had water temperatures between 10 . 8- 13*0 C, and also seemed to have higher alewife concentrations than other stations with cooler water temperatures (Figo 81). Low water temperatures at Lake Michigan stations in late July were undoubtedly caused by an upwelling of cooler water, since water temperatures in early July and August were much higher in comparison. In general, the sporadic occurrence of high concentrations of alewife larvae in late July at the Lake Michigan south transect was usually related to higher water temperatures . Since many of the larvae observed in late July were smaller larvae (3-6 mm), it is unlikely that these larvae were exhibiting an active preference for warmer water temperatures. It was more likely that warmer water, containing larvae hatched in mid- July was replaced by cooler upwelled water (containing few larvae). A mixing of these two masses of water was probably incomplete at the time of sampling. Larger larvae (>15 mm) observed at warmer water temperatures may be exhibiting an active preference for warmer water as was observed by Jude et al. (1979). North transect collections in late July when compared to samples procured in early July also experienced a decrease in the number of alewife larvae found similar to that observed at the south transect (Fig. 77, 80 and 81). It appeared from our data that north offshore Lake Michigan stations (L-6 m to 0-12 m) had consistently more larvae in late July than comparable stations to the south (C-6 m to E-12 m) . Examination of water temperature data (Appendices 6 and 7) from late July indicated that stations L-6 'in to 0-12 m north had elevated temperatures at all depths (6.0-13 C, most above 10 C) compared with stations C-6 m to E-12 m south which had temperatures from 5-13 C, mostly below 10 C. North transect elevated water temperatures, apparently preferred by alewife larvae, allowed a more even distribution of alewife larvae at all depths; whereas they were found mainly in the warmer surface waters at south transect stations. It is evident that upwelled colder water was thoroughly mixed with discharge water at north stations causing alewife larvae to be widely distributed throughout the entire water column in this area during late July. Thus the apparent differences in larvae distribution between north and south transects may only occur during times of upwellings. Again beach station collections along both transects exhibited continued high numbers of alewife larvae during late July which was probably due to higher water temperatures (Fig. 79). It is interesting to note that extraordinarily high average concentrations of eggs (up to 511,700 eggs/ 1000 m , Appendices 6 and 7) were found at beach stations P, Q and R indicating the distinct possibility of continued alewife spawning there through 25-28 July. 26k Sled tow data for late July (Appendix 9) indicated that alewife larvae in the bottom strata at south transect stations were more concentrated at shallower depths. Lake Michigan south beach station P (s. reference) and openwater stations A (1.5 m - s.) to C (6 m - s*) had notably higher bottom strata concentrations (72-1084 larvae/ 1000 m ) than stations D (9 m - s.) toH (21 m - s.) which had 0-475 larvae/ 1000 m . There was no apparent relationship between water temperature and alewife density since no notable differences in water temperature were observed between depths, other than the 16.0 C temperature at the south beach station P which was higher than the 6.0-9*8 C measured at other stations (Appendix 6). Highest concentrations of alewives from north transect bottom sled tows were observed at inshore beach station Q (835-1372 larvae/1000 m3) and R (5261 larvae/1000 nr), as well as at the 1 .5 m station I where an extremely high concentration of 15,884 larvae/ 1000 m was found. Length-frequency comparisons of alewife larvae captured during inshore July sled tows at Lake Michigan beach stations (P, Q, R) , 1.5 m stations (A, I) and 3 m stations (B, J) compared with inshore stations C (6 m - s.) fro H (21 m - s.) and L (6m - n.) toO (12 m - n.), indicated that smaller alewife larvae were more frequently found at offshore stations, and larger alewife larvae tended to occur more frequently at inshore stations (Fig. 74). This was also illustrated by a similar comparison using net tow data (Fig. 74). Extremely low densities of entrained alewife were observed on 29 July (20-26 larvae/ 1000 m ) when compared with weeks both previous and after collection of these samples . An upwelling in Lake Michigan on 29 July was suspected as being responsible for this observation and gives credence to the hypothesis that many alewife larvae eventually entrained were derived from Lake Michigan. An intake water temperature of 12.5 C was recorded on 29 July; whereas, temperatures of 22.8-23.4 C were recorded on 21 July and 18.3-19.4 C on 3 August. Lower water temperatures in the intake canal (station Z) in late July also coincided with lower alewife concentrations (Figs. 78 and 82). Pigeon Lake station M (6 m) in late July also had water temperatures of 10.0-11.7 C; when few (Fig. 82) alewife larvae were found. Pigeon Lake beach stations S and V, as well as openwater station X (0.5 m) which had warmer water had alewife concentrations up to 1865 larvae/ 1000 ra (Fig. 82) indicating that upwelled water displaced warmer Pigeon Lake water. Alewives in the outlying warmer areas were not subject to entrainment, while water being drawn into the plant from Lake; Michigan contained fewer larvae causing lower entrainment values. During August sampling, water temperatures at Lake Michigan south transect stations were elevated at all depth strata, with the exception 265 0.5 L T X 0.5 a. UJ Q 0.5 -■ 4000 8000 NO LARVAE/1000 m 12000 16000 3 20000 X a, 0.5 0.5 O.D 4.5 ■ ^ 0.5 X 400 800 120C 1600 NO. LARVAE/1000 m 20 40 60 NO. LARVAE/ 1000 m 2000 80 FIG. 82. Number of alewife larvae per 1000 m3 for beach , openwater and intake canal stations in Pigeon Lake near the J- H. Campbell Plant, eastern Lake Michigan , 25-28 July 1977. □ = Day ■ = Night 266 of the bottom, when compared with July values. This apparently allowed, alewife larvae to become more widely distributed throughout the water column (Fig. 83) which was similar to the distributional pattern observed at north transect stations in late July (Fig. 81) c North transect stations in mid-August also showed alewife larvae to be widely distributed throughout all depth strata, with somewhat higher concentrations observed at beach station R (n. discharge) (Figs. 79, 83)* Eggs were noticeably absent from all Lake Michigan samples on 15-19 August indicating possible cessation of alewife spawning (Appendix 6 and 7). Occurrence of alewife larvae in sled tow samples from Lake Michigan stations was sporadic during mid-August , with measurable concentrations recorded from stations E (12 m - s„, 18 larvae/ 1000-nr) , G (18 m - s., 72 larvae/1000 nr) and J (3 m - nM 58 larvae/1000 nr). All larvae caught in sled tows during August were small (<10 mm) larvae (Fig. 74). In Pigeon Lake, alewife larvae during mid-August were found primarily at stations influenced by Lake Michigan (M - 6 m and S - beach) with some caught at beach station V (undisturbed Pigeon Lake) and openwater station X (undisturbed Pigeon Lake) (Fig. 84 ). The intake canal (Z) had concentrations up to 249 alewife larvae/ 1000 m . Again the alewife length-frequency comparison of openwater Pigeon Lake stations with beach stations in Pigeon Lake (Fig. 74) indicated lower numbers of larger (>20 mm) alewife larvae and higher numbers of small larvae in deeper water. The reverse was true for beach stations. Entrainment samples from 3 and 10 August contained relatively high concentrations of alewives (Appendix 10) when compared to July (with the exception of the upwelling period-late July) . Sampling in Lake Michigan and Pigeon Lake was not performed concurrent with these earlier August entrainment samples. Decreased concentrations of alewife in entrainment samples for late August, and the continuing decline through December, probably reflects growth of many larvae from the arbitrary "larvae" classification (less than 25*4 mm) into the "fry" classification (larger than 25*4 mm). The substantially increased number of fry observed in entrainment samples in August (9-2193 fry/ 1000 m , Appendix 11) substantiates this contention. Density of alewife larvae entrained, on 10 August was 1004-1108/1000 m , which then declined to 30-53/1000 nr' on 16 August (Appendix 10). Numbers entrained on 16 August were low despite concentrations of 0-249 alewife larvae/ 1000 m at the intake canal and high average values observed at Pigeon Lake beach station S (3223-4653-Jarvae/1000 nr) and openwater 6 m station M (up to 3324 larvae/ 1000 nr) . Considerable numbers of fry (up to 549 fry/ 1000 m3) were also found at these three stations. Reason for low entrainment of alewives on 16 August was 261 k ■*-q- I 1 rf JiliU- O o o < > < o z CD S- rg CD 4-> SZ JZ en SZ Z o •p- !l a > cn ^ JZ U II in m in ui m cm *° in (w) Hid3Q 0£ — E iLL CD J^ rO «J . rs* s- r^ cd cr> +J r— fQ B 4-3 C C^ CD 3 CL O) O 3 <+~ ,_ CO u^ £ •— O « o c O re r— en °r~ S- JC CD CJ GL-r- s CD fO CD > ^ i. re re — i r- ■» 1 £ SZ CD S- o <+- CD o •f- 4J o 3 \ CD fO < > r— CD re a: « < <+- 4-3 o c d ra z &. p— CD Q~ jQ cs ■— " 3 i — Z CD JD CL ra m cj CO m o o q in in ininq ■* r^ d •*» ad ^ •* m m in m m in o o m »n « o 3 200 250 FIG. 84. Number of alewife larvae per 1000 m for beach, openwater and intake canal stations in Pigeon Lake near the J. H0 Campbell Plant, eastern Lake Michigan, 15-19 August 1977. □ = Day ■ = Night 269 probably related to size of the larvae, A length-frequency histogram for Pigeon Lake and Lake Michigan (Fig. 74 ) indicated that many larvae were longer than 15 mm, and probably easily avoided or maintained themselves in the intake current . It is probable that factors other than inability of alewife to avoid intake canal current were responsible for the entrainment patterns observed. The drastic decline in the number of fry entrained between 10 and 16 August was undoubtedly related to the fact that fry had grown to a size that was no longer susceptible to entrainment, even at locations very close to the actual intake. Alewife larval concentrations measured during September at Lake Michigan stations indicated that both north and south transects had similar concentrations and distributions of larvae (Fig. 85), with the exception of station A (1.5 m - s.) and B (3 m - s.) which had higher concentrations of alewives than comparable north transect station samples. Concentrations of alewives ranged from 0-351/1000 m at these south stations as opposed to 0-37/1000 m^ at north stations . In general, the trend during September at all Lake Michigan stations was a decline in alewife larvae concentrations, probably again due to larvae growth, mortality and increased ability of larvae to avoid the net. Larvae were longer than 15 mm both in September sled tows and openwater tows in Lake Michigan (Fig. 74). There was a marked increase in .densities of alewife larvae at inshore stations in Lake Michigan during daytime September sampling, compared with nighttime (Fig. 85 )• Inshore south transect Lake Michigan stations P £ beach), A (1.5 m) and B (3 m) samples contained up to 361 larvae/ 1000 m (Figs. 79 and 85) which was in sharp contrast with deeper south transect stations C (6 m) to H (21 m) where only two occurrences of larvae were observed during the day, one at station C (6 m - s.) at the surface (19 larvae/ 1000 m ) and one at station D (9 m - s.) at a depth of 6 m (16 larvae/ 1000 m ). Night samples from south transect stations, however, indicated that larvae concentrations were greatest at deepwater stations C (6 m - s, , up to 30 larvae/ 1000 nr) and D (9 m - s., up to 38 larvae/ 1000 nr) when compared with shallower stations, demonstrating an offshore daily movement by this size alewife (>15 mm) (Fig* 85 ). Concentrations of 19 and 14 larvae/1000 m were also observed at stations E (12 m - s.) and F (15 m - s.) respectively at night in September. Due to net avoidance during daylight hours by alewife in this size range (16.5-25*4, S.E. = 0.6) it is probable that concentrations of larvae at sampling stations during the day were underestimated. However, since net avoidance is appreciably diminished during dark hours, a movement of alewife from the beach zone to offshore waters at night was clearly indicated by our data< This trend (described above) toward inshore movement by larval alewives during the day was also noted at the north transect stations in September when an average of 84 alewife larvae/ 1000 m were observed at 270 CD 03 CD CD »r- c 2: 00 II §■ •I— 03 o o o \ u < > < o 2 CO >> 03 d Q 03 CD II •1— JZ u D o o («i) HlcGQ OS 2 -5 ^ Lid uJ O O o < < s £ a o m in w o o •^ K 6 V 00 ~ ■+ A 10 in in « «n q o a. a. o cd 00 O <+- C\J I CO r— • E C\J O * O C O A3 r— CD •r- L- JZ CD (J Olt- cd 03 CU > ^ S. 03 03 —I C CD S- <+- CD •r- +J 5 CO CD 03 r- CD 03 <+- +J o c 03 S- 1— CD Q. -Q £ r~ 3 1 — "ZL CD -Q CL • E 03 00 0 O) HldlQ X £ o e ^- £ UJ £ CD c < £ 271 beach station Q (s« discharge) during the day; no larvae were found at night. Openwater stations L (6 m - n.) to Q (12 m - n.) showed moderate concentrations at night (0-57 larvae/1000 m ), but the tendency toward inshore movement during the day was not as distinct as exhibited at south transect stations in September. Pigeon Lake data at this time in September showed alewife larvae were present at beach station S (influenced by Lake Michigan) during the day (4571 larvae/ 1000 nr) and absent at this station at night (Fig. 86). However* at Pigeon Lake openwater station M (6 m), up to 136 larvae/ 1000 nr were observed at night during September, with an absence of larvae during the day. These data indicated a preference for inshore shallows by Pigeon Lake larval alewives during the day and offshore movement to deeper water at night, similar to that observed in Lake Michigan. In October, no larvae were collected at Lake Michigan beach station P (s. reference); however there was an average density of 91 alewife fey/ 1000 m in duplicate night samples. An average of 343 larvae/ 1000 m was observed in day samples taken at beach station R (n. discharge), but no larvae were found at station Q (s. discharge). Fry densities at these north beach stations (Q and R) ranged up to 844. fry/ 1000 nr (Appendix 11).. Although no openwater tows were taken in Lake Michigan during October, densities of larvae at Lake Michigan beach stations (P, Q and R) are indicative of a trend toward decreased numbers, similar to that observed in September. Observations of larvae in sled tow samples in October were sporadic, with larvae observed at stations C (6 m - s.)f I (1.5 1 - n.) and J (3 m - n.) in densities ranging from 20 to 36 larvae/1000 (Appendix 9). Pigeon Lake samples from October contained no alewife larvae with the exception of 90 larvae/ 1000 nr observed at 1.5 m openwater station X (influenced by Pigeon River) and 45 and 78 larvae/ 1000 m at night at station M (influenced by Lake Michigan) (Appendix 11). Entrainment in October was extremely low ranging from 373-7500 larvae entrained in a 24-hr period (Appendix 10). October alewife fry concentrations in Pigeon Lake (Appendix 11) were fairly comparable with late September densities and ranged from 0-78 larvae/ 1000 nr. It was apparent that most alewives in October were able to maintain themselves in or away from the intake current, depending on their behavior and preferences. No alewife larvae were found at any Lake Michigan stations in November. In contrast however, Pigeon Lake samples contained densities of larvae from 0-38/1000 nr with additional fry densities of 0-174 fry/ 1000 nr at openwater station M (6 m) (Fig. 87 and Appendix 11 ). Fry also occurred at station Z Lintake canal) during November in concentrations up to 22 /1000 nr (Appendix 11). 272 0.5 X 0.5 - Q- U Q 0.5 0.5 - ^ 0.5 E a a 0.5 H 2.5 4.5 JL 0.5 - X I- °- 2 5 Q 1000 2000 3000 4000 NO. LARVAE/1000 m 40 80 120 NO. LARVAE/ 1000 m 20 40 60 NO. LARVAF./1000 m 5000 16C 80 FIG. 86. Number of alewife larvae per 1000 m3 for beach, openwater and intake canal stations in Pigeon Lake near the J. H. Campbell Plant, eastern Lake Michigan, 21-23 Setpember 1977. D = Day ■ = Night 273 Y M Y M a. a 17 - - 20 October 0.5 - 0.5 - 0.5 - 2.5 - 4.5 - a, u a 20 40 60 80 NO. LARVAE/ 1000 rrT 10 20 30 NO. LARVAE/ 1000 m" 100 0.5 - 31 October - - 2 November 0.5 - 0.5 - ? 5 - '" ' i . _ i — i .I — p — « — « • * — i 40 fig. 87. Number of alewife larvae per 1000 m3 for openwater Pigeon Lake stations near the J.H. Campbell Plant, eastern Lake Michigan, 1977. □ * Day ■= Night 27k 3 In December alewife fry concentrations of up to 19 /1000 m were noted in Pigeon Lake, openwater station M (influenced by Lake Michigan). No other larvae or fry were collected. Only one station was sampled in Lake Michigan in December, station L (6 m - n.) , no larvae were found. Maximum entrainment losses of alewife larvae during the 1977 sampling period occurred in early July (Fig* 88). This period coincided with maximum densities of larvae observed at Lake Michigan stations. Alewife larvae entrainment was maintained at relatively high levels (greater than 0.4 million larvae/24 hr period) from 7 July through 10 August. The drastic decrease in alewife larvae entrained noted on 29 July was probably due to an upwelling which occurred at that time. Although post larvae and fry were entrained, newly hatched larvae seemed particularly susceptible to entrainment. Decreased numbers of alewife larvae entrained after 10 August was due to growth of larvae into the fry stage, as indicated by the increased number of fry entrained (Fig. 89 )• Peak numbers of fry entrained occurred in August, when most fry were small. Minimal entrainment of alewife larvae occurred after 19 September. No fry entrainment occurred from mid-November through December; which is probably indicative of alewife movement from the area. Cvprinidae Complex State of the art identification of cyprinid fish larvae is only now starting to address some of the problems in these areas , We have attempted to do our best in separating the various cyprinid larvae collected during sampling around the J. H. Campbell Plant using existing keys and literature, (some only now being published) and reference larvae from the Great Lakes Regional Fish Larvae Collection (GLRFLC) located at the Great Lakes Research Division Fisheries Laboratory. Because this was the first year of study and we had little experience working with many of the Pigeon Lake larval species , some compromises had to be made. The major species of cyprinid larvae (most numerous) were spottail shiners and bluntnose minnows. Less common species included golden shiner and carp. Other rarely caught cyprinids were: goldfish, emerald shiner, bigmouth shiner, blacknose shiner and longnose dace. When first picking samples and identifying larvae we established a special code (XM) to designate unknown cyprinid larvae. Many of the larvae collected from Pigeon Lake and some from Lake Michigan were called unknown cyprinids. To facilitate completion of this report, we reported these larvae as unknown cyprinids. However, we are in the process of developing the necessary expertise from newly published literature, GLRFLC and outside research scientists competent in this area, and we expect to re-identify as many unknown cyprinids as possible. Thus data presented for each of the known cyprinids in this section should be considered tentative, until a final determination about the identity of the unknown larvae is reached. 275 39S.730 1.301.786 700 -j 1 1 0 i r | 1 0 p 525 J " 1 | j i 1 i ! ! i ••- ! t i ! i i ! I i ! 1 75 - 1 J 1 | i i i i i i 1 ^ 1 Qi.r> ^ ALEWIFE ENTRAINED— LARVAE (TOTAL NO.) IUK- j>- i- / 5- i" a" c? ^ « « The spottail shiner is the most abundant species of minnow in the Campbell Plant area. Large numbers have been observed in both Pigeon Lake and Lake Michigan, and an understanding of their larval distribution and seasonal abundance is paramount to gaining a full understanding of their role in each ecological system. Spawning of spottail shiners occurred primarily in June and July in southeastern Lake Michigan during 1973-74 (Jude et al. 1979). Spawning occurs over sandy shoals (Scott and Grossman 1973), with spawning in clumps of algae also reported (Dorr and Miller 1975). Yearling spottails from Clear Lake, Iowa (70-90 cam) were reported to contain 100-1400 eggs, while 2-yr old specimens contained 1300-2600 eggs (McCann 1959). Spottail shiner larvae were collected in the Campbell Plant area during our first sampling trip in early June, Lake Michigan beach 277 stations R (n. discharge) and Q (s. discharge) exhibited average densities of 146 and 73 larvae/ 1000 m respectively (Fig. 90). These concentrations suggested the possibility that localized spawning in the immediate area of the present discharge, or possibly in the discharge canal itself, occurred in May. Average size of spottail shiner larvae for pooled Lake Michigan stations at this time was 4.9 nun (SoE» = 0*3 mm) (Fig. 91)? indicating recent hatching as Dorr and Miller (1975) found newly hatched spottails from Lake Michigan to average 4.6 mm. Spawning beds of centrarchids were noted by Consumers Power plant personnel in the discharge canal, which indicated there were areas probably suitable for spawning of spottails there. In contrast to the north transect, no spottail larvae were collected at the south transect in early June, indicating that spawning in May had apparently not occurred there. Water temperatures at south transect beach station P ranged from 9.5-13.0 C in early June, compared with temperatures of 8.0-17*0 C recorded at north beach stations at the time of larvae sampling c Pigeon Lake samples from early June indicated that spottails also spawned there in May. High concentrations of spottail larvae were observed in Pigeon Lake samples in early June at beach stations T (influenced by Pigeon River) and S (influenced by Lake Michigan) with lower densities observed at station V (undisturbed Pigeon Lake) (Fig. 92). No spottail larvae were collected in the intake canal (station Z) in early June. All occurrences of spottail larvae during early June in both lakes, with the exception of those at beach station Q (s. discharge), were observed at night. General absence of spottail larvae in samples collected during the day may be due to net avoidance or the demersal character of this species during daylight hours which was noted by Jude et al. (1975); however, no sled tow samples were 'taken in June to verify this finding. Sled tow data from July and August however amply demonstrated the affinity of spottails for the bottom. Late June sampling at Lake Michigan south transect stations showed no spottail larvae present. However, high densities of unidentified fish eggs were found (average 757 eggs/ 1000 nr) at station P during the day which may indicate some spottail spawning at this time (Appendix 6). North beach stations Q (s. discharge) and R (n« discharge) continued to have concentrations of spottail larvae in late June comparable to early June (Fig. 90). Occurrence of eggs at north beach stations (up to 985 eggs/ 1000 m ) (Appendix 7) may indicate continued spottail spawning in the area; some eggs may also be those of alewife. Water temperatures in late June ranged from 16.0-19-6 C at north beach stations and 16.0- 17* 5 C at south transect beach station P* Although water temperatures for both early and late June were not extremely different between north and south stations, there does appear to be significant differences in the spawning of spottails, with earlier spawning indicated at Lake Michigan 278 0.5 - 31 May - 3 June T v^.* \ J— Q. Ui Q 120 0.5 X 0.5 Q. Ui Q 17 - 23 June ■i »■ 40 120 180 200 0.5 - Q x °'5 0- 7 - 10 July i R 0.5 - ? X 0.5 - \- Q- Ui Q 0.5 - 25 - 28 July Q p -1 Q X 0.5 - CL 2000 4000 6000 aooo 10000 12000 NO. LARVAE/ 1000 m3 15 - 19 August NO. LARVAE/ 1000 m FIG. 90. Number of spottail shiner larvae per 1000 m3 for Lake Michigan beach stations near the J. H. Campbell Plant, eastern Lake Michigan, 1977. D * Day ■ » Night 219 40 -I Lake Michigan 30- pooled X -- 4.9 (0.3} 20- N=8 10- 40 1 30- Pigeon Lake pooled X = 9.5(l.2) 20- N = 29 10- ,1 -UuijU JUNE 40 ■ Pigeon Lake beach ■ X = i0.7 ii.5) N = 23 ■ ,1 INI, JU 10 15 20 25 Lake Michigan pooled X»ll. 3(0.4) N = 365 Hn. t , 1 1 Itj i,iMilnfd*L.i. JULY Lake Michigan inshore -day X = 6.2 (0.4) N=79 *°] 45.l6ll46.77 R Lake Michigan 30 1 0. 10- N. transect- day f= 5.7 1 N»62 Lake Michigan N. transect - night X»t3.l(0.5) N=200 *©- Pigeon Lake pooled *» 1 1.4 (0.1) N»3502 Pigeon Lake beach *X = 11-5(0.1) N*3437 Lake Mich gan sled - poo ed X' 11.6(0.3) H- ■217 I ■JllllllllJlll.lllllllll,,,. Lake Michigan sled- day X = 8.9 (0.4) N*90 W 40 -i 66.67 Pigeon Lake 30- openwater X* 5.2 (0.1) 20- N*6 KH 15 20 25 Lake Michigan inshore- night X« 13.5(0.4) N*263 5 TO 15 20 25 40-1 46.34 j Lake Michigan 30- stations .2)2 m X» 5.3(0.1) 20- N=4I 10- I tilll 10 15 20 25 Pigeon Lake openwater- day X= 1 2.4(1.4) N»8 20 25 Lake Michigan sled- night X* 13.5(0.3) N*I27 IImLw- !0 15 20 25 5 ^ TOTAL LENGTH (mm) 15 20 25 Lane Michigan stations -£6m X* 4.8 (0.1) N = 23 I 5 10 41.54 Pigeon Lake Openwater Pooled Day, Night X=5.8 (0.1) N*65 pi I 1, 1 1 l ,» i, 5 10 IS 20 25 40- J47.37 I Pigeon Lake 30- openwater- night X* 4.9(0.1) 20- N=57 W- j 1 2 10 IS 20 25 40- 60.00 Entrained 30- X* 6.7(0.9) 15 20« 10- I III FIG. 91 . Length- frequency histogram for larval spottail shiner caught at selected pooled stations in Lake Michigan and Pigeon Lake near the J. H. Campbell Plant, 1977, All tows, were net tows unless sled tows were specified. Inshore means all stations 3 m or less in depth (X=mean, N= total number of larvae used in the comparison., standard error is given in parenthesis). 280 X 0.5 -fa Q. UJ Q 0.5 -■ 100 200 :joo NO. LARVAE/ 1000 m 400 3 500 600 M 0.5 - 0.5 H Q 0.5 2.5 4.5 40 80 120 NO. LARVAE/ 1000 m 160 fig. 92. Number of spottail shiner larvae per 1000 m3 for beach and openwater stations in Pigeon Lake near the J. H. Campbell Plant, eastern Lake Michigan 31 May - 3 June 1977. □ = Day ■ = Night north beach stations or in the discharge canal. Some spottail larvae (20 and 21 larvae/1000 nr) were also noted at station L* (6m - s.) at night on 17-23 June (Fig. 93). In Pigeon Lake during late June, spottail larvae were noticeably absent from Lake Michigan influenced stations (S - beach and M - 6 m) , 28] 0 (I2m-N) N ^ (9m-N) £ L (6m-N) 0.5 3.0 - 6.0 - 9.0 11.0 0.5 2.5 4.5 6.5 X uj 8.5 Q 0.5 2.0 4.0 5.5 J (3m-N) (l.5m-N) 0.5 H 2.5 0.5 - -j — — — ■■ — r "T > 1 ' T-" T" » I 10 15 20 25 NO. LARVAE/ 1000 m* fig. 93c Number of spottail shiner larvae per 1000 m3 for north transect openwater stations in Lake Michigan near the J. H. Campbell Plant* eastern Lake Michigan, 17-23 June 1977 e □ = Day ■= Night 282 V T S 0.5 X 0.5 Q. UJ Q 17 - 23 June 0.5 - / 0.5 400 800 21 - 23 Seotember 1200 1600 40 80 120 NO. LARVAE/ 1000 m3 160 200 FIG. 94. Number of spottail shiner larvae per 1000 m3 for beach stations in Pigeon Lake near the J, H. Campbell Plant, eastern Lake Michigan, 1977. D s Day ■= Night as well as the intake canal (station Z) (Appendix 8)* The reason for this may be related to water temperature. Temperatures in late June at Lake Michigan influenced stations ranged from 15*1-17*8 C, whereas Pigeon Lake beach stations T and V had temperatures from 20.0-24.4 C. Concurrently, these stations exhibited higher spottail larvae densities (Fig. 94). It is also possible that net avoidance may be a factor in the decreased catches observed in late June. While no larvae were found at beach station S (influenced by Lake Michigan) in late June, extremely high concentrations of eggs were found (15,306-18,190 eggs/1000 nr) , which may indicate spawning of spottails at this station had been at high levels in late June. High densities of eggs at station S in late June (Appendix 8) were coincident with high densities of eggs at Lake Michigan south beach station P (757 eggs/ 1000 nr found at night) (Appendix 6) and Lake Michigan north beach station Q (338 eggs/ 1000 nr reported at night). Although these occurrences of eggs may be signs of spottail spawning, some alewife spawning was also indicated. Careful examination of length-frequency histograms for spottails caught during June (Fig. 91) showed that larvae collected in Lake 283 Michigan at this time (all pooled net tow samples) were around 4 . 5-6.0 mm; whereas, Pigeon Lake larvae pooled samples showed a length range much wider, from about 5 to 23 ram . This evidence was strong support for the two conclusions discussed previously: 1.) Recent spot tail spawning had occurred in Lake Michigan, apparently in or around the discharge canal, which appeared to be initial spawning in this vicinity of Lake Michigan during 1977* This early spawning transpired in a localized area, no spawning apparently occurred at the south transect • 2.) The wide range of spottail lengths observed at Pigeon Lake stations indicated that spawning by spottail shiners occurred there much earlier (early May on) than spawning in Lake Michigan. Larvae caught at beach stations in Pigeon Lake exhibited a noticeably wider length interval than those smaller specimens caught in openwater samples (Fig. 91). This observation was partly the result of decreased net avoidance at beach stations (more vegetation) allowing larger larvae to be captured, but may also be indicative of the behavior of newly hatched larvae (which these were). Apparently some of these 1-3 day-old larvae were pelagic and planktonic, as indicated by their presence at these openwater stations . These data may also demonstrate a transfer of newly hatched spottail larvae from Lake Michigan and through Pigeon Lake in the cooling water utilized at the Campbell Plant. Spottail larvae first occurred at Lake Michigan south transect stations in early July (Fig0 95) , indicating spawning in this area occurred sometime in June. Spottail larvae at this time were distributed from the nearshore area station P (s. beach) (Fig. 90) to a depth of 12 m - s. station E (Fig. 95). There was a noticeable absence of spottail larvae at depths exceeding 12 m. Catches at openwater stations (B, 3 m - s. to E, 12 a - s.) were all at night, with a tendency of larvae to be found in deeper strata near bottom. An uhusually high density of spottail larvae compared with openwater stations was noted at beach station P (s. reference) during the day (Fig. 90). Many larvae designated XM (unknown cyprinids-Appendix 7) at this time were probably spottail larvae, and hence would generate even higher night densities at beach stations. North Lake Michigan stations in early July showed high densities of larvae present at beach stations Q (s. discharge) and R (n. discharge) (Fig. 90). Although highest concentrations there were observed at night, substantially high numbers were also found in day samples at station R. No larvae were found at openwater station L (6 m - n.) in early July. High densities of spottail larvae were found at night in early July samples from Pigeon Lake at Lake Michigan influenced station M (6 m) and S (beach station) (Fig. 96). These high concentrations may indicate that peak spawning at beach station S (influenced by Lake Michigan) occurred coincidently with spawning of spottails in Lake Michigan. It 28U H (21m-S) G (18m-S) F (15m-S) E (I2m-S) 0.5 5.0 10.0 - 15.0 - 20,0 - 0.5 4.0 9.0 ^ 14.0 17.0 A 0.5 H 4.5 8.5 11.5 14.0 w 0.5 i X UJ Q 6.0 «, 9.0 11.0 0.5 D (9m-S) c (6m-S) B (3m-S) A (l.5m-S) 2.5 4.5 6.5 8.5 0.5 2.0 H 4.0 5.5 0.5 2.5 4 0.5 - — , — 100 200 300 400 NO. LARVAE/ 1000 rrT fig. 95. Number of spottail shiner larvae per 1000 m3 for south transect openwater stations in Lake Michigan near the J. H. Campbell Plant, eastern Lake Michigan, 7-10 July 1977. □ = Day ■ = Night 285 Y 3.5 | X 0.5 h- CL LU Q 0.5 0.5 - 0.5 CL UJ Q 0.5 2.5 -i 4.5 2000 4000 6000 8000 1G0O0 NC. LARVAE/ 1000 m 400 800 1200 1600 NO. LARVAE/ 1000 m fig. 96 o Number of spottail shiner larvae per 1000 m3 for beach and openwater stations in Pigeon Lake near the J. H. Campbell Plant, eastern Lake Michigan, 7 - 10 July 1977. D = Day ■ » Night is evident, however, that spawning of spottails did occur to some degree in May at this Pigeon Lake station. This earlier spawning was responsible for the densities of spottails at Lake Michigan influenced stations of Pigeon Lake in early June. There were no larvae found at station Z (intake canal) in early July. In mid- July, only Lake Michigan north transect stations were 286 sampled. Spottail larvae were observed at this time at station I (1.5 m - n.) and J (3 m - n.) (Fig. 97)* The higher density of spottail larvae at station I (1.5 m - n.)f as well as lack of spottail larvae at depths 6-12 m, clearly demonstrated the tendency for larvae of this species to remain inshore. Sled tow samples taken on 20-21 July substantiated the contention. At south transect stations P (beach), A (1.5~m) and B (3 m)- densities of spottail larvae ranged from 0 to 6791/1000 m in sled tows (Appendix 9)* Offshore south transect stations showed no spottail larvae present in sled tows with the exception of a low density of 49 larvae/ 1000 m at station C (6 m). North transect stations showed a similar trend in sled tow samples with spottail larvae concentrations of 0-4431 larvae/ 1000 m observed at Lake Michigan beach stations Q (s. discharge) and R (n. discharge) and station I (1.5 m - n.) (Appendix 9). No spottail larvae were observed deeper than 1.5 m on 20-21 July. Late July Lake Michigan samples showed clearly that spottail larvae were inshore at depths less than 2 m. Lake Michigan south transect station P (beach) had densities from 435-4173 larvae/1000 nr (Fig. 90), while station A (1.5 m - s.) was the only offshore station with spottail larvae present (0-64 larvae/1000 m ) (Fig. 98)0 This distribution pattern was consistent at the north transect, where spottail larvae were only collected at beach stations Q (s. discharge) and R (n. discharge) in concentrations ranging from 0-10,675 larvae/ 1000 nr (Fig. 90); none were found at offshore stations I (1.5 m) through 0 (12 m) (Appendix 7). An upwelling, which occurred during our sampling, apparently had little effect on spottail larvae distribution. Samples from Lake Michigan at this time also indicated that there were increased numbers of spottail larvae growing into the fry classification (Appendix 11). Samples taken in Pigeon Lake in late July indicated extremely high densities of spottail larvae ( 13*978-283,674 larvae/ 1000 nr) at beach station S (influenced by Lake Michigan) (Fig. 99), the highest concentration of spottail larvae we ever recorded. An overview of all monthly data suggested that these high densities in late July merely reflected extensive use of this Pigeon Lake habitat as a nursery area for spottail shiners. Beach station S may be selected for spawning by spottail over other Pigeon Lake beach stations due to its sandy bottom and moderate vegetation. Some spottail larvae were also observed at station M (6 m-Pigeon Lake) at the surface (100 larvae/1000 nr) and 2.5 m depth (94 larvae/1000 nr) in late July (Fig. 99)* No spottail larvae were observed at station Z (intake canal) in late July. . Length- frequency comparisons of Pigeon Lake spottail larvae collected in July (Fig. 91) indicated larvae at openwater stations M (6 m) , X (1.5 m) and Y ( 1 m) were smaller Cx = 5.8 mm S.E. =0.1) than those collected at beach stations S (influenced by Lake Michigan), V (undisturbed Pigeon Lake) and T (influenced by Pigeon River) (x = 11.5 mm) S.E. = 0.1. This may indicate that some small spottail larvae 281 0.5 0 (12m-N) 6.0 - N _ (9m-N) E 8.0 - 0.5 4.0 - L (6m-N) Sj 8.0 Q 0.5 3.0 6.0 J (3m-N) 0.5 2.0 (l.5m-N) 0.5 • i ■ i • » ' » • I I > l I I I \ i I 50 100 150 NO. LARVAE/ 1000 m* 200 250 fig. 97. Number of spottail shiner larvae per 1000 m3 for north transect openwater stations in Lake Michigan near the J. H, Campbell Plant9 eastern Lake Michigan, 13 July 1977. □ = Day ■ = Night 288 H (21m-S) G (18m-S) F (15m-S) E (I2m-S) a, lu Q D (9m-S) C (6m-S) B (3m-S) A (1.5m-S) 0.5 5.0 10.0 15.0 20.0 0.5 4.0 9.0 14.0 17.0 0.5 4.5 8.5 11.5 , 14.0 ' 0.5 3.0 6.0 9.0 11:0 0.5 2.5 4.5 6.5 8.5 - 0.5 - 2.0 - 4.0 - 5.5 0.5 2.5 0.5 20 40 60 80 NO. LARVAE/ 1000 m* fig. 98. Number of spottail shiner larvae per 1000 m3 for south transect openwater stations in Lake Michigan near the Jo H. Campbell Plant, eastern Lake Michigan, 25-28 July 1977. D = Day ■ - Night 289 V 0.5 X 0.5 CL Q 0.5 -■ 50000 100000 150000 200000 250000 300000 NO. LARVAE/ 1000 m^ 0.5 - ^ 0.5 - E a. a M 0.5 2.5 4.5 20 40 60 80 100 NO. LARVAE/ 1000 m FIG. 99. Number of spottail shiner larvae per 1000 m: for beach and openwater stations in Pigeon Lake near the J. H. Campbell Plant, eastern Lake Michigan, 25 - 28 July 1977. D - Day ■ - Night were subject to currents which drew larvae away from shore areas . Recall that a similar phenomenon, where many newly hatched spottail larvae were found in openwater while a much wider length range of larvae occurred at beach stations, was also found during June in Pigeon Lake* Presence of vegetation at beach stations may increase the efficiency of our nets there. Day-night differences in length of larvae captured was 290 also dramatic at openwater Pigeon lake samples in July. During the day, many large larvae were captured, while at night, only newly hatched larvae were collected. Apparently the longer spottails (at least some), were in surface waters during the day (possibly feeding) while at night they were either demersal in their distribution or moved inshore to littoral zone stations. Comparing Pigeon Lake pooled samples (N=3502) with Lake Michigan pooled samples for July (N=365) (Fig. 91), showed that spottails were collected in higher densities and more often in Pigeon Lake, with the length range of spottails from both habitats comparable. Spottails from Pigeon Lake, which undoubtedly were spawned, earlier than Lake Michigan specimens, appeared in Pigeon Lake beach seine catches in July as YOY with a modal length of 40 mm (Appendix 5)* Many other YOY 25-30 mm were also captured. In contrast, Lake Michigan seine catches in July contained very few individuals that were 20-40 mm. Large numbers of YOY from Lake Michigan seine catches were present in the 30 and 40 mm length interval during August, almost a month behind the YOY modal length group of spottails in Pigeon Lake, YOY distribution differences between Pigeon Lake and Lake Michigan are also discussed under JUVENILE and ADULT FISH-Spottail Shiner. Lake Michigan length-frequency data for spottail shiners caught during July (Fig. 91) showed that by this time a full length range of larvae (4.5-25 mm) was present. Breaking down the Lake Michigan stations by depth showed the predominance of spottails in the inshore (3 m, 1*5 ni and beach zone) water.. Day-caught spottails inshore ranged in length from about 4.5-25 mm with a mean of 6.2 mm (S.E. = 0.4, N = 79) , while night-caught larvae, though having a similar range, were more abundant and on the average twice as long, with a mean of 13*5 mm (S.E. 0.4, N = 263). Stations in Lake Michigan 6 to 12 m had some spottails present; but most were small, from 4.5-7 mm, suggesting that some of the main population of larval spottails were transported offshore during their early existence. A classic example of net avoidance was provided by comparing the north transect stations day catch with the night catch (Fig. 91). Sixty-two larvae (5-7 mm long) with a mean length of 5*7 nun (S.E. = <0.1) were caught during the day; at night 200 (4.5-25*4 mm long) with a mean length of 13. 1 mm (S.E. * 0.5) were collected. Sled tow length-frequency data also aptly demonstrated the inshore distribution of spottails as well as the phenomenon of net avoidance (Fig. 91). From day sled tows in Lake Michigan, 90 larvae with a mean length of 8.9 mm (S.E. = 0.4, range 4.5-18 mm) were found; at night there was a drastic shift to more and larger sizes of larvae, when 127 with a mean of about 13.5 mm (S.E. = 0.3, range 8-22 mm) were observed. During July, densities of spottail larvae in entrained water did not exceed 21 larvae/ 1000 m . Despite the wide availability of many 291 sizes of larvae in both Pigeon Lake and Lake Michigan, and a tendency for the newly hatched spottails to be planktonic and therefore susceptible to entrainment, few were entrained . Lengths of entrained larvae appeared in two distinct size groups, one in the newly hatched range around 5 mm, and another around 14 mm (Fig. 91). August collection of spottail larvae from Lake Michigan was restricted to north beach station Q where 190 larvae/ 1000 m were observed in aisled tow sample, and station I (1.5 m - n.) where 39 larvae/1000 m were observed. Lack of spottail larvae in Lake Michigan samples in August was probably due to net avoidance, as well as growth of many larvae into "fry" stage. August beach seine data from Lake Michigan (Fig. 20) as previously discussed, documented presence of many Y0Y in the 30-40 mm intervals. Pigeon Lake beach station S continued to have high densities of spottail larvae (Fig. 100) indicating its continued use as a rearing area. Lower densities of spottail larvae were observed at station V in August. During August as with all prior months, more spottail larvae were caught in Pigeon Lake (1960) than in Lake Michigan (1), despite peak abundance in Lake Michigan during July. In Pigeon Lake, another good example of net avoidance was shown with the pooled beach length-frequency samples, where during the day the distribution was skewed to the left (mean of 14.9 mm S.E. = 0.1) while at night longer larvae were caught which skewed the distribution to the right (mean of about 19*2 mm, S.E. = 0*2) (Fig. 101). Pooled sled tows in August (all larvae were caught during the day) showed a wide length range (5-22 mm) of spottails present in Lake Michigan. Entrained larvae apparently came from Pigeon Lake, as few were observed in Lake Michigan; whereas, many were found at Pigeon Lake stations. Entrained larvae in August (N = 18) ranged in length from 10-22 mm with a mean of 15.5 mm. Spottail larvae were absent from Lake Michigan samples collected during September-November, which may be attributed primarily to larval growth. Spottail fry occurrence in plankton nets was sporadic in September at Lake Michigan inshore stations (Appendix 11); none were found in October and November samples from Lake Michigan. Spottail densities of 69 larvae/1000 nr were still observed at Pigeon Lake beach station S in September at night. No larvae were observed during the day at this station (Fig. 94). This decrease in concentration compared with August was probably due to larval growth to the fry stage (2327 Y0Y spottails 30-50 mm were seined in September) (Appendix 5). No spottail larvae were found at other Pigeon Lake stations in September. Spottail larvae were also absent from all October through December Pigeon Lake samples. In general, spottail larvae were not very susceptible to 292 0.5 X 0.5 Q. U Q 0.5 1 T ' I 178,773 ZL<— a~ 1 I ' I ' I ' > ' I ' 1 ' 1 20000 40000 60000 80000 100000 120000 140000 NO. LARVAE/ 1000 m3 U a 0.5 - 0.5 - 0.5 - >!'»'» ' » ' 1 2.5 - 4.5 - 10 20 30 NO. LARVAE/ 1000 m3 40 50 FIG. 100. Number of spottail shiner larvae per 1000 m for beach and openwater stations in Pigeon Lake near the J. H. Campbell Plant, eastern Lake Michigan, 15-19 August 1977, D= Day B- Night 293 30- Ui O 20- Pigeon Lake pooled X=I5.9 (0.1) N='960 5 10 15 20 25 AUGUST Pigeon Lake beach- day X=!4.9 (O.I) N*!505 JWllL.. t0 « 20 28 Pigeon Lake beach- night X*l9.2 (0.2) N=454 ■ ..ILtilWb & 10 18 2© 25 TOTAL LENGTH (mm) Pigeon Lake openwater X» 18.5 (0.0) 100.00 10 15 20 25 SEPTEMBER 5 Lake Michigan _ sled tows X=i3.4(3.3) ■ Entrained X= 15.5(0.8) N = I8 - ii < , III I as 5 10 15 20 25 5 10 15 20 25 TOTAL LENGTH (mm) Pigeon t_ake pooled "x = 24.5 (0.0) 1 00.00 5 10 15 20 25 TOTAL LENGTH (mm) FIG., 101. . Length- frequency histogram for larval spottail shiner caught at selected pooled stations in Lake Michigan and Pigeon Lake near the J.H^ Campbell Plants 1977* All tows were net tows unless sled tows were specified . (X=means N~total number of. larvae used in the comparison, standard error is given in parenthesis . ) entrainment through the Campbell Plant. Entrainment of this species only occurred in July and August almost exclusively at-night, and all observations indicated low densities (25 larvae/1000 m ) of spottail larvae (Fig. 102). Highest concentrations of spottail larvae observed at the 6 m openwater station M in Pigeon Lake in early July night samples (213-4^1^ larvae/1000 m ) coincided with observations of only 17 larvae/1000 m in discharged water (Appendix 10) , indicating that most of the small larvae (about 6 mm) observed at station M in July were somehow avoiding the intake current. Lack of spottail larvae at station Z (intake) during all months sampled also substantiated this. Spottail shiner fry were entrained from one to five times per month during July to November in concentrations ranging from 8-19/1000 nr (Appendix 11). The reason for such low entrainment of spottail larvae and fry was probably related to the tendency of this species to be demersal during the day. Field samples indicated that this species was sometimes found in the upper strata of the water column at night. Seven of the nine occurrences of entrainment of spottail larvae and ten of twelve occurrences of fry occurred at night, indicating that this species was 29h 7,504 6,330 I I I SPOTTAIL SHINER ENTRAiNED — LARVAE (TOTAL NO ) FIG. 102. Total.. number of laryal spot tail shiner entrained during the day and night at the J. H. Campbell Plants 1977, □ = Day ■ = Night probably more vulnerable to entrainment when it entered upper water strata at night. Bluntnose Minnow — The bluntnose minnow, a likely candidate for the unknown cyprinid larvae category, was another species in the Cyprinidae complex found in Pigeon Lake. Adult bluntnose comprised about 7*5* of the total number of adult fish caught in Pigeon Lake, making them an important species numerically. Like the adults, all bluntnose larvae were taken at Pigeon Lake beach stations. In the early June sampling period, bluntnose larvae were recorded at night at beach station^T (influenced by Pigeon River) at a density of about 250 larvae/1000 nr (Fig. 103). Bluntnose larvae caught in June were quite long, from 15 to 22 mm (Fig. 104) indicating much earlier spawning, perhaps late April-early May. The bluntnose adult fish discussion corroborates this estimation* In July, bluntnose larvae were observed at beach station V (undisturbed Pigeon Lake) at night (1075/1000 m- ) and at station S (influenced by Lake Michigan) during the day; the average concentration 295 0.5 - X 0.5 - H- CL UJ a 0.5 - — | — 50 31 May - 3 June, 100 150 200 NO. LARVAE/ 1000 m3 2S0 300 V T a, 0.5 0.5 0.5 1000 25 -28 July 2000 3000 NO, LARVAE/ 1000 m 4000 5000 FIG. 103, Number of bluntnose minnow larvae per 1000 m3 for beach stations in Pigeon Lake near the J. H. Campbell Plant, eastern Lake Michigan, 1977. D = Day «s Night 296 Pigeon Lake' K 20 JUNE Stations M,X,Y,S,T,V X= 18.5 ..7) N= 3 20 10 15 20 25 Beach- day 7=15.5(0.4) N = 45 3C -M-J Ml II II M^L 8each- night X* 14.9 (0.1) N = I2 30 Stations M,X,YfS,r,V X* 15.4 (0.4) •\i -- 57 15 20 25 5 10 TOTAL LENGTH (mm) 15 20 25 -M-jw UlLlILUL 25 FIG. 104.. Length-frequency histogram for larval bluntnose minnow caught at selected pooled stations in Lake Michigan and Pigeon Lake near the J.H^ Campbell Plant, 1977 • All tows were net tows unless sled tows were specified. (X=mean, N=total number of larvae used in the comparison, standard error is given in parenthesis . ) of larvae was 4032/1000 nr(Fig. 103). Contrary to expectations, more larvae were caught during the day and approximately the same length groups (10-23 mm) were sampled both day and night at Pigeon Lake beach stations (Fig. 104). Apparently net avoidance was minimal over diel period which was certainly possible since all larvae came from beach stations in Pigeon Lake. Beach stations had maximum macrophyte density in July, which undoubtedly reduced the ability of larvae to detect a moving net. No bluntnose minnows were identified in entrainment samples (Appendix 10) . If unknown cyprinids really were bluntnose minnows as we suspect , it will be difficult to use the technique of examining larger specimens and working backwards to the unknown smaller size, because very few unknown cyprinids and no bluntnose were entrained in later months. The only cyprinids that were identified from entrainment samples, all in low abundance, were spottail and emerald shiners. Further sampling near the plant as well as more work on the cyprinid complex should solve this problem,, Golden Shiner — Golden shiner adults comprised almost 13? (2615 fish) of the total catch 'of fish from Pigeon Lake; they were the third most abundant fish collected following alewife and spottail shiner . Despite this abundance very few larvae were collected, which may of course be related to the problems of identifying cyprinids. Some percentage of the unknown 297 cyprinids were probably golden shiners. All identified golden shiner larvae were collected during June and July in Pigeon Lake at beach stations S (influenced by Lake Michigan) and T (influenced by Pigeon River) (Figc 105). Larvae captured during early June at station T ranged in length from-7o5 to 20 mm and were taken in concentrations from 85 to 651/1000 nr. During the 17-23 June period golden shiner larvae (690/1000 m ) were only captured at night at station T (Appendix 8). During the late July period, golden shiner larvae captured were still small, from 9 to 16 mm in length, and were taken exclusively at station S at night; density of larvae was 807/1000 nr '. It is obvious from these data that golden shiner larvae preferred beach zone littoral areas , as they were never collected at openwater stations in Pigeon Lake or anywhere in Lake Michigan, In addition, no identified golden shiners were entrained during July-December 1 977. Golden shiner fry were observed six times in net tows during the study. They were taken at night at station T on 23 June, 7 July, 26 July and 16 August (Appendix 11), reaffirming their occurrence at well- vegetated littoral-zone beach stations. The reason for fry being caught only at night at station T was undoubtedly related to the dense macrophytes and turbid water present at this remote section of Pigeon Lake near the confluence with the Pigeon River. Carp- Carp larvae were collected from both Lake Michigan (11) and Pigeon Lake (18) mostly in July but one was also taken in June. In addition 18 were observed in entrainment samples during Julye The 23 June specimen (7.0 mm long) was taken in a night surface sample at openwater station X (undisturbed Pigeon Lake) (Fig. 106 ). Water temperature was 18.5 C. On 7 July, five carp larvae (6.0-8.5 mm long) were collected in night surface samples at beach station V (undisturbed Pigeon Lake) (Fig. 107) giving a larval density of 657/1000 m"0 Three larvae (4,5-6,5 mm) were also taken at Pigeon Lake openwater station M (influenced by Lake Michigan). On 25-28 July, three larvae (6.5-11.0 mm) were taken in a night surface sample from Pigeon Lake beach station S (influenced by Lake Michigan), yielding a larval density of 269/1000 nr (Fig. 106). Six larvae (9.5-23.5 mm) were also collected in replicate ^ight surface samples at beach station V. Larval density was 538/1000 nr . In Lake Michigan on 7 July four carp larvae (5 . 0-6.0 mm) were collected at beach station R (n. discharge); larval density was 296/1000 m ■ (Fig. 108). On 9 July one larva was collected from each of three Lake Michigan stations: a 6 m night sample at 9 m station D (5.0 mm 298 V V 0.5 X 0.5 CL LU Q 0.5 31 May ~ 3 June « 200 400 600 8C 17-23 June 0.5 - i ' i - "i X 0.5 - h- CL Ld Q 0.5 - 200 400 600 800 V Q 200 600 400 NO. LARVAE/ 1000 m3 0.5 - 25-28 Julv 0.5 - 0.5 - I , , , , , : , , , , -, , , 800 1000 fig. 105. Number of golden shiner larvae per 1000 m3 for beach stations in Pigeon Lake near the J. H. Campbell Plant, eastern Lake Michigan, 1977. D = Day ■ = Night 299 Y M 0.5 ^ 0.5 E 0, u Q 0.5 2.5 4.5 17- -23 JUNE to 20 30 40 NO. LARVAE/ 1000 m 0.5 4 X 0.5 - u Q 0.5 25-28 JULY ■ i.i i 50 100 150 200 NO. LARVAE/ 1000 m3 250 300 FIG* 106. Number of carp larvae per 1000 m for beach and openwater stations in Pigeon Lake near the J. H. Campbell Plant, eastern Lake Michigan, 1977. n= Day ■ * Night long); a 4 m night sample at 18 m station G (6.8 mm); a 4 m sample at 6 m station L (6.0 mm) (Fig. 109). One larva (10.5 mm) was also taken during the day on 28 July at station I (1,5 m - nj (Figc 110). One carp larva (7.3 mm) was also captured during the night on 21 July in a bottom sled tow at beach station Q (s. discharge) (Appendix 9). During the apparent peak abundance of carp larvae in July, 13 300 0.5 -k X 0.5 Q. U a 0,5 200 400 600 NO. LARVAE!/ 1000 m3 800 M 0.5 ^ 0.5 - £ a, a 0.5 2.5 -j 4.5 r 20 40 60 NO. LARVAE/1000 m 80 •,oo FIG. 107. Number of carp larvae per 1000 m for beach and openwater stations in Pigeon Lake near the J„ Ho Campbell Plant, eastern Lake Michigan, 7-10 July 1977, n~ Day ■ - Night larvae were also removed from entrainment samples. These larvae were all small, from 5 to 6c5 mm (newly hatched), and were all captured at night. Water temperatures in the intake were 21, 7-23 <> 4 C„ These larvae 301 0.5 - 7 - ■ 10 July DEPTH (m) o bi 0.5 • 50 100 150 NO. LARVAE/ 1000 m 200 3* 250 300 fig. 103. Number of carp larvae per 1000 m3 for Lake Michigan beach stations near the J. H. Campbell Plant, eastern Lake Michigan, 1977. D = Day ■ = Night 3 resulted in entrainment concentrations of 35/1000 m^ on 8 July and an average density of 27/1000 m on 21 July. Carp larvae were present in both Pigeon Lake and Lake Michigan at this time, with this size range of carp present in both habitats. Origin of entrained carp is unknown. Presence of these larvae in entrainment samples may have resulted from carp spawning in the intake canal . We observed many large adult carp in the intake canal during June and July of both 1977 and 1978. Carp taken in field collections ranged from 4,5 to 23 . 5 mm with most in the 4.5-9 mm range. These fish were caught at water temperatures ranging from 11„8 to 28.0 C. Of the 47 carp larvae entrained and collected in the field only three were captured during the day, the remaining 44 were all caught at night . Predominance of night-caught larvae indicates either daytime net avoidance or demersal behavior. However only one larva out of 11 taken in Lake Michigan was observed in a sled tow, suggesting a pelagic existence for recently hatched carp larvae. We thus suspect that carp larvae actively avoided nets towed during the day. In Pigeon Lake, carp were never collected at the Pigeon River influenced stations T or X; whereas many were taken at other beach and openwater stations in Pigeon Lake, The only reason that can be advanced for the absence of carp larvae at station T is net avoidance. Carp probably spawned early in this area of Pigeon Lake, 302 3 -z, S- 03 CD 4-> C JZ cn 00 •!— E c z: o o *r- II o o ■ \ +-> lu oo < > c < 03 >> cn as 6 JZ 0*0 Hld3Q Og ■^ £ 2 2 £ d •*• « ;: V d o vo m m < O z u II D cy j*£ 03 -j r^ s- r^ cd cn +-> r— 03 S >> c r— CD rs CL1^ O 0 i- r— • O 1 <4- r*** CO „ E 03 O cn O •p- O JZ r— 0 S- S cd Q. S- C 03 s. r— ■ » CD CL 00 £- 03 03 CD U m <4- +J O C 03 i. 1— ■ n cd Cu -Q tZ r— * ^3 r-» 2: CD 03 JD -M CL 03 • E -O CTk 03 O iH O O SZ CD LUDZ (w) Hld3Q xs lu e ^£ ? 1 CD g < £ 303 0 (I2m-N) 0.5 - 3.0 - 6,0 9.0 - 11.0 - 0.5 2.5 N (9m-N) t 4.5 X 6.5 h- CL UJ 8.5 Q 0.5 2.0 L (6m-N) 4.0 5.5 J (3m-N) (1.5m-N) 0,5 H 2*5 0.5 „J 10 20 30 — } 40 NO. LARVAE/ 1000 m* :FI<5.0 110. Number of carp larvae per 1000 m3 for north transect openwater stations in Lake Michigan near the J, H. Campbell Plants eastern Lake Michigan, 25-28 July 1977. □= Day ■» Night 30U allowing carp larvae there to grow to a size which was not vulnerable to our larvae sampling gear. Support for this hypothesis was a 30 mm YOY carp captured at night during July in a seine haul at station T (Appendix 4). Carp spawning begins in spring and early summer when water temperatures reach at least 17 C and may continue for several weeks. Swee and McCrimmon (1966) believe spawning may extend from May to August in the Great Lakes. Carp move into vegetated shallow water to spawn. Eggs become attached to submerged vegetation and hatch within 3-6 days (Scott and Crossman 1973). Fish (1932) reported that early larvae of carp were large (9-10 mm long); newly hatched larvae measured 5.0-5»5 mm (McCrimmon 1968). The relatively small size of larvae collected from June through July at Campbell suggested that spawning was occurring throughout this time. Jude et al. (1975) found that carp did not spawn during 1973 in the vicinity of the Cook Plant but data collected in later years showed that spawning around the discharge occurred regularly, especially in July. Few ripe carp were taken in Lake Michigan, near the Campbell Plant or from Pigeon Lake. Pigeon Lake, however, has areas of dense vegetation which would provide suitable spawning habitat for carp. McCrimmon (1968) found that by the time carp larvae reached 8.0 mm, they were free-swimming and moved about the area. It is likely that larvae found in Lake Michigan samples were hatched in the area around the thermal discharge or in the discharge canal since conditions there, warm flowing water and abundant habitat, are ideal for spawning. In fact in early July 1978 we observed carp spawning throughout the discharge canal. The small number of carp larvae collected from Pigeon Lake as well as the small number of ripe adults captured during 1977 suggests that only limited spawning may have occurred there. Emerald Shiner Fry — Two emerald shiner fry (32.5 and 35.0 mm) were collected on 7 July in a night fish larvae surface tow at Pigeon Lake beach station S (influenced by Lake Michigan). One fry (32.5 mm) was also entrained on 28 November. Emerald shiners reportedly spawn from June through August in Lake Erie (Flittner 1964) and in Lewis and Clark Lake, South Dakota (Fuchs 1967). Spawning takes place inshore over clean sand, hard mud bottoms and over shoal areas (Flittner 1964). Fry collected in Pigeon Lake during July were probably spawned at the very beginning of the 1977 spawning season to have achieved 32-35 mm by the first week of July. The fry entrained in November was a YOY probably hatched later in the spring. Appearance of emerald shiner fry 305 at station S also raises the possibility that some unknown cyprinids collected here and at other stations, could have been emerald shiners. However since only four adults were collected (three in Pigeon Lake, one in Lake Michigan) and low numbers of fry were observed (three), abundance of larval emerald shiners must be low. Unknown Cyprinidae — Minnows which could not be identified with certainty to the genus or species level were tentatively categorized as unknown cyprinids. As a result, larvae in this taxonomic category in many cases were the most numerous larvae noted at a station and along with alewife comprised the majority of larvae entrained at the Campbell Plant. In Pigeon Lake, unknown cyprinids were abundant (3155 larvae/1000 m ) during the 31 May-3 June sampling period in night tows at beach station T (influenced by Pigeon River) (Fig, 111 and Appendix 8). Fewer (93/1000 m ) were caught during the day at this station, which marked the only time unknown cyprinid larvae were captured during daytime at any station during the early June period. These cyprinids were also abundant at beach station S (influenced by Lake Michigan) (1611 larvae/1000 m ) at night. Lesser numbers were observed exclusively at night at beach station V, openwater stations X, M and Y and in the intake canal at station Z (Fig, 111). Larvae were caught during the day only at the most turbid station (T) where net avoidance would be minimal. Specimens at all other stations were caught at night. This pattern indicated that these larvae were either demersal (unlikely since some were caught during the day in surface tows) or that they actively avoided plankton nets. Since adult bluntnose minnows were thought to have spawned in late May and bluntnose larvae were identified from some stations, most unknown cyprinid larvae were thought to be bluntnose minnows . More support for this contention was that spottails, the only other abundant larvae, were easy to separate from bluntnose minnows. Pigeon Lake results for unknown cyprinids during the 17-23 June sampling period (Fig. 112) were similar to those observed in the early Jude period. -Again, larvae were taken during the day in low numbers (13-90/1000 m ) at beach station T and station Z (intake canal) . Largest concentrations were observed at night at^station T (919/1000 nr), but some larvae (up to. 340/1000 m ) were collected at beach stations V and S and openwater stations X and Mc The only occurrence of unknown cyprinids in Lake Michigan during June was at the 3 m station B, south transect (Fig„ 113) and beach station R near the present discharge (Fig. 114). Concentration of larvae at these stations ranged from 0-146/1000 m^at night, none were 306 0.5 -B 2 0.5 - n I— UJ Q 0.5 - 1000 2000 3000 NO. LARVAE/ 1000 m3 4000 M 0.5 - ^ 0.5 £ a. UJ Q 0.5 i 2.5 4.5 50 100 150 NO. LARVAE/ 1000 m3 200 250 0.5 Q 20 40 60 NO. uARVAE/1000 m 80 fig. ill. Number of unidentified cyprinid larvae per 1000 m3 for beach, openwater and intake canal stations in Pigeon Lake near the J. H. Campbell Plant, eastern Lake Michigan, 31 May - 3 June 1977, □ = Day ■ = Night 307 jE °-5 CL UJ Q 0.5 0.5 0.5 - CL U Q 0.5 2.5 4.5 - 200 400 600 800 1000 NO. LARVAE/ 1000 m 20 40 60 80 100 NO. LARVAE/ 1000 m w 0.5 X Q 10 15 NO. LARVAE/ 1000 m3 20 25 fig. 112. Number of unidentified cyprinid larvae per 1000 m3-for beach* openwater and intake canal stations in Pigeon Lake near the J, H. Campbell Plant, eastern Lake Michigan, 17-23 June 1977. Q = Day ■ s Night 308 0.5 5.0 H (21m-S) 10,0 15.0 20.0 0.5 4.0 G (18m-S) 9.0 14.0 17.0 F (15m-S) 0.5 4.5 - 8.5 - 11.5 14.0 H E (12m-S) CL LU a D (9m-S) C (6m-S) B (3m-S) A (1.5m-S) 0.5 - 3.0 - 6.0 9.0 - 11.0 - 0.5 2.5 4.5 6.5 - 8.5 - 0.5 - 2.0 - 4.0 - 5.5 0,5 i 2.5 0.5 H — r— 20 40 60 — r— 80 100 NO. LARVAE/ 1000 m* fig. 113. Number of unidentified cyprinid larvae per 1000 m3 for south transect openwater stations in Lake Michigan near the J. H. Campbell Plant, eastern Lake Michigan, 17-23 June 1977. D = Day ■= Night 309 Q 0.5 - 3! May - - 3 June DEPTH (m) o 0.5 • i • " J v 1 40 80 120 160 0.5 Q X 0.5 CL Ld a 0o5 1000 i 0 July 2000 3000 4000 LI I .I I HI I » I I II U I t 'I ■ If j I II | 5000 6000 Q 0.5 X 0.5 a, UJ a 0.5 - 3 July -T— r ' i NO DATA i i ■ i — j — 'i — '" » — '■■*' ' ' ' i — s — « ■ ' * NO DATA 200 400 600 NO. LARVAE/ 1000 m* 800 1000 fig. 114. Number of unidentified cyprinid larvae per 1000 m3 for Lake Michigan beach stations near the J. H. Campbell Plant, eastern Lake Michigan, 1977. D= Day ■ = Night 310 collected in Lake Michigan during the day. These larvae were undoubtedly spottail shiners because (1) spottail adults were the only abundant cyprinid in this area of Lake Michigan, (2) this time (1-23 June) coincided with appearance of spottail larvae at other nearby Lake Michigan areas (Cook Plant), (3) the strongly demersal distribution of spottails in inshore waters (3 m of water or less) (Jude et al. 1975), and (4) spottail larvae were present at some stations during this period. A large size range of larvae, from about 4 to 17 mm, was present at Pigeon Lake stations during June (Fig. 115). Spawning by adults of these larvae (thought to be bluntnose minnows) apparently was confirmed for mid to late May. Net avoidance was also quite apparent from these data, since larvae caught during the day at all beach stations were small (about 6 mm) while night-caught specimens ranged in length from 4-17 mm (Fig. 115). Larvae caught at night at Pigeon Lake openwater stations were 5-10 mm long; none were caught during the day. In June Lake Michigan pooled length-frequency samples of unknown cyprinids, thought to be spottail shiners, showed that larvae there were in the 5-6 mm range (Fig. 115). The length range of larvae caught at Pigeon Lake station M (Lake Michigan influenced) and in the intake canal (Z) was also 5-7 mm, raising the possibility of transport of larvae from Lake Michigan, through Pigeon Lake and into the intake canal. During both July sampling periods (7-10 and 25-28) distribution of unknown cyprinids at Pigeon Lake stations remained essentially the same as in June (Figs. 116, 117). However, numbers at night were much lower at station T while numbers collected at beach station S (Lake Michigan influenced) rose sharply from June levels of 340-1611 to 7058-8775/1000 m in July. During the day in July, small numbers of larvae were collected at stations M, S, T, V, and Y (7 - 182 larvae/1000 m3)0 The range of sizes of cyprinids was larger for all Pigeon Lake samples pooled than the range observed at stations M (6 m) and Z (intake canal) where only smaller larvae were- collected (Fig, 118). The wider range of larvae being available at Pigeon Lake stations not influenced by Lake Michigan may be related to: (1) earlier spawning in Pigeon Lake, and therefore availability of larger cyprinid larvae, and (2) greater catchability of larvae because of the more turbid waters at beach stations compared with openwater station M and the intake canal, station Z. It may also be that only the smaller larvae are found in openwater, being transported more widely by currents due to their inability to resist them. Of the three sampling surveys conducted in Lake Michigan, two included- all stations on 7-10 and 25-28 July, while one survey trip included only north transect stations with samples collected at surface, mid-depth and bottom. These data were collected by Consumers Power 311 2 UJ CL pigeon . ake Stations MtX,Y,S,T,V 40 * 50.00] JUNE [50.00 30- Pigeon Lake Beach- day 20- X^ 5.8 (0.3) N=2 »• 66.67 Lake Michigan pooled X = 5.3 (0.3) N=3 10 15 20 25 Pigeon Lake ,rt Beach- night Jy X=7.8(0.4) 20' N*62 10- ,ll I . 40-^ i i 10 tt 20 ioaoo 25 < » 30- Pigeon Lake station M 20- X*5(0.0) N«5 10- "20 10- 5 10 1S 20 25 TOTAL LENGTH (mm) Pigeon Latte Openwaier- night X* 6.5 (0.3) N=20 5 10 15 20 25 Intake Canal X= 5.8(0.4) N=6 20 FIG* 115. Length- frequency histogram for unidentified cyprinid larvae caught at selected pooled stations in Lake Michigan and Pigeon Lake near the Je He Campbell^ Plant , 1977 . All tows were net tows unless sled tows were specified. (X=mean, U=total number of larvae used in the comparison, standard error is given in parenthesis . ) Company personnel on 13 July. Data from the first survey on 7-10 July (Fig. 119) showed high numbers, 3525/1000 nr , of unknown cyprinids (undoubtedly spottails) at night at the 1.5 m, south transect station A and 3582-5245/1000 nr at beach stations R (n. discharge) and P (s. reference) (Fig. 114). None were caught at 1.5 or 3 m stations at the north transect. A few larvae were also observed at south transect stations G (18 m), E (12 m) , D (9 m) , C (6 m) and B (3 m) . At the north transect during early July the only occurrence of unknown cyprinids at openwater stations was in a day sample-collected at station L (6 m) at the 5o5 m depth— few larvae, 18/1000 m, were found. Samples collected on 13 July at the north transect only (Fig„ 120) 312 0.5 . M X 0.5 h- CL UJ Q 0.5 -k 0.5 - Q- Q 0.5 - 2.5 - 4.5 2000 4000 6000 8O00 NO. LARVAE/ 1000 m 200 400 600 800 1000 NO. LARVAE/ 1000 m w 0.5 -\ X P4 2.5 200 400 600 NO. LARVAE/ 1000 m 800 3 1000 1200 FIG. 116. Number of unidentified cyprinid larvae per 1000 m3 for beach, openwater and intake canal stations in Pigeon Lake near the J. H. Campbell Plant, eastern Lake Michigan, 7-10 July 1977. D = Day ■ = Night 313 V 0.5 • X 0.5 ^- CL U Q 0.5 2000 4000 NO. LARVAE/ 1G00 m 6000 8000 3 10000 M 0.5 - Q 0.5 2.5 4.5 J- 0.5 0- 2 5 20 40 60 80 NO. LARVAE/ 100C m 15 20 NO LARVAE/ 1000 m fig. 117 Number of unidentified cyprinid larvae per 1000 m3 for beach, openwater and intake canal stations in Pigeon Lake near the J, H. Campbell Plant, eastern Lake Michigan, 25-28 July 1977. Q ^ Day ■ = Night '31U 40 i 30 U O 20 cr u a. 10 30-, o 20H 01 CL 10- Entroinment JULY 30- 20- All samples X*5.7 (0.0) 10- N =III5 J » 1 , 10 15 20 25 Day X = 5.4(0.l) N*48 10 15 20 25 JU- | Night 20- X» 5.7 (0.0) 10- N* I067 J ■■"-"! . r— r- 10 15 20 25 30 20 10 40 30 u O 20' 10 H Entramfnent TOTAL LENGTH (mm) AUGUST X»9.7(l.3) N = 8 30 O 20 10- 10 15 20 — r* 25 TOTAL LENGTH (mm) Pigeon Lake Pooled stations M,X,Y,S,T,V Xs 7.2 (0.2) N = 33l IN * 331 10 15 20 25 Station M - 6 m JjliUlL X = 6.5 (0.3) N= 31 5 10 15 20 30- Intake Canai 20- Xs 6.0(0.2) 10- N*45 * II llL — _ , 5 10 15 20 25 Pigeon Lake Beach stations X= 13.2(0.5) N = 37 U IL 10 15 20 FIG, 118. Length- frequency histogram for unidentified cyprinid larvae caught at selected pooled stations in Lake Michigan and Pigeon Lake near the J.H. Campbell_Plant , 1977. All tows were net tows unless sled tows were specified. (X=mean, N=total number of larvae used in the comparison, standard error is given in parenthesis.) 315 (w) HL63Q Os c 03 >> CD H3 •r= a JS CJ 1! □ O) 's ^ 03 • o -J r*v> o o r-*> ■ S» \ OJ ,»=«» < 4J > 03 >> OS < — 1 £ r» C 3 CD ■""3 d a 2 o O I o P"^ If- «* co c £ 03 en o opMK o -C o u r- •r i_ OJ CD flL^i 03 cd -J rO > C £« s» fS CD ,_ 4-) -o 03 0f-=> CD c •r « i. 4-5 CL C >> 03 CJ a. "O CD r» »r= r— ■ <+- CD •r* -Q 4»> CL C s _ m CD 03 ^ E "O O 4-3 ♦ f-o 03 o o C . -o o 3 31 q« O < > o ^ II a: < s~ ^ ^ -j OS < o JZ OS >> cn 03 (J II CD J^ • 03 Pn. -J p^ cr> 03 r— S 3 C ^ c 03 CD r o o o o < > < o 2 o o in ifl in ioo o in in in in tn ~ d n t id si CO "O 03 •r- CD a. c >> 03 CJ r— Q- CD i— Of— p— . M- CD «r- jQ 4-> Q. c E CD 03 -o <-> •r- c • 3 3: O "D £- CD JD +■> E 3 i- S 03 CD +J C -C CD HCZ CN O r-4 .,- i! e +■> » O) Hid3a x g o s a i < e 319 Q 0.5 X 0.5 CL LU Q 0.5 !5 - 28 July 1 1 i 1000 2000 NO. LARVAE/ 1000 m 3000 4000 3 5000 R Q 0.5 X 0.5 - GL UJ Q 0.5 - 15 - 19 August » i 20 40 60 NO. LARVAE/ 1000 m3 . — p— 80 100 fig.. 122. Number of unidentified cyprinid larvae per 1000 m3 for Lake Michigan beach stations near the J, H. Campbell Plant, eastern Lake Michigan, 1977, D s Day ■ » Night 320 20-i 10 20-i 10- 20 10 z u o u Q-40 30- 20 10 20-i 10- Lake Michigan- JULY Pooled Lake Michigan X= 6.6(0.1) N = 433 m lljlh ul.j . , 20 ft 10 15 N. Transect Stations X= 8.0 (0.4) N=64 T 25 LlU 10 15 20 25 S. Transect Stations X= 6.I (O.i) N=2I0 iiUi^ 15 — r— 20 — r- 25 49.09 N. Transect Stations . Oay X* 5.9 (0.2) - N = 53 - ■JL, L, , r 10 15 20 25 J N. Transect Stations Night X= 7.6 (0.3) N*I63 limujili lilt} 1 1 10 15 20 25 30 20- 10- u o Id a. 20-f 10 40-, 30 20- 10- TOTAL LENGTH (mm) Pooled Lake Michigan All sled tows X* 6. 6 (O.I) N*289 M»»'»-t- ■» ■ , 5 10 15 20 25 40-] 44.44 30- Beach Sled Tows 20- X= 6.0(0.3) N= 18 10- HIJ , , , 1 <3m Sl'ed Tows j X- 6.5 (0.1) Hi N= 287 i Hi 10 15 20 25 j 50.00 >6m Sled Tows X = IL5(L5) N=2 10 -i 1 — 15 20 — j— 25 FIG. 123. Length- frequency histogram for unidentified cyprinid larvae caught at selected pooled stations in Lake Michigan and Pigeon Lake near the £ T T ▼ ▼ e, , o «o !2m X= 6.8(0.2) N=29 il 10 15 — T — 20 25 JULY 40 30 20 10 Lake Michigan Xs 5.3 (0.3) N»5 10 16 4U- 100.00 < 30- Entrained X= 5.0(0 20- N*l 10- 40 n 30- 20- 10- 5 10 15 TOTAL LENGTH (mm) 100.00 Sled Tow station Q X- 6.5 (0.01 N= I 10 15 FIG.. 126. Length- frequency histogram for larval yellow perch caught at selected pooled stations in Lake Michigan and Pigeon Lake near the J.H. Campbell Plant, 1977. All tows were net tows unless sleji tows were specified. Inshore means all stations 3m or less in depth. (X=mear.t, N-total number of larvae used in the comparison, standard error is given in parenthesis . ) 327 0.5 - X 0.5 UJ Q 0.5 500 1000 1300 NO. LARVAE/ 1000 m' 2000 3 2500 2000 a, UJ Q M 0.5 - I 0.5 - 0.5 - 2.5 - D 4>.5 - 200 400 600 800 1000 NO. LARVAE/ 1000 m fig- 127c Number of yellow perch larvae per 1000 m3 for beach and openwater stations in Pigeon Lake near the Jo H. Campbell Plant, eastern Lake Michigan9 31 May - 3 June 1977. D - Day ■ » Night similarly reported by Jude et al. (1975) during 1973 studies in southeastern Lake Michigan. At Campbell, larvae were most abundant at the 6, 9 and 12 m stations in Lake Michigan; few were taken at 3 m or depths greater than 12 m and none were caught at beach stations . Jude et al. (1975) noted a similar absence of perch at beach stations at the Cook Plant. No definite vertical distribution pattern (Fig. 127) was 328 I l! o o o < > < o Z (w) Hid3Q Os -J 6 "* E - 6 Jii-oU JUa o o o < > < o z r o o «2 o o >o m io o lO q o fw) Hld30 o c »n *> *> *} S- c CO +j C JZ o en <0 +-> ii :■ rt3 en •r- -C >> •r- Q li fl3 ?<* cd O C O ^- CO CO I £ r- o o - o c i—S CO CJ) CD jc CL O CD S« ^ fO fO o s- S» CD CD 4-> CL CO £ > fO o z~ *^> CD CD =5 e o CO 3C CM rH O CD M JZ O £ li- £ W £ C*« < s 329 Y LU O M 0o5 0.5 0.5 2.5 - 4.5 i T— — i — 1 1 n — r~ 1 r — r— i i * ' '■ r " -i t s r i t "'i i " t h 10 15 NO. LARVAE/ 1000 m 20 2 25 30 fig., 129. Number of yellow perch larvae per 1000 m3 for open- water Pigeon Lake stations near the J. H. Campbell Plant s eastern Lake Michigan, 17-23 June 1977. D * Day ■» Night evident although more were caught at the deeper strata of the 9-15 m stations during the day than at any other strata . Ability of larvae to avoid a net may decrease with depth. At night , larvae were concentrated near the surface (Jude et al. 1975). No larvae were caught in Pigeon Lake during the 17-23 June sampling period except at station M (6 m - influenced by Lake Michigan) (Fig, 129). These larvae were similar in size (6-9 mm) to those found in Lake Michigan and were thought to have been derived from there (Fig. 126). The apparent absence of yellow perch larvae in Pigeon Lake was undoubtedly due to gear avoidance and rapid growth from the larval stage. Presence of 32-40 mm fry in samples collected with plankton nets at station T supported this observation., Perch fry concentrations up to 1379/1000 m were observed at station T (Appendix 11). In Lake Michigan, yellow perch densities (17-391/1000 m ) were much lower during the 7-13 July sampling period than in late (17-23) June* Perch were collected only four times during this July period. They were collected three times along the south transect (stations H - 21 m, E - 12 m and C - 6 m) (Fig. 130) and once along the north transect at station I (1.5 m) (Fig. 131). More larvae were caught at night than during the day, and no depth stratification of larvae was apparent . The 330 H (21m -S) G (18m -S) (15m-S) E (12m -S) 0.5 i 5.0 10.0 15.0 20.0 0.5 4.0 H 9.0 14.0 - 17.0 0.5 4.5 8.5 11.5 14.0 H w 0.5 X jr 3.0 CL U ° 6.0 9.0 11.0 0.5 D (9m-S) C (6m-S) B (3m-S) A (1.5m-S) 2.5 4.5 H 6.5 8.5 0.5 2.0 4.0 5.5 0.5 2.5 0.5 -| 10 20 .30 NO. LARVAE/ 1000 rrf 4C fig. 130. Number of yellow perch larvae per 1000 m3 for south transect openwater stations in Lake Michigan near the J. H. Campbell Plant, eastern Lake Michigan, 7-10 July 1977. D = Day ■ = Night 331 0o5 (I2m-N) 6'° * N _ (9m~N) £ 8e0 0*5 - 4.0 Sj 8.0 0.5 L (6m-N) 3.0 6.0 0,5 (3m~N) (1.5m-N) 2.0 - 0.5 4 10 « — "T 20 30 NO. LARVAE/1000 m* —I 40 FiGe 131. Number of yellow perch larvae per 1000 m3 for north transect openwater stations in Lake Michigan near the J, H* Campbell Plants eastern Lake Michigan, 13 July 1977. □ = Day ■= Night 332 range of lengths of Lake Michigan perch (4.5-6.5 mm) corresponded to the range of lengths for larvae entrained at this time which clearly indicates withdrawal of Lake Michigan water by the plant. Interestingly, larvae (17/1000 m ) were found at the 21 m contour, but only in the epilimnion. No perch larvae this size (4.5 - 6.5 mm) were caught in Pigeon Lake during 7-13 July. Rapid growth of yellow perch larvae in Pigeon Lake was evident during the mid- July (7-13) sampling period. Only yellow perch fry were caught and all were collected at station T, the preferred habitat. Fry, averaging 34 mm were caught there in moderate densities at night (average 80/1000 m ) on 7-13 July. By 26 July, this cohort was 53-61 mm and was found at beach stations T and S. Yellow perch fry were only collected three more times for the remainder of the year, all in Pigeon Lake on 16 August at station V (68 mm), on 17 October at station T (70-80 mm) and on 1 November at station T (81-85 mm). About 160 yellow perch larvae were collected in Lake Michigan and Pigeon Lake. Most were taken from upper water strata, indicating their preference for surface waters during their early planktonic stage (6-8 mm). One larva, however, 6.5 mm was collected during July in a sled tow at Lake Michigan beach station Q (s. discharge). In addition to being the only yellow perch larva caught in a sled tow, it was also the only one caught at a beach station in Lake Michigan. Centrarchidae Complex Since there are seven species of centrarchids in Pigeon Lake, and early stages of these larvae are difficult to identify, we included all known species and taxonomic groups (Lepomis spp. and Pomoxis spp.) under this discussion. Among the sunfishes there are green sunfish, pumpkinseed and bluegill. The warmouth , another Lepomis adult present, if collected never were identified in the larval form. Among Pomoxis spp., there are the black crappie which we collected as adults from Pigeon Lake and the reported presence of white crappie (Consumers Power Company 1975). There are two Micropterus present, the smallmouth and largemouth bass. In addition rock bass,, Amblonlites. was also collected as adult and larva. Pumpkinseed — One pumpkinseed larva (12.1 mm) was collected at night on 26 July in a surface sample at beach station S (influenced by Lake Michigan). Water temperature was 15 * 6 C. (See unidentified Lepomis spp. for a discussion of Lepomis larvae which may include pumpkinseed). Scarcity of pumpkinseed larvae in Pigeon Lake was surprising. Adults with developed gonads were collected and the shallow vegetated 33: areas would seem to be suitable spawning habitat. If pumpkinseed do successfully spawn in Pigeon Lake, the young must reside in areas relatively protected from sampling efforts, such as near the bottom in densely vegetated areas or many of the larvae, designated Lepomis spp. , were pumpkinseed. Green Sunfish— Five green sunfish larvae (16.5-20.5 mm) were collected at night on 28 July at openwater station X (undisturbed Pigeon Lake). Larvae were collected from surface waters.. when the water temperature was 18.0 C; density was 155 larvae/1000 m , Green sunfish spawn from mid-May to early August with multiple spawning occurring (Scott and Grossman 1973). Eggs hatch in 3-5 days. Nests are built in shallow, sunlit water in areas sheltered by rocks, logs, etc. The green sunfish larvae had probably moved off the spawning grounds by the time of collection and into the deeper water of station X, a phenomenon noted by Faber (1967) for sunfish larvae. Some of the Lepomis spp. larvae may have been green sunfish. Largemouth Bass — Largemouth bass are one of the important predaceous sport fish found in Pigeon Lake. Adults comprised almost 4? (760 fish) of the total number of fish captured in Pigeon Lake (Table 14) . None were taken in Lake Michigan. Twenty larval bass were collected during the study, all in Pigeon Lake, and almost all at beach station T (influenced by Pigeon River) in the remote section of Pigeon Lake (Fig.f 132). One was also captured at openwater station X (undisturbed Pigeon Lake). Larval bass were taken in the first series of samples collected on 1 June in both dav and night samples at beach station T (day-558/1000 nr5; night-598/1000 nr) (Fig. 132 and Appendix 8). Length range of these fish was 11-25 mm, indicating spawning had occurred at least 2 wks prior to our sampling, sometime in-mid-May. On 23 June bass were again recorded in both day (268/1000 m3) and night (459/1000 nr) samples at station T. Lengths of larval bass at this time were 11-24 mm. The last sampling period in July, also recorded the presence of largemouth bass, again at station T at night in a density of 260/1000 m . Only one larva 11.4 mm was collected . Three largemouth bass fry (25 . 5, 27 . 2 and 31.0 mm) were also observed at this station in late July. The final collection of bass occurred during the day on 17 October at openwater station X when one specimen 20.5 mm long was collected; density was 25/1000 nr (Fig. 133). A 49.5 mm fry (Appendix 11) was collected on 18 October from a day sample at station T* 33U V V 0.5 - jE 0.5 CL UJ o 0.5 - CL UJ Q 100 100 31 May - 3 J une » i" — 200 300 400 200 300 500 400 600 0.5 - 17 - - 23 June 0.5 - ) 0.5 - ' ' i ■ 1 — ! 1 » » \ i i 500 V CL UJ Q 0.5 - 0.5 0.5 - 25 - - 28 July 1 , , i r- 1 1 -i 1 f 1 r 1 50 100 150 NO. LARVAE/ 1000 m 200 3 250 300 fig. 132. Number of largemouth bass larvae per 1000 m3 for beach stations in Pigeon Lake near the J. H. Campbell Plant, eastern Lake Michigan, i 977. □ = Day ■= Night 335 Y 0.5 0.5 UJ Q 0.5 - M 2.5 4.5 - 10 15 NO. LARVAE/ 1000 m 20 3 25 30 fig. 133. Number of largemouth bass larvae per 1000 m3 for open- water Pigeon Lake stations near the J. H. Campbell Plant, eastern Lake Michigan, 17-20 October 1977. □ * Day ■ = Night Largemouth bass spawned sometime in May in Pigeon Lake and their larvae preferred the habitat represented by beach station T. This area is near the entry of Pigeon River with Pigeon Lake and was heavily vegetated and very turbid. This area is also highly productive and should be an ideal nursery for larval largemouth bass. Larval bass did not seem to move much from that area of the lake as most were caught there throughout the season 0 None were ever entrained. However, larvae captured were relatively large (greater than 11 mm); most other species of larvae entrained were considerably smaller, 5-8 mm0 Smallmouth Bass- One smallmouth bass larva (10 mm ) was collected in a night surface sample on 26 July at Pigeon Lake beach station S (influenced by Lake Michigan) . The following information from Scott and Grossman (1973) suggested that smallmouth spawned in late June-early July in Pigeon Lake. Smallmouth bass spawn from late May to early July over a period of 6 to 10 days, Mests are built near rocks or logs for protection and occasionally near dense vegetation. Four to 10 days later larvae 5,6-5.9 mm hatch. Within 12 days larvae grow from 8C7 to 9.9 mm and rise from the bottom into the water column. The only large adult smallmouth captured was taken in a seine haul at night during June at beach station T (influenced by Pigeon River), However, absence of adult smallmouth from seine catches at beach station S, where the larva was 336 collected, does not preclude their presence, as water at station S was much clearer than at station T and net avoidance by large smallmouth would be expected there. Rock Bass — Rock bass were one of the less abundant adult fish collected in Pigeon Lake. We captured nine rock bass larvae during June and July at beach station T (influenced by Pigeon River) and openwater station X (2 m). In June eight rock bass (5-17.5 mm long) were obtained from station T. Larvae.were taken in day surface samples on 1 June at a cjensity of 186/1000 m , while at night densities were 342 larvae/1000 m". On 23 June day surface samples at station T contained 179 larvae/ 1000 m . On. 28 July a single rock bass larva (24 mm long) was obtained from a . surface sample at station X, resulting in a density of 31 fry/1000 m . Water temperature was 18.0 C. Rock bass spawn in late spring and early summer in areas ranging from swamps to gravel shoals (Scott and Grossman 1973). This species spawns in May and June in weedy places along lake shores (Fish 1932) . Beach station T (influenced by Pigeon River), being shallow and weedy, would appear to be a suitable spawning area for rock bass. Young rock bass are littoral to limnetic in habit which explains their occurrence at openwater station X in Pigeon Lake. Black Crappie— Black crappie larvae were only collected from day surface samples on 23 June at beach station T (influenced by Pigeon River). Water temperature was 24.4 C and larval density was 89 larvae/ 1000 m . More information on black crappie larvae, can be found under Pomoxis spp., as most larvae with this designation are believed to be black crappies. Black crappies spawn from late May to early July, beginning when water temperature is 19-20 C. Nests are built in water from 25-60 cm deep on a sand, gravel or mud bottom with some vegetation. Sometimes nests are built near undercut banks. Eggs hatch in 3-5 days (Scott and Grossman 1973). The vegetation, shallow water, and protective obstructions at station T would provide good spawning habitat for black crappies. Unidentified Lepomis spp. — Lepomis spp. larvae (21) were collected in surface samples throughout the summer and once in October from stations in Pigeon Lake (S, T, V, Z) and beach station Q in Lake Michigan. One larva was entrained in August. Presence of very small larvae through August suggested that spawning of Lepomis spp. occurred throughout the summer. 33T Length ranges in June, July and August were 5-11 mm, 8-14 mm and 4*5-19.9 mm, respectively. Based upon adult fish collections the unidentified larvae were most likely either pumpkinseed or bluegill. Lack of suitable spawning habitat in Lake Michigan strongly indicated that all Lepomis larvae originated from Pigeon Lake or more likely the discharge canal. Unidentified Lepomis larvae were first caught on 23 June in day samples from beach station T (influenced by Pigeon River) and the intake canal (station Z). Concentrations at these stations were 358 and 25 larvae/ 1000 m respectively. On 7 July, larvae (48/1000 nr) were collected at Lake Michigan beach station Q (s„ discharge) at night . All other Lepomis larvae captured in July were collected in night samples from Pigeon Lake beach stations S (179/1000 nr) and V (89/1000 nr). Larvae were caught in day and night samples on 13 August at beach., station V; concentrations ranged from 89 to 610 larvae per 1000 nT . No unidentified Lepomis larvae were caught in September, but a single larva (22.5 mm long) was captured on 17 October at openwater station X - (undisturbed Pigeon Lake), resulting in a density of 26 larvae/1000 m . The only recorded entrainment of Lepomis larvae occurred in August at very low concentrations (2/1000 m ). In general we found very little entrainment of species endemic to Pigeon Lake, except for bluntnose minnows . Four species of Lepomis are known from the areas pumpkinseed, green sunfish, bluegill and warmouth (present but rare). These four species of Lepomis coexist in the littoral zone of many lakes (Werner and Hall 1976) and have similar spawning times and habitats (Scott and Grossman 1973). Therefore, our unidentified Lepomis larvae may represent any or all of the above species . Unidentified Pomoxis sppc< — Two species of the genus Pomoxis may inhabit the study area, but we have captured only black crappie near the Campbell plant. Previous workers have observed white crappie in impingement samples. Pomoxis larvae were taken only in June and Julyc All field-caught larvae were captured at Pigeon Lake stations, except for a single (11 m) larva taken in a night surface tow at Lake Michigan station C (6 m -■ s.) (Fig. 134). This larva had probably originated in the discharge canal, as many adult and larval species have been observed there during 1978. Pomoxis larvae were widely dispersed in Pigeon Lake on 1 June, Highest concentrations were observed at beach station T in both day (8751/1000 m5) and night (8288/1000 m5) samples (Appendix 8) (Fig. 135). Lower concentrations were found at openwater station X and the intake canal (Fig. 135). These larvae ranged from 4 to 17 mm (Fig. 136), which suggested that spawning began in late May. 338 H (21m-S) G (18m-S) F (15m-S) E (12m-S) 0.5 5.0 10.0 15.0 20.0 0.5 4.0 9.0 H 14.0 17.0 0.5 4.5 8.5 H 11.5 , 14.0 4 CL Q 0.5 3.0 6.0 9.0 - 11.0 - D (9m-S) c (6m-S) B (3m-S) A (l.5m-S) 0.5 2.5 4.5 H 6.5 8.5 0.5 - 2-0 - 4.0 - 5.5 - 0.5 2.5 - 0.5 - 10 — r- 15 NO. LARVAE/ 1000 m 20 3 25 — i 30 fig. 134. Number of PomoxZ6 sp. larvae per 1000 m3 for south transect openwater stations in Lake Michigan near the Jo H. Campbell Plant, eastern Lake Michigan, 31 May - 3 June 1977. □ = Day M = Night 339 V M 0.5 - X 0.5 CL a 0.5 a 0.5 0.5 0.5 2.5 4.5 £o.5 Q 2000 4000 6000 3000 10000 NO. LARVAE/ 1000 m 200 400 600 NO. LARVAE/ 1000 m 10 20 30 NO. LARVAE/ 100C m 800 40 FlGe 135. Number of VomoxAA sp. larvae per 1000 m3 for beach, openwater and intake canal stations in Pigeon Lake near the J. H, Campbell Plants eastern Lake Michigan, 31 May - 3 June 1977. D - Day ■ = Night 3^0 JUNE -Pigeon Lake 30 -i Z UJ 20- O T=6.4(0.l) N = 23 L 40 -i 30- Lake Michigan day 7=6.5(0.2) 20- N*H7 10- | i II 40-i so.o y Lake Michigan 30- night X* 6.2(0.2) N*6 20- 10" 20 25 5 TOTAL LENGTH (mm) 26- I00.0i iqeon Lake I pooled X=23(0.0) -juuy. AUGUST SEPTEMBER Z 30 0- 20 Lake Michigan poolea X*20.5(2 N=2 20 25 X*23.5 (1.5 J N*2 lyo.d *0 -j Entrained 7*23.1 (0.3) N«4 > X* 25.0 (0.0) 15 20 25 5 TOTAL LENGTH (mm) FIG* 138. Length-frequency histogram for larval rainbow smelt caught at selected pooled stations in Lake Michigan and Pigeon Lake near the J.H. Campbell Plants 1977. All tows were net tows unless sled tows were specified, (X=mean, N=total number of larvae used in the comparison, standard error is given in parenthesis.) sampled in June was probably produced by a relatively small fraction of the spawning population in late May. An earlier, more intense spawning period was indicated by high numbers of YOY, 25-45 mm, which were trawled in late July. Growth data summarized by Scott and Grossman (1973) suggested these larvae were about 2 months old. Given this premise, absence of larger smelt larvae in June must be due to either net avoidance by larger larvae or immigration of Y0Y into the trawling depths during July Only two additional occurrences of smelt larvae from July to November were observed at Lake Michigan stations. A density of 103 larvae/ 1000 nr was observed at station 0 (12 m -n.) in late July, 3kk 0 (12m-N) 0.5 3.0 H 6.0 9.0 - 11.0 - 0.5 2.5 N (9m-N) X I— CL UJ Q 4.5 6.5 8.5 0.5 L (6m-N) 2.0 4.0 5.5 J (3m-N) (1.5m-N) 0.5 2.5 A 0.5 -f r 20 — j— 40 ~ I 60 NO. LARVAE/ 1000 m 80 3 100 120 fig. 139. Number of rainbow smelt larvae per 1000 m3 for north transect openwater stations in Lake Michigan near the J. H. Campbell Plant, eastern Lake Michigan, 25-28 July 1977. □= Day ■» Night 3U5 Y x \- CL U Q M 0.5 - 0.5 0.5 - 2.5 4.5 10 20 30 40 50 NO. LARVAE/ 1000 m* FIG. 140. Number of rainbow smelt larvae per 1000 m3 for open- water Pigeon Lake stations near the J. H. Campbell Plant, eastern Lake Michigan, 17-23- June 1977. □= Day -■ - Night and a concentration of 30 larvae/ 1000 m was observed in a sled tow sample at the same station in September. The two larvae observed in July at station 0 (12 m - n.) were 17 and 23 mm (Fig. 139), and probably hatched from eggs laid in early May. The one larva captured in a September sled tow was 25 mm, and was probably part of the smelt cohort spawned in late May. The extent to which Pigeon River and Pigeon Lake were used by smelt for spawning cannot be determined using 1977 data. The only occurrence of smelt larvae in Pigeon Lake during 1977 was late June at 6 m openwater station M (influenced by Lake Michigan) when 42 larvae/1000 m3 were observed at the 4 m depth at night. The 23 mm larva in this sample (Fig. 140), probably hatched in May possibly in Pigeon Lake. In general, absence of smelt larvae in early June from Pigeon Lake, as well as lack of suitable spawning habitat gives initial indication that Pigeon Lake was not used for spawning by smelt. Data from 1978 may clarify this question. Our data showed that growth of smelt larvae into the fry stage occurred primarily during August, when increased densities of fry were noted at most Lake Michigan stations (Appendix 11). No smelt fry were collected from Pigeon Lake in August. Most fry were captured at night; lack of fry in day samples was undoubtedly due to net avoidance. 3U6 In September, smelt fry were collected sporadically only at night in Lake Michigan (Appendix 11). Smelt fry were not caught in Lake Michigan during October which coincided with a decreased catch of adult smelt during this month (Appendix 11). Smelt probably moved from the area to deeper water at this time. Smelt fry were observed in low densities at Pigeon Lake openwater station M (6 m-influenced by Lake Michigan) and intake canal station Z where 26 and 32 fry/ 1000 ra respectively were collected during October. Entrainment of smelt larvae by the Campbell Plant was low during 1977 sampling, not exceeding 2500 larvae/24 hr period during July-December (Fig. 141). Most larval entrainment occurred at night. This trend was similar to that of spottail shiner larvae and reflects an apparent increased vulnerability of fish larvae when they were found to migrate to surface water strata. All smelt larvae entrained exceeded 20 mm in length (Fig. 138). Although 1977 sampling indicated low entrainment of smelt larvae, we expect increased entrainment immediately following the spring spawning season. Entrainment of smelt fry generally exceeded entrainment of larvae from 3 August to 21 November (Fig. 141). High numbers of smelt fry in entrainment samples in late summer, up to 40000/24 hr period, were probably due to immigration of fry from other areas into the influence of the intakes. Most entrainment occurred during the night hours with the exception of 1 and 8 September when entrainment during daylight hours exceeded nighttime entrainment. Entrainment of smelt fry after 8 September was sporadic with values ranging from zero to over 10,000 larvae entrained in a 24-hr period in early October. Johnny Darter Eight johnny darter larvae were collected during 1977; all were taken during early June in Pigeon Lake; seven at beach station T (influenced by Pigeon River) and one at beach station V (undisturbed Pigeon Lake)(Fig. 142). All larvae were collected at night from surface waters where water temperatures were 16.6 and 14.0 C, respectively. Replicate tows at station T at night revealed larval densities of . 171-1026 larvae/ 10Q0 m. Larval density at station V was 79 individuals/ 1000 m . Spawning by johnny darter takes place in spring with local conditions determining the exact time (Scott and Crossman 1973) « Spawning occurs during May and June in southern Michigan (Winn 1958b), southeastern Lake Michigan (Jude et al. 1975) and Lake Erie (Fish 1932). Hatching time ranges from 5-8 days at temperatures of 22-24 C (Scott and Crossman 1973) with newly hatched larvae measuring 5*0 mm total length (Fish 1932). Larval lengths from beach stations T and V ranged from 12.5 to 22.5 mm indicating spawning had occurred sometime 34? : § 6 26,250 33,076 I 0 n RAINBOW 3MELr ENTRAINED — FRY (TOTAL NO.) RAINBOW SMELT ENTRAINEC CARVAE (TOTAL NO.) FIG. 141. Total number of larval rainbow smelt entrained during the day and night at the J.H. Campbell Plant, 1977. 3^8 V 0.5 £ X 0.5 - a 0.5 - 100 200 300 NO. LARVAE/ 1000 m 400 3 500 600 FIG. 142. Number of johnny darter larvae per 1000 m3 for beach stations in Pigeon Lake near the J. H. Campbell Plant, eastern Lake Michigan, 31 May - 3 June 1977. □ = Day ■ = Night prior to 1-2 June near the Campbell Plant. Johnny darters inhabit a wide range of aquatic habitats, but are usually found in inshore waters of moderate or no current (Scott and Grossman 1973)* They spawn in areas having large rocks, logs or other objects under which they can deposit eggs (Winn 1958b) . Beach station T (influenced by Pigeon River), with shallow water and large obstructions present satisfies these requirements. Four unidentified Etheostoma larvae were collected, all in night surface samples. On 1 June 1977 one (9.5 mm total length) was taken at Pigeon Lake beach station S (influenced by Lake Michigan) at a temperature of 11.0 C. On 2 June two (12.0 and 12.5 mm) were collected at openwater station X (undisturbed Pigeon Lake) at 10.3 C One Etheostoma spp. larva (7*0 mm) was also entrained in July. Brook Silverside Fewer brook silverside larvae were collected (total of 22) than was expected, considering adults were the 11th most abundant adult fish captured in Pigeon Lake. Ten larvae, with a length range of 4.5 to 18.5 mm, were observed in June at beach stations T (influenced by Pigeon River) and V (undisturbed Pigeon Lake). Twelve were collected in July at station T; lengths ranged from 9-15.1 mm (Fig. 143). Silversides showed their preference for the weedy, somewhat more turbid, remote section of Pigeon Lake. Samples from beach station V (undisturbed Pigeon Lake) at night on 23 June at the surface (20.0 C) 3^9 V V 0.5 X 0.5 Q. UJ a QJ5 - 0.5 X 0.5 H a. UJ a 0.5 - 0.5 - X 0.5 CL UJ a 0.5 - 31 Mav - 3 June 200 400 17 - 23 June 600 ? 50 ii 100 I 150 i \ 200 250 7 - 10 July i ' r -i " — r 1 r — - 1 < i — 200 400 600 NO. LARVAE/ 1000 m 800 300 i i > 1 > ; i f t i 800 1000 1200 1400 3 FIG, 143. Number of brook silverside larvae per 1000 m3 for beach stations in Pigeon Lake near the J. H. Campbell Plant, eastern Lake Michigan, 1977, □ = Day ■ - Night 350 contained 266 larvae/ 1000 m . This station also contained considerable amounts of vegetation* None were collected at the somewhat less vegetated, sand-bottom station S (influenced by Lake Michigan) . At station T on 1 June larval densities of 651/1000 nr were found in day surface samples when the water temperature was 12.0 C. Night surface samples (16.6 C) showed a mean density of 171 larvae/1000 m . The July sample was taken from surface waters at 16.6 C at station T during the day and showed 1254 larvae/ 1000 m — a high concentration of larvae (Fig* 143). Scott and Crossman (1973) reported that spawning by brook silversides occurred in spring and early summer. In a northern Indiana lake, spawning extended from 17 June to 5 August (Nelson 1968a). Silversides prefer to spawn in and around aquatic vegetation, although they may spawn over gravel in moderate current (Scott and Crossman 1973). Beach stations T and V are areas of dense vegetation and would afford good spawning conditions for this species. Ninespine Stickleback Ninespine stickleback larvae (9) were all collected during June in Pigeon Lake surface tows at beach station S (influenced by Lake Michigan). They ranged in length from 9 to 20.5 mm. They were taken on 1 June during both day and night sampling. The surface day tow replicates (water temperature 11 .2 C) showed an average larval density of 281 larvae/1000 m (Appendix 8). The night tow (temperature 11.0 C) revealed a density of 537 larvae/1000 m . Reported spawning time for this species ranged from April to August (Nelson 1967, Scott and Crossman 1973) with greatest spawning activity occurring at 11-12 C (Griswold and Smith 1972). Average total length at hatching (12 C) was 5-65 mm with lengths of 5.95, 7.56 and 12.91 nim after 1, 11 and 22 days respectively (Griswold and Smith 1972). Ninespine stickleback larval lengths in June at beach station S ranged from 7.5 to 20.5 mm indicating that spawning was probably initiated sometime in late April-early May and had been occurring over a period" of weeks (see ADULT AND JUVENILE FISH - Ninespine Stickleback) . Station S, where all larvae were caught, has a fine sand bottom with sharply increasing depth. Griswold and Smith (1973) reported large concentrations of both male and female sticklebacks in beach areas with steep slopes covered with dense growths of Nitella sp. McKenzie and Keenleyside (1970) in a South Bay, Manitoulin Island, Ontario study, described spawning habitats as rocks and' gravel with no rooted plants in the nesting area. Loose mats of detritus and plant fragments were found on nearby sandy bottoms, Nelson (1967) suggested that this species moved from deep water into rooted aquatic plants to spawn in the spring and after spawning moved back into deeper water. After hatching, young fish scatter along the bottom and hide among rocks . 351 Three unidentified stickleback larvae were also collected in night samples. Two larvae (8.5 and 9*0 mm) were collected on 28 July in a surface sample at station A (1.5 m - s.) in Lake Michigan. Water temperature was 13.0 C. One additional stickleback larva (8.0 mm) was taken in July from a 2 m sample at openwater Pigeon Lake station M (influenced by Lake Michigan). Water temperature was 11.7 C. These larvae were probably ninespine stickleback because ninespines were the only adult sticklebacks collected during the study to date. Slimy Sculoin Three slimy sculpin larvae (total captured during 1977) were taken on 27 July at offshore Lake Michigan stations F (15 m - sj and H (21 m - s.). A day sample from station F, at a tow depth of 15 m and water temperature of 4.8 C, contained a single larva (12 mm). Day and night samples at station H at tow depths of 9 m and 15 m, where water temperatures were 4.1 C and 6.5 C also contained one larva in each sample, 12.5 and 19.0 mm respectively. Collection of sculpins at 9 m at the 15 m station F indicates these larvae are found off the bottom on occasion. Rottiers (1965) reported that slimy sculpin spawning in Lake Michigan began prior to 5 May in shallow water. By 23 May, almost all adult fish collected were spent. However, slimy sculpins collected from deep water had not yet spawned by 26 May. Larvae we collected were probably spawned in deep water also during May. In the Montreal River, spawning occurred at about 8 C in early May and eggs hatched after about 4 wks (Scott and Grossman 1973). Slimy sculpins spawned at depths from 17-45 fathoms with bottom types ranging from fine sand to mud (Rottiers 1965). When occupying a stream habitat, they attach their eggs to the undersides of rocks and logs. In Lake Michigan where such debris is lacking, their spawning behavior is largely unknown. However, eggs which subsequently hatched were collected by divers on intake structure riprap near the Cook Nuclear Plant, southeastern Lake Michigan (Jude et al. 1975). Fourhorn Sculoin Two fourhorn sculpin larvae (14.5 and 17.5 mm) were obtained in night samples on 18 August at station G (18 m - s.) in Lake Michigan. Water temperature was 15.1 C at 14 m and 4.7 C at 17 m where the larvae were collected. Minimum length of newly hatched larvae was 7.6 mm according to Kahn and Faber (1974), suggesting hatching sometime prior to August, probably April -May. Little is known about the breeding biology of the fourhorn sculpin because it is a deepwater species on which little work has been done. Scott and Grossman (1973) suggested spawning occurs in summer or early 352 fall. Fish (1932) reported collecting larvae of this species from the end of July to mid-August in Lake Erie. Our recent experience in identifying fourhorn sculpin from other areas, specimens in GLRFLC, as well as capture records from the Cook Plant and Campbell Plant (unpublished data) suggests strongly that spawning occurs in winter . Later, these larvae become distributed widely in inshore waters. Trout-perch Trout-perch spawn in the spring, usually in May, in many inland waters. In Lake Erie, spawning was observed from May to August (Scott and Grossman 1973) > while Magnuson and Smith (1963) found trout-perch in Red Lakes, Minnesota spawned from June through August. Trout-perch spawning in larger lakes (such as Lakes Michigan and Erie) is apparently prolonged over several months. Peak spawning periods are not evident and spawning appears to be uniformly distributed over the period. Hatching occurs within 20 days (Scott and Grossman 1973)* Although trout-perch were common in adult fish samples at the Campbell plant, only four larvae were collected. All four were taken at different times and locations. Our data suggested that spawning occurred at least from mid- June through September. A 15 mm larvae was captured in a sled tow on 21 July at Lake Michigan station F (15 m - s.) at a water temperature of 6 C. We estimated that this larvae was spawned about mid- June. One other larva captured on 21 July was a 6 mm specimen found in entrainment samples. Two larvae were also captured on 21 September in sled tows at stations J (3 m - n.) and L (6 m - n.). Lengths of these larvae were 6 and 10 mm respectively. Trout-perch larvae were usually found on the bottom and captured most frequently in sled tows. Spawning by trout-perch at both the Cook and Cambell plants appeared to be extended and intermittent. Unidentified Coregonidae One unidentified coregonid larva (13*0 mm) was taken in a day sample from the 4 m tow on 18 June at station F (15 m - s.), Lake Michigan. Water temperature was 13.5 C. We believe that this larva was a bloater, since C. hovi is one of the common adult coregonids in this vicinity. Since considerable difficulty remains in identifying the small adult coregonids, the possibility of identifying their larvae remains remote. Larval bloaters collected by Wells (1966) in southeastern Lake Michigan ranged from 8.6 to 14.9 m, which further confirms our belief that the 13 mm specimen we caught was a bloater. Wells also found that larval bloaters were most abundant in June and July and were primarily found between 73-110 m, being rare at depths shallower than 36 m. Based on Wells1 data, larval bloaters would be expected to be found in low numbers in the study area, because sampling was only conducted to 21 m. The larva captured probably hatched during 353 the mid- January to mid-March spawning season as found by Wells. These eggs probably incubated 4 months before hatching* Unidentified Ictalurus spp. One 15 mm bullhead larva was taken in a day tow in Pigeon Lake at beach station V (undisturbed Pigeon Lake) on 7 July, Water temperature was 28 C. There are five species of Ictaluridae known from Pigeon Lake: channel catfish, tadpole madtom, brown, yellow and black bullhead . The specimen we captured was definitely a bullhead species, but we were unable to ascertain the key character on the spine necessary for speciation. Among adults, brown bullhead was caught most often (120), followed by yellow bullhead (35) and black bullhead (17). Tadpole Madtom Fry One tadpole madtom (81.5 mm) was collected in a night surface sample at beach station T (influenced by Pigeon River) on 2 June* Scott and Grossman (1973) reported an age-length relationship for madtom in a lake in Minnesota that would indicate this fish to be 1-yr old. See ADULT AND JUVENILE FISH - Tadpole Madtom for information on madtoms collected and habitat requirements. Unknown Pisces There were three larvae we were unable to identify to family, two were collected from Pigeon Lake and one came from Lake Michigan. The Pigeon Lake specimens were captured at openwater station X (undisturbed Pigeon Lake) during a day tow on 2 June when water temperature was 14.8 C. Both larvae were 6 mm* The remaining identified larvae in the sample were alewife and Pomoxis spp. One unknown larva, also 6 mm, was taken from a 17 June night 3 m tow at openwater Lake Michigan station E (12 m - s.). Water temperature was only 12 «9 C. No other larvae occurred in the sample; however, yellow perch and alewife were common in other tows at station E. Damaged Larvae Damaged larvae are those larvae which could not be identified due to physical damage to the specimens. In contrast, unknown larvae (XX) were intact but could not be identified. Larvae were damaged by abrasion with the net and its contents, particularly macrophytes. Although numbers of damaged larvae were generally low, their presence biases abundance estimates for all other species. The degree of bias should be roughly proportional to the fraction of damaged larvae within a sample. Our data suggested that this bias was minimal since (1) damaged larvae numbers and concentrations were low and (2) identifiable 35^ larvae within a sample were generally dominated by one species. Hence, damaged larvae were most probably members of the dominant species found in the sample. During the early June sampling period damaged larvae were found at Pigeon Lake beach station S (influenced by Lake Michigan), openwater stations X (undisturbed Pigeon Lake) and M (influenced by Lake Michigan), in the intake canal and at Lake Michigan openwater station L (6 m - n.). Low numbers of damaged larvae, 25-93/1000 m , were observed at these stations (Figs. 144-145); most were caught at night. On 17-23 June damaged larvae occurred only at Lake Michigan openwater station D (9 m - s.) at a concentration of 22/1000 m (Fig. 146) „ In June there were five damaged larvae from Pigeon Lake (4-8 mm), two from Lake Michigan (4-8 mm) and one 7 mm specimen taken in the intake canal (Fig. 147). The low number (8) of damaged larvae collected in June and their low concentrations (less than 100/1000 m ) should not severely bias interpretations of results for other species. In July, the month of maximum abundance of larvae and macrophytes (which contributed to damaging larvae), maximum numbers of damaged larvae (143) were recorded. More were captured in Pigeon Lake (68) than in Lake Michigan (54). In addition, 12 were observed in Lake Michigan sled tows and nine were recorded from entrainment samples. In Pigeon Lake during the 7-10 July sampling period, damaged larvae were found at beach stations S and T and in the intake canal. Concentrations there ranged from 34-230/1000 m (Fig. 148). During 24-28 July damaged larvae were found at beach stations V and S, at the latter in rather high concentrations, 3136/1000 m during the 'daye In Lake Michigan, damaged larvae were observed at beach station R (n. discharge) on 7-10 July and stations R and Q (s. discharge) on 25-28 July. The highest concentration, over 1143/1000 m was observed at station Q (Fig. 149). Damaged larvae were also observed at a number of Lake Michigan south transect stations (A - 1 .5 mf B - 3 m, E - 12 m, G «• 18 m, H - 21 m) at night in concentrations ranging from about 20 to 180/1000 nr (Fig. 150). At the Lake Michigan north transect on 13 July, damaged larvae were recorded from stations I (1 .5 m) , J (3 m) , N (9 m) and 0 (12 m) in low densities, less than 60/1000 nr (Fig. 151). A wide length range of damaged larvae (3-25 mm) were captured during July (Fig. 147). In Pigeon Lake, the most abundant length group was 10 mm, with a range from 5 to 15 mm. In Lake Michigan damaged larvae (probably alewives) were generally smaller than Pigeon Lake specimens with a mean of 7.1 mm; some were 25 mm. Damaged larvae in sled tows from Lake Michigan had a length range similar to that found 355 0.5 - X 0.5 - J— CL UJ Q 0.5 0.5 0.5 - CL Q 0.5 - 2.5 4.5 -1 20 40 60 80 100 NO. LARVAE/ 1000 m 20 40 60 80 100 NO. LARVAE/ 1000 m 0.5 CL U Q 2.5 ^ 10 15 NO. LARVAE/1000 rr1 20 25 fig. 144. Number of unidentified damaged larvae per 1000 m3 for beach, openwater and intake canal stations in Pigeon Lake near the J. H. Campbell Plant, eastern Lake Michigan, 31 May - 3 June 1977. □ = Day ■ = Night 356 0 (12m-N) N (9m-N) L (6m-N) J (3m~N) (1.5m-N) 0.5 3.0 -| 6.0 9,0 - 11.0 - 0.5 2.5 -£ 6.5 a 0,5 1 2.0 4.0 5.5 0.5 2.5 0.5 - 20 40 60 — t 8C NO. LARVAE/ 1000 rrf fig. 145 o Number of unidentified damaged larvae per 1000 m3 for north transect openwater stations in Lake Michigan near the J. H. Campbell Plant, eastern Lake Michigan, 31 May - 3 June 1977. □ = Day ■ = Night 357 H (21m-S) G M8m->S) F U5m-S) h (12m-S) 0.5 5.0 - 10.0 - 15.0 - 20.0 0.5 S) 2.5 4.5 - 6.5 - 8.5 - 0.5 i 2.0 4v0 - 5.5 - 0.5 i 2.5 •0.5 10 15 20 25 NO. LARVAE/ 1000 rrT fig. 146. Number of unidentified damaged larvae per 1000 m3 for south transect openwater stations in Lake Michigan near the J* H. Campbell Plant, eastern Lake Michigan, 17-23 June 1977. □ s Day ■ s Night 358 ■JUNE cc 20- Pigeon Lake X=7.0(0.7) N = 5 5 10 15 20 25 Lake Michigan X= 5.5(1.5) N=2 T ■ ! — | 1 r= 5 10 15 20 25 TOTAL LENGTH (mm) intaKe Canal X = 7.0(0.0) N- I 10 15 20 25 JULY 30- a ?0- P*geon Lake X= 9.9(0-2) N^ 68 illl 10 15 20 25 401 30- LaKe Michigan net tows 20- X» 7.1(0.7) N*54 10- _1 plii J ,i , , Lake Michigan sled tows 30- X = 9.3(1.1) 20- N = !2 10 15 20 25 5 10 TOTAL LENGTH (mm) 15 20 25 X=9.6(2.i M=9 10 15 20 25 FIG. 147. Length- frequency histogram for unidentified damaged larvae caught at selected pooled stations in Lake Michigan and Pigeon Lake near the J.H. Campbell Plant, 1977. All tows were net tows unless sled tows were specified. (X=mean, N=total number of larvae used in the comparison, standard error is given in parenthesis.) for net-caught specimens from both Pigeon Lake and Lake Michigan, 6-16 mm. Damaged larvae constituted a small fraction of the larvae entrained and should not bias entrainment results . Only nine larvae (4-22 mm) were found damaged in entrainment samples . In August damaged larvae were collected only once at openwater station I (1.5 m - n.) (Fig* 152), where the density of larvae was 27/1000 m • These larvae were both small, about 5 mm* Overall, the low numbers and abundance of damaged larvae caught in June and August should have a negligible effect on interpretations of 359 V V 0.5 - 7 - ■ 10 July X 0.5 - Q 0.5 - _ 0.5 X 0.5 -\ h- GL Ld Q 50 100 150 200 250 NO. LARVAE/ 1000 m w 0.5 - X 7 - ■10 July °- 25 -I i 10 20 30 NO. LARVAE/ 1000 m 25 - 28 July 1000 2000 3000 NO. LARVAE/1000 m" 40 4000 FIG. 148. Number of unidentified damaged larvae per 1000 m3 at beach stations in Pigeon Lake near the Je H. Campbell Plant, eastern Lake Michigan, 1977. □ s Day ■= Night 36o R 0.5 7 - 10 July Q X 0.5 a. a 0.5 - 50 1 i iOO 150 200 250 25 - 28 July 0.5 Q X 0.5 H- Q- UJ Q 0.5 - 200 400 600 600 1000 1200 FIG. 149. Number of unidentified damaged larvae oer 1000 m3 for Lake Michigan beach stations near the J. H. Campbell Plant, eastern Lake Michigan, 1977. □= Day ■= Night results for other species. During July abundance of damaged larvae was high, but these larvae were still a small fraction of the observed larvae. Most likely, the damaged larvae in July were alewives. FISH LARVAE TOTAL LENGTfJ-ROny PEP™ RELATIONSHIP Measurements of total length and body depth were made for 245 fish larvae of nine different species (Table 58). It was hoped that at least five larvae of each species could be found for each 5 mm length interval, but limited availability of certain sizes of larvae resulted in gaps in the data (Table 59). For certain species (burbot, carp and trout-perch) length ranges did not cover the entire 25.4 mm (Table 60, Fig. 153A). However, certain calculations were made from the regression 361 H (21m -s) G (18m -s) F (15m -s) E (12m -s) D (9m-S) C (6m-S) B (3rn-S) A (1.5m-S) 0.5 - 5.0 - 10.0 - 15.0 - 20.0 - 0.5 - 4.0 - 9.0 - 14.0 - 17.0 - 0.5 - ■ • i • i » i i i 4.5 - 8.5 - 11.5 - ^ 14.0 - E w 0.5 - i . « i , < i > i DEPTH Jl iA d b 9.0 - 11.0 - 0.5 - i , . , . , , . , 2.5 - 4 5 - 6.5 - 8.5 - 0.5 - 2.0 - 4.0 - 5.5 * 0 5 - 2.5 J 0 5- ) | r | ■ t- 1 i ! * ' — 1 40 80 120 160 200 NO. LARVAE/1000 rrf FIG. 150. Number of unidentified damaged larvae. per 1000 m3 for south transect openwater stations in Lake Michigan near the J* H. Campbell Plant, eastern Lake Michigan, 7-10 July 1977. □ = Day ■= Night 362 0 (12m-N) 0.5 - 3.0 6.0 N ^ (9m-N) £ 8.0 - 0*5 4.0 - L (6m-N) & 8.0 Q 0.5 3.0 8.0 0.5 (3m-N) ZQ . i (l.5m-N) 0.5 - i i i' i i 10 20 30 NO. LARVAE/ 1000 m 40 3 50 — i 60 fig, 151. Number of unidentified damaged larvae per 1000 m3 for north transect openwater stations in Lake Michigan near the J. H. Campbell Plant, eastern Lake Michigan, 13 July 1977. □= Day ■= Night 363 0 (12m-N) 0.5 3.0 6.0 9.0 11.0 0.5 2.5 N (9m-N) X a. UJ a 4.5 6.5 8.5 0.5 L (6m~N) 2.0 4.0 5.5 (3m-N) I (1.5m-N) 0.5 2.5 - 0.5 10 15 NO. LARVAE/ 1000 m 20 3 25 — ? 30 fig. 152 . Number of unidentified damaged larvae per 1000 m3 for north transect openwater stations in Lake Michigan near the J. H, Campbell Plant, eastern Lake Michigan, 15-19 August 1977, □ = Day ■= Night 36U CO CJ x: CO co > cO C 03 60 •H a •H a) CO G O o a o CO a •H 4-» CO •H 4J CO 0) O c CO CD o H CO uO W PQ < Eh £2 o 33 CO J CJ h4 erf < p-» f H S3 m 3 CJ • O Prf ^r erf H PL, < H H O O-i CO erf W CO L3 O H PQ hJ 55 W H a CO 2 o ■"3 erf W H Q CO CO £3 H H O CJ CJ H O PQ erf ED PQ fa W W co CO CM CM CO o> CN O o co o> vO CM O CN O cr> CN ON d CD O 00 O m o CN co co CN CO CO CO CN CM d O CO o co CO LO CM CO CN 00 d S c c t4 CJ CM d s 3 r-; r* S ZJ Z3 •H 00 C P0 X C CO e CO CD a CJ X H-J s 1-3 o r-J P-. d d o o CO CO d a 3 Q e P T3 S •H O g CO S 0J iQ X "O CO C £ PQ * >s g T3 g O "»«• PQ *■ « C .u CO cu CD CJ S /-> 365 sr ?» UJ Q 2 . 1 . TROUT-PERCH LARVAE A. SPQTTAIL LARVAE 8 12 TOTAL LENGTH 16 20 8 12 16 20 TOTAL LENGTH (4 ALEWXFE LARVAE C. ♦ 3 • X CL. o 2 >- Q a 03 jS I • 0 / ! 1 i L I S COTTUS SPP. D. LARVAE «4 . . 5* a. o .. • o c . • 1 c • 0 ,..„ r. i \ I X 10 15 TOTAL LENGTH 20 25 a 12 TOTAL LENGTH 16 20 FIG«153 . Scatter plots representing three types of total length- body depth relationship results: A) insufficient data for meaningful regression; B) and C) linear relationships; D) curvilinear relationship due to yolk sac influence. 366 TABLE 59. Number of larval fish specimens per 5 mm length interval used in total length-body depth regression equations. Most larvae were from Lake Michigan. SPECIES Length Cottus Johnny Rainbow Spottail Trout- Yellow Interval (mm) Alewif e Burbot Carp spp. Darter Smelt Shiner Perch Perch. 0-5.0 11 7 1 5 7 3 2 4 5.1-10.0 17 5 11 14 10 11 24 6 21 10.1-15.0 4 1 4 1 5 5 6 2 12 15.1-20.0 6 - - 1 3 2 12 3 1 20.1-25.0 6 - - - - 4 4 - 3 TOTAL 45 13 16 16 23 29 49 13 41 equations generated by MIDAS for these species (Table 61). Alewif e, rainbow smelt , spottail shiner and yellow perch showed a linear relationship between total length and body depth with R values greater than or equal to 0.85 (Table 60, Fig. 153B and C). Cottus spp. and to a lesser extent, johnny darter showed a curvilinear total length-body depth relationship due to yolk-sac influence (Table 60, Fig. 153D). For alewif e, the most abundant larval species entrained at the Cook and Campbell Plants, 45 larvae were measured. The smallest was 2.5 mm in total length with a corresponding body depth of 0.3 mm. Since the smaller larvae of this species (and most other species) tend to be entrained at a far higher rate than larger larvae, (see Fish Larvae and Entrainment Species) it is possible that most newly hatched larvae would pass, head on, through a 0.5 mm screen. However, this does not take into consideration any avoidance ability or behavioral reaction to a screen. The largest alewif e larva measured was 25 ram with a body depth of 3.7 mm. Many alewives larger than 25 mm (unlike most other species) were entrained. The regression of body depth on total length was linear with an R value of 0.85 (Fig. 153C). Rainbow smelt larvae were probably entrained in large numbers during their peak hatching period in May. A linear relationship between total length and body depth (R =0.87) was found for this species. Of the 29 fish measured, the smallest, (newly hatched) was 4.0 mm with a body depth of 0.2 mm. As with alewif e, all newly hatched rainbow smelt could potentially pass, head on, through a 0.5 mm mesh screen. The largest rainbow smelt larva measured 25 mm in length and 2.7 mm in depth. Large numbers of fry (>25 mm) of this species were entrained during late summer and fall. These could be excluded by most smaller mesh sizes of intake screens. The 49 spottail shiner larvae measured showed a linear relationship between total length and body depth with a high (0.95) regression 367 TABLE 60. Summary of total length-body depth regression analyses for common Lake Michigan larval fishes. Y- R2 MEAN SQUARE SPECIES SLOPE INTERCEPT ERROR N Alewife 0.12066 -0.19394 0.85 0.12826 45 Burbot 0.17118 -0.40646 0.77 0.06379 13 Carp 0.17639 -0.21584 0.59 0.13218 16 Cottus spp. -0.00396 2.16529 0.00 0.92085 16 Johnny 0.12115 0.32023 0.72 0.16095 23 darter Rainbow 0.10847 -0.24987 0.87 0.07029 29 smelt Spottail 0.16717 -0.27825 0.95 0.05621 49 shiner Trout- 0.19119 -0.25428 0.95 0.05508 13 perch Yellow 0.17260 -0.33124 0.94 0.04708 41 perch coefficient (Fig. 153B). Minimum length of larvae measured was 4.3 mm, minimum body depth was 0.4 mm. Maximum measurements were 24.9 nim for total length and 4.5 mm for body depth. Spottail shiner were rarely entrained at either the J. H. Campbell or D. C* Cook Plants (Jude et aL 1975, 1979). Yellow perch were susceptible to entrainment at the Campbell Plant only when they were newly hatched. The 41 larvae measured yielded a linear total length-body depth equation with an R value of 0.94. Minimum length of newly hatched larvae was 4,8 mm with a corresponding body depth of 0.5 mm. Maximum length of perch larvae was 22.8 mm; body depth was 3.7 mm. Curvilinear total length-body depth relationships were manifested by large body depth values at relatively short total lengths due to the presence of a sizeable yolk sac, this was observed for Cottus spp. and johnny darter. As the yolk sac was absorbed, body depth decreased as length increased. After the yolk sac was gone, body depth increased with length as with other species. Cottus spp., of which 16 specimens were measured, ranged from 6.0 to 18.0 mm in length and from 1.0 to 4.0 mm in depth (Fig. 153D). Greatest body depth, 4.0 mm, corresponded to lengths of 6.0-7.1 mm. Body depth then fell sharply with yolk sac absorption and increasing length. At a length of 9.1 mm, body depths were reduced to 1.1-1.7 mm. From 9.1 mm on, length and body depth both increased proportionately. More data may indicate a linear relationship after the yolk sac was absorbed. 368 TABLE 61. Total length in mm at which common Lake Michigan larval fish attained a body depth of 0.5, 1.0 and 2.0 mm. Total length values were obtained from regression equations. BODY DEPTH (mm) SPECIES 0.5 1.0 2.0 Johnny darter * 5.6 13.8 Trout-perch 3.9 6.5 11.8 Carp 4.0 6.9 12.6 Spottail shiner 4.6 7.6 13.6 Yellow perch 4.8 7.7 13.5 Burbot 5.3 8.2 14.1 Alewife 5.7 9.9 18.2 Rainbow smelt 6.9 11.5 20.7 * Not meaningful because total length less than hatching length. Twenty-three johnny darters were measured with a length range of 3.0-20.0 mm at a body depth range of 0.6-2.8 mm. Much variation in measurements was observed. For example,, body depth was as great as 1.8 mm for lengths of around 5 mm while other specimens of comparable length had body depths of 0.7 and 0.9 mm. At lengths of about 7.0 mm, when the yolk sac was absorbed, body depths of 0.7-0.8 mm were recorded. Beyond this length, both total length and body depth increased proportionately to maximum values measured. Of the species analyzed, alewife and rainbow smelt have to grow well beyond the most frequently entrained, newly hatched size before body depths of 0.5, 1.0 and 2.0 mm were attained (Table 61). Body-depth data would suggest that these two species must reach relatively greater size, compared with other species examined, before they could be excluded by small screen meshes. The numbers of larvae entrained in 1977 at the J. H. Campbell Plant varied considerably according to species. Calculations of the percentage of alewife, spottail shiner, rainbow smelt and yellow perch that could potentially be excluded by small mesh screens assuming no avoidance are biased for some species because of the small sample size (Table 62). With a large sample size, (2,786 larvae), it was estimated that only k9% of all larval alewives entrained in July 1977 at the Campbell Plant (see Fish Larvae and Entrainment Study — Alewife) could 369 TABLE 62. Percentage of common Lake Michigan fish larvae that could be excluded by 0.5, 1.0 and 2.0 mm mesh screens. Per- centages calculated from 1977 length frequency entrainment data from the J. H. Campbell Plant. N = number of specimens entrained. Mesh Size Month Species 0.5 mm 1.0 mm 2.0 mm N ALEWIFE 48.9 97.8 100.0 100.0 27.8 82.9 100 . 0 100.0 7.2 60.5 60.0 100.0 July August September October 2786 2084 85 6 All Months Combined 70.4 50.4 30.6 4961 SPOTTAIL SHINER 93.3 100.0 20.0 100.0 6.7 72.2 July August 15 18 All Months Combined 96.9 63.6 42.4 33 RAINBOW SMELT 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 July Augus t September 2 4 1 All Months Combined 100.0 100.0 100,0 YELLOW PERCH 100.0 100.0 100.0 July have been protected from entrainment, even by a 0.5 mm screen. By August, large larvae with a higher potential for survival in nature, had increased in total length and body depth to such an extent that it was likely that nearly 100$ exclusion of larval alewives by small mesh screen would be expected. Large numbers of larval alewives could have been entrained in July even if 2.0 mm screens were employed but the magnitude of entrainment would have dropped significantly by August. To have achieved 100% protection from entrainment for alewife in all months , based on body-depth data and lack of behavioral considerations a 0.3 mm mesh screen would be required. 370 Using the same data and assumptions, a 0.5 mm screen should have provided 90 % protection for all spottail shiner, rainbow smelt and yellow perch larvae entrained in July and 100? protection in August, but these conclusions are based on limited data. As with alewife, 2.0 mm mesh screens would provide considerably less protection for these other species. Estimates of exclusion (Table 62) were made assuming that larvae pass through screens head first , that larvae with body depths equal to mesh size would be excluded and that there was no avoidance or behavioral responses . Tomljanovich et al. (1977) however, found that fish with body depths up to 84? greater than mesh size could pass through the mesh and be entrained depending on approach velocity of intake water. Thus, low intake water velocities will certainly aid in alleviating the entrainment problem. Because of Tomljanovich' s findings, the percentage fish larvae excluded by small mesh screens would span a certain range of larval total lengths and not be as clear as this paper presents . A further point not considered here is mortality of retained larval fish due to impingement duration on small mesh screens (Hadderingh 1974, Tomljanovich et al. 1977). There is a need for more data on the total length-body depth relationship for other species of fish larvae. This presentation is the first attempt to make such correlations for Lake Michigan fishes. Based on the species for which adequate data were gathered however, it appeared that a sound statistical relationship could be established between total length and body depth of larval fish and that this relationship could be useful in predicting the effectiveness of various mesh sizes of intake screens in preventing entrainment of fish larvae. 371 BENTHOS - LAKE MICHIGAN AND PIGEON LAKE Itaks MioMren - general Interest in the role of benthos in the ecology of Lake Michigan and the Great Lakes has increased over the last few decades. Although little work has been done on productivity and energetics of the benthos as they relate to other organisms, e.g. fish, in the lakes, much is being published based on the survey approach . Many of the studies operate on the assumption that although the benthos are difficult to study, they are good long-term indicators of the effect of suspected contaminants (Carr and Hiltunen 1965, Howmiller and Beeton 1970). While some benthic forms are mobile (some chironomids, naidids and Pontoporeia af finis) . most are confined to a small area. Of the mobile forms, only a small percentage actually migrate from the bottom at a given time, except during heavy wave action. Therefore, benthos are valuable in assessing long-term exposure to a contaminant. Benthic surveys have been published for the Grand Haven and Holland area by Powers and Robertson (1965), Robertson and Alley (1966), Hiltunen (1967), Alley (1968), Alley and Mozley (1975), Consumers Power Company (1975) and the Water Resources Commission (1968). These studies provided baseline data for the examination of benthic macroinvertebrates along the central-eastern shore of Lake Michigan. Focus of the present sampling effort in Lake Michigan was to survey a large area near the Campbell Plant for the followng reasons: 1) determination of benthic community structure at various depths , and nearshore/offshore abundance (density), 2) estimation of variance inherent in the benthic population in the vicinity of the Campbell Plant and 3) determination of a sample design adequate for surveys in this area of Lake Michigan in relation to the future offshore intake/discharge structures now being built and effects of the associated thermal plume on the benthic community. Total Animal Distribution — Distribution of total animals in Lake Michigan during the June 1977 sampling period followed the same general pattern in all three regions (see METHODS - BENTHOS for definitions of regions and depth zones). The generalized pattern was one of lowest average total abundance occurring at the 3-6 m depth zone (2600-4600/m , Fig. 154), increasing abundances at 9-12 m (6700-8500/m ), peak abundances at 15 m (1 3200-1 7900/m ) and slightly decreased abundances at 20 and 25 m (8 100-1 3^00 /nr ) . Although each region followed this general pattern, abundances in the 15-25 m 37^ depth zones deviated from this trend the most. The middle region at 15 m, which was offshore from the present discharge, had approximately 4000 /m more animals than did either the north or south region. Abundance of animals in the south region was similar at the 20 and 25 m contours when compared with numbers of animals found at 15 m. This was not true in the north and middle region. While abundance of animals was similar in the north-region at 25 m and 15 m, abundance of organisms was approximately 4000/m less at 20 m when compared to 15 and 25 m. The number of animals at 20 and 25 m in the middle region was approximately 9000 /m less than was found at 15 m. The middle region was richer in the number of species present when compared to the north and south regions,, Over the entire survey area 83 identifiable taxa were found. Of these, 77 were found in the middle region, 70 in the north and 71 in the south (Table 63). The middle region was the richest only at shallow depth zones (3-9 m). The most diverse depth zones were 9 m (57 taxa) and 12 and 15 m (58 taxa). Beyond 9 m, the middle region had consistently fewer taxa (2-8) than either the north or south regions. Neither the north nor south regions had consistently greater or fewer taxa than the other. Chironomidae Distribution — Thirty-one taxa of chironomids were identified from Lake Michigan near the Campbell Plant. Distribution of chironomids was similar in all three regions but varied across the depth zones considered (Tables 64-70, Fig. 155)p The general pattern was one of similar abundances at 3 m (2600-3400/m ), 6 m (3000-4600/m ) and 9 m (3000-4100/m ). greatly reduced abundances began at 12 m and extended to 25 m (400-800/nf ) . Specific differences between regions and depth zones for chironomids as well as other major taxonomic groups will be dealt with in the statistical section to follow (see Lake Michigan - Statistical Analysis) . In addition chironomids were sorted into two groups arbitrarily called the shallow-zone chironomids (3-9 m) and deep-zone chironomids (12-25 m) based on numerical importance and taxonomic differences. Shallow-zone chironomids were represented by 26 taxa and comprised numerically 43—96% of the total animals present in the 3-9 m zone. Deep-zone chironomids were made up of 20 taxa and comprised numerically 4-955 of the total animals present at 12-25 m.- Of the 18 and 16 chironomid taxa collected at 3 and 6 m, respectively, the dominant chironomidSpWere Robackia cfr. demeiierei (360-20QO/m ), Chironomus sp. (960-1400/m ) and Saetheria cfr. tvlus (360-940/m ). Chironomid taxa occurring in moderate density at 3-6 m were Crvptochironomus sp. 1, Paracladopelma cfr. nereis. Paracladopelma cfr. undine and Cladotanytargus sp. 373 < 1 2 o ■a § o a o 8. 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A o» « s» « ft* 1 3 A* I ft* > c -a 4J c E c C ffl d P u( £ J ajajcjajjajajajjcjajcjajcjoj 395 I* T3 2 -S S- o oo m m N vfl \fl CS vO ^O vo m f-* vO ifl H lx o o OP G •H -P O o ^ 396 £ 6 § PL, H H -p 4) «5 3 -P 03 2 O • u • ^ w C • cd CO T3 1 ,o a) < a> a • u ao vo IX I c— 9 ft: e* H ** « o n- © ^ m o » *> v* <* O »^ w> -^ %% » • • » • o M « ** -*r MP © o O »• *♦ ^ *0 M -♦ •■* • *% o a o o CO r«# o o O o ^ S> S q « M • -*» »«» «* «»% o o 3 •* 4 O «t O 9* p< o ** *< *4 >o *• M vO »0 IH «# f*« r* «* *» »# v© »♦ *» *+ o v4 •■* o r* r«i o O o «M »» -^ *■* « IM Jt f* «* *0 *0 c« <*r f<« *4 sr **• NO ^* "* * ^ *< ** v% ** »■« «* r« e«e •» «rt • 0* A «« •^ rt r* f* •* •>4 i^ f* y\ r% •0 f* ^ *% *• o © «■* P*» o o •* i £ O 4 8 «• «# • %o <0 © m o «e 00 vO 533 • ot o O <* ri o o o oo M ** •0 *» <0 o «o ^0 to CO 3*3 4* «i •-4 f* •^ 3 I • *0 m »0 10 ^> *» hO «e « >a >0 <0 ^ e« O «*i u m «-# o o r« «n o o *-4 m • • • • • • • * • • • • * • 2 •* <■« «n •^ 3 •"* S a i ^ Ofc Kk **» F*6 f«*» t* • «-4 «0 <^ M «* m «*• <*« *i r>« • « * • • • A •4 . p* •4 •* *»4 m* >© «4> «0 «^ f« 4* #n «^ 2 3 m O *0 «4 M> vO %o «o 9* *«. m 0k m Fl O O » » O W> O O O O C4 « «e M • • • • • «A <0 *» «0 «o « %» «n CO 0fe <0 • m Ob «4 9* ^r «♦ r* 3 X «♦ <0 «© <0 *0 <* <• O *« ^ ^ #«J t^ M *4 ** o «•* o o o o m Nd tM m 40 *» <0 *0 «o *» o « M% «4> M r* m M t*. rt «^ 10 ^ »-i p* • • • • •> m «4 « O » «0m<«>O»m<> O «CO O «A f-» Ofc O »♦ ^ <^o» >o <-» «♦ en • « 10 <0M vffi O «♦ CO f« ^ M « «M £ -• a w u w w a, e «^ u • « 0/ ^ -0 > c 3 TT -3 9 W e e «4 a 4 ^ O « T3 -a « ■O U k* « Ci c u U O 4» 0 Cm a -3 1 ? «• «s o tj > >< C u k- ** c c •^ c 0 i * m w • 0 o a u i *• «• O *• U A* A» xl *•! «1 ^ ^. « 397 i s s © <* © © © *♦ « « « < n • • • • « *a o ct ~i <•* f» O C°>« «■* r^ «rt *"* • © *»e flt « © v% p»t «* ** «tf s© «o f* © vs e*e «a <*d r* *c -4 © *-« O ©<» • •••«« n n x m **> <0 o <* <*► • e iM © t* n© ** ^ #4 «"» as o p*» n «-» v> >. «•» m « OS 26 • e 3 Q) e e «8 n J£ ec Ct, •8 « X u <* V T3 C *£ a U u E V «9 s 9 a 64 S <0 « «M 3 k> U2 o C Q. JS, m 10 •» « V) 3 3 3 o »^ dS -« »» la U •9 "^ «3 '^s. o c 0 *. I I | •*. >»5 •* S a «9 3 C O * o °a 'O o c 3 « Vm a. O m u> &j u «>4 • • r. «4 ■ 3 e >< c e « J^ 4* « C u > > o M « o e "O "O «1«* he <»4 >^ e» ta 0 c* &l a m s > 3 m <& W >c 9k •<4 X * 3 u fc. tt « 6-« JE X S^ 0 0 to C 0 u w *0 E s 0) 0) o C3 c o 0 «=*» ^ 0 0 « y . - o CO 00 *-i Ix e «* »re rei ««> ,«> ^> © o «-* • • • • • S 5 " ft - <"» o a» «i «* «■» ** ere w • 2© o o <# c* « «re «\ © • • » • • *• m *4 3 ji a IA 3 6 O c 0 « 3 B O C 0 3 □ O c o M W u e 4» ■» 6 u 1 4t c a, • •< 3 C •* • •• 3 M 9 B <9 8 u (3 fib • k. CH a. & <-< «• 3 M m «9 «c • O o 0 ■a ** >> CI 3 u o j: T» •o ■e n u C „* o u u re <3 « — c o T> *« re "« O re Q o 5^ u u u O m o U a >< -3 0 c K U 0 u « « m A* u *0 A. ft* 0 *» u *• • « 3 9 «4 «^ re m u u o o * ■ w w & O h. b « i» o v X s Uoi • I © *•* »** r* «*» «* w* • • • • * • * «a o O O «• ~i** •< ■? mo ^ o «* r^ O O © <«© « «s « © « • • © «0 *8 *» ?•» q <«> re «* t* ^ — _ _ _ « N N *tf ^ <* G o o o o o o 3 «* *© .-o *» 000*-4Q o *? O ssas « « ~ 2 • * o <• 3 e « « «e*tf>0 *B >e «A ^ «» <£> «4 «ft Ot *e «* O O O 9* O O «» © * » • •«•«• « , c «•***© a) G •H C o a ON vo i «■? <£ s * S 3 « • g s 2 3 M 3 S *• «• © © « M N © <* v-t • * * <*p re m *• ** O «« «4 • • • • • • 3 3 fc. w « •*4 ft 3 o 3 IS o2 00 C ** « M •■* * « 19 > « #■* a ** * * ** « ss «a K • ts 3 41 e e as * : * V * fe» «-* oa c a 9 M •> M 3 3 ha h> °3 «^ O 0 J c e 2 2 J? i u| S ii02 m r-4 rH CJN GO en Ci3 co O o » a\ rH m rH o CO cm m m go m r*» on O r-. cr> m on co cm en O co > H CO* col 'A oj ej a»1 cj 4 aj U03 c o r*H "So cc W o f-4 cn cn cm •H -P O a OS E3 Eh CM o o CM cn O O 00 O e-4 o PS. oo cn rH m cm cn r- r>» o rH O r-4 00 CO o o o r» vo cn ao co r-4 iH oo co oo m n m O «h m cm CN 00 1-4 O CO r-4 CM vO O CM oo r-4 vO 00 CM V© e- oj J J aJ i;04 c <0 U a) O i* co 3 fH -J2 < 1) C • 3 O ""3 fc— C •H » i-3 a 3 m H CN 4 3 3 3 S >* ^ • ° 2 2 * 2 n ° «s 9> r*> ** q O w> .A v« <-> • • • • • N O ^ N rt *2 •» • <*> <*• m «♦ O «*» <*» «M r< r-4 O ••••••• «H ^ 0O ^ vft tO «« «* ot <* ** »3 2* *#• <# «*% r* >f 9^ m «0 M> N ^ o ^ «n <# *T «4 2 *l i 3 3 £ f*> *l O *• * O -* ^ n o H *© *"» *%. o ^ <# £ * O O O <* M © «X «* #-» ® f* ^ ••••••• * O © O *"* ^ M 2 «* « • ** •* • s m 3 •• s 25 ° o *% « © o» o O <* m I* • • • • • •^ **» ** o o « *• «* >J w w °o 3 3 S B • « < 0 e C 0 O u g s fco c c c «M 0 o o w c o w u •* w . a «9 o _o" « 0= x: TJ u o w u ra c JA o 0 o ft> U ta o o aj a a a w « « ^ >i > >* V u u o u u c 41 <8 ftt u U o tf> 0. A. B -4 •^ e *• CJ *4 - « ^ 6 ^ u u o « »: « W *« O Ob « g a a * M 5 3 « « >> « ~ « 3 C "** -* c *• « *« "O 9 •& o a a «o ^« «o >^ >> o o « «4 •-• c o ^ 0 O O w UJ A* fe Si Ao 1+0 = I a I A I 1 7 C 5 «: s JM « #* ** • • • 3 3 s s art o e • c* •* OB «*» •4 •* «rt «* «4 «4 4» • • * « - s s s s a s 2 s " a s s s s s s • • o © *o «B o «n o *« « • • • «4 m m s a «) e e O ^ < c U C X (A JR u £ m v* ■*» § We • V *j ** 4J M «4 c (Q 8> «• *# C u a o «e u e ** «■* e 3 w *"* IS as m .* a «0 ft 9 > c c e o •»< a « T3 o b» i* «*-i c a 4 H at) «** « «B 3 • t* £ »4 « s O E <« a 3 n « «m 3 u Vtrf a tJ «*4 . CJ «* O 4 o &l w> 0 oS (V us Q. M 6 e « « a V) w 3 3 3 3 « w O «o -o t» °e •o c 0 C 0 o o E 3* » e 1 e s c g s « 5 2 2 u ^ o 0to Q A.1 U06 o m m r»» vo en v£> «N CN *4 f-H rH en r«. m m m ^o en m O o N H 00 O CO o CO © ON CN o> 00 en en fH m en co O ON o o O CO CN r-i r-» fH O o CO co m en rH CO I— 1 00 1^. CO f-4 en r-t CO f-4 CM CO o en o en CN r-. CO O en o en o o iH O 0> f-t vO CO en vO rH en CN rH ^O en r^. o" o cn en en cn r-j o\ r-i in vo en cn en vo vO •H -P c o O o a 5 «i-«U U07 o oo m cm vr o 00 c 00 r* r*» o O m f-t GO a\ VjO O r-» rH r-i 00 i— I CM SO CO e-J pH r-» p-> o ci in m r». r-t a\ IX O CM CO r-» o co cr* r-4 so »h ci 00 O VO r-* I* CM CM CM CM •H o o a i i co on to c— c I I 0 v rn it* &-. J a] cu J fC — CO 0 i) c cc c i E > e i r^ r^ l w 3 •-5 c T3 •H "3 T3 1 03 I "O 1 c CO a; -a g *-> J? 0) a s •H 0) X • 03 03 C 03 a CO «H o M •h o oo > t- u >> 0) a c 03 c D <3 2W / 'ON a fa I o 0) U13 2 moderate abundances were Potamothrix mqldaviensis (51 /m2), l4mqQdr;Lly? orofundicola (44/m ) and UmpQdrUy? epgystipenis (34/m ). • At 12 m L- hoffmeisteri was the most abundant tubificid species (45/m ) of the seven identifiable tubificid taxa collected. Remaining species1 abundances were split evenly between JL. profundicola, £, moldaviensis. Peloscolex frevi and L- ?flffu?tipenig. Of the seven taxa of tubificids collected at 15 m, the most abundant were P.. moldaviensis (95/m ) and L.. hoffmeisteri (9|/m ) . The only other common tubificid was Potamothrix veidovskvi (36/m ). Of the seven tubificid soecies found at 20 m9 L.. hoffmeisteri was the most common species (55 /m ). Z° moldaviensis and P. veidovskvi were the only identifiable tubificids present in significant numbers at 20 m (12/m and 18/m /respectively). Five species of tubificids were collected at 25 m . k* hoffmeisteri was the dominant tubificid species (32/m ), followed by £.. ve idovskvi (10/m ). The immature with hair chaeta (im w/hc) comprised 17% (44/m ) of the tubificids at 25 m. P^Io^cqIqx superiorensis (8/m ) was present in its maximum abundance at 25 me Stvlodrilus heringianus Distribution ~ Distribution of Stvlodrilus heringianus was similar across the regions (Tables 64-70, Fig. 158) but was not taken at depths shallower than 15 nuexcept in the middle region at 9 m. At 15 m mean abundance was 933/m . Population size increased approximately two-fold at 20 m (2050/m ) when compared to 15 m. The number of £• hertogiUnus collected continued to increase at 25 m (2954 /m ). Abundances of &. herjpgj.^pus at 15, 20 and 25 m corresponded to 6$, 20 % and 25? of the total animal density, respectively (Fig. 159)- Pontoporeia af finis Distribution « Pontoporeia affinis were sorted into size classes following the procedure of Mozley (1974). Immature JP. affinis were sorted into size classes <3 mm, 3-4.9 mm, 5-7 mm and >7 mm. Mature £, affinjg were sorted into gravid females, spent females and males . Of particular importance to the present study was the <3 mm size group which was considered to be young P.. affinis released from the marsupium of females earlier in the season (presumably in April and/or May). It has also come to the author's attention that the species name for £. affinis has been changed to £. hovi during the course of the study (Segerstrale 1977). Since all tables and figures had already been UlU 3 s H UJ Q m ? -a • M ao rH n\ T CQ H 1 ° 1 -H o 1 u C2? 1 M M 1 ^ fa Ul5 1 2 ? ? ? ? - « V •» £ N » • » O z a. a. w H o * 4* H O a o AS £ ^9 Cfc <9 1 <9 s C o o o 40 o Q O s * C 03 o u a o c o X O •r-j cd S O c o o a. a o a 0) as a a N0ll!S0«iW03% c Gv H «H a g Ui6 completed, it was decided to retain the old name, £. af finis. The general pattern of distribution of £.. affinis was similar in all three regions (Tables 64-70, Fig. 160)^ At 3 and 6 m there were very low number of £.. affinis present (4/m and 38/m , respectively). Of these 86? were young (<3 mm). The first depth zone where £. affinis began to occur in significant numbers was at 9 m (1733/m ). Young individuals (<3 mm) dominated the population (96$) of £.. affinis. The trend of increasing abundances of £.. affinis with depth was also evident at 12 m. Size of the population increased about 2.5 times when compared with 9 m levels and comprised 64% of all the animals present at 12 m. Average density present was 4822/m with most (99.7?) being young £.. affinis, 2 Peak abundance of P.. affinis occurred at 15 m (10,023/m ) in all regions, which was approximately a two-fold increase in the population size when compared with 12 m levels. P.. affinis comprised 67? of the total animal population at 15 m. Again young £.. affinis was the most numerous size class (98?). At 20 m population size began to decline and the population age composition began to shift to slightly older individuals. Mean abundance of £. affinis at 20 m was 5454 /m . Although young individuals were still the dominant size class (73?), age structure of the P,. affjnis population at 20 m included more 3-4.9 mm (13?) and 5-7 mm (13?) individuals than was found at shallower depths. 2 Although the average number of £. affinis at 25 m (5457/m ) was similar to that observed at 20 m, the population age structure shifted to older individuals. At 25 m 57? of the P.. affinis population was comprised of the youngest size class. The 3-4.9 mm and 5-7 mm classes comprised 20? and 23? of the £,. affinis population, respectively. Gastropoda Distribution — Gastropods were represented by three taxa; Valvata sincera. Amnicola sp. and Lvmnaea sp. Possibly, a fourth taxa, Somatogvrus sp., was present but since it is rare in the lake and taxonomic determination is difficult, it has not been included. At all depths the most numerous gastropod was V. sincera. Lvmnaea sp. was limited to a single occurrence at 25 m in the middle region. The general distributional pattern of gastropods was different from region to region (Tables 64-70, Fig. 161). Numbers of gastropods in the hll C 03 | I e 1 r^ ! ON cy 3 •-3 e c 3« / ON C 03 rH PL4 ^ ^ Q) * 8 t* ^ M 2 <-» c ,-» „, 03 M-l ^ o c JS T3 H O* M 03 xz T> ■ « 4J a a 3 03 M g u to CO m hi8 -=cklJ— !— ' < Q O a. o oc in < < O O O .M 4J 3 >> O ^2 • CO T3 T3 > u CONOvO oooo oooo oooo o o o o cm oooo CM ^ \fiN«OH «h o u"» o> ^ cn «/"» C* *-4 O • • • • < o> *y h o> ^ *h m ^ CM N vO I i-* ** O O rH O ooxeo n O o »-» o hso vn ao noo^H h rs» oo OOOO o cm o OHvfiN NHMM »a ia o> cm • o • • vO vO vO vO »T W N vO vfi (N vO vO »j ao ps cs o • o • »* »n so ««r in vo -c u-> oa cm f^ o\ ONMH OOOO 00 «-t »» tit *-4 *tf r* 0% CM »H CM iH iA 0» CM iH •* »a fM o CO (A iO vO OOOO OOOO oooo oooo M3 en en fM iA «»3» cn so HtnoooN *-* *-4 <30 O WlAN(*| CM 00 !50 *» « • • • N»JNO CM cm tri fv h 00NO<^ vo en cn so ©> cn cn cn a a a a en c^ cn cn I l I 1 cn «^ ^ »a ^ co ia co r* en r* 5 o\«rt f-» m «a^ia cn so «* co Neon ^ HCMH MHHH «-( CM r*» O *4? cm cn co cm CM f* CM CM cn CM C* M> CM CM Ci CM CMcnCM t-4«Hp«iiH OOOO \0 CM »A M3 cm i-H cn r*» O *-» M3 CM Cn CO N CO a a a a vO O sO vC» I f I t co cn en f-i ia en co cm cn o cm cn a a a a cn cn ci\ o> I I » I cn cn cn co cm cn r^ \o co rs O co earns CM CM CM CM HCOvOO *H SO «A vO cn cm »a en a a a a »A tA »A lA ">* CM IA *5> OA CM SON m »a *» <^ *o *a a> «a CM CO OV O »ri <»* sr «n a a a a aasia ' i J i i i t it W Q) Q) •SS^'^ -C^JS^H JZ ~4 j£ ~4 5~.2^° o «h o o o -h o o ZSWH 2XWH 35SWH t t 1 I 3 J2 *H JS ^4 *-» -o JJ CO »-• *U 3 *J O -^ O O « S W H oooo CM CM CM CM U*4 lA »A »A CM CM CM CM I I I I I I JS. ~* JS ^ *-» T3 *J CO u -a 3 jj o -* o o 2= S W H — »-4 «e fH O -H O O ' t » • JS r-4 jet «-4 OH O O U21 0) M rH. O *V M T3 H •H > w tu o . Q rH W L> "0 rH G ^ 03 3 u o *Q rt "H < 0 -^ CM \o H 03 s 0) ^W/'ON o G CU a U22 abundant in deeper water. 5.. transversum was rare; only seven individuals (five of those from the south region at 15 m) were found. 5.. nitidum was the most abundant of the three taxa (87-105/m ). Similar to jg.. nifridumT;jS. striatinum was most abundant in the 20-25 m depth zones (24-42/ni7. Replicability and Reliability — Based on June 1977 data and using total number of animals per grab, the within mean square from a two-way analysis of variance (Depth x Region) was used in conjunction with Sokal and Rohlffs (1969) formulas to estimate the least detectable true difference (5) and reliability of the data for detecting changes in benthos near the Campbell Plant . The theoretical relationship between 6 and the successive number of grabs (n) needed to alter 6 is presented in Fig. 1 63 . While any n from Fig. 163 could be chosen, six replicates were selected for use in calculating 6 based on the relationship between s (variance) and the succcessive number of grabs presented in Fig. 164. For any particular depth zone the extreme values for variance began to approach a stable level at approximately six replicates. When six replicates were related to the (5 value (Fig. 163), 6 equalled 143 animals per sample location (« = 0.05, P = 0.95). Due to the large variances associated with these natural populations of animals (Coefficient of Variation = 40?), the difference between any two sample location means must differ by 143 animals in order to detect a significant difference at « = 0.05 and P = 0.95. The effect of increasing sampling effort was negligible when evaluated against time and cost factors., By doubling effort to 12 replicates per location, the ability to detect change (6) was increased 36? to 92 animals per location. By tripling the effort to 18 replicates per location, the ability to detect change (6) was increased 50? to 72 animals per location. Therefore, based on the June 1977 data set, future sampling efforts in the vicinity of the J.H. Campbell Plant should have six replicates per sample location (« = 0.05 and P = 0.95) if a detectable difference of 143 animals between any two sample locations is acceptable. If increased sensitivity is required sample effort will need to be substantially increased. Analyses of Variance — Results of tests for normality of subsets of the benthos data set are presented in Table 72. The following transformations were used in order to normalize specific data sets for subsequent application of parametric statistics : total animals (3-25 m) (/x ) , shallow-zone chironomids (3-9 m) (log [x+1]), deep-zone chironomids (12-12 m) (none), U23 o o o o o o (avHs/ sivwinv ivioi) ^ 0) o c CD n "3 U2U No. of grabs FIG* 161+ . The relationship between the variance (s ) and number of replicates. The two lines on each graph outline the upper and lower extremes of five curves generated for each depth zone from random draws from 30 replicates at each depth zone. 1*25 5 i o -J a- ism zone 20m zone 0 3 6 9 la 5- 15 18 21 0 3 6 9 12 15 |8 21 5- o 25 m zone 0 3 G 9 12 15 18 21 No. of grabs PIG, 16k . (continued) . k26 TABLE 72. Results of testing for normality of data subsets from June 1977 in the vicinity of the J. H. Campbell Power Plant (n = number of samples, Maxdiff = maximum cumulative frequency distri- bution difference, L = Lillieforfs 99% quartile test value), * = significant. n HAXDIFF L SIGNIFICANCE SKEWNESS JCURT0SIS BATA SET USED IN ANOVA T. Aniaal* 3-25 m No Trans Log(rfl) 210 210 210 0.117 0.074 0.056 0.071 0.071 0.071 NS NS a 0.838 -0.287 0.310 -0.023 -0.651 -0.669 X J>. affinU 9-25 ■ No Trans Log (x+1) 150 150 150 0.102 0.096 0.076 0.084 0.084 0.084 NS NS * 0.967 -O.508 0.217 1.110 -0.285 -0.495 X T. Chir. 3-25 m No Trans Igg (xH) 210 210 210 0.219 0.114 0.167 0.071 0.071 0.071 NS NS NS 1.645 0.106 0.773 3.214 -0.959 -0.209 T. OUr. 3-9 b No Trans ^g (x^D 90 90 90 0.108 0.036 0.078 0.109 0.109 0.109 * * « 1.518 -0.053 0.703 3.369 0.269 0.924 X T. Chir. 12-25 a No Trans lp 150 150 150 0.160 0.087 0.072 0.084 0.084 0.084 NS NS 1.694 -0.296 0.366 3.700 -0.707 -0.187 X TUblfleldas f-15 m No Trans 90 90 90 0.143 0.106 0.052 0.109 0.109 0.109 NS a a 1.611 -0.579 0.289 3.102 -0.177 0.033 X U2T naidids (/x), Pontoooreia affinis (9-25 m) (/x) , tubificids (9-15 m) (/x), Pisidium spp. (12-25 m) (log [x+1]) and Stvlodrilus heringianus (15-25 m) (/x) . No transformation of the "total chironomids" data set (3-25 m) would normalize it. Data subsets were chosen for each group based on depth zones of maximum occurrence. An Analysis of Variance (ANOVA) was performed on each of the above transformed data sets (Tables 73-81). For the total animals, £.. affinis and naidid data sets there were no overall regional differences , but there were significant depth and interaction effects. For the deep-zone chironomid data set only regional effects were significant. Only depth effects were found for the tubificid and &. heringianus data sets. The shallow-zone chironomid data set had no overall significant regional ? depth or interaction effects. The Pisidium sppB data set had significant overall effects for regions, depths and interaction terms, Student-Neuman-Keuls Multiple Comparisons — The within mean square from the appropriate ANOVA for each major taxonomic group was used in conjunction with the Student-Neuman-Keuls multiple comparison technique. In the first portion of this section (see below) results from comparisons made within a specific depth zone across regions for dominant taxonomic forms are presented (Fig. 165)* In the second portion results from comparisons made within a specific region across depth zones in that region for dominant taxonomic forms are presented (Fig. 166). Multiple comparisons among regions within depth zones — The 3 na depth zone — » There were two major taxonomic groups dominant at 3 m; the chironomids and the naidids (Tables 64-70, Fig. 165). There were no significant differences across regions for the chironomids. However, naidids in the south region were significantly less abundant (24/m ) than those in the middle (176/m ) and north (103/m ) regions. The dominant naidid in the middle and north regions was Nais elinguis. &. elinguis did not occur at 3 m in the south region. The 6 m depth zone — At 6 m average number of animals in the north region (5042/m ) was significantly higher thatn average numbers observed in the middle region (3691 /m ) (Tables 64-70, Fig. 165). Average number of animals in the south region (4945/m ) was not different from either region. Dominant taxonomic groups were chironomids and naidids (Table 71). Chironomids were significantly more abundant in the north (1388/m ) and south (1206/m ) regions when compared to the middle region (957/m ). Chironomus sp. was ~300/m less abundant in the middle than in the north and south regions,, JR.. cfr. demeiierei was ~l600/m more abundant in the north and ~500/m more abundant in the south than in the U28 TABLE 73 . Analysis of variance for total animals (3-25 m) using the /x transformation. The correction factor used was 0.995. NS = not significant, alpha » 0.05, * = significant. SOURCE CORRECTED DEGREES OF FREEDOM CORRECTED MEAN SQUARE SIGNIFICANCE REGION 2 DEPTH 6 REGION x DEPTH 12 WITHIN CELL 188 4.07 253.36 12.32 5.24 0.78 48.35 2.35 NS * * TABLE 7^+. Analysis of variance for total animals (3-25 m) using no transformation. The correction factor used was 0.995. SOURCE CORRECTED DEGREES OF FREEDOM CORRECTED MEAN SQUARE REGION DEPTH REGION x DEPTH WITHIN CELL 2 6 12 188 2552.23 135559.22 9474.50 3220.63 TABLE 75. Analysis of variance for shallow-zone chironomids (3-9 m) using the log (x+1) transformation. The correction factor used was 0.989. NS = not significant, alpha = 0.05. SOURCE CORRECTED DEGREES OF FREEDOM CORRECTED MEAN SQUARE SIGNIFICANCE REGION 2 0.017 0.46 NS DEPTH 2 0.030 0.80 NS REGION x DEPTH 4 0.085 2.27 NS WITHIN CELL 80 0.037 ;29 TABLE 76 • Analysis of variance for naidids (3-15 m) using the v'x transformation. The correction factor used was 0.993. NS = not significant, alpha = 0.05, * = significant. SOURCE CORRECTED DEGREES OF FREEDOM CORRECTED MEAN SQUARE SIGNIFICANCE REGION 2 0.56 0.66 NS DEPTH 4 53.69 45.40 * REGION x DEPTH 8 3.87 3.27 * WITHIN CELL 134 1.18 TABLE 77. Analysis of variance for tubif icids (9-15 m) using the v'x" transformation. The correction factor used was 0.989. NS = not significant, alpha = 0.05, * = significant. SOURCE CORRECTED DEGREES OF FREEDOM CORRECTED MEAN SQUARE SIGNIFICANCE REGION 2 3.82 1.60 NS DEPTH 2 20.02 8.38 * REGION x DEPTH 4 1.81 0.76 NS WITHIN CELL 80 2.39 TABLE 78. Analysis of variance for P. af finis (9-25 m) using the Vx transformation. The correction factor used was 0.993. NS = not significant, alpha = 0.05, * = significant. SOURCE CORRECTED DEGREES OF FREEDOM CORRECTED MEAN SQUARE SIGNIFICANCE REGION 2 DEPTH 4 REGION x DEPTH 8 WITHIN CELL 134 0.11 205.91 11.34 3.43 0.03 60.03 3.31 NS * * U30 TABLE 79. Analysis of variance for Pisidium spp. (12-25 m) using the log (x+1) transformation. The correction factor used was 0.991. NS » not significant, alpha = 0.05, * = significant. SOURCE CORRECTED DEGREES OF FREEDOM CORRECTED MEAN SQUARE SIGNIFICANCE REGION DEPTH REGION x DEPTH WITHIN CELL 2 3 6 107 0.353 1.380 0.322 0.104 3.39 13.26 3.10 * * TABLE 80. Analysis of variance for deep-zone chironomids (12-25 m) using no transformation. The correction factor used was 0.991. NS = not significant, alpha = 0.05, * = significant. SOURCE CORRECTED DEGREES FREEDOM CORRECTED MEAN SQUARE SIGNIFICANCE REGION 2 DEPTH 3 REGION x DEPTH 6 WITHIN CELL 107 132.55 25.46 23.43 18.03 7.35 1.41 1.30 * NS NS TABLE 81. Analysis of variance for _S. heringianus (15-25 m) using the Jx. transformation. The correction factor used was 0.989. NS = not significant, alpha = 0.05 , * = significant. SOURCE CORRECTED DEGREES OF FREEDOM CORRECTED MEAN SQUARE SIGNIFICANCE REGION DEPTH REGION x DEPTH WITHIN CELL 2 2 4 80 13 . 93 87 . 61 2.27 5.08 2.74 17.23 0.45 NS * NS 1+31 Depth Zone: 3 M Total Animals N M S LSR=1.38 7.47 7.17 6.53 h ^ Shallow Chironomidae N M S LSR = 0.I2 1.73 1.68 1.63 1 H Total Noididoe M N S LSR = 0.66 1.63 1.05 0.34 I , | , Depth Zone: 6M Totol Animals N S M LSR= 1.38 8.81 8.76 7.40 » 1 I 1 Shallow Chironomidae N S M LSRsO.12 1.83 1.77 1.63 I , , .-_, Total Naididae S M N LSR = 0.66 3.83 2.61 2.45 I 1 > FIG". l65.. Results of multiple comparisons of specific depth zones across region (N=»north, M=middle, S=south) using the Student- Neuman-Keuls technique for the most abundant major taxonomic groups near the J. H. Campbell Power Plant, in June 1977 ._LSR - least signifjxarvt range at <= = 0.05. U32 DEPTH ZONE; 9 M Total Animals M N S LSR=1.38 11.53 11.03 10.98 Shallow Chironomidae M S N LSR = 0.I2 1.80 1.68 1.63 I H H 1 Total Naididae N M S LSR=0.66 5.28 4.62 4.22 I 1 Total Tubificidae M N S LSR = 0.93 4.35 4.11 3.20 I 1 Ih Pontoporeia of finis S N M LSR = I.I2 6.03 5.08 4.55 h — \ I — FIG'. 2<55. (continued). i+33 DEPTH ZONE: 12 M Total Animals N M S LSR = 1.38 11.64 10.91 10.44 ■ I — 1 Totol Tubificidae N MS LSR = 0.93 3.07 2.30 1.93 h 1 I- Deop Chironomidae S N M LSR = 2.57 11.90 |(. 50 8.90 I 1 I 1 Pontoporeia af finis H M S LSR=L12 9.07 9.05 8.22 I 1 Pisidium spp. N M S LSR = 0.!9 1.17 0.95 0.79 I 1 h Totol Naididae S N M ISR = 0.66 3.81 3.09 3.08 | , FIG:. 165. (continued). 1+3U DEPTH ZONE- 15 M Total Animals M N S LSR=L38 17.08 14.69 14.65 I 1 I " i Total Tubificidae MSN LSR = 0.93 4.07 3.77 3.64 I 1 Deep Chironomidae S M N LSR =2.57 12.60 7.90 6.80 I 1 1 1 Pontoporeia af finis M N S LSR =1.12 14.29 11.96 11.65 H 1 I 1 Pisidium spp. M N S LSR =0.19 1.44 1.42 1.12 Stylodrilus heringianus S N M LSR = 1.3 6 4.13 3.10 2.85 H 1 Total Naididae MSN LSR =0.66 2.75 2.65 2.00 H FIG. i65. (continued) U35 DEPTH ZONE- 20 M Total Animals S N M LSR = 1.38 13.93 12.08 11.44 I 1 1 " 1 Deep Chlronomidae S N M LSR =2.57 9.80 9.10 7.00 H 1 Pontoporeia at finis S M N LSR = 1.12 9.61 9.26 8.81 I— 1 Pisidium spp. S N M LSR =0.19 1.36 1.20 1.05 | 1 I- Stylodrilus heringianus S N M LSR =1.36 6.11 5.21 3.81 H 1 H 1 FIG. 165. (continued) U36 DEPTH ZONE* 25 M Total Animals S N M LSR = 1.38 14.62 14.49 11.61 I 1 I 1 Deep Chironomidae N S M LSR =2.57 11.40 11.00 6.90 h Ponfoporeia affinis H S M LSR = 1.12 10.08 9.89 7.85 J J h Pisidium spp. N S M LSR = 0.19 1.60 1.58 1.25 4 — 1 I 1 Styhdrilm heringianus S N M LSR = 1.36 7.07 6.78 6.54 I H FIG* 165. (continued). 1+37 OVERALL N M S LSR =0.91 11,46 11.02 11.42 Total Animals j i N M S LSR =0.12 1.74 L70 L6 9 Shallow Chironomidae Naididae S M N LSR =0.51 2.97 2.94 2.77 J 1 H M S LSR =0.93 3.61 3.57 2.97 Tubificidae S N M LSR =0.87 9.08 9.00 9.00 Ponfoporeia a f finis S N M LSR =2.22 11.33 9.70 7.68 Deep Chironomidae ) | N S M LSR =0.17 135 1.21 LI7 Pisidium spp. j i I -! S N M LSR = 1.36 5.77 5.03 4.40 Stylodrilus heringiarws t j I A FIGi i£>5. (continued). U38 Total Anlmolt 15 M 14.69 25 M 14.49 NORTH REGION 20 M 12.08 12 M 11.64 9M 11.03 6M 8.81 i H 3M 7.47 H h LSR*U6 Shallow Chironomidce 6M L63 3M 1.73 H h 9M 1.66 LSR* 0.12 NoidUoc 9M 5.28 I 1 12 M 3.09 h 1 6M 2.45 ISM 2.00 3M 1.05 \— 1 LSR* 0.59 Tu bifid da t 9M 4.11 ISM 3.64 H h 12 M 3.07 LSR sO.93 Poafoporefa of finis 15 M 11.96 25 M 10.08 H h H b 12 M 9.07 20 M 8.81 9M 5.08 LSR = 1.01 H h Dtep Chironomidoe I2M 11.50 25 M 11.40 20 M 9.10 15 M 6.80 LSR = 2.44 ffsrtftvm ftpp, 25 M 1.60 I 1 ISM 1.42 1 1 20 M 1.20 12 M 1.17 LSR* 0.18 Styhdfilus h^mgionat 25 6.78 20 5.21 H h -i h 85 3.10 LSR M.36 FIG4> 166. - Results of multiple comparisons of specific regions across depths (3-25 m) using the _^tudent-Neuman-Keuls technique for the most abundant major taxonomic groups near the J. H. Campbell Power Plant in June 1977. LSR = least significant range at « =0.05. ^39 MIDDLE REGION Tolol Animals I3M 25M 9M 20M «2M 6M 3M l?*°« ««« «.53 U.44 10.91 7.40 7|7 I H | . . , 1 __ L$R*M6 Shallow Chironomidat 9M 3M 6M LSR«0.I2 1.80 1.68 L63 | 1 | , *•»«*«• ^M I2M ISM 6M 3M LSR*0.59 4.62 3.08 2,75 2.61 1.63 I 1 | _< h Twbiflcidot 9M ISM I2M LSR*093 4.35 4.07 2.30 ^ h Pontoportia ef finis ISM 20 M J2 M 25 M 9 LSR*I0« 14.29 9.26 9.05 7.85 4.55 | «H , _ 1 ^_ , j_ j D««p CMronomidot 12 M !5M 20 M 25 M LSR*2.44 8.90 7,90 7.00 6.90 I ! MMtat tpp. 15 M 25 M 20 M 12 M LSR«0.I8 M4- 1.25 1.05 0.95 | j , 1 H St/toJrifui htringiQmss 25 M 20 M ISM LSR»I.36 6.64 3.81 2.83 | , , H FIG'. 166. (continued). Ul^O SOUTH REGION Total Animals 15 M 14.65 25 M 14.62 20 M 13.93 9M 10.98 -I h 12 M 10.44 6M 8,76 3M 6.53 H h H h Shallow Chironomidae 6M 1.77 9M 1.68 3M 1.63 LSR«0.I2 LSR'1.16 Noidldat 9M 4,22 6M 3.83 12 M 3.81 15 M 2.65 -i b 3M 0.34 LSR*0.59 H h Tublficidov ISM 3.77 9M 3.20 12. M 1.93 4 h LSR-0.93 Pontoportia off Ms ISM 11.65 25M 9.89 -i *" 20M 9.61 12 M 8.22 -I h 9M 6.03 I H LSR*t.0l Otcp Chironomidae I5M 12.60 12 M 11.90 25 M 11.00 20 M 9.80 LSR-2.44 Ptsidium «pp. 25 M 1.58 H 1 20 M 1.36 15 M 1.12 4 h 12 M 0.79 LSR«0.18 H h $tyfedritij$ htringiomts 25 M 7.07 20M 6.11 15 M 4.13 LSR»I.36 FIG* 166. (continued) hkl OVERALL TftUl Animals ISM 25 M 20 M 9M *2M 6M 3M IM7 «*58 »2.48 (1.(8 11.00 8.32 7 06 1 I 1 I— _ ' - — — — H LSR*t.74 Shallow Chlroftomidat 6M 9M 3M ISR*0J2 L74 t.7! I.68 «•«<««•• »M t2M 6M fSM 3M UR*0.77 <70 3«33 2.98 2«47 t„0« I 1 I — 1 « 1 TiblfleWat 9M I5M |2M LSR«0.93 5-89 3.82 2.43 h 1 I \ P**t*poe,lQ eWhiM ISM 25 M 20 M «2 M 9M LSR*I.3I 12*63 9.27 9.22 8.78 5.22 H h Ottp Chironomldac 12 M 25 M 15M 20M LSR*2.8« 10.77 9.77 9.10 8.63 HMfrm tpp. 25 M 15 U 20 M 12 M LSR«0.2I W« 1.33 L20 0.97 Sf/MrUts **rtntto**$ 25M 20M ISM LSR »L36 6.60 &04 3.36 I -H I 1 F— [ FIG. 166. (continued) o U*2 2 2 middle region. However, S.. cfr. tvlus was ~150/m to ~500/m more abundant in the middle than in the north and south regions, respectively. Naidids at 6 m were significantly more abundant in the south (1085/nr) than in the middle (570/m2) or north (455/m2). Although comprising approximately the same proportion of the population, £.. affinis across the three regions at 12 m. The density in the north, middle and south was 5123/m , 5111/m and 4230/m , respectively. Pisidium spp. were significantly more abundant at 12 m in the north (964/m ) than in the middle (505/m ) and south (364/m ) regions. £. fallax and £.. casertanum comprised ~60? of the pisidia in the north region and were two to three times more abundant than those in the middle and south regions. The 15 m depth zone -- While total animals observed in the north (13247/m ) and south (13732/m ) regions were not different from each other at 15 m, the middle region (17865/m ) was significantly different from the other two regions (Tables 64-70, Fig. 165). Major taxonomic groups dominating in this depth zone were naidids, tubificids, chironomids '9 £. affinis. Pisidium spp. and £. heringianus. The significant difference noted in the regional distribution of total animal abundance was largely a function of the abundance of JP . affinis. £• affinis was significantly more abundant in the middle (12593/m ) than in the north (8775/m ) and south (8702/m ) regions. p Naidids in the south 149 1/m ) were not significantly different from those in the middle (509/m ) and north (297/m ) regions. However, the number of naidids in the middle was significantly higher than those occurring in the north region. JP. michiganensis was more abundant in the middle than either the north or south c £. simplex was very abundant in the south when compared to the other two regions „ There were no significant differences in abundance for tubificids and £. heringianus among regions at 15 m. 2 Chironomids in the south (164 /m ) were significantly more abundant than those in the middle (479/m ) and north (412/m ) regions. The primary difference among regions was a preponderance of £. fallax-gr. khk 2 ("300/m more) in the south. 2 Numbers of Pisidium spp. in the middle (1963/m ) and north (1733/m ) regions were significantly more abundant than those occurring in the south (1285/m ). P.. casertanum and £.. nitidum were the most numerous pisidia in all regions but were 1.4 to 2.4 times more abundant in the north and middle regions when compared to the south region. Thep20 m depth zone - — At 20 m total animal density in the south (12768/m ) was significant lypgreater than that found in the north (9278/m ) and middle (8120/m ) regions (Tables 64-70, Fig. 165). The dominant taxonomic forms at 20 m were chironomids, P.. affinis p Pisidium spp. and 5.. heringianus. The chironomids in the south (594/m ) were significantly more abundant than those occurring in the middle p (424/m ). The north had an abundance similar to both regions (551 /m ). There were no obvious species abundances that set the south apart from the other two regions. Generally, benthic species found in the south region tended to be slightly more abundant than those in the middle region at 20 m. There were no significant differences-in the distribution of P.. affinis across regions ( 5054-5963 /m ) at the 20 m depth contour. Pisidium spp. were significantly more abundant in the south (2066/m ) than the middle (854/m ) region^ Number of Pisidium spp. found in the north region at 20 m (1206/m ) was not different from either region „ The south region had twics as many £. nitidum and five times as many P.. conventus as there were in the north or middle regions. The north region had two to five times as many £.. casertanum as did the middle or south regions . S„ heringianus was significantly more abundant in the south (2909 /m) when compared to the north (2060/m )and middle (1182/m ) regions. The 25 m depth zone — At 25 m abundance of total animals was significantly greater in the2south 03399/m ) and north (13126/m ) than in the middle region (8375/m ) (Tables 64-70, Fig. 165). The major taxonomic groups dominating the 25 m depth zone were chironomids, £.. affinis . Pisidium spp. and £. heringianus . Chironomids in the north (691/m ) and south (667/© ) regions had significantly more animals than the middle region (418/m ). The middle region at 25 m tended to have slightly lower abundances of the same numerically important major taxonomic groups . 2 P.- affinis was significantly more abundant in the north £6360/m ) and south (6193/m ) regions than in the middle region (381 8/m ). Age composition of the population was similar in all three regions. kh5 Pisidium spp . were significantly more abundant in the north (2588/m ) and south (2685/m ) regions than in the middle region (1133/m ). P. casertanum and £,. nitidum were two to three times more abundant in the north and south regions than those in the middle region. In the south region P.. conventus was two to three times more abundant than those occurring in the other regions . There were no significant differences across the regions at 25 m for a. fterlwrtwnig (2748-3206/m ). MqlfrjLple ppmparisj.op? yjfrhin , region? acro?S <3epfrh ggpqs. The north region — The general pattern of abundance of animals in the north was that the average number of total animals at the 15 and 25 m depth zones were significantly higher than at the 9, 12 and 20 m depths . Total animal abundance at the 3 and 6 ra depths were significantly different from each other and significantly lower than densities observed at all other depths (Tables 64-70, Fig. 166). Abundance of shallow-zone chironomids was not significantly different between 3 and 6 m. Chironomids at 3 and 6 m were significantly more abundant than those at 9 m„ All depths were significantly different from each other when considering naidids, except for the 6 and 15 m depths zones, which were similar. Tubificids were significantly more abundant at 9 and 15 m than they were at 12 m» Average numbers of £e affinis found at all depths were significantly different from each other, except at 12 and 20 m, where densities were similar. Abundances of deep-zone chironomids were significantly higher at 12 and 25 m than at 15 m. Deep-zone chironomid abundance at 20 m was similar to abundances observed at the 12, 15 and 25 m depths. Average numbers of Pisidium spp. at all depths were significantly different from each other, except at 12 and 20 m, where densities were similar . Average numbers of 5. heringanus from all depth zones were significantly different from each other. The middle region ~ The general trend of benthic abundance in the middle region showed that the 15 m depth contour contained significantly higher numbers of total animals than any other depth zone. Abundance of total animals at the 9, 12, 20 and 25 m depths was similar. The 3 and 6 m depths were similar in numbers of animals observed and contained the lowest abundance of animals found at any depth zone in the middle region (Tables 64-70, Fig. 166). Abundance of shallow-zone chironomids was significantly higher at 9 m than at 3 and 6 m which had similar numbers of chironomids. Number of naidids found at 9 m in the middle region was significantly higher than those found in the 6, 12 and 15 m depth zones, which contained similar numbers of animals. Tubificids were significantly more abundant kke at 9 and 15 m than they were at 12 m. P.. affinis and Pisidium spp. had similar patterns in that average densities across depths in the middle region were significantly different except at 12 and 20 m. Deep-zone chironomids had no significant differences in abundance across observed depth zones. Abundance of ,§.. heringianus at 25 m was significantly higher than numbers observed at 15 and 20 m, where densities were similar. The south region — The general pattern of benthic abundance in the south region indicated that the 15, 20 and 25 m depth contours contained similar abundances of total animals and a significantly greater number of benthic macroinvertebrates than the remaining depth zones . Of the remaining depth zones the 9 and 12 m depths had similar abundances of total animals. Total animal abundances at the 3 and 6 m depths were significantly different from each other and significantly lower than densities at other depths (Tables 64-70, Fig. 166). Shallow-zone chironomids were significantly more abundant at 6 m when compared to those at 3 m. Shallow-zone chironomid abundance at 9 m was similar to abundances observed at 3 and 6 m. The density of naidids at the 6, 9 and 12 m depths were similar but significantly higher than numbers found at the 3 and 15 m depths. Numbers of naiads at 3 and 15 m depths were significantly different from each other. Tubificids were significantly more abundant at 9 and 15 m than they were at 12 m, Average abundances of £.. ^ffinis at all depths were significantly different from each other except at 20 and 25 m which had similar numbers of P.. affinis. The deep-zone chironomids had wide overlapping abundances among depth zones in the south region with only those at 15 m and 20 m having densities significantly different from each other. Densities of Pisidium spp. at all depth zones were significantly different from each other. Numbers of 5.. heringianus found at 20 and 25 m were similar, but significantly more abundant than densities observed at 15 m. lake Michigan - Pis*51 animals present in Pigeon Lake in various habitat types. Taxonomie determinations were carried as far as possible to aid in associating groups of animals with differing habitat types and to determine how many different forms of macroinvertebrates inhabited Pigeon Lake. Plgeop kpke - Western 9asjp Transect 1 - Station PL 11 — The first transect in the western basin of Pigeon Lake was PL 11 which had only one station (PL11). Station PL 11 was 7 m deep and was sampled as representative of the benthic community inhabiting the maximum depth found in Pigeon Lake. Sediments were composed entirely of silt and detritus. 2 Station PL 11 had more animals/m than any other station sampled in Pigeon Lake (Table 82). Mean abundance of total animals was 130168/m . The most numerous forms, tubificids and chironomids, comprised 97$ and < 3% of the total animals present, respectively (Table 83 ). When compared to other stations in Pigeon Lake, the second lowest number of taxa (19) occurred at PL 11 (Tables 82 and 84), and the largest number of tubificids were found at PL11; most were immature forms of tubificids. However, it is believed that these immatures were I±. hof fmeisteri . i,.. cervix and Tubifex tubifex. which were present in low abundance in the samples. Thus in 2-6 wks these three forms would the dominants. The most abundant identifiable tubificid was A.* pluriseta. The greatest number of JL. pluriseta. Peloscolex multisetosus multisetosus and £. multisetosus longidentis occurred at PL1 1 . Chironomus spp. was the most numerous chironomid at PL11. Transect 2 - Station PL24 ~ The deepest station along the second transect (PL2) was PL24 (5 m). Station PL24 was sampled as representative of the habitat at intermediate depths in Pigeon Lake. The environment sampled consisted of two sediment types. The first type (from replicates A and B) consisted of silty sand with considerable detritus . Sediments of replicate C were silt with some sand. Like PL11, this station did not have any aquatic macrophytes present. Station PL24 samples contained 44 taxa (Tables 82 and 84). Chironomids were the most species-rich group with 15. When compared to other stations, the greatest number of tubificid (11) and second greatest number of naidid taxa (10) occurred at PL24. Station PL24 located in the western end of thepWestern basin had the third greatest number of total animals ( 67776 /m ) and along with 452 CD O (U qO •H Oh O u w > 2 -p < c •H a CM w <: h lx »H tO a> r* a\ Nin *0 f*> OS •* os so to \o » «o to ~4 JO tO ft O SO OS to ** m cm r» OS r*. Os \Q NfMrt vO N 00 CO o r*. O OS M |X IX © OS © O en to «r rsj ^do «♦ p«» cm OS 00 «•> O ♦■* rt «o cm «n p* «*» © <* o««» o o» os o eft «<9H en en os to os »N flO'f 00 OS o OS CO s0 o. as as w ©, « _ • u cwc as 99 • a h O. « 09 Q.VM a • « 3 as as Ob SM a. o. 3 a u «as a, s CO 3 3 09 l« « a a o 3 "■4 i -< o a C *rs f9 0) u C (J u > 12 •m n "2 ° o T3 01 c t O T3 a 19 O O 3 >« ? * y u £X u C •73 ;?» cm -* cm WS iO OS OS m *-» IX O cm CM «■» n© en en «» «Sfl«l OS 00 O en r*. o o OS OS os os sr en so sr l*o OS » OS CM f"4 no en 00 i ,n. 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Results from sampling the littoral zone in the western end of the western basin of Pigeon Lake showed that habitat was substantially different from that of the other littoral zone stations mentioned previously. Differences in species composition observed between PL25 and PL31, etc. were likely due to habitat differences. Malacrustaceans and chironomids at PL25 (littoral zone - western basin) comprised only 32? of the total animal fauna while the major constituent there was tubificids (55$ of total animals). However, even though malacrustaceans occurred in low percentages at PL25, g^FlFflna? sp. and Asellus sp. occurred at their maximum abundance. Although there was ample vegetation at PL25, less vegetation was present compared with other littoral stations. As a result, it is suspected that the efficiency of the Ponar in obtaining a sample, not only of the vegetation but of the substrates, may have been increased at PL25. For kj2 the sake of comparison, assuming tubificids were the major constituents of the substrate, tubificid total was removed from the total animals at PL25, leaving malacrustaceans which comprised 40? and chironomids 30? of the total remaining animal population. Thus, PL25 compared favorably (70? malacrustaceans and chironomids) with other littoral-zone stations (PL31, etc.). Therefore, although PL25 appeared to be substantially different from other littoral-zone stations, suspected increased efficiency of the Ponar may have resulted in the differences noted which were mostly increased numbers of tubificids. The major differences observed in numbers and species of benthos between the stations were caused mostly by habitat type. Since the Ponar appeared to sample the substrate below vegetation inefficiently and did not effectively sample fast-swimming organisms; e.g., ephemeropterans, coleopterans and hemipterans, use of a sampling device or devices other than the Ponar may have more efficiently sampled the organisms and separate habitats. Pigeon Lftke - Sipm^ry In Pigeon Lake 7 of 13 stations sampled had a mean abundance of total animals that fell within the range 10000-50000 animals/m . Three stations (PL11, PL24 and PI 25) exceeded 50000 animals/m and three stations had fewer than 10000 animals/m (PL51,.PL52 and PLX2). While most sample sites were dominated numerically by chironomids (32-56? of the total animals present), four stations (PL11, PL24, PL25 and PL32) were dominated by tubificids (49-97? of total animals present) and one station (PL51) was dominated by g?rPflrv? sp. If malacrustaceans (Amphipoda and Isopoda) were pooled, then three stations (PL41, PL51 and PL53) were dominated numerically by this group * The most abundant chironomids in Pigeon Lake were the orthoclads, Cricotopus spp. Aside from unidentified immature tubificids, the identifiable tubificids comprising the greatest percentage of the total animal abundance in Pigeon Lake were Aulodrilus p^.urj.seta and Limnodrilus hoffmeisfreri. Other major components of the benthos in Pigeon Lake were the naidid, Nais variabilis: the leech, Helobdella gtagnaUa; the gastropod, AmrUQgla SP°5 the sphaeriids, Pisidium sop,: and the trichopteran family, Leptoceridae. There were 150 taxa identified from Pigeon Lake. While most stations (7 of 13) had between 30-60 taxa present, four stations (PL25, PLX1, PLX3 and PL53) had more than 60 taxa present and two stations (PL11 and PL32) had less than 30. Chironomids were the most diverse group present with 56 identifiably different forms, followed by trichopterans (24), naidids (20), tubificids (16), gastropods (7) and miscellaneous others (27). kJ3 The species list would be much greater had chironomids been identified beyond the genus level, which was not possible with present knowledge. In particular, the genus Crj.qotopus probably consisted of 10 or more different forms. However, since Cricotopus spp. were generally quite small and occurred in great quantities, taxonomic treatment could not be complete without further procedures beyond the scope of the study (i.e., rearing larva to adult stages). Finally, swift moving taxa would have increased the list of taxa present in Pigeon Lake and possibly at each station had another mode(s) of collection been used. Nevertheless, the study was able to collect a large number of taxa and produce quantitative results that will provide baseline data for future studies. kjh SCUBA OBSERVATIONS Introduction The following represents a compendium of physical and biological information obtained from seven SCUBA dives in Lake Michigan in the vicinity of the J, H, Campbell Plant 9 August 1977* Time of each dive and direction swum are presented in Table 86, while subsequent information details physical and biological characteristics associated with each station within a given transect. Black and white pictures were also taken along each transect documenting bottom configuration and any unique objects. These prints are available from the Great Lakes Research Division or Consumers Power, Environmental Services Division, Jackson, Michigan , Diving was performed to document unique fish-spawning areas or substrates prior to construction of the intake and discharge structures and to evaluate some existing physical, limnological and biological conditions in the lake. We also noted unique features such as irregular lake-bottom terrain, areas of locally increased turbidity and presence of rooted aquatic macrophytes. Use of SCUBA permits direct observation and hand-sampling of an area; data obtained may supplement or be correlated with data obtained during other (primarily mechanical) sampling efforts in the study area. Observations were made by John A, Dorr III, Gregory G, Godun and James A, Wojcik; all divers were aquatic biologists experienced in underwater survey, sampling and observational techniques. Description of each SCUBA Dive Dive No, 1 Diving Team: Dorr, Godun Location: future discharge canal transect (Fig, 6) Date: 9 August 1977 Time: 1540-1725 Duration: 105 min Estimated length of transect: 1000 m W to E 400 m N following 6 m contour Depth range: 12,2-5-2 m Secchi disc: 3,0 m Water temperature: 21,5 C surface, 21,5 C bottom same for all stations Air temperature: 26 C Cloud cover: overcast Wind: S, 8-16 km/hr Seas: SW, wave height 0,3 m Weather : rain UT5 TABLE 86. Summary of survey SCUBA dives performed in eastern Lake Michigan near the J. H. Campbell Plant, 9-10 August 1977. Times given (EST) are times of observation at each station* Date Time Dive No. Station Number Depth (m) Team 9 Aug 1544 1548 1557 1605 1616 1646 1655 1704 1 1 2 3 4 5 6 7 8 12.2 12.2 11.3 10.4 8.5 7.9 7.0 6.1 Dorr, Go dun (direction s shift, from E to N) 1710 9 5.2 1720 10 5.5 9 Aug 1805 1835 1845 1851 1856 2 1 2 3 4 5 10.4 9.5 8.5 7.0 6.1 Dorr, Wojik (direction shift, from E to S) 1904 6 5.8 1912 7 6.1 1917 8 6.1 10 Aug 1201 1219 1230 1240 1246 1316 1320 3 1 2 3 4 5 6 7 5.2 7.6 9.1 10.7 11.6 12.5 12.8 Dorr, Godun (direction shift, from W to S) 1341 8 11.9 10 Aug 1358 1410 4 1 2 8.5 8.8 Dorr, Wojcik 10 Aug 1431 1437 5 1 2 7.6 7.6 Dorr, Wo j cik 10 Aug 1505 1506 1515 6 1 2 3 12.2 11.0 10.7 Dorr, Woj cik 10 Aug 1604 1606 1614 1615 1622 1644 1645 1648 7 (d: (d: 1 2 3 Lrection 4 5 Lrection 6 7 8 shift, shift, 12.2 11.3 11.6 , from N to E" 10.7 11.0 , from E to N^ 9.1 8.8 8.8 Dorr, ) ) Wojcik U76 Station 1 - Time: 1544 Depth: 12.2 m Bottom: fine sand Organic detritus : Biological notes: few mm floe none Station 2 - Time : 1 548 Depth: 12.2 m Bottom: fine sand Organic detritus: Biological notes: few mm floe none Station 3 - Time: 1557 Depth: 11.3m Bottom: fine sand Organic detritus : Biological notes: few mm floe none Station 4 - Time: 1605 Depth: 10.4 m Bottom: sand " Organic detritus: Biological notes: few mm floe none Station 5 - Time : 1 6 1 6 Depth: 8.5 m Bottom: sand Organic detritus : Biological notes: few mm floe none Station 6 - Time: 1646 Depth: 7-9 m Bottom: sand Organic detritus: Biological notes: few mm floe none Station 7 - Time: 1655 Depth: 7*0 m Bottom: coarse sand, ripple marks larger than those observed at deeper stations Organic detritus: fine silt between ripple marks (several mm thick) 477 Biological notes : none Station 8 - Time: 1704 Depth: 6*1 m Bottom: coarse sand Organic detritus: fine silt between ripple marks (several mm thick) Biological notes: one dead crayfish, few clumps of aquatic macrophyte Mvriophvllum sp« (10-30 mm diameter) At this point in the transect (station 8), divers turned 90 degrees and swam north parallel to shore for approximately 400 m. Station 9 - Time: 1710 Depth: 5-2 m Bottom: coarse sand Organic detritus: none observed Biological notes : none Station 10- Time: 1720 Depth: 5*5 m. ' Bottom: fine sand Organic detritus: none observed Biological notes: none The following between-station observations were made: 1) Young-of-the-year (YOY) alewife 20-30 mm long were abundant • Numerous schools of 10-100 fish per school were seen. Many fish were observed darting and "snapping" (not coughing) which was interpreted to be feeding behavior. 2) Loose clumps of Mvriophvllum sp. were present in trace amounts at most stations 6 m or deeper. Clumps were small (10-30 mm diameter) and appeared randomly distributed . 3) Floe (fine organic detritus and sediment), a few milimeters thick, was observed at all stations, except stations 9 and 10. Where ripple marks were large, floe concentrated in troughs. 4) There was a distinct shift in sand grain size from fine to coarse (prodeeding shoreward) at approximately 7 m. In addition, ripple marks which were previously smaller and V78 asymmetric at deeper stations became larger (1-2 cm trough-to-crest, 15-20 cm crest-to-crest, 1-2 m long) and more symmetric. Dive No. 2 Diving Team: Dorr, Wojcik Location: south reference transect (Fig. 6) Date: 9 August 1977 Time: 1805-1917 Duration: 72 min Estimated length of transect: 800 m W to E 400 m N following 6 m contour Depth range: 10.4-5-8 m Secchi disc: 3.5 id Water temperature: 21.0 C surface, 21 ,0 C bottom same for all stations Air temperature: 26 C Cloud cover: overcast Wind: S, 0-8 km/hr Seas: SW, wave height 0 Weather: rain ending, 2 m skies clearing Station 1 - Time: 1805 Depth: 10.5 m Bottom: fine sand Organic detritus: few mm floe Biological notes: snails (Valvata sp„ ) abundant Station 2 - Time: 1835 Depth: 9-5 m Bottom: fine sand Organic detritus: Biological notes: few mm floe snails (Valvata sp.) abundant Station 3 - Time: 1845 Depth: 8.5 m Bottom: fine sand Organic detritus: Biological notes: few mm floe snails (Valvata sp . ) not as abundant as stations 1 and 2 U79 Station 4 - Time: 1851 Depth: 7.0 m Bottom: sand, less fine than stations 1 and 3 Organic detritus: few mm floe Biological notes: snails not observed Station 5 - Time: 1856 Depth: 6.1m Bottom: coarse sand Organic detritus: little Biological notes: none At this point (station 5) divers turned 90 degrees and swam south parallel to shore for approximately 400 m. Station 6 - Time: 1904 Depth: 5.8 m Bottom: coarse sand Organic detritus: little Biological notes: none Station 7 - Time: 1912 Depth: 6dm Bottom: coarse sand Organic detritus: little Biological notes: none Station 8 - Time: 1917 Depth: 6.1m Bottom: coarse sand Organic detritus: none Biological notes: none The following between-station observations were made: 1 ) Y0Y alewif e were abundant ; schooling was apparent 0 2) Small loose clumps of Mvriophvllum sp. were occasionally encountered. 3) Floe layer, bottom composition and zonation and ripple mark pattern paralleled that observed during Dive No» 1c 4) Occurrence and abundance of snails (Valvata sp„; stations 1 and 3) were unique to this dive. 480 Dive No. 3 Diving Team: Dorr, Godun Location: future intake transect (Fig. 6) Date: 10 August 1977 Time: 1201-1341 Duration: 100 min Estimated length of transect: 1000 m E to W 400 m N to S Depth range: 5-2-12.8 m Secchi disc: 4.0 m Water temperature: 25 C Air temperature: 26 C Cloud cover: partly cloudy Wind: SSW, 8-16 km/hr Seas: SW, wave height 0.3-0. Weather: clear 5 m Station 1 - Time: Depth: Bottom: 1201 5-2 m medium- fine sand, ripple marks 5-7 cm high, 10 cm apart 1-3 mm of floe in ripple mark troughs one alewife (25 mm) seen swimming near bottom Organic detritus: Biological notes: Station 2 - Time: 1219 Depth: 7*6 m Bottom: medium- fine sand, ripple marks Organic detritus: more floe than station 1 Biological notes: none Station 3 - Time: 1230 Depth: 9.1 m Bottom: medium- fine sand, ripple marks smaller, less pronounced, closer together (5-7 cm] than stations 1 and 2 Organic detritus: floe layer 4 mm thick many schools of small alewife (approximately 25 mm) swimming approximately 0.3 m from bottom, 10-20 fish/school Biological notes: 483 Station 4 - Time: 1240 Depth: 10.7 m Bottom: medium-fine sand Organic detritus: floe layer 4 mm thick Biological notes: numerous snail tracks observed Station 5 - Time: 1246 Depth: 11.6m Bottom: medium-fine sand Organic detritus: floe layer less thick than previous stations Biological notes: none Station 6 - Time: 1316 Depth: 12.5 m Bottom: fine sand, ripple marks indistinct Organic detritus: thin (1-2 mm) layer of floe Biological notes: log observed, approximately 10 cm diameter, 2-3 m in length Station 7 - Time: 1320 Depth: 12.8 m Bottom: fine sand Organic detritus: Biological notes: fine layer of floe none Station 8 - Time: 1341 Depth: 11.9m Bottom: fine sand Organic detritus: Biological notes: fine layer of floe none Between-station observations related to change in bottom composition, ripple mark pattern and accumulation of organic detritus paralleled those taken at previous transects (dive nos. 1 and 2). During this transect there was a marked improvement in horizontal visibility from the 5.2 m station (visibility less than 2 m) to the 10.7 m station (visibility 3 m) , despite increasing depth. Dive No. 4 Diving Team: Dorr, Wojcik 482 Location: 6 m contour perpendicular to future intake transect (Fig. 6) Date: 10 August 1977 Time: 1358-1415 Duration: 17 min Estimated length of transect: 200 m S to N Depth range: 8.5-8.8 m Secchi disc: 4.0 m Water temperature: 21.0 C surface and bottom same for all stations Air temperature: 25 C Cloud cover: partly cloudy Wind: SSW, 8-16 km/hr Seas: SW, wave height 0.3-0.5 m Weather: clear Station 1 - Time: 1358 Depth: 8.5 m Bottom: fine sand Organic detritus: floe layer relatively thick (3-5 mm) Biological notes: one tree branch observed Station 2 - Time: 1410 Depth: 8.8 m Bottom: fine sand, ripple marks 5-7 cm high, 7-10 cm apart Organic detritus: floe layer relatively thick (3-5 mm) Biological notes: none Dive No. 5 Diving Team: Dorr, Wojcik Location: 9 m contour, perpendicular to future discharge transect (Fige 6) Date: 10 August 1977 Time: 1431-1440 Duration: 10 min Estimated length of transect: 200 m N to S Depth range: 7.6 m Secchi disc: 4.0 m Water temperature: 21.0 C surface and bottom same for all stations Air temperature: 25 C U83 Cloud cover: partly cloudy Wind: SSW, 8-16 km/hr Seas: SW, wave height 0.3-0.5 m Weather: clear Station 1 - Time: 1431 Depth: 7*6 m Bottom: fine sand Organic detritus: Biological notes: thin layer of floe none Station 2 - Time: 1437 Depth: 7.6 m Bottom: fine sand Organic detritus: Biological notes: thin layer of floe none Dive No. 6 Diving Team: Dorr, Wojcik Location: 12 m contour, perpendicular to future discharge transect (Fig* 6) Date: 10 August 1977 Time: 1505-1520 Duration: 15 min Estimated length of transect: 200 m S to N Depth range: 12.2-10.7 m Secchi disc: 4.0 m Water temperature: 21.0 C surface and bottom same for all stations Air temperature: 25 C Cloud cover: partly cloudy Wind: SSW, 8-16 km/hr Seas: SW, wave height 0.3-0.5 m Weather: clear Station 1 - Time: 1505 Depth: 12.2 m Bottom: fine sand Organic detritus: Biological notes: 1-3 mm floe none Station 2 - Time: 1506 k8h Depth: 11.3m Bottom: fine sand Organic detritus: 1-3 mm floe Biological notes: none Station 3 - Time: 1515 Depth: 11,6m Bottom: fine sand Organic detritus: slightly more floe than stations 1 and 2, turbidity higher (visibility less than 1.2 m) Biological notes: one large (10 cm diameter) clump of aquatic macrophyte (Mvriophvllum sp.) observed Slight increase in turbidity noted from stations 1 to 3. Dive No. 7 Diving Team: Dorr, Wojcik Location: 12 m contour at reference location south of Campbell Plant (Fig. 6) Date: 10 August 1977 Time: 1604-1650 Duration: 46 min • Estimated length of transect: 200 m S to N 500 m W to E 200 m W to N Depth range: 12.2-8.8 m Secchi disc: 4.0 m Water temperature: 21.0 C surface and bottom same for all stations Air temperature: 25 C Cloud cover: partly cloudy Wind: SSW, 8-16 km/hr Seas: SW, wave height 0.3-0.5 m Weather: clear Station 1 - Time: 1604 Depth: 12.2 m Bottom: fine sand Organic detritus: 1-3 mm floe U85 Station 2 - Biological notes: none Time: 1 606 Depth: 11.3m Bottom: fine sand Organic detritus: Biological notes: Station 3 - 1-3 mm floe none Time: 1614 Depth: 11,6m Bottom: fine sand Organic detritus: Biological notes: 1-3 mm floe snails (Valvata sp.) abundant At this point (station 3) in the transect, divers turned 90 degrees and swam east (shoreward) for approximately 500 m. Station 4 - Time: 1615 Depth: 10.7 m Bottom: fine sand Organic detritus: Biological notes: 1-3 mm floe snails (Valvafra. sp.) abundant Station 5 - Time: 1622 Depth: 11.0m Bottom: fine sand Organic detritus: Biological notes: 1-3 mm floe snail less abundant At this point (station 5) in the transect, divers turned 90 degrees and swam from south to north for approximately 200 m. Station 6 - Time: 1644 Depth: 9.1 m' Bottom: fine sand Organic detritus: Biological notes: 1-3 mm floe snails (Valvata sp.) numerous Station 7 - Time: 1645 Depth: 8.8 m Bottom: fine sand k86 Organic detritus: 1-3 mm floe Biological notes: snails (Valvata sp.) numerous Station 8 - Time: 1648 Depth: 8.8 m Bottom: fine sand Organic detritus:: 1-3 mm floe Biological notes: snails (Valvata sp.) numerous Bottom composition was similar to that found at previous transects. Snails (Valvata sp.) were first observed outside station 3 (11.6 m) and were most abundant at stations 3 and 4 (11.6-10.7 m). Snail density decreased at stations 5-7 (11.0-8.8 m) , relative to stations 3 and 4. Sumwary 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, limnological 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 m 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 of silt were encountered, primarily offshore from the 7.5 m contour. Silt was often concentrated in troughs of ripple marks. (4) Substrate was entirely shifting-sand; rocks, gravel, clay and heavy silt were not encountered. (5) Ripple marks at stations deeper than 7.5 m 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 m contour shoreward, 487 (6) Bottom profile was flat and even; rises, depressions and sudden drop-off s were not encountered. Limnological 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 m 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 periphyton 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 Mvriophvllum 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 m contour; very little was observed at shallow (6.0 m) stations. 488 (6) Thousands of snails (Valvata spj were seen on the bottom within the south reference transects (dive nos. 2 and 7) between the 11.6 - 9.1 m 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. (8) Young-of-the-year alewives (20-30 mm TL) were observed at many but not all locations. Numbers were estimated to range from 1-30/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. Stations examined during our 9-10 August dive studies appeared physically and limnologically homogeneous. With few exceptions (occurrence of detrital material and concentrations of snails), stations also appeared to be relatively biologically homogeneous. No unique spawning habitats were identified. However several species of fish, most notably the alewife and spot tail shiner, would be expected to spawn in the vicinity of the Campbell Plant, as they do along most of the eastern Lake Michigan shoreline. From our previous experiences, we would expect yellow perch to spawn in specific areas away from the Campbell Plant. Other species, such as trout-perch, bloaters and slimy sculpins probably would use the area near Campbell for spawning purposes to some degree, but no large concentrations of fish would be expected. This area should be no more attractive than others along the shoreline . Rainbow smelt may be an exception, as the jetties, intake and discharge canal and their associated currents may be attractive to smelt during their spring spawning runs. If the future intake and discharge structures are built using riprap as many other plants along Lake Michigan have been, we would expect this rocky substrate to become attractive spawning habitat for slimy sculpins and johnny darters. In addition, some limited yellow perch spawning may also occur there. U89 GENERAL CONCLUSIONS This study was an attempt to characterize fish and benthos populations in a number of ecologically distinct habitats and try to relate their distributions to present and possible future effects of a power plant. Lake Michigan with its wide expanse of water and the associated coldwater fauna that inhabit it, is one habitat type* Pigeon Lake would be a typical inland lake with typical warmwater species complexes, were it not for the influence of Lake Michigan water and the Pigeon River on its ecology. Pigeon River adds yet another facet to the study picture, because of the reservoir of riverine organisms that inhabit its stretches, and ultimately exerts its effect on the composition and abundance of species living in Pigeon Lake. Our adult fish surveys in Lake Michigan have established that alewife, spottail shiner, rainbow smelt and yellow perch are seasonally common to abundant in the inshore region around the plant. Alewives dominate the inshore region starting in April with the first warming of inshore waters, then leave their myriad young behind after early summer. Both young and adults are an important aspect of the ecology of these waters . There was .tremendous diversity of fishes within Pigeon Lake, many species of which were not collected in Lake Michigan. This is probably due to the range of habitats available, abundant plant cover and seasonally warm temperatures. Immigration of typical Lake Michigan fish species into Pigeon Lake has important ramifications both because of influences on the biology of resident Pigeon Lake species and potential increases in entrainment . The adult species of fishes in both lakes interact with each other in many ways. It is suspected that many Lake Michigan fish, burbot, some salmonids (lake, brown and rainbow trout, Chinook and coho salmon), suckers (golden redhorse and white) and lake herring make spawning runs into Pigeon Lake; and others, such as yellow perch, spottail shiner and alewife succesfully reproduce in Pigeon Lake. One dilemma noted was that although gizzard shad were commonly impinged on traveling screens particularly in the fall and winter (Consumers Power 1975), very few were caught in our sampling gear. The mark and recapture study established that large numbers of northern pike and largemouth bass inhabit Pigeon Lake. These fish were utilizing the abundant food supply due in part to YOY produced by Lake Michigan fish species and the diverse habitat present in Pigeon Lake* Initial observations suggested that northern pike experience above average growth in Pigeon Lake. Considerable movement within Pigeon Lake was also noted for these large piscivores. U90 Fish larvae in Pigeon Lake, as expected, were quite abundant. The lake provides a sheltered environment in contrast to Lake Michigan and many species like alewives, spottail shiners and perch have been attracted there and successfully spawned. Very few larvae were collected in Lake Michigan during early June, when large numbers were collected in Pigeon Lake. Even during periods of maximum abundance of alewife larvae in Lake Michigan, we still observed higher concentrations of larvae in Pigeon Lake. The number of species of larval fish caught in Pigeon Lake were also quite high when compared to the few collected in Lake Michigan. Sled tows showed that high concentrations of spottail shiners inhabited the sandy inshore beach areas. Many other rarely captured larvae, like sculpins and trout-perch, were also taken with the sled. Rainbow smelt larval data suggested an interesting temporal distribution pattern. Newly-hatched larvae were present at offshore Lake Michigan stations in mid-June which was considerably later than the usual occurrence of larval smelt. Peak abundance of larval smelt was probably sometime in late April-May and presence of these larvae in mid-June was puzzling. We will continue to monitor this situation closely to document whether 1977 was an unusual year for rainbow smelt larvae . Another situation which was common for a number of larval fish species, was appearance of larvae at the north transect of stations in the area of the thermal discharge but none at the south reference transect. We believe the presence of larvae at the north transect was due to spawning by adult fish in the discharge canal. After hatching, larvae were apparently carried into Lake Michigan in the area of the thermal discharge, accounting for their appearance in north transect samples. Sampling and observation of the discharge canal in 1978 revealed that alewives were spawning there in abundance, carp YOY and small centrarchids were caught in minnow traps, spawning nests of some centrarchids were observed and adult white suckers were seen in the canal during their peak spawning period, A prevailing theme running throughout the larval fish data analysis was the earlier spawning by fish species in Pigeon Lake compared with Lake Michigan. "This phenomena resulted in dual peaks of larvae passing through plant intakes . Successive peaks of fish larvae in entrainment samples came from larval cohorts spawned in Pigeon Lake and then sometime later in Lake Michigan. This was clearly evident for the following major species: alewife, spottail shiner and yellow perch. Net avoidance biased results for all species. Factors such as macrophyte density and water turbidity, when coupled with net avoidance, resulted in different gear efficiencies among stations and between day and night. Species-specific differences were also noted. For example, the 491 frail, relatively slow-swimming larval alewives were collected over the entire larvae length range (0-25 mm) while more robust species like yellow perch (in Lake Michigan) were never collected at lengths over 9 mm. Of course, larger yellow perch were frequently captured in Pigeon Lake at night at stations which had turbid water and macrophytes. Daytime net avoidance by fish larvae prompts the recommendation that any calculations or generalizations about field concentrations of larvae should be based on night data for most species captured . Thus any calculations of potential entrainment impact due to the future offshore intake should use nighttime data. For some time periods and species (i.e., alewife in early June) both day and night data could be used to advantage . A wide discrepancy existed between the large number of taxonomic groups observed in the field larval fish collections and the few groups represented in entrainment samples. Possible causes might be limited dispersion by some groups, low abundance or misidentificationc Entrainment of fish larvae and fry at the Campbell plant was high during peak periods of larval abundance. Most larvae were entrained on the first sampling date (8 July) when over 4.5 million larvae in 24 hr passed through the plant. Undoubtedly, high entrainment values were also occurring in June. Values of over one million larvae per day were common through early August, but after 10 August entrainment rates dropped to less than 70,000/24 hr for the remainder of the year. Alewife, unknown cyprinids and rainbow smelt were the dominant larval groups entrained. Another 11 groups of larvae were also entrained, but in low numbers. We have observed unusually high concentrations of larvae in the intake canal. Concentrations there were higher than those observed in Pigeon Lake or Lake Michigan. We also found that many of the larvae entrained by the Campbell Plant were derived from larval populations in Lake Michigan. Evidence for this was the consistent entrainment of alewife larvae during times when few were present in areas of Pigeon Lake outside the influence of Lake Michigan. In addition, very few larvae of resident Pigeon Lake species were ever entrained, although they were abundant at our Pigeon Lake beach and openwater stations. Contradicting this general trend was that on two occasions, yellow perch and alewife larvae, that were only present in Pigeon Lake, were entrained in large numbers. Both of these occurrences were in the spring and may have been due to water flow changes in Pigeon Lake. In the spring, Pigeon River flow was high which may have caused most intake water to come from Pigeon Lake rather than Lake Michigan, as was the case later in the year. During summer and fall few Pigeon Lake endemic species were entrained. Peak numbers of fry entrained occurred later in the season, reflecting growth of larvae as the season progressed. The 8 August U92 period was the time of maximum entrainment of fry; most were alewife, but some smelt were also collected. After 8 August, some fry were collected during every sampling period through 28 November, the last time sampling was conducted in 1977. A general pattern of entrainment was established for each larval fish species. Some species (e.g., yellow perch, unknown minnows and spottails) were susceptible to entrainment for relatively short periods followed by a nearly total absence in entrainment samples. Others, like the alewife and rainbow smelt, were entrained over nearly half a year. Reasons for these species-related differences might be ontological, behavioral changes and habitat preference changes increasing with size and mobility. Apparently the pelagic nature of alewife and smelt resulted in increased probability of encounter with intake canal currents and subsequent entrainment. Diel activity patterns resulted In high nocturnal catches of rainbow smelt. Another common pattern observed was that many of the larvae entrained were relatively small, newly-hatched individuals, despite presence of a wide range of larger larvae in Pigeon Lake and Lake Michigan. This indicated that many species of larvae were relatively susceptible to prevailing water currents just after hatching and as a result vulnerable to entrainment. After working with the fish larvae data sets from Pigeon Lake and Lake Michigan and trying to understand the distribution and behavior of fish larvae species as they interact with the various water bodies and current processes occurring around the Campbell Plant , we were struck with the complexity of this ecosystem. Not only were there different species complexes in the three systems (Pigeon Lake, Pigeon River, Lake Michigan), but they spawned at different times and undoubtedly there was crossover spawning — Lake Michigan fish spawning and migrating to Pigeon Lake and vice-versa. Superimposed on this artificial system was the additional vector of entrainment and impingement mortality caused by the Campbell Plant. Two factors must be considered here. On the one hand, the plant was responsible for building the jetties (good new spawning habitat), they created a cold, clear source of oxygen-rich water which flows through Pigeon Lake (prevents stratification and attracts fish), built the intake and discharge canal (also new spawning habitat) and discharged heated water to Lake Michigan which creates favorable habitat for early spawning and attracts fish. On the other hand, the plant destroys a large number of larval and adult fish, cropping the organisms that come under the influence of its intake system. It may also stress or kill fish that are attracted into the discharge canal. In the final analysis , one must weigh the fact that the plant was not only responsible for the destruction of many fishes, but was also instrumental in creating and maintaining habitat favorable for fish reproduction which would not occur were the plant not there. As a U93 matter of historical fact , residents on the lake have noted that the Pigeon Lake outlet, before the plant reconstructed it for use as an inlet, was little more than a transient opening to Lake Michigan. Now it is maintained through dredging as a safe harbor and access point to Lake Michigan* These same residents have remarked on the improvement in sport fishing. Results of the benthos survey showed that high concentrations of the amphipod, Pontoporeia af finis, were observed at the 15 m depth contour in June. Other differences between the potentially affected area and reference areas north and south were documented by utilizing data on benthic community structure and composition. Patterns of benthic distribution at Campbell were similar in most respects to what has been observed elsewere in Lake Michigan, but differed in several aspects. One hypothesis suggested to account for the higher concentrations of benthic organisms at 15 m off Campbell is related to possible transport of detritus and nutrients from the discharge canal as well as the presence of an exposed layer of moraine in this area. The final study, SCUBA observations, has shown this part of the inshore region of Lake Michigan to be a fairly typical sandy, featureless habitat common to the eastern and southeastern shore of the lake. A few objects (sticks, logs), fish, snails and some detrital material were observed. No unique spawning habitat for fish was noted. Stations examined during our 9-10 August dive studies appeared physically and limnologically homogeneous. With few exceptions (occurrence of detrital material and concentrations of snails), stations also appeared to be relatively homogeneous biologically. No unique spawning habitats were identified. However, several species of fish, most notably the alewife and spottail shiner, would be expected to spawn in the vicinity of the Campbell plant, as they do along most of the eastern Lake Michigan shoreline. From our previous experiences, we would expect yellow perch to spawn in specific areas away from the Campbell Plant. Other species, such as trout-perch, bloaters and slimy sculpins probably would use the area near Campbell for spawning purposes to some degree, but no large concentrations of fish would be expected. This area should be no more attractive than others along the shoreline. Rainbow smelt may be an exception, as the jetties, intake and discharge canal and their associated currents may be attractive to smelt during their spring spawning runs. If the future intake and discharge structures are built using riprap as many other plants along Lake Michigan were, we would expect this rocky substrate to become attractive spawning habitat for slimy sculpins and johnny darters. 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R. 1967 • Age, growth and fecundity of the alewife, Alosa 506 pseudoharengu$ (Wilson), in Lake Michigan. Trans. Amer. Fish< Soc. 96:387-393- Nursall, J. R. 1973- Some biological interactions of spottail shiners (Notropis hwilggniVlg) , yellow perch (P3r cd 3 a. ?j y} •>•— \ ^ -a ^ en • S V* O •H J-i Q M-4 a a. cu g en • £ Vw c •H 5-» 0) 1-t ■u 03 Ctt 'M a 01 ■3 c. a-i u ^ •J 3 H CO 02 •J en C •H «5 U i-J 02 "3 cn io o m lOcMcMvOvo-vr^r-cf U T U > 1-^4 i.^« "O^ NU -si "Nf "*sl *+S >-« I «W ^W -LS l^» \A«/ 'w' V«/ • I • I . I .| • | o J • | . \ . | . | CS M CM OJ M CN >N fN H I O I H J CM i CM ! CM t ^ | fl | rH -H f— * r-i -H —l ■*H <— i —4 --* pH rH rH »H *H «H • 03 O CJ £ S S 6 S sense flflc:^c3P3wC3^wdf3f<3 UUUUUUUCJUUUUU C^ CSi oou^Ln<>*<»• \^S ^^ V^/ S.^ •>««• CJQW.-3 CJCJQQWW momo^OOtnmmoooo "-H'HOOonir,i- m un v.^ inmOi-ooou^oonor^Or^ cm cm ro O O c^i cni C4 m r— i ^r un P=* -a CD M 3 iJ cO 0) U o >>%>% >s co U. 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