Spencer Gulf Research Initiative: Development of an Ecosystem Model for Fisheries and Aquaculture Bronwyn M. Gillanders, Simon Goldsworthy, Thomas A.A. Prowse, Mark Doubell, John Middleton, Paul Rogers, Jason E. Tanner, Nathan A. Clisby, Charles James, John Luick, Paul van Ruth, Corey J. A. Bradshaw, Tim M. Ward May 2015 FRDC Project No 2011/205 Development of a Spencer Gulf ecosystem model for fisheries and aquaculture 2 © 2015 Fisheries Research and Development Corporation. All rights reserved. ISBN 978-0-646-93971-1 Spencer Gulf Research Initiative: Development of an Ecosystem Model for Fisheries and Aquaculture 2011/205 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, University of Adelaide and SARDI Aquatic Sciences. This publication (and any information sourced from it) should be attributed to Gillanders, BM, S Goldsworthy, TAA Prowse, M Doubell, J Middleton, P Rogers, JE Tanner, NA Clisby, C James, J Luick, P van Ruth, CJA Bradshaw, TM Ward (2015) Spencer Gulf research initiative: Development of an ecosystem model for fisheries and aquaculture. University of Adelaide and SARDI Aquatic Sciences, Adelaide. CC BY 3. 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. Creative Commons Attribution 3.0 Australia Licence is a standard form licence agreement that allows you to copy, distribute, transmit and adapt this publication provided you attribute the work. A summary of the licence terms is available from creativecommons.org/licenses/by/3.0/au/deed.en. The full licence terms are available from creativecommons.org/licenses/by/3.0/au/legalcode. Inquiries regarding the licence and any use of this document should be sent to: [email protected]. Disclaimer The authors do not warrant that the information in this document is free from errors or omissions. The authors do not accept any form of liability, be it contractual, tortious, or otherwise, for the contents of this document or for any consequences arising from its use or any reliance placed upon it. 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: Bronwyn M. Gillanders Address: 25 Geils Court Address: School of Biological Sciences Deakin ACT 2600 University of Adelaide, SA 5005, Australia Phone: 02 6285 0400 Phone: 61 8 8313 6235 Fax: 02 6285 0499 Fax: 61 8 8313 4364 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. Development of a Spencer Gulf ecosystem model for fisheries and aquaculture 3 Contents Contents .................................................................................................................................................. 3 Tables ...................................................................................................................................................... 5 Figures ..................................................................................................................................................... 6 Acknowledgments .................................................................................................................................. 8 Abbreviations ......................................................................................................................................... 9 Executive Summary ............................................................................................................................. 10 1 Introduction .................................................................................................................................... 13 1.1 Background ............................................................................................................................ 13 1.2 Need ....................................................................................................................................... 14 1.3 Objectives ............................................................................................................................... 16 2 A three-dimensional hydrodynamic-biogeochemical model for Spencer Gulf .................. 17 2.1 Introduction ............................................................................................................................ 17 2.2 Methods .................................................................................................................................. 18 2.2.1 Hydrodynamic model ................................................................................................... 18 2.2.2 Biogeochemical model ................................................................................................. 18 2.2.3 Anthropogenic nutrient sources and scenario studies ................................................... 19 2.3 Results and Discussion ........................................................................................................... 20 2.3.1 Control scenario: simulation of the annual cycle ......................................................... 20 2.3.2 Alternative scenario studies .......................................................................................... 21 3 Modelling seagrass and macroalgae distributions within Spencer Gulf .................................. 31 3.1 Introduction ............................................................................................................................ 31 3.2 Methods .................................................................................................................................. 32 3.2.1 Habitat cover and putative environmental covariates ................................................... 32 3.2.2 Statistical distribution models ...................................................................................... 32 3.2.3 Model selection ............................................................................................................. 33 3.2.4 Habitat predictions and benthic productivity estimates for Spencer Gulf. ................... 33 3.2.5 Biomass and productivity estimates for benthic primary producers ............................ 33 3.3 Results and Discussion ........................................................................................................... 33 3.3.1 Statistical distribution models ...................................................................................... 33 3.3.2 Estimates of biomass and productivity for each habitat ............................................... 35 3.3.3 Key assumptions ........................................................................................................... 35 4 Development of a Spencer Gulf ecosystem model for fisheries and aquaculture .................... 37 4.1 Introduction ............................................................................................................................ 37 4.2 Methods .................................................................................................................................. 37 4.2.1 Ecopath and mass balance approach ............................................................................ 37 4.2.2 Model area and structure .............................................................................................. 37 4.2.3 Model fitting ................................................................................................................. 41 4.2.4 Ecosystem indicators .................................................................................................... 41 4.2.5 Ecospace model ............................................................................................................ 41 4.2.6 Scenario testing ............................................................................................................. 41 4.3 Results and Discussion ........................................................................................................... 42 4.3.1 Trophic structure and flow ........................................................................................... 42 Development of a Spencer Gulf ecosystem model for fisheries and aquaculture 4 4.3.2 Food-web control and model fitting ............................................................................. 44 4.3.3 Temporal changes in group biomass ............................................................................ 51 4.3.4 Ecosystem indicators .................................................................................................... 53 4.3.5 Ecospace ......................................................................................................................