Research to develop and manage the sea urchin fisheries of NSW and eastern Victoria D.G. Worthington and C.Blount Cronulla Fisheries Centre, P.O. Box 21, Cronulla, NSW, 2230 Australia FRDC Project No. 1999/128 October 2003 NSW Fisheries Final Report Series No. 56 ISSN 1440-3544 Research to develop and manage the sea urchin fisheries of NSW and eastern Victoria D.G. Worthington and C.Blount Cronulla Fisheries Centre, P.O. Box 21, Cronulla, NSW, 2230 Australia FRDC Project No. 1999/128 October 2003 NSW Fisheries Final Report Series No. 56 ISSN 1440-3544 Research to develop and manage the sea urchin fisheries of NSW and eastern Victoria October 2003 Authors: D.G. Worthington and C.Blount Published By: NSW Fisheries Postal Address: PO Box 21, Cronulla NSW 2230 Internet: www.fisheries.nsw.gov.au NSW Fisheries This work is copyright. Except as permitted under the Copyright Act (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. DISCLAIMER Every attempt has been made to provide accurate information in this document. However, no liability attaches to NSW Fisheries or to any organisation or individual concerned with the supply of information or the preparation of this document for any consequences of using the information contained in this document. ISSN 1440-3544 Contents i TABLE OF CONTENTS TABLE OF CONTENTS ................................................................................................................................ I LIST OF TABLES........................................................................................................................................ III LIST OF FIGURES...................................................................................................................................... IV ACKNOWLEDGEMENTS ......................................................................................................................... VI NON-TECHNICAL SUMMARY...............................................................................................................VII 1. INTRODUCTION...................................................................................................................................... 1 1.1. Background.................................................................................................................................. 1 1.2. Need ............................................................................................................................................. 2 1.3. Objectives..................................................................................................................................... 2 2. DEVELOPMENT OF METHODS TO ASSESS STOCKS OF SEA URCHIN IN NSW AND EASTERN VICTORIA ..... 3 2.1. General introduction.................................................................................................................... 3 2.2. Assessment of stocks of red sea urchins in NSW.......................................................................... 4 2.2.1. Introduction...........................................................................................................................................4 2.2.2. Methods.................................................................................................................................................4 2.2.2.1. Commercial catch ..........................................................................................................................4 2.2.2.2. Density and biomass ......................................................................................................................5 2.2.2.3. Depletion caused by fishing...........................................................................................................6 2.2.3. Results...................................................................................................................................................6 2.2.3.1. Commercial catch ..........................................................................................................................6 2.2.3.2. Density and biomass ......................................................................................................................9 2.2.3.3. Depletion caused by fishing.........................................................................................................11 2.2.4. Discussion ...........................................................................................................................................13 2.3. Assessment of stocks of purple sea urchins in NSW................................................................... 14 2.3.1. Introduction.........................................................................................................................................14 2.3.2. Methods...............................................................................................................................................14 2.3.3. Results.................................................................................................................................................16 2.3.4. Discussion ...........................................................................................................................................21 2.4. Assessment of stocks of sea urchins in Port Phillip Bay and eastern Victoria .......................... 23 2.4.1. Introduction.........................................................................................................................................23 2.4.2. Methods...............................................................................................................................................23 2.4.2.1. Port Phillip Bay............................................................................................................................23 2.4.2.2. Eastern Victoria ...........................................................................................................................25 2.4.2.3. Habitat area and biomass .............................................................................................................25 2.4.3. Results.................................................................................................................................................26 2.4.3.1. Port Phillip Bay............................................................................................................................26 2.4.3.2. Eastern Victoria ...........................................................................................................................30 2.4.4. Discussion ...........................................................................................................................................35 3. DEVELOPMENT OF METHODS TO ENHANCE THE ROE OF SEA URCHINS.................................................. 37 3.1. General introduction.................................................................................................................. 37 3.2. Enhancing the roe of the purple sea urchin by reducing density ............................................... 38 3.2.1. Introduction.........................................................................................................................................38 3.2.2. Methods...............................................................................................................................................38 3.2.2.1. Experimental design and sites sampled........................................................................................38 Small-scale .................................................................................................................................................38 Medium-scale.............................................................................................................................................39 Large-scale .................................................................................................................................................39 3.2.2.2. Effects of density on sea urchins..................................................................................................39 Small-scale .................................................................................................................................................39 Medium-scale.............................................................................................................................................39 Large-scale .................................................................................................................................................41 3.2.2.3. Effects of density on benthic assemblages...................................................................................41 3.2.3. Results.................................................................................................................................................42 Sea urchin fisheries of NSW and eastern Victoria, Blount & Worthington FRDC Project No. 99/128 ii Contents 3.2.3.1. Effects of density on sea urchins..................................................................................................42 3.2.3.2. Effects of density on benthic assemblages ...................................................................................48