FISHERIES RESEARCH REPORT NO. 165, 2007 Biological and Fisheries Data for Managing Deep Sea Crabs in Western Australia
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FISHERIES RESEARCH REPORT NO. 165, 2007 Biological and Fisheries Data for Managing Deep Sea Crabs in Western Australia Final FRDC Report – Project 2001/055 R. Melville-Smith, S.M.G. Norton and A.W. Thomson Australian Government Fisheries Research and Development Corporation Fisheries Research Division Western Australian Fisheries and Marine Research Laboratories PO Box 20 NORTH BEACH Western Australia 6920 Correct citation: Melville-Smith, R., Norton, S.M.G. and Thomson, A.W. 2007. Biological and Fisheries Data for Managing Deep Sea Crabs in Western Australia Final report to Fisheries Research and Development Corporation on Project No. 2001/055. Fisheries Research Report No. 165, Department of Fisheries, Western Australia, 248p. Appendix 6 is published and can be referenced separately. Published by Department of Fisheries, Western Australia. October 2007. ISSN: 1035 - 4549 ISBN: 1 877098 91 4 Enquiries: WA Fisheries and Marine Research Laboratories, PO Box 20, North Beach, WA 6920 Tel: +61 8 9203 0111 Email: [email protected] Website: http://www.fish.wa.gov.au Publications may be accessed through this website. A complete list of Fisheries Research Reports is available online at www.fish.wa.gov.au © Fisheries Research and Development Corporation and Department of Fisheries, Western Australia 2007. This work is copyright. Except as permitted under the Copyright Act 1968 (Cth), no part of this publication may be reproduced by any process, electronic or otherwise, without the specific written permission of the copyright owners. Neither may information be stored electronically in any form whatsoever without such permission. The Fisheries Research and Development Corporation plans, invests in and manages fisheries research and development throughout Australia. It is a statutory authority within the portfolio of the federal Minister for Agriculture, Fisheries and Forestry, jointly funded by the Australian Government and the fishing industry. Disclaimer Despite all due care and diligence being given by the Department of Fisheries – Government of Western Australia in the preparation of this document, the Department of Fisheries makes no warranty of any kind, expressed or implied, concerning the use of technology mentioned in this publication. 2 Fisheries Research Report [Western Australia] No. 165, 2007 Contents Non-technical summary ............................................................................................... 5 Objectives ................................................................................................................ 6 Outcomes Achieved To Date ................................................................................... 6 Acknowledgements ....................................................................................................... 7 1.0 General Introduction ............................................................................................ 8 1.1 Background ...................................................................................................... 8 1.2 Need ................................................................................................................. 9 1. Objectives ........................................................................................................ 10 1.4 Management of the Fishery ............................................................................. 10 1.5 Fishing methods ............................................................................................... 12 1.6 Extent of the Grounds ...................................................................................... 12 2.0 Spatial and temporal catch and effort trends .................................................... 13 2.1 Methods ........................................................................................................... 1 2.1.1 Data sources ........................................................................................... 1 2.1.2 Validation and choice of CAES and logbook information .................... 1 2.1. Analysis of logbook and CAES data ..................................................... 14 2.1.4 Establishing the extent of the grounds ................................................... 15 2.1.5 Establishing production by Zone ........................................................... 15 2.2 Results .............................................................................................................. 16 2.2.1 Catch data for legal sized crabs ............................................................. 16 2.2.2 Effort data for legal sized crabs ............................................................. 17 2.2. CPUE data for legal sized crabs ............................................................ 18 2.2.4 Logbook analysis for legal size crabs .................................................... 19 2.2.5 Logbook analysis for sub-legal size crabs ............................................. 22 2.2.6 Logbook analysis for ovigerous crabs ................................................... 25 2.2.7 Extent of the grounds by Zone .............................................................. 27 2.2.8 Production of crystal crabs per Zone ..................................................... 27 2. Discussion ........................................................................................................ 28 3.0 Monitoring the commercial catch composition .................................................. 31 .1 Methods ........................................................................................................... 31 .2 Results .............................................................................................................. 32 .2.1 Carapace length-width and live weight relationships ............................ 32 .2.2 Catch monitoring ................................................................................... 3 .2. Male crab length-frequency monitoring ................................................ 34 .2.4 Female crab length-frequency monitoring ............................................ 36 . Discussion ........................................................................................................ 38 4.0 Effect of escape gaps ............................................................................................. 40 4.1 Introduction ...................................................................................................... 40 4.2 Methods and sampling regime ......................................................................... 40 4.2.1 Equipment .............................................................................................. 41 4.2.2 Sampling ................................................................................................ 42 4.2. Data analysis .......................................................................................... 42 4.2 Results .............................................................................................................. 42 Fisheries Research Report [Western Australia] No. 165, 2007 5.0 Movement of tagged crystal crabs ....................................................................... 44 5.1 Introduction ...................................................................................................... 44 5.2 Methods ........................................................................................................... 44 . Results .............................................................................................................. 46 5. Discussion ........................................................................................................ 52 6.0 Growth of tagged crystal crabs ............................................................................ 54 6.1 Introduction ...................................................................................................... 54 6.2 Methods ........................................................................................................... 54 6. Data analysis .................................................................................................... 55 6.4 Results .............................................................................................................. 55 6.5 Discussion ........................................................................................................ 62 7.0 Depletion experiments ........................................................................................... 65 7.1 Introduction ...................................................................................................... 65 2.2 Methods ........................................................................................................... 65 2. Results .............................................................................................................. 66 7..1 Study site ............................................................................................... 66 7..2 Temperature and depth data ................................................................... 67 7.. Catch data .............................................................................................. 68 7.4 Discussion ........................................................................................................ 69 8.0 Assessment of the stock ......................................................................................... 71 8.1 Introduction .....................................................................................................