To contribute to the understanding of the invasion biology of common carp Cyprinus carpio in southern Africa, this thesis investigated the life history, relative abundance, long-term population demographics and trophic niche utilisations of non-native common carp C. carpio in relation to two endemic cyprinids, Orange River mudfish Labeo capensis and smallmouth yellowfish Labeobarbus aeneus in South Africa‟s largest impoundment, Lake Gariep. The growth zone deposition rates in astericus otoliths of the three species were validated as biannual for C. carpio and as annual for L. capensis and L. aeneus, which allowed for reliable estimation of lengths-at-age upon which growth, age-at-maturity and mortality rates could be estimated. Cyprinus carpio exhibited fast growth, matured relatively early at two years of age and attained a maximum age of seven years. Labeo capensis grew significantly slower, but attained older ages of up to 12 years. Females showed notably delayed maturation at approximately six years of age. The life history parameter estimates for L. aeneus were similar to those of L. capensis. These species-specific life history characteristics contributed to a substantially higher population growth potential of C. carpio compared to L. capensis and L. aeneus. Delta-lognormal and delta-gamma Generalized Linear Models (GLMs) were used to analyse patterns of relative abundance of L. capensis, L. aeneus and C. carpio. The application of these GLMs was necessary to account for large proportions of zeros and strong skewness in the catch-per-unit-effort (CPUE) from experimental gillnet and fisheries-dependent angler surveys. Confidence intervals around predicted abundance indices were obtained through the development of a generalised parametric bootstrap procedure. The resulting standardised abundance indices were coupled with results from analysis of stable isotope ratios of fish tissues and potential food resources and revealed that C. carpio was mainly confined to soft-bottom habitats, where it predominantly foraged on benthic invertebrates. Labeo capensis was abundant in a wide range of benthic habitats and was consumed basal food resources such as detritus. Labeobarbus aeneus was found to feed mostly on pelagic zooplankton. There were no significant interspecific differences in trophic niche space, suggesting limited resource competition among the three species. Standardised historical and contemporary gillnet CPUE data indicated slow population growth rates of L. capensis and L. aeneus during the first ten years postimpoundment, but showed high biomass levels some four decades after impoundment. These results could be corroborated by stochastic age-structured production model (ASPM) simulations. In contrast to the two endemic species, the gillnet CPUE of C. carpio showed a clear „boom and bust‟ pattern, which, based on ASPM simulations, could be best explained by increased food availability during the first five years postimpoundment, followed by suboptimal conditions thereafter. Together, these results provided evidence that the establishment of the C. carpio population did not prevent the slow but successful long-term establishment of the two large endemic cyprinids. Both endemic fishes revealed specialised feeding within the impoundment.

Thesis (MScEng (Mechanical and Mechatronic Engineering)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: In the Greater Gariep agricultural area adjacent to the Orange River between Prieska and the Vanderkloof dam alone an estimated 311 000 ton/yr of maize and wheat straw is available. These agricultural residues have an energy equivalent of 196 000 ton of coal per year and should be utilised as a renewable energy resource. A technical and financial evaluation on the collection and transport of agricultural residue showed that the Hopetown area has the highest concentration of agricultural residue in the Greater Gariep agricultural area with approximately 68 000 ton/yr that is spread out over 76 kmª. Briquetting, combustion, pyrolysis and gasification were identified as the technologies with the highest potential to convert agricultural residue into a higher grade energy product in this area. The expected overall energy conversion efficiency for a plant capacity between 5 000 to 100 000 ton/yr is 98.9%, 10-25%, 25-30% and 28-36% for the briquetting, combustion, pyrolysis and gasification plants respectively. A financial evaluation based on the internal rate of return and the net present value of investment showed that the briquetting plant is financially feasible and the most profitable for capacities between 25 000 and 60 000 ton/yr while the pyrolysis plant was financially feasible and the most profitable technology for capacities greater than 60 000 ton/yr. A sensitivity and risk analysis done on the proposed briquetting and pyrolysis plants to evaluate the impact of market fluctuations on the profitability of the power plants exposed the briquetting plant as a very high risk investment, mainly because of the sensitivity to the selling price of fuel briquettes and the high maintenance cost associated with the briquetting equipment. Although the proposed pyrolysis plant is sensitive to variation in the electricity price, the risks associated with the market conditions for the pyrolysis plant is very low and an internal rate of return of 15% is still projected at the minimum expected electricity price. From the study it is clear that the utilisation of agricultural residue available in the Greater Gariep agricultural area is technically and financially viable. / AFRIKAANSE OPSOMMING: In die Groter Gariep landbougebied langs die Oranjerivier, tussen Prieska en die Van Der Kloof Dam is daar jaarliks ’n beraamde 311 000 ton mielie- en koringstrooi beskikbaar. Hierdie landbou-reste het die energie-ekwivalent van 196 000 ton steenkool per jaar en behoort as hernubare energiebron benut te word. ’n Tegniese en finansiële evaluasie van die versamel en vervoer van landbou-reste het getoon dat die Hopetown-area die hoogste konsentrasie landbou-reste in die Groter Gariep landbougebied het met ongeveer 68 000 ton/jaar wat versprei is oor 76 kmª. Brikettering, verbranding, pirolise en vergassing is geïdentifiseer as die tegnologieë met die hoogste potensiaal om landbou-reste te omskep in ’n hoër graad energieproduk vir hierdie gebied. Die verwagte totale energie-omsettingseffektiwiteit vir ’n aanlegkapasiteit van tussen 5 000 tot 10 000 ton/jaar is onderskeidelik 98.9%, 10-25%, 25-30% en 28-36% vir die brikettering, verbranding, pirolise en vergassingsaanlegte. ’n Finansiële evaluasie gebaseer op die opbrengs op aanvangskoste en die netto huidige waarde van die belegging het getoon dat die briketteringsaanleg finansieel lewensvatbaar is en die winsgewendste is vir ’n aanlegkapasiteit tussen 25 000 en 60 000 ton/jaar terwyl die pirolise-aanleg finansieel lewensvatbaar is en die winsgewendste tegnologie is vir kapasiteite van groter as 60 000 ton/jaar. ’n Sensitiwiteits- en risiko-analise is op die voorgestelde brikettings- en pirolise-aanlegte gedoen om die impak van markskommelings op die winsgewendheid van die aanlegte te evalueer. Die resultate het getoon dat die briketteringsaanleg ’n baie hoë-risiko belegging is as gevolg van die sensitiwiteit op die verkoopprys van brikette en die hoë onderhoudskoste van briketteringstoerusting. Alhoewel die voorgenome pirolise-aanleg sensitief is vir skommelings in die elektrisiteitsprys, is die risiko’s wat met die marktoestande vir die pirolise-aanleg gepaardgaan, baie laag en ’n opbrengs op aanvangskoste van 15% word steeds voorspel teen die minimum verwagte verkoopsprys van elektrisiteit. Vanuit die studie blyk dit duidelik dat die gebruik van landbou-reste wat beskikbaar is in die Groter Gariep landbougebied, tegnies en finansieel lewensvatbaar is as hernubare energiebron. / Sponsored by the Centre for Renewable and Sustainable Energy Studies

An autecological study of the heterosporous fern Azolla filiculoides Lamarck and its endosymbiotic blue-green alga Anabaena azollae Strasburger, based on a combination of field and laboratory studies, is presented. The taxonomy, morphology and anatomy of the fern-alga association were studied as well as nutritional and physiological aspects of the symbiosis. These studies have defined the habitat and nutritional requirements of the fern and have provided new insights into its reproductive biology, nitrogen metabolism and the nature of the association between the fern and alga. In the catchment area of the Hendrik Verwoerd Dam the availability of suitably sheltered habitat limits the distribution of A. filiculoides while the availability of nutrients, in particular calcium, phosphorus and iron, limits the growth of the fern. The multilayered mats formed by A. filiculoides are essential for spore production, cause dramatic changes in the hydrochemistry of the underlying waters and confer a great competitive advantage on the plant. Methods for the isolation of the fern and algal components of the symbiosis have been developed but recombination of the individual organisms to reform the symbiosis was unsuccessful. The development of the fern is closely linked to that of the alga and the association is maintained throughout the life cycle of the fern. Because of its specific habitat and nutritional requirements, A. filiculoides is unlikely to colonize the open waters of the Hendrik Verwoerd Dam.

The concept of cross-border tourism planning and cooperation is investigated in reference to the Lake !Gariep Initiative. The field of cross-border economic planning and integration is an area of increasing interest in regional development studies. The Lake Gariep Initiative is an initiative to promote cross-border planning and development around nature conservation, water resource management, economic development, poverty alleviation and tourism in the three municipalities that surround the Gariep Dam. The Gariep Dam, which is largest dam in South Africa, is surrounded by three provinces. The region is also economically and politically marginalised as it has a small, dispersed population and a marginal contribution to the broader regional economy. Under these circumstances the coordination of resources between municipalities to develop and promote the region has been identified as a key success factor for the region. The Lake Gariep Initiative although strongly supported locally has over ten years failed to be institutionalised. This study examines the Lake Gariep Initiative in terms of the origins of the concept and the key challenges that have been faced in establishing a cross-border, development entity. Findings are based on an assessment of documents on the formation of the LGI, interviews with stakeholders involved in the process and an assessment of critical success factors in reference to national and international case studies. This study provides a review of the key challenges, benefits and critical success factors for cross-border tourism development in relation to the Lake !Gariep Initiative.

A large sportfishery that targets both smallmouth (Labeobarbus aeneus) and largemouth (Labeobarbus kimberleyensis) yellowfish exists in South Africa. Both species have high conservation priority, and no assessments documenting the effect of angling on L. aeneus and L. kimberleyensis have been undertaken. The overall aim of this study was to provide an assessment of the impact of angling on L. aeneus and L. kimberleyensis. The specific objectives of this study were to characterise the sectors utilising Lake Gariep, document catch, effort and total catch for the fishery as well as the locality specific biology of L. aeneus and L. kimberleyensis. The study was undertaken on Lake Gariep, South Africa's largest impoundment, situated on the Orange River system in central South Africa. Subsistence fishers were the dominant user group, constituting 60 % of the fishery, the remainder constituted recreational anglers. Angler catches were dominated by carp (Cyprinus carpio; 74 %), followed by mudfish (Labeo capensis; 13 %) and smallmouth yellowfish (8 %). Catches of largemouth yellowfish contributed < 0.5 % to the total catch. The relative abundance of species by weight differed by area (χ² test of independence: χ² = 182, df = 4, p ≤ 0.05). On any sampling day time fished was the best predictor for differences in probability of capture (PC) (Wald X²(1) = 7.169, p = 0.007). The probability of capturing L. aeneus differed significantly between month (Wald X²(5) = 20.690, p = 0.000) and region (Wald X²(3) = 46.755, p = 0.000). The single best predictor of differences in log abundance and non-zero CPUE was region (Factorial ANOVA p ≤ 0.05). Mean CPUE ranged from 0.21 ± 0.06 kg. man⁻¹.hr⁻¹ to 0.82 ± 0.11 kg. man⁻¹.hr⁻¹ in the OV region and 0.42 ± 0.10 kg. man⁻¹.hr⁻¹ to 1.17 ± 0.24 kg. man⁻¹.hr⁻¹ in the GD region. Angler effort was higher in OV than in GD and ranged from 17 ± 3 anglers/day to 45 ± 9 anglers/day and 6 ± 1 anglers/day to 41 ± 8 anglers/day, respectively. Total catch was higher in the GD 46.0 [95 % CI = 15:102.6] t. period⁻¹ than the OV region 40.0 [95 % CI = 13.9:89.6] t. period⁻¹. The total catch from the Lake Gariep fishery between March and December 2007 was estimated to be 86.0 [95 % CI = 40.4:154.8] t. period⁻¹. Age and growth was determined using whole otoliths. The growth of L. aeneus was best described by the von Bertalanffy growth model as Lt = 481.80 (1- e⁻°·²²⁽t⁺°·⁶¹⁾). Gonadal development for L. aeneus was seasonal, with the gonadosomatic index peaking in January, revealing a distinct spawning season. The length at 50 % maturity for female L. aeneus was attained at a fork length of 354.7 mm. Natural mortality (M) was estimated at 0.55 year⁻¹. The growth of L. kimberleyensis was described by the von Bertalanffy growth model as Lt = 763.22 (1- e⁻°·¹¹⁽t⁺°·⁶³⁾). Only 6 mature female and 15 mature male L. kimberleyensis were recorded during the study period. The smallest mature female was a 390 mm FL stage four female and the earliest recorded mature male was a 337 mm FL, ripe running male. Natural mortality (M) was estimated at 0.08 year⁻¹ for L. kimberleyensis. Per recruit analysis indicated that current fishing mortality reduces the L. aeneus spawner biomass by 7 %, which is considered negligible. Labeobarbus kimberleyensis forms an insignificant proportion of anglers catches and stock status is currently considered pristine.

Skanskopeiland is een van die besproeiingsnedersettings wat in die vroeë twintigste eeu langs die Benede-­‐Oranjerivier (vandag bekend as die Gariep) gevestig is met die doel om blanke armoede te help verlig. Na afloop van die Carnegiekommissie se ondersoek na blanke armoede en die daaropvolgende Volkskongres in Kimberley (1934) was dit in die 1930’s beide die staat en die kerk se benadering om arm gemeenskappe te ondersteun om deur selfwerksaamheid vir hulle en hulle nageslag ʼn selfstandige bestaan te verseker. Terselfdertyd kon hulle deur landbouproduksie ʼn bydrae tot die landsekonomie en die ontwikkeling van die streek maak. Hoewel hulle na die toekenning van grond feitlik geen verdere staatshulp ontvang het nie en oor beperkte hulpbronne beskik het, is die meeste van die eerste nedersetters op Skanskopeiland suksesvol gevestig. Aangedryf deur die wil om vir hulleself te sorg en vir hulle gesinne ʼn beter bestaan moontlik te maak, was hulle bereid om fisies hard te werk. Met behulp van mentorskap, wat deur die staat voorsien is, het hulle met selfwerksame optrede binne tien jaar ʼn woesteny omskep in ʼn suksesvolle landbounedersetting. Hulle het die eenvoudige tegnieke en tegnologie wat beskikbaar was, aangewend om die natuur te “tem” en die vrugbare grond voor te berei vir landbouproduksie. Hierdie studie skets die historiese agtergrond waarbinne die nedersetting op Skanskopeiland gevestig is, beskryf die moeisame prosesse waardeur die nedersetters die eiland vir landbouproduksie gereed gemaak het en beoordeel hulle pogings om hulleself en hulle nageslag uit armoede op te hef. ʼn Empiriese studie, wat as deel van die navorsing onderneem is, het die impak van die opheffing op die nasate van die pioniernedersetters bepaal en die bevinding daarvan word in die studie gerapporteer. / MA (History), North-West University, Potchefstroom Campus, 2015

Skanskopeiland is een van die besproeiingsnedersettings wat in die vroeë twintigste eeu langs die Benede-­‐Oranjerivier (vandag bekend as die Gariep) gevestig is met die doel om blanke armoede te help verlig. Na afloop van die Carnegiekommissie se ondersoek na blanke armoede en die daaropvolgende Volkskongres in Kimberley (1934) was dit in die 1930’s beide die staat en die kerk se benadering om arm gemeenskappe te ondersteun om deur selfwerksaamheid vir hulle en hulle nageslag ʼn selfstandige bestaan te verseker. Terselfdertyd kon hulle deur landbouproduksie ʼn bydrae tot die landsekonomie en die ontwikkeling van die streek maak. Hoewel hulle na die toekenning van grond feitlik geen verdere staatshulp ontvang het nie en oor beperkte hulpbronne beskik het, is die meeste van die eerste nedersetters op Skanskopeiland suksesvol gevestig. Aangedryf deur die wil om vir hulleself te sorg en vir hulle gesinne ʼn beter bestaan moontlik te maak, was hulle bereid om fisies hard te werk. Met behulp van mentorskap, wat deur die staat voorsien is, het hulle met selfwerksame optrede binne tien jaar ʼn woesteny omskep in ʼn suksesvolle landbounedersetting. Hulle het die eenvoudige tegnieke en tegnologie wat beskikbaar was, aangewend om die natuur te “tem” en die vrugbare grond voor te berei vir landbouproduksie. Hierdie studie skets die historiese agtergrond waarbinne die nedersetting op Skanskopeiland gevestig is, beskryf die moeisame prosesse waardeur die nedersetters die eiland vir landbouproduksie gereed gemaak het en beoordeel hulle pogings om hulleself en hulle nageslag uit armoede op te hef. ʼn Empiriese studie, wat as deel van die navorsing onderneem is, het die impak van die opheffing op die nasate van die pioniernedersetters bepaal en die bevinding daarvan word in die studie gerapporteer. / MA (History), North-West University, Potchefstroom Campus, 2015