University of Alberta Assessing the effects of trout stocking on native amphibian communities in small boreal foothills lakes of Alberta By Candra Margaret May Schank A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Master of Science In Ecology Department of Biological Sciences Edmonton, Alberta Fall 2008 Library and Bibliotheque et 1*1 Archives Canada Archives Canada Published Heritage Direction du Branch Patrimoine de I'edition 395 Wellington Street 395, rue Wellington Ottawa ON K1A0N4 Ottawa ON K1A0N4 Canada Canada Your file Votre reference ISBN: 978-0-494-47406-8 Our file Notre reference ISBN: 978-0-494-47406-8 NOTICE: AVIS: The author has granted a non­ L'auteur a accorde une licence non exclusive exclusive license allowing Library permettant a la Bibliotheque et Archives and Archives Canada to reproduce, Canada de reproduire, publier, archiver, publish, archive, preserve, conserve, sauvegarder, conserver, transmettre au public communicate to the public by par telecommunication ou par Plntemet, prefer, telecommunication or on the Internet, distribuer et vendre des theses partout dans loan, distribute and sell theses le monde, a des fins commerciales ou autres, worldwide, for commercial or non­ sur support microforme, papier, electronique commercial purposes, in microform, et/ou autres formats. paper, electronic and/or any other formats. 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Canada Abstract Creating or enhancing recreational fisheries through sport-fish stocking is an accepted practice, but can also have negative concequences on the recipient ecosystem. I studied 11 boreal foothills lakes, 5 with and 6 without stocked trout. All lakes supported native forage fish and 3 amphibian species: wood frog (Lithobates sylvaticus), boreal chorus frog {Pseudacris maculata), and western toad (Anaxyrus boreas). To assess effects of stocking on amphibian populations, I examined the relative abundance and size of adults and young-of year, and timing of metamorphosis over 3 years. For wood frogs and western toads, none of these parameters differed significantly between stocked and unstocked lakes. However, adult boreal chorus frogs were significantly more abundant on unstocked lakes. Wood frog abundance and size differed between 11 fish-bearing lakes and a Ashless lake, suggesting fish presence, per se, affects frog populations. I conclude that generally, stocked trout are not affecting amphibian populations in Alberta's boreal foothills. Acknowledgments This study could not have occurred without the financial and in-kind support from Alberta Sustainable Resource Development (ASRD), Alberta Conservation Association (ACA), Industrial Post Scholarship NSERC, Alberta Conservation Association Grant Eligible - Conservation Fund, Canada Circumpolar Institute - C/BAR fund, and the Alberta Sport, Recreation, Parks, Wildlife Foundation Development Initiatives Fund. I would like to acknowledge and send out a thank you to several people for making this study possible. The staff at the Rocky Mountain House government building in Alberta Sustainable Resource Development and Alberta Conservation Association offices were incredibly supportive and accommodating by providing housing, field, computer, and file resources, as well as volunteering their time. In particular I would like to say thanks to Steve Herman (ASRD), Rocky Konynenbelt (ASRD), Rod Burns (ASRD) and Cory Rasmussen (ACA). I would also like to thank the Grazing Association, local anglers, the Kutz Family, and Mr. and Mrs. Taylor for allowing us to have access to their land and providing us with local knowledge of the area. I am forever grateful to my dearest friend and side-kick in this project, Leslie Nasmith, for all her hard work in and out of the field for the past three years. She was my rock and this study would not have been the same without her. I would also like to thank my family for their support over the years. Without their kind words and gentil pushes, none of this would have been possible. Also, special thanks goes out to all the hard working enthusiastic field assistants that I had over the last three years - Colette Feehan, Katie Thompson, Justin Hanisch, Chantelle Allen, Paul Giang, Alissa Moenting, Darryl Edwards, Andre Caron, and Teela Stroll. This study would not have been possible without all of you. Thank-you! I would also like to send out a special thanks to the many members of my committee and lab: Bill Tonn, Garry Scrimgeour, and Lee Foote, the Pasz-Tonn team. Oh, and I could never forget my bio-core friends, Stephanie Nakada, Sarah lord, and Amy Darling for their assistance and advice and for always being there for me. Even with all the support and advice I have gathered from my friends, I am thankful and would like to give a 5-star special thanks to my supervisor, Cindy for her guidance, insight, contributions and patience with all my "silly questions" over the past three years. TABLE OF CONTENTS ABSTRACT ACHNOWLEDGMENTS TABLE OF CONTENTS LIST OF TABLES LIST OF FIGURES 1. INTRODUCTION 1 1.1 Sport-Fish Stocking: Management and Human Benefits 1 1.2 Sport-Fish Stocking: Effects on Receiving Ecosystems 3 1.3 Sport-Fish Stocking: Effects on Native Amphibians 5 1.4 The Structure of this Thesis 9 2. STUDY AREA AND SPECIES 10 2.1 Terrestrial and Aquatic Features 10 2.2 Fish Assemblages 12 2.3 Study Species: Amphibians 13 2.3 Predictions: Concerning Effects of Stocked Trout on Amphibian Populations 13 3. METHODS 14 3.1 Limnological Characteristics 14 3.2 Amphibian Surveys 15 3.3 Data Analysis 19 4. RESULTS 22 4.1 Limnological Characteristics 22 4.2 Amphibian Assemblages 23 4.3 Call Surveys and Egg Mass Searches 23 4.4 Overview: Transect Surveys and Pitfall Trapping 24 4.5 Transect Surveys: Relative Abundance - Catch-per-unit-effort 25 4.6 Pitfall Array Trapping: Relative abundance - Catch-per-unit-effort 26 4.7 Body Size 27 4.8 Timing of Wood Frog Metamorphosis 29 4.9 Additional Analyses Comparing Stocked and Unstocked Lakes 29 4.10 Fish-Bearing and Fishless Treatments 30 5. DISCUSSION 31 5.1 Main Results 31 5.2 Habitat Features 32 5.3 Trout Diet: What are Trout Eating? 33 5.4 Calling Behaviour 34 5.5 Relative Abundances of Amphibians 36 5.6 Relative Abundance as Measured by Pitfall Array Trapping and Differences between Sampling Methods 38 5.7 Indirect Effects of Predation: Body Size and Development Patterns 40 5.8 Does Wood Frog Body Size Affect Predation Risk? 42 5.9 Lakes With and Without Fish 43 5.10 Lake and Year Effects 44 6. CONCLUSIONS 46 6.1 North American Fisheries 46 6.2 Alberta's Fishing Policy 47 6.3 Stocking as a Tool 47 6.4 Management Actions 48 6.5 Use of Fish Hatcheries 49 6.6 Stocking Decisions 50 6.7 Recommendations 50 8. LITERATURE CITED 54 APPENDICES 96 A Two methodology diagrams: A) Transect surveys and B) Pitfall trap array 96 B Table showing raw wood frog call survey data for 2006 97 C Presence/absence of adult and YOY wood frog, boreal chorus frog, western toad in transect surveys and pitfall traps 98 D Presence/absence of adult and (YOY) wood frog, boreal chorus frog, and western toad from transect surveys 98 E Adult and (YOY) wood frog mean ± SE SUL 99 F Number of adult female and male wood frogs in transects 100 G Number of adult male and female wood frogs, boreal chorus frogs and western toad pitfall array traps 101 H Adult and YOY wood frog, western toad, and boreal chorus frog transect CPUES for 1) 2005, 2) 2006, 3) 2007 102 I Means (± SE) for catch-per-unit-effort for all 3 species and two age classes 112 LIST OF TABLES Table 1 Physical characteristics of all 12 study lakes in the boreal foothills 68 Table 2 Information for 12 study lakes in the boreal foothills, Alberta, on stocking status, native and non-native species 69 Table 3 Stocking information for the 5 stocked study lakes 70 Table 4 Temperature and water chemistry of 12 small boreal foothills Study lakes 72 Table 5 Summary of the wood frog call and transect survey data from 2006, indicating the number of transects, point counts, and number of call codes observed in each rank index over the entire survey period 74 Table 6 Envrionmental parameter table showing means (± SE) and statistical test results for environmental parameters 75 Table 7 Occurrence on transects of adult and YOY of 3 species of amphibians at 5 stocked lakes and 5 or 6 unstocked lakes 76 Table 8 Summary of the number of wood frog egg masses. Egg masses counts are separated into three survey periods 77 Table 9 Summary of relative abundance Split-plot and Nested Anova outputs for 3 amphibian species and two age classes 78 Table 10 Summary of Wood frog Snout-Urostyle length Split-plot and Nested ANOVA output for two age classes 79 LIST OF FIGURES Figure 1 Mean (± SE) call Rank for adult male wood frogs in 2006.