Black Bream (Acanthopagrus butcheri) Stock Assessment Report 2014/15 J. Earl, T.M. Ward and Q. Ye SARDI Publication No. F2008/000810-2 SARDI Research Report Series No. 885 SARDI Aquatic Sciences PO Box 120 Henley Beach SA 5022 January 2016 Report to PIRSA Fisheries and Aquaculture Earl, J. et al. (2016) Black Bream Stock Assessment Report 2014/15 Black Bream (Acanthopagrus butcheri) Stock Assessment Report 2014/15 Report to PIRSA Fisheries and Aquaculture J. Earl, T.M. Ward and Q. Ye SARDI Publication No. F2008/000810-2 SARDI Research Report Series No. 885 January 2016 i Earl, J. et al. (2016) Black Bream Stock Assessment Report 2014/15 This publication may be cited as: Earl, J., Ward, T.M. and Ye, Q. (2016). Black Bream (Acanthopagrus butcheri) Stock Assessment Report 2014/15. Report to PIRSA Fisheries and Aquaculture. South Australian Research and Development Institute (Aquatic Sciences), Adelaide. SARDI Publication No. F2008/000810-2. SARDI Research Report Series No. 885. 44pp. South Australian Research and Development Institute SARDI Aquatic Sciences 2 Hamra Avenue West Beach SA 5024 Telephone: (08) 8207 5400 Facsimile: (08) 8207 5406 http://www.pir.sa.gov.au/research DISCLAIMER The authors warrant that they have taken all reasonable care in producing this report. The report has been through the SARDI internal review process, and has been formally approved for release by the Research Chief, Aquatic Sciences. Although all reasonable efforts have been made to ensure quality, SARDI does not warrant that the information in this report is free from errors or omissions. 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. The SARDI Report Series is an Administrative Report Series which has not been reviewed outside the department and is not considered peer-reviewed literature. Material presented in these Administrative Reports may later be published in formal peer-reviewed scientific literature. © 2016 SARDI 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. Printed in Adelaide: January 2016 SARDI Publication No. F2008/000810-2 SARDI Research Report Series No. 885 Author(s): J. Earl, T.M. Ward and Q. Ye Reviewer(s): A. J. Fowler and M.A. Steer Approved by: S. Mayfield Science Leader - Fisheries Signed: Date: 22 January 2016 Distribution: PIRSA Fisheries and Aquaculture, Lakes and Coorong Consultative Committee, SAASC Library, University of Adelaide Library, Parliamentary Library, State Library and National Library Circulation: Public Domain ii Earl, J. et al. (2016) Black Bream Stock Assessment Report 2014/15 TABLE OF CONTENTS LIST OF FIGURES ................................................................................................................... IV LIST OF TABLES ...................................................................................................................... IV ACKNOWLEDGEMENTS .......................................................................................................... V EXECUTIVE SUMMARY ........................................................................................................... 1 1. GENERAL INTRODUCTION ............................................................................................... 2 1.1 Overview ...................................................................................................................... 2 1.2 Description of the fishery.............................................................................................. 2 1.3 Management of the fishery ........................................................................................... 4 1.4 Performance indicators for the fishery .......................................................................... 7 1.5 Previous stock assessments ........................................................................................ 7 1.6 Biology of Black Bream ................................................................................................ 8 2. COMMERCIAL FISHERY STATISTICS .............................................................................15 2.1 Introduction .................................................................................................................15 2.2 Methods ......................................................................................................................15 2.3 Results ........................................................................................................................17 2.4 Discussion ..................................................................................................................24 3. SIZE AND AGE STRUCTURES .........................................................................................25 3.1 Introduction .................................................................................................................25 3.2 Methods ......................................................................................................................25 3.3 Results ........................................................................................................................26 3.4 Discussion ..................................................................................................................28 4. PERFORMANCE INDICATORS ........................................................................................31 4.1 Introduction .................................................................................................................31 4.2 Methods ......................................................................................................................31 4.3 Results ........................................................................................................................31 4.4 Discussion ..................................................................................................................33 5. GENERAL DISCUSSION ...................................................................................................34 5.1 Information available for assessing fishery status .......................................................34 5.2 Current status of the LCF for Black Bream ..................................................................34 5.3 Uncertainty in the assessment ....................................................................................36 5.4 Future research needs ................................................................................................38 REFERENCES .........................................................................................................................39 iii Earl, J. et al. (2016) Black Bream Stock Assessment Report 2014/15 LIST OF FIGURES Figure 1. Map of the Lakes and Coorong region showing commercial reporting areas 4 – 16 of the LCF. 3 Figure 2. Estimates of total annual catch of Black Bream (bars) in South Australia from 1960/61 to 2014/15, by fishing sector. Information on the sector by which catches were taken was not available between 1960/61 to 1975/76. Estimates of annual freshwater inflows to the Coorong estuary (line) from 1970/71 to 2014/15 are also shown. ........................................................................................................................................... 17 Figure 3. Annual catches of Black Bream from the LCF from 1984/85 to 2014/15, by gear type. ............. 18 Figure 4. Average monthly catches (± S. E.) of Black Bream from the LCF from 1984/85 to 2014/15, expressed as a percentage of annual catch. .............................................................................................. 19 Figure 5. Annual targeted catch and effort for Black Bream using large mesh gill nets. (A) Targeted catch shown in tonnes, and as a percentage of total catch. (B) Comparison of two measures of targeted effort for large mesh gill nets, i.e. fisher days, net-days. (C) Comparison of two measures of CPUELMGN (± S. E.). Estimates of CPUELMGN were not available for 2009/10, as no targeted effort was reported for Black Bream. (*) represents confidential data. .................................................................................................................. 20 Figure 6. Annual catches of Black Bream from LCF commercial reporting areas from 1984/85 to 2014/15. .................................................................................................................................................................... 21 Figure 7. Contribution (%) of catches of Black Bream taken from areas north and south of Mark Point to the total catch for the LCF between 1984/85 and 2014/15. .............................................................................. 22 Figure 8. Annual freshwater inflows to the Coorong estuary from 1970/71 to 2014/15. Flow estimates were obtained from the regression based Murray hydrological model (MSM-BIGMOD, Murray–Darling Basin Authority). .................................................................................................................................................... 23 Figure 9. The relationship between freshwater inflow to the Coorong estuary and the proportion of the total catch taken from