University of Warwick institutional repository: http://go.warwick.ac.uk/wrap A Thesis Submitted for the Degree of PhD at the University of Warwick http://go.warwick.ac.uk/wrap/57704 This thesis is made available online and is protected by original copyright. Please scroll down to view the document itself. Please refer to the repository record for this item for information to help you to cite it. Our policy information is available from the repository home page. Assessment of demersal fishery resources in Brunei Darussalam Syazana Ebil BSc., MSc. Thesis submitted in fulfilment of the requirements for the degree of Doctor of Philosophy in Biological Sciences School of Life Sciences (Environmental Resource Management) University of Warwick March 2013 Contents Contents ....................................................................................................................... ii List of Figures ............................................................................................................ vii List of Tables................................................................................................................ x Acknowledgements .................................................................................................... xii Declaration ................................................................................................................ xiii Summary ................................................................................................................... xiv List of Abbreviations.................................................................................................. xv CHAPTER 1 General Introduction ....................................................................................... 1 1.1 Background ............................................................................................................ 2 1.2 Brunei Darussalam, coastal features, and climate and environmental status ......... 4 1.3 State of marine capture fisheries in Brunei Darussalam ........................................ 8 1.3.1 Fisheries management and research ................................................................ 9 1.3.2 The fishing fleets ........................................................................................... 11 1.3.2.1 The large-scale sector ............................................................................. 12 1.3.2.2 The small-scale sector ............................................................................ 13 1.3.3 Marine fishery resources of Brunei ............................................................... 15 1.4 Research aims and objectives............................................................................... 17 1.5 Thesis organisation: Summary outline of chapters .............................................. 18 CHAPTER 2 Review on Assessment of Tropical Fishery Resources ............................... 19 2.1 Overview of tropical fish stock assessment ......................................................... 20 2.2 Data requirements for development of indicators ................................................ 26 2.2.1 Assessing stock status using catch-effort data .............................................. 28 2.2.2 The ‘Catch per Unit Effort’ model ................................................................ 30 2.2.3 The ecosystem-based approach ..................................................................... 33 2.3 Contribution of local ecological knowledge (LEK) in stock assessment and fishery management ................................................................................................... 37 2.3.1 The “Shifting Baseline Syndrome” ............................................................... 39 2.3.2 Formalisation of LEK with geographical information system (GIS)............ 41 2.3.3 Application of fuzzy logic concept in quantification of LEK ....................... 42 2.4 Marine environmental variability and fishery resources ...................................... 43 ii 2.4.1 Impact of climate change on tropical marine ecosystem and fishery ........... 45 2.5 Earlier studies on fishery and stock assessments in Brunei Darussalam ............. 47 CHAPTER 3 Overview of Brunei marine ecosystem in the past decade via trophodynamic indicators and community structure analyses ................. 50 3.1 Introduction .......................................................................................................... 51 3.2 Materials and methods ......................................................................................... 52 3.2.1 Study area ...................................................................................................... 52 3.2.2 Catch data and trophic level estimates .......................................................... 52 3.2.3 Data analyses ................................................................................................. 56 3.2.3.1 Mean trophic level (MTL) and Fishing-in-Balance (FiB) index ........... 56 3.2.3.2 Trophic spectra (TS) .............................................................................. 57 3.2.3.3 Statistical analyses ................................................................................. 58 3.3 Results .................................................................................................................. 59 3.3.1 Exploratory analysis: Trends in annual catch and effort ............................... 59 3.3.2 Trends of trophic-based indicators ................................................................ 62 3.3.3 Trends in species composition of catch ........................................................ 63 3.3.4 Catch trophic spectra analysis ....................................................................... 66 3.4 Discussion and Conclusion .................................................................................. 68 CHAPTER 4 Exploring human and environmental influence on recent abundance trends of selected demersal stocks in Brunei ............................................... 74 4.1 Introduction .......................................................................................................... 75 4.2 Materials and Methods ......................................................................................... 77 4.2.1 Study area ...................................................................................................... 77 4.2.2 Official fishery-dependent data and data selection ....................................... 77 4.2.3 Environmental data collation ........................................................................ 79 4.2.3.1 Sea-surface temperature (SST) data ....................................................... 79 4.2.3.2 Chlorophyll-a concentration (chl-a) data ............................................... 79 4.2.3.3 Precipitation data .................................................................................... 80 4.2.3.4 Indices of the Southern Oscillation (SOI) .............................................. 80 4.2.4 Effort unit selection ....................................................................................... 80 4.2.5 Standardisation of CPUE .............................................................................. 81 4.2.6 Definition of stock status based on catch ...................................................... 83 4.2.7 Statistical analyses ........................................................................................ 83 iii 4.3 Results .................................................................................................................. 84 4.3.1 Exploratory analysis: distribution by gear .................................................... 84 4.3.2 Exploratory analysis: short- and long-term changes in environmental variables ................................................................................................................. 85 4.3.3 Best measure of effort ................................................................................... 87 4.3.4 Standardisation of CPUE .............................................................................. 88 4.3.5 Lagged-effects of environmental variables on stocks’ CPUE index ............ 90 4.3.6 Trends in catch and CPUE index of demersal stocks in Brunei between 2000 and 2009 ................................................................................................................. 93 4.4 Discussion and Conclusion ................................................................................ 101 4.4.1 Best measure of effort ................................................................................. 101 4.4.2 CPUE standardisation ................................................................................. 103 4.4.3 Potential influence of environmental variability on selected demersal stocks in Brunei ............................................................................................................... 106 4.4.4 Probable cause of non-proportionality ........................................................ 111 4.4.5 Spatio-temporal changes in CPUE of demersal stocks in Brunei ............... 113 4.4.6 General limitations of analyses ................................................................... 115 CHAPTER 5 Utilisation of local ecological knowledge to assess status of selected demersal stocks in Brunei ..........................................................................