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An Assessment of Inland Fisheries in South Africa

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An Assessment of Inland Fisheries in South Africa AN ASSESSMENT OF INLAND FISHERIES IN SOUTH AFRICA USING FISHERIES-DEPENDENT AND FISHERIES- INDEPENDENT DATA SOURCES A thesis submitted in fulfilment of the requirements for the degree of MASTER OF SCIENCE of RHODES UNIVERSITY by James Ross McCafferty February 2012 Abstract The role of inland fisheries as contributors to local and national economies in developing African countries is well documented. In South Africa, there is increasing interest in inland fisheries as vehicles for achieving national policy objectives including food security, livelihoods provision, poverty alleviation and economic development but there is surprisingly little literature on the history, current status, and potential of inland fishery resources. This lack of knowledge constrains the development of management strategies for ensuring the biological sustainability of these resources and the economic and social sustainability of the people that are dependent on them. In order to contribute to the knowledge base of inland fisheries in South Africa this thesis: (1) presents an exhaustive review of the available literature on inland fisheries in South Africa; (2) describes the organisation of recreational anglers (the primary users of the resource); (3) compiles recreational angling catch records and scientific gill net survey data, and assesses the applicability of these data for providing estimates of fish abundance (catch-per-unit effort [CPUE]), and finally, (4) determines the potential for models of fish abundance using morphometric, edaphic, and climatic factors. The literature review highlighted the data-poor nature of South African inland fisheries. In particular information on harvest rates was lacking. A lack of knowledge regarding different inland fishery sectors, governance systems, and potential user conflicts was also found. Recreational anglers were identified as the dominant user group and catch data from this sector were identified as potential sources of fish abundance and harvest information. Formal freshwater recreational angling in South Africa is a highly organised, multi-faceted activity which is based primarily on angling for non-native species, particularly common carp Cyprinus carpio and largemouth bass Micropterus salmoides. Bank anglers constituted the largest number of formal participants (5 309 anglers affiliated to formal angling organisations) followed by bass anglers (1 184 anglers affiliated to formal angling organisations). The highly structured nature of organised recreational angling and dominant utilisation of inland fisheries resources by this sector illustrated not only the vested interest of anglers in the management and development of inland fisheries but also the role that anglers may play in future decision-making and monitoring through the dissemination of catch data from organised angling events. ii Generalised linear models (GLMs) and generalised additive models (GAMs) were used to standardise CPUE estimates from bass- and bank angling catch records, which provided the most suitable data, and to determine environmental variables which most influenced capture probabilities and CPUE. Capture probabilities and CPUE for bass were influenced primarily by altitude and conductivity and multiple regression analysis revealed that predictive models incorporating altitude, conductivity, surface area and capacity explained significant (p < 0.05) amounts of variability in CPUE (53%), probability of capture (49%) and probability of limit bag (74%). Bank angling CPUE was influenced by conductivity, surface area and rainfall although an insignificant (p > 0.05) amount of variability (63%) was explained by a predictive model incorporating these variables as investigations were constrained by small sample sizes and aggregated catch information. Scientific survey data provided multi-species information and highlighted the high proportion of non-native fish species in Eastern Cape impoundments. Gillnet catches were influenced primarily by species composition and were less subject to fluctuations induced by environmental factors. Overall standardised gillnet CPUE was influenced by surface area, conductivity and age of impoundment. Although the model fit was not significant at the p<0.05 level, 23% of the variability in the data was explained by a predictive model incorporating these variables. The presence of species which could be effectively targeted by gillnets was hypothesised to represent the most important factor influencing catch rates. Investigation of factors influencing CPUE in impoundments dominated by Clarias gariepinus and native cyprinids indicated that warmer, younger impoundments and smaller, colder impoundments produced higher catches of C. gariepinus and native cyprinids respectively. A predictive model for C. gariepinus abundance explained a significant amount of variability (77%) in CPUE although the small sample size of impoundments suggests that predictions from this model may not be robust. CPUE of native cyprinids was influenced primarily by the presence of Labeo umbratus and constrained by small sample size of impoundments and the model did not adequately explain the variability in the data (r2 = 0.31, p>0.05). These results indicate that angling catch- and scientific survey data can be useful in providing predictions of fish abundance that are biologically realistic. However, more data over a greater spatial scale would allow for more robust predictions of catch rates. This could be achieved through increased monitoring of existing resource users, the creation of a iii centralised database for catch records from angling competitions, and increased scientific surveys of South African impoundments conducted by a dedicated governmental function. iv Acknowledgements Firstly, I would like to thank my supervisor, Dr Olaf Weyl, for providing me with immeasurable insight and advice throughout the course of this thesis. Your unerring dedication and drive, as well as your passion for freshwater fishes, have contributed in so many ways to the completion of this thesis (including pulling all-nighters to mark chapter drafts!). Your assistance with data collection, in providing me with contacts for angling representatives and colleagues all over South Africa, has proved invaluable to the outcomes of this study, and I thank you sincerely for your input. To Dr Henning Winker, it is difficult to express my level of gratitude for the help that you so willingly gave me concerning the most complex and crucial aspects of this thesis. Your enthusiasm and approachable nature, coupled with immense know-how of a challenging (and daunting!) field, are in my experience unsurpassed and hugely appreciated. The knowledge that you imparted in only three short days has not only shaped a large part of this thesis, but has also sparked my interest in ecological modelling and statistics. Thank you. To Dr Ernst Swartz, thank you for providing me with important information and insight into the NEM:BA process, as well as the maps from the survey process, and much needed company and advice on conference trips. I would like to thank the following angling officials and representatives who contributed large amounts of their time and effort into providing contacts, data, and other information for the project: Mr John Pledger, Mr Fred Visagie, Mr Andre Nortje; Mr Trevor Spencer; Mrs Wendy Watson; Mr Bernard Venter; Mr Cyril Schwarz; Mr Louwtjie Louwens; Mr Eugene Kruger; Mr Jaco Janse van Rensburg; Mrs Sue Babich; Mr Barry Kurten; Mr Tim Mundy; Mr Knop van der Merwe; Mr Richard Prinsloo; Mr Albert Olivier; Mr Dawie Jacobs; Mr Louis Erasmus; Mr Hennie Zeelie; Mr Corrie Barnard; Ms Meisie Schneider; Mr Piet Rall. v Without your input this project would not have been possible and for this I sincerely thank you. Thanks are also due to colleagues within the Department of Icthyology and Fisheries Science, in particular Dr, Warren Potts, Tim Richardson, Bruce Ellender, Geraldine Taylor, Qurban Rouhani, who provided me with their gillnet data and additional input on the project. I would also like to thank Taryn Murray, Matthew Parkinson, Richard Peel, and Reece Wartenberg for their continued friendship, support and advice throughout my time at DIFS and particularly during the completion of this thesis. I would also like to thank Jeremy Baxter foIt is much appreciated. Thanks are also due to Jeremy Baxter for his statistical insights and useful advice. I would also like to acknowledge the Water Research Commission (WRC) for providing funding for this project, as well as the South Africa Netherlands Research Programme on Alternatives in Development (SANPAD) for funding gillnet surveys in the Eastern Cape used in this thesis. Lastly to my family, Dad, Mom, and Richard. Mom and Dad, your unwavering support and belief in me throughout my life has been a source of constant inspiration .Rich, late night/early morning phone calls from the office always spurred me on and you have always been the first person I go to for guidance and encouragement. Thank you. vi Table of Contents Abstract ……… ....................................................................................................................... ii Acknowledgements ..................................................................................................................... v List of figures .......................................................................................................................... ix List of tables ........................................................................................................................
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