Assessment of the implications of interactions between fur seals and sea lions and the southern rock lobster and gillnet sector of the Southern and Eastern Scalefish and Shark Fishery (SESSF) in South Australia Photo: Nick Gales Final Report to the Fisheries Research and Development Corporation Simon D. Goldsworthy, Derek Hamer and Brad Page FRDC PROJECT NUMBER: 2005/077 TABLE OF CONTENTS 2 Assessment of the implications of interactions between fur seals and sea lions and the southern rock lobster and gillnet sector of the Southern and Eastern Scalefish and Shark Fishery (SESSF) in South Australia Simon D. Goldsworthy, Derek Hamer and Brad Page South Australian Research And Development Institute SARDI Aquatic Sciences 2 Hamra Avenue West Beach SA 5024 Telephone: (08) 8207 5400 Facsimile: (08) 8207 5481 http://www.sardi.sa.gov.au/ Disclaimer Copyright Fisheries Research and Development Corporation and South Australian Research and Development Institute 2007. This work is copyright. Except as permitted under the Copyright Act 1968 (Commonwealth), 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 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. Printed in Adelaide, August 2007 SARDI Aquatic Sciences Publication Number F2007/000711-1 SARDI Research Report Series Number 225 ISBN Number: 978 0 7308 5372 5 Authors: Simon D. Goldsworthy, Derek Hamer and Brad Page Reviewers: Dr Scoresby Shepherd, Dr Adrian Linnane, Dr Peter Shaughnessy Approved by: Dr. Tim Ward Signed: Date: 9 August 2007 Circulation: Public Domain TABLE OF CONTENTS 3 1 NON TECHNICAL SUMMARY ............................................................................. 5 2 BACKGROUND .................................................................................................... 8 SOUTHERN ROCK LOBSTER FISHERY .......................................................................................9 ESD Assessment - SA Rock lobster fishery.................................................................10 GILLNET SECTOR SOUTHERN AND EASTERN SCALEFISH AND SHARK FISHERY (SESSF).........11 ESD assessment – gillnet sector of the SESSF...........................................................12 BACKGROUND TO SEAL SPECIES ...........................................................................................13 Australian sea lion (ASL)..............................................................................................13 New Zealand fur seals (NZFS).....................................................................................15 3 NEED .................................................................................................................. 19 4 OBJECTIVES...................................................................................................... 20 5 REPORT FORMAT ............................................................................................. 20 6 SYNTHESISE AND REVIEW THE FISHERY LOGBOOKS FOR THE SA ROCK LOBSTER AND GILLNET SECTOR SESSF FISHERIES FOR REPORTS OF INTERACTIONS WITH SEALS........................................................................... 21 INTRODUCTION.....................................................................................................................21 AFMA LOGBOOK RECORDS FOR THE SOUTHERN AND EASTERN SCALEFISH AND SHARK FISHERY (SESSF) SHARK GILL-NET SECTOR .........................................................................23 LOGBOOK RECORDS FOR THE SOUTH AUSTRALIAN ROCK LOBSTER FISHERY (SARLF)............25 7 RISK-ASSESSMENT OF SEAL INTERACTIONS IN THE SOUTH AUSTRALIAN ROCK LOBSTER AND GILL-NET SECTOR OF THE SOUTHERN AND EASTERN SCALEFISH AND SHARK FISHERY ............................................... 26 INTRODUCTION.....................................................................................................................26 METHODS ............................................................................................................................26 Seal distribution, population size and population viability analysis ..............................26 Location of breeding sites....................................................................................26 Population estimates ...........................................................................................27 Leslie matrix and population model development................................................28 Population viability analysis (PVA) ......................................................................33 Seal foraging models and spatial distribution of foraging effort ...................................34 Spatial and temporal overlap in fishery effort and seal foraging effort .........................38 RESULTS .............................................................................................................................41 Population distribution and size ...................................................................................41 Distribution of seal foraging effort ................................................................................42 Distribution of fishing effort...........................................................................................42 Gill-net sector of the SESSF................................................................................42 SA Rock lobster fishery (SARLF) ........................................................................43 Spatial overlap in fishing and seal foraging effort ........................................................46 Australian sea lions..............................................................................................46 New Zealand fur seals .........................................................................................48 Population viability analysis .........................................................................................51 New Zealand fur seals .........................................................................................54 Fishery bycatch scenarios............................................................................................56 Australian sea lion - gill-net sector SESSF ..........................................................56 Australian sea lion and the SA Rock lobster fishery ............................................63 New Zealand fur seal and the gillnet SESSF.......................................................64 New Zealand fur seal and the SARLF Fishery ....................................................66 TABLE OF CONTENTS 4 DISCUSSION.........................................................................................................................74 Study limitations...........................................................................................................74 Seal population data ............................................................................................74 Foraging models and fishing effort ......................................................................75 Assessment of risks to Australian sea lions .................................................................76 PVA assessment of subpopulations ....................................................................76 Evaluating the risk posed by each fishery ...........................................................77 Assessment of risks to New Zealand fur seals ............................................................80 PVA assessment of subpopulations ....................................................................80 Evaluating the risk posed by each fishery ...........................................................80 Potential to develop risk management tools ................................................................81 CONCLUSIONS AND RECOMMENDATIONS ...............................................................................82 8 REVIEW OF THE MANAGEMENT RESPONSES RELATED TO SEAL-FISHERY INTERACTIONS.................................................................................................134 Bycatch quotas or limits .............................................................................................135 Spatial closures..........................................................................................................137 Modification of fishing gear ........................................................................................139 Seal Exclusion Devices for lobster pots.............................................................139 Acoustic deterrents and harassment devices ....................................................140 Modification of fishing practices .................................................................................141 Concluding remarks ...................................................................................................143 9 RECOMMENDATIONS FOR FURTHER RESEARCH ......................................145 10 BENEFITS AND ADOPTION .............................................................................149 11 FURTHER DEVELOPMENT ..............................................................................150