Town The copyright of this thesis rests with the University of Cape Town. No quotation from it or information derivedCape from it is to be published without full acknowledgement of theof source. The thesis is to be used for private study or non-commercial research purposes only. University Ecosystem effects of a rock-lobster 'invasion': comparative and modelling approaches Laura Kate Blamey Town Cape Of Supervisors: Emeritus Professor George M. Branch and Dr Éva Plagányi-Lloyd Thesis presented for the Degree of UniversityDoctor of Philosophy In the Department on Zoology Faculty of Science University of Cape Town February 2010 Town Cape Of University “For in the end, we will conserve only what we love, we will love only what we understand, and we will understand only what we are taught.” ~ Baba Dioum, 1968. This thesis is dedicated to my parentsTown Campbell and Ursula Blamey Cape And to my grandfather DonaldOf Currie University Town Cape Of University Declaration I hereby declare that all the work presented in this thesis is my own, except where otherwise stated in the text. This thesis has not been submitted in whole or in part for a degree at any other university. Town _____________________ Laura Kate Blamey Cape _____________________ Of Date University Table of Contents Acknowledgements...................................................................................................... iii Abstract.......................................................................................................................... v Glossary .......................................................................................................................vii Chapter 1 Setting the scene: introduction and overview of thesis................................................1 1.1 Kelp Forest Ecosystems ................................................................................................ 2 1.2 The South African Abalone Haliotis midae................................................................. 6 1.3 The Cape Urchin Parechinus angulosus...................................................................... 6 1.4 Urchin-Abalone Interactions........................................................................................ 7 1.5 The West Coast Rock Lobster Jasus lalandii.............................................................. 8 1.6 An Ecosystem Approach to Fisheries (EAF) ............................................................ 14 1.7 Breakdown and Overview of Thesis.......................................................................... 21 Chapter 2 Temporal changes in kelp forest benthic community structureTown at two sites East of Cape Hangklip.............................................................................................................23 2.1 Introduction................................................................................................................. 24 2.2 Methods........................................................................................................................ 27 2.3 Results ....................................................................................................................Cape ...... 29 2.4 Discussion.................................................................................................................Of .... 33 Chapter 3 Spatial differences in kelp forest benthic community structure: impacts of an ‘invasion’ by the rock lobster Jasus lalandii..............................................................39 3.1 Introduction................................................................................................................. 40 3.2 Methods........................................................................................................................ 44 3.3 Results .......................................................................................................................... 49 3.4 Discussion.................................................................................................................University .... 58 3.5 Conclusions.................................................................................................................. 75 Chapter 4 A Minimally Realistic Model of lobster-urchin-abalone interactions in a lobster- invaded area East of Cape Hangklip..........................................................................79 4.1 Introduction................................................................................................................. 80 4.2 Study Area ................................................................................................................... 83 4.3 Data .............................................................................................................................. 84 4.4 Rock Lobster Model Assumptions............................................................................. 88 4.5 Model Description ....................................................................................................... 90 4.6 Model Equations ......................................................................................................... 94 i 4.7 Parameters................................................................................................................. 108 4.8 Results and Discussion.............................................................................................. 109 4.9 Summary.................................................................................................................... 122 Chapter 5 Sensitivity analyses and future projections for a Minimally Realistic Model in a lobster-invaded area East of Cape Hangklip. ..........................................................125 5.1 Introduction............................................................................................................... 126 5.2 Sensitivity Analyses................................................................................................... 127 5.3 Akaike Information Criterion.................................................................................. 132 5.4 Future Projections..................................................................................................... 132 5.5 Results and Discussion.............................................................................................. 133 5.6 Summary.................................................................................................................... 145 Chapter 6 Modelling a hypothetical invasion of rock lobsters .................................................149 6.1 Introduction............................................................................................................... 150 6.2 Model Description and Data ....................................................................................Town 152 6.3 Model Assumptions................................................................................................... 153 6.4 Results ........................................................................................................................ 154 6.5 Discussion.................................................................................................................Cape .. 156 6.5 Summary.................................................................................................................... 158 Chapter 7 Of Impacts of depleting top predators on the predatory effects of rock lobsters on benthic communities .................................................................................................161 7.1 Introduction............................................................................................................... 162 7.2 Fish Species................................................................................................................ 164 7.3 Model Description ..................................................................................................... 164 7.4 Data .......................................................................................................................University ..... 165 7.5 Model Assumptions................................................................................................... 168 7.6 Equations ................................................................................................................... 170 7.7 Parameters................................................................................................................. 176 7.8 Results ........................................................................................................................ 177 7.9 Discussion................................................................................................................... 181 Chapter 8 Synthesis....................................................................................................................189 Appendices.................................................................................................................199 Literature cited ..........................................................................................................225 ii Acknowledgements This project would not have been possible without the financial support I received from the NRF (National Research Foundation), the Andrew W. Mellon Foundation, the History of the Nearshore Project and the South African Research Chairs Initiative of the Department of Science and