A Trophic Model for Gulf St Vincent: Balancing Exploitation of Three Fisheries in an EBFM Framework
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A trophic model for Gulf St Vincent: Balancing exploitation of three fisheries in an EBFM framework Simon D Goldsworthy, Maylene Loo, Anthony Fowler, Michael Steer and Craig Noell April 2017 FRDC Project No. 2013/031 A trophic model for Gulf St Vincent: balancing exploitation of three fisheries ii © 2017 Fisheries Research and Development Corporation and South Australian Research and Development Institute. All rights reserved. ISBN: 978-1-921563-93-5 A trophic model for Gulf St Vincent: Balancing exploitation of three fisheries in an EBFM framework. 2013/031 2017 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. 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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 readers 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: Simon D. Goldsworthy Address: 25 Geils Court Address: SARD Aquatic Sciences Deakin ACT 2600 2 Hamra Avenue Phone: 02 6285 0400 West Beach SA 5024 Fax: 02 6285 0499 Phone: 08 8207 5325 Email: [email protected] Fax: Web: www.frdc.com.au Email: [email protected] In submitting this report, the researcher has agreed to FRDC publishing this material in its edited form. A trophic model for Gulf St Vincent: balancing exploitation of three fisheries iii Contents Contents ................................................................................................................................................. iii Tables ...................................................................................................................................................... v Figures ................................................................................................................................................... vi Acknowledgments ................................................................................................................................ vii Abbreviations ....................................................................................................................................... vii Executive Summary .............................................................................................................................. 1 1 Introduction ......................................................................................................................................... 4 1.1 Background ..................................................................................................................................4 1.2 Need .............................................................................................................................................5 1.3 Objectives ....................................................................................................................................5 2 Methodology ........................................................................................................................................ 6 2.1 Ecopath and mass balance approach ............................................................................................6 2.2 Model area and structure ..............................................................................................................6 2.3 Model fitting ................................................................................................................................7 2.4 Ecosystem indicators ...................................................................................................................8 2.5 Scenario testing ............................................................................................................................8 3 Results................................................................................................................................................ 13 3.1 Trophic structure and flow (Ecopath) ........................................................................................13 3.2 Model fitting (Ecosim) ...............................................................................................................13 3.3 Temporal changes in GSV ecosystem .......................................................................................16 Trends in catch ..........................................................................................................................16 Group biomasses .......................................................................................................................16 Effects of fishing .......................................................................................................................17 3.2 Trophic role of three key species and impact of Snapper ..........................................................25 Diet of three key species ...........................................................................................................25 Predation on three key species ..................................................................................................25 Sensitivity analysis ....................................................................................................................26 Impact of increasing biomass of Snapper on GSV ecosystem ..................................................26 3.3 Optimisation of future ecological and economic performance ..................................................32 Impact of reducing Snapper biomass on high value commercial fisheries and on the GSV ecosystem ..................................................................................................................................32 4 Discussion .......................................................................................................................................... 37 Dynamic management arrangements in the GSV ecosystem ..........................................................37 Trophodynamic indicators of fisheries status and impact ................................................................41 Trophic relationships – role of Snapper in GSV ecosystem ............................................................43 Could a directed fishery for Snapper be used to optimise ecological and economic performance of Blue Crab and prawn fisheries? ..............................................................................45 5 Conclusion ......................................................................................................................................... 46 6 Implications ....................................................................................................................................... 47 7 Recommendations ............................................................................................................................ 48 8 Further development 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