Prawn and crab harvest optimisation: a bio-physical management tool Final Report to the Fisheries Research and Development Corporation McLeay, L., Doubell, M., Roberts, S., Dixon, C., Andreacchio, L., James, C., Luick, J. and Middleton, J. August 2015 FRDC Project No 2008/011 © 2015 Fisheries Research and Development Corporation and South Australian Research and Development Institute. All rights reserved. ISBN 978-1-921563-76-8 Prawn and Crab harvest optimisation: a bio-physical management tool. Final Report to the Fisheries Research and Development Corporation 2008/011 2015 Ownership of Intellectual property rights Unless otherwise noted, copyright (and any other intellectual property rights, if any) in this publication is owned by the Fisheries Research and Development Corporation and the South Australian Research and Development Institute. This work is copyright. Apart from any use as permitted under the Copyright Act 1968 (Cth), no part may be reproduced by any process, electronic or otherwise, without the specific written permission of the copyright owner. Neither may information be stored electronically in any form whatsoever without such permission. This publication (and any information sourced from it) should be attributed to McLeay, L., Doubell, M., Roberts, S., Dixon, C., Andreacchio, L., James, C., Luick, J. and Middleton, J. South Australian Research and Development Institute (Aquatic Sciences) 2015, Prawn and crab harvest optimisation: a bio-physical management tool. Final Report to the Fisheries Research and Development Corporation. Adelaide, August. Creative Commons licence All material in this publication is licensed under a Creative Commons Attribution 3.0 Australia Licence, save for content supplied by third parties, logos and the Commonwealth Coat of Arms. 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SARDI does not accept any liability for the contents of this report or for any consequences arising from its use or any reliance placed upon it. Material presented in these Administrative Reports may later be published in formal peer-reviewed scientific literature. The information, opinions and advice contained in this document may not relate, or be relevant, to a reader’s particular circumstances. Opinions expressed by the authors are the individual opinions expressed by those persons and are not necessarily those of the publisher, research provider or the FRDC. 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. Researcher Contact Details FRDC Contact Details Name: L.J. McLeay Address: 25 Geils Court, Address: c/o SARDI Aquatic Sciences, Deakin ACT 2600 2 Hamra Ave, West Beach 5024 Phone: 02 6285 0400 Phone: 08 8207 5400 Fax: 02 6285 0499 Fax: 08 8207 5481 Email: [email protected] Email: [email protected] Web: www.frdc.com.au In submitting this report, the researcher has agreed to FRDC publishing this material in its edited form. ii Contents Acknowledgments .................................................................................................................viii Abbreviations .........................................................................................................................viii Executive Summary ................................................................................................................. 9 1 Introduction.......................................................................................................................12 2 Need ...................................................................................................................................16 3 Objectives .........................................................................................................................17 4 Methods .............................................................................................................................18 4.1 Biological models ....................................................................................................18 4.1.1 Overview of data sources ....................................................................................18 4.1.2 Larval duration .....................................................................................................18 4.1.2.1 Western King Prawn ........................................................................................18 4.1.2.2 Blue Swimmer Crab .........................................................................................20 4.1.3 Larval behaviour ..................................................................................................20 4.1.3.1 Western King Prawn ........................................................................................20 4.1.3.2 Blue Swimmer Crab .........................................................................................21 4.1.4 Adult reproduction ................................................................................................21 4.1.4.1 Western King Prawn ........................................................................................21 4.1.4.2 Blue Swimmer Crab .........................................................................................25 4.2 Bio-physical model ..................................................................................................27 4.2.1 Hydrodynamic modelling ......................................................................................27 4.2.2 Larval tracking model ...........................................................................................28 4.2.2.1 Overview ..........................................................................................................28 4.2.2.2 Initial conditions and source/sink regions .........................................................28 4.2.2.3 Modelled scenarios of larval dispersal and settlement ......................................30 4.3 Harvest sensitivity analyses .....................................................................................31 5 Results ..............................................................................................................................34 5.1 Biological models ....................................................................................................34 5.1.1 Larval duration models .........................................................................................34 5.1.1.1 Western King Prawn ........................................................................................34 5.1.1.2 Blue Swimmer Crab .........................................................................................36 5.1.2 Larval behaviour models ......................................................................................36 5.1.3 Adult reproductive models....................................................................................36 5.1.3.1 Western King Prawn ........................................................................................36 5.1.3.2 Blue Swimmer Crab .........................................................................................42 5.2 Bio-physical model for Spencer Gulf .......................................................................45 5.2.1 Hydrodynamic modelling ......................................................................................45 5.2.1.1 Model validation ...............................................................................................45 5.2.1.2 Patterns of larval dispersal and connectivity .....................................................47 5.3 Harvest sensitivity analyses – case study: the Spencer Gulf Prawn Fishery ............51 5.3.1 Overview ..............................................................................................................51 5.3.2 Areas contributing to larval settlement success (pre-fishing) ...............................51 5.3.3 Distribution of catch .............................................................................................53 5.3.4 Effects of fishing on larval settlement...................................................................54 5.3.5 Harvest sensitivity analyses .................................................................................57 iii 6 Discussion ........................................................................................................................59 6.1 Larval duration .........................................................................................................59