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Project No. 2007/040 Selectivity and bycatch reduction of Tiger Flathead and Eastern School Whiting nets in the Danish seine fishery Matt Koopman, Paul McCoy, Vladimir Troynikov, Juan Matias Braccini, and Ian Knuckey Project No. 2007/040 Selectivity and bycatch reduction of Tiger Flathead and Eastern School Whiting nets in the Danish seine fishery Matt Koopman, Paul McCoy, Vladimir Troynikov, Juan Matias Braccini, and Ian Knuckey Fisheries Victoria, Fisheries Research Branch, Department of Primary Industries, Queenscliff, Victoria November 2010 Project Number 2007/040 Selectivity of Danish seine gear iii © Fisheries Research and Development Corporation and Fisheries Victoria. 2010 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. ISBN 978‐1‐74264‐573‐5 Preferred way to cite: Koopman, M.T., McCoy, P., Troynikov, V.S., Braccini, J.N. and Knuckey, I.A. (2010). Selectivity and bycatch reduction of Tiger Flathead and Eastern School Whiting nets in the Danish seine fishery. Final report to Fisheries Research and Development Corporation Project No. 2007/040. Department of Primary Industries, Queenscliff. Published by Fisheries Victoria, Department of Primary Industries, Queenscliff, Victoria, 3225. Formatted/designed by Fisheries Victoria Queenscliff Printed by Fisheries Victoria Queenscliff, Victoria 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 reader’s particular circumstance. 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. Selectivity of Danish seine gear iv Table of Contents NON‐TECHNICAL SUMMARY........................................................................ 1 Acknowledgments................................................................................................. 3 Background............................................................................................................. 4 Need ......................................................................................................................... 5 Objectives................................................................................................................ 5 Methods................................................................................................................... 6 Optimum size and age‐at‐capture...........................................................................................................................6 Modelling yield‐and value‐per‐recruit ................................................................................................................6 Data...........................................................................................................................................................................7 Selectivity of Danish seine gear..............................................................................................................................8 Vessel and fishing gear ..........................................................................................................................................8 Covered codend field methods...........................................................................................................................11 Alternate haul field methods...............................................................................................................................11 Data collection.......................................................................................................................................................11 Underwater video analysis..................................................................................................................................11 Analysis..................................................................................................................................................................13 Gear modifications..................................................................................................................................................14 Field methods........................................................................................................................................................14 Results/Discussion .............................................................................................. 14 Optimum size and age‐at‐capture.........................................................................................................................14 Adjusting age and growth for selectivity and retention..................................................................................15 Optimum size‐at‐capture.....................................................................................................................................15 Tiger Flathead........................................................................................................................................................16 Eastern School Whiting........................................................................................................................................17 Selectivity of Danish seine gear............................................................................................................................19 Effect of the codend cover ...................................................................................................................................19 Tiger Flathead nets ...............................................................................................................................................20 Selectivity of Danish seine gear v Eastern School Whiting nets ............................................................................................................................... 39 Interactions with Threatented, Endangered or Protected Species................................................................. 50 Observations of fish behaviour............................................................................................................................ 51 General description of the Danish seine shot and behaviour of fish in the net........................................... 51 Main bycatch species ........................................................................................................................................... 54 Gear modifications ................................................................................................................................................. 61 T90 gear ................................................................................................................................................................. 61 Catch composition................................................................................................................................................ 62 Size composition................................................................................................................................................... 68 Selectivity .............................................................................................................................................................. 68 Threatened, Endangered and Protected (TEP) Species................................................................................... 69 Discussion............................................................................................................. 72 Benefits.................................................................................................................. 74 Further Development ......................................................................................... 74 Planned Outcomes .............................................................................................. 75 Conclusion ............................................................................................................ 75 References ............................................................................................................. 77 Appendix 1: Intellectual Property................................................................... 81 Appendix 2: Staff................................................................................................ 81 Appendix 3: Tow data for all shots conducted during project.................. 82 Appendix 4: Paper published in Fisheries Science Volume 75................. 84 Selectivity of Danish seine gear vi List of Tables Table 1. Values of β1 modelled to simulate changes in codend mesh size.......................................................
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