Marine Ecosystems Australian sea lion investigations: 2018-19 S.D. Goldsworthy, J. Hodgson and D. Holman SARDI Publication No. F2020/000052-1 SARDI Research Report Series No. 1051 SARDI Aquatics Sciences PO Box 120 Henley Beach SA 5022 March 2020 Report to the Department for Environment and Water Goldsworthy, S.D., Hodgson, J., and Holman, D. (2020) Australian sea lions investigations 2018-19 Australian sea lion investigations: 2018-19 Report to the Department for Environment and Water S.D. Goldsworthy, J. Hodgson and D. Holman SARDI Publication No. F2020/000052-1 SARDI Research Report Series No. 1051 March 2020 II Goldsworthy, S.D., Hodgson, J., and Holman, D. (2020) Australian sea lions investigations 2018-19 This publication may be cited as: Goldsworthy, S.D., Hodgson, J. and Holman, D. (2020). Australian sea lion investigations: 2018-19. South Australian Research and Development Institute (Aquatic Sciences), Adelaide. SARDI Publication No. F2020/000052-1. SARDI Research Report Series No. 1051. 88pp. South Australian Research and Development Institute SARDI Aquatic Sciences 2 Hamra Avenue West Beach SA 5024 Telephone: (08) 8207 5400 Facsimile: (08) 8207 5415 http://www.pir.sa.gov.au/research DISCLAIMER The authors warrant that they have taken all reasonable care in producing this report. The report has been through the SARDI internal review process, and has been formally approved for release by the Research Director, Aquatic Sciences. Although all reasonable efforts have been made to ensure quality, SARDI does not warrant that the information in this report is free from errors or omissions. SARDI and its employees do not warrant or make any representation regarding the use, or results of the use, of the information contained herein as regards to its correctness, accuracy, reliability and currency or otherwise. SARDI and its employees expressly disclaim all liability or responsibility to any person using the information or advice. Use of the information and data contained in this report is at the user’s sole risk. If users rely on the information they are responsible for ensuring by independent verification its accuracy, currency or completeness. The SARDI Report Series is an Administrative Report Series which has not been reviewed outside the department and is not considered peer- reviewed literature. Material presented in these Administrative Reports may later be published in formal peer-reviewed scientific literature. © 2020 SARDI This work is copyright. Apart from any use as permitted under the Copyright Act 1968 (Cth), no part may be reproduced by any process, electronic or otherwise, without the specific written permission of the copyright owner. Neither may information be stored electronically in any form whatsoever without such permission. SARDI Publication No. F2020/000052-1 SARDI Research Report Series No. 1051 Author(s): S.D. Goldsworthy, J. Hodgson and D. Holman Reviewer(s): Marty Deveney and Fred Bailleul Approved by: A/Prof T Ward Science Leader – Marine Ecosystems Signed: Date: 4 March 2020 Distribution: DEW, SAASC Library, Parliamentary Library, State Library and National Library Circulation: Public Domain III Goldsworthy, S.D., Hodgson, J., and Holman, D. (2020) Australian sea lions investigations 2018-19 TABLE OF CONTENTS ACKNOWLEDGEMENTS .......................................................................................................... XII EXECUTIVE SUMMARY .............................................................................................................. 1 1. INTRODUCTION ................................................................................................................... 3 1.1. Background .................................................................................................................... 3 1.2. Objectives ....................................................................................................................... 4 2. MONITORING AUSTRALIAN SEA LION COLONIES OFF WESTERN AND LOWER EYRE PENINSULA .................................................................................................................................. 5 2.1. Introduction ..................................................................................................................... 5 2.2. Methods .......................................................................................................................... 5 2.3. Results ............................................................................................................................ 8 2.4. Discussion .................................................................................................................... 32 3. POPULATION VIABILITY ANALYSIS OF AUSTRALIAN SEA LION .................................. 33 3.1. Introduction ................................................................................................................... 33 3.2. Methods ........................................................................................................................ 34 3.3. Results .......................................................................................................................... 38 3.4. Discussion .................................................................................................................... 55 4. SUITABILITY OF DRONE IMAGEY TO ESTIMATE THE BODY SIZE AND CONDITION IN AUSTRALIAN SEA LIONS ......................................................................................................... 57 4.1. Introduction ................................................................................................................... 57 4.2. Materials and methods ................................................................................................. 60 4.3. Results .......................................................................................................................... 65 4.4. Discussion .................................................................................................................... 66 REFERENCES ........................................................................................................................... 82 IV Goldsworthy, S.D., Hodgson, J., and Holman, D. (2020) Australian sea lions investigations 2018-19 LIST OF FIGURES Figure 2.1. The location of Australian sea lion (ASL) breeding sites in South Australia, including those surveyed as part of this study. ............................................................................................ 8 Figure 2.2. Comparison of trend in the abundance of Australian sea lion pups at Olive Island between 2003 and 2019, based on four pup abundance indices: CPP = cumulative pup production; M-R = maximum mark-recapture Petersen estimate (plus cumulative dead pups); Count 1 = sum of the maximum count of live pups and cumulative dead pups; Count 2 = sum of the cumulative number of marked pups, the maximum number of unmarked pups surveyed and cumulative dead (unmarked) pups. An exponential curve is fitted to each time-series for the period between 2006 and 2017, where survey data using all four methods are comparable. ............... 12 Figure 2.3. Trends in the abundance of Australian sea lion pups at Nicolas Baudin Island between 2002 and 2019. Pup abundance is based on ground survey counts of pups, with Comparable surveys (filled circles, and Questionable surveys (grey squares) indicated (see Table 2.5). An exponential curve is fitted to the comparable survey time-series data. ...................................... 15 Figure 2.4. Trends in the abundance of Australian sea lion pups at West Waldegrave Island between 2002 and 2019. Pup abundance is based on ground survey counts of pups, with Comparable surveys (filled circles), and Questionable surveys (grey squares) indicated (see Table 2.6). An exponential curve is fitted to the comparable survey time-series data. ............... 17 Figure 2.5. Trends in the abundance of Australian sea lion pups at Rocky (South) Island between 2011 and 2019. Pup abundance is based on ground survey counts of pups. An exponential curve is fitted to the comparable time-series data ................................................................................ 19 Figure 2.6. Trends in the abundance of Australian sea lion pups at the Four Hummocks Islands between 1996 and 2019. Pup abundance is based on ground survey counts of pups, with comparable survey (filled circles), and questionable surveys (grey squares) indicated (see Table 2.8). An exponential curve is fitted to the comparable survey time-series data. ......................... 21 Figure 2.7. Camera trap installed on West Waldegrave Island (top-left), with a range of images of black pup with mother (bottom images),and brown pups (middle and top-right). ................... 27 Figure 2.8. Camera trap installed on Rocky (North) Island (top-left), with assorted images of brown and moulted pups, with some females and juveniles. ...................................................... 28 Figure 2.9. Camera trap installed on Liguanea Island (top-left), with assorted images: juvenile with Cape Barron goose (top-right), brown pup and moulted pup (middle), and adult male (bottom left). The final image uploaded from the camera (bottom-right) may be obscured by a sea lion which potentially disconnect the external power cable to the camera. ....................................... 29 V Goldsworthy, S.D., Hodgson, J., and Holman, D. (2020) Australian sea lions investigations