No abstract available. Copyright / Dissertation (MSc)--University of Pretoria, 2009. / Chemistry / unrestricted

Heaviside's dolphin (Cephalorhynchus heavisidii) is a poorly studied coastal delphinid with a limited inshore distribution off the west coast of southern Africa where it is sympatric with the similar sized dusky dolphin (Lagenorhynchus obscurus). It is exposed to an unknown level of bycatch particularly in near-shore set-net fisheries and is also potentially impacted by the growing boat-based whale watching industry in South Africa. In this thesis I describe the results of a study investigating the distribution, movements, behaviour and abundance of Heaviside's dolphins in the near-shore environment of the Western Cape of South Africa as a precursor to assessing its potential vulnerability to anthropogenic threats. Data were gathered using three different approaches in the field; diurnal shore based observations, boat based photo-ID surveys along ~390 km of coastline and satellite telemetry. Data were collected for dusky dolphins where feasible. Heaviside’s dolphins exhibited a strong pattern of resting inshore during daytime and foraging offshore at night that was presumed to be related to the movement of juvenile hake (Merluccius capensis) closer to the surface at night. In addition, despite near-shore observations failing to indicate feeding, dolphins were consistently found to be more abundant along regions of the coast which over the long term had higher levels of small hake available offshore. In contrast the near-shore distribution of dusky dolphins varied considerably between years possibly due to the very near-shore environment being at the edge of their habitat. A tendency for dusky dolphins to move offshore during upwelling conditions was observed from shore in St Helena Bay, the site of a strong predictable upwelling cell. However this was the only location in which very large groups of animals (50-500) were seen during coastal boat surveys suggesting this pattern may have been area specific and feeding strategies may vary throughout their range. Sympatric appears to be mediated by differences in overall range and prey type and size differentiation. Heaviside’s dolphins were found to have small home ranges and show a high degree of site fidelity over several years, at least during summer months. Dolphins fitted with satellitelinked transmitters used only limited home ranges (~876 to 1990 km2) which scaled positively with body size within the ~50 day tracking period, while photographically identified animals did not disperse significantly further than this over 3 years. The maximum coastwise displacement observed for an individual (88.4 km after 1 year) was considerably less than the 390 km length of the overall study area, and equivalent to the maximum coastwise movement seen during satellite-tagging (83.1 km). This suggests that measured home ranges may be stable over several years, although the number of resighted individuals (n = 76) was small and (as data collection was restricted to summer months) seasonal differences in movements or migrations cannot be ruled out. Associations among photographically identified animals did not differ from a random mixing of individuals, suggesting that this species has a fission-fusion type social structure at least over the short term. The abundance of Heaviside's dolphins was calculated from photo-ID mark-recapture data at three spatial scales using Chapman’s modified Petersen estimators. The proportion ofdistinctively marked individuals in this species is low (14 - 17%) reducing sample sizes and introducing a large extrapolation factor, both of which contribute to an increase in the variance of any resultant population estimate. Using resightings after one year, the total number of animals over the whole 390km study area was calculated to be 6345 (CV = 0.26, CI = 3573 – 11 267) while using same-season re-sightings the total number of animals using a 20km long section of coastline in the centre of the study area was calculated as 527 (CV = 0.35, CI = 272 – 1020). These estimates may be significantly biased downwards by the effects of heterogeneity in the capture probability of individuals which it was not possible to account for analytically due to small sample sizes. Sympatry of Heaviside's and dusky dolphins appears to be mediated by differences in the overall range and in the type and size of prey consumed. From a conservation point of view, our findings for Heaviside's dolphins are encouraging in that they indicate a relatively large population size, although their strong site fidelity does make them more vulnerable to localised impacts than a more widely ranging species like dusky dolphins and this needs to be considered during management of the population. / Thesis (PhD)--University of Pretoria, 2009. / Zoology and Entomology / unrestricted

Thesis (PhD)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Aquaculture has proven to be a viable operation in multi-used irrigation reservoirs (also referred to as farm dams) in the Western Cape province (WCP) of South Africa. Many studies found that the fitness-for-use of these reservoirs for both net cage culture of fish and irrigation of crops is feasible. However, practising intensive fish farming in existing open water bodies can increase the nutrient levels of the water through organic loading, originating from uneaten feeds and fish metabolic wastes. Under such conditions the primary (irrigation) and secondary (drinking water and recreation) usage of the dam could be compromised by deteriorating water quality. Rainbow trout (Oncorhynchus mykiss) farming is done in Mediterranean climatic conditions of the WCP. This type of climate presents short production seasons with fluctuating water quality and quantity. The study investigated the dynamics of water physico-chemical parameters and assessed the long term impact of rainbow trout farming on irrigation reservoirs. Furthermore, associated land-use in the catchment of such integrated aqua-agriculture systems is described, and mitigation to minimise the impact of fish farming evaluated. The investigation concluded with assessing the contribution of aquaculture to rural and peri-urban communities. The aim is to present an integrated, socio-ecologically balanced farming system for irrigation reservoirs with associated aquaculture activities. A total of 35 reservoirs, including both fish farming and non-fish farming ones, were selected as research sites. They were located in three geographical regions namely, Overberg (Grabouw/Caledon), Boland (Stellenbosch/Franschhoek) and Breede River (Ceres/Worcester). Reservoirs were <20 ha in surface area and the volume ranges from 300 000 to 1 500 000 m3. Water samples were collected monthly and seasonally for the different investigations and analysed for a range of water quality parameters, including: transparency (Secchi disc), temperature, dissolved oxygen (DO), pH, sodium (Na), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), chloride (Cl), carbonate (CO3), bicarbonate (HCO3), manganese (Mn), copper (Cu), zinc (Zn), boron (B), total phosphorous (TP), orthophosphate (PO4), total ammonia nitrogen (TAN), nitrate-nitrogen (NO3-N), nitrite-nitrogen (NO2-N), aluminium (Al), total suspended solids (TSS), total dissolved solids (TDS), alkalinity, hardness and sulphate. Phytoplankton samples were also collected, genera identified and biomass calculated. The water quality data were analysed in terms of surface and bottom strata in both fish farming and non-fish farming reservoirs based on repeated measurements at the same site location at different times using the procedure General Linear Models of Stastical Analysis System (SAS, 2012). Values p<0.05 were considered as statistically significant. A Principal Component Analysis (PCA) biplot was used to graphically depict all the sites and measured water quality variables with the purpose of trying to see whether the fish farming and non-fish farming ones showed any groupings and how the sites were related to the measured variables. Structured questionnaires and informal discussions were used to collect additional information on the water use, production data and socio-economic effects on fish farmers. Categorical data gathered from the interviews (21 aquaculture projects) were analysed for frequency of occurrence using the Statistical Product and Service Solutions (SPSS) computer programme (SPSS Systems for Windows, Version 12.0). Results are presented in publication form with research chapters focusing on the subject areas of water quality impact, catchment land-use, potential mitigation measures and aquaculture contribution. Results for the water quality analyses indicated that as a collective, the farm reservoirs’ overall minimum, mean and maximum values for the physico-chemical parameters were fit-for-use for trout farming. The depth of the reservoirs ranged from 1.2 - 21.6 m with the low value taken during the summer season. Values lower than 5.0 m can cause management problems for floating cages that require a minimum of 4.0 m for net suspension and 1.0 m of free space below for adequate lateral flow. The Secchi disc reading of the reservoirs ranged from 10 – 510 cm. Higher transparencies were recorded after the winter rains when sand, silt and clay settled. Trout feeding is dependent on visibility and transparencies of more than 50 cm are required for good feeding conditions. The dissolved oxygen (DO) ranged from 0.3 – 16.4 mg/L with values below 5.00 mg/L recorded during summer when extraction and temperatures were high and provided conditions unable to sustain trout farming. The situation reverses with the onset of winter when the dams fill and DO rises above 5.00 mg/L as required for trout farming. The phosphorous (P) levels ranged from 0.001 – 0.735 mg/L. Higher concentrations were recorded during the winter turnover phase when bottom and surface waters mixed. Concentration above 0.01 mg/L can cause eutrophication of the water bodies. Total ammonia nitrogen (TAN) ranged from 0.015 - 6.480 mg/L. Higher concentrations were recorded during summer when temperatures were high and depths were low. TAN can be toxic to fish when the pH and temperature are high. The generally low least square means (LSM) for TAN were indicative of minor environmental impact of trout farming operations conducted during the colder, winter rainfall months. Trout farming coincided with conditions where the water temperatures were low, dam levels were high and dams were overflowing. The difference in bottom and surface water quality of reservoirs and the site location were found to be more important than the absence or presence of fish farming. The difference in bottom and surface water is directly linked to the ecological status of the sediment, which serve as nutrient sinks. In monomictic dams found in Mediterranean areas, mixing occurs during the winter turnover phase. Nutrients are released due to surface and bottom water mixing, brought about by torrential rains and wind turbulence. The concentration of organic material in the sediment and bottom waters is a function of the nutrient loading over time, irrespective whether the non-point sources were fish farming or agricultural activities and therefore it is difficult to partition causes and effects. In cases where reservoirs were already eutrophic due to past agricultural practices, implementing aquaculture could exacerbate the poor water quality status of the reservoir. There was a statistically significant difference between fish farming and non-fish farming for phosphorous, Secchi disc, total suspended solids and nitrite-nitrogen (p<0.05) and no statistically significant difference between fish farming and non-fish farming for dissolved oxygen, total ammonia nitrogen and nitrate-nitrogen (p>0.05). There was a statistically significant difference between surface and bottom waters for P and TAN (p<0.05). One reason for higher P and TAN concentrations in bottom waters is the accumulation of both in the sediment and subsequent release in the water column when the water mixes. A two-dimensional scatter plot was generated using the score for the first two principal components. The first two principal components accounts for 40 and 17 % of the total variance respectively, and the two groups of fish farming and non-fish farming did not separate well based on the first two principal components. The occurrence and distribution of phytoplankton biomass fluctuated with dam water levels and nutrient concentrations. The prevailing phytoplankton communities are important to fish farmers for two reasons: 1. It leads to fluctuations in dissolved oxygen concentrations via users (respiration and decomposition) and producers (photosynthesis). 2. It could lead to algal taint of fish flesh when geosmin-producing phytoplankton species are present. The frequency of occurrence indicated that the Group Chlorophyta (including genera, Chlamydomonas, Closterium, Oocystis, Scenedesmus, Staurastrum, Tetraedron, etc) had the most occurrences (n=371) with Chrysophyta (including genera, Dinobryon, Mallomonas, Synura, etc) the least (n=34). There was a statistically significant difference between genera occurrence and season (p<0.05). The geographical location of sites had no significance influence on the frequency of phytoplankton occurrence. There was no direct link between water quality and production yield (p>0.05). The fish yield of farms were linked mainly to the quality of fingerlings and the feed conversion ratio (FCR) achieved (p<0.05). Land-use patterns in the catchment where fish farming dams were located have shown that the dams are multiple-used systems. The ecological integrity of the farm dam ecosystem is dependent on the base volume. The dam is primarily for irrigation and fish farming can be compromised when higher demand for water is required during the dry season. The dams receive about 20 % of its water from rainfall and the rest from runoffs. Farmers could not provide accurate extraction rates making it difficult to predict water levels for future fish production. Four potential mitigation measures to reduce nutrient loading were described namely, feed management (quantity, frequency, type, etc.), feeding method (demand feeders, hand feeding), feed ingredients (formulation) and floating gardens. Both feed management procedures and demand feeders were evaluated as to the efficiency of reducing feed wastage and optimising FCR’s. The small-scale fish farmers were producing approximately 6 tons and had an average FCR of 1.96:1 ± 1.15. If farmers could improve their FCR’s by 0.1 (i.e. from 1.96 to 1.86), it would translate into a reduction of 100 kg feed for every ton of fish produced and result in 5% decrease in nutrient loading. The results of the water analysis and visual assessment of faecal length and colour showed no statistically significant difference between treatments for the guar-gum based binder (p>0.05). In addition, the level of binder did not influence digestibility of the experimental diets. The floating garden study indicated that it was feasible to construct a low cost raft system that is easy to manage and can produce plant crops as a hydroponic system in conjunction with fish farming cages. The lettuces grown on farm dam water provided support for the premise that the water quality can be improved via extraction of nutrients for crop production. For the production of 3.5 kg/m2 lettuce, a ratio of 1.09 plants/fish equal to 1.84 g feed/day/plant would reduce the accumulation of soluble nutrients around floating net cage farming system. The socio-economic evaluation of the contribution of fish farming to the welfare of rural and peri-urban farming communities supported the notion that aquaculture can lead to the upliftment of participating communities. Seventy-one percent (71%) of the respondents indicated that their motivation for exploring aquaculture is to supply fish to the wholesale market in order to generate income. Sixty-one percent (61%) of the respondents conducted the sales themselves or co-opted family members to assist them. The contribution of aquaculture provided direct benefits through improvement in household income, subsistence food supply and skills development. Indirect benefits included providing an information hub for other emerging farmers, elevation of the fish farmer’s status in the community through greater wealth and knowledge creation and promoting sector diversification through new products and technology. The three main constraints to the promotion and growth of aquaculture were listed as lack of government support, insufficient market intelligence and access, and limited choice in the availability of suitable candidate aquaculture species. Irrigation reservoirs in the WCP have a history of enrichment through external sources supplying water via agricultural runoff (fertilisers and pesticides), catchment runoff (leaf litter and organic debris) and stormwater effluent (grey and black water). The incorporation of aquaculture into such dams adds extra nutrients to the water column and management is crucial to limit the nutrient loading and ensure environmental sustainability. Such an approach will ensure that commercial land-based crop farmers’ irrigation regime and water distribution operations would not be negatively affected. Therefore future research needs should focus on; firstly the prevention and minimisation of pollution deriving from aquaculture through improved production management and technology transfer, secondly the monitoring and evaluation of the catchment ecosystem as a continuum with all the external factors affecting the ecology of farm dams and thirdly, evaluating the sediment processes and dynamics as sinks for nutrient accumulation. / AFRIKAANSE OPSOMMING: Akwakultuur het getoon dat dit ‘n lewensvatbare inisiatief is vir meerdoelige-gebruik van besproeiingsdamme (ook genoem plaasdamme) in die Wes-Kaap provinsie (WKP) van Suid-Afrika. Vele studies het bewys dat die geskiktheid-vir-gebruik van die reservoirs haalbaar is vir beide visproduksie sowel as besproeiing van landbougewasse. Nieteenstaande, die beoefening van intensiewe visboerdery in bestaande buitelug watersisteme kan lei tot ‘n toename in nutriëntvlakke van die water as gevolg van organiese belading afkomstig van ongevrete voere en metaboliese afvalstowwe van die vis. Onder sulke omstandigthede kan die primêre- (besproeiing) en die sekondêre (drinkwater en rekreasie) gebruik van die dam in gedrang kom weens ‘n afname in waterkwaliteit. Reënboogforel (Oncorhynchus mykiss) boerdery word beoefen in die omliggende Mediterreense klimaat van die WKP. Die tipe klimaat verskaf kort produksie-seisoene met wisselvallige water kwaliteit en kwantiteit. Die studie het die dinamika van water se fisies-chemiese parameters ondersoek en het die impak van forelboerdery op besproeiingdamme oor die langtermyn beskryf. Verder het die studie die geassosieerde landgebruik in die opvangsgebied met geïntegreerde akwa-landbou sisteme beskryf, asook moontlike toetrede (mitigasie maatreëls) geëvalueer wat die impak moontlik kan verlaag. Die ondersoek is afgesluit deur die bydrae wat akwakultuur lewer aan landelike en semi-stedelike gebiede, te beskryf. Die hoofdoel is die daarstelling van ‘n geïntegreerde, sosio-ekologiese gebalanseerde sisteem vir besproeiingdamme met gesamentlike akwakultuuraktiwiteite. ‘n Totaal van 35 besproeiingsdamme, insluitend die met visboerdery en nie-visboerdery, is gekies as navorsingspersele. Dit is hoofsaaklik geleë in drie geografiese gebiede naamlik, Overberg (Grabouw/Caledon), Boland (Stellenbosch/Franschhoek) en Breederivier (Ceres/Worcester). Die reservoirs is almal < 20 ha in oppervlakarea en die volumes het gewissel van 300 000 – 1 500 000 m3. Watermonsters is maandeliks sowel as seisoenaal versamel vir die onderskeie ondersoeke en ontleed vir ‘n reeks van parameters, insluitend: sigbaarheid (Secchi disc), temperatuur, opgeloste suurstof (OS), pH, natrium (Na), kalium (K), kalsium (Ca), magnesium (Mg), yster (Fe), chloor (Cl), karbonaat (CO3), bikarbonaat (HCO3), mangaan (Mn), koper (Cu), sink (Zn), boor (B), totale fosfor (TP), ortofosfaat (PO4), totale ammoniak stikstof (TAN), nitraat-stikstof (NO3-N), nitriet-stikstof (NO2-N), aluminium (Al), totale gesuspendeerde vaste stowwe (TGV), totale opgeloste vaste stowwe (TOV), alkaliniteit, hardheid en sulfate. Phytoplanktonmonsters is ook versamel, genera geïdentifiseer en die biomassa bepaal. Die waterkwaliteitsdata is ontleed in terme van oppervlak- en bodemstrata vir beide visboerdery en nie-visboerdery reservoirs en was gebaseer op herhaalde metings by dieselfde perseel op verskillende tye deur gebruik te maak van die Algemene Liniêre Model van Statistiese Analitiese Sisteem (SAS, 2012). Waardes p<0.05 is oorweeg as statisties beduidend. ‘n Hoofkomponentanalise bi-stipping (HKA) is toegepas om die persele en veranderlikes grafies voor te stel en te bepaal of die visboerdery en nie-visboerdery s’n enige groeperinge vorm asook hoe die persele assosieer met die veranderlikes. Gestruktureerde vraelyste en informele besprekings is onderneem om inligting in te samel op watergebruik, produksie-data, en die sosio-ekonomiese invloed wat akwakultuur bied aan visboere. Kategoriese data wat deur die onderhoude (21 akwakultuurprojekte) ingesamel is, is ontleed vir die frekwensie van aanwesigheid deur die gebruik van Statistiese Produk en Dienste-oplossings (SPDO) rekenaarprogram (SPSS Systems for Windows, Version 12.0). Die resultate vir die verskeie ondersoeke is beskryf en saamgestel in publikasie-vorm met die navorsingshoofstukke wat gefokus het op die areas van waterkwaliteitsimpak, opvangsgebied landgebruik, toetrede-meganismes en die bydrae van akwakultuur. Die resultate vir die waterkwaliteitsanalises het getoon dat gesamentlik die reservoirs se oorhoofse minimum, gemiddelde en maksimum waardes vir die verskillende fisies-chemiese parameters geskik is vir forelboerdery. Die diepte van die reservoirs het gewissel van 1.2 - 21.6 m, met die laagste waarde aangeteken gedurende die somermaande. Waardes laer as 5.0 m kan bestuursprobleme vir drywende hokstelsels versoorsaak want ‘n minimum van tenminste 4.0 m vrye spasie onder die hokke word benodig vir voldoende laterale vloei. Die Secchi-skyf lesing (sigbaarheid) van die reservoirs het gewissel van 10 – 510 cm. Hoër sigbaarheidswaardes is aangeteken na winterreëns wanneer sand-, slik- en klei deeltjies uitgesak het. Forel voer op sig en sigbaarheid van > 50 cm word benodig om goeie voeding te handhaaf. Die OS het gewissel van 0.3 – 16.4 mg/L met waardes onder 5 mg/L aangeteken gedurende somer wanneer wateronttrekking en temperature hoog was. Dit het gelei tot ongunstige toestande vir forelboerdery. Die situasie swaai om met die begin van winter wanneer die damme vol reën en die OS bo 5 mg/L styg soos benodig vir forelboerdery. Die P-vlakke het gewissel van 0.001 – 0.735 mg/L. Hoër waardes is aangeteken gedurende die winteromkeerfase wanneer die bodem en oppervlak se water meng. Konsentrasies bo 0.01 mg/L kan tot eutrofikasie van watersisteme lei. TAS het gewissel van 0-015 – 6.480 mg/L. Hoër konsentrasies is aangeteken gedurende die somer wanneer temperature hoog is en damvlakke laag. By hoë pH’s en temperature kan TAS toksies wees vir vis. The algemene lae kleinste kwadaat gemiddelde (KKG) waarde vir TAS het getoon dat daar ‘n klein impak op die omgewing was wanneer forelboerdery bedryf word gedurende die koue, winter reënvalmaande. Forelboerdery val saam met omstandigthede wanneer die watertemperature laag is, damvlakke hoog en die reservoirs oorloop. Die verskil in die bodem- en oppervlak water in die besproeiingsdamme en die ligging van die perseel is vasgestel om meer belangrik te wees as die teenwoordigheid of afwesigheid van visboerdery. Die verskil in die bodem en oppervlak is toe te skryf aan die toestand van die sediment waar nutriënte kan opgaar. In monomiktiese damme soos gevind in Mediterreende areas, vind vermenging plaas gedurende die winteromkeerfase. Nutriënte word vrygestel a.g.v. die vermenging van die oppervlak en bodem se water wat dan veroorsaak word deur harde reën en windturbulensie. Die konsentrasie van organiese materiaal in die sediment en bodem water is ‘n funksie van die nutriëntlading met tyd, ongeag of dit afkomstig was vanaf visboerdery of landbou-aktiwiteite. Dit is dus moelik om die spesifieke oorsaak van besoedeling af te baken. In gevalle waar die reservoirs alreeds eutrofies is a.g.v. aangewese landbouaktiwiteite, kan die toestand van die waterbron vererger indien akwakultuur toegepas word. Daar is ‘n statistiese noemenswaardige verskil tussen visboerdery en nie-visboerdery vir P, Secchi-skyf, totale gesuspendeerde vaste stowwe en nitrite-stikstof (p<0.05), en geen statistiese noemenswaardige verskil tussen visboerdery en nie-visboerdery vir OS, TAS en nitraat-stikstof (p>0.05). Daar is ‘n statistiese noemenswaardige verskil tussen oppervlak- en bodem water vir P en TAS (p<0.05). Een moontlike rede vir hoër P en TAS konsentrasies in die bodemwater, is die akkumulasie van beide parameters in die sediment en gevolglike vrystelling in die waterkolom wanneer die water gemeng word. ‘n Twee dimensionele spreidingstipping is geprodueer deur die waardes te gebruik van die eerste twee hoofkomponente. Die eerste twee hoofkomponente dra by 40 % en 17 % van die totale variansie onderskeidelik, en die twee groepering van visboerdery en nie-visboerdery het nie duidelik getoon nie. Die voorkoms en verspreiding van phytoplankton biomassa het gewissel met die verandering in damvlakke en nutriëntkonsentrasies. Die aanwesige phytoplanktongemeenskappe is belangrik vir die visboer vir twee redes: 1. Dit kan wisselende OS-vlakke versoorsaak deur die verbruik (respirasie en dekomposisie) en produksie (fotosintese) daarvan. 2. Dit kan lei tot alge na-smake van vis wanneer geosmin-produserende phytoplankton spesies aanwesig is. The frekwensie van voorkoms het getoon dat die Groep Chlorophyta (insluitend die genera, Chlamydomonas, Closterium, Oocystis, Scenedesmus, Staurastrum, Tetraedron, ens.) die meeste voorkom (n=371), met Chrysophyta (insluitend die genera, Dinobryon, Mallomonas, Synura, ens.) die minste (n=34). Daar is ‘n statistiese noemenswaardige verskil tussen genera voorkoms en seisoen (p<0.05) vir phytoplankton. Die geografiese ligging van die perseel het geen noemenswaardige invloed op die frekwensie van phytoplankton voorkoms nie. Daar is geen statistiese noemenswaardige verbintenis tussen waterkwaliteit en visproduksieopbrengste nie (p>0.05). Die visopbrengste by plase is hofsaaklik afhangende van die kwaliteit van die vingerlinge en die voeromsettingsverhouding (VOV) wat bereik is (p<0.05). Die landgebruikspatrone in die opvangsgebied waar visboere gesetel is, het aangedui dat die besproeiingsdamme meeldoelige sisteme is. Die ekologiese integriteit van die plaasdam-ekosisteem is afhanklik van die basisvolume. Die dam is hoofsaaklik daar vir die besproeiing en visboerdery kan in gedrang kom wanneer daar ‘n hoër aanvraag vir water gedurende die droë seisoen is. Die damme het omtrent 20 % van die water vanaf reënval ontvang en die res van aflope. Boere kon nie akkurate inligting verskaf van waterontrekking nie wat dit moeilik gemaak het om te voorspel wat die beskikbare watervlakke in die toekoms sou wees vir visproduksie. Vier potensiële toetrede meganismes om die nutriëntlading te verminder, is beskryf naamlik voedingsbestuur, (kwantiteit, frekwensie, tipe, ens.) voermetodes (aanvraagvoeder, handvoeding), voerbestandele (formulasies) en drywende tuine. Beide voedingsbestuur prosedure en aanvraagvoeders is geëvalueer as ‘n metode om die voervermorsing te verminder en die VOV te verbeter. Die kleinskaalse visboere het ongeveer 6 ton produseer met ‘n gemiddelde VOV van 1.96:1 ± 1.15. Indien die visboere hul VOV’s met 0.1 kan verbeter (bv. van 1.96 tot 1.86), sal dit beteken dat daar ‘n vermindering van 100 kg voer bewerkstellig word vir elke ton vis geproduseer. Dit kan ook lei tot ‘n vermindering van 5 % in die nutriëntlading. Die resultate van die wateranalises en die visuele waarneming van faeceslengte en kleur het geen statistiese noemenswaardige verskil tussen die behandelinge vir die guar-gom binder getoon nie (p>0.05). Verder, die hoeveelheid van die binder het nie die vertering van die eksperimentele diëte beïnvloed nie. Die studie op die drywende tuine het getoon dat dit haalbaar is om ‘n lae-koste sisteem te bou wat maklik is om te bestuur en gewasse kan produseer soos in ‘n hidroponiese sisteem tesame met visproduserende hokstelsels. Die kropslaaie se groei het getoon dat die waterkwaliteit van besproeiingsdamme kan verbeter word deur die opname van nutriënte wanneer plante verbou word. Vir die produksie van 3.5 kg/m2 kropslaaie, sal ‘n verhouding van 1.09 plante/vis of 1.84 g voer/dag/plant die akkumulasie van opgeloste nutriënte rondom die hokstelsels verminder. Die sosio-ekonomiese evaluasie van die bydrae van visboerdery tot die welvaart van die landelike en semistedelike plaasgemeenskappe ondersteun die feit dat akwakultuur verbetering kan bewerkstellig, veral onder deelnemende gemeenskappe. Een-en sewentig persent (71 %) van die respondente het getoon dat hul oorweging vir die bedryf van akwakultuur is om vis te voorsien aan die grootmark en daarvolgens geld te maak. Een-en-sestig persent (61 %) van die respondente het aangedui dat hulself die vis verkoop of vir familie-lede vra om met die verkope te help. Die bydrae van akwakultuur het direkte voordele aan die deelmers voorsien deur ‘n verbetering in huishoudelike inkomste, voedselvoorsiening vir selfgebruik en die ontwikkeling van vaardigthede. Indirekte voordele sluit in dat die deelmers ‘n bron van inligting geword het vir opkomende boere, hul status in die gemeenskap het verbeter omdat hul kennis verbreed het en dit het verder gelei tot diversifisering in die sektor a.g.v. die skepping van nuwe produkte en tegnologie. Die drie hoof struikelblokke wat die groei en bevordering van akwakultuur belemmer is o.a., ‘n tekort aan staatsondersteuning, onvoldoende markinligting en toegang en ‘n beperkte keuse in spesies vir boerdery. Besproeiingsdamme in die WKP het ‘n geskiedenis van verryking deur eksterne bronne wat water voorsien vanaf landbou-afloop (bemestingstowwe en pesbestrydingsmiddels), opvangsgebied-afloop (blare en ander organiese debris) en stormwateruitlaat (gruis- en swart water). Die implementering van akwakultuur in sulke damme voeg addisionele nutriënte tot die waterkolom en bestuur is krities om die lading te verminder en te verseker dat omgewingsvolhoubaarheid behou word. Indien die regte praktyke en bestuur toegepas word, sal dit beteken dat die kommersiële boer se besproeiing en waterverspreiding nie negatief beïnvloed word nie. Vervolgens moet toekomstige navosingsbehoeftes fokus op eerstens, die voorkoming en vemindering van besoedeling afkomstig van akwakultuur deur verbeterde produksie-bestuur en tegnologie-oordrag, tweedens, die monitoring en evaluering van die opvangs-ekosisteem as ‘n kontinuum met al die eksterne faktore wat die ekologie van die plaasdam kan beïnvloed en laastens, die ondersoek en evaluering van die sediment se prosesse en dinamika as ‘n sisteem wat nutriënte ophoop.

Thesis (MScAgric )--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Pine pitch canker, caused by Fusarium circinatum, is a major constraint to the production of high quality timber in the Western Cape Province of South Africa. Under nursery conditions the pathogen causes a serious root and collar rot disease, and in plantations it causes stem cankers and branch die-back. In this thesis, sources of inoculum within a forestry nursery were investigated and novel approaches developed to eradicate the pathogen. Plant material was evaluated for plantation establishment in the Western Cape Province, and epidemiological studies conducted to better understand the infection, disease development, spore release and dissemination of F. circinatum in pine plantations. Fusarium circinatum was first reported in a forestry nursery in the Mpumalanga Province of South Africa in 1990, and now causes significant economic losses to most forestry nurseries in the country. The irrigation system, planting tray inserts, seeds and air at Karatara nursery were screened as potential sources of F. circinatum. Both the irrigation water and planting tray inserts were found to serve as sources of inoculum. An oxidation reduction potential (ORP)-based system, using hydrogen peroxide, was tested to sanitize irrigation water and planting tray inserts. An ORP level of 400 mV for 6 hours was effective in killing F. circinatum spores in irrigation water without being phytotoxic to pine seedlings. An ORP value of >500 mV cleaned planting tray inserts of all inoculum. Pinus radiata is the principal pine species grown in the Western Cape Province, but this species is also highly susceptible to F. circinatum. There are numerous different varieties or families of P. radiata available that can be planted, and it is known that tolerance levels between these varieties and families vary. Pinus radiata families, as well as other Pinus spp. that could potentially be planted in the Western Cape Province in future, were evaluated for tolerance to the pitch canker fungus. The P. radiata families were moderately to highly susceptible to F. circinatum. Pinus taeda was the Pinus spp. most tolerant, while P. elliottii also had good tolerance to the pathogen. None of the P. radiata families screened showed tolerance comparable to that of either P. elliottii or P. taeda. Pine pitch canker was first reported from the Tokai plantation in the Western Cape Province in 2005. In order to develop a disease management strategy for the disease in pine plantations, we investigated the effect of pruning wounds as potential entry sites for the pathogen, and how fast the disease spread under South African climatic conditions. The amount and time of sporulation was also investigated. Pitch canker increased slowly over a 3-year period, and pruning wounds appeared not to serve as primary entry points for F. circinatum. Spore quantification over a 12-month period using quantitative real-time PCR showed that inoculum was produced throughout the year, but that significantly more spores were released during the cold, rainy winter months. The role of insects in pathogen transmission and spread should be investigated in the Tokai plantation. / AFRIKAANSE OPSOMMING: Fusarium circinatum veroorsaak “pine pitch canker”. Hierdie siekte is een van die grootste beperkinge op die Suid Afrikaanse bosbou industrie. In kwekerye veroorsaak die patogeen wortelvrot en wortelkraagvrot. In plantasies veroorsaak F. circinatum kankers op die hoofstam van dennebome en die terugsterwing van sytakke. In hierdie tesis was bronne van inokulum in ‘n bosbou kwekery ondersoek. Nuwe tegnieke was gebruik om die bronne uit te wis. Plantmateriaal wat in die Wes-Kaap geplant kan word, was geëvalueer vir toleransie teen F. circinatum. Epidemiologiesie studies was uitgevoer om die infeksieproses, siekte-ontwikkeling, spoorvrystelling, en verspreiding van F. circinatum binne denneplantasies beter te verstaan. Die eerste verslag van F. circinatum in ‘n bosboukwekery was in 1990 in die Mpumalanga Provinsie. Verliese word tans veroorsaak deur die patogeen in die meeste bosbou kwekerye in Suid Afrika. Die besproeiingstelsel, planthouers en saad was getoets as potensiële bronne van inokulum. Daar was gevind dat beide die besproeiingstelsel en die planthouers dien as bronne van F. circinatum inokulum. ‘n Oksidasie reduksie potensiaal (ORP)-gebaseerde sisteem waar waterstofperoksied gebruik was, was getoets of dit die besproeingwater en planthouers kan ontsmet. ‘n ORP-vlak van 400 mV vir ‘n blootstellingstydperk van 6 ure is effektief om al die F. circinatum spore dood te maak, sonder dat dit fitotoksies is teenoor die dennesaailinge. ‘n ORP-vlak van >500 mV het die F. circinatum in die planthouers uitgewis. Pinus radiata is die belangrikste dennespesie wat geplant word in die Wes-Kaap Provinsie, maar hierdie spesie is hoogs vatbaar vir F. circinatum. Verskillende variteite van P. radiata met verskillende tolleransie vlakke bestaan. Pinus radiata families en ander spesies wat in die toekoms potensieel geplant kan word in die Wes-Kaap was geevalueer vir toleransie teen F. circinatum. Die P. radiata families was matig to hoogs vatbaar vir F. circinatum. Pinus taeda het die hoogste toleransie vlak gehad en P. elliottii was matig tolererant. Nie een van die P. radiata families wat getoets was het toleransie vlakke gehad wat vergelykbaar was met die toleransie vlakke van P. taeda of P. elliottii nie. In 2005 was F. circinatum vir die eerste keer geraporteer in die Tokai plantasie op volwasse dennebome in die Wes-Kaap Provinsie. Die rol van snoeiwonde in die infeksieproses van F. circinatum was bestudeer asook hoe vinning die siekte ontwikkel en versprei. Die hoeveelheid en tyd van sporulasie was ook bestudeer. “Pitch canker” het stadig toegeneem oor die 3-jaar moniteringsperiode en dit blyk asof snoeiwonde nie die primêre ingangspunt vir die patogeen is nie. Kwantifisering van die sporulasie van F. circinatum deur middel van qPCR het aangedui dat spore reg deur die jaar geproduseer word. Meer spore word geproduseer in die koue nat wintersmaande. Die rol van insekte in die infeksieproses en verspreiding van F. circinatum in die Tokai plantasie moet ondersoek word.

The seasonality of wild caught Cape mole-rats was investigated, focusing on endocrine, neuroendocrine and neuroanatomical parameters. The Cape mole-rat reproduces only during the winter rainfall period of the western Cape Province. Interestingly, the gonadal steroid hormones do not show any significant seasonal patterns in either males or females. In addition, the pituitary does not exhibit a reduced sensitivity to GnRH stimulation during the non-breeding season in either sex. Moreover, in the brain the distribution, number and size of GnRH perikarya do not differ with respect to season. Therefore, although only producing young during a specific period of the year, the Cape mole-rat does not appear to be physiologically repressed from reproducing throughout the year. The results of this study imply that the Cape mole-rat is an opportunistic breeder that is reproductively quiescent during the dry season as a consequence of ecological factors such as lack of favourable burrowing conditions and that when opportunities avail themselves following aseasonal rainfall, reproduction may occur. The seasonality and socially induced infertility of the Natal mole-rat was examined via endocrine, neuroendocrine and neuroanatomical investigations. In contrast with the phylogenetically closely related common mole-rat and highveld mole-rat, the Natal mole-rat does not appear to breed seasonally. Post-mortem examination of animals collected revealed pregnant reproductive females throughout the year. A similar scenario is reflected in gonadal steroid concentrations, with no major seasonal differences observed in either males or females. Likewise, pituitary sensitivity to GnRH does not change over season in males or females, and all neuroanatomical parameters investigated remained stable over season in both males and females. Natal mole-rats captured for this study occur in an area with a high annual rainfall, (almost double that of the common mole-rat habitat and one and a half times that of the highveld mole-rat) and the relatively higher rainfall and hence soil moisture content may provide the Natal mole-rat with increased foraging time a result of increased periods over which the soil is optimal for burrowing. Socially induced infertility in the Natal mole-rat appears to be enforced behaviourally as a result of active incest avoidance. The circulating testosterone concentrations were not significantly different in reproductive and non-reproductive males, and likewise oestrogen concentrations did not differ between reproductive and non-reproductive females. Progesterone concentrations were very low in subordinate females, but markedly higher in reproductive females. This is not surprising since the Natal mole-rat is an induced ovulator, thus coitus is required to induce the LH surge that stimulates ovulation. The sensitivity of the pituitary to a GnRH challenge did not differ between reproductive and non-reproductive animals from either sex. No neuroanatomical differences were observed between reproductive and non-reproductive animals of either sex, however, non-reproductive males and females had significantly higher amounts of GnRH in the median eminence, implying that GnRH is synthesized and transported to the median eminence but not released in the portal system to the anterior pituitary. These findings suggest that non-reproductive animals of both sexes are not sterile, but merely sexually quiescent. Copyright / Thesis (PhD)--University of Pretoria, 2008. / Zoology and Entomology / unrestricted