Appendix E Gutsch (2017) Ruffe Study Dissertation The rise and fall of the Ruffe (Gymnocephalus cernua) empire in Lake Superior A DISSERTATION SUBMITTED TO THE FACULTY OF UNIVERSITY OF MINNESOTA BY Michelle Kathleen Gutsch IN PARTIAL FULFILLMENT OF THE REQUIREMENTS OF THE DEGREE OF DOCTOR OF PHILOSOPHY Dr Joel C Hoffman, Advisor December 2017 ©Michelle Gutsch 2017 Acknowledgements Thank you to all of the people that compiled and shared data with me— Henry Quinlan and Jared Myers (US Fish and Wildlife Service), Andrew Edwards (1854 Treaty Authority), Deserae Hendrickson (MN Department of Natural Resources), Bradley Ray (WI Department of Natural Resources), Mark Vinson and Lori Evrard (US Geological Survey), and Derek Ogle, Randy Lehr, and Matt Hudson (Northland College) Thank you to Greg Peterson, Chelsea Hatzenbuhler, Leah Mohn, Rob Skalitsky, and Will Bartsch for field and lab assistance Thank you to Anne Cotter for stable isotope processing Thank you to Cindy Hagley and local and regional educators associated with MN Sea Grant programming for help collecting and processing samples Thank you to Will Bartsch and Matt Etterson for R and stats help and support Thank you to Nate Nibbelink and Matt Etterson for Maxent help and support A special thank you to Jonathan Launspach for amazing GIS work on multiple chapters of the dissertation Thank you to Lyle Shannon and Paul Bates for teaching support and mentoring Thank you to the Integrated Biosciences and Biology Departments for financial and educational support Thank you to my committee—Matthew Etterson, Thomas Hrabik, Donn Branstrator—and to my academic advisor, Joel Hoffman I would also like to thank my office mates for scientific and emotional support— Jill Scharold, Chelsea Hatzenbuhler, Julie Lietz, and Christy Meredith Special thank you to my friends and family for incredible support—husband (Charles Gornik), Baby Maggie, Mom (Holly Gutsch), Dad (Mike Gutsch), Sister (Bonnie Gutsch), Emily Heald, Chelsea Hatzenbuhler, and Dogs (Rascal and Zoey) i Dedication I dedicate this dissertation to my husband and Baby Maggie Thank you for your love and support throughout this endeavor ii Abstract Invasive species are a global problem, impacting property, habitats, ecosystem function, and native species Our ability to predict future habitat and spread of aquatic invasive species is limited because it is challenging to collect and integrate information regarding life history, movement, and habitat, especially across continents Invasive Ruffe (Gymnocephalus cernua) has caused substantial ecological damage in North America, parts of Western Europe, Scandinavian countries, and the United Kingdom Given the potential for ecological impacts, such as native fish declines, ongoing concern regarding the spread of Ruffe is warranted But there are significant research gaps regarding life history, movement, and Ruffe distribution in the native and non-native range Therefore, the overall goals of my dissertation were to acquire life stage-specific data for Ruffe, including dispersal, seasonal, and spawning movements, and characterize their life cycle, and to develop a lake-scale species distribution model for Ruffe at a 30-m resolution First, I found that Ruffe exhibits plasticity with regard to chemical, physical, biological, and habitat requirements (Chapter One) Adult Ruffe has characteristics that allow it to adapt to a range of environments, including rapid maturation, relatively long life and large size, batch spawning, genotypic and phenotypic plasticity, tolerance to a wide range of environmental conditions, broad diet, and multiple dispersal periods Notably, there is variability among these characteristics between the native, non-native North American, and European non-native populations Second, I found that Ruffe populations in both the St Louis River and Chequamegon Bay are at different invasion stages (Chapter Two) In the St Louis River, the population iii increased from the initial invasion in 1986 up to 1995 and has been in decline for the past two decades (1996-2015) In Chequamegon Bay, the overall population is increasing, but is doing so by oscillating every 5-7 years I concluded that Ruffe populations in both systems partially conform to the typical “boom-bust” patterns seen with other invasive fish species Third, carbon and nitrogen stable isotope ratios (13C, 15N) revealed size-specific movements between coastal wetland and Lake Superior I found significant differences in δ13C and δ15N values between Ruffe captured in Lake Superior and those captured in the St Louis River, but not among locations within the river (Chapter Three) I found size-based differences as well; medium-sized fish, 60-80 mm standard length (SL), had a δ13Clipid corrected of about -25‰ to -45‰, lower than either small (