ResearchOnline@JCU This file is part of the following reference: Cole, Andrew (2011) Energetic costs of chronic fish predation on reef-building corals. PhD thesis, James Cook University. Access to this file is available from: http://researchonline.jcu.edu.au/37611/ The author has certified to JCU that they have made a reasonable effort to gain permission and acknowledge the owner of any third party copyright material included in this document. If you believe that this is not the case, please contact [email protected] and quote http://researchonline.jcu.edu.au/37611/ The energetic costs of chronic fish predation on reef-building corals Thesis submitted by Andrew Cole BSc (Hons) September 2011 For the degree of Doctor of Philosophy in Marine Biology ARC Centre of Excellence for Coral Reef Studies and the School of Marine and Tropical Biology James Cook University Townsville, Queensland, Australia Statement of Access I, the undersigned, the author of this thesis, understand that James Cook University will make it available for use within the University Library and via the Australian Digital Thesis Network for use elsewhere. I understand that as an unpublished work this thesis has significant protection under the Copyright Act and I do not wish to put any further restrictions upon access to this thesis. 09/09/2011 (signature) (Date) ii Statement of Sources Declaration I declare that this thesis is my own work and has not been submitted in any form for another degree or diploma at my university or other institution of tertiary education. Information derived from the published or unpublished work of others has been acknowledged in the text and a list of references is given. 09/09/2011 (signature) (Date) iii Electronic copy declaration I, the undersigned, the author of this work, declare that the electronic copy of this thesis provided to the James Cook University library, is an accurate copy of the print thesis submitted, within the limits of the technology available. 09/09/2011 (signature) (Date) iv Statement on the contribution of others This thesis includes some collaborative work with Dr Morgan Pratchett, Dr Shaun Wilson, Professor Geoff Jones and Ms Rebecca Lawton. While undertaking these collaborations, I was responsible for the project design, data collection, data analysis and interpretation. My collaborators provided intellectual guidance, financial support, assistance with field work, technical instruction and editorial assistance. The chapters in this thesis have been presented as published, with exceptions for edits, updated references and standardised formatting. Financial support for the present study was provided by an Australian Research Council Grant awarded to Dr Morgan Pratchett. Additional financial assistance was provided by the Padi Foundation, the Project AWARE Foundation, the wildlife Preservation Society of Australia, Australian Geographic, the Mahonia na Dari Research and Conservation Centre and the Walindi Plantation Resort in Kimbe Bay, PNG. The ARC Centre of Excellence for Coral Reef Studies and the School of Marine and Tropical Biology, James Cook University provided laboratory space and equipment and funded several trips to conferences. Stipend support was provided by an Australian Postgraduate Award. This project was approved by the James Cook University Animal Ethics review Committee: A1327, A1306, A1328, A1443. v Acknowledgements The product of this thesis is much more than a singular effort by myself. Many people have helped, ranging from providing small but crucial comments to large investments of both time and effort. I greatly appreciate and thank you all. Foremost in my thanks is my supervisory team. First, thanks to Morgan Pratchett, whose relaxed style of supervision provided a great environment for a productive and cohesive lab group. Your guidance and generosity throughout all stages of my research development has been invaluable and the simple fact that your door was always open made my research journey all the more interesting and enjoyable. To Shaun Wilson, your insights, humor and ability to get me to think laterally about my research have been greatly appreciated, even though we were on opposite sides of the country your quick responses to emails and phone calls were a great bonus. To my final supervisor Geoff Jones, who introduced me to Kimbe Bay all those years ago; a place that I will take with me for the rest of my life. I will always be grateful to Geoff for taking a chance on me and giving me a shot at honours research and everything it has led to. Many thanks to the people of Kilu village and the staff of the Mahonia na Dari Research and Conservation Centre for making my field time a fun and productive experience. I am indebted to Michael Giru for his hospitality, friendship and keen crocodile spotting eyes. We had plenty good times. Thanks also to Jo Misman, Blazius Uma and Blazius Pondi for helping with fieldwork in Kimbe. A special thank you to the support and hospitality provided by Max Benjamin and the staff of the Walindi Plantation Resort (particularly Keat and Lowe), who not only helped with dive logistics, but also frequently fed a very hungry researcher. I will greatly miss visiting Kimbe, the people there, and all it involves. To the many friends; Rebecca Lawton, Darren Coker, Karen Chong-Seng, James Moore, Dominique McCowan, Nick Graham, Vanessa Messmer, Jarod Hines, Michael Berumen, Andy Hoey, Chris Goatley, Melanie Trapon, Colin Wen and to the many others whose names escape me, who have helped on field trips, discussed ideas and made the last few years a fun experience, this research would not have been worth doing without you all. The countless hours we spent together over the last few years have not always been productive, but at least vi they were fun. I am also very grateful to range of administrative and technical staff from JCU: Olga Bazaka, Janet Swanson, Rose-Marie Vasiljuk, Jenny Lapin, Gordon Bailey and Phil Osmond, who have all shown a great deal of patience in helping me navigate the bureaucracy of James Cook University. Finally, I am grateful for the love and support of a key group of people who helped just by being who they are. To my family who helped set me onto this track I’ve taken, and have never pressured me to get a real job. A special thank you to my partner Theresa Petray, whose love and support have made the last several years of my life so good. You were happy to spend hours in the water on field trips, proof-read drafts, listen to practice seminars and pretend to be interested in many science centric conversations. Thank you. I have also very much appreciated the funding provided by several organizations; The Wildlife Preservation Society of Australia, Padi foundation, Australian Geographic. All have enabled me the freedom to research topics which aroused my curiosity. Also to the Australian government who provided an Australian Postgraduate Award for the duration of my doctorate. Finally, and not least, to the reviewers of the papers which make up this thesis, largely a thankless task, but I am grateful for the time you have spent. Thank you. vii Abstract Interactions between predators and prey organisms are of fundamental importance to ecological communities. While the ecological impacts that grazing predators can have in terrestrial and temperate marine systems are well established, the importance of coral grazers on tropical reefs has often been overlooked. Fishes that feed from live corals (corallivores) are a conspicuous component of healthy coral reef environments. Published records document that at least 128 corallivorous fish species from 11 different families feed at least in part upon scleractinian corals, with 69 of these belonging to the family Chaetodontidae. One third of all coral-feeding fishes feed almost entirely upon corals, with more than 80% of their diet based on live coral tissue. This thesis aims to assess the energetic cost and relative importance that predation from polyp-feeding fishes has on reef-building corals by: 1) determining how the frequency and intensity of predation is dispersed both among and within common species of reef-building corals, 2) quantifying the amount of coral tissue consumed by corallivorous butterflyfishes and determining the proportion of available coral tissue biomass and potential productivity of tabular acroporid corals this consumption represents, and 3) assessing the energetic cost that chronic tissue consumption by juvenile and adult corallivores has on the growth and condition of reef-building corals. To assess how corallivore predation is dispersed both among and within coral species I used an observational study to quantify grazing rates on four common reef corals (Acropora hyacinthus, Acropora millepora, Pocillopora damicornis, and massive Porites). I also assessed the variation in predation intensity within A. hyacinthus and A. millepora by standardising grazing rates by colony surface area. Rates of grazing on individual colonies were highest (16.75 (± 0.30 SE) bites.20 minutes-1) for A. hyacinthus. Within coral species, grazing rates showed a linear increase with increasing size of the colony, however the intensity of predation showed a negative relationship with increasing colony size. Predation intensity was highest for small to medium sized colonies with a peak intensity of 1.13 (± 0.17) bites 100cm-2.20minutes- 1.colony-1 for A. hyacinthus colonies and 0.56 (± 0.09) bites 100cm-2.20 minutes-1.colony-1 for A. millepora colonies (200-600cm2). In contrast, predation intensity was lowest for both very viii small and very large colonies, with very small colonies (<200cm2) rarely consumed by corallivorous fishes. To assess the magnitude of coral tissue that is removed from the reef by corallivorous fishes I undertook aquarium based feeding trials to quantify the bite size of four prominent species of coral-feeding butterflyfishes. Sub-adult butterflyfishes (60-70mm TL, 6-11g wet weight) remove between 0.6 and 0.9g of live coral tissue per day, while larger adults (>110mm TL, 40-50g wet weight) remove between 1.5 and 3g of coral tissue each day.