Assessment of a 35-mm square-mesh codend and composite square-mesh panel configuration in the ocean prawn-trawl fishery of northern New South Wales William G. Macbeth, Daniel D. Johnson and Charles A. Gray NSW Department of Primary Industries Cronulla Fisheries Research Centre of Excellence P.O. Box 21, Cronulla, NSW 2230, Australia Northern Rivers Catchment Management Authority Project No. IS7-8-243-06 July 2008 NSW Department of Primary Industries – Fisheries Final Report Series No. 103 ISSN 1449-9967 Assessment of a 35-mm square-mesh codend and composite square-mesh panel configuration in the ocean prawn- trawl fishery of northern New South Wales July 2008 Authors: Macbeth, W.G., Johnson, D.D. and Gray, C.A. Published By: NSW Department of Primary Industries (now incorporating NSW Fisheries) Postal Address: Cronulla Fisheries Research Centre of Excellence, PO Box 21, NSW, 2230 Internet: www.dpi.nsw.gov.au © NSW Department of Primary Industries and the Northern Rivers Catchment Management Authority This work is copyright. Except as permitted under the Copyright Act, no part of this reproduction 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. DISCLAIMER The publishers do not warrant that the information in this report is free from errors or omissions. The publishers do not accept any form of liability, be it contractual, tortuous or otherwise, for the contents of this report for any consequences arising from its use or any reliance placed on it. The information, opinions and advice contained in this report may not relate to, or be relevant to, a reader’s particular circumstance. ISSN 1449-9967 (Note: Prior to July 2004, this report series was published as the ‘NSW Fisheries Final Report Series’ with ISSN number 1440-3544) Contents iii TABLE OF CONTENTS TABLE OF CONTENTS..............................................................................................................................III LIST OF FIGURES ....................................................................................................................................... V LIST OF TABLES.........................................................................................................................................VI ACKNOWLEDGEMENTS........................................................................................................................ VII EXECUTIVE SUMMARY........................................................................................................................VIII 1. INTRODUCTION....................................................................................................................................... 11 1.1. The NSW Ocean Prawn Trawl (OPT) fishery........................................................................... 11 1.2. Addressing the issue of bycatch in the NSW OPT fishery......................................................... 15 1.3. Distribution of a 35-mm square-mesh codend to OPT operators............................................. 19 1.4. Objectives ................................................................................................................................. 19 2. MATERIALS & METHODS....................................................................................................................... 20 2.1. Study area 20 2.2. Experimental design and codends used .................................................................................... 20 2.2.1. Design of the 35-mm square-mesh codend................................................................................... 21 2.2.2. Industry codends involved in paired comparisons........................................................................ 21 2.2.3. 29-mm square-mesh codend used during school-prawn trawling................................................. 22 2.3. Data collected........................................................................................................................... 22 2.4. Catch variables for analysis ..................................................................................................... 23 2.5. Analysis of data......................................................................................................................... 24 3. RESULTS ................................................................................................................................................. 25 3.1. Cooperation and participation by trawl operators................................................................... 25 3.2. Specific paired comparisons between codends......................................................................... 25 3.3. Analysis of catches from trips targeting eastern king prawn and/or whiting........................... 26 3.3.1. 35S vs. 40D-150 codend comparison ........................................................................................... 26 3.3.1.1. Eastern king prawn........................................................................................ 27 3.3.1.2. Trawl whiting................................................................................................. 31 3.3.1.3. Other byproduct............................................................................................. 32 3.3.1.4. Discarded bycatch ......................................................................................... 36 3.3.2. 35S vs. 40D-200 codend comparison ........................................................................................... 37 3.3.2.1. Eastern king prawn........................................................................................ 38 3.3.2.2. Trawl whiting................................................................................................. 39 3.3.2.3. Other byproduct............................................................................................. 40 3.3.2.4. Discarded bycatch ......................................................................................... 40 3.3.3. 35S vs. 45D-150 codend comparison ........................................................................................... 40 3.3.3.1. Eastern king prawn........................................................................................ 41 3.3.3.2. Trawl whiting................................................................................................. 41 3.3.3.3. Other byproduct............................................................................................. 44 3.3.3.4. Discarded bycatch ......................................................................................... 44 3.4. Analysis of catches from trips targeting school prawn............................................................. 45 3.4.1. 35S vs. 40D-200 codend comparison ........................................................................................... 45 3.4.1.1. School prawn................................................................................................. 45 3.4.1.2. Trawl whiting and other byproduct ............................................................... 46 3.4.1.3. Discarded bycatch ......................................................................................... 48 3.4.1.4. 29-mm square-mesh codend .......................................................................... 48 3.5. Analysis of catches from an industry-developed square-mesh codend design ......................... 49 3.6. Interactions with threatened, protected and other species of interest ...................................... 52 3.6.1. Threatened and/or protected fish species...................................................................................... 52 3.6.2. Marine reptiles, marine mammals and seabirds............................................................................ 52 3.6.3. Sharks and rays............................................................................................................................. 52 3.6.4. Non-target species of particular commercial and/or recreational importance............................... 53 Square-mesh codends in the northern NSW OPT fishery (Macbeth et al.) NRCMA Project IS7-8-243-06 iv Contents 4. DISCUSSION .............................................................................................................................................54 4.1. General overview ......................................................................................................................54 4.2. Trawling for eastern king prawns .............................................................................................54 4.3. Trawling for school prawns ......................................................................................................57 4.4. Trawling for whiting..................................................................................................................57 4.5. Interactions with threatened, protected and other species of interest.......................................58 4.6. Fate of discarded bycatch vs. fate of escapees during trawling................................................58 5. CONCLUSIONS AND RECOMMENDATIONS...............................................................................................59 6. REFERENCES ...........................................................................................................................................60