The comparative growth and survival of a naturalized and aquaculture strain of rainbow trout

221 Pages·2013·1.9 MB·English

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

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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.

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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.

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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
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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
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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

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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

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