INFLUENCE OF WATERFALLS ON PATTERNS OF ASSOCIATION BETWEEN TROUT AND NATAL CASCADE FROG HADROMOPHRYNE NATALENSIS TADPOLES IN TWO HEADWATERSTREAMS OF THE UKHAHLAMBA DRAKENSBERG PARK WORLD HERITAGE SITE by ROBERT JEFFERY KARSSING Submitted in fulfillment of the requirements for the degree of MASTER OF SCIENCE in ENVIRONMENTAL SCIENCE College of Agriculture and Environmental Sciences at the UNIVERSITY OF SOUTH AFRICA (UNISA) SUPERVISOR: DR K. SLATER CO-SUPERVISOR: DR. N. RIVERS-MOORE JUNE 2010 I INFLUENCE OF WATERFALLS ON PATTERNS OF ASSOCIATION BETWEEN TROUT AND NATAL CASCADE FROG TADPOLES HADROMOPHRYNE NATALENSIS IN TWO HEADWATER STREAMS OF THE UKHAHLAMBA DRAKENSBERG PARK WORLD HERITAGE SITE Robert Jeffrey Karssing Supervisors: Dr. K. Slater1 Dr. N. River-Moore2 Departments: 1Department of Environmental Sciences, University of South Africa (UNISA) 2 Consulting Freshwater Ecologist Submitted for the degree of Master of Science (Environmental Science) in the School of Environmental Sciences. SUMMARY Current literature suggests that little, if any, research has been conducted in South Africa to determine the impact of alien invasive trout on indigenous amphibian biodiversity. The primary aim of the research project was to establish whether waterfalls are seasonally important in protecting the indigenous Natal Cascade Frog Hadromophryne natalensis tadpole populations from predation by alien rainbow trout Oncorhynchus mykiss and brown trout Salmo trutta at two sampling areas located at Injesuthi and Monk‟s Cowl Nature Reserve within the uKhahlamba Drakensberg Park World Heritage Site (UDPWHS). The dissertation argues in favour of a biotic rationale, namely trout predation, as being the primary cause for the decline of H. natalensis tadpoles below the waterfalls and systematically negates the influence of geo-physical (abiotic) environmental factors on II tadpole abundance. Habitat isolation and fragmentation is identified as a latent threat to the continued persistence of H. natalensis populations in the UDPWHS. Key words – amphibian, Brown Trout Salmo trutta, Rainbow Trout Oncorhynchus mykiss, alien, invasive, predation, waterfall, isolation, fragmentation. Dissertation submitted in honour of my friends and colleagues Mark Coetzee and James Wakelin who died in a light aircraft crash in Mozambique, 2007. III ACKNOWLEDGEMENTS Thanks to the Lord Jesus Christ, for providing me with an opportunity to study further, placing mentors in my life and for keeping us safe in the field. Many thanks to my supervisor Dr. Kerry Slater for her guidance in writing up the dissertation and keeping me well informed about University events and information resources. Thank you so much to the librarians at UNISA who went the extra mile in sourcing journal articles for me. Many thanks to my very good friend and mentor, Dr Nicholas River-Moore, who accompanied me diligently in the field and ensured that I approached my research project according to scientifically, approved methodology and protocols. To my biodiversity colleagues and friends, Messrs. Mncedi Nkosi and Patrick Kubheka, who unselfishly assisted me in the field despite all the physical challenges associated with the process. Thanks also to Heidi Snyman, the Ezemvelo KZN Wildlife cartographer, for ably assisting me in the development of my maps and Boyd Escott, our GIS analyst, for helping me solve an endless array of GIS, database and spreadsheet related problems. Thanks also to Mr. Craig Morris, Senior Researcher, Agricultural Research Council (ARC), based at the University of KwaZulu-Natal (UKZN), who assisted me with the design of my research project relative to statistical tests. Thanks to my good friend and colleague, Mr. John Craigie, who accompanied me in my earlier field surveys that ultimately culminated in the development of this research project. A vote of thanks also to Alan and Sonja Howell who provided us with comfortable accommodation at Monk‟s Cowl Nature Reserve and field rangers to assist us with the carrying of our equipment. Thanks to hospitality manager Dennis Miya and his friendly camp staff at Injesuthi Nature Reserve for providing us with comfortable accommodation. I would also like to express my thanks to my senior managers Dr Jean Harris, Mr. Peter Thomson and Dr Peter Goodman for granting me the opportunity and time to complete to complete this dissertation. Special thanks to my employer Ezemvelo KZN Wildlife for awarding me with a study bursary and for sponsoring my field work in terms of time, accommodation and transportation. Last, but not least, a special thanks to my wife Renée and daughters Shea and Kerryn for supporting me loyally throughout the duration of my studies. IV DISCLAIMER These studies represent original work by the author and have not otherwise been submitted in any form for any degree or diploma to any University or other academic institution. Where use has been made of the work of others, it is duly acknowledged in the text. All the experimental work described in this dissertation was carried out in the School of Agriculture and Environmental Sciences, University of South Africa (UNISA) under direct supervision of my UNISA supervisor Dr. Kerry Slater in close collaboration with my co- supervisor Dr. Nicholas Rivers-Moore. PREAMBLE I am currently employed as a Chief Aquatic Research Technician with the provincial conservation agency Ezemvelo KwaZulu-Natal Wildlife, South Africa. I was tasked in 2004 to carry out field surveys in the uKhahlamba Drakensberg Park World Heritage Site (UDPWHS), South Africa, to assess what impact, if any, invasive alien trout may have had on indigenous biodiversity. A number of field surveys were conducted above (trout absent) and below (trout present) selected waterfalls within the UDPWHS. These preliminary field surveys suggested that the populations of the Natal Cascade Frog Hadromophryne natalensis tadpoles are substantially reduced below certain waterfalls where trout occur. This study is primarily aimed at understanding the pivotal role that waterfalls play in conserving H. natalensis populations in the UDPWHS by empirically investigating the link that exists between trout and tadpole abundance. The project argues in favour of a biotic reason (trout predation) being primarily responsible for the decline in tadpole abundance below waterfalls in the UDPWHS, and conversely argues against the role that abiotic environmental factors may have played, relative to the similarities in geo-physical conditions occurring both above and below two selected waterfalls in the UDPWHS. V TABLE OF CONTENTS SUMMARY…………………………………………………………………………..….II ACKNOWLEDGEMENTS……………………………………………………….….....IV DISCLAIMER……………………………………………………………….……….…..V PREAMBLE……………………………………………………………………...………V CHAPTER 1…………………………………………………………………….………...1 1 INTRODUCTION………………………………………………………………..1 1.1 General…………………………………………………………………….1 1.2 The importance of researching amphibians……………………………….2 1.3 Threat of alien invasive species to freshwater biodiversity ………………2 1.4 Threat of introduced alien fish on amphibian biodiversity………………..6 1.5 Trout as alien invaders…………………………………………………….7 1.6 The importance of recreational angling as a medium for the Introduction of invasive species………………………………………….11 1.7 The impact of trout on indigenous amphibians…………………………..14 1.8 Case studies involving the decline amphibians due to trout predation…..15 1.8.1 Mountain Yellow-legged Frogs Rana muscosa………………….15 1.8.2 Pacific Treefrogs Hyla regilla…………………………………...16 1.8.3 Spotted Tree Frog Litoria spenceri………………………………17 1.8.4 Tailed Frog Ascaphus truei………………………………………18 1.8.5 Other amphibian case studies involving trout predation…………18 1.9 Anti-predator mechanisms of amphibians…………………………...…..19 1.9.1 The important role of cover in protecting amphibians…………...19 1.9.2 Anti-predator mechanisms of amphibians……………...………..20 1.10 Recovery of amphibian populations after the removal of alien predators……………………………………………………………...…..24 1.11 Why the Natal Cascade Frog Hadromophryne natalensis is an Important research ………………..…………………………….……….26 VI 1.12 Trout Ecology………………………………………………………..…..27 1.12.1 Distribution of Brown Trout S. trutta and Rainbow Trout O. mykiss...................................................................................................27 1.12.2 General habitats requirements of trout....………………………...28 1.13 Biology of Natal Cascade Frog Hadromophryne natalensis.....................32 1.14 Relevance of the study…………………………………………………...33 1.15 Aim of the study…………………………………………………………34 1.16 Specific research questions………………………………………………34 1.17 Constraints to this dissertation………………………………………….35 1.18 Dissertation outline………………………………………………………35 CHAPTER ……………………………………………………………………………...38 2 METHODS………………………………………………………………...……38 2.1 Description of study area………………………………………………...38 2.2 GIS Interpretation of sampling areas…………………………………….39 2.3 GIS Delineation of sampling sites……………………………………….39 2.4 Delineation of sampling sites in the field……………………………….40 2.5 Sampling frequency……………………………………………………...42 2.6 Gridded geomorrphological data collecting……………………………...43 2.7 Water flow velocity and depth…………………………………………..46 2.8 Water quality variables…………………………………………………..49 2.9 Electrofishing…………………………………………………………….51 2.10 Data analysis 2.10.1 Geo-physical parameters…………………………………………53 2.10.2 Water quality……………………………………………………..54 2.10.3 Principal Components Analysis (PCA)………………………….54 2.10.4 Electrofishing…………………………………………………….54 2.10.5 Habitat overlap between H. natalensis tadpoles and trout……….56