Habitat, growth and life history of the goby Parapocryptes serperaster Minh Quang Dinh, BSc. MSc. A thesis submitted for the degree of Doctor of Philosophy School of Biological Sciences Faculty of Science & Engineering Flinders University December 2015 CONTENTS CONTENTS.............................................................................................................. i LIST OF TABLES ................................................................................................... v LIST OF FIGURES ................................................................................................. vi DECLARATION .................................................................................................. viii ABSTRACT............................................................................................................ ix ACKNOWLEDGEMENT ....................................................................................... xi CHAPTER 1: GENERAL INTRODUCTION .......................................................... 1 1.1. Coastal and estuarine ecosystems and fisheries .............................................. 1 1.2. Coastal and estuarine fisheries in the Mekong Delta....................................... 2 1.3. Habitat use and features ................................................................................. 6 1.4. Growth pattern and condition factor variation ................................................ 7 1.5. Food and feeding habit .................................................................................. 8 1.6. Reproductive biology ..................................................................................... 9 1.7. Population and age structure ........................................................................ 10 1.8. Objectives of the study ................................................................................ 11 1.9. Thesis organisation ...................................................................................... 12 1.10. References ................................................................................................. 13 CHAPTER 2: BURROW USE AND FEATURES ................................................. 22 2.1. Abstract ....................................................................................................... 22 2.2. Introduction ................................................................................................. 22 2.3. Materials and methods ................................................................................. 24 2.3.1. Study site .............................................................................................. 24 2.3.2. Burrow casting and analysis .................................................................. 25 2.3.3. Laboratory experiment and burrowing behavioural observations ........... 26 2.3.4. Data analysis ......................................................................................... 28 2.4. Results ......................................................................................................... 28 2.4.1. Burrow structure and its relationships with fish size and season ............ 28 2.4.2. Burrowing activities and utilisation ....................................................... 31 2.5. Discussion ................................................................................................... 32 2.5.1. Burrowing morphology ......................................................................... 32 2.5.2. Burrowing activities and utilisation ....................................................... 35 2.6. Acknowledgments ....................................................................................... 36 2.7. References ................................................................................................... 36 CHAPTER 3: GROWTH PATTERN AND CONDITION FACTOR VARIATION ......................................................................................................... 40 i 3.1. Abstract ....................................................................................................... 40 3.2. Introduction ................................................................................................. 40 3.3. Materials and methods ................................................................................. 41 3.3.1. Study site .............................................................................................. 41 3.3.2. Fish collection....................................................................................... 42 3.3.3. Data analysis ......................................................................................... 43 3.4. Results ......................................................................................................... 43 3.4.1. Sex ratio and morphometric measurements ........................................... 43 3.4.2. Length-weight relationships .................................................................. 45 3.4.3. The condition factor (K) ........................................................................ 46 3.5. Discussion ................................................................................................... 48 3.5.1. Sex ratio and morphometric traits .......................................................... 48 3.5.2. Length-weight relationships .................................................................. 48 3.5.3. Condition factor (K) .............................................................................. 50 3.6. Acknowledgments ....................................................................................... 51 3.7. References ................................................................................................... 51 CHAPTER 4: FOOD AND FEEDING HABIT ...................................................... 54 4.1. Abstract ....................................................................................................... 54 4.2. Introduction ................................................................................................. 54 4.3. Materials and methods ................................................................................. 57 4.3.1. Study site .............................................................................................. 57 4.3.2. Fish collection....................................................................................... 57 4.3.3. Feeding habit and intensity determination ............................................. 57 4.3.4. Diet composition and index of relative importance ................................ 58 4.3.5. Diet breadth and feeding strategy .......................................................... 59 4.3.6. Data analysis ......................................................................................... 59 4.4. Results ......................................................................................................... 60 4.4.1. Relative gut length and gut fullness ....................................................... 60 4.4.2. General diet composition ...................................................................... 62 4.4.3. Seasonal and intraspecific variations in diet composition ...................... 63 4.4.4. Diet breadth, feeding strategy and prey election .................................... 67 4.5. Discussion ................................................................................................... 70 4.6. Acknowledgement ....................................................................................... 74 4.7. References ................................................................................................... 74 CHAPTER 5: REPRODUCTIVE BIOLOGY ......................................................... 79 5.1. Abstract ....................................................................................................... 79 ii 5.2. Introduction ................................................................................................. 79 5.3. Materials and methods ................................................................................. 81 5.3.1. Study site description and specimen collection ...................................... 81 5.3.2. Classification of gonad stage and gamete development ......................... 82 5.3.3. Gonadosomatic index, body length at sexual maturity and fecundity ..... 82 5.3.4. Data analyses ........................................................................................ 83 5.4. Results ......................................................................................................... 83 5.4.1. Environmental variables and sex ratio ................................................... 83 5.4.2. Development of ovary and testis ........................................................... 84 5.4.3. Gonadosomatic index, length at first maturation and fecundity .............. 85 5.5. Discussion ................................................................................................... 89 5.6. Acknowledgements ..................................................................................... 92 5.7. References ................................................................................................... 92 CHAPTER 6: POPULATION AND AGE STRUCTURE ...................................... 97 6.1. Abstract ....................................................................................................... 97 6.2. Introduction ................................................................................................