The comparative growth and survival of a naturalized and aquaculture strain of rainbow trout (Oncorhynchus mykiss) in laboratory and whole-ecosystem experiments by Matthew T. Martens A Thesis submitted to the Faculty of Graduate Studies of The University of Manitoba in partial fulfillment of the requirements of the degree of MASTER OF SCIENCE Department of Biological Sciences University of Manitoba Winnipeg Copyright © 2013 by Matthew T. Martens i ii ABSTRACT This thesis investigates the comparative growth and mortality of a naturalized (wild) and domestic (aquaculture) strain of rainbow trout (Oncorhynchus mykiss) common to Lake Huron. I first conducted a laboratory-based experiment, comparing the growth rates of the two strains. Under optimal and competition treatments, the domestic strain achieved a body weight ~2x that of wild conspecifics. Next, I conducted a replicated, whole-ecosystem study comparing the same strains. Both strains experienced equally low survival and the domestic strain segregated into a fast-growing group, (~3x growth relative to the wild strain), and a slow-growing group that had a lower growth rate than wild trout. A high growth rate for fast-growing domestic trout was achieved by a reliance on high energy prey as well as through low metabolic costs relative to wild strains. Together, these results demonstrate that aquaculture strains of rainbow trout have greater growth potential relative to wild conspecifics and may outcompete them in nature. iii iv ACKNOWLEDGEMENTS Foremost I would like to thanks my advisor, Dr. Paul Blanchfield, whose patience and guidance has helped me to develop my skills as a well-rounded scientist through my graduate work. Secondly, I thank my committee members, Dr. Gary Anderson, Dr. Mark Hanson and Dr. Bob Devlin for your encouragement and suggestions throughout this process. I also wish to acknowledge Dr. Michael Rennie for his help and suggestions regarding modelling and statistics. Next, I would like to acknowledge all of the assistance I received from staff and students during the growth trials and the ELA experiments. I thank the ABEL lab at Lakehead University for overseeing and allowing us to conduct experiments at their facilities. I would like to thank Blair Wasylenko for giving up his time to feed and read stories to the rainbow trout. I would also like to thank Dorian fish hatchery and Cedar Crest farms for providing the fish for these experiments. I would especially like to thank Alex Wall. These studies could never have been undertaken without his knowledge, experience and work ethic, which benefited these experiments immensely. I am grateful for the personal funding and support through the Experimental Lakes Area Student Fellowship, Fisheries & Oceans Canada, the University of Manitoba’s Faculty of Science, Graduate Studies and Department of Biological Sciences. Next, I would like to thank my peers and laboratory, Lee Hrenchuk, Matt Guzzo, Jane Kirk and Jordan Matley for analytical and intellectual support. Finally, I would like to thank my parents and Kristin Macaulay for putting up with me through these years. v vi Table of Contents ABSTRACT ........................................................................................................... iii ACKNOWLEDGEMENTS .....................................................................................v LIST OF TABLES ...................................................................................................x LIST OF FIGURES .............................................................................................. xii CHAPTER 1. Introduction .....................................................................................1 1.1 Aquaculture ....................................................................................................1 1.2 Phenotypic characteristics of farmed and wild salmonids .............................5 1.2.1 Reproductive characteristics ....................................................................6 1.2.2 Growth .....................................................................................................9 1.2.3 Survival..................................................................................................10 1.3 Freshwater salmonid aquaculture in Canada ................................................12 1.4 Objectives .....................................................................................................15 1.5 Rainbow trout (Oncorhynchus mykiss) ........................................................16 1.5.1 Strains ....................................................................................................19 1.6 Project summary and design ........................................................................23 1.6.1 Growth trials (Chapter 2).......................................................................24 1.6.2 Whole-ecosystem experiment (Chapter 3) ............................................25 CHAPTER 2. Growth of aquaculture and wild strains of rainbow trout in a controlled laboratory-setting ..................................................................................33 2.1 Introduction ..................................................................................................33 2.1.1 Salmonid genotypes...............................................................................33 2.1.2 Growth rates ..........................................................................................33 2.1.3 Rainbow trout ........................................................................................34 2.1.4 Objectives ..............................................................................................37 2.2 Methods ........................................................................................................37 2.2.1 Experimental design ..............................................................................37 2.2.1.1 Treatment 1: Growth potential .......................................................38 2.2.1.2 Treatment 2: Growth under inter-strain competition .....................39 2.2.2 Daily condition monitoring ...................................................................40 2.2.3 Data collection .......................................................................................41 2.2.4 Data analysis ..........................................................................................42 2.2.5 Calculations ...........................................................................................43 2.2.6 Bioenergetics modeling to estimate consumption .................................45 2.3 Results ..........................................................................................................46 vii 2.3.1 Physical parameters ...............................................................................46 2.3.2 Mortality ................................................................................................46 2.3.3 Growth ...................................................................................................46 2.3.3.1 Treatment 1 ....................................................................................46 2.3.3.2 Treatment 2 ....................................................................................49 2.3.4 Comparison of growth between treatments ...........................................50 2.3.5 Feed consumption ..................................................................................50 2.4 Discussion ....................................................................................................51 2.4.1 Growth ...................................................................................................52 2.4.1.1 Optimal conditions .........................................................................52 2.4.1.2 Competitive environment/comparison to Treatment 1 ..................56 2.4.2 Feed consumption ..................................................................................58 2.4.3 Modeling predictions .............................................................................60 2.4.4 Conclusions and recommendations .......................................................61 CHAPTER 3. Relative growth and mortality of domestic and wild strains of rainbow trout in a whole-ecosystem experiment ...................................................84 3.1 Introduction ..................................................................................................84 3.1.1 Domestic salmonid escapes into natural systems ..................................84 3.1.2 Salmonid survival and growth studies ...................................................86 3.1.3 Aquaculture in Canadian Shield lakes ...................................................87 3.1.4 Chapter objectives .................................................................................89 3.1.4 Hypothesis .............................................................................................90 3.2 Methods ........................................................................................................90 3.2.1 Study lakes.............................................................................................90 3.2.2 Limnological conditions ........................................................................91 3.2.3 Rainbow trout stocking procedure.........................................................93 3.2.4 Survival..................................................................................................95 3.2.4.1 Rainbow trout sampling .................................................................95 3.2.4.2 Avian predation ..............................................................................97 3.2.4.3 Population estimation.....................................................................98 3.2.5 Growth ...................................................................................................99 3.2.5.1 Stomach contents analysis ...........................................................100 3.2.5.2 Stable isotope analysis (SIA) .......................................................102 3.2.5.3 Bioenergetics and mercury mass balance modeling ....................106 3.2.5.4 Prey energy density ......................................................................108 3.2.5.5 Methyl-mercury (MeHg) determination ......................................109 3.3 Results ........................................................................................................111 3.3.1 Limnological conditions ......................................................................111 3.3.2 Rainbow trout recaptures .....................................................................112 3.3.3 Avian predation ...................................................................................112 3.3.4 Survival................................................................................................114 3.3.5 Growth .................................................................................................114 viii 3.3.5.1 Individual growth .........................................................................115 3.3.5.2 Stomach contents analysis ...........................................................116 3.3.5.3 Stable isotope analysis (SIA) .......................................................117 3.3.5.4 Bioenergetics................................................................................118 3.4 Discussion ..................................................................................................119 3.4.1 Survival................................................................................................120 3.4.2 Growth .................................................................................................125 3.4.2.1 Bioenergetics modeling ...............................................................129 3.4.3 Conclusions .........................................................................................131 CHAPTER 4. Synthesis ......................................................................................158 3.4.1 Survival................................................................................................158 3.4.2 Growth .................................................................................................159 3.4.3 Future direction ...................................................................................163 APPENDIX 1. Model input calculation and stable isotope sample list ..............167 A1.1 MeHg calculation ....................................................................................167 A1.2 Energy density calculation ......................................................................168 APPENDIX TABLES ........................................................................................169 APPENDIX FIGURES ......................................................................................177 APPENDIX FIGURES ......................................................................................178 ix LIST OF TABLES Table 1.1 List of studies examining differences in phenotype between artificially selected salmonids (domestic; D) compared to wild (W) conspecifics.................26 Table 2.1 Size, condition and variation in mass of wild and domestic strains of rainbow trout fed to satiation (treatment 1). Data represent x¯ ± 1 S.D. from three replicate tanks (n = 3) each containing 30 fish…………………………………..63 Table 2.2 Standardized growth and feed efficiency measurements of wild and domestic strains of rainbow trout fed to satiation (treatment 1); TGC = thermal growth coefficient (multiplied by 1000 to bring to unity); SGR = specific growth rate; FCR = feed conversion ratio. FCR data represent the x¯ ± 1 S.D. All data is calculated from three replicate tanks (n = 3) each containing 30 fish. Total values are calculated from measurements taken on day 0 and day 102 of the experiment……………………………………………………………………..…64 Table 2.3 Input parameters for bioenergetics model. ………………...…….…...65 Table 2.4 Size, condition and variation in mass of wild and domestic strains of rainbow trout fed a reduced ration and reared in same tanks (treatment 2). Data represent the x¯ ± 1 S.D. from three replicate tanks (n = 3) each containing 15 fish.…………………………………...................................................……….….67 Table 2.5 Standardized growth and feed efficiency measurements of wild and domestic strains of rainbow trout fed to satiation (treatment 1); TGC = thermal growth coefficient (multiplied by 1000 to bring to unity); SGR = specific growth rate. Data is calculated from three replicate tanks (n = 3) each containing 30 fish. Total values are calculated from measurements taken on day 0 and day 102 of the experiment………………………………………………………...………....…...68 Table 3.1 Total gillnet hours fished for Lake 303 and Lake 304 at the Experimental Lakes Area in 2011. Gillnet hours is a product the total number of hours a gillnet was fishing in a lake by the number of nets set in the lake…………….…………………………………..…………………….……...132 Table 3.2 Estimated survival (total number of remaining fish remaining) in Lake 304 at the Experimental Lakes Area in 2011 based on a formula for probability of recapture (Biro et al. 2003) of a specific fork length of a rainbow trout.......…..133 Table 3.3 Initial mass (g) and fork length (mm) ± 1 S.D. of wild and domestic strains of rainbow trout stocked into Lake 303 and Lake 304 at the Experimental Lakes Area on June 25, 2011. Differences in size were determined by a Student's t test for equal variance…………………………………………………...…..….134 x