CRC REEF RESEARCH TECHNICAL REPORT DESIGN OF EXPERIMENTAL INVESTIGATIONS OF THE EFFECTS OF LINE AND SPEAR FISHING ON THE GREAT BARRIER REEF B.D. Mapstone1, R.A. Campbell2, & A.D.M Smith2 1CRC Reef Research Centre c/- James Cook University of North Queensland, Townsville, QLD 4811 2CSIRO Division of Fisheries, Hobart, TAS 7000 A report funded by the CRC Reef Research Centre. The CRC Reef Research Centre was established under the Australian Government's Cooperative Research Centres Program. The Centre, established in 1993, undertakes an integrated program of applied research and development, training and education, aimed at increasing opportunities for ecologically sustainable development of the Great Barrier Reef and providing an improved scientific basis for Reef management and regulatory decision making. CRC Reef Research Centre c/- James Cook University TOWNSVILLE QLD 4811 Phone: (077) 81 4976 Fax: (077) 81 4099 Email: [email protected] ? Cooperative Research Centre for Ecologically Sustainable Development of the Great Barrier Reef National Library of Australia Cataloguing-in- Publication entry Mapstone, Bruce D. (Bruce David). Design of experimental investigations of the effects of line and spear fishing on the Great Barrier Reef. Bibliography. Includes index. ISBN 1 876054 05 0. 1. Fisheries - Research - Queensland - Great Barrier Reef - Methodology. I. Smith, A.D.M. (Anthony David Miln), 1953- . II. Campbell, Robert Alan, 1957 - . III. Cooperative Research Centre for Ecologically Sustainable Development of the Great Barrier Reef (Australia). IV. Title. (Series: CRC Reef Research technical report; 7). 639.20720943 This publication should be cited as: Mapstone, B.D., Campbell, R.A. and Smith, A.D.M. (1996) Design of experimental investigations of the effects of line and spear fishing on the Great Barrier Reef CRC Reef Research Centre Technical Report No. 7 Townsville; CRC Reef Research Centre, 86pp. This work is copyright. The Copyright Act 1968 permits fair dealing for study, research, news reporting, criticism or review. Selected passages, tables or diagrams may be reproduced for such purposes provided acknowledgement of the source is included. Major extracts of the entire document may not be reproduced by any process without written permission of the Director, CRC Reef Research Centre. Published by the Cooperative Research Centre for Ecologically Sustainable Development of the Great Barrier Reef. Further copies may be obtained from CRC Reef Research Centre, c/- James Cook University Post Office, Townsville, QLD 4811. Printed by James Cook University of North Queensland. TABLE OF CONTENTS INTRODUCTION .................................................................................................................. 1 PREVIOUS PROPOSALS FOR FISHING EXPERIMENTS ................................................ 5 EVALUATION OF POTENTIAL EXPERIMENTAL DESIGNS ......................................... 9 OBJECTIVES OF FUTURE REEF-SCALE EXPERIMENTS..............................................10 Selection of Design Alternatives ...........................................................................................11 Potential Treatments...................................................................................................... 11 Constraints on Design Options ..................................................................................... 13 Duration ....................................................................................................................... 13 Logistics........................................................................................................................ 13 Generality of Results..................................................................................................... 14 Availability of suitable reefs.......................................................................................... 15 Impacts of Experiments ................................................................................................. 15 Cost............................................................................................................................... 15 Designs Examined......................................................................................................... 16 Computer Simulations ..........................................................................................................17 Population Dynamics ................................................................................................... 19 Initialisation ................................................................................................................. 20 Larval Supply ............................................................................................................... 20 Recruitment .................................................................................................................. 22 Mortality ...................................................................................................................... 23 Migration ..................................................................................................................... 24 Management and Experimental Treatments .................................................................. 24 Sampling Variation....................................................................................................... 25 Monte-Carlo Simulations.............................................................................................. 26 Necessity of Imposed Fishing Pressure......................................................................... 29 Sensitivity to variation in recruitment........................................................................... 29 Sensitivity to management and fishing parameters ....................................................... 32 Effects of experimental design..................................................................................... 32 Analyses of Simulation Data......................................................................................... 33 Existing Information & Demographic Parameters for Simulation Models .................................34 Variation in Larval Supply & Recruitment.................................................................... 34 Mortality ...................................................................................................................... 35 Natural Mortality ......................................................................................................... 35 Fishing Mortality.......................................................................................................... 36 Inter-reef movement...................................................................................................... 37 Inter-reef & inter-cluster variation in estimated abundance......................................... 38 Sampling Variation....................................................................................................... 39 Trawling mortality ........................................................................................................ 39 RESULTS OF SIMULATIONS ..........................................................................................40 Necessity of Imposed Fishing Pressure ......................................................................... 40 Sensitivity to variation in recruitment & inter-reef movement........................................ 41 Sensitivity to management and fishing parameters ........................................................ 44 Effects of experimental design ..................................................................................... 46 DISCUSSION........................................................................................................................48 Preferred Designs ...............................................................................................................48 Implementation of Experiments.............................................................................................52 Imposing Fishing Treatments........................................................................................ 52 Critical Data ................................................................................................................ 55 Fishery-independent Estimates of Abundance .............................................................. 55 Fishery-dependent estimates of Abundance & Fishing Behaviour................................ 56 Size- and Age-structure Data ....................................................................................... 57 Background Fishing Effort .......................................................................................... 58 Reproductive Biology ................................................................................................... 57 Logistic Considerations & Coordination...................................................................... 60 CONCLUSIONS & RECOMMENDATIONS.........................................................................62 ACKNOWLEDGMENTS.......................................................................................................62 REFERENCES.......................................................................................................................63 APPENDIX 1: MODELLING POPULATION DYNAMICS..................................................69 Larval Supply & Recruitment