Northern Michigan University NMU Commons All NMU Master's Theses Student Works 5-2016 DIET ANALYSIS OF NATIVE AND NON- NATIVE JUVENILE SALMONIDS IN A LAKE SUPERIOR TRIBUTARY Alexis C. Growe-Raney Northern Michigan University, [email protected] Follow this and additional works at: https://commons.nmu.edu/theses Part of the Life Sciences Commons Recommended Citation Growe-Raney, Alexis C., "DIET ANALYSIS OF NATIVE AND NON-NATIVE JUVENILE SALMONIDS IN A LAKE SUPERIOR TRIBUTARY" (2016). All NMU Master's Theses. 81. https://commons.nmu.edu/theses/81 This Open Access is brought to you for free and open access by the Student Works at NMU Commons. It has been accepted for inclusion in All NMU Master's Theses by an authorized administrator of NMU Commons. For more information, please contact [email protected],[email protected]. DIET ANALYSIS OF NATIVE AND NON-NATIVE JUVENILE SALMONIDS IN A LAKE SUPERIOR TRIBUTARY By Alexis C. Growe-Raney THESIS Submitted to Northern Michigan University In partial fulfillment of the requirements For the degree of MASTER OF SCIENCE Office of Graduate Education and Research May 2016 SIGNATURE APPROVAL FORM Title of Thesis: DIET ANALYSIS OF NATIVE AND NON-NATIVE JUVENILE SALMONIDS IN A LAKE SUPERIOR TRIBUTARY This thesis by Alexis C. Growe-Raney is recommended for approval by the student’s Thesis Committee and Department Head in the Department of Biology and by the Assistant Provost of Graduate Education and Research. ________________________________________________________________________ Committee Chair: Dr. Jill Leonard Date ________________________________________________________________________ First Reader: Dr. Patrick Brown Date ________________________________________________________________________ Second Reader: Dr. Ashley Moerke Date ________________________________________________________________________ Department Head: Dr. John Rebers Date ________________________________________________________________________ Dr. Robert J. Winn Date Interim Assistant Provost of Graduate Education and Research ABSTRACT DIET ANALYSIS OF NATIVE AND NON-NATIVE JUVENILE SALMONIDS IN A LAKE SUPERIOR TRIBUTARY By Alexis C. Growe-Raney Introductions of Pacific salmonids to the Great Lakes and their tributaries have caused concerns about potential competition with native brook trout (Salvelinus fontinalis) of the region. My research evaluated the diet of five fish size categories (FSCs) of brook trout, non-native steelhead trout (Oncorhynchus mykiss), and coho salmon (Oncorhynchus kisutch) in a tributary of Lake Superior by using diet overlap and selectivity indices as measures of potential competitive interactions. Stomach contents and drift were analyzed for seven months in three habitat areas of the study stream. Stomach contents were obtained from 643 fish and yielded 6245 prey items, the majority (76.3%) of which were aquatic. Diet overlap analysis included 8372 comparisons between individual fish and 42.63% of these comparisons had an index value of 0.0, meaning that the two individuals did not have a single prey item in common. Results suggest that niche differentiation has occurred among the three fish as indicated by the low diet overlap index values between interspecific pairings of FSCs and differences in the selectivity values for the most common prey items in the drift and diet among the FSCs. While this study provides evidence of the ability of native brook trout to persist in the presence of non-native Pacific salmonids in Great Lakes tributaries, it also suggests that this sympatry has costs for the native brook trout. i Copyright by Alexis C. Growe-Raney 2016 ii DEDICATION This study is dedicated to the waters of the Upper Peninsula, the creatures that live in them, and the people who love them. I also dedicate this work to my parents who nurtured my curiosity and appreciation for “endless forms most beautiful and most wonderful”. iii ACKNOWLEDGEMENTS This research was made possible by funding from the National Park Service, Northern Michigan University's Excellence in Education Grant, and the Fred Waara Chapter of Trout Unlimited. This project would not have been remotely possible without the help of a small army of fish aficionados. I give heartfelt thanks to my advisor, Dr. Jill Leonard, and committee members, Dr. Patrick Brown and Dr. Ashley Moerke; my fellow NMU Fish Lab members including Julie Howard, Joseph Gerbyshak, Chris Gagnon, Kevin Duby, Chris Kovala, Rob Cross and Donald Danesi; the National Park Service staff of PIRO; members of Fred Waara Chapter of Trout Unlimited; and countless of unsuspecting undergraduate/graduate students, NMU faculty, citizens, and friends. This thesis follows the format required by the Canadian Journal of Fisheries and Aquatic Sciences (CJFAS) and Northern Michigan University’s Department of Biology and the Office of Graduate Education and Research. iv TABLE OF CONTENTS List of tables .................................................................................................................................. viii List of figures .................................................................................................................................. ix List of abbreviations ..................................................................................................................... xiii CHAPTER ONE: DIET ANALYSIS OF NATIVE AND NON-NATIVE JUVENILE SALMONIDS IN A LAKE SUPERIOR TRIBUTARY .............................................................................................. 1 INTRODUCTION ....................................................................................................................... 1 Methods ....................................................................................................................................... 5 Study Site .................................................................................................................................. 5 Experimental Design ................................................................................................................ 6 Habitat metrics......................................................................................................................... 7 Available forage from the drift................................................................................................. 8 Fish metrics ............................................................................................................................ 11 Diet analysis........................................................................................................................... 13 Results ....................................................................................................................................... 15 Habitat Metrics ...................................................................................................................... 15 Available forage from the drift............................................................................................... 17 Fish metrics ............................................................................................................................ 20 Diet analyses .......................................................................................................................... 23 Discussion ................................................................................................................................. 42 Available forage ..................................................................................................................... 43 Diet analysis........................................................................................................................... 47 Habitat use and fish distribution ............................................................................................ 50 Summary ................................................................................................................................ 56 Works cited ............................................................................................................................. 119 Appendices .............................................................................................................................. 129 Appendix A: Taxonomic classification of prey categories found in drift and stomach samples ................................................................................................................................ 129 Appendix B: Previously published body length-biomass regressions used to calculate biomass of individuals found in drift and stomach samples ................................................ 136 Appendix C: Body length-head width regressions calculated from drift samples ............... 142 Appendix D: NMU IACUC Protocol # 152 ..................................................................... 143 v Appendix E: Count of each prey category found in drift samples by month and habitat .... 144 Appendix F: Count of each prey category found in stomach samples by month and habitat .................................................................................................................................. 154 Appendix G: Proportions (%N, %W, FO%) of prey categories found in the diet of the five fscs by month ........................................................................................................................ 166 vi LIST OF TABLES Table 1: Prey size, life stage, prey source categories and prey occurrence