Sea cucumber fisheries in the Kingdom of Tonga: regeneration biology, ecology, and environmental chemistry Hannah Charan-Dixon A thesis submitted in partial fulfilment of a Master of Science School of Biological Sciences University of Canterbury 1 This thesis is dedicated to my late Great Grandmother - an incredible woman whose memory continues to inspire me each and every day. 2 Acknowledgements I would like to thank my supervisors; Dr. Sharyn Goldstien, Dr. Chris Glover, and Dr. Sally Gaw for all of their hard work, advice, and support. This has been an incredible learning opportunity which would not have been possible without the three of you. In addition, I would like to thank Beth Vanderhaven, the most excellent field and laboratory assistant anyone could ask for; your enthusiasm, friendship, and help in all matters big and small have been critical throughout the duration of this journey. I would also like to express my very sincere thanks to the New Zealand Federation of Graduate Women and the Ministry of Foreign Affairs and Trade who provided the funding support essential for this research. In addition, a very special thank you to the Tonga Fisheries Division, in particular to Dr. Siola’a Malimali, Dr. Tuikolongahau Halafihi, and Tonga Latu Tuiano for making this research possible and for sharing your considerable knowledge with me. To the staff at Noa’s Guesthouse; your hospitality, friendship, and kindness made for such a wonderful experience filled with great memories. To the University of Canterbury branch; Jonathan Hill, Jan McKenzie, Dr. Bill Davison, Renny Bishop, Alan Woods, The Physiology Research Group, The Environmental Chemistry Group, The International Waters Group, and the inhabitants of my office – you’ve all been fundamental to the success of this project and you have all taught me so much. In particular, Travis Foster, thank you for your help, for providing all manner of discussion topics, and for being so supportive at every turn. Lastly, thank you to my wonderful family for your positivity, endless support and advice, and for guiding me on this journey. You have been the best support crew anyone could ever dream of. I would also like to thank my partner and my friends for their understanding, patience, and ongoing support. In particular, Isis Metcalfe, thank you for your thoughtfulness, the adventures, and your outstanding sense of humour. 3 List of Contents Acknowledgements ............................................................................................................................. 3 List of Figures ..................................................................................................................................... 6 List of Tables ...................................................................................................................................... 8 Abstract ............................................................................................................................................... 9 1. General introduction ..................................................................................................................... 10 1. 1. Commercial export fishery: Tonga ....................................................................................... 12 1. 2. Traditional fishery; Tonga .................................................................................................... 13 1. 3. Regeneration ......................................................................................................................... 14 1. 4. Trace metals as pollutants in the marine environment .......................................................... 15 1. 5. Thesis: Aims and Hypotheses ............................................................................................... 17 2. Regeneration Biology: The Effects of a Traditional Fishing Technique on the Physiology and Biochemistry of Stichopus horrens ................................................................................................... 19 2. 1. Introduction ........................................................................................................................... 19 2. 2. Methods................................................................................................................................. 22 2. 2. 1. Experimental set-up ...................................................................................................... 23 2. 2. 2. Respirometry ................................................................................................................. 25 2. 2. 3 Ammonia Excretion Rate .............................................................................................. 28 2. 2. 4. O:N ................................................................................................................................ 29 2. 2. 5. Biochemistry ................................................................................................................. 30 2. 2. 6. Determination of regeneration ...................................................................................... 33 2. 2. 7. Data analysis ................................................................................................................. 34 2. 3. Results ................................................................................................................................... 36 2. 3. 1. Internal Organ Regeneration ......................................................................................... 36 2. 3. 2. Asexual reproduction .................................................................................................... 39 2. 3. 3. Physiology ..................................................................................................................... 40 2. 3. 4. Biochemistry ................................................................................................................. 47 2. 3. 5. O:N ................................................................................................................................ 50 2. 4. Discussion ............................................................................................................................. 50 2. 4. 1. Internal organ regeneration ........................................................................................... 50 2. 4. 2. Respiratory tree regeneration ........................................................................................ 53 2. 4. 3. Gonad regeneration and development ........................................................................... 54 2. 4. 4. Asexual reproduction .................................................................................................... 54 2. 4. 5. Physiology: Oxygen consumption rate and ammonia excretion rate ............................ 56 2. 4. 6. Biochemistry: Glycogen, O:N, Glucose, and Lactate ................................................... 58 2. 4. 7. Summary ....................................................................................................................... 60 3. The Ecological Distribution and Diversity of holothuroids of the Tongatapu Island group ......... 62 3.1 Introduction ........................................................................................................................... 62 3. 1. 2. Sea cucumber ecology .................................................................................................. 62 3. 1. 3. Ecological surveys/stock assessments........................................................................... 64 3. 2. Methods................................................................................................................................. 66 3. 2. 1. Site identification .......................................................................................................... 66 3. 2. 2. Ecological sampling ...................................................................................................... 67 3. 2. 3. Data analysis ................................................................................................................. 71 3. 2. 4. Species richness ............................................................................................................ 73 3. 2. 5. Shannon-Wiener diversity index ................................................................................... 73 3. 2. 6. Evenness ....................................................................................................................... 74 3. 3. Results ................................................................................................................................... 74 3. 3. 1. Differences in sea cucumber composition between sites – ‘Seagrass’ habitat .................. 74 3. 3. 2. Habitat composition – ‘seagrass’ .................................................................................. 77 3. 3. 3. Generalised linear models; effects of habitat variables on Stichopus horrens abundance 79 3. 3. 4. Differences between time of day, stations, and years – Stichopus horrens ...................... 81 3. 3. 5. Species richness ............................................................................................................ 84 4 3. 3. 6. Species diversity; Shannon-Wiener index ........................................................................ 85 3. 3. 7. Juvenile Holothuria leucospilota aggregration – Atata Station 2 ................................