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AN EVALUATION OF CORAL REEF FISH COMMUNITIES IN SOUTH AFRICAN MARINE PROTECTED AREAS by CAMILLA FLOROS A thesis submitted in fulfilment of the requirements for the degree of DOCTOR OF PHILOSOPHY in the School of Biological & Conservation Sciences, University of KwaZulu-Natal, Durban 2010 SUPERVISORS: PROF. M.H. SCHLEYER DR L. CELLIERS ABSTRACT Differences in coral reef fish assemblages were investigated on six South African and one southern Mozambican reef under varying management regimes. All of the South African reefs fall within marine protected areas (MPA) but are zoned for differing types and intensities of human activity. Reefs where no human activities are allowed were termed Sanctuaries, while those on which restricted fishing and SCUBA diving are permitted were termed Protected. The reef in southern Mozambique is subjected to unrestricted fishing and SCUBA diving and was consequently termed Open. This study consists of two parts. The first dealt with a community assessment which investigated and provided baseline data on the trophic structure, density, and species diversity of fish assemblages on each of the seven study reefs. The objective was to compare the aforementioned metrics between reefs and thereafter compare them between the different protection zones. The second part of this study focused on assessing the impacts of human activities using 25 fish indicator species. These species were selected a priori based on their ecological importance and sensitivity to human activity (fishing and diving). The selection process was then guided by the results of the community assessment. The objective was to use these species as indicators of recreational diving and fishing pressure in the different protection zones. Density, biomass and size frequency analyses comprised the primary metrics in this assessment. Randomly stratified underwater visual censuses (UVC) were used to collect the fish data and these were conducted on reefs inhabited by a coral community considered to be the core community on South Africa’s reefs in terms of biodiversity and coral cover. The fish community assessment consisted of timed counts in which all non-cryptic fish species were quantified. Indicator species counts employed the point count technique with a radius of 10 m. An average of 11 community counts and an average of 62 point counts were conducted per reef. Various environmental variables and habitat characteritics were recorded during the UVCs. Multivariate analysis of the fish assemblages indicated that the fish community structure differed significantly according to reef protection status. Sanctuary reefs were significantly different from the Open reef in Southern Mozambique. Mean fish abundance was highest on Sanctuary reefs and lowest on the Open reef. In terms of overall species diversity, a total of 284 species belonging to 50 families were recorded, this being comparable to other reefs in the WIO region. Six families i contributed more than 50% towards the fish community composition: Labridae, Acanthuridae, Chaetodontidae, Lutjanidae, Pomacentridae and Serranidae. All predator categories were well represented on Sanctuary reefs, while top-level predators were scarce on the High-Diving and the Open reef. Generalised linear model (GLM) regression analysis indicated that human activities were significant variables in accounting for the variance in fish community structure. The total fish abundance and biomass of the selected indicator species were significantly higher in Sanctuary zones and lowest in the Open zone. In addition, Sanctuary zones were characterised by high numbers of large predators, while non-Sanctuary zones were characterised by higher abundances of prey species. Target species were also larger and more abundant in Sanctuary zones. The data revealed that recreational fishing and high diving intensity may be influencing the fish community structure on southern African coral reefs, which was confirmed by GLM regression analysis. Long-term monitoring of these fish communities is recommended to confirm the trends observed in this data set. ii PREFACE The experimental work described in this thesis was carried out at the Oceanographic Research Institute in the School of Biological Science, University of KwaZulu-Natal, Durban from March 2007 to May 2010, under the supervision of Professor Michael H. Schleyer and under the co- supervision of Dr Louis Celliers. These studies represent original work by the author and have not otherwise been submitted in any form for any degree or diploma to any tertiary institution. Where use has been made of the work of others it is duly acknowledged in the text. Signed ______________________________ Date __________________________ iii ACKNOWLEDGMENTS I would like to acknowledge many people who helped me start and finish my PhD. I will start with the people who were there from the beginning, when I first knew what I wanted to be on the white beaches of S ta Carolina. To my family, Panagiotis, Angela and Olivia Floros, thank you for never doubting that my marine path was the right one, for your intense love and support, and for offering to help before I even had to ask. What more could a daughter and sister ask for. I will be forever grateful. To Kristina Clark, the adopted member of the Floros family, thank you for your friendship and your invaluable management knowledge. To my husband and soul mate, Sarel Coetzer. I could not have completed the last three years without your unfailing love and support in every way. Your commitment to me and willingness to share my passion for anything marine cements my love for you. Thank you for being by my side. I would like to express sincere gratitude to my supervisors, Professor Michael Schleyer and Dr Louis Celliers for their guidance. Mike, thank you for the opportunities you afforded me at the Oceanographic Research Institute, and for your kindness. Your support has meant a great deal to me over the past three years. Louis, thank you for agreeing to be my co-supervisor at such a late stage. Your comments and suggestions motivate me to think ‘outside the box.’ I would also like to acknowledge Professor Dave Schoeman for his contributions towards this thesis. I am indebted to many people at the Oceanographic Research Institute. To the Director, Rudy van der Elst, thank you for the opportunity to study at ORI. To the many people who helped with fieldwork, sometimes in perfect weather, but a few times, when it was touch-and-go. Thank you to the skippers for always bringing us home safely, especially after the long journeys to Rabbit Rock in 3 m swell. Special thanks to Jade Maggs for gathering all my fish community data and for shielding me from those pesky potato bass. I am grateful to a number of people who jumped in at the last minute when I needed extra hands in the field; Bruce Mann, Sean Fennessy and Erica Steyn. Sincere thanks goes to Grace Samuriwo, the ORI librarian, who was incredibly efficient in sourcing my article requests. Thanks also to the admin staff, in particular Paul Zammit, who organised and helped print my thesis. A big thank you to Denis Rouillard who, very patiently, constructed the reef maps for this thesis. Lastly, thank you to all my friends at ORI for the laughs, ideas and discussions. It is such a pleasure to work with you all. iv This project was carried out with financial and logistical support from numerous sources. The fieldwork was funded by the National Research Foundation and the South African Association for Marine Biological Research. The NRF also granted me a free-standing bursary. Ezemvelo KZN Wildlife and iSimangaliso Wetland Park provided logistical support for the project and the Mazda Wildlife Fund sponsored a 4x4 vehicle for coral research. Colin Ogden of Amoray Diving provided airfills during the fieldtrips. Angie Gullan of Dolphin EnCountours was very generous in providing a base during the southern Mozambique fieldtrips. Many of the photographs used in the monitoring protocol are courtesy of Dennis and Sally Polack. v TABLE OF CONTENTS Abstract ................................................................................................................................................ i Preface................................................................................................................................................iii Acknowledgments.............................................................................................................................. iv Table of contents................................................................................................................................ vi CHAPTER 1 General Introduction ....................................................................................................................... 1 CHAPTER 2 Study site...................................................................................................................................... 15 2.1 Study site description .......................................................................................................... 15 2.1.2 Climate ............................................................................................................................. 16 2.1.3 Oceanography................................................................................................................... 16 2.1.4 Geology............................................................................................................................ 18 2.1.5 The benthic