Could harvest from abalone stocks be increased through better management of the size limit/quota interaction? Hugh Jones, David Tarbath, Caleb Gardner Project No. 2009/746 04 March 2015 This project was conducted by University of Tasmania – Institute for Marine and Antarctic Studies ISBN: 978-1-86295-793-0 Copyright, 2014: The Seafood CRC Company Ltd, the Fisheries Research and Development Corporation and University of Tasmania – Institute for Marine and Antarctic Studies. 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. The Australian Seafood CRC is established and supported under the Australian Government’s Cooperative Research Centres Program. Other investors in the CRC are the Fisheries Research and Development Corporation, Seafood CRC company members, and supporting participants. Office Mark Oliphant Building, Laffer Drive, Bedford Park SA 5042 Postal Box 26, Mark Oliphant Building, Laffer Drive, Bedford Park SA 5042 Tollfree 1300 732 213 Phone 08 8201 7650 Facsimile 08 8201 7659 Website www.seafoodcrc.com ABN 51 126 074 048 Important Notice Although the Australian Seafood CRC has taken all reasonable care in preparing this report, neither the Seafood CRC nor its officers accept any liability from the interpretation or use of the information set out in this document. Information contained in this document is subject to change without notice. Seafood CRC 2009-746 Final Report Contents NON-TECHNICAL SUMMARY ............................................................................................................ 1 1. INTRODUCTION OR BACKGROUND ........................................................................ 4 1.1 FORMAT ............................................................................................................................... 4 1.2 INTRODUCTION ..................................................................................................................... 5 1.3 NEED .................................................................................................................................... 6 1.4 OBJECTIVES .......................................................................................................................... 7 1.5 REFERENCES ........................................................................................................................ 7 2. QUANTIFYING DENSITY-DEPENDENT EFFECTS ON WILD BLACKLIP ABALONE GROWTH AND ITS IMPACT ON MEAT QUALITY. ................................................... 9 2.1 INTRODUCTION ..................................................................................................................... 9 2.2 METHOD ............................................................................................................................. 10 2.2.1 Comparison of biological parameters ................................................................................ 12 Growth rate .................................................................................................................................. 12 Size at maturity ............................................................................................................................ 14 2.2.2 Abalone quality ................................................................................................................. 15 2.3 RESULTS ............................................................................................................................. 15 2.3.1 Density reduction ............................................................................................................... 15 2.3.2 Comparison of growth rate parameters .............................................................................. 16 Growth rate: ................................................................................................................................. 16 Size at maturity: ........................................................................................................................... 21 2.3.3 Abalone Quality ................................................................................................................. 22 2.4 DISCUSSION ........................................................................................................................ 22 2.5 REFERENCES ...................................................................................................................... 24 3. DEVELOPING A STATISTICAL TOOL FOR THE DETERMINATION OF SHELL GRADE ...................................................................................................................................... 27 3.1 INTRODUCTION ................................................................................................................... 27 3.2 METHOD ............................................................................................................................. 28 3.2.1 Field operations ................................................................................................................. 28 3.2.2 Tasmanian Seafoods grade classification .......................................................................... 28 3.2.3 Measurement of shell dimensions and allometric growth ................................................. 29 3.2.4 Testing TSF shell grade ..................................................................................................... 31 3.2.5 Transformation of shell dimensions to remove scaling effects .......................................... 31 3.2.6 Quantification of TSF shell grade by shell dimensions ..................................................... 31 3.3 RESULTS ............................................................................................................................. 32 3.3.1 Measurement of shell dimensions, ratios and allometric growth ....................................... 32 3.3.2 Testing of TSF shell grade ................................................................................................. 32 3.3.3 Quantification of TSF shell grade by shell dimensions. .................................................... 33 3.3.4 Binomial model of shell grade ........................................................................................... 34 3.3.5 Allometric shape model ..................................................................................................... 36 3.4 DISCUSSION ........................................................................................................................ 39 3.5 REFERENCES ...................................................................................................................... 42 4. THE USE OF LENGTH-BASED MODELS TO TEST THE ADEQUACY OF SHELL AGE PERFORMANCE MEASURES..................................................................................... 44 4.1 INTRODUCTION ................................................................................................................... 44 4.2 METHOD ............................................................................................................................. 45 4.2.1 Site selection ...................................................................................................................... 45 4.2.2 Statistical analysis ............................................................................................................. 47 4.2.3 Size at maturity .................................................................................................................. 47 4.2.4 Transformation of shell dimensions to remove scaling effects. ......................................... 47 4.2.5 Variation in shell shape with size and location – Binomial model .................................... 47 4.2.6 Variation in shell shape with size and location – Allometric shape model........................ 48 4.2.7 Theoretical growth rate estimates and LMLct .................................................................... 48 Page 1 Seafood CRC 2009-746 Final Report 4.3 RESULTS ............................................................................................................................. 49 4.3.1 Size at maturity .................................................................................................................. 49 4.3.2 Variation in shell shape with size and location – Binomial model .................................... 50 4.3.3 Variation in shell shape with size and location – allometric shape model ......................... 51 4.3.4 Theoretical SL for harvest at slow growth regions defined by shape (SLty). ..................... 55 4.3.5 Theoretical growth rate estimates and LMLct .................................................................... 57 4.4 DISCUSSION ........................................................................................................................ 58 4.5 SUMMARY .......................................................................................................................... 61 4.6 REFERENCES ...................................................................................................................... 61 5. CONCLUSION ...............................................................................................................