A preliminary consideration of by-catch in the Marine Scalefish fishery of South Australia AJ Fowler, M Lloyd, and D Schmarr May 2009 SARDI Publication Number F2009/000097-1 SARDI Research Report Series Number 365 A preliminary consideration of by-catch in the Marine Scalefish fishery of South Australia AJ Fowler, M Lloyd, and D Schmarr May 2009 ii This publication may be cited as: Fowler AJ, Lloyd M, Schmarr D (2009). A preliminary consideration of by-catch in the Marine Scalefish fishery of South Australia. South Australian Research and Development Institute (Aquatic Sciences), Adelaide, F2009/000097-1. SARDI Research Report Series No. 365. 79 pp. South Australian Research and Development Institute SARDI Aquatic Sciences PO Box 120 HENLEY BEACH SA 5022 Telephone: (08) 8207 5400 Facsimile: (08) 8207 5406 http://www.sardi.sa.gov.au Disclaimer The authors warrant that they have taken all reasonable care in producing this report. The report has been through the SARDI Aquatic Sciences internal review process, and has been formally approved for release by the Chief Scientist. Although all reasonable efforts have been made to ensure quality, SARDI Aquatic Sciences does not warrant that the information in this report is free from errors or omissions. SARDI Aquatic Sciences 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. © 2009 SARDI Aquatic Sciences This work is copyright. Apart from any use as permitted under the Copyright Act 1968, no part may be reproduced by any process without prior written permission from the author. Author(s): A.J. Fowler, M.T. Lloyd, D. Schmarr Reviewers: Dr David Currie and Dr Michael Steer Approved by: Dr Tim Ward Signed: Date: 11 June 2009 Distribution : PIRSA Fisheries, SARDI Aquatic Sciences Library Circulation: Public Domain iii TABLE OF CONTENTS TABLE OF CONTENTS....................................................................................................... iv List of Tables............................................................................................................................ v List of figures ........................................................................................................................ viii ACKNOWLEDGEMENTS.................................................................................................... x 1. EXECUTIVE SUMMARY...................................................................................... 1 2. General Introduction ............................................................................................... 3 2.1 Background................................................................................................................. 3 2.2 Aim and objectives ..................................................................................................... 6 2.3 Definitions of terminology.......................................................................................... 6 3. General materials and methods .............................................................................. 8 3.1 Field sampling techniques........................................................................................... 8 3.2 Data Analysis............................................................................................................ 13 4. Results ..................................................................................................................... 16 4.1 Comparison of multi-species catches between gear types ........................................ 16 4.2 Multi-species catches by gear type ........................................................................... 20 4.3 Sizes and condition of discarded fish........................................................................ 46 5. General Discussion................................................................................................. 69 5.1 Species Composition of catches from main gear types............................................. 69 5.2 Conclusions............................................................................................................... 76 6. Reference list .......................................................................................................... 78 iv LIST OF TABLES Table 3.2 Summary of the number of fishing operations successfully scrutinised by observers, divided between gulfs, seasons and gear types....................................................................................................10 Table 3.3 Summary of the procedures undertaken for processing the catches taken using the different gear types, and gear sections (for haul nets). For haul nets the method of processing depended on size and composition of the catch..................................................................................................................11 Table 3.4 Condition categories to which individual or groups of fish were assigned when being discarded.................................................................................................................................................13 Table 4.1 Summary of the contribution of major taxa to the multi-species catches of commercial Marine Scalefish fishers during 122 fishing operations involving handlines, longlines and haul nets...17 Table 4.2 Summary of the species captured by the three gear types considered in this study. The table shows the major taxon, the family name, common name, scientific name and indicates whether the species was captured by the different gear types. Ce = cephalopods; cr = crustaceans; ec = echinoderms; e = elasmobranchs; t = teleosts; HL = handlines; LL = longlines; HN = haul nets; X = species caught by that gear type. ............................................................................................................17 Table 4.3 Number of handline fishing days monitored by scientific observers during the seasons of summer and winter in each of SG and GSV that were targeted at KGW, snapper or divided between both species (K&S).................................................................................................................................20 Table 4.4 Summary of results from the 12 handline fishing operations targeted at KGW in GSV. The results show the species composition, the catch and catch rates by species in numbers, and the division of catch into discard and retention rates. Catch and catch rates are shown by weight for the two primary target species.............................................................................................................................26 Table 4.5 Summary of results from the three handline fishing operations targeted at KGW and snapper, monitored in GSV. The results show the species composition, the catch and catch rates by species in numbers, and the division of catch into discard and retention rates. Catch and catch rates are shown by weight for the target species. ..................................................................................................................27 Table 4.6 Summary of results from the three handline fishing operations targeted at snapper, monitored in GSV. The results show the species composition, the catch and catch rates by species in numbers, and the division of catch into discard and retention rates. Catch and catch rates are shown by weight for the target species. ..................................................................................................................27 Table 4.7 Summary of results from the 14 handline fishing operations targeted at KGW, monitored in SG by fishery observers. The results show the species composition, the catch and catch rates by species in numbers, and the division of catch into discard and retention rates. Catch and catch rates are shown by weight for the target species...................................................................................................28 Table 4.8 Summary of results from the 11 handline fishing operations targeted at KGW and snapper, monitored in SG. The results show the species composition, the catch and catch rates by species in numbers, and the division of catch into discard and retention rates. Catch and catch rates are shown by weight for the target species. ..................................................................................................................29 Table 4.9 Summary of results from the nine handline fishing operations targeted at snapper, monitored in SG. The results show the species composition, the catch and catch rates by species in numbers, and v the division of catch into discard and retention rates. Catch and catch rates are shown by weight for the target species. .........................................................................................................................................30 Table 4.10 Number of fishing events that were monitored by scientific observers that involved the HNS 3.0 and HNF 5.0 nets, during both seasons in each of SG and GSV. ............................................31 Table 4.11 Summary of results from the 12 haul net fishing operations with the HNF 3.0 nets monitored in GSV. The results show the species composition, the catch and catch rates by species in numbers, and the division of catch into discard and retention rates. Catch and catch rates are shown by weight for two target species..................................................................................................................36