BIOECONOMICS IN AQUACULTURE. PRELIMINARY ANALYSIS OF THE CU_LTURE POTENTIAL OF THE FRESHWATER ANGELFISH- PTEROPHYLLUAISCALARE by Shane Willis, B. App. Sc., Grad. Dip. App. Sc. (Aqua). A thesis submitted in fulfilment of the requirements for the degree of Master of Applied Science. Department of Aquaculture University of Tasmania, at Launceston. July 1995.
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BIOECONOMICS IN AQUACULTURE.
PRELIMINARY ANALYSIS OF THE
CU_LTURE POTENTIAL OF THE
FRESHWATER ANGELFISH-
PTEROPHYLLUAISCALARE
by Shane Willis, B. App. Sc., Grad. Dip. App. Sc. (Aqua).
A thesis submitted in fulfilment of the
requirements for the degree of
Master of Applied Science.
Department of Aquaculture
University of Tasmania, at Launceston.
July 1995.
DECLARATION AND AUTHORITY
OF ACCESS
I certify that this dissertation contains no material which has been accepted for the award of
any other degree or diploma in any institute, college or university and that to my knowledge
and belief, it contains no material previously published or written by another person, except
where due reference is made in the text of the dissertation.
Shane Willis.
July 1995.
This thesis is not to be made available for loan or copying for two years following the date
this statement was signed. Following that time the thesis may be made available for loan and
limited copying in accordance with the Copyright Act 1968.
Shane Willis.
November 20, 1995.
ACKNOWLEDGMENTS
I would like to sincerely thank my research supervisors, Professor Nigel Forteath, Professor
Owen McCarthy and Dr. Jacqueline Flint for their advice and encouragement during my
work for this thesis.
Thanks also to Mr. Rick Datodi who has also been a great help, particularly with industry
infmmation. Thank you also to my family, particularly my father Greg and sister Louise, for
assisting me during my experiments and persevering with me during my research.
Thankyou to Mandy Reeves who has been so patient and understanding over the past months
while I have been completing my thesis.
I would also like to dedicate this work to the memory of my grandmother, Joyce Stewart,
who sadly passed away while I conducted this study.
11
TABLE OF CONTENTS
Page
DECLARATION AND AUTHORITY OF ACCESS ..................... .
ACKNOWLEDGMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . u
TABLE OF CONTENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . m
LIST OF FIGURES V111
LIST OF TABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . X
ABSTRACT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Xlll
CHAPTER 1. INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Bioeconomics in aquaculture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.3 Farm design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.3.1 Product-definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
1.3.2 Product-definition of ornamental fish . . . . . . . . . . . . . . . . . . . . . . . . . . 10
1.3.3 Biological submodel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
1.3 .4 Physical submodel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
1.3.5 Economic submodel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
1.4 Preliminary investigations into the culture potential of P. seafare . . . . . . . . . . . 16
1.4.1 General biology of P. sealare . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
1.4.2 Culture of P. seafare . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
1.4.3 Marketing and economic aspects of P. sealare production . . . . . . . . . . . 27
1.4.4 Research needed for development of farm design . . . . . . . . . . . . . . . . . 29
1.5 Research for this study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
CHAPTER 2. GENERAL EXPERIMENTAL PROTOCOL . . . . . . . . . . . . . . 31
2.1 Experimental animals and faci1ities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
2.2 Water quality monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
lll
continued
2.3 Water supply 32
2.4 Experimental tanks and tank systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
2.4.1 Broodstock tanks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
2.4.2 Egg and larval incubation tanks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
2.4.3 Nursery tanks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
2.4.4 Small scale recirculating system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
2.5 Anaesthesia of fish . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
2.6 Length measurement
2.7 Weighing procedure
2.8 Growth calculations
36
36
38
2.9 Feeds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
2.10 Statistical methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
2.10.1 Mean, standard deviation and variance . . . . . . . . . . . . . . . . . . . . . . . . 39
2.10.2 Students t-test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
2.10.3 Analysis of variance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
2.10.4 Regression analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
CHAPTER 3. DEVELOPMENT OF BIOLOGICAL SUB-MODEL 42
3.1 Length - weight relationships and determination of food particle size for P.
sea/are . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
3 .1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
3 .1.2 Materials and methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
3 .1.4 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
3.1.5 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
3.2 The effect of incubation technique on ova and larval survival of P. sea/are . . . 50
3.2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
3.2.2 Materials and methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
3.2.3 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
3.2.4 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
3.3 Nursery culture of P. sea/are under commercial hatchery conditions . . . . . . . . 62
3.3 .1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
iv
continued
3.3 .2 Materials and methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
3.3.3 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
3.3.4 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
3.4 Effect of feeding rate on the growth of P. seal are . . . . . . . . . . . . . . . . . . . . . . 69
3.4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
3.4.2 Materials and methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
3.4.3 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
3.4.4 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
3.5 The effect of stocking density on growth and fin factor P. seafare juveniles . . 80
3.5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
3.5.2 Materials and methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
3.5.3 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
3.5.4 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
3.6 Biological submodel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
3.6.1 Production stages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
3.6.2 Survival . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
3.6.3 Reproduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
3.6.4 Growth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
3.6.5 Nutrition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
3.6.6 Water quality requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
3.7 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
CHAPTER 4. MARKET CONSIDERATIONS FOR THE ORNAMENTAL
FISH MARKET AND IN PARTICULAR P. SCALARE . . . . . . . 102
4.1 An international perspective of the ornamental fish industry . . . . . . . . . . . . . . . 103
4.2 Industry survey of Australian ornamental fish industry . . . . . . . . . . . . . . . . . . . 107
4.2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
4.2.2 Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
4.2.3 Results and discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112
4.2.4 Summary of survey results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124
4.3 The Australian ornamental fish industry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125
v
continued
4.3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125
4.3.2 Imports of ornamental fish . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126
4.3.3 Domestic production . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130
4.3.4 Consumer profile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134
4.3.5 The Australian P. sea/are market . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137
4.4 Target markets, competitive analysis and SWOT for Tas Angels . . . . . . . . . . . 142
4.4.1 Description ofTas Angels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142
4.4.2 Target markets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143
4.4.3 Competitors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145
4.4.4 SWOT analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148
4.5 Summary and conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157
CHAPTER 5. PRELIMINARY ANALYSIS OF THE FEASIBILITY OF THE
INTENSIVE INDOOR CULTURE OF P. SCALARE . . . . . . . . . 159
5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159
5.2 Description ofTas Angels facilities and culture systems . . . . . . . . . . . . . . . . . . 160
5.2.1 Culture system design and operation . . . . . . . . . . . . . . . . . . . . . . . . . . . 160
5 .2.2 Production facilities desi!:,TU . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164
5.3 Recommended marketing mix strategies for Tas Angels . . . . . . . . . . . . . . . . . . 166
5.3.1 Market objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167
5.3 .2 Product . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170
5.3.3 Price . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175
5.3.4 Distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178
5.3 .5 Promotion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180
5.3.6 Summary of marketing strategy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187
5.4 Financial statements and analysis for Tas Angels . . . . . . . . . . . . . . . . . . . . . . . 189
5.4.1 Capital costs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190
5.4.2 Financial statements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191
5.4.3 Financial analyses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192
5.4.4 Improvements and recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . 200
5.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206
VI
continued
CHAPTER 6. CONCLUSION AND DIRECTIONS FOR FUTURE
RESEARCH 208
601 Purpose and value of the study 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 . 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 208
602 Summary of results 0 . 0 0 0 0 0 0 0 . 0 0 0 0 0 • 0 0 0 •••••.•. 0 •.• 0 • 0 0 . 0 0 0 0 0 0 0 . 210
603 Limitations of this study . 0 0 0 0 0 0 • 0 0 0 • 0 0 •.. 0 0 0 0 0 0 .. 0 •.••• 0 0 • 0 • . • • • • 214
6.4 Directions for future research ........ 0 0 •••.•..•.•.... 0 .. 0 •...••.• 0 215
605 Final comment ... 0 •..•• 0 •••. 0. 0 •.••••••.•. 0 • 0 0 ••... 0 0 .. 0 ... 0 . 0 217
REFERENCES .. 0 .•.•.•.• 0 .• 0 0 0 0 ... 0 0 0 0 0 0 0 0. 0 0 0 0. 0 0 0 •...• 0 0 0 0 0 0... 218
APPENDIX A QUESTIONNAIRE USED IN INDUSTRY SURVEY 0 0 o 0 0 0 0 0 232
APPENDIX B COVER LETTER USED IN INDUSTRY SURVEY 0 0 0 0 0 0 0 0 0 236
APPENDIX C FOLLOW-UP LETTER USED IN INDUSTRY SURVEY ... 0 238
APPENDIX D IMPORTS OF ORNAMENTAL FISH BY COUNTRY OF
ORIGIN 0 ••..• 0 ... 0. 0 .•..• 0 •.• 0 .• o ••• 0 0 ••.••...•••• 0 240
APPENDIX E DETAILS OF PROMOTIONAL ACTIVITIES AND COSTS . 241
APPENDIX F DETAILS OF COST CALCULATIONS USED TO DEVELOP
FINANCIAL STATEMENTS FOR TAS ANGELS . . . . . . . . . . 243
APPENDIX G ASSUMPTIONS AND COSTS FOR STAGED EXPANSION
SCENARIO 0 0 0 .• 0 • 0 ••. 0 •••.. 0 0 0 0 0 •. 0 0 •• 0 • 0 • 0 0 0 0 0 • 0 • • 249
APPENDIX H ASSUMPTIONS AND COSTS FOR LEASING SCENARIO 0 0 253
Vll
LIST OF FIGURES
Figure
1. Colour plates of P. seafare
2. Map of the natural distribution of P. seafare
Page
18
20
3. Front view of P. seafare, indicating external morphological sex differences 21
4. Diagram of small scale experimental recirculating system used in growth trials for juvenile P. seafare .................................... .
5. Lateral view of P. seafare indicating length measurements used in this study
6. Exponential regression of length - weight data for P. seafare ........... .
7. Linear regression of standard length and upper-jaw length data for P. seafare
8. Linear regression of standard length and calculated gape data for P. seafare
9. Number of spawnings for P. seafare broodstock pairs during the 55 day
35
37
45
46
47
experimental period . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
10. The effect of egg and larval incubation method on absolute fecundity for
different sized female P. seafare 56
11. The effect of egg and larval incubation method on cumulative fecundity for
different sized female P. seafare 57
12. The effect of egg and larval incubation method on relative fecundity for
different sized female P. seafare 58
13, Daily incidence of mortalities of P. seafare juveniles during nursery culture
phase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
14. Increase in mean standard length of P. seafare juveniles during nursery
culture phase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
15. Change in mean weight of P. seafare juveniles using different feeding rates 72
16. Effect of feeding rate on the specific growth rate of juvenile P. seafare . . . . 74
17. Linear regression of the food conversion ratio and feeding rate of P. seafare
juveniles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
Vlll
continued
18. Linear regression of gross efficiency and feeding rate of P. seafare
JUveniles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
19. Change in mean weight of P. seafare juveniles cultured at different stocking
densities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
20. Specific growth rate of juvenile P. seafare at different stocking densities 86
21. Effect of stocking density on the food conversion ratio of juvenile P.
seafare . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
22. Linear regression of stocking density and fin factor data for juvenile P.
seafare cultured at different stocking densities . . . . . . . . . . . . . . . . . . . . . . . 89
23. Generalised international market channel for ornamental fish . . . . . . . . . . . . 105
24. Graphical illustration of proposed production schedule for Tas Angels . . . . . 163
25. Proposed floor plan ofTas Angels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166
IX
LIST OF TABLES
Table Page
1. Design parameters for development of a farm design or system model 7
2. Product-definition for different product types of food fish . . . . . . . . . . . . . . . . 9
3. Product-definition of live ornamental fish . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
4. Comparison ofLaunceston City Water with general fish culture water quality
standards and recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
5. Composition of Gibson's salmon starter pellets . . . . . . . . . . . . . . . . . . . . . . . . 38
6. Recommended food particle sizes for P .scalare . . . . . . . . . . . . . . . . . . . . . . . 49
7. The spawning frequency of P. scalare with different methods
of egg and larval incubation during experimental period of 55 days 53
8. Fecundity of P. scalare using artificial and natural incubation of eggs and
larvae . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
9. Mean larval size and survival rates for P. scalare using
natural and artificial incubation of eggs and larvae . . . . . . . . . . . . . . . . . . . . . . 55
10. Initial length, final length and survival ofP. scalare fry during nursery
culture phase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
11. Summary of water quality parameters for nursery tanks . . . . . . . . . . . . . . . . . 65
12. Growth and feeding efficiency of P. scalare at different feeding rates
13. Summary of water quality parameters during feeding rate experiment
14. The specific growth rate and food conversion ratio of P. scalare juveniles
71
73
at different stocking densities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
15. Dorsal-fin length, standard length and fin factor of P. scalare juveniles
cultured at different stocking densities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
16. Summary of water quality parameters for stocking density experiment . . . . . 90
17. Production and life stages of P. scalare . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
18. Calculated survival rate and range of P. scalare for production stages . . . . . . 95
X
continued
19. Calculated annual egg production of P. seal are using at1ificial egg and larval . t h . reanng ec ntques ............................................ .
20. Growth and production data for P. scalare .......................... .
41. Recommended food type, particles size, feeding rate and expected food
96
97
conversion ratio for production stages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
22. Wholesale market value (US$) of tropical ornamental fish . . . . . . . . . . . . . . . 103
23. Number of farms surveyed and their response rate . . . . . . . . . . . . . . . . . . . . . 111
24. Location of ornamental fish farms in Australia . . . . . . . . . . . . . . . . . . . . . . . . 113
25. Relative use of production systems by Australian ornamental fish producers 114
26. Use of different production intensity of ornamental fish of fatms in each
state . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
27. Percentage of ornamental fish farms using various market channels . . . . . . . . 116
28. Staffing of ornamental fish farms in Australia . . . . . . . . . . . . . . . . . . . . . . . . 117
29. Ornamental fish species currently produced in Australia . . . . . . . . . . . . . . . . . 119
30. Actual and estimated production of surveyed ornamental fish farms in
Australia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121
31. State production of omamental fish in Australia in the 1994-95 financial
year . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
32. Number of imports of ornamental fish into Australia and FOB value . . . . . . 127
33. Number and FOB value of imports of ornamental fish into Australian states
between 1989- 90 and 1993- 94 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131
34. Ornamental fish; estimates of number of farms, area, production & value for
1989-90 (O'Sullivan, 1991) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132
35. Farm gate ptices and price per kg of P. scalare in Australia . . . . . . . . . . . . . . 137
36. Annual sales of P. scalare by Pet & Aquarium Industries Pty Ltd for 1993 -
94 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138
3 7. Estimated annual number and value of sales of P. scalare in Australia for
1993- 94 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139
38. Production of P. seafare in Australia for the year 1994- 95 . . . . . . . . . . . . . . 140
39. Size and value of geographic market segments for P. scalare in Australia for
1993 -94 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141
40. Size of target segments for import replacement of P. seafare in Australia for
1993- 94 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144
XI
continued
41. Production targets for Tas Angels 145
42. Summary of strengths, weaknesses, opportunities and threats for Tas Angels 148
43. Projected annual production of P. seafare by Tas Angels during the first five
years of operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162
44. Number and cost of culture tank systems for Tas Angels . . . . . . . . . . . . . . . . 164
45. Product-definition of P. seafare for the ornamental fish industry in Australia . 171
46. Tas Angels marketing schedule for the first five years of operation . . . . . . . . 188
47. Capital cost requirements for an intensive culture facility for production of
207,000 P. seafare . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190
48. Depreciation schedule of capital items for Tas Angels . . . . . . . . . . . . . . . . . . 191
49. Loan repayment schedule for Tas Angels . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192
50. Cash flow statement for first five years operation for Tas Angels . . . . . . . . . . 193
51. Profit and loss statement for first five years operation for Tas Angels . . . . . . . 194
52. End of year balance sheet for Years 1 and 5 for Tas Angels . . . . . . . . . . . . . . 195
53. End of year financial ratios for Tas Angels . . . . . . . . . . . . . . . . . . . . . . . . . . . 197
54. Comparison of end of year financial ratios for three scenarios for Tas Angels 202
55. Imports of ornamental fish into Australia by country of origin between
1990-91 and 1992-93 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240
56. Patiial cash flow statement for staged expansion of Tas Angels . . . . . . . . . . . 250
57. Partial profit and loss statement for staged expansion of Tas Angels . . . . . . . . 251
58. Partial balance sheet statement for staged expansion scenario for Tas Angels . 251
59. Partial cash flow statement for leasing production facility by Tas Angels 254
60. Partial profit and loss statement for leasing scenario for Tas Angels . . . . . . . . 255
61. Partial balance sheet statement for Tas Angels leasing suitable premises . . . . 256
Xll
ABSTRACT
The majority of ornamental fish sold in Australia are imported from overseas farms and wild
fisheries mainly based in Asia. The number of ornamental fish imported into Australia in
1991-92 was 7,593,812 tails worth $2,385,000 landed in Australia. Due to the increase in
importation costs, it has become more economical and attractive for Australian hobbyists and
farmers to produce many species commercially, especially the more specialised higher-value
lines of tropical ornamental fish. The industry is expected to expand rapidly during the
1990's and is rated as having sound prospects for the future, with production for 1994-1995
expected to be worth around $10 million (O'Sullivan, 1991).
At present over 20 species of ornamental fish species are cultured on a commercial scale in
Australia (McKay and Reynolds, 1983). One such example is the freshwater Angelfish,
Pterophyllum sea/are (Lichtenstein) (Pisces; Cichlidae) , a popular medium-priced cichlid.
CmTently production of this species in Australia is minimal and the biological, marketing and
economic aspects of commercial production are poorly understood.
This research project examines the current knowledge of the biology of P. sea/are and
establishes the performance of P. sea/are under intensive culture conditions. In particular
experimentation examines the following areas:
1. Length-weight and length-mouth size relationships;
2. Hatchery production, in particular the effect of artificial incubation of eggs
on the reproductive performance of P. sea/are under commercial culture;
3. Growth and survival of P. sealare during the nursery culture phase;
4. Effect of ration level on growth, survival and feeding efficiency; and
xm
5. Effect of stocking density on growth, survival and fin factor.
The results from these expeliments suggest that P. sea/are is a good candidate for intensive
culture, with reasonable growth rates, high survival and good feeding efficiency. However,
there is potentially a problem with the reproductive output of P. sea/are. Although these
experiments indicate that artificial incubation of eggs can increase the cumulative fecundity
of P. sea/are, egg production is highly variable and large numbers of broodstock must be
kept to supply eggs for an intensive culture system. This is an area that needs further
research effort.
Preliminary market analysis, based on a survey of the Australian ornamental fish industry,
indicates that the majority of P. sea/are sold in Australia at present are imported. With the
increasing costs associated with importing fish, there appears to be considerable market
potential for Australian producers to supply P. scalare for import replacement. The survey
also indicates the rapid growth of the Australian industry and its growing importance as part
of the aquaculture industry. It is expected that the industry will continue to grow rapidly
throughout the remainder of the decade.
A preliminary farm design is developed, based on these marketing data as well as the
biological data, as a basis for assessing the culture potential of P. sea/are under intensive
culture conditions. From this farm design, financial statements are developed to analyse the
economic potential of intensive culture of P. seafare, and recommendations made for
marketing strategies for the enterplise. Analysis indicates that intensive production of P.
seafare is feasible, but returns are limited due to high capital investment, long establishment
and lag-time in production, and small market size. The analysis indicates that with an
initial investment of $120,000, an owner/operator would realise a net present value of
approximately $35,000 after five years. Improvements in the biological performance of P.
sea/are, the use of polyculture and increasing the market size may further increase the culture
potential of this species.
XIV
P. scalare offers merit as an aquaculture species in Australia, particularly for a family
business, with production and marketing strategies aimed at producing high quality fish for
import replacement.
XV
CHAPTER 1
INTRODUCTION
1.1 Introduction
The aquaculture industry world-wide has been characterised in the past by a high failure rate of
new ventures and poor profitability, with the Australian aquaculture industry being no exception.
Although this is to be expected in any new industry, failures in many cases can be attributed to
the lack of understanding of the fundamental relationship between the biology of a species, the
physical culture system, site selection, the economics of the culture system and the market
potential of the cultured species (Allen et al., 1984; O'Hanlon, 1988; Pillay, 1990; Shepherd and
Bromage, 1988; and Logan and Johnston, 1992). This lack ofunderstanding often leads to poor
design, planning and management of farms.
Aquaculture has been practised in various parts of the world for some 2,500 years. However, it
has only recently begun to develop from a cmde, subsistence level of production and technology
to a more sophisticated, highly developed process (Allen et al., 1984; Pillay, 1990; and Shepherd
and Bromage, 1988). Indeed, aquaculture is yet to experience the development seen in the
agriculture industry which has resulted in the domestication of many plant and animal species
(Raven and Johnson, 1990). In contrast, aquaculture can boast only a few domesticated species
of food fish, including the common carp, Cyprinus carpio; channel catfish, Ictalurus punctatus;
rainbow trout, Oncorhynchus mykiss; atlantic salmon, Salmo salar; and Tilapia spp (Allen et
al., 1984; Pillay, 1990; and Stickney, 1994).
1
In contrast, the ornamental fish industry has many species of fish that have been domesticated
through continuous breeding over many generations. The most familiar of these species is the
goldfish, Carrassius auratus, which was first reared in China over 2,500 years ago (Penzes and
Tolg, 1986). Examples of other domesticated species found in this industry include guppies,
Poeclia reticulata; angelfish, Pterophyllum seafare; gouramis, Trichogaster sp.; platys,
Xihophorus variatus; and Siamese fighting fish, Betta splendens.
The market for ornamental fish is well established throughout the world (Bedford-Clarke, 1993;
Bassleer, 1994), with world-wide wholesale sales of ornamental fish worth more than US$4
billion per annum (Winfree, 1989) and retail sales in 1986 more than US$7.2 billion (Andrews,
1992). The market is also well established in Australia, with ornamental fish or aquarium fish
hobbyists representing approximately 11 per cent of households in Australia (Humphrey, 1989),
with at least one million enthusiasts in Australia ( 0' Sullivan, 1991 ). The Australian
ornamental fish industry sells over $80 million retail value worth of aquarium fish annually (pers
comm, R. McKay, 1991).
The majority of ornamental fish sold in Australia are imported from overseas farms and wild
fisheries. The number of ornamental fish imported into Australia in 1993 - 94 was
7,872,909 tails, worth in excess of $2,720,000 landed in Australia (Australian Bureau of
Statistics Foreign Trade Data). Due to the increase in importation costs, it has become more
economical and attractive for Australian hobbyists and farmers to produce many species
commercially, especially the more specialised higher-value lines of tropical ornamental fish.
The industry is expected to continue to expand during the rest of the 1990's and is rated as
having good prospects for the future, with production for 1994-1995 expected to be worth
around $10 million (O'Sullivan, 1991).
At present over 20 species of ornamental fish species are cultured on a commercial scale in
Australia (McKay and Reynolds, 1983). One such example is the freshwater Angelfish,
Pterophyllum sea/are (Lichtenstein) (Pisces; Cichlidae) , a popular medium priced cichlid.
Currently production of this species is minimal in Australia and the biological, marketing and
economic aspects of commercial production are poorly understood.
2
P. seafare is a popular species that has a well established reputation in the aquarium industry,
with several different colour forms available, as well as long and short tailed versions, developed
through selective breeding. It is estimated that the Australian market for Angelfish is in the
vicinity of 320,000 tails per year, with sales of 56 per cent small, 40 per cent medium sized and
4 per cent large sized (pers comm, R. Datodi, 1992). At present the majority of P. seafare sold
in Australia are imported from Asian farms. This suggests that there is good potential for
production of P. seafare for import replacement in Australia.
There is no longer any reliance on wild fisheries for the supply of this species (Brown and
Gratzek 1982), and demand must be met through farm produced fish (Axelrod and Burgess,
1979). However, little data are available on the economics of producing this species, or indeed
other omamental fish species, either in Australia or overseas. With continuing demand in the
omamental fish industry and the inconsistent nature of its supply, P. seafare offers potential as
an aquaculture species.
This study presents a preliminary analysis of the culture potential of P. seafare by assessing the
feasibility of producing P. seafare in an indoor, intensive culture system, situated in
Launceston, Tasmania. The study is divided into three sections:
1. focus on the development of biological data through experimentation;
2. an analysis of the market for P. seafare in Australia; and
3. the development of a farm design and economic assessment of the culture
potential of this species, based on the biological and market data generated in the
first two sections of the study.
The remainder of this chapter provides a brief introduction to bioeconomics and the application
of this discipline to aquaculture. A preliminary commentary on the general biology, culture
methods and economics of producing P. seafare is also given.
3
1.2 Bioeconomics in aquaculture
Traditionally, assessment of the culture potential of a given species has been simplistic and one
dimensional, based on the market potential of a species (Allen et al., 1984). However, as well as
considering the market potential for a cultured species, consideration also must be given to its
biology and the physical culture system to be used. More recently, a more integrative approach
has been adopted with these aspects viewed as a dynamic interrelated system. This approach
acknowledges the dynamic interrelationships that exist between these disciplines. Bioeconomics
is a term used to describe these integrative relationships between the biological and economic
attributes of a physical production system (Allen et al., 1984; O'Hanlon, 1988; Shepherd and
Bromage, 1988). This relationship examines the aquacultural enterprise as an entire dynamic
system considering the interrelationships of three areas, rather than the traditional one
dimensional view of a farm as a just a set of accounts. Bioeconomics assesses the culture of a
given species in three functional areas as defined by Allen et al. (1984). These functional areas
are:
1. the biological characteristics of the cultured species;
2. the physical culture system design and management; and
3. the economic performance of the physical culture system and
marketing of the cultured species.
The biological characteristics of the cultured species are perhaps the most fundamental and
limiting factor from the bioeconomic viewpoint. For success, a precise understanding of
reproduction, growth and development, nutrition and physiological functions must be attained
(Allen et al., 1984). Fundamental scientific research on the chosen species biology is essential
to achieve this. These characteristics can be presented as the biological sub-model of the culture
system.
The technical component of a culture system also is important, and must be designed to satisfy
the biological characteristics of the cultured species and to meet economic objectives of the
4
culture concept (Allen et al., 1984; O'Hanlon, 1988). The physical system, presented as the
physical sub-model, must provide the necessary physical requirements for optimal biological
performance at the most economic rate (O'Hanlon, 1988). In order to accomplish this goal, the
physical system must provide the following: suitable water quality, sufficient space for growth
and development, and a suitable feeding regime. The physical system regulates and controls the
culture environment for the fish, providing the abiotic factors needed for reproduction and
growth ( eg. space for fish, water of good quality, food, oxygen and waste removal). The fish in
the system respond by surviving to grow to marketable size whence they are sold and the system
restocked.
As in any other business activity, the principles of economics must apply to the aquaculture
enterprise, both on a microeconomic (ie. farm) and a macroeconomic level (ie. industry,
domestic market, international market) (O'Hanlon, 1988), with changes in the external
environment just as significant as changes in the internal environment (ie. availability or cost of
inputs or price and demand of output) . The economic factors that must be considered when
evaluating the production from a given culture system include:
1. assessment of market or projected market for the product;
2. costs of production;
3. projected sales and revenue;
4. variation in costs and revenue; and
5. profitability of the enterprise.
Costs include operating costs (ie. costs of inputs - heating, pumping, food, chemicals, and
labour), capital costs (ie. the money required to establish plant and equipment, buildings and
land) and costs associated with conducting marketing activities which are generally essential for
maintaining and/or expanding market share. The functional relationships between the biological
and physical components result in a unique set of economic circumstances (ie. cost of
production, net cash flow, profit), for any given production scenario, with changes in any aspect
of the biological and or physical components having some degree of impact on the economic
5
outcome (Allen et al., 1984). These economic circumstances are presented as the economic
sub-model.
Therefore the aquaculture fatm designer must be able to utilise data from the disciplines of
biology, engineering and economics in order to develop a suitable facility. The design process
and data sources are discussed in the following sections.
1.3 Farm design
A farm design can be developed for the cultured species from the biological, physical and
economic submodels. This design can be used to define both the relationships between the
system components and the performance of a system, and at the same time permit comparisons
to be made with other systems (Allen et al., 1984; Huguenin and Colt, 1986; and Logan and
Johnston, 1992). Developing a farm design is a complex task involving a range of biological,
technological, marketing and economic data. The complexity of the system is compounded by
the interactions between the various components of the system (Allen et al., 1984; Huguenin
and Colt, 1986; and Logan and Johnston, 1992). The fatm design should indicate the
relationships between the physical system and biological response of the species in a quantified
way to determine the following factors:
1. the economic viability of the enterprise;
2. areas for further research;
3. the technology to be used;
4. production management;
5. marketing management; and
6. site selection.
In order to determine the above factors a series of parameters need to be known in order to
develop a workable system model. These parameters include: site specific conditions;
management decisions; biological responses; and costs. These parameters are further expanded
in Table 1.
6
Table 1. Design parameters for development of a farm design or system model
1. SITE SPECIFIC CONDITIONS 2. MANAGEMENT DECISIONS 3. BIOLOGICAL RESPONSES 4. COSTS
A. Location of facility, market proximity A. Marketing strategy A. Water conditions A. Capital costs 1. Product definition 1. Water flow requirement 1. Plant 2. Market mix strategy 2. Oxygen consumption 2. Land
3. Temperature effects 3. Buildings 4. Stock
B. Water quality B. Initial production strategy B. Egg production rates B. Operating costs 1. Temperature 1. Hatchery operation 1. Conditions affecting time to hatch L Fixed 2. Dissolved oxygen 2. Procurement size 2. Fecundity 2. Variable 3. pH level 3. Larval growth and development. 4. Volume of water or Flow rate 5. Pollution - current or future
C. Government restrictions and licensing c. Capacity of facility C. Stocking density requirements 1. Number of tanks 1. Effect on food conversion ratio
2. Size of tanks 2. Effect on growth rate and net productivity of system.
D. Available infrastructure, utilities, D. Technology D. Nutrition Requirements services, and labour 1. Technology organisation 1. Dietary requirements
2. Intensive culture versus extensive 2. Ration
E. Stocking density E. Growth rates
F. Ration and feeding practices F. Metabolite production 1. Complete ration 1. Recirculation and treatment 2. Hand feed or automatic feeders
G. Water treatment G. Mortality rates 1. Flow through 2. Recirculation
I 3. Effluent treatment L_-------~------------
-....)
The parameters listed in Table 1 can be used, in conjunction with the product definition, to
determine a farm design, which should address the interactions between these factors.
Generally the biological requirements and expected culture performance of a species will act as
the framework on which the culture system must be based. A physical culture system must then
be developed that meets the biological requirements and achieves the required biological
performance of the species in a manner that meets economical and marketing objectives. Due
to the diverse range of data needed from the various disciplines to design a farm, it is a very
difficult, time consuming process that is sometimes more of an art than a science (Parker, 1981;
Huguenin and Colt, 1986). The difficulty is often compounded by a lack of data for various
areas of the farm design. These sub-systems are discussed in the following sections. Of
particular use when commencing design of the facility is to begin with a sound idea or definition
of what product( s) will be produced by the farm. Several researchers have proposed a product
definition to provide system designers with a formal definition of the product(s) that will be
cultured by a facility.
1.3.1 Product-definition
Anon (1979) proposed a product-definition in order to help define the production/economic
objectives of a culture system. The product-definition is a clear statement of the product that will
be produced from the system, stating the purpose or use of product in terms of consumer
expectations (Forteath, 1993). This statement would ideally be used to determine the most
suitable species and culture system to suit the product attributes and consumer expectations,
however this is seldom the case with many farm designs based on limited biological
considerations and culture requirements, or based on techniques and biological criteria for other
species of fish. To date product-definition has been used rarely when designing and
constructing aquaculture facilities, leading to poor performance of the farmed species and often
resulting in expensive modifications being made to the production facilities or production
techniques (Forteath, 1993).
Aquaculture facilities produce a vast range of products, for example, oyster spat, Kurama prawns
and table-fish. Other less typical species or products produced by aquacultural enterprises
8
include microalgae, macroalgae, zooplankton, and sea-urchins. The products that a typical fish
farm may produce can be summarised in the following classes:
1. game or commercial harvest (ranching);
2. food fish;
3. ornamental or aquarium fish;
4. forage and baitfish; and
5. egg production.
Each of these classes may be defined further, in order to give a more specific picture of their
product-definition. Within each class, there may be more than one type of product, with
considerable differences between the definitions of the various types, particularly in terms of
product-attributes. For example, Anon (1979) defines the various types of food fish as set out in
Table 2.
Table 2. Product-definition for different product types of food fish
Product type
Fresh fish (dressed) Processed fish Fee Fishing Product 1. Condition 1. Boned 1. Size
attributes a) K-factor 2. Filleted 2. Ease of catching b) appearance 3. Fish sticks
2. Species 4. Fish protein concentrate 3. Size 4. Shelf life
Market 1. Size ie. weight 1. Size ie. weight 1. Size eg. weight, length
demand 2. Season 2. Season 2. Season 3. Number 3. Nmnber 3. Number
Consumer 1. Dress-out (meat yield) 1. Dress out 1. Perfonnance as a
acceptance 2. Presentation 2. Size sportfish 3. Flesh quality 3. Flesh quality 2. Availability of 4. Taste 4. Taste stockers
9
It must also be noted that the product definition may vary for a given species when considering
local and export markets, in fact, consistent with basic marketing principles, the
product-definition will often vary according to which export market is considered (Logan and
Johnston, 1992). Farms also may produce more than one type of product, or a product-line of
related items. This gives rise to more than one product definition for the farm. A hatchery and
grow-out operation, for example, may sell eggs, fingerlings and plate sized fish. This increased
range of products spreads the risk, giving flexibility and the ability to adapt to changing markets
(Logan and Johnston, 1992).
Therefore, although the farm becomes more complex to manage, there are inherent advantages
in having greater flexibility in adapting production strategies to suit changes in market demand
or the needs of different market segments.
Once the product-definition has been decided for the cultured species with a clear understanding
of the marketing objectives and attributes, a more rigorous approach can be used to further
assess the economic merits of producing the species. It can be used as a starting point in
beginning the farm design, for example, it may be used to estimate culture system size, the
appropriate culture technology to be used, and processing and packaging needs. Fmieath (1993)
highlights the fact that the product-definition is rarely used in aquaculture to determine these
factors. This concept can also be used for ornamental fish and is discussed in the following
section.
1.3.2 Product-definition of ornamental fish
Although many of the production techniques used in food fish and ornamental fish culture are
similar, there are considerable differences between food and ornamental fish. Perhaps the most
distinct difference between the product-definitions for ornamental and food fish is that
ornamental fish are always live. A general scheme for the product-definition of ornamental fish
was proposed by Anon (1979) and has been adapted as shown in Table 3.
10
Table 3. Product-definition of live ornamental fish
Market demand 1. species 2. geographic market 3. frequency 4. number
Appearance 1. colour 2. fin factor 3. condition factor 4. damage
Distribution 1. transportation method 2. packaging 3. packing density 4. anaesthetics 5. acceptable mortalities during
transit
Disease status 1. disease free certification 2. disease history 3. previous treatments 4. health of fish
Market demand is a very important factor. The sale of ornamental fish in Australia is relatively
stable with little seasonal fluctuation in demand throughout the year (Brown and Gratzek, 1982)
and the farmer must be able to supply this demand continuously. This may pose a significant
problem for producers, particularly those using extensive production methods which often result
in seasonal production (Brown and Gratzek, 1982). As a result producers may face difficulties
in matching supply with demand at certain times of the year.
Associated with market demand are aspects of quality in the appearance of the fish ie. colour,
fin-factor, condition-factor and damage to fins and skin. This quality is dependent on a range of
factors including culture methods used, nutrition of fish, and handling techniques. It is
important for farmers to develop fish management practices that enable a given level of quality
to be maintained throughout the year.
Distribution is a very impmiant factor in the product-definition of ornamental fish. Farm
products are generally perishable (Kotler et al., 1983; and Stanton et al., 1994) and as such
11
require particular attention in packaging and transportation. Due to this extra care and special
packaging needed to ensure that ornamental fish arrive alive and healthy, packaging and
transport costs may add considerably to production expenditures (Brown and Gratzek, 1982).
The disease status of ornamental fish is also an important factor. Rigorous disease control and
strict quarantine procedures when introducing new stock to the farm are invaluable in
establishing and maintaining good quality stock. It is expected that these factors will increase in
importance with the growing concern on the potential to introduce and spread exotic disease
throughout Australia.
Once the product definition has been achieved, the farm designer can begin work on developing
the biological submodel, which will create the basis on which subsequent development of
technical and economic data can be based.
1.3.3 Biological submodel
The biological submodel must be as realistic as possible because it is the basis for the physical
and economic submodels and will indicate the limitations and requirements of the system. Data
for this submodel can come from a range of areas. Allen et al. (1984) divide these sources of
data into four groups. The first source and probably the most reliable and valuable source is
aquaculture oriented expetimental data. These experiments are generally designed to give
specific information on culture related topics and may be in the form of laboratory to pilot scale
production system experiments.
The second source of data is from non-aquaculture oriented experiments. These data may be
derived from physiological or ecological studies of fish and are useful in increasing the
understanding of environmental influences on attributes such as fish reproduction and growth.
However, Parker (1981) and Huguenin and Colt (1986) highlight the following when basing
designs on non-aquaculture expetimental data:
1. research and designs aims may differ;
12
2. time factor - research is generally short term with farming long-term;
3. although biological and behavioural processes are generally dependent on scale;
the effects of scale are often underestimated or ignored;
4. data from other species, even closely related species, may not give a true
indication of another species performance; and
5. inherent differences between laboratory and field conditions.
The third source of data can be attained from existing metabolic and growth models developed
through previous studies. However their usefulness may be reduced due to differences between
the culture and experimental environments, as well as differences in the aim or purpose of the
existing model and the culture model.
The fourth source of data is the use of energy or mass balance relationships. These relationships
can be used to estimate upper and lower limits of experimental values and may be useful as
substitutes for experimental data (if unavailable) or as a check for experimental results.
Thus, a wide range of biological data may be available for the researcher to develop the
biological submodel. Generally, such data are usually taken from a combination of the four
sources. These sources often complement each other by reducing deficiencies in data from each
individual source (Allen et al., 1984). Even then it is vitally important that the biological
submodel reflects the true nature of the interactions of the cultured species with its environment
in order for an accurate physical submodel to be designed, as well as determining the economics
of the system. For this reason pilot scale studies are often performed before commercial scale
production commences to reduce enors in the biological submodel. Once the biological
submodel is satisfactory, development of the physical submodel can commence.
1.3.4 Physical submodel
The physical submodel includes all the culture facilities and management practices used to
spawn, grow, harvest and process the cultured species. These facilities are usually designed with
only a limited number of the cultured species biological requirements in mind and are often
13
based on the biological requirements of other species due to lack of biological data (F01ieath,
1993). Ideally the facilities would be designed to satisfy the product and marketing criteria set
by the product-definition, as well as the biological requirements of the cultured species.
A vast range of culture systems is available to the farm designer, ranging from extensive pond
systems to more intensive culture methods such as raceways, cages and recirculating systems
(Wheaton, 1977; Muir, 1982; Laird and Needham, 1988; Shepherd and Bromage, 1988; Pillay,
1990; and Stickney, 1994). As the intensity of production increases, so must the level of control
over the culture environment. For example, Tilapia production has traditionally been canied out
on a subsistence basis involving little more than harvesting of fish from ponds (Allen et al.,
1984). This has meant that there is virtually no control over the production of the Tilapia and
the production from such a system is minimal and somewhat unreliable (Pillay, 1990). A move
towards more intensive production of Tilapia has lead to a higher level of capital investment (ie.
pumps, aerators, tanks etc.), and a higher level of inputs (ie. more labour, artificial food etc.) has
led to an increase in operating costs. However, this greater level of control and intensity means
much higher production is possible (eg. 64 kg/m3) (Balat·in and Haller, 1982; and Stickney,
1994).
Site selection also is an important consideration that can have a substantial impact on the choice
of technology, operation and profitability of the farm (Shepherd and Bromage, 1988; and
Stickney, 1994). In the past, site selection has been based mainly on the availability of sufficient
quantities of suitable water for projected use and future expansion. However, other factors such
as electricity supply, road access etc. must be considered. Also an important factor that is often
overlooked is the access to markets. If a suitable local market is unavailable for the product then
access to transportation must be addressed. The trade-offs between access to a suitable site and
good quality water must be offset against costs of accessing markets and distributing the product
to the customers. Consequently, the choice of system and technology is affected by many
factors including the following:
1. biological requirements of the cultured species;
2. land availability;
14
3. water quality and availability;
4. climate;
5. infrastructure (ie. utilities, roads);
6. labour and technical expertise;
7. feeds;
8. product distribution (harvest, storage, processing and transportation);
9. level of capital investment; and
10. marketing and economic goals of the system.
Once the physical submodel is complete, an economic submodel must be developed.
1.3.5 Economic submodel
Normally aquacultural enterprises have the economic objective of profitability for the owners.
However, it should be noted that the enterprise may also need to meet a range of social, political,
legal, technical and environmental objectives (Huguenin and Colt, 1986) such as restocking
native fish stocks, providing seed stock for subsistence farmers, aquaculture research centres and
public aquaria. In developing this submodel, a range of factors must be addressed:
1. level of capital investment;
2. gross mcome;
3. operating costs; and
4. debt and equity levels.
Management decisions relating to these factors are made in the context of uncertainties in the
supplies of inputs and the demand for the final product. Further complications arise from the
variability in the biological responses of the cultured species and their interaction with the
physical system. Therefore economic decisions need to be considered together with the physical
and biological submodels.
15
Marketing in aquaculture is often a neglected area (Shaw, 1986; and O'Hanlon, 1988). Many
farm designs have been based on production of products that the designers perceive the market
desires rather than on market needs. However, through market research and consequent product
definition appropriate production and marketing strategies can be developed to satisfy market
demand. This approach is market driven rather than product driven. Shaw (1990) indicates
that this market driven approach is becoming increasingly important for aquaculture producers
due to the increasing level of competition throughout the industry. There also is an increasing
need for farmers to establish and maintain competitive advantages over other farms in order to
maintain market share and profitability.
From the above discussion it is clear there is a wide range of data necessary to develop a farm
design for any given species. Thus, when commencing work on such a project it is first
necessary to conduct a secondary data search (Allen et al. 1984) in order to establish the current
knowledge on the biology, culture and economics of the candidate species. The following
sections address this issue.
1.4 Preliminary investigations into the culture potential of P. seafare
When investigating the culture potential for any species, an essential starting point is a review of
the current status of knowledge on culture, biology and economics for the candidate species. A
review of this secondary data may reveal considerable information regarding the candidate
species and indicate areas that require investigation. This information will save the farm
designer time and money by identifying areas where research is needed, as well as enabling
pliority of research needs to be determined.
The following section gives a review of the current understanding of the general biology of P.
seafare, as well as culture methods and economic and marketing considerations. These data. will
then be used to highlight areas where knowledge of P. seafare is lacking for the development of
a realistic farm design for intensive P. seafare culture in Tasmania and hence its culture
potential.
16
1.4.1 General biology of P. seafare
P. sea/are has been utilised as an ornamental fish species for many years. During this time a
great deal of work has been conducted on the general biology of P. sea/are, which is discussed
below.
External morphology. P. seafare has a strongly compressed, deep form resulting in a disc-like
body shape with large sickle shaped dorsal and anal fins. The pelvic fins are elongated giving a
feeler like appearance, with the caudal fin being large and rounded (Axelrod and Burgess, 1979;
Hoedeman, 1975; and Mclnenry and Genard, 1989) (see Figure 1). This species grows to a
length of approximately 150 mm and up to 260 mm from the dorsal-fin tip to anal-fin tips
(Hoedeman, 1975; and Petrovicky, 1984). The basic colouration is olive-green to grey with a
silvery sheen (Hoedeman, 1975), but selective breeding has given rise to many other colours,
including yellow-golds to blue-green and black.
Taxonomy. The taxonomy of aquarium fish often is confused and disorganised, generally due to
hunied and inaccurate naming of species (Axelrod and Burgess, 1979). The genus Pterophyllum
is no exception.
Coffey ( 1977) lists three species of fish in the genus Pterophyllum, viz. P. altum, P. seafare, and
P. dumerilii. More recently Gilbert ( 1981) lists three species within this genus, viz. P. altum, P.
seal are and P. eimekei, while Petro vicky ( 1984) lists just P. seafare and P. altum and states that
P. eimekei is synonymous with P. sea/are. Mcinerny & Genard (1989) agree with Gilbert
(1981) stating that the genus consists of three species P. seafare, P altum, and P. eimekei.
Gilbert (1981) further states that due to the similarity between P. eimekei and P. seafare,
interbreeding between the two species is common and has resulted in a domesticated hybrid due
to continual crossing of the species since they were first kept in captivity in the early part of the
20th century.
It would appear therefore that the domesticated Angelfish stocked in aquaria throughout the
world are the result of interbreeding of the two species P. eimekei and P. seafare. As most
17
Figure 1. Colour photograph of a sub-adult, gold variety P. sea/are
18
literature regarding Angelfish uses P. seafare as the species name, P. seafare will be used in this
thesis.
Natural Distribution and Habitat. Fish of the genus Pterophyllum occur naturally in the
Amazon basin, ranging throughout its river systems (Axelrod and Burgess, 1979) (see Figure 2).
P. seafare usually inhabits slow flowing areas of rivers, particularly in rocky areas, where it
hides in the rock crannies (Hoedeman, 1975). Shady pools covered by vegetation are generally
most favoured (Axelrod and Burgess, 1979).
In its natural habitat, P. seafare is exposed to a pH range of 5.8- 6.2 and a water hardness
(mg/1 CaC03) of 16 ppm (Axelrod and Burgess, 1979). However, in captivity it has been found
that P. seafare is able to tolerate a wide range of water qualities, patiicularly with respect to pH
and water hardness. Recommendations for suitable water quality for P. seafare are a pH of 6.8
- 7.2, with a water hardness (mg/1 CaC03) of 100- 150 mg/1 (Axelrod and Burgess, 1979), while
Chye (1991) recommends a pH of 6.8- 7.2, and a water hardness (mg/1 CaC03) of 46.2 mg/1.
Recommended temperatures for P. seafare range from 25-27 oc (Chye, 1991; Hoedeman,
1975; Mcinerny and Genard, 1989; and Pterovicky, 1984).
Reproductive Biology. P. seafare reaches sexual maturity at about 12 months of age
(Hoedeman, 1975; Petrovicky, 1984; Mcinerny and GetTard, 1989), with spawning behaviour
being displayed after 9 months (Axelrod and Burgess, 1979).
There is little or no sexual dimorphism in P. seafare although there are many so-called
'foolproof' methods to distinguish males from females (Hoedeman, 1975; Axelrod & Burgess,
1979). The only reliable distinguishing feature between sexes is the rounding of the abdominal
region, behind and below the pectoral fins, in mature females (Mcinerny & Gerard, 1989). In
males this region appears to have a convex shape (see Figure 3).
P. seafare is a substrate spawner and as such requires a substrate on which a spawning female
can deposit her eggs. In the wild, large broad leafed plants or flat rocks are suitable substrates.
19
/ N 0
~
Orinoco
Figure 2. Map of the natural distribution of P. seafare (not too scale)
Figure 3. Front view of male and female P. seafare indicating
morphological differences in abdominal region (not to scale)
FEMALE
21
Spawning normally occurs when the temperature reaches 26 - 30 oc at a pH of 6.8 and water
hardness of 80 ppm (Mcinerny and Gerrard, 1979). P. seafare can be classed as a partial
spawner, able to spawn several times over the breeding season, when conditions are suitable.
Spawning is imminent when pairs begin to clean a suitable spawning substrate free of sediment
and algae. Females are able to produce 300- 1,200 eggs per spawning depending on their size
(Chye, 1991). The eggs normally take three days to hatch at a temperature of 25.5 °C. The larvae
remain attached to the spawning substrate for fours days at 25.5 oc, dming which time they feed
endogenously on their yolk sac. The free swimming fry will feed readily on Artemia sp. Nauplii
(instar I), accepting larger zooplankton as they grow. Weaning can commence after Day 14 with
the fry becoming reliant on artificial food by Day 20.
It is beyond the scope of this work to analyse the physiological processes responsible for
reproduction in P. seafare, however a brief comment on general reproductive endocrinology and
in particular oogenesis must be made. Reproductive activity is generally initiated by a range of
environmental cues which result in a series of neurological and hormonal processes that
culminate in production of mature gametes and spawning activity. Lam (1983) highlights a
range of environmental influences capable of influencing and controlling gametogenesis and
spawning in fish. The reproductive physiology of fish has been reviewed by several authors
(Nagahama, 1983; Iwanto and Sower, 1985; Redding and Patino, 1993).
During oogenesis, oocytes become arrested at the diplotene stage of the first meiotic division,
and then commence a period of growth, largely due to the accumulation of yolk material
(Nagahama, 1983). This period of growth is known as vitellogenesis. During vitellogenesis
pituitary gonadotropin levels increase and cause ovarian follicles to begin production of
oestradiol, which in turn leads to production of vitellogenin by the liver (Redding and Patino,
1993). Vitellogenic growth is primarily due to the uptake ofvitellogenin and the consequent
deposition of yolk. Upon finishing vitellogenic growth and the completion of the first meiotic
division, maturation can take place (Nagahama, 1983).
The transition from vitellogenic growth to final maturation is often indistinct (Goetz, 1983).
Oocyte maturation results from the production of oocyte maturation substance (MIS) by ovarian
22
follicle tissue via a two step process. During the maturation phase, the germinal vesicle resumes
its migration, towards the side of the oocyte and the subsequent breakdown of the germinal
vesicle (Redding and Patino, 1993).
The culmination of oocyte maturation is ovulation or the expulsion of mature oocytes (now
eggs) from their follicles. Ovulation is generally induced by gonadotropins however, although
maturation and ovulation share common hormonal stimuli, they are mediated by different
mechanisms (Redding and Patino, 1993). The production of maturation inducing substance or
other follicular steroids in response to gonadotropins may be necessary for ovulation.
Prostaglandin may also play a role in ovulation (Redding and Patino, 1993).
Teleosts and in particular females, have developed highly variable reproductive systems and
behaviour (Nagahama, 1983). Three basic ovarian types can be used for classification of teleosts
(Nagahama, 1983; Redding and Patino, 1993):
1. synchronous - ovary consists of oocytes all at the same developmental stage;
2. group synchronous - ovary consists of 2 or more groups of oocytes at
distinctly different developmental stages; and
3. asynchronous - ovary contains oocytes at all developmental stages.
Asynchronous ovaries are typical in tropical and sub-tropical species of fish and display
spawning behaviour continuously or for extended periods throughout the year (Lam, 1983). P.
seafare is a typical synchronous spawner, capable of continuous spawning throughout the year
and is further complicated by displaying parental behaviour. Spawning behaviour of P. seafare
is described in Bergmen (1967) and Chye (1991).
In mammals prolactin, a pituitary hormone, plays a major role in hormonal control of
reproduction. It promotes secretion of progesterone by the corpus luteum and induces lactation
in females after the birth of their offspring. Prolactin also reduces fetiility in mammals (Raven
and Johnson, 1986), and has also been found to inhibit the secretion ofFSH by the pituitary and
suppress gonadal activity in birds (Blum and Fiedler, 1965). Prolactin is primarily involved in
23
osmoregulatory function and control in fish (Wendelaar Bonga, 1993), however it has also been
implicated in gonad steroidogensis and parental behaviour in some species (Egami and Ishii,
1962; Blum and Fiedler, 1965; Liley, 1979; Singh et al., 1988; Kindler, et al., 1989; Redding
and Patino, 1993; and Wendelaar and Bonga, 1993). The exact role in species exhibiting
parental behaviour in unclear, as is the mechanism by which this parental state is induced and
maintained (Noakes, 1979).
The similarity of the function of prolactin in birds, mammals and fish suggests that as prolactin
is responsible for reductions in fertility in birds and mammals, it may play a role in inhibiting
gonad development, while promoting parental behaviour in egg-guarding species of fish.
Parental Care. P. sea/are exhibit strong parental behaviour if allowed to incubate their eggs
after spawning (Chye, 1991). For example, the pair will normally take turns at either fanning
the eggs and larvae (this involves gently forcing water over them by movement of the pectoral
fins or by blowing water gently from the mouth), or guarding the tetTitory from other fish. The
parents may also eat fungal infested or infertile eggs. The parents may transfer the newly
hatched larvae to another area if threatened (Hoedeman, 1975). As the larvae begin to swim
freely, the parents will herd the fry into a tight ball between them, ensuring that they are kept
away from danger. As the fry get older this behaviour weakens until the pair spawns again
several weeks latter. Bergman (1967) gives an in-depth account of the parental behaviour of P.
sea/are.
Growth. P. sea/are can live a relatively long life in captivity, with reports of fish living for at
least 12 years (Hoedeman, 1975). There is very little information on the growth rates of P.
seafare, although one author reports growth to market size in 4 - 6 months from hatching
(Mcinerny and Gerrard, 1989). Degani (1993) reports growth of P. seafare individuals from 1g
to 4g in a 60 day period at stocking density of 200 fish per 500 L. Similar growth rates are
reported by Low and Wong (1984).
Nutrition. The nutritional requirements and feeding habits of P. seafare also have been poorly
researched, with limited information indicating that P. seafare is carnivorous and feeds readily
24
on zooplankton species (Degani, 1993; Mcinerny and GetTard, 1989; Hoedeman, 1975; Low and
Wong, 1984). Preliminary w01l by Degani (1993) suggests that commercial trout pellets may
provide an adequate diet for growth of this species. Recommended protein levels for other
cichlids are high, for example the .dietary protein levels recommended for Oreochromis
mossambicus are 49- 50 per cent (Macintosh and De Silva, 1984). Degani (1993) reports that
P. seafare also requires high levels of protein (40- 50 per cent) and recommends the use of
commercial salmonid diets. Several commercial growers and wholesalers of P. seafare have
also found salmonid diets to be more cost effective and give better growth than specialised
aquarium foods (pers comm, R. Datodi, 1992).
While there is a broad knowledge base on the general biology of P. seafare, the data reveal little
quantitative information regarding reproductive and growth performance, particularly for the
following:
1. development of morphometric data to allow conversion between length and
weight data and to determine food particle sizes needed for different sized fish;
2. development of hatchery procedures and quantification of hatchery production in
order to determine broodstock numbers;
3. development of growth and survival models for the entire production cycle and
to determine the effects of feeding rate and stocking densities on growth
and survival of P. seafare; and
4. prediction of feed costs, productivity and farm infrastructure needs.
1.4.2 Culture ofP. scalare
P. seafare is cultured throughout the world by both hobbyists and commercial producers. As
previously discussed a range of culture systems is available to the fish fatmer. These systems
can be classified according to the level of production intensity.
Extensive production ofP. seafare. The main commercial method of production of P. seafare is
by extensive production of fish in earthen ponds or pond culture. Pond culture is probably the
25
most popular method used in the world for the culture of aquarium fish and is used in Singapore,
Malaysia, Thailand, China and Florida (USA) for the production of tropical aquarium fish.
Pond culture relies primatily on livefood production in the ponds to feed the fish, although farms
do use varying amounts of supplementary feeding with trash fish and atiificial diets (Stickney,
1994). Stocking densities are low but production is cheap requiring minimal labour input. The
main disadvantage with this system is that very little environmental control is possible.
Therefore if the climate is not suitable for the species, less than optimum growth will be
possible, giving rise to seasonal production. As a result production using this type of culture
system is largely restricted to areas with similar climatic conditions to that of P. sea/are's natural
habitat.
Although pond culture is a widely practised technique for P. sea/are, there is little published
literature. One example is the culture of P. sea/are in net-cages suspended in fertilised earthen
ponds (Low and Wong, 1984). P. sea/are has been found to be a suitable candidate for
polyculture systems and is grown in conjunction with species such as Corydoras sp. and Labeo
erythrusus (Low and Wong, 1984).
Intensive culture of P. sea/are. Intensive culture for P. sea/are is generally characterised by the
use of glass aquaria (Brown and Gratzek, 1982). Another example of P. sea/are production is
given by Degani (1993), where a flow-through system using large indoor tanks (500L) was used.
Damas and Kamio ( 1978) also describe the breeding and rearing of P. sea/are in large outdoor
tanks utilising flow-through water to control water quality. In more temperate regions glass
aquaria and small tanks, generally less than 500 litres, are used. Production is very intensive
with high stocking densities, reliance on atiificial feeds and a relatively higher labour
requirement than extensive systems. Such systems are used widely in cooler climates such as
Europe, particularly Germany, Btitain and northern areas of the USA, where tanks are housed in
heated, insulated rooms. This type of production is generally expensive with production geared
more towards domestic markets. Production from such farms is not competitive in the export
market due to the higher costs relative to major export countries in Asia (Bassleer, 1994). To
date, few papers have been published on the intensive culture of ornamental fish and in
particular on the intensive culture of P. sea/are in recirculating systems.
26
Recirculating systems are generally considered to be the best method for conserving and reusing
water (Muir, 1982; and Stickney, 1994). As water is conserved in these systems so is heat loss
compared with flow-through systems, particularly when the culture system is housed in an
insulated building. Recirculating systems have therefore been used for culturing a variety of
warmwater species of fish in temperate regions such as Tilapia, carp and channel catfish.
The design of recirculating systems may vary considerably, but generally incorporate a culture
tank to house fish, a biological filter to remove metabolites from the water and a pump to move
water around the system. The design, operating parameters and management of recirculating
systems have been reviewed by several authors (Wheaton, 1977; Spotte, 1979; Tiews, 1981;
Muir, 1982; Rogers and Klemetson, 1984; Forteath, 1990; and Stickney, 1994). Although the
use of recirculating systems is relatively untried for the culture of ornamental species, it is
thought that such systems would be more suited to large-scale commercial production than
traditional glass aquaria for the following reasons:
1. larger production tanks result in reduced labour costs per fish (ie. economies of
scale);
2. water quality management is easier in recirculating systems;
3. there are indications that higher stocking densities may be possible; and
4. conservation of water and heat.
For these reasons it has been proposed that the use of recirculating systems for the culture of P.
sea/are in a controlled environment would be the best culture technology to use in a temperate
region, such as Tasmania. The design and management of such a culture system is addressed in
subsequent chapters.
1.4.3 Marketing and economic considerations in the production of P. seafare
Australia offers good opportunities for ornamental fish production, with a well established
infrastructure already existing for the aquaculture and ornamental fish industries. The
Australian ornamental fish culture industry is currently undergoing a period of rapid expansion
27
with demand for ornamental fish expected to grow (Treadwell et al., 1992). Production of
ornamental fish in Australia is primarily for import replacement (Lee, 1991), with the
competitiveness of domestic producers, both here and internationally, improving due to the
rising cost of imported ornamental fish, and the continuing interest in high quality fish
throughout the world (Bassleer, 1994 ).
Market assessment. With the apparent increase in culture opportunities in the ornamental fish
industry, there is a need to target and assess potential species for commercial production. As
previously mentioned such a candidate is P. seafare, for which there is no longer any reliance
on the wild fisheries for supply (Axelrod and Burgess, 1979; and Brown and Gratzek 1982).
As a result of a disease outbreak known as "Angelfish syndrome" in 1987 an international
shortage of P. seafare has occmTed (Lambourne, 1991; and Gratzek et al., 1992). The causative
agent is thought to be viral, although considerable research since its discovery has revealed little
information regarding the exact mechanisms of the disease (Lambourne, 1991; and Gratzek et
al., 1992). The disease has severely reduced the production of P. seafare throughout the world,
creating a demand for healthy disease free stock (Gratzek et al., 1992).
Industry sources estimate that the market size and value for P. seafare in Australia is
approximately 350,000 fish per annum worth $300,000 (pers comm R. Datodi, 1992). However,
confirmation of industry estimates is difficult due to the lack of market data. There are few data
on the nature of the domestic production of P. seafare, or ornamental fish in general. An
exploratory industry survey is therefore needed to help establish trends and a clear picture of the
industry.
Economics. The continuing demand for P. seafare in the ornamental fish industry and the
inconsistent nature of supply (due to Angelfish syndrome) indicates that P. seafare has
commercial potential. This potential appears particularly good for import replacement for the
Australian ornamental fish industry. However, data on the economics of producing P. seafare
are unavailable, as for other ornamental fish species both in Australia and overseas. Therefore
there are no benchmark studies from which comparisons can be made for the present study.
28
The culture potential of a species can be assessed by developing different financial scenarios,
based on the interactions between the biological and physical submodels developed. These
financial scenarios can be illustrated by financial statements such as cash flow, profit and loss
and balance sheet. Such information is useful in illustrating the economic potential of a culture
candidate and can be used for comparison with other species and other types of economic
investments.
1.4.4 Research needed for development of farm design
This analysis of the current status of knowledge of the biology, culture and economics of P.
seafare highlights some significant deficiencies in these areas. In particular these data include:
1. little or no quantitative biological data regarding, reproduction, growth and
nutrition of P. seafare;
2. little or no data regarding intensive culture methods and technology for
P. seafare; and
3. little or no data on the market potential or economics of producing P. seafare in
Australia or overseas.
In order to obtain a meaningful assessment for the culture potential of P. seafare for Australian
markets these deficiencies must be addressed. The following section highlights deficiencies in
these data.
1.5 Research aims for this study
The aim of this study is to assess the feasibility of producing P. seafare in an indoor, intensive
culture system, situated in Launceston, Tasmania. This will be assessed using bioeconomic
principles by developing biological, physical and economic sub-models. Emphasis for this
research will however focus on the development of the biological and marketing/economic
sub-model. Development of the physical sub-model will be based largely on experiences of
commercial producers of ornamental fish and the methods used in the biological experiments.
29
The biological sub-model, detailed further in Chapter 3, will focus primarily on the following
areas:
1. development of morphometric data to allow conversion between length and
weight data and to determine food particle sizes needed for different sized fish;
2. development of hatchery procedures and quantification of hatchery production in
order to determine broodstock numbers;
3. development of growth and survival models for the entire production cycle and
to determine the effects of feeding rate and stocking densities on growth
and survival of P. scalare; and
4. prediction of feed costs, productivity and farm infrastmcture needs.
The economic sub-model will focus primarily on market analysis (detailed in Chapter 4) and
includes an industry survey to determine the nature of the ornamental fish industry in Australia
and to establish the market potential and possible marketing strategies for sale of P. scalare in
Australia. These data, in conjunction with the biological and physical submodel data, will be
used to develop a financial profile of a fictitious enterptise producing P. scalare in an indoor,
intensive culture system, situated in Tasmania (detailed in Chapter 5) to assess its culture
potential.
30
CHAPTER2
GENERAL EXPERIMENTAL PROTOCOL
This chapter provides the general experimental protocol used for the experiments performed
on P. seafare in this study.
2.1 Experimental animals and facilities
The experiments were conducted at Tasmanian Ornamental Fish Farms, a commercial
ornamental fish hatchery located in Launceston, Tasmania. Experimental animals were held
at the facility for at least three generations.
The hatchery facilities consist of a 30 m2 brick building, which is insulated with 60 mm of
isolite sheeting. This laboratory holds over 150 glass aquaria with volumes ranging from
20 L to 100 L. These tanks are maintained with undergrave1 filters and aeration is provided
by two Sakuragawa Hiblow 80 air pumps. An air temperature of 26 ± 2 oc is maintained
throughout the year by two 2 kW oil filled heaters controlled by thermostats. Lighting is
provided by fluorescent light tubes with a photoperiod of 14 hr light, 10 hr dark.
2.2 Water quality monitoring
Samples of water were taken from the tanks prior to morning tank cleaning and water
changes. Ammonia (NH4-N), nitrite (N02-N), and nitrate (N03-N) levels were determined
using a Hach DR 2000 spectrophotometer (Anon, 1989). The dissolved oxygen levels were
measured with a Hanna HI 8543 Portable Dissolved Oxygen Meter. The Dissolved oxygen
31
levels were 7 ± 2 ppm or over 95 per cent saturation at 25 ± 1 °C. The pH was measured
using a Hanna model HI 8424 portable pH meter. The pH meter was calibrated weekly using
standard calibration techniques. The pH was maintained close to a pH of 6.8 using the
following procedure:
1. low pH (ie. acidic conditions) calcium carbonate was applied at the rate of 5
ml per pH unit per 100 L; and
2. high pH (ie. alkaline conditions) sodium sulphite B.P. was applied at the rate
of 2 ml per pH unit per 100 L.
Water hardness was dete1mined using an Aquasonic Water Hardness Test Kit as mg/1 of
CaC03 • This kit utilises the titration reaction of EDTA in the presence of indicator organic
dyes to indicate the presence of CaC03 •
2.3 Water supply
Water used in the facility is delived from the Launceston city water supply. An analysis is
given in Table 4. The water is filtered to reduce the level of suspended solids by a series of
cartridge filters, viz. 50 p,m, 15 p,m, 5 p,m. A 5 p,m activated carbon filter is used to reduce
the levels of contaminants such as residual chlorine and dissolved organic compounds. The
water is then stored in storage tanks (3 x 300 L capacity) for at least 3 days, where it is
vigorously aerated to eliminate residual chlorine used to treat city water (Spotte, 1979).
During this time the water is passively heated to just below ambient room temperature at 25
± 1 °C.
2.4 Experimental tanks and tank systems
2.4.1 Broodstock tanks
Broodstock holding tanks were constructed of 6 mm glass, with the dimensions of 720 x 460
x 350 mm. The approximate water volume was 90 L. Filtration was provided in each tank
via a commercial undergravel filter with a filter plate of 585 x 290 x 20 mm, with two 25
32
Table 4. Comparison of Launceston City Water with general
fish culture water quality standards and recommendations
Chemical Launceston City WaterA General Water Quality Standards for
Culturing Fish8
Total Dissolved Solids 70ppm <400
Ammonia (unionized NDA < 0.02 NH3)
Nitrate 0.1 ppm < 1.0
Nitrite NDA <0.01
pH 7.01 6.7- 8.6
Hardness (as CaC03) 27ppm 20-200
Chloride 8.6ppm <0.003
Fluoride 0.96 -Aluminium (total) 0.05 -Arsenic <0.005 -Cadmium <0.001 <0.0005 (soft water)
<0.003 (hard water)
Chromium <0.001 NDA
Cyanide < 0.05 ppm <0.005
Iron 0.05 <0.01
Copper 0.01 <0.006
Manganese <0.01 <0.01
Selenium <0.001 <0.05
Lead <0.001 <0.02
Sodium 5.7 -Sulphate 7.9 -Mercury <0.001 <0.0002
Zinc <0.01 0.03
Aldrin <0.001 < 0.01 ug L-1
Dieldrin <0.001 0.005 ug L-1
Chlordane <0.001 0.004 ug L-1
Key.
No data available
A Govermnent Analyst Laboratory, Hobart Tasmania 2/3/93.
B Langdon, 1988
33
mm uplift tubes. The biofilter substrate consists of a 10 mm sheet of upholstery sponge, laid
over the filter plate, covering the entire bottom of the aquarium, which was covered with 10
mm of 7 mm aggregate cmshed dolerite gravel.
2.4.2 Egg and larval incubation tanks
Egg and larval incubation tanks were constmcted of 4 mm glass, with dimensions measuring
360 x 260 x 250 mm. These tanks contained approximately 18 L of water. No filtration was
provided for these aquaria, and gentle aeration was provided by a small airstone.
2.4.3 Nursery tanks
The nursery tanks were constmcted of 6 mm glass, with the dimensions of 460 x 360 x 350
mm, with an approximate volume of water of 40 L. Filtration was provided in the same
manner as the broodstock holding tanks, with each tank having a commercial undergravel
filter with a filter plate of 290 x 290 x 20 mm, with one 25 mm uplift tubes. Biofilter
substrate consisted of a 10 mm sheet of upholstery sponge, laid over the filter plate, covering
the entire bottom of the aquaria and with a 10 mm layer of 7 mm aggregate crushed dolerite
gravel.
2.4.4 Small scale recirculating ftlystem
The experimental grow-out system consisted of 12 x 8 L glass aquaria (measuring 300 x 150
x 180 mm) with a working volume of7 L, sharing a common biofilter (see Figure 4). Water
flowed through the experimental tanks at 0.5 L minute, allowing a full water exchange every
14 minutes or 4.3 times per hour.
The biofilter was constructed as a trickle filter, from a 10 L plastic bucket with 4 mm holes
in the bottom. The filter substrate consisted of 8 L ofDupla- Biokascade bioballs. Water
flowed down through the filter substrate and was then collected in a 25 L sump. The water is
then pumped back through the experimental holding tanks via a Project canister filter,
containing 2 L of Dupla - Biokascade bioballs and glass filter wool to remove fine sediments,
at 800 L per hour.
34
w v.
/. Inlet manifold Bypass tap
\ Effluent manifold
Dacron filter ----11~~~~ Airline
Splash plate flow
Inlet tap f
A: ..... ,--~ . --.
I
•••••• •••••• .. ·~·.~.• It*••• -BiobalLs---.,., •• "tti LJ
I ..-- Airstone - Inlet manifold
Submersible
I • pump
•••••••• ·······: •••••• ••• ~ ... t-t. --- Reservoir
Figure 5. Diagram of expe1imental recirculating system used in growth trials for P. seafare juveniles
2.5 Anaesthesia of fish
Prior to handling, experimental fish to be anaesthetised were placed in a 2 L bucket of water
and lightly anaesthetised using a 10 per cent Benzocaine solution at the rate of 2 ml per 10 L.
Fish were sufficiently anaesthetised when they began to float 'belly up', where-upon they
were removed. The time taken to anaesthetise the fish varied with the size of fish, but
usually occmTed within 3 - 5 minutes.
After the appropriate experimental procedures had been canied out, the fish were placed in a
1 OL bucket containing approximately 7L of fresh water that was lightly aerated. The fish
recovered quickly (usually within 3 minutes) and were then returned to the approptiate
tanks.
2.6 Length measurement
Throughout the experiments the Standard Length (Ricker, 1979) is used rather than total
length because of the large variation in caudal fin length found in P. scalare.
Juvenile and adult fish were anaesthetised (see section 2.5), and then placed on damp paper
towelling on a bench. The standard length (see Figure 5) was determined to the nearest 0.5
mm using a pair of Vernier callipers.
2. 7 Weighing procedure
Prior to weighing, all the fish in the experimental tank were netted and anaesthetised (see
section 2.5). The fish were then individually blotted dry on paper towelling for 10 seconds
to remove external water and weighed in a plastic container with approximately 800 ml of
water on an electronic balance to the nearest 0.01 gram. Fish were then placed in a recovery
bucket before transfer back to their respective experimental tanks.
36
.....- Dorsal fin length
Figure 5. Lateral view of P. seafare indicatinglength measurements
used in this study (not to scale)
Upper jaw
length
37
2.8 Growth calculations
The following calculations were used to calculate growth rates and feeding efficiencies:
Absolute Growth Rate = Final Weight- Initial Weight (Hopkins, 1992). Time (days)
Specific Growth Rate = ln(Final Weight) -ln(lnitial Weight) x 100 Time (days) (Hopkins, 1992).
FCR = Weight of Feed Offered wet Weight gain (Laird and Needham, 1988)
Conversion efficiency = (Growth Rate I Ration) x 100 (Brett, 1979)
Condition Factor
2.9 Feeds
= (Weight (g) I Length 3) x 100 (Merola and de
Souza, 1988)
A commercial salmonid diet was used throughout the experiments as recommended by
Degani (1993) (see Section 1.4.1). The salmonid diet consisted of a salmon starter pellet
produced by Gibson's Feeds in Hobart Tasmania and was used as a food source in both
broodstock and growth expetiments. Table 5 provides a basic analysis of the salmonid diet
used during the study.
Table 5. Composition of Gibson's salmon starter pellets
Ingredient %
Protein 50.23
Lipid 13.89
Carbohydrates 10.06
Salt 0.05
Omega 6 1.23
Omega3 3.15
Other 21.39
Total 100
Gibson's salmonid diet has proved to be an acceptable feed for P. seafare held at the
Tasmanian Ornamental Fish Farm. No attempt is made here to compare this diet with other
salmonid feeds available in Australia.
2.10 Statistical methods
Statistical analyses were performed using The Student Edition ofExecustat® (Anon, 1991)
on an IBM compatible (ie. means, Student's t-test and ANOV A), with curve fits and linear
regressions being determined by using the method of least squares and plotted using Cricket
Graph III on Apple Macintosh. The following calculations were used in the analyses.
Notation - single sample
- more than one
sample
n =sample size (number of non-missing observations)
Xi = value of the ith observation in a sample
XliJ = value of the ith smallest value in a sample
ni = number of non-missing observations in jth sample
xi = average of the fh sample
si = standard deviation of the jth sample
2.10.1 Mean, standard deviation and variance
The following calaculations were used to determine the mean, variance and standard
deviation of experimental populations.
Mean:
Variance:
Standard deviation: s=P
39
2.10.2 Students t-Test
Analysis of sample data from two populations ( eg when two treatments were used) was
performed using a T -test to compare both the means of the two populations. The null
hypothesis was that the difference in the two population means was equal to zero. The null
hypothesis was rejected when the calculated P value was less than the confidence level (P =
0.05) (Anon, 1991). The following calculations were used:
Confidence interval
difference in means:
Confidence interval
for ratio of variances:
(x 1 - Xz) ± tm; al2 ( J [siln1 + s~lnz J ) where (11m) = (c21v) + (1 - c) 21w
c = ( siln1) I [siln1 + s~lnz J
~ [ sils~) IFv,w; al2, [ sils~) IFv, w; 1 - al2l
2.10.3 Analysis ofvariance (ANOVA)
Analysis of variance was used for comparing the means of more than two samples ( eg more
than two experimental treatments). The null hypothesis was that the difference in the two
population means was equal to zero and was rejected when the calculated F value ( eg.
between samples variance I within samples variance) is equal to or is greater than the
tabulated value for P = 0.05 (Fowler and Cohen, 1992).
The following calculations were used:
k = number of samples
v. = n.- 1 J J
Pooled variance: Sp2 = [ t VjSj 2 ] l(n - k)
;=l
40
Confidence
interval: Xy ± In-k; cd2 ( Sp/ jfij J
2.1 0. 4 Regression analysis
Regression analysis was used to quantify relationships between experimental fators through
line fitting using the method ofleast squares (Kreyszig, 1983). Regression analysis was
performed using CA-Cricket Graph III on the Macintosh computer (Anon, 1992). The line
and curve fit calculations were performed using the following equations:
Linear form y = a 0 + a1x valid range: - oo :::;; x :::;; oo,- oo :::;; y :::;; oo
Power form y = aoX01
Coefficient of
determination: r 2 = E <Y-v)2
E (y-Ji)2
valid range: x > O,y > 0
The following chapter utilises these general experimental procedures in a series of
experiments used for the development of a biological sub-model for P. seafare.
41
CHAPTER3
DEVELOPMENT OF BIOLOGICAL SUB-MODEL
The general biology of P. seafare has been discussed in Section 1.4.1. However these data
provide little quantitative information on which a robust sub-model can be based. In
particular several key areas indicated in Section 1.5, have been identified as essential for
development of this sub-model. This chapter provides additional data for these key areas
through experimentation into the following:
1. length-weight relationships and dete1mination of food particle size;
2. hatchery production, with emphasis on the effect of artificial incubation of
eggs on the reproductive performance of P. seafare under commercial culture;
3. growth and survival of P. seafare during the nursery culture phase;
4. effect of ration level on growth, survival and feeding efficiency; and
5. effect of stocking density on growth survival and fin factor.
The following sections detail the methods, results and discussion for these experiments.
3.1 Length- weight relationships and determination of food particle size for P. seafare
3.1.1 Introduction
Basic morphometric data are important for computing of growth models. Of patiicular
interest is the relationship between length and weight of fish as defined by the general
formula:
Weight = a Length b; where a and b are constants (Hopkins, 1992) .... 1
42
The length - weight relationship for a cultured species is a useful tool for the aquaculturalist,
allowing easy conversion between weight and length of fish. This is of particular use to
ornamental fish producers who must satisfy product definitions based on length, whereas
management practices such as feeding and stocking rates are normally based on biomass or
fish weight. Easy conversion between the two measurements is therefore impotiant in fish
management. An extensive literature search has revealed no such data for P. sea/are.
Mouth size of fish is important to the aquaculturalist, as food particle size may act as a
limiting factor for fish, particularly juvenile fish feeding on both natural prey organisms and
artificial diets (Dabrowski and Bardega, 1984). When presenting food particles, they should
be of a size that is able to be easily engulfed by the fish's mouth. If the particles are too large
they may be too difficult to engulf or to ingest quickly; when particles are too small they may
remain undetected or be difficult to capture (Hasan and Macintosh, 1992). Inconect food
particle size can compromise the management of an aquaculture system and may cause poor
FCR and wastage of food increasing costs in production and deterioration of water quality.
At present food particle size preferences for P. sea/are consist of recommendations for
feeding selected zooplankton species during fry rearing (see Section 1.4.1). Therefore in
order to provide a suitable nutritional regime to P. sea/are in intensive culture, more data are
needed to determine particle size requirements.
3.1.2 Materials and methods
P. seafare individuals, from larvae to adult size (n = 180), were selected at random from the
culture tanks at the Tasmanian Ornamental Fish Farms. The fish were then sacrificed and
preserved in a solution of 10% formal calcium for 24 hours at room temperature, for future
measurement.
The fish were weighed to the nearest 0.01 g to attain the wet weight (see section 2.7). The
standard lengths were then measured to the nearest 0.5 mm (see section 2.6). No allowances
were made for possible shrinkage of specimens during preservation (Hasan and Macintosh,
1992). Length and weight data were plotted and an exponential curve-fit perfonned using
Cricket Graph III (see Section 2.10.4).
43
The length of the upper jaw was measured to the nearest 0.5 mm, using a dissecting
microscope and eyepiece gradicule for small specimens or a pair of Vernier callipers for
larger specimens. The mouth size or gape was then calculated using the formula:
Gape =v2 x Length ofupperjaw (after Hasan and Macintosh, 1992).
A linear regression of the calculated gape and standard length data was plotted using Cricket
Graph III, to define the relationship between calculated gape and standard length for P.
seafare (see Section 2.10.4).
3.1.3 Results
The standard-length and weight data for P. seafare are presented in Figure 6 and were found
to have the following curvi-linear relationship:
Weight= 0.000037 (Standard Length), 3·1 r2 = 0.989, (n = 180) .... 2
The upper jaw-length and standard-length data are presented in Figure 7 with the following
linear relationship:
Upper jaw-length= 0.049 (standard-length)+ 0.044, r = 0.901, (n = 180) .... 3
Figure 8 shows the relationship between the calculated gape and standard-length. A linear
regression indicated the following relationship:
Gape= 0.032 (Standard Length)+ 0.764. r2 = 0.900, (n = 180) ... .4
44
.4. V1
...-....
.::3 :c
OJ)
·o:; ~
6
5
4
3
2
1
0
0 10 20 30
Total-Length (mm)
40 50
Y = 0.00037x3.123
r2 = 0.986
Figure 6. Exponential regression of length-weight data for P. seafare (n = 180)
+:>. 0'.
'? 5 ..c o:n c: ~ :;: "' .,.., .... <l) p.. p..
:::>
3
2.5
2
1.5
0.5
0 0 10 20 30
Standard length (mm)
y = 0.049x + 0.044 r2 = 0.901
40 50
Figure 7. Linear regression of standard-length and upper-jaw length data for P. seafare (n = 180)
+;.. -......)
E' g 0)
~ OJ) .., ~ :; <)
;::; u
2.5
2
1.5
y = 0.032x + 0.764 ~ = 0.900
0.5 +----.-----,-----....----..-----. 0 10 20 30 40 50
Standard-length (mm)
Figure 8. Linear regression of standard-length and calculated gape for P. seafare (n = 180)
3.1.4 Discussion
The length weight data for P. seafare were found to fit the general equation detailed in
Section 3.1.1 (see Equation 1 ). The validity or usefulness of this relationship depends on
obtaining data on a wide range of different sized specimens, including age 0 (Ricker, 1979).
Ricker (1979) also indicates that small sample populations may bias data and result in
deviations from actual to calculated length - weight parameters. Figure 7 indicates the close
fit of the data to the exponential regression equation (see Equation 2) and is further validated
by the high r2 value. This high r value indicates the good correlation between the
standard-length and weight data for P. seafare over the range examined. This would suggest
that the sample population was large enough to give a reliable indication of the length-weight
relationship for P. seafare and that the mathematical relationship established here can be
used with a high def,rree of accuracy.
Knights (1985) states that the food particle sizes available to fish are determined by the ease
of location and capture for small particles (lower limit) and by the size of the mouth or gape
(upper limit). Particle size preference may also be influenced by the particle taste, hardness,
abrasiveness and food particle density (Knights, 1983; Knights, 1985; Khada and Rao, 1986;
and Hasan and Macintosh, 1992). Dabrowski and Bardega (1984) note that while under
experimental conditions fish may consume food particles equal to the gape, field
observations indicate that the prefeiTed particle size may in fact be much smaller than the
gape. Knights ( 1985) indicates that for hard and or abrasive food particles, the prefeiTed
particle size is generally 0.4- 0.6 of the gape, whereas for soft particles the prefeiTed size is
generally equal to that of the gape.
Although experimentation is needed to confirm the preferred particle sizes for P. seafare, for
the purposes of this study it will be assumed that preferred patiicle size will be between 0.4
and 0.6 of gape. Table 6 indicates recommended particle size for size classes of P. seafare,
based on the standard-length, weight and calculated gape previously detailed.
48
Table 6. Recommended food particle sizes for P .seafare
Size of P. sea/are Mouth size Food Particle
SIZe
Weight (g) Length (mm) (mm) Diameter (mm)
0.16 15 1.24 0.50- 0.74
0.4 20 1.40 0.56- 0.84
0.8 25 1.56 0.62- 0.94
1.4 30 1.72 0.69- 1.03
2.26 35 1.88 0.75 - 1.13
3.42 40 2.06 0.82- 1.24
4.93 45 2.20 0.88- 1.32
6.84 50 2.36 0.94- 1.42
A regression of the calculated gape and standard-length (see Figure 8) indicates that mouth
size increases linearly with standard length. However these data show some variation from
the calculated regression line (see Equation 4) which can be attributed to two possible
sources:
1. changes in the upper jaw-length and standard-length relationship due to
morphomettic changes during growth; and
2. poor measuring technique or some other source of experimental error.
Fmther experimentation may improve the regression through using a larger sample
population. These data and their regression however give a good indication of the
relationship between the mouth size and standard length for P. seafare over the size ranges
used. Although food particle size preference must at some stage be confirmed
experimentally, the predictions made here are a useful starting point.
49
3.2 The effect of incubation technique on ova and larval survival of P. sea/are
3. 2.1 Introduction
A prerequisite for the intensive production of a species is the ability to provide seed in a
consistent, reliable manner (Shepherd and Bromage, 1988). Reliance on natural seed
production for stocking of culture systems can be unreliable, and may be impractical if the
wild fisheries have been decimated or culture of the species is to be undetiaken at a distance
from its natural habitat (Shepherd and Bromage 1988, Pillay 1990).
The reliable production of seed for P. seafare is essential as wild fisheries of this species
have been over-exploited (Axelrod and Burgess, 1979). It would also be impractical to
transport wild caught fry to culture operations throughout the world. Therefore a reliable
protocol for production of seed is vital to the success of a commercial culture operation and
to provide a means of selective breeding.
P. seafare has been produced on a commercial basis since the 1940's (Brown and Gratzek,
1982), and there is a basic understanding of the reproductive activities of this species (see
Section 1.4.1 ). However, no data have been found in the literature on quantifying the
fecundity of P. seafare. Brown and Gratzek (1982) state that artificial incubation of P.
seafare eggs and larvae promotes increased hatch rate and survival of larvae over natural
incubation, however there are no quantitative data available on the effect of egg and larvae
incubation method on the fecundity, hatch rate, larval survival and larval size of P. seafare.
Such data are important in the development of the biological submodel. The aim of this
experiment was therefore to determine the fecundity of P. seafare under commercial
hatchery conditions, and the effect of egg and larval incubation method on fecundity and
larval size and survival.
3.2.2 Materials and methods
Twenty pairs of breeding P. seafare, maintained in separate tanks, were sexed, measured, and
randomly assigned to one of two treatments viz:
50
1. the eggs produced by 10 pairs were removed from the parental tank
as soon as possible after spawning and incubated artificially; and
2. the eggs produced from 10 pairs were left in situ and incubated
naturally by the parents.
Spawning activity was monitored for a period of 55 days from mid-November to January in
1992/93. During this time the following data were recorded for each spawning: number of
eggs, time to hatch, hatch rate, larval incubation time and larval survival.
Broodstock management. Broodstock pairs were maintained in glass aquaria (see Section
2.4.1 ). Spawning substrate in the form of a 200 x 70 x 10 mm ceramic tile was provided for
each pair.
The pH was measured every second day and maintained at 6.8 (see Section 2.2) Nitrite and
nitrate levels were determined weekly (see Section 2.2) prior to a 25 per cent water change
being carried-out. Pairs were fed ad libitum, three times daily with salmonid pellets (see
Section 2.9).
Natural incubation of eggs and lmvae. Breeding pairs were monitored daily for spawning
c\.ctivity. Upon spawning the temperature, pH and water hardness (see Section 2.2) were
recorded as well as time and number of eggs. The spawning substrate was then removed
from the broodstock tank and placed in a shallow dish containing sufficient water from the
broodstock tank to cover the eggs and substrate. The eggs were counted and the substrate
and eggs returned to their tank and the parent fish allowed to maintain their eggs naturally
(see Section 1.4.1). During incubation of the eggs feeding of the broodfish and water
quality management practices as described above were continued.
Artificial incubation of eggs and larvae. For artificial incubation, the eggs were removed on
their substrate and counted as above. The eggs were then placed in an egg incubation tank
(see Section 2.4.2). An airstone was positioned at the base of the tile so that a gentle stream
of air bubbles passed over the eggs. Malachite green was used at the rate of 0.15 ppm to
51
minimise fungal infection of eggs. A 50 per cent water change was made after hatching and
again after first swim-up of the fry.
Fecundity measurements. Fecundity of a female can be expressed several ways. Rana
(1988) found that for multiple spawners, fecundity measured as the number of eggs per
spawn rather than ovmian counts gave the most reliable results. Ovarian counts using
histological sections reveal a wide range of oocyte sizes, making it difficult to determine
which oocytes will be spawned next leading to inaccurate measurements. For this reason the
fecundity was determined by egg counts rather than ovarian counts.
The following formulae were used for calculating fecundity:
Cumulative fecundity =
Absolute fecundity =
Relative fecundity =
total number of eggs produced during
experimental period
number of eggs per spawn
total number of eggs produced during
experimental period I weight of female
Hatch rate and larva/length. In both the natural and artificial incubation methods, the eggs
were monitored for development and signs of hatching. On the first signs of hatching, time
was recorded. After all the viable eggs hatched, the number of larvae were counted by
carefully siphoning them into a petri-dish with a grid and counted under a dissecting
microscope at low magnification. Percentage hatch rate was then calculated. The standard
length of a sample of 40 larvae was measured to the nearest 0.01 mm using an eyepiece
gradicule on a stage microscope; the larvae were then returned to their tank and the mean
standard-length calculated (see Section 2.10.1).
Data analyses. From the spawning data, the mean and standard deviation of the spawning
frequency and inter-spawning interval were determined (see Section 2.10.1). The data were
compared using a Student's t-test (see Section 2.1 0.2). A graph of the number of spawnings
each pair produced during the expelimental period was plotted.
52
Fecundity measurements for the two treatments were calculated and statistically compared
using Student's t-test (see Section 2.10.2). The means and standard deviation were also
determined (see Section 2.10.1). The relationship between female weight and relative
fecundity was plotted and a linear regression used to quantify the relationship (see Section
2.10.4).
The hatch rate, larval length, and larval survival to first swim-up for the two treatments were
compared using a Student's t-test (see Section 2.10.2).
3.2.3 Results
Spawning frequency. The number of spawns during the expelimental period per breeding
pair varied from one to five spawnings over the 55 day experiment. The spawning
frequency varied from 1.7 ± 0.48 times per 55 days using natural incubation of eggs to a
spawning rate of 3.9 ± 0.87 times per 55 days when using artificial incubation of eggs.
These spawning frequency and inter-spawning data are summalised in Table 7.
Table 7. The spawning frequency of P. scalare with different methods
of egg and larval incubation during experimental period of 55 days (n = 20)
Natural Incubation Artificial Significantly
Incubation Different (P < 0.05)
Number of spawns 1.7 ± 0.48 3.9 ± 0.87 yes
Inter-spawning 28.62 ± 10.45 11.88 ± 5.54 yes
Interval (days)
The inter-spawning interval was significantly higher (P < 0.05) for the natural incubation
(28.62 ± 10.45 days) treatment than for the artificial incubation method (11.88 ± 5.54 days).
The inter-spawning interval was also found to be affected by the incubation method, with
the inter-spawning interval for natural incubation significantly higher than that of artificial
incubation (P < 0.05). Figure 9 shows the number of spawnings for each replicate pair
duling the experimental period.
53
Vl +:>-
"' b1) c ·c: ~
"' 0..
6-
5-
4-
,: 3-0 ... '-'
..0 E z 2-
l-
0
r:-:-:
6
5
"' b1) 4 c ·c: ~
"' 0..
"' "--' 3 0 >-< '-'
..0 E
-::-:7:
I I Qr-:'1 ~
s 0 j ... . .. ... ... . .. ... ... ...
I I I I I I I I-~
:::: 2 z
0 II) l J=,{'l !\"•! l "(I!).!-...,! '1 J f::("l 1\)1 I }I [\i"\1
2 3 4 5 6 7 8 9 10 2 3 4 5 6 7 8 9 10
Replicate pair number Replicate pair number
Natural egg incubation Artificial egg incubation
Figure 9. Number of spawnings for P. seafare broodstock pair during the 55 day experimental period
Egg production. Fecundity was found to vary with the choice of egg incubation method.
Data for absolute fecundity, cumulative fecundity and relative fecundity are shown in Figures
10, 11, 12 respectfully. These fecundity data are summarised in Table 8.
Table 8. Fecundity of P. scalare using artificial and natural incubation of
eggs and larvae (n = 20)
Number of eggs Significantly
Natural Artificial Different (P < 0.05)
Incubation Incubation
Cumulative Fecundity 374 ± 177 709 ± 236 yes
Absolute Fecundity 257 ± 66.7 176.8 ± 70.2 yes
Relative Fecundity 5.6 ± 2.34 21.24 ± 10.33 yes
Hatch rate, Larval size and survival. A students t-test showed no significant difference (P >
0.05) between the hatch rate of natural and artificial incubated eggs during the experiment.
The hatch rate for naturally incubated eggs was 90.67 ± 3.25 per cent, while the hatch rate of
eggs naturally incubated was 89 ± 3.54 per cent. Results for larval size and survival are
presented in Table 9.
Table 9. Mean larval size and survival rates for P. scalare using
natural and artificial incubation of eggs and larvae
Natural Artificial Significantly Different
Incubation Incubation (P < 0.05)
Larval Length (mm) 2.6 ± 0.05 2.61 ± 0.03 no
(n = 40)
Larval Survival (%) 91.5 ± 4.94 91.69 ± 4.22 no
(n = 20)
The larval size and survival rates were not significantly different (P > 0.05) between the two
treatments (Student's t-test).
'Jo ---.]
'"0 .., (.) ::l
"d 0 .... 0..
"' ell ell ..,
4-. 0 .... 0
.D E ::l :::
~ 0
E-
1250 I
1000
750
500
250
• o I
20
1250
I 1000
"d
I e ..,
(.) e ::l e '"C) • 0 .... 750 0..
"' ell
500~ e ell ..,
'--< e • 0
•e .... .., • .D • E § e •
• ~ e 0
250 •• e E-
I I I I I I I 0 30 40 50 60 70 80 90 20 30 40 50 60
Weight (g) Weight (g)
Natural incubation Artificial incubation
Figure 11. The effect of egg and larval incubation method on cumulative fecundity for different sized female P. scalare (n = 20)
•
70 80 90
'J)
00
E '" ... OJ) ... <l) p.. Vl OJ) OJ) <l)
....... 0 .... 2 E ;:::l
z
30.,
25
20
15
10
• 5-l
0 20
30
I • 25
E • '" ... 20 OJ) • .... <l) p.. • U'l OJ) •• OJ) 15 • <l)
....... 0 • ....
• 2 E 10 ;:::l
• z 6/b • I •
'\ • 5
• 0
30 40 50 60 70 80 90 20 30 40 50 60 70
Weight (g) Weight (g)
Natural incubation Artificial incubation
Figure 12. The effect of egg and larval incubation method on relative fecundity for different sized female P. seafare (n = 20)
•
80 90
3.2.4 Discussion
Spawning frequency. P. sea/are is a multiple spawner and is able to spawn several times
during the year if water quality and temperature is maintained near the optimum for
spawning and nutrition is adequate (Axelrod and Burgess, 1979; Brown and Gratzek, 1982).
As is common with multiple spawners (Axelrod and Burgess, 1979), P. sea/are has a low
absolute fecundity and large numbers ofbroodstock must be maintained to produce large
numbers of fry.
Verde gem and McGinty ( 1987) repmied that a reliable way to increase egg production in
multiple spawners is to increase the spawning frequency. The removal of eggs or recently
hatched progeny from brooding pairs has been found to increase the spawning frequency in
other egg-guarding cichlid species (Verdegem and McGinty, 1987; Rana, 1988; Brown and
Gratzek, 1982). The results of this experiment also indicate that removing the eggs from
breeding pairs will increase the spawning frequency of P. sea/are. The spawning rate was
found to be significantly higher (P < 0.05) using artificial incubation, with a spawning rate of
3.9 ± 0.87 times per 55 days, than using natural incubation, with a spawning rate of 1.7 ±
0.48 times per 55 days. These differences are highlighted by Figure 9, which shows the
number of spawns during the experimental period for each breeding pair.
The change in spawning frequency resulted in a significant decrease to the inter-spawning
interval from 28.62 ± 10.45 days for natural incubation, to 11.18 ± 5.54 days for artificial
incubation. These data confirm reports from Brown and Gratzek (1982) that removing eggs
from breeding pairs of P. seafare can lead to spawning on a weekly to fortnightly basis.
Similar findings for Tilapia (another member of the Cichlid family) females indicate that
removing eggs after spawning will decrease the inter-spawning interval from 30- 59 days to
12- 16 days (Rana, 1988). The mechanism through which egg removal influences spawning
frequency is not known, however there are some indications that the presence of eggs and/or
fry may induce a hormonal block to reproductive behaviour in cichlids and other groups of
fish exhibiting parental behaviour (see Section 1.4.1). It should be noted that the
inter-spawning interval for the natural incubation method was inconsistent (as evidenced by
the large standard deviation) and ranged from 11 to 53 days. This suggests that spawning
inhibition due to the presence of eggs and/or fry may be complicated by other factors. It is
59
beyond the scope of this study to investigate this further, however, more investigation into
the reproductive physiology of P. seafare is needed to develop a better understanding of the
role of the presence of eggs and fry in influencing reproductive activity.
Egg production. Asynchronous ovaries are typical in tropical and sub-tropical species of
fish that display spawning behaviour continuously or for extended periods throughout the
year (Lam 1983) and generally have a range of oocytes at various stages of maturity allowing
ovulation over a long period (Rana, 1988; and Redding and Patino, 1993). Consequently the
inter-spawning interval may play a role in the number of oocytes maturing for the next
spawning. This would suggest that a decrease in the inter-spawning interval, as for artificial
incubation, would lead to a decrease in the absolute fecundity, as confirmed by experimental
data. Absolute fecundity (number of eggs per spawn) using natural incubation was found to
be significantly higher with a mean of 235 ± 52 eggs per spawn for natural incubation, than
for artificial incubation with a mean of 163 ± 41 eggs per spawn (P < 0.05) (see Table 7).
However, when cumulative fecundity (total number of eggs produced during the experiment)
was considered, it was found that artificial incubation gave a significantly higher (P < 0.05)
cumulative fecundity of 651 ± 255 eggs than natural incubation with a cumulative fecundity
of 3 70 ± 163 eggs. This indicates that although using natural incubation leads to higher egg
production per spawning, the total number of eggs produced over a long period (in this case
55 days) is much higher when artificial incubation is used. This higher cumulative fecundity
for artificial incubation is largely the result of the increased number of spawnings during the
experimental period (approximately twice as many as natural incubation). Therefore it
would seem that greater productivity could be achieved by utilising artificial incubation of P.
seafare eggs and fry.
It is generally accepted that the number of eggs produced by a female fish will increase with
age and size (Rana, 1988). However, the relative fecundity data (see Figure 12) for P.
seafare does not exhibit this linear relationship and in fact, suggest a trend of a decreasing
relative fecundity with increasing bodyweight of females. These data are highly variable,
along with absolute and cumulative fecundity (see Figures 10 and 11 respectfully). This
variability in fecundity data is likely to be the cause of this apparent discrepancy with the
findings of the current study to the accepted relationship between relative fecundity and
60
female weight. The reasons for this variability are unclear and could be due to management
practices or to inherent biological vatiability.
Further experimentation into the endocrinological control of oocyte maturation and ovulation
in asynchronous spawners, and in particular P. seafare is needed to determine the exact
mechanisms at work here.
Hatch rate, larval survival and length. A hatch rate was achieved in both treatments of 89 ±
3.54 and 90.67 ± 3.25 per cent respectively with no significant difference between
treatments. These results differ from the findings of Brown and Gratzek (1982) who report
increases in the hatch rate of eggs when incubated artificially. However these authors do not
provide any information on their methodology preventing direct comparisons being made
between their study and the results presented here. It should be noted that during the course
of the experiment, eggs naturally incubated were eaten by the parents on three occasions. P.
seafare pairs frequently eat their eggs, when allowed to naturally incubate them, in response
to a perceived threat (Bergman, 1967; Axelrod and Burgess, 1979; and Brown and Gratzek,
1982). The differences between the cun-ent findings and that of Brown and Gratzek (1982)
may be due to a higher incidence of egg eating in former work.
The size of the larvae upon hatching showed little variation between treatments and at-test
indicated no significant difference at P > 0.05 between eggs incubated naturally or
artificially. The incubation method also played no role in the survival of the larvae to first
swim up with at-test showing no significant difference (P > 0.05) between the two
treatments used (see Table 9). The performance of larvae was not significantly affected by
incubation choice, with no significant difference between the treatments for larval size or
survival to first swim-up.
The results suggest that egg removal and artificial incubation (which were shown to have no
adverse effect on egg or larval survival and growth) would be used to maximise production
of fry in commercial production. The use of this method has been shown to increase fry
production significantly over a period of time, which will reduce the number of broodstock
pairs needed and reduce operating costs associated with hatchery production. However, as
61
Brown and Gratzek (1982) highlight, periodic resting of breeding pairs is necessary to
prevent decreases in fecundity from a prolonged period of continual spawning.
3.3 Nursery culture of P. scalare under commercial hatchery conditions
3.3.1 Introduction
The reliable supply of fry for intensive farming operations is essential for success of such
ventures, and is cited as a major constraint in the production of several species (Hay lor,
1993). Shang (1981), indicates that the intensification of fry production by moving to
intensive hatchery techniques, rather than extensive pond systems, can lead to a reduction in
both the production costs and cost variability. These reductions are primarily due to
increases in the quality (ie. consistency and reliability) of production, which is essential for
large scale commercial production (Jones and Houde, 1986).
Several authors have proposed fry production techniques for P. seafare (Hoedeman, 1975;
Mcinerny and Gerrard, 1989; and Chye, 1991). A literature search has revealed no previous
attempt to quantify the survival, growth and development of P. seafare during the nursery
culture phase. These data are essential for further development of the sub-model.
This experiment was carried out to quantify the performance of P. seafare fry during the
nursery phase of production under commercial culture conditions.
3. 3. 2 Materials and methods
Replicates consisted of eggs from three pairs of broodstock , selected randomly from the
hatchery. The eggs were incubated artificially (see Section 3.2.3.) and the resultant fry
stocked in nursery tanks (see section 2.4.3) on Day 7 (post hatching) at a density of 100 fish
per tank (ie 100 fish per 40 L). Temperature and pH were recorded daily, with ammonia,
nitrite and water hardness measured every 7 days (see Section 2.2). Thirty per cent of the
water was changed every 7 days.
62
Samples often fry from each tank were taken daily from Days 0 to 9, and then on Days 12,
14, 16, 18, 20, 24, 28, 32 and 36. The fry were anaesthetised (see section 2.5) and the
standard length measured (see SEction 2.6) and recorded for each individual in the sample.
Upon recovery the fry were returned to their tank. The mean length was determined for
each sample (see Section 2.10.1).
Mortalities were removed from their respective tanks and recorded. Mortalities were not
replaced during the experiment.
The feeding regime used in this experiment was similar to that proposed by Mcinerny and
Gerrard (1989). From Day 0 to 6 the larvae fed endogenously on their yolk-sac reserves
after which they commenced free swimming and feeding exogenously. First swim-up fry
were fed freshly hatched Artemia sp, after 50 per cent of the fry had begun free-swimming
on Day 6. Freshly hatched Artemia sp. nauplii (Instar I) were hatched from Salt Lake City
Artemia cysts. The cysts were decapsulated using standard techniques described by Me Vey
(1983). The decapsulated cysts were hatched in a 5L glass container with aerated seawater.
The nauplii were harvested after 24 hours and fed ad libitum 3 times daily until the larvae
were 20 days old. Weaning onto artificial food, in the form of powdered salmon starter
pellets (see section 2.9), was commenced on Day 14, with this being the only food source
provided from Day 21.
Data analyses. The per cent survival rate was calculated from the mortality data for each
tank. The mean length and standard deviation were determined for each sample (see Section
2.10.1) and compared using a Students t-test (see Section 2.10.2). The mean length data
were then used to calculate the specific growth rate of the fry during the experimental period.
3.3.3 Results
Figure 13 shows the numbers of mortalities per day during the experiment period and
reveals two peaks in mortalities. The first was between Days 1 and 2 after hatching, the
second peak between Days 18 and 20. This pattern of mortality resulted in a mean survival
of93.67 ± 0.58 per cent.
63
4
Tank I 3
:~ ~ 0 s .... 2 0
~
1 z
oJ-~~------------_J~~L-------
4
3
:~ Tank II
g 0 s 2 .... 0 1-<
"' .0
§ z
r.'"
0~~--------------~~~L------
4
3 ~
"' :-e Tank III s 1-< 0 E '- 2 0
b .0
§ z
I 2 3 4 5 6 7 8 9 12141618 20 24 28 32 34
Time(Days)
Figure 13. Daily incidence of mortalities of P. sea/are juveniles during nursery culture phase
64
The fry grew from a mean length of2.85 mm to more than 25 mm over the 36 days ofthe
experiment at a specific growth rate of 6.42 % day-1• Figure 14 shows the change in mean
standard-lengths of the fry during the 36 day experimental petiod.
Table 10 lists the initial and final lengths oflarvae and fry, as well as the survival and
specific growth rates for each of the replicate tanks.
Table 10. Initial length, final length and survival of P. scalare fry during
nursery culture phase (n = 300)
Tank I Tank II Tank III
Initial Length (mm) 2.85 ± 0.03a 2.84 ± 0.04b 2.85 ± o.o2c
Final Length (mm) 25.08 ± 1.1Y 25.29 ± 0.07b 24.62 ± 1.15c
Survival rate(%) 94 94 93
Note: Data in the same row sharing the same superscript are significantly different (P < 0.05).
The water quality of the tanks during the experiment are summarised in Table 11.
Table 11. Summary of water quality parameters for nursery culture
phase
Water Quality Tank I Tank II Tank III
Parameter
Temperature 25.9 ± 0.44 26.11 ± 0.5 25.97 ± 0.51
CC)
pH 6.93 ± 0.02 6.96 ± 0.02 6.97 ± 0.02
Ammonia (ppm) 0.01 ± 0.01 0.01 ± 0.01 0.01 ± 0.01
Nitrite (ppm) 0.01 ± 0.01 0.01 ± 0.01 0 ± 0.01
Water Hardness 78 ± 11.64 78.67 ± 11.06 77.5 ± 9.35
(ppm CaC03)
65
0\ 0\
e s co ]
'" 3 " "' " :2:
30
25
20
15
10
5
0 0 10 20 30
Time (Days)
Tank. I
] ?
I 20 e g
-5 -5 O!l 00
" " ~ 15 ~ -,; g 0 0 ,.... ,....
" 10 " "' "' " " :2: :2:
5
0 I
40 0 10 20 30 40
Time (Days)
Tank II
Figure 14. Increase in mean standard-length of P. scalare juveniles during nursery culture phase
30
25
20
15
10
5
0 0 10 20 30 40
Time (Days)
Tank III
3.3. 4 Discussion
The water quality in the tanks are within the recommended range for P. sea/are (Hoedeman,
1979; and Chye, 1991) while the levels of ammonia and nitrite were within the range
recommended by Langdon (1988) for hatchery production oflarval fish (see Table 4).
Survival of P. sea/are fry was 93.67 ± 0.58 per cent for the three tanks during this
experiment and similar to survival rates found in other warmwater species of fish such as
Oreoehromis nilotieus (Dambo and Rana, 1992) and Clarias lazera (Hogendoorn, 1980; and
Haylor, 1993), reared under similar conditions. This high survival rate may in part be due
to P. seafare being non-cannibalistic. There was no aggressive or cannibalistic behaviour
observed during the experiment and there have been no reported cases of cannibalism or
aggressive interaction causing mortalities for P. seafare. Aggressive or cannibalistic
behaviour can cause severe mortality rates in other species cultured intensively, such as 40
per cent for Koi carp (VanDamme, et.al, 1989), 16 per cent for larval walleye (Stizostedion
vitreum) (Krise and Meade, 1986) and 10per cent in Clarias sp. Haylor, (1991).
The pattern of mortality was consistent between the replicate tanks and appeared to be
spatially dependent, with two peaks in mortalities observed during the experimental period.
The first peak occurs between Days 1 and 2 after hatching (see Figure 13). These
mortalities were most likely the result of insufficient yolk reserves or deformities in the
larvae (Blaxter, 1979). The second peak in mortalities occurred between Days 16 and 20.
This peak coincided with a period of metamorphosis and the weaning phase. During
metamorphosis, the fry undergo lateral-compression and take on their adult form. Signs of
lateral compression were first observed on Day 15 with all the fish having undergone lateral
compression by Day 19. Blaxter ( 1979) reports that mortalities often occur in larvae and fry
in conjunction with development of organs or major physiological changes. The weaning
phase commenced on Day 15 and involved the gradual replacement of Artemia nauplii with
an artificial diet. The weaning phase is critical and can result in high mortalities in many
species (Shepherd and Bromage, 1988; Jones and Houde, 1986). Mortalities during weaning
are generally due to one of two reasons; an increase in the rate of cannibalism or starvation
due to the inability to recognise and accept new food particles. It was likely a combination
of metamorphosis and weaning were the cause of the mortalities observed at this stage,
although the exact mechanism remains unclear and warrants further investigation.
67
The fry grew at a specific growth rate of 6.42% day-1 over the 36 days of the experiment,
with no significant difference in growth between the 3 replicate tanks (P > 0.05). This is
illustrated by Figure 14 which depicts the change in mean standard-length of fry in the three
replicate tanks and highlights the characteristic rapid growth that juvenile fish experience
(Brett, 1979).
The nutritional regime provided during the experiment appears adequate for P. seafare, as
evidenced by the growth and survival rates. However, the perfonnance of the larvae and fry
may be further improved through refinements of the nutritional regime. Nutrition, in terms
of both quality and quantity have been shown to play an important role in the growth and
survival of larvae and fry, with performance increasing with quality and quantity of food
provided (Jones and Houde, 1986). Incorporation of additional zooplankton species and or
the use of nutritionally enhanced Artemia may improve growth and survival of P. seafare.
Feeding of Artemia for a longer period (ie prolonging the weaning phase) may also improve
the performance of P. seafare. Degani (1993) indicates that as well as requiring high levels
of protein, the addition of a small quantity of live food significantly increases the growth of
P. seafare. It was proposed that live food sources such as Artemia sp. may contain a
micro-element absent in artificial diets (Degani, 1993). The issue of nutrition, particularly
the use of live food, may therefore need further investigation in order to achieve better
growth and survival performance from P. seafare during the nursery phase.
An in-depth critique of the development of P. seafare fry is beyond the scope of this study,
however a developmental aspect of note is that of swim-bladder inflation. Generally the
successful inflation of the swim-bladder is essential for successful commencement of feeding
for first feeding fry (Rana, 1988; Stickney, 1994). During the experiment first swim-up fry
were evident on the morning of Day 6 and all fry were free swimming within 12 hours
(temperature approximately 26 oc). Initial swim-bladder inflation can generally be achieved
through either gulping atmospheric oxygen, usually upon first swim-up or through absorption
of oxygen from the water during larval development (Lagler, et al, 1977; and Blaxter 1979).
In the case of P. seafare swim-up fry did not appear to gulp atmospheric gas during initial
swim bladder inflation during the experiment and generally remained in the lower half of the
water column. Similar observations have been found in other cichlids. Doroshev and
Cornacchia, (1979) found that Tilapia mossambiea did not gulp atmospheric air to inflate
68
their swim bladder and suggested that inflation was achieved through the transport of
dissolved oxygen from the water via the respiratory and circulatory systems to the primordial
swim bladder. This mode of int1ation has been observed in other cichlid species (Doroshev
and Cornacchia, 1979) and is thought to be the mode through which P. seafare achieves
swim-bladder inflation. However, histological and microscopic analyses of the development
of P. seafare are needed to confirm this.
In summary the growth and survival rates of P. seafare in this experiment suggest that the
methods used here are suitable for rearing of P. seafare and indicates the amenability of P.
seafare to intensive culture practices. However, further investigation into the nutritional
regime and developmental processes during the nursery phase may be useful in improving
the growth and survival rates of P. seafare.
3.4 Effect of feeding rate on the growth of P. seafare
3. 4.1 Introduction
Nutrition, both in terms of quantity and quality, is a vitally impmiant factor in the growth of
any organism and to the success of a culture system (Allen et al., 1984; and Pillay 1990). An
artificial diet must satisfy all the nutritional requirements of the cultured species, and is
essential as nutritionally deficient or incorrectly balanced diets can adversely affect growth of
the fish and even lead to disease problems (Allen et al., 1984; and Shepherd and Bromage,
1988).
The cost of artificial diets can be one of the largest inputs for intensive farming operations
(Allen et al., 1984; and Pillay, 1990) and the optimisation or lowering of the cost of feed
inputs can drastically affect the profitability of intensive farming of fish (Treadwell et al.,
1992). Improved feed utilisation may mean significant cost savings for the farmer and may
also see improvements in water quality due to reduced wastage of feed (Al-Ahmad et al.,
1988; and Cacho et al., 1990). As such the dietary requirements for important food species
such as salmonids has received considerable attention.
69
However, the nutritional requirements of P. seafare and ornamental fish in general
(Pannevis, 1993), have received little attention to date. Furthermore, information regarding
optimal feeding regimes for P. seafare is also limited. Feeding rate is of particular
importance when developing a farm plan as it will affect the feed costs and determine the
level of effluent generated by the fish. These parameters are important for determining
operating and capital costs requirements of the enterprise.
3.4.2 Materials and methods
Four different feeding rates were tested in the experiment, viz: 2, 6, 10, and 16 per cent of
tank biomass per day(% day"1). Each treatment was assigned three replicate tanks, with
each experimental tank randomly assigned to a treatment. Each experimental tank was
stocked with five juvenile P. seafare with a mean weight of 0.55 ± 0.03g and a mean
standard-length of 25 ± 0.21 mm (n = 60). All the fish were the progeny of a single
spawmng.
The fish were held in the experimental grow-out system discussed in Section 2.4.4. The
experimental tanks were siphoned to remove any uneaten food and faeces, with a 10 per cent
water change performed daily. Water quality (pH, temperature and ammonia) were
measured and recorded prior to siphoning the tanks, with weekly measurements of nitrite and
nitrate also taken (see Section 2.2). Dissolved oxygen level was maintained at 7 ± 1 ppm.
The experimental fish were weighed (see Section 2. 7) on the morning of Day 1 of the
experiment, and thereafter every seven days until the end of the experiment.
Feeding Regime. A pelleted salmonid diet (0.6- 1.4 mm pellet size) was used. The amount
of food provided to each tank was calculated by multiplying the tank biomass by the feeding
rate. The food was weighed and recorded daily to the nearest 0.01g, and fed in three equal
portions at 0900, 1300 and 1700h respectively. Rations were adjusted weekly according to
new tank biomass. The food conversion ratio (FCR) was calculated from these data (see
Section 2.8).
Data analyses. The mean weight for each treatment was calculated weekly (see Section
2.10.1). These data were plotted on a graph of mean weight versus time. The mean and
70
standard deviation of survival were determined for each treatment (see Section 2.1 0.1 ).
The effect of feeding rate on the percentage survival rate of P. seafare was statistically
analysed using an ANOVA (see Section 2.10.3). The FCR and conversion efficiency for
each replicate tank, and the mean and standard deviation were then calculated for each
treatment. ANOV A was used to analyse the effect of feeding rate on the FCR and
conversion efficiency (see Section 2.10.3). A graph ofFCR versus feeding rate was used to
illustrate the effect of feeding rate on FCR, with a linear regression performed to quantify
this relationship (see Section 2.10.4). The biomass for each tank was used to calculate the
specific growth rate (SGR) (see Section 2.8), and an AN OVA test used to assess the effect of
feeding rate on the SGR of P. seafare (see Section 2.10.3).
A growth-ration graph was developed using the experimental data, with the growth-ration
curve fitted by eye, there being too few points to solve the general equation (Brett, 1979).
3.4.3 Results
During the experimental period one mortality was recorded in a replicate tank fed a ration of
10 % day-1 and one mortality was recorded in a replicate tank fed at 12 % day-1• The growth
of the P. seafare juveniles is illustrated in Figure 15, which depicts the change in the mean
weights of fish during the experiment. The results for initial weights, final weights, SGR,
FCR, and conversion efficiency are summarised in Table 12.
Table 12. Growth and feeding efficiency of P. sea/are at different feeding rate (n = 60)
Feeding rate(% day-1) 2% day-1 6% day-1 10% day-1 16% day-1
Initial weight (g) 0.54 ± 0.08" 0.54 ± 0.09" 0.57±0.11" 0.55 ± O.P
Final weight (g) 0.78 ± 0.2· 1.34 ± 0.32b 1.63 ± 0.39bc 1.7 ± 0.32°
SGR (% day-1) 1.75 ± 0.24" 4.34 ± 0.28b 5.14 ± 0.98bc 5.52 ± 0.59c
FCR 0.73 ± 0.09" 1.11 ± 0.04b 1.57 ± 0.27c 2.09 ± 0.16d
Gross Efficiency 82.5 ± 12.77" 68.17 ± 8.74ab 56.4° ± 16.97b 35.81± 4.24°
Note: Data in the same row with different superscripts are significantly different (P < 0.05).
71
2.5 2.5
2 2
3 1.5 3 1.5 ~ .1'1 'il bl)
'il ~ " ;J " " T il :::;:
T :::;: T 1 .l. l
0.5 0.5
0 0 0 5 10 15 20 25 0 5 10 15 20 25
2%day-1 6% day -1
Time (Days) Time (Days)
2.5 2.5
2 2
3 1.5 3 1.5
~ .1'1 bl)
'OJ . ., " " ~ ;J
:::;: ~
0.5 0.5
0 0
0 5 10 15 20 25 0 5 10 15 20 25
Time (Days) Timw (Days)
lOo/oday-1 16%day-1
Figure 15. Change in mean weight of P.scalare juveniles using different feeding rates
72
The specific growth rate of P. seafare ranged from 1. 75 ± 0.24 % day-1 at the a feeding rate
of2% day-1 to 5.52 ± 0.59% dai1 at a feeding rate of 16% day-1. The change in specific
growth rate with increasing feeding rate for P. seafare juveniles is shown in Figure 16. The
FCR was also found to be influenced by feeding rate and ranged from 0.73 ± 0.09 at 2%
day-1 to 2.09 ± 0.16 at the 16% day-1• A linear regression, shown in Figure 17, revealed a
linear relationship between FCR and feeding rate to be:
FCR 0.098(Feeding Rate)+ 0.54, r2 = 0.997, n = 60. .. .. 5
The gross efficiency was also found to be affected by the feeding rate, with an increase in
the feeding rate resulting in a decrease in the gross efficiency. A linear regression
determined the following relationship between conversion efficiency and feeding rate (see
Figure 18):
Conversion efficiency -3.304(Feeding Rate)+ 88.802, r2 = 0.999, n = 60 .... 6
Water Quality. The water quality proved to be consistent throughout the experiment. Table
13 lists mean parameters and standard enors.
Table 13. Summary of water quality parameters during feeding rate experiment
Parameter RANGE Mean
Temperature ( oc) 25- 26.5 25.8 ± 0.65
pH 6.89- 7.2 6.97 ± 0.5
Ammonia (ppm) 0-0.3 0.01 ± 0.01
Nitrate (ppm) 0-47 16 ± 16.7
Nitrite (ppm) 0-0.02 0.01 ± .01
Water Hardness (CaCo3) 20- 80 68 ± 27
(ppm)
The water quality experienced during the experiment was found to be within the ranges
recommended for growth of P. seafare. However, ammonia, did exceed recommended
73
--..) .j::;.
~ -' >.
"' "0
<f 0)
""' 0::: ..c ~ 0 h
0 (.)
lC ·c:;
C) p..
U)
8
6
I .,-
4
2
04-------~------r-----~~----~
0 5 10 15 20
Feeding rate (% bodyweight day -1)
Figure 16. Effect of feeding rate on the specific growth rate of juvenile P. seafare
--...}
V1
.s 'c;J ~ c 0 ·c:; .... <!) ;> c: 0 u "d 0 0
u..
2.5
I T
I fi 2
1.5
I -r y = 0.098x + 0.540 r2 = 0.997 -'-
0.5
0,_------~------.-------r------,
0 5 10 15 20
Feeding rate (% bodyweight day -1)
Figure 17. Linear regression of food conversion ratio and feeding rate for P. seafare juveniles
--...)
~
~ t:: <1l
"<::)
100
80
y = -3.304x + 88.802 y2 = 0.999
8 60 <1l
"' "' 0
0
40
l.
204-------~------,-------~----~
0 5 10 15 20
Feeding rate (% bodyweight day -1)
Figure 18. Linear regression of gross efficiciency and feeding rate of P. seafare juveniles
levels on occasions towards the end of the experiment, indicating that the nitrifying capacity
of the biological filter may have been insufficient for the biomass.
3. 4. 4 Discussion
Survival of P. seafare during the experiment was high, with only two mortalities recorded.
The results of this experiment suggest that at the levels tested feeding rate has little effect on
the survival on P. seafare. However, a multi-factorial experiment would be necessary to
determine the effect of feeding rate on the survival of P. scalare.
The effect of feeding rate on growth of P. seafare is shown in Figure 15 which illustrates the
change in mean weight of juveniles during the experiment. This graph clearly indicates the
much lower growth of juveniles fed at a rate of 2 % day-1 than the other three treatments.
Growth was strongly influenced by feeding rate with the specific growth rate ranging from
1.75 ± 0.24% day- 1 at a feeding rate of 2% day-1 to 5.52 ± 0.59% day-I, at a feeding rate of
16 % day-1• Statistical analysis showed that the specific growth rate at a feeding rate of 2 %
day-1 was significantly lower than the other three treatments (P < 0.05); with the specific
growth rate at a feeding rate of 6 % day-1 significantly lower than the specific growth rate at
a feeding rate of 16 % day-1• There was no significant difference in specific growth rate
between a feeding rate of 10 and 16 % day-1 or between a feeding rate of the 6 and 10 %
day-1 (P > 0.05).
The growth rates attained by P. seafare under these experimental conditions compare well to
growth rates of other similar sized warmwater species. Common carp ( Cyprinus carpio)
under intensive conditions were found to have a specific growth rate of 0.65 % day-1 at a
feeding rate of 1.75% day- 1, which increased to 3.1% day-1 at a feeding rate of9% day-1
(Goolish and Adelman, 1984). Hogendoom (1980) reported growth rates of 5.5% day-1 at a
feeding rate of 10% day-1 for Cfarias lazera fingerlings in the size range of0.05- 1.5g.
Reports for Tilapia sp indicate growth rates for similar sized fish are between 2- 5 % day-1
under intensive tank culture (Balatin and Haller, 1982).
In general, the growth rate of fish increases as the feeding rate increases until a maximum
feeding rate is reached after which no further increases in growth can be attained with further
77
feeding rate increases (Brett, 1979; and Gunther and Boza Abarca, 1992). This relationship
can be shown as a growth-ration curve with the general form of:
Growth= a/SIN(b*Ration +c), where a, b, and care constants, (Brett, 1979).
The feeding rate was found to have a similar effect on P. seafare, with growth increasing
with increasing feeding rate to a point where no further significant increases (P < 0.05) in
growth were attained for increases in feeding rate. A growth-ration graph was developed
using these data, with the growth-ration curve fitted by eye (Figure 16), there being too few
points to solve the general equation (Brett, 1979). Extrapolation of the results from this
experiment can be used to further approximate the optimum level. These extrapolated data
indicate that increases in feeding rate past 8% day·1 result in relatively small increases in
growth, but large increases in FCR. As food was wasted at higher rations near I 0 % day·1 it
would suggest that a feeding rate of 8 % day·1 may be optimal in terms of growth, FCR and
hygiene. However, it is recommended that more feeding trials using a wider range of
feeding rate levels be used to verify these findings.
The food conversion ratio was also found to be affected by feeding rate, with all treatments
significantly different (P < 0.05). These statistical differences are highlighted by a linear
regression of feeding rate and FCR (Figure 17), which revealed a strong linear relationship
between food conversion ratio and feeding rate. This regression indicates that FCR
increases linearly with increasing feeding rate over the feeding rates tested and agrees with
findings of other authors. Al-Ahmad et al. (1988) found that FCR increased with increasing
feeding rate for Oreoehromis spilurus. Anderson and Fast (1991) found that the FCR for
Clarias fueus reared at different temperatures increased with feed rate. Another American
cichlid, Colossoma macropomum, is also an efficient converter at low feeding rates and the
FCR increased as feeding rate increased (Gunther and Boza Abarca, 1992).
P. seafare exhibited low FCR, particularly at low rations indicating that it is an efficient
converter. The lowest FCR (see Table 12) was recorded at a feeding rate of 2 % day·1 (P <
0.05) indicating P. seafare is an efficient food converter at low rations. The significantly
higher FCR for the 16 % day"1 treatment may be due in part to some of the food remaining
uneaten in the tanks. The level of uneaten food was not recorded, however it is estimated
78
that up to 25 per cent of the food fed remained uneaten, particularly in the last two weeks of
the expetiment. This uneaten food resulted in large amounts of fungi in the tanks with
resultant poor hygiene relative to other tanks in the 16 and 10 % day-1 treatment tanks.
However the 10% day"1 treatment tanks were not affected to the same extent. Similar
findings were attained with Oreochromis mossambicus fry at high rations (12 and 24 per
cent per day), with uneaten food resulting in high FCR values of 1.8 to 2.2 and poor water
quality (Beamish and Thomas, 1984).
The results for gross conversion efficiency also indicate that P. sea/are is an efficient
convertor at low feeding rates (see Figure 18), with the gross conversion efficiency of the 2
% day-1 treatment being found to be significantly higher (P < 0.05) than the 10 and 16%
day"1 treatments, with the 6% day- 1 treatment being significantly higher than the 16% day- 1
treatment. However, the linear relationship (see equation 6) does not comply with the
general form. Brett (1979) states that a graph of gross conversion efficiency and feeding rate
is the shape of a tapered, dome-shaped curve and is not linear as depicted here by Figure 20.
However, due to the high r value the linear relationship of the present study is hard to
dismiss. It is difficult to determine the cause of this discrepancy in the shape of the graph
without further experimentation, however it may be due to either a lack of data points (ie. a
wider range of feeding rates needs to be tested) or due to the higher levels of uneaten food
found in the 10 and 16 % day-1 treatments. This uneaten food was not adjusted for in
calculations and therefore may result in anomalies in the data. Future studies may address
this problem through increasing the number of feeds over which the daily ration is fed.
The importance of FCR in the culture of ornamental fish should be noted here. Ornamental
fish generally have a much higher value to weight than food fish species, and Bassleer (1994)
gives the example of food fish being worth $3.00 per kg compared with ornamental fish
being worth $300.00 per kg. Therefore food costs do not have as large an impact on
ornamental fish culture as for food fish culture. Nevertheless, a reasonable FCR should still
be sought, particularly to minimise the amount of uneaten food so water quality does not
become compromised and to reduce tank cleaning. Cacho et al. (1990) propose that the
optimal feeding rate must be one that minimises the risk of poor water quality or stress and
maximises growth and survival of the cultured species. The results from this experiment
suggest that the optimum feeding rate, in terms of growth, FCR and minimum food wastage
79
lies between 6 and 10 % day-1• This agrees with recommendations from Degani (1993) who
used a feeding rate of 7 % dai1 for P. seafare. However it was not stated on what basis this
feeding rate was used or the FCR achieved. These feeding rates are also similar to those
found for other warmwater species of similar size. Goolish and Adelman ( 1984) determined
that a feeding rate of 9 % day-1 leads to the best food conversion and growth-rates for
common carp. A slightly higher value of 10 % dai1 was found to give the best result for
Clarias lazera (Hogendoorn, 1980).
The issue of diet quality should also be noted here. Diet quality, and in particular protein
levels can significantly affect growth rates and conversion rates (Brett, 1979; and Cacho et
al., 1990). Degani (1993), states that P. seafare needs a high level of protein (40- 50 per
cent) which is similar to recommendations for other cichlids (Balarin and Haller, 1982).
Degani ( 1993) also found that the addition of a small quantity of livefood significantly raises
growth, which is attributed to Artemia possibly containing a micro-element absent in
artificial diets. Although it is beyond the scope of this paper to determine the optimum diet
as far as quality is concerned, the importance of diet quality and its possible effect on the
optimum feeding rate determined from this experiment cannot be overlooked. It is therefore
recommended that this area be further investigated in an attempt to further refine the model
and promote better growth rates.
3.5 The effect of stocking density on growth and fin factor P. scalare juveniles
3.5.1 Introduction
Management practices have a great impact on the profitability of fish farming. One such
example is the stocking density used for culturing fish. The stocking density at which fish
are grown is critical in determining the production capacity of a culture system. Density is
an even more critical issue when considering intensive culture systems that generally have a
much higher capital cost than less intensive systems. Such systems must employ relatively
higher stocking densities in order to maximise the production of fish with minimal water
80
usage (Suresh and Lin, 1992). By using high stocking densities the production costs per fish
are reduced, assuming satisfactory growth and survival are maintained (Wallace et al., 1988).
The most appropriate density will depend on a range of biological and economic factors
(Baylor, 1991). In intensive systems the stocking density is often determined by the
canying capacity of the system, which is determined by the levels of oxygen that can be
maintained and the rate at which toxic metabolites can be removed. Thus a tank could only
hold that amount of fish that does not reduce the oxygen level during peak demand (ie.
during and shortly after feeding) to levels that may compromise the health of the fish
(Wheaton, 1977). Similarly, the system must be able to maintain the level of toxic
metabolites below levels that may cause any depression in growth or mortalities. Other
factors that may influence the optimal stocking density are age and/or size within species and
exogenous factors such as temperature and feeding rate (Baylor, 1991).
The stocking density also may affect the social interaction between fish and lead to
competitive behaviour for food, space or tenitory and may result in aggressive behaviour
(Brett, 1979). This behaviour may change production parameters such as growth, food
conversion ratio and survival (Brett, 1979; Wallace et.al, 1988; and Suresh and Lin, 1992).
These changes generally include decreases in growth rates, survival and food conversion
ratios with increases in stocking density. However, it should be noted that the interaction
between stocking density and growth performance is complex. Fish on unrestricted rations
may feed poorly at low densities, giving reduced growth and FCR. Some species require
social stimulation through increased numbers to enhance feeding behaviour (Brett, 1979).
Stocking density also plays an important role in the quality of ornamental fish. The product
definition for ornamental fish dictates that they must be free of lesions and injuries, as well as
having properly formed fins. Fish not conforming to these criteria may be unsaleable. As
the stocking density increases the occunence of injuries and damage to fish generally
increases, particularly for aggressive or tenitorial species and species with enlarged fins
(Brown and Gratzek, 1982). Therefore the stocking density used for ornamental fish will
need to be one that offers:
1. high growth rates;
81
2. high survival;
3. low FCR; and
4. a low rate of injuries or damage.
Several authors have recommended appropriate stocking densities for P. seafare (Low and
Wong, 1984 and Degani, 1993). However, as these recommendations have been made for
pond culture, they may not be appropriate for more intensive systems. These studies have
not addressed the effects of stocking density on fin damage (as measured by fin factor).
The aim of this experiment was to determine the effect of different stocking densities on the
growth, survival and fin quality of P. seafare in an experimental recirculating system.
3.5.2 Materials and methods
The experimental animals used were P. seafare fry with a mean weight of 0.47 ± 0.05 g
and mean standard length of 23 ± 0.5 mm (n = 102). These fry were the progeny of one
spawning previously reared using the methods described in 3.1 and 3.2. The fry were
randomly assigned to their experimental tank. The following treatments were used, each
with three replicates, giving a total of 12 experimental tanks:
Treatment I - 3 fish per tank;
Treatment II - 7 fish per tank;
Treatment III - 10 fish per tank; and
Treatment IV - 14 fish per tank.
The fish were stocked in 10 L aquaria containing 7 L of water serviced by a common
biofilter (see section 2.4.4). These densities resulted in the arbitary stocking densities of 0.5
fish litre-I, 1 fish litre-1, 1.5 fish litre-\ and 2 fish litre-1
. The experimental tanks were
siphoned to remove any uneaten food and faeces, with a 10 per cent water change performed
daily. Water quality (pH, temperature and ammonia} were measured and recorded prior to
siphoning the tanks. The dissolved oxygen level was maintained at 7 ± 1 ppm with weekly
measurements of nitrite and nitrate also undertaken.
82
The experimental fish were weighed on the morning of Day 1 (see Section 2.7) and
thereafter every seven days until the end of the experiment. From these data the mean
weights were determined and the specific growth rates and FCR calculated using tank
biomass.
The fry were fed at 8% day-\ based on anecdotal data from Section 3.4. A pelleted
salmonid diet (0.6- 1.4 mm pellet size) was used (see Section 2.9). The amount of food to
be provided to each tank was calculated by multiplying the tank biomass by the feeding rate.
The food was weighed and recorded daily to the nearest 0.01g, and fed in three equal
portions at 0900, 1300 and 1700h respectively. The amount of feed provided to each tank
was adjusted every seven days, based on the tank biomass.
The degree of fin erosion was determined using a method similar to that of Kindshci ( 1987),
however standard length was used instead of total length due to the variation in caudal fin
lengths between individual fish. The fin factor was determined at the last weighing of the
fish. After the fish had been weighed, the standard-length was measured (see Section 2.6).
After the standard-length had been determined the dorsal fin length was measured to the
nearest 1 mm (see Section 2.6).
The degree of fin erosion was then calculated using the following formula;
Fin Factor(%)= Dorsal Fin Length x 100 (adapted from Kindshci, 1987)
Standard Length.
The mean weight and standard deviation for each treatment were calculated weekly (see
Section 2.1 0.1 ). These data were plotted using Cricket Graph III and a linear regression
performed (see Section 2.10.4).
The percentage survival rate was calculated for each replicate and the mean percentage
survival rate determined for each treatment (see Section 2.10.1). The effect of stocking rate
on the percentage survival rate of P. seafare for each treatment was statistically analysed
using ANOVA (see Section 2.10.3).
83
The FCR for each replicate was calculated using tank biomass and total food fed data. The
mean and standard deviation was then calculated for each treatment (see Section 2.1 0.1 ). An
ANOV A was used to statistically analyse the effect of stocking density on FCR for P.
seafare (see Section 2.1 0.3)
The fin factor was calculated for each experimental fish and the mean and standard deviation
determined for each treatment (see Section 2.10.1). The effect of stocking density on the fin
factor of P. seafare was statistically analysed by ANOVA (see Section 2.10.3). A linear
regression was performed to quantify this relationship (see Section 2.10.4).
3. 5. 3 Results
High survival rates were experienced during this experiment. Two mortalities were recorded
during the experiment with one mortality each in Treatment III and Treatment IV
respectively. The growth of P. sea/are juveniles was found to be variable between the
treatments. This is shown in Figure 19, which depicts the change in mean weight of P.
seafare juveniles cultured at different stocking densities. Table 14 sets out the mean specific
growth rates, food conversion ratios and survival rates for the various stocking densities.
Table 14. The specific growth rate and food conversion ratio of P. seafare
juveniles at different stocking densities (n = 102)
3 fish tank1 7 fish tank1 10 fish tank1 14 fish tank1
Specific Growth 3.49 ± 0.01 3 3.33 ± 0.05b 3.43 ± 0.18c 3.64 ± o.os•c
Rate
Food Conversion 1.94 ± 0.05" 2.04 ± 0.06 2.13 ± 0.13ab 1.93 ± 0.1b
Ratio
Survival(%) 100 ± 0 100 ± 0 97 ± 2.8 98 ±4
Note: treatments sharing the same letter in the same row are significantly different at P < 0.05
The relationship between stocking density and SGR is shown in Figure 20. The SGR at a
density of 3 fish tank1 was not significantly different (P>0.05) to the other three treatments,
84
2.5
2
3 1.5 .<= .ell ~
~ ~
0.5
0 0
2.5
2
3 1.5 .<= .ell
" ~ 0::: :l ~
0.5
0 0
3 .<= -~ ~ 0:::
j
10 20 30 40 50
Time (Days)
Four fish per tank
3 :;:; .ell " :< 0::: :l ~
10 20 30 40 50
Time (Days)
10 fish per tank
2.5
2
1.5
0.5
0 0
2.5
2
1.5
0.5
0
0
10 20 30
Time (Days)
Seven fish per tank
10 20 30
Time (Days)
14 fish per tank
Figure 19. Change in mean weight of P. scalare juveniles cultured at different stocking densities (n = 1 02)
40 50
40 50
85
00 0'.
,......_ ";< >, "" "0
.:c 0!)
•o:J ~ »
"0 0
,D
~ <!)
""' ~ ..c ~ 0 )...
0 (.)
<..:: ·o 0 P..
C/)
4
3.75
T $
I .L
3.5 $
$
1 T $ .L
3.25
3
0 0.5 1 1.5 2 2.5
Stocking Density (fish per litre)
Figure 20. Specific growth rate of juvenile P. seafare at Different Stocking Densities.
while the SGR at a density of7 fish tank1 was found to be significantly lower than the SGR
at a density of 14 fish tank1 (P<0.05). The SGR at a density of 10 fish tank1 was also
significantly lower than that at a density of 14 fish tank1. The FCR was also found to be
effected by stocking density. The FCR at a density of 3 fish tank1 was significantly lower
than at 10 fish tank1 (P<0.05), with the FCR at a density of 10 fish tank1 was also
significantly higher than at 14 fish tank1• The relationship between stocking density and
FCR is shown in Figure 21.
The fin factor was also found to vruy with stocking density. The fin factor as well as
standard-lengths and dorsal-fin lengths are listed in Table 15.
Table 15 Dorsal-fin length, standard length and fin factor of
P. scalare juveniles cultured at different stocking densities (n = 102)
Stocking density 3 fish tank1 7 fish tank1 10 fish tank1 14 fish tank1
Mean dorsal fin 32.14 ± 4.74 28.27 ± 4.17 26.9 ± 3.73 27.89 ± 4.25
length (mm)
Mean standard- 36.71 ± 2.87 34 ± 2.37 35.21 ± 3.42 35.54 ± 3.03
length (mm)
Mean Fin Factor 93.9 ± 6.42 84.78 ± 6.57 76.89a ± 8.02 76.28a ± 6.78
(%)
(treatments sharing the same letter are not significantly different at P < 0.05)
A linear regression of stocking density and fin factor (see Figure 22) found a negative linear
relationship defined by the following equations:
Fin Factor= -12.15 (Stocking Density)+ 98.15, r2 = 0.903, n = 102. .. .. 8
However, there was no significant difference (P< 0.05) in fin factor between a density of 10
and 14 fish tank1• The remaining treatment combinations were significantly different
(P<0.05).
87
00 00
-~ d .... c: 0 ·u; .... "" ;> c: 0 ()
"0 0 0
t:I...
2.5
2.25-1
T $
T 1 $
T 2 _L T $ $ .l.. 1
1.75
1.5 -+-----,----..,.----.,,...----,...------,
0 0.5 1.5 2 2.5
Stocking density (number of fish litre -1)
Figure 21. Effect of stocking density on the food conversion ratio of juvenile P. seafare
00 '-0
'""' ~ .... .9 () o:l
'7 .s t:I.
110
100 -l
T e
90_, ~T Y = -12.150x + 98.150 r2 = 0.903
80
70
60~----,-----,-----,-----~----.
0 0.5 1.5 2 2.5
Stocking density (number of fish litre -1)
Figure 22. Linear regression of stocking density and fin-factor for juvenile P. seafare cultured at different stocking densities
The water quality proved to be consistent throughout the experiment. Table 16 lists water
quality parameters recorded during the experiment.
Table 16. Summary of water quality
parameters for stocking density experiment
Parameter Mean
Temperature ec) 25.56 ± 0.5
pH 6.85 ± 0.06
Ammonia (ppm) 0.02 ± 0.01
Nitrite (ppm) 0.01 ± 0
Nitrate (ppm) 6.17 ± 4.84
Water Hardness (ppm) 68.33 ± 5.53
3.5.4 Discussion
Survival. The mortality rate of P. seafare was minimal dming the experiment, with only two
mortalities recorded and mean survival rates ranging from 97 ± 2.8 to 100 per cent. The
survival rates during this experiment were higher than those reported by Degani (1993) who
found that the survival of P. seafare juveniles was 90 per cent at densities of 1 fish per 10 L
to 1 fish per 2.5 L. However, Degani (1993) grew his fish to a much larger size (up to 9g)
and over a period of 60 days, which would be close to sexual maturity.
Several authors (Hoedeman, 1975; Axelrod and Burgess, 1979; and Chye, 1991) report that
P. seafare can become aggressive upon sexual maturity which could lead to higher mortality
rates as the fish become older. This may indicate that over a longer experimental period
similar survival rates may be experienced, particularly if fish are nearing sexual maturity.
However, there have been no repmts in the literature or observations during this study of P.
seafare displaying cannibalistic behaviour.
The growth of P. seafare juveniles was variable over the densities tested and a graph of the
change in mean weight of P. seafare during the experiment does not indicate a clear
relationship between growth and stocking density (see Figure 19). This is further
90
highlighted by a graph of the specific growth rate of P. seafare juveniles at different
stocking densities (Figure 20) which also suggests that the SGR over the densities tested is
variable and no clear relationship can be determined.. The highest specific growth rate
(3.64 ± .05 % day-1) was recorded for at a density of 14 fish tank\ while the lowest specific
growth rate (3.33 ± .05% day-1) was found at a density of7 fish tank1
. Macintosh and De
Silva (1984) found that the growth of juvenile Oreochromis mossambicus, another cichlid
species, at densities of 2 -12 fish litre-1, was also highly variable with no significant effect of
density on the growth rate observed. Other research on the effect of density on growth of P.
seafare indicates that growth at low densities ( eg. 1 fish per 10 li tres) was significantly
higher than growth at a density of 1 fish per 2.5 L (Degani, 1993). Degani (1993) also noted
that there was no difference in the growth of P. seafare juveniles at the densities tested for
the first 20 days of the experiment (ie. at sizes ranging from 1 to 2 g). Although not
conclusive, the results of the present study and that ofDegani (1993) suggest that at stocking
densities less than 2 fish per L, density may not affect growth for fish less than 2g. Density
may only begin to significantly influence the growth rate of P. seafare as they reach a certain
size and/or age. Similar findings have been made for other species and it is thought that
age and size within a species is important in determining the optimal stocking density (Brett,
1979; and Wallace et al., 1988).
Interestingly, the juveniles grown at a density of 14 fish tank1 showed a relatively higher
variation in growth between individual fish compared with the other treatments. The mean
weights in the three replicate tanks for a density of 14 fish tank1 ranged from 1.05 to 3.08g.
This relatively large range may be due to hierarchical or social interactions between fish with
dominant fish being able to out-compete other smaller fish for food enabling them to grow
much larger than their smaller siblings. Similar problems have been encountered with other
species under intensive culture. Dambo and Rana, (1992) indicate that growth differences
within treatments for Oreochromis niloticus are most likely due to difficulty in providing
food uniformly to all fish at high densities, with similar findings in Oncorhynchus myldss
(Holm et. al., 1990) and Channa striatus (Sampath, 1984). Increasing the feeding frequency
( eg. delivering the daily ration over more meals per day) has been found to promote a more
uniform growth (Holm et al., 1990). Although the feeding frequency used here (eg. three
feeds per day) is based on that used and found to be suitable by commercial producers,
increasing the feeding frequency may decrease variability in growth between fish in the same
91
tank. Therefore, feeding frequency should be further investigated to determine its effect on
the growth of P. seafare.
In general, the performance of fish decreases with increases in stocking density. The FCR
has been found to follow this trend and increases with increasing density in red tilapia
(Suresh and Lin, 1992), channel catfish (Allen, 1974), and salmonid species (Refstie, 1977;
Vijayan and Leatherland, 1988). The experimental data did not reveal a clear relationship
between FCR and stocking density. Figure 21 indicates that FCR increases with increasing
density between a density of 3 and 10 fish tank1, however there is a pronounced decrease in
FCR from a density of 10 and 14 fish tank1• The experimental data therefore tend to
suggest that there is no consistent relationship between FCR and stocking density over the
range tested. Other researchers have found similar results with Oreoehromis mossambieus
exhibiting a range of FCR at different densities with no clear relationship (Macintosh and De
Silva, 1984).
Fin erosion is a problem encountered in salmonid culture (Soderberg and Meade, 1987; Mork
et al., 1989; and Kindschi et al., 1991), with other researchers reporting similar problems in
species such as channel catfish (Mazik et al., 1989). Fin erosion is also a significant problem
in the culture of ornamental fish, particularly in species such as P. seafare which have
relatively large fins. For these species the aesthetic appeal of the fish is often related directly
to the length of fins relative to the body. Any degree of fin erosion may detract significantly
from the aesthetic appeal of the fish and result in otherwise healthy fish being unsaleable.
Previous studies on rainbow trout and channel catfish indicate a range of causes of fin
erosion (Laird and Needham, 1988; Kindschi et al., 1991; and Mazik et al., 1989), viz.
1. bacterial infection;
2. mechanical damage through handling of fish (ie. netting, grading etc.);
3. fin nipping between cohorts;
4. abrasive rearing surfaces;
5. poor nutrition (qualitative or quantitative);
6. sunlight;
7. poor water quality; and
92
8. environmental contaminants.
The results from this experiment indicate that the stocking density has a strong influence on
the fin-factor of P. seafare juveniles. Figure 22 shows a linear regression of fin factor and
density for P. seafare and clearly indicates the lineal decrease in fin factor with increasing
density results. The mechanism through which stocking density caused dorsal fin erosion in
P. seafare during this experiment is not clear. Early studies into fin erosion in salmonids cite
stocking density as a causative factor in this syndrome (Soderberg and Meade, 1987).
However, more recent studies have shown that density does not cause fin erosion, rather
density associated factors such as competition and water quality are the cause (Soderberg and
Meade, 1987; and Kindschi, et al., 1991). As aspects such as water quality, nutrition, rearing
surfaces, handling techniques, sunlight and environmental contaminants would have been the
same throughout all replicates it is unlikely that they are the cause of dorsal fin erosion in the
present study. Examination of the dorsal fin margin revealed little damage and there were no
visible lesions present, which would be expected as a result of bacterial or parasitic infection.
However, there were some physical interactions observed between fish in all treatments, such
as:
1. fish pushing each other out of the way (especially when feeding); and
2. chasing over short distances (100 mm).
Bergman (1967) describes the social interaction and aggressive behaviour in P. seafare.
Such physical interactions between fish may be the cause of dorsal fin erosion. As
previously discussed, there appear to be some competitive factors influencing growth of P.
seafare at high densities and this issue warrants further investigation to determine the exact
mechanism through which stocking density affects dorsal fin erosion.
Another point worth noting is that the number of fish having a fin factor that does not meet
the product-definition (see Chapter 4) for P. seafare increases as density increases. Fish with
a fin factor below 73 per cent are sub-standard and do not meet the product definition for this
species. The prevalence of fish with a fin factor less than 73 per cent was found to increase
as the density increased; from 0 per cent for densities of 3 fish tank1 and 7 fish tank1, to 26.9
93
per cent for 10 fish tank1 and 31.5 per cent for 14 fish tank-1• The increased incidence of
stunting of fins at higher densities results in lost productivity through raising fish that are
substandard and unsaleable.
The experimental data here have shown that there is no significant relationship between
stocking density and growth of P. scalare between 3 fish tank1 and 14 fish tank1, for fish
between 0.5- 3g (see Figures, 19 and 20). However, fin factor is found to decrease linearly
with increasing density over the range examined (see Figure 22). The mechanism of this
relationship is unclear, but may be due to competitive hierarchical interactions between
individuals at higher densities.
3.6 Biological submodel
The biological and production data detailed here are based on the procedures and
experimental data detailed in the previous sections of the current chapter and Chapter 2, as
well as general biology data presented in Section 1.4.1. Where data are lacking practical
observations and experiences of commercial producers have been used.
3. 6.1 Production stages
The production of P. scalare was divided into different stages according to life stages and
changes in management practices through the production cycle. The production stages, life
stage and size class data are listed in Table 17.
94
Table 17 Production and life stages of P. scalare
Production Stage Life stage Size
Stage I (Egg- First Feed) eggs not applicable
Stage II (First feed- nursery) larvae- fry (2.85 - 22 mm)
Stage III (grow-out) juveniles 0.5 - 1.4g (22 - 30 mm)
Stage IV (grow-out) juveniles 1.4- 3.4g (30- 40 mm)
Stage V (grow-out) sub-adults 3.4- 29g (40- 80 mm)
Stage VI (Breeding) adult 80mm+
Of primary concern in this study, particularly for growth performance, are Stages I to IV.
Small P. sea/are are classed as stage III and medium sized P. sea/are are classed as Stage IV.
3.6.2 Survival
For the purposes of the farm design, survival is shown as a percentage of individuals
surviving from the original number of eggs laid. This was determined using data from the
experiments in this study and calculating the expected survival (based on the experimental
means) for each production stage and the range of survival possible (based on the
experimental standard deviations). The calculated survival rates and ranges are presented in
Table 18 for each production stage.
Table 18. Calculated survival rate and range of P. scalare for production stages
Stage I Stage II Stage III Stage IV Stage V
Experimental 90.67 ± 3.25 93.67 ± 0.58 98.75 ± 1.5 98.75 ± 1.5 NDA
survival (%)
Number of 91 85 84 83 82
survivors(%)
Range(%) 87.42- 93.92 84.4- 85.46 83.1- 84.93 81.56- 83.87 NDA
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The survival rate of P. seafare, at more than 81 per cent to Stage IV, attests to the
suitability of this species for commercial intensive culture. Good survival rates are important
in commercial production, as it minimises waste of resources and lost production. The
majority of mortalities occur in the early part of production cycle during Stages I and II.
From an economic viewpoint financial losses are minimised with these mortalities in early
stages in production because relatively little time or money has been invested in them.
3. 6.3 Reproduction
Experimental data from this study indicate that the removal and artificial incubation of P.
seafare eggs be used to maximise production of seed in a commercial production facility.
The use of artificial incubation has been shown to significantly increase (P < 0. 05) fry
production over a period of time, which reduces both capital and operating costs associated
with the hatchery.
The expected annual egg production for a pair of fish was derived from mean spawning and
fecundity mean data for P. seafare using artificial rearing of eggs and fry. A spawning
season of 270 days was assumed, allowing three months rest from spawning during the year
to prevent health problems and fecundity decreases associated with continual spawning over
long periods oftime (Brown and Gratzek, 1982). Standard deviation data were used to
calculate the possible range of spawnings and the range of eggs produced for a pair. The
possible range of eggs that could be produced by a pair over a year was then calculated. The
expected annual egg production and range for P. seafare, using artificial egg and larval
rearing techniques is shown in Table 19.
Table 19. Calculated annual egg production of P. seafare
using artificial egg and larval rearing techniques
Number of spawns Number of eggs
per year per year
Calculated mean 23 3,890
Calculated range 15.5 - 42.58 1,599- 10,621
96
Broodstock numbers were then calculated by dividing the number of eggs to be produced per
year by the expected egg production of a pair. Allowance for mortality incurred in each
production stage was also made in calculation of the number of eggs needed to meet
production targets.
The reproductive performance for P. seafare is an area that needs further investigation due to
the considerable variability in fecundity between individuals. Although broodstock
management does not require sophisticated manipulation or induced spawning techniques, a
large number of breeding pairs must be kept to produce sufficient eggs to meet production
demand, due to variability in fecundity between individuals. Research is needed in this area
to increase the fecundity of P. seafare, and to reduce the considerable capital and operating
costs involved in maintaining a large number of broodstock. It is thought that fecundity may
be improved through examining broodstock nutrition, controlling the length of the inter
spawning period and in the longer term, selective breeding may also be useful.
3. 6.4 Growth
The growth of fish in a culture system is the result of a large number of biological and
management interactions (Brett, 1979) and it is beyond the scope of this study to address all
these factors. However, two of the more important management decisions, ie stocking
density, and feeding rate have been addressed in this study (see Sections 3.4 and 3.5). The
mean experimental growth rates (see Sections 3.3, 3.4, and 3.5) were used to determine the
growth rate, duration and stocking density for each production stage (Table 20).
Table 20. Growth and Production data for P. seafare
Stage I II III IV v Stocking Density 1 pair per 5 fish per 3 fish per 2 1 fish per 1 fish per
tank 2L L lL 2L
Specific Growth Not 6.42 3.97 3.07 NDA
Rate (% day-1) applicable
Duration (days) 10 36 21 21 65
97
P. seafare exhibits good growth, resulting in a production cycle of approximately 81 days
for medium sized P. seafare and 60 days for small sized P. seafare. This short production
cycle allows capital infrastmcture to be kept to a minimum and rapid turnover of stock.
Short production mns (ie 21 - 36 days for Stages II- IV) mean rapid turnover of stock,
allowing efficient use of tanks (ie more crops per year). By using sequential rearing
(Paessun and Allison, 1984), small regular numbers offish can be produced throughout the
year. This method has the added advantage of minimising the biomass carried in a
recirculating system by stocking tanks with different sized fish, and reducing the size and
cost of filtration systems. Sequential rearing methods also allow production of P. seafare to
meet product definition criteria, ie small regular shipments (weekly or fortnightly) rather
than larger irregular shipments.
Stocking density plays a significant role in determining the productivity and management of
culture system. Intensive culture systems generally use high stocking densities to maximise
production with minimal water usage (Suresh and Lin, 1992), while more extensive
operations tend to use lower densities to minimise labour and feeding necessary to maintain
low operating costs. In general an increase in stocking density results in decreases in
growth, food conversion ratio and survival (Suresh and Lin, 1992). Although P. seafare is
able to perform well at the higher densities tested (ie. 2 fish per litre), fin damage will occur
at these densities rendering fish unsaleable and/or reducing their quality. Lower densities
(ie. 1 fish per litre) allow better formation of fins and result in higher quality fish. The
stocking densities used in the farm design are based on those used in the experiments and
optimal density determined in stocking density trial for Stages III and IV. Recommended
stocking densities for each production stage are presented in Table 20.
3.6.5 Nutrition
The optimum food type, particle size, feeding rate, and food conversion ratio for each
production stage was determined based on the methods used in the various experiments and
the results. Experimental data from the experiment 3.4 were used to determine the optimal
feeding rate for Stages III and IV. The nutritional regime for Stage II was based on an ad
libitum diet or for feeding as much as fish require. The nutritional regime for Stage V was
98
based on experiences of commercial producers. The recommended nutritional regime is
presented in Table 21.
Table 21. Recommended food type, particles size, feeding rate and expected
FCR for production stages
Stage I II III IV v
Food type N/A Artemia- Salmon Salmon Salmon
weaned onto Starter Starter Starter
powder Pellets Pellets Pellets
Particle size N/A .3- .60 .6- 1.4 .6 - 1.4 1.4- 3.6
(mm)
Feeding Rate N/A ad libitum 8 8 7
(%day-1)
FCR N/A N/A 2.04 ± 0.06 2.04 ± 0.06 N/A
Recommended protein levels for other cichlids are high, with dietary protein levels for 0.
mossambieus between 49- 50 per cent (Macintosh and De Silva, 1984). Degani (1993)
reports that P. seafare need high levels of protein (40- 50 per cent) and recommends the use
of commercial salmonid diets. This is confirmed by Willis et al. (1993) who found that use
of a salmonid diet resulted in superior growth of P. sea/are, compared to several commercial
aquarium fish diets. Several commercial growers and wholesalers of P. sea/are have also
found salmonid diets to be more cost effective and give better growth than specialised
aquarium foods (pers comm. R. Datodi, 1992). It should also be noted that Degani (1993)
indicated that, as well as requiring high levels of protein, the addition of a small quantity of
livefood significantly raises the growth of P. sea/are. It has been proposed that livefood
sources such as Artemia sp. may contain a micro-element absent in artificial diets (Degani,
1993).
Artemia sp. was the main source of livefood used for rearing fry in this study. This food
source was found to provide adequate nutrition (as evidenced by the growth and survival of
fry). However, it is thought that provision of a larger variety of zooplankton species and
99
nutritionally enhanced Artemia sp. may improve both growth and survival duting Stage II,
and should be the subject of further investigation.
The nutritional regime used appears to be adequate and is similar to that used by other
researchers (Degani, 1993) and by commercial farmers. Reasonable FCR are achieved, with
an expected FCR of 1.3 at a feeding rate of 8 %day·1• The salmonid diet used also offers a
cost effective alternative to the commercial aquatium diets currently available on the market
(Willis et. al., 1993 unpublished data). However, the nutritional requirements, in terms of
quality, need to be addressed at some stage and a specific diet developed for P. seafare. The
issue of feeding frequency should also be examined. Further investigation into the
nutritional regime used during hatchery and nursery stages may also prove useful in
improving growth and survival during these phases of production. This research should
address the use of larger zooplankton species during the nursery stage and the use of boosted
Artemia sp. for increasing survival and/or growth rates of P. seafare.
3. 6. 6 Water quality requirements
Maintenance of good water quality is important in ornamental fish culture. Poor water
quality, particularly pH, water hardness and nitrogenous compounds, can depress the growth
performance of cultured fish, and may compromise fish health (Forteath, 1990; Gratzek
et.al., 1992). This can result in generally poor quality or problems with opportunistic
diseases that may result in mortalities, and damage to skin and/or fins of fish rendering them
unsuitable for sale.
Water quality requirements for P. sea/are are poorly defined, with recommendations limited
to pH, water hardness and temperature. Very little data are available on the effects of
ammonia, or other nitrogenous compounds, on P. seafare. Daud et al. (1988) found 0.
mossambieus fry to have a fairly high tolerance of unionised ammonia, with a threshold
lethal concentration with no mortality of 0.24 mg/1 unionised ammonia. It is also thought
that high ammonia levels may cause damage to fin margins in Stage II fish and lead to
poorly developed, substandard dorsal and anal fins. The influence of other water quality
parameters, particularly nitrogenous compounds, on growth and quality of fish should be
determined and suitable water quality standards set.
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3.7 Summary
The data developed in this chapter indicates that P. sealare is well suited to intensive culture.
The hatchery procedures developed in this study are suitable for mass production of P.
sealare and are suitable for production of eggs and fry all year round. However, further
investigation into the considerable variability in individual fecundity is needed to increase
the reliability of egg production and reduce the numbers of broodstock needed. Another
important factor in intensive culture is fast growth rates and low FCR. P. sealare exhibits
good growth rates throughout the production cycle with grow-out times of 116 days for
large, 81 days for medium and 60 days for small sized P. sea/are. During the growth cycle
low FCR are achieved with an expected FCR of 1.3 at a feeding rate of 8 % day-1 for Stages
III- IV. The nutritional regime developed in this model is adequate for intensive culture
and the salmonid diet used also offers a cost effective alternative to the commercial aquarium
diets currently available on the market. However, the qualitative nutritional requirements of
P. sealare need to be addressed at some stage and a specific diet developed. Water quality
had no deleterious effects on the performance of P. seafare during this study. The tolerances
for pH, water hardness and temperature are well established, however, more data is needed to
determine the effects of other water quality parameters, particularly nitrogenous compounds,
on growth and performance of P. seafare.
The biological data presented here are used in Chapter 5 in the development of the physical
and economic sub-models in the design and operation of a fictitious intensive culture facility
based in Launceston, Tasmania. The following chapter presents an analysis of the
ornamental fish industry, focusing on the Australian industry and the market for P. sealare.
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