WALLEYE HABITAT USE, SPAWNING BEHAVIOR, AND EGG DEPOSITION IN SANDUSKY BAY, LAKE ERIE Thesis Presented in Partial Fulfillment of the Requirements for the Degree Master of Science in the Graduate School of The Ohio State University By Adam L. Thompson, B.S Graduate Program in Evolution, Ecology, and Organismal Biology The Ohio State University 2009 Thesis Committee: Dr. Elizabeth Marschall, Advisor Dr. Andrew Roberts Dr. Stuart Ludsin Copyright by Adam L. Thompson 2009 ABSTRACT Understanding habitat selection in fish can reveal areas critical for a population’s continuation in the ecosystem. In systems experiencing habitat alterations or reductions in population sizes, identifying habitat use takes on increased importance. To facilitate our understanding of potential factors limiting the success of walleye (Sander vitreus) in Sandusky Bay, Lake Erie, we combined walleye locations determined from radio telemetry with habitat predictor variables to model habitat use and reveal sex-specific patterns of habitat use throughout the spawning season (Chapter 2). Models revealed that the presence of preferred walleye spawning substrate, gravel and cobble, was an important predictor of walleye locations during the entire spawning season, and depth and distance from shore were important particularly prior to the spawn. In examining sex-specific patterns of habitat use, we discovered that males were more likely to occur over gravel and cobble substrates than females. We hypothesize that males establish position in these areas in anticipation of spawning females. Only a small proportion of walleye tagged in Sandusky Bay migrated to upstream spawning grounds (2 of 197; 1%). To confirm whether ii walleye spawning occurs in Sandusky Bay and to analyze how spawning substrate might affect egg deposition rates and viability, we compared eggs collected using spawning mats from gravel/cobble and sand/silt substrates (Chapter 3). Egg deposition and egg viability were not significantly different between substrates, and the majority of walleye eggs were collected from one site that contained gravel and cobble. The combined results of this investigation reveal that the Sandusky Bay is a spawning ground for walleye and that preferred spawning substrate is an important factor predicting the location of walleye during the spawn. Because the amount of spawning habitat in this system has declined by an estimated 92% during the past century, we recommend that conservation and restoration steps be taken to preserve this walleye spawning population. iii ACKNOWLEDGEMENTS This work was made possible through the extraordinary effort by multiple people. First, I would like to thank my advisor, Dr. Libby Marschall, for her continual support, advice, and patience. I am also grateful for Drs. Andy Roberts, Stu Ludsin, and Roy Stein for providing valuable recommendations and revisions that enhanced the quality of this project. Additionally, I would like to thank those individuals at the Aquatic Ecology Lab who helped in the field and in the lab and answered my many questions. I would especially like to thank Geoff Hosack, Cassie May, Alex Johnson, Joe Conroy, Jason Van Tassell, Paris Collingsworth, Kevin Pangle, Jahn Kallis, Kevin Donner, Emily Sopkovich, Bryan Kinter, Megan Nims, Josh Vidmar, and Josh Hatch. I am also indebted to Melissa Marburger, Margarita Talavera, Barb Fate, and Faith Haleem for their many administrative efforts. Mike Sovic generously offered his time and expertise with genetic analyses. Numerous members of the Ohio Division of Wildlife made significant contributions to this project in terms of funding, field collections, and intellectual input during project scoping meetings. I am especially grateful to Roger Knight, Jeff Tyson, Eric Weimer, Travis Hartman, Chris Vandergoot, Stephanie Shaw, iv and Jason Ross. Joe Barber and Ohio Department of Transportation pilots made it possible to conduct aerial surveys. Access to sites was provided by Jim Johnson and Joe Flahiff (City of Fremont), the River Cliff Golf Course, and the Tackle Box Restaurant. Frank Lopez supplied housing at the Old Woman Creek dormitories during the field season. Ken Buehler and Darryl Trent cooperated extensively with us during fish collections. Ed Roseman offered egg sampling advice. Further, I would like to thank Scudder Mackey, Dale Liebenthal, Don Guy, and many members of the Ohio Geologic Survey, including Erik Venteris, Mark Jones, Jim McDonald, and Greg Schumacher for their assistance with substrate analyses and collections. Finally, I would like to thank my parents, Al and Kathy, for everything that they have done. v VITA July 13, 1984………………........Born - Ames, Iowa, USA 2007………………………………Colorado State University, Fort Collins, Colorado, USA B.S. Fishery Biology, cum laude 2007 to present……………….....Graduate Research Associate, Department of Evolution, Ecology, and Organismal Biology The Ohio State University, Columbus, Ohio, USA FIELDS OF STUDY Major Field: Evolution, Ecology, and Organismal Biology Specialization: Aquatic Ecology vi TABLE OF CONTENTS Page Abstract ................................................................................................................. ii Acknowledgements. ............................................................................................. iv Vita ....................................................................................................................... vi List of Tables ........................................................................................................ ix List of Figures ....................................................................................................... x Chapters: 1. Introduction ................................................................................................ 1 2. Habitat use and spawning behavior of walleye in Sandusky Bay, Lake Erie ................................................................................................... 3 2.1 Introduction .......................................................................................... 3 2.2 Methods ............................................................................................... 6 2.2.1 Study site ............................................................................... 6 2.2.2 Study species ......................................................................... 6 2.2.3 Capture and tagging .............................................................. 7 2.2.4 Tracking ................................................................................. 9 2.2.5 Habitat variables .................................................................. 10 2.2.6 Model development .............................................................. 11 2.2.6.1 Abiotic habitat model .............................................. 12 2.2.6.2 Individual traits model ............................................ 13 2.3 Results ............................................................................................... 15 2.3.1 Walleye locations ................................................................. 15 vii 2.3.2 Abiotic habitat model ............................................................. 15 2.3.3 Individual traits model ........................................................... 16 2.4 Discussion ......................................................................................... 17 3. Spawning documentation and the influence of spawning substrate on walleye eggs in Sandusky Bay, Lake Erie .............................................. 23 3.1 Introduction ........................................................................................ 23 3.2 Methods ............................................................................................. 25 3.2.1 Egg collections ..................................................................... 25 3.2.2 Sample processing and statistical treatment ........................ 26 3.3 Results ............................................................................................... 28 3.4 Discussion ......................................................................................... 29 References ......................................................................................................... 32 Appendix A. Tables and figures .......................................................................... 42 Appendix B. Compilation of habitat data ............................................................. 62 Appendix C. Historical substrate of Sandusky Bay ............................................. 65 viii LIST OF TABLES Table Page 1. Correlation coefficients (r2) of model parameters: depth (m), distance from shore (m; “distance”), and substrate (1 = gravel and cobble present; 0 = gravel and cobble absent).........................................................................43 2. Parameter coefficients and corresponding p-values from logistic regression for pre-spawn, peak-spawn, and post-spawn time periods. The model predicted the presence/absence of walleye in an individual cell in relation to depth (m), distance from shore (m), and substrate (1 = gravel and cobble present; 0 = gravel and cobble absent.......................................................................................................44 3. Parameter coefficients and corresponding p-values from logistic regression taken across all time periods. The model predicted the presence/absence of walleye over gravel and cobble in relation to an