Thesis Submitted for the Degree of Doctor of Philosophy
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kesis ýa 55 The Culture of African Catfish, Clarias gariepinus (Burchell) in Africa, with particular reference to controlled hatchery production Graham S Haylor Thesis submitted for the degree of Doctor of Philosophy Institute of Aquaculture, University of Stirling Stirling, FK9 4LA, Scotland March, 1992 For Albert, and his family ACKNOWLEDGEMENTS For introducing me to Africa I would like to thank Professor WS Richards. I am indebted to Professor Rj Roberts for the foresight and funds which enabled this piece of work to be undertaken at Stirling. I have borrowed heavily of time, patience and wisdom from so many over the past three years and to them I extend my heartfelt thanks. I would particularly like to acknowledge the guidance of my supervisors Dr Kim Jauncey and until his retirement Professor A Matty and the wordprocessing skills of Elspeth Gillespie. I am grateful to Professor Tom Hecht, Wynand Uys, and John Verreth for their useful comments on developmental stages. Finally thanks to Georgina for her support and encouragement during the production of this thesis and to Theodora for her distractions. -ii- ABSTRACT A rationale is presented for a primary nursing strategy and an on-growing strategy for Clarias gariepinus (Burchell) culture in Africa, thus providing a potential model for the development of culture technology for the species. Existing information pertaining to the production strategies identified is reviewed, highlighting the attributes of African catfish for aquaculture. Some of the current deficiencies and inconsistencies in available information pertaining to controlled hatchery production are addressed. The early developmental stages of Clarias gariepinus are defined, in order to promote consistent use of terminology and help farmers better address the changing needs of their developing stock. The pattern of growth and survival of larvae and fry is investigated at higher stocking densities than those used experimentally to provide a database for planning full-scale commercial operations. Tank design and water flow rates appropriate for Clarias gariepinus in hatcheries are investigated and recommendations made. Finally, in order to promote maximal growth rates of hatchery stocks the maximum daily feed intake of larvae in relation to different feeding regimes is estimated based on rates of gastric evacuation and return of appetite. An overview of the controlled hatchery production of Clarias gariepinus is presented. -iii- The Culture of African Catfish Clarias gariepinus (Burchell) in Africa with Particular Reference to Controlled Hatchery Production ' Page No Contents iv Tables viii Figures x Chapter 1: INTRODUCTION 1 1.1 Africa's developmental disadvantage 1 1.2 Addressing the food deficit 3 1.3 Aquaculture development in Africa 5 1.4 Objectives of the present work 8 Chapter 2: A STRATEGY FOR THE DEVELOPMENT OF 9 CULTURE TECHNOLOGY FOR CLARIAS GARIEPINUS IN AFRICA 2.1 Introduction 9 2.1.1 Guiding principles 2.1.2 Objectives and target groups 2.1.3 Assessmentof the comparative feasibility of different systems 2.2 An assessmentof farming strategies for the 13 primary nursing phase 2.2.1 Introduction 2.2.2 'Semi-intensive' methods of fry production 2.2.3 'Semi-intensive/intensive' methods of fry production 2.2.4 'Intensive' methods of fry production 2.2.5 A primary nursing strategy 2.3 An assessmentof farming strategies for 22 on-growing 2.3.1 Introduction 2.3.2 'Extensive' and 'semi-intensive' on-growing 2.3.3 'Intensive' on-growing 2.3.4 An on-growing strategy 2.4 Conclusions: A model for the development of 27 culture technology for African catfish Chapter 3: A SYNOPTIC REVIEW OF SOME ASPECTS OF THE 30 BIOLOGY AND CULTURE OF AFRICAN CATFISH 3.1 Introduction 30 3.2 Some aspects of the biology of Clarias 30 gariepinus of relevance to its culture 3.2.1 Introduction 3.2.2 Classification 3.2.3 Distribution and translocation 3.2.3.1 Distribution -iv- 3.2.3.2 Translocation and its risks 3.2.4 The breeding biology 3.2.4.1 Size at first maturity 3.2.4.2 Fecundity 3.2.4.3 The breeding season 3.2.4.4 Spawning behaviour 3.2.5 Natural diet and feeding habit 3.2.5.1 Introduction 3.2.5.2 Feeding physiology and behaviour 3.25.3 Feeding strategy 3.2.6 Airbreathing 3.2.6.1 Introduction 3.2.6.2 Oxygen consumption 3.3 Culture 47 3.3.1 Spawning 3.3.1.1 Introduction 3.3.1.2 Induced spawning 3.3.1.3 Induced spawning by manipulating environmental conditions 3.3.1.4 Induced spawning by manipulating the hypothalamic- pituitary-ovarian axis 3.3.1.4.1 The hypothalamic level: gonadotropin release- inhibitory Factor (GRIF) antagonists 3.3.1.4.2 The hypothalamic level: deca-neuropeptide stimulation of pituitary gonadotropin release. 3.3.1.4.3 The pituitary level: hormonal glycoprotein induction of spawning 3.3.1.4.4 The ovarian level: steroid hormone induction of spawning 3.3.2 Egg incubation 3.3.2.1 Growth and development 3.3.2.2 Egg incubation systems 3.3.2.2.1 Incubation funnels 3.3.2.2.2 Incubation trays 3.3.2.2.3 Induced natural spawning 3.3.3 Hatching 3.3.4 Larval rearing 3.3.4.1 Introduction 3.3.4.2 Larval feeds 3.3.4.3 Feeding and growth 3.3.4.4 Feeding frequency 3.3.4.5 Stocking density 3.3.4.6 Behavioral problems 3.3.4.6.1 Introduction 3.3.4.6.2 Cannibalism 3.34.6.3 Territoriality 3.3.5 Disease 3.3.5.1 Introduction 3.3.5.2 Protozoan parasitic infections 3.3.5.3 Metazoan parasitic infections 3.3.5.3.1 Platyhelminthes 3.3.5.3.2 Aschelminthes 3.3.5.3.5 Arthropods 3.3.5.4 Virus and bacterial infections 3.35.5 Fungal infections 3.3.5.6 Diseasesof unknown etiology and culture dependent diseases 3.3.6 On-growing and production 3.3.6.1 Introduction 3.3.6.2 Introduction of Clariasgariepinus to ponds 3.3.6.3 Fertilization -v- 3.3.6.4 Supplementary feeding 3.3.7 A stock model for semi-intensive Clarias gariepinus Culture 3.4 Production of Clarias gariepinus in Africa 101 3.5 Conclusions 104 Chapter 4: TERMINOLOGY FOR THE EARLY DEVELOPMENT STAGES OF 107 CLARIAS GARIEPINUS - WORKING DEFINITIONS FOR AQUACULTURE 4.1 Introduction 107 107 4.2 Larvae -a definition 4.2.1 The onset of the larval period 4.2.2 The end of the larval period 4.3 juvenile -a definition 110 4.4 A summary of the terminology of early life stages 112 Chapter 5: THE GROWTH AND SURVIVAL OF CLARIAS GARIEPINUS 113 LARVAE AT HIGH STOCKING DENSITY 5.1 Introduction 113 5.2 Methods and materials 114 5.2.1 Production of first feeding larvae 5.2.2 Feeding 5.2.3 The larval rearing system 5.2.4 A study of the effect of initial larval stocking density on growth and survival 5.2.5 An investigation of changesin growth rate over the early rearing period 5.2.6 Data analysis 5.3 Results 121 5.4 Discussion 133 5.5 Summary 139 Chapter 6: THE GROWTH AND SURVIVAL OF CLARIAS GARIEPINUS FRY 140 AT HIGH STOCKING DENSITY 6.1 Introduction 140 6.2 Methods and materials 141 6.2.1 An investigation of cannibalistic mortality, non-cannibalistic mortality and growth rate in relation to stocking density during fry rearing 6.2.2 Data Analysis 6.3 Results 146 6.4 Discussion 158 6.5 Summary 165 Chapter 7: AN INVESTIGATION OF TANK DESIGN AND WATER FLOW 167 RATES APPROPRIATE FOR CLARIAS GARIEPINUS IN HATCHERIES 7.1 Introduction 167 7.1.1 Tank design choice 7.1.2 The present study 7.2 Methods and materials 170 -vi- 7.2.1 The effect of a small increase in water depth 7.2.2 The effect of an increasein tank volume 7.2.3 The effect of an increasein diameter to depth ratio 7.2.4 The effect of flow rate on current velocity and its relation to tank dimensions and fish size 7.2.5 Data analysis 7.3 Results 178 7.4 Discussion 183 7.5 Summary 189 Chapter 8: AN ESTIMATE OF MAXIMUM DAILY FEED INTAKE OF 191 CLARIAS GARIEPINUS LARVAE 8.1 Introduction 191 8.2 Materials and methods 192 8.2.1 An estimate of satiation time, stomach capacity, gastric evacuation and return of appetite 8.2.2 Data analysis 8.3 Results 196 8.4 Discussion 199 8.5 Summary 204 Chapter 9: CONTROLLED HATCHERY PRODUCTION OF CLARIAS 208 ' GARIEPINUS - SUMMARY CONCLUSIONS 9.1 Introduction 208 9.2 Intensive primary nursing - requirements, 208 protocols and definitions 9.2.1 Spawning 9.2.2 Incubation of eggs 9.2.3 Hatching 9.2.4 Larval rearing 9.2.5 Fry rearing 9.2.6 End piece REFERENCES 216 APPENDIX I 246 APPENDIX II 252 -vii- Tables 1.1 International trade in Fisheries commodities by sub-Saharan African Countries 1988 (FAO 1991a). 2.1 A summary of the different methods used to culture Clarias gariepinus. 2.2 Predators of young Clariasgariepinus. 2.3 Fertilization regimes used in Clariasgariepinus nursery ponds. 2.4 A summary of methods used to on-grow Clarias gariepinus in Africa. 3.1 Median size at first maturity for different Clarias populations in Africa (from Bruton, 1979a). 3.2 Estimates of absolute fecundity (Bagenal, 1973) of different Clarias species (from Bruton, 1979a). 3.3 Breeding season of Clarias gariepinus in relation to rainfall and locality. 3.4 A comparison of spawning and parental care in catfish species.