This thesis traces the history of the abalone fisheries on the California Coast and how those fisheries have been understood and shaped by humans over time. An overarching interest that guides this effort is how indigenous populations used abalone and otters (as well as other marine resources) purposefully for millennia prior to European arrival. However, this work is not entirely focused on prehistory. Instead, it shows how a lack of understanding of this prehistory shaped the conservation efforts of the California Department of Fish and Game and its ultimate decision to close the commercial fishery in 1997. In this sense, there is a layer of this thesis that takes on the form of an institutional history of the California Department of Fish and Game, but it does so as a model of how management practices were developed and implemented during the twentieth century. In this frame, this thesis in also a history of twentieth century ecological and scientific practices that historicizes the closure of the commercial abalone fishery in 1997.

Thesis (MSc(Agric))--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: The pnmary alm of this study was to investigate the national competitive advantage of the South African abalone industry. A further aim was therefore to investigate the environment, in which the South-African abalone industry operates. Secondary aims included presenting a detailed description of the roleplayers in the South African abalone industry, and considering whether the South African abalone industry can be made more competitive and, if so, how this can be achieved. The achievement of these aims required a framework to establish which data is necessary for the task. The framework selected involved a combination of Porter's Five Forces analysis and Diamond Model. The study suggests that South African abalone firms should promote South African abalone more actively, invest more funds in human resources, and that the industry's faith in government needs to be restored, which can be achieved by improving the services offered by public institutions like the South African Bureau of Standards (SABS), the Department of Trade and Industry (DTI) and Marine and Coastal Management (M&CM). / AFRIKAANSE OPSOMMING: Die doel met die studie was om die nasionale kompeterende voordeel van die Suid Afrikaanse perlemoen industrie te ondersoek. Om dit te bereik, moes die omgewing waarin die industrie fuksioneer ontleed en die rolspelers in die industrie deeglik beskryf word. 'n Verdere doel was om te bepaal of dit moontlik is om die kompeterendheid van die industrie te verhoog, en indien wel, hoe dit bereik kan word. Die raamwerk wat gekies is om die doelstellings te bereik bestaan uit 'n kombinasie van Porter se "Five Farces" analise en "Diamond Model". Die resultate dui aan dat die industrie Suid-Afrikaanse perlemoen meer aktief moet bekendstel, individuele ondernemings meer in hul menslike hulpbronne moet investeer, en dat die industrie se vertroue in die nasionale regering herstel moet word, deur die dienste te verbeter wat deur publieke instellings soos die Suid-Afrikaanse Buro van Stanaarde (SABS), Departement Handel en Nywerheid en Mariene- en Kusbestuur verskaf word.

Thesis (MSc (Genetics))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The South African abalone, Haliotis midae, is the only endemic species of commercial value. Aquaculture remains the only avenue for expanding the industry, since the closure of the fishery. The current focus is on implementing a molecular breeding programme; thus the development of molecular markers for linkage mapping and QTL analysis is a priority. Various markers, mainly anonymous, have been developed for H. midae; however emphasis is being placed on the development of gene-linked type I molecular markers. The present study investigates and demonstrates the use of public sequence collections to develop type I markers for a species with limited genomic resources, via three strategies: Surveying anonymous H. midae microsatellite markers’ flanking regions to find homology to gene sequences in public databases, cross-species marker transfer of anonymous markers from H. rubra and H. discus hannai demonstrating putative gene associations and lastly EST marker mining (SNP and microsatellites) from various Haliotids and testing transfer to the target species. Approximately 17% of H. midae anonymous markers showed significant similarity to genes. The current study also reports higher cross-species transferability from both H. rubra and H. discus hannai to H. midae (39% and 20.5%, respectively) than previously demonstrated and 15 EST-microsatellites and 16 EST-SNPs were successfully mined. Furthermore, the non-random distribution of microsatellites and high nucleotide diversity in the H. midae genome was confirmed. This is a low cost and time effective method for marker development and presents a continuous and dynamic resource that could be used for future marker development and characterisation as sequence information in public databases grow exponentially. / AFRIKAANSE OPSOMMING: Die Suid-Afrikaanse perlemoen, Haliotis midae, is die enigste van vyf inheemse spesies van kommersiële waarde. Na die noodgedwonge sluiting van die vissery, is akwakultuur die mees praktiese oplossing om die perlemoen industrie uit te brei. Die huidige fokus is gerig op die implementering van ‘n molekulêre teel-program en dus is die ontwikkeling van molekulêre merkers vir genetiese kartering en kwantitatiewe kenmerk lokus analise, van uiterste belang. Tipe II merkers is voorheen vir die perlemoen ontwikkel, maar huidige tendense lê klem op die ontwikkeling van geen-gekoppelde tipe I merkers. Die huidige studie ondersoek die gebruik van publieke databasisse vir die ontwikkeling van tipe I molekulêre merkers vir ‘n spesie met beperkte genomiese bronne. Drie strategieë is geïmplementeer: Eerstens is ‘n opname gemaak van die homologie van perlemoen tipe II merker-vleuelende volgordes met geen volgordes in databasisse. Verder is die oordraagbaarheid van tipe II merkers vanaf H. rubra en H. discus hannai wat assosiasie met gene toon ondersoek. Laastens is ‘n Uitgedrukte Volgorde Merk (UVM) (Expressed Sequence Tag, EST) merker-ontginnings metode vanaf verskeie Haliotis spesies en toetsing van oordraagbaarheid na die teiken spesie uitgevoer. Ongeveer 17% van die tipe II H. midae merkers het geniese assosiasie getoon. ‘n Hoër tussen-spesie oordraagbaarheid vanaf beide H. rubra en H. discus hannai na H. midae (39% en 20.5%, onderskeidelik) word gerapporteer in vergelyking met vorige studies en 15 UVM-mikrosatelliete en 16 UVM-enkel nukleotied polimorfismes (single nucleotide polimorphism, SNP) is ontwikkel. Verder bevestig die studie die nie-lukrake verspreiding van mikrosatelliete en hoë nukleotied diversiteit in die perlemoen genoom. Die gebruik van publieke databasise vir die ontwikkeling en karakterisering van tipe I molekulêre merkers is tyd- en koste-besparend en bied ‘n volgehoue en dinamiese bron vir toekomstige gebruik.

Thesis (MSc)--Stellenbosch University, 2002. / ENGLISH ABSTRACT: The species Haliotis midae is the only abalone species of commercial importance to the South African fisheries industry. The species is currently under substantial pressure due to commercial harvest and illegal poaching, to the extent that genetic and biodiversity may be under threat. The species is also being cultured in commercial systems for supply to international markets. The South African production for 2002 amounted to 350 tons. The commercial production of abalone may also have implications with regard to genetic diversity of natural and commercial populations. The aim of this project was to assess the genetic diversity of the natural and commercial populations of abalone at the I&J Abalone Farm, Danger Point, Gansbaai, in South Africa, in order to make recommendation with regard to possible impact on natural diversity as well as internal management systems. Distortion of natural genetic diversity or a loss of internal diversity will have detrimental consequences. Representative samples have been obtained from the surrounding natural population, as well as the commercial populations, including the broodstock and various progeny groups. Both mtDNA and AFLP molecular techniques were used to assess genetic diversity. Data analysis showed that the genetic profile of the commercial population display sufficient genetic variation. The genetic structure of the commercial population also displays no significant deviation from that of the surrounding natural population, i.e. the population of origin. The results through give indication of a small, though unsignificant loss of genetic variation from the broodstock to the subsequent progeny groups. The investigation conclude that the commercial populations of abalone at the I&J Abalone Farm, Danger Point, Gansbaai, in its current format holds no threat to the disruption of the genetic diversity of the surrounding natural population. Further, the commercial population possesses sufficient genetic variation in view of future genetic development. There is signs of a slight loss of genetic variation in the change over from the broodstock to the progeny groups. This would necessitate careful and controlled replacement of the original broodstock with new animals from the commercial progeny groups as part of an ongoing process of domestication. / AFRIKAANSE OPSOMMING: Die spesie Haliotis midae is die enigste perlemoen spesie van kommersiële belang vir Suid Afrikaanse visserye. Die spesie verkeer tans onder toenemende druk as gevolg van kommersiële en onwettige vangste, tot so 'n mate dat genetiese en biodiversiteit daardeur geaffekteer kan word. Die spesie word in toenemende mate kunsmatig gekweek vir voorsiening aan internasionale markte. Suid Afrikaanse produksie vir 2002 beloop reeds sowat 350 ton per jaar. Die kunsmatige produksie van perlemoen het ook moontlike implikasies op die genetiese diversiteit van natuurlike en kommersiële populasies van die perlemoen, Haliotis midae. Die doel van die projek was om die aard van genetiese diversiteit van die natuurlike en kommersiële populasies van perlemoen by die I&J Perlemoen Plaas, Danger Point, Gansbaai in Suid Afrika te ondersoek, ten einde aanbevelings te maak ten opsigte van moontlike impak op natuurlike diversiteit asook ten opsigte van interne genetiese bestuurstelsels. Versteuring van natuurlike diversiteit of verlies van interne diversiteit hou nadelige gevolge in. Verteenwoordigende monsters is versamel vanuit die omliggende natuurlike populasies, sowel as van die kommersiële populasie op die plaas, insluitend die teelmateriaal en verskillende nageslaggroepe. Beide mtDNA en AFLP-molekulêre tegnieke is gebruik tydens die ontleding van genetiese diversiteit. Dataontleding het aangetoon dat die genetiese profiel van die kommersiële populasie voldoende genetiese variasie demonstreer. Die genetiese struktuur van die kommersiële populasie toon verder geen betekenisvolle verskil met die omliggende natuurlike populasie nie, dit wil sê met die populasie van oorsprong nie. Die resultate toon verder 'n geringe, dog nie betekenisvolle verlies van genetiese variasie wat waargeneem word met oorgang van die teelmateriaal na die onderskeie nageslaggroepe. Die bevindinge van die ondersoek is dus dat die kommersiële populasie op die I&J Perlemoen Plaas, Danger Point, Gansbaai, in die huidige formaat, geen bedreiging inhou vir die versteuring van die omliggende natuurlike genetiese diversiteit nie. Verdere bevindinge is dat die kommersiële populasie oor voldoende genetiese diversiteit beskik met die oog op toekomstige genetiese ontwikkeling. Daar is tekens van 'n geringe afname in genetiese diversiteit met die oorgang vanaf die teelmateriaal na die nageslaggroepe. Dit beklemtoon die belang van 'n gekontroleerde vervanging van die oorspronklike teelmateriaal met nuwe teeldiere vanuit die kommersiële populasie as deel van die domestikasieproses.

Thesis (MScAgric)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: The aim of this study was to critically assess the implementation of the internal reference method within the most recent 173 full-sibling growth trial of the Innovation Fund Abalone Breeding Project. The trial was conducted over two locations for a period of five years, with minimal replication for the majority of test families and a single full-sibling family was entered into each experimental unit (basket) as an internal reference group. The primary focus was firstly, to validate the performance of the internal reference group as a control for comparisons and correction of environmental variation in test family performances. Secondly, to identify areas of weakness and either make recommendations to remedy areas of weakness or justify devoting resources to alternative methods of reducing extraneous environmental variance with limitations on replication. The efficiency and statistical power associated with utilising internal reference information as a covariate and for manual correction respectively were examined for the 6 full-sibling test families that were replicated. This study reports on the evaluation of factors which are potential sources of bias in the internal reference method, the first of which, tag loss, was found to be significant after 6- 12 months. However, it was not found to bias internal reference group performances as the factors which contribute to tag loss were found to act randomly. Variability in size ratio of internal reference to test family at co-stocking proved a significant source of bias, as reference groups smaller than their test family counterparts had reduced performances. Testing for genotype by environment interactions was precluded due to the inherent lack of replication and the subsequent confounding of genotype effects with inter-rearing structure effects at one of the locations. However, significant differences were detected for both traits of interest of the internal reference group over the two locations. Significant antagonistic interactions were detected and identified as a source of bias for average daily weight gain of replicate test families. The evaluation of average daily length gain for the efficiency of adjustment when the internal reference is a covariate and the change in statistical power when the internal reference is used for a manual correction, yielded conflicting results. The latter shows a decrease in statistical power and the former shows an increase in efficiency, both resulting in poor goodness of fit in the respective models. There was however evidence that when no antagonistic interactions occurred “between replicate variance” decreased and therefore the internal reference method has statistical merit provided all critical success factors are satisfied. Recommendations were made for future implementation of the internal reference method to facilitate adequate statistical testing for sources of bias and the prevention thereof. Additionally, an alternative method which may have merit in decreasing environmental variance and the need for replication, is discussed. / AFRIKAANSE OPSOMMING: Die doel van die studie was om die gebruik van ʼn interne verwysingsgroep te ontleed, soos toegepas tydens die evaluering van 173 volsib families as deel van die Innovasiefonds Perlemoen Teelprogram. Die evaluering is gedoen op twee lokaliteite oor 'n tydperk van vyf jaar, met minimale replikasie van die toets families en die gebruik van ‘n enkele volsib familie as 'n interne verwysingsgroep in elke eksperimentele eenheid (mandjie). Die primêre fokus was eerstens om die gebruik van die interne verwysingsgroep vir die korreksie van omgewingsvariasie in die toets familie optredes te evalueer. Tweedens, om spesifieke gebreke te identifiseer ten opsigte van die gebruik van die interne verwysingsgroep en aanbevelings maak dit reg te stel en om die meriete van alternatiewe metodes te oorweeg. Die doeltreffendheid en statistiese onderskeidingsvermoë van die gebruik van interne verwysingsgroep as 'n kovariaat is ondersoek met betrekking tot die 6 volsib groepe wat oor voldoende replikasies beskik het. Die studie doen voorts verslag oor die evaluering van potensiële oorsake van sydigheid ten opsigte van die gebruik van die interne verwysingsgroep, insluitend die beduidende verlies van identifikasie vanaf 6 tot 12 maande. Geen aanduiding van sydigheid is egter gevind en die aanleidende oorsake van verlies van identifikasie blyk van ʼn ewekansige aard te wees. Verskille in die grootte tussen die interne verwysingsgroep en toets-families met aanvang van evaluering blyk 'n belangrike bron van sydigheid te wees, waar die kleiner groepering aan verminderde prestasie gekoppel word. Bepaling van genotipe-omgewing-interaksies kon nie uitgevoer word nie as gevolg van die inherente gebrek van replisering oor lokaliteite. Beduidende verskille is egter waargeneem tussen interne verwysingsgroepe oor die twee lokasies ten opsigte van die beide groei eienskappe. Beduidende antagonistiese interaksies is waargeneem en geïdentifiseer as 'n bron van sydigheid ten opsigte van die gemiddelde daaglikse gewigstoename van replikaat toetsfamilies. Die evaluering van gemiddelde daaglikse lengtetoename met die interne verwysingsgroep as is 'n kovariaat en die verandering in statistiese ontledingsvermoë tydens die gebruik van die interne verwysingsgroep het teenstrydige resultate opgelewer. Laasgenoemde toon 'n afname in statistiese ontledingsvermoë en die eersgenoemde toon 'n toename in doeltreffendheid, met beide swak passing op die onderskeie modelle. In die afwesigheid van antagonistiese interaksies tussen replikasies het variansie afgeneem en beskik die interne verwysingsgroep oor die nodige statistiese meriete indien daar aan al die kritiese vereistes voldoen word. Aanbevelings is gemaak ten opsigte van die toekomstige implementering van die interne verwysingsmetode met verwysing na voldoende statistiese toetsing vir bronne van sydigheid en die voorkoming daarvan. 'n Verdere metode wat oor die nodige meriete beskik om die omgewingsvariasie en die noodsaaklikheid vir replikasie te verminder, word bespreek.

Thesis (MSc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Cultured abalone in South Africa is undomesticated. For the local industry to remain competitive on the international markets it is essential to improve production. This study is part of a selective breeding component of a larger genetic programme that aims to enhance productivity of the local industry by genetic improvement of growth rates. Selective breeding programmes are based on genetic variation and correlations. Molecular studies proved genetic differentiation exist between the broodstock- and offspring populations and among the offspring populations used in this study. Five commercial abalone farms from the Walker bay region each entered 3000 randomly selected animals obtained from synchronised mass spawning of conditioned broodstock into a Performance Recording Scheme (PRS). Microsatellite marker analysis proved these broodstock populations to be representative of the wild populations. The five cohorts were assessed over the five locations represented by three replicates per location with 200 randomly assigned animals per replicate. The average growth rate was used as growth performance parameter by measuring shell length and body weight at three month intervals over a period of 24 months. Interaction was observed between cohort and location effects when analysing the full data set. This was unexpected as the cohorts were constructed from parent stick that was randomly sampled from the same geographical area, the larger Walker bay. The factors suspected of causing this observed interaction were considered in a stepwise analysis. Initial and progressive tag loss, differences in initial size of animals entered into the study and on-farm management errors were considered as possible causes of the observed interaction in a stepwise analysis. Statistically significant differences were observed between the five cohorts and between the five locations in terms of length and weight growth rates. Based on these findings it is advised that a central facility is used to effectively compare the growth rates of different cohorts or populations. Any future research in selective breeding to follow this study should involve the integration of molecular techniques and biotechnologies. / AFRIKAANSE OPSOMMING: In Suid-Afrika is gekweekte perlemoen wild. Vir die plaaslike bedryf om op die internasionale markte kompeterend te bly, is dit noodsaaklik om produksie te verbeter. Hierdie studie vorm deel van ’n selektiewe telingskomponent van ‘n groter genetiese program met die doel om die produktiwiteit van die plaaslike bedryf deur die genetiese verbetering van groeitempo’s te verbeter. Selektiewe teelprogramme word gebaseer op genetiese variasie en korrelasies. Molekulêre studies het bewys dat daar genetiese differensiasie bestaan tussen die teel- en nageslagpopulasies en onder die nageslagpopulasies wat in hierdie studie gebruik is. Vyf kommersiële perlemoenplase in die Walkerbaaistreek het elk 3000 ewekansig geselekteerde diere vanaf gesinkroniseerde massa broei van gekondisioneerde teelpopulasies aan ‘n Performance Recording Scheme (PRS) bygedra. Mikrosatelliet merker-analise het bewys dat hierdie teelpopulasies verteenwoordigend is van die wilde populasies. Die vyf kohorte is oor die vyf liggings geassesseer, elkeen waarvan verteenwoordig is deur drie replikate bestaande uit 200 ewekansig toegedeelde diere per replikaat. Die gemiddelde groeitempo is gebruik as die groeiprestasieparameter deur skulplengte en liggaamsgewig elke drie maande oor ‘n tydperk van 24 maande te meet. Daar is interaksie waargeneem tussen kohort- en liggingseffekte toe die volledige datastel geanaliseer is. Hierdie was onverwags, aangesien die kohorte gekonstrueer is uit teelouers waarvan monsters ewekansig vanuit dieselfde geografiese gebied, naamlik die groter Walkerbaai, geneem is. Die faktore wat vermoedelik hierdie waargenome interaksie veroorsaak het, is in ‘n stapsgewyse analise beskou. Aanvanklike en progressiewe merkerverlies, verskille in die aanvanklike grootte van die diere wat in die studie ingesluit is en bestuursfoute op die plaas is as moontlike oorsake van die waargenome interaksie voorgestel. Statisties betekenisvolle verskille is tussen die vyf genotipes en tussen die vyf liggings in terme van lengte en gewigsgroeitempo’s waargeneem. Op grond van hierdie bevindings word daar voorgestel dat ‘n sentrale fasiliteit gebruik word om die groeitempo’s van die verskillende genotipes of populasies doeltreffend te vergelyk. Enige toekomstige navorsing oor selektiewe teelt wat op hierdie studie sou volg, moet die integrasie van molekulêre tegnieke en biotegnologieë behels.

The largest abalone in South Africa, the perlemoen, Haliotis midae, occurs along approximately two-thirds of the country's coastline, but has only been the target of an extensive commercial fishery in the south-western part of South Africa. Large-scale illegal fishing has however proliferated throughout its entire range over the last 10–15 years, which has had serious effects on stock abundance and once productive populations are facing economic collapse. Abalone stock enhancement has been put forward as an addition or alternative to traditional fisheries management practices, which can potentially rehabilitate overfished abalone populations and enhance natural production. The aim of this project was to investigate the potential of abalone stock enhancement for managing an area in the Eastern Cape Province, which was being subjected to intense illegal fishing pressure. A research approach was adopted to investigate the scale and effects of this poaching and to investigate the survival of artificially cultured abalone seed in the natural environment. A model of a commercial-scale ranching operation was investigated to assess the economic feasibility of such a scheme. Analysis of poaching cases and research samples from Cape Recife indicated high levels of fishing effort that appeared to be causing the observed declines in emergent abalone abundance and average size. Poaching cases from Cape Recife contributed 32% of the total number of cases of known origin in the Eastern Cape Province from 1998–2002, with the majority of the cases (82%) originating from within the Port Elizabeth metropole. There was an exponential increase in the number of poaching cases in the Eastern Cape Province (r²=0.967) and Port Elizabeth over this period but actual annual total catch stabilized, particularly at Cape Recife, where estimates of CPUE declined significantly from 2000–2002 (p<0.001). The annual proportion of emergent abalone under the MLS from Cape Recife was always >85% in confiscations and research collections, and did not change significantly over the period of examination. Comparison of illegal catches with an adjacent site indicated that the emergent abalone population at Cape Recife had a significantly higher proportion of undersized emergent animals (p<0.001) and they were significantly smaller than the abalone from the closest site, Noordhoek, and other areas in Port Elizabeth from 2000–2002 (p<0.001). The apparent declines in emergent abalone abundance indicated by the poaching data were corroborated by sampling of emergent abalone abundance at Cape Recife. Numbers of abalone declined significantly from 125.6 to 53.8 per 20min count (p<0.001), from April 1998–October 2001 and density declined from 1.3 to 0.8m⁻² over a similar period (p<0.001). Juvenile density did not change over this period, although there were significant differences in density observed between two different habitats (p<0.001). Initial releases of cultured juvenile abalone showed that they could be distinguished from their wild counterparts for at least a year after release, by their different shell colouration. Short-term, small-scale trials (7–10 days) using animals between 17 and 30mm SL had mean survival rates of 64–82% (mean 70.4%) and the effect of size on survival was not significant in most cases, although the power to detect differences was low. Attempts to measure the effect of habitat on survival were not conclusive, although refuges under sea urchins appeared to be favoured by both seed and wild abalone, although urchins were not an absolute requirement for survival. Similar medium-term trials (31–74 days) in sheltered sites yielded mean returns of 53.1% using 25mm SL animals and similar trials in a more exposed area had more variable survival rates of between 18.4 and 73.6%, after 25–27 days. A comparison between careful hand-seeding and surface-scattering seed release methods in the open-ocean habitat showed no significant differences in survival rate after 41 days. Larger seed survived significantly better than the smaller seed when scattered on the surface (p<0.0001) and the smaller seed survived significantly better when seeded carefully by hand onto the substrate (p<0.028). Further medium-term releases of large numbers of seed abalone, released using the surface-scattering method in open-ocean habitat, gave mean survival rates of 32.8% over periods of 83–114 days. Assessment of a seeding trial using release modules to seed juvenile animals in the open-ocean was hampered by poor sea conditions and difficult to search substrates, and a mean recovery rate of 3.1% was obtained for the sites that were sampled. Movement of seed was low in the more sheltered sites, and also appeared to be affected by the amount of available habitat. Growth of seed was measured using changes in shell colouration and there were significant differences between areas. An average growth of 1.6mm.month⁻¹ shell length was calculated for all areas. The potential for commercial scale abalone ranching to be used to enhance a territorial user right fishery was investigated using a model of economic feasibility. Internal rates of return of 30.3 and 36.9% were obtained from two harvest regimes using different harvest sizes. There was a high degree of risk associated with these figures owing to a lack of consistent seed survival rate estimates, and the input parameters, which are subject to variation, showed a significant effect on profitability. The operation of this type of ranching scheme is probably not economically feasible as a stand-alone operation but could probably be operated effectively in conjunction with an existing abalone farm. By adding a small wild catch component the profitability of a ranching scheme could be significantly improved. The results of the present study indicate that high levels of poaching at Cape Recife have led to declines in emergent abalone abundance, which will probably lead to stock collapse in the near future. This implies that fisheries managers have failed to fulfil the provisions of fisheries policy in South Africa. The present results from seeding trials show that cultured juveniles can survive and make a contribution to overall stock abundance. Furthermore, while there are obstacles to economic feasibility, commercial ranching has the potential to be a valuable addition to current abalone management strategy.

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Nearly all South African abalone farms function on an intensive pump-ashore, flow-through system. Large volumes of sea water that are pumped ashore flow through abalone or kelp harvesting tanks and finally gravitate back to the ocean. If the effluent from an abalone farm can be desalinated without permanent membrane fouling, then sea water reverse osmosis (SWRO) technology can be integrated effectively with established abalone farms without having to increase the farms’ intake system capacities. Without the need to construct and maintain an intake system, the overall cost of desalination can be reduced. Therefore, the aim of this study was to determine the feasibility and viability of integrating a SWRO desalination plant with a typical South African abalone farm. The project focused on four areas of concern, namely: - characterisation of typical South African abalone farm water - SWRO desalination plant pilot study and membrane fouling behaviour - general operation of a typical abalone farm and its implications for desalination - cost estimates and implications for the integration of an SWRO desalination plant with an abalone farm During a nine-month on-site investigation, sea water turbidity was reduced by up to 43% from a mean value of 0.82 NTU in the influent stream to 0.47 NTU in the combined effluent stream from the abalone tanks. Even with spikes in the influent turbidity, the turbidity of the combined effluent from all abalone tanks (excluding tank flush water) remained below 1 NTU. Dissolved organic carbon (DOC) in both the influent and combined effluent remained below 1 mg/litre. Ultrafiltration (UF) was selected as pre-treatment to the reverse osmosis (RO) in order to minimise potential fouling of the RO membranes. Membrane compaction of both the UF and RO membranes contributed significantly to initial flux losses – as much as 18% for the polyethersulfone (PESM) UF membranes and 20% for the thin film composite (TFC) polyamide RO membrane. However, this is comfortably in line with typical compaction values quoted in the literature. Without pre-flocculation, the UF was able to operate at a specific flux between 45 and 55 litre/m2/h (LMH) and recoveries ranging between 60 and 75%. Corresponding trans-membrane pressure (TMP) ranged between 0.59 and 0.76 bar. With ferric chloride pre-flocculation at a concentration of 3 mg/litre (as Fe3+) the UF could be operated at notably lower TMP values between 0.11 and 0.36 bar. These results indicate that provision should definitely be made for pre-flocculation when using UF as pre-treatment, despite the fact that the DOC concentrations and turbidity of the abalone farm effluent are quite low (DOC <1 mg/litre, NTU <1). It furthermore highlights the inability of DOC and turbidity alone to predict the membrane fouling potential of water. A better indicator of membrane fouling potential, albeit not perfect, is the modified fouling index (MFI0.45). This index follows a linear trend with foulant concentration and serves as a good indicator of the filterability of water. On-site measurements showed an increase in mean MFI0.45 values from 29 s/litre2 for the influent to 48 s/litre2 for the effluent from the abalone tanks, thereby confirming the need for pre-flocculation as part of UF pre-treatment. Chemically enhanced backwashing (CEB) of the UF membrane at least every 24 hours was found to be essential for its stable operation. Therefore, UF with pre-flocculation (3 mg/litre Fe3+) and regular CEB can be used effectively as pre-treatment method for the desalination of abalone farm effluent water. An RO ‘feed-and-bleed’ system was used to simulate the typical performance of the last membrane in a full-scale RO membrane bank. This RO membrane performed well with no signs of extreme fouling. The membrane produced a good quality permeate – for the last membrane in a membrane bank – reducing the TDS of the RO feed from 33 493 mg/litre to 969 mg/litre. These results compared well with simulated values by Reverse Osmosis System Analysis (ROSA; an RO simulator by DOW), indicating a TDS reduction from 33 271 mg/litre to 1 409 mg/litre at a feed pressure of 56 bar, and overall recovery of 44%. A steady performance of the RO membrane during the pilot study indicated that it is possible to desalinate abalone effluent water without notable permanent membrane fouling. A stable normalised flux rate of 8 LMH was achieved and RO membrane integrity remained intact with a salt rejection that ranged from 98.0 to 98.5%. No sudden reduction in permeate flux was observed as a result of fouling by unknown constituents present in the UF permeate. DBNPA (a non-oxidising disinfectant) was dosed once per week at a concentration of 10 – 30 mg/litre for 30 minutes. Scaling was controlled effectively by means of an antiscalant dosed at a concentration of 11 – 12 mg/litre in the feed stream. The CIP frequency was not optimised but a CIP frequency of once every 6 – 8 weeks appeared to be more than adequate to prevent permanent membrane fouling Advantages of integrating an SWRO desalination plant with a South African abalone farm include: - no lengthy and costly environmental impact assessment (EIA) is required to build a new intake system - shared capital and operational cost of intake system - dual incentive to keep constant good quality water flowing through the farm - early warnings regarding occurrences such as algal bloom and red bait - shared operational and management cost to keep pipelines clean - electricity saved (pumps for intake system) Disadvantages of integrating an SWRO desalination plant with a South African abalone farm include: - will require diverting of the abalone tank wash water from regular effluent - possible water ‘down-times’ due to maintenance operations on abalone farm Based on information from the literature the fixed capital cost depreciation rate (FCCDR) typically contributes approximately 40% and the operation and maintenance (O&M) cost typically contributes 60% to the unit production cost (UPC) of desalinated water. Furthermore, a SWRO desalination plant’s intake system can contribute between 5% and 33% to the FCCDR, depending on the nature and design of the plant. Consequently, the intake system can contribute between 2% and 13% of the UPC of desalinated sea water. This implies possible cost savings of between R0.15/m3 and R2.37/m3 for the production of fresh water (depending on site-specific design factors) when desalinating sea water effluent from on-shore abalone tanks. Integration of an SWRO desalination plant with a South African abalone farm is feasible and viable, provided that the necessary steps and precautions are taken to ensure a smooth and stable operation of the SWRO desalination plant. Cost savings on the part of all the stakeholders are possible if the correct contract can be negotiated. / AFRIKAANSE OPSOMMING: Byna alle Suid Afrikaanse perlemoenplase funksioneer op ‘n seewater deurvloeistelsel. Groot volumes seewater word aan wal gepomp en vloei deur die perlemoen of kelp-oes tenks. Hierdie water vloei dan uiteindelik terug na die oseaan as gevolg van swaartekrag. Indien die afvalwater van die perlemoenplase ontsout kan word sonder permanente membraanbevuiling kan seewater tru-osmose (SWTO)-tegnologie effektief met gevestigde perlemoenplase geïntegreer word sonder om die plase se water inname-stelsels se kapasiteite te vergroot. Sonder die behoefte aan uitbreiding en instandhouding van ‘n water inname-stelsel by so ‘n plaas behoort die totale koste van ontsouting aansienlik minder te wees. Die doel van hierdie studie was dus om die uitvoerbaarheid en lewensvatbaarheid van ‘n integrasie van ‘n SWTO ontsoutingsaanleg met ‘n tipiese Suid Afrikaanse perlemoenplaas te ondersoek. Ten einde dit te doen, het die projek op vier areas van belang gefokus, naamlik: - karakterisering van tipiese Suid-Afrikaanse perlemoenplaas water - SWTO ontsoutingsaanleg loodsstudie en membraan bevuilingsgedrag - algemene bedryf van ‘n tipiese perlemoenplaas en die implikasies vir ontsouting - kosteberamings en koste-implikasies met betrekking tot die integrasie van ‘n SWTO ontsoutingsaanleg met ‘n perlemoenplaas Gedurende ‘n nege maande op-perseel ondersoek is seewater troebelheid verminder met tot 43% van 'n gemiddelde waarde van 0.82 NTU in die invloeistroom tot 0.47 NTU in die gekombineerde afvalwaterstroom wat die tenks verlaat. Selfs met skerp wisseling in die invloeistroom troebelheid, bly afvalwaterstroom troebelheid deurgaans onder 1 NTU met die uitsondering van tenk spoelwater. Opgeloste organiese koolstof (OOK) in beide die invloeistroom en die gekombineerde afvalwaterstroom het deurgaans onder 1 mg/liter gebly. Ultrafiltrasie (UF) is gebruik as voorbehandeling vir die tru-osmose (TO) om sodoende potensiële bevuiling van TO membrane te minimaliseer. Membraan kompaksie van beide die UF en TO het merkbaar bygedra tot aanvanlike deurvloeiverliese – so veel as 18% vir die poli-etersulfoon (PESM) UF membrane en 20% vir die dun film saamgestelde (DFS) poli-amied TO membraan. Hierdie is egter gerieflik binne die tipiese kompaksiewaardes soos aangehaal in die literatuur. Sonder flokkulasie was die UF in staat tot temperatuur aangepaste deurvloeitempo van tussen 45 en 55 liter/m2/h (LMH) teen herwinningstempo’s tussen 60 en 75%. Ooreenstemmende trans-membraandrukkings (TMD) het gewissel tussen 0.59 en 0.76 bar. Met ysterchloried voor-flokkulasie teen 'n konsentrasie van 3 mg/liter (as Fe3+) kon die UF teen merkbaar laer TMD waardes bedryf word – tussen 0.11 en 0.36 bar. Hierdie resultate dui daarop dat daar beslis voorsiening vir pre-flokkulasie gemaak moet word wanneer UF as voorbehandeling gebruik word, ten spyte van die feit dat die OOK konsentrasie en troebelheid van die afvalwater van die perlemoenplaas redelik laag is (OOK <1 mg / liter, troebelheid <1 NTU). Verder lig dit die onvermoë uit om OOK en troebelheid alleen te gebruik om membraanbevuilingspotensiaal van water te voorspel. ‘n Beter aanwyser van membraanbevuilingspotensiaal, alhoewel nie perfek nie, is die aangepaste bevuilingsindeks (MFI0.45). Hierdie bevuilingsindeks volg ‘n lineêre neiging met die konsentrasie van onsuiwerhede en dien as ‘n goeie aanwyser van die filtreerbaarheid van water. Op-perseel metings het getoon dat ‘n toename in gemiddelde MFI0.45 waardes van 29 s/litre2 vir die invloeistroom tot 48 s/litre2 vir die afvalstroom van die perlemoentenks die behoefte vir voor-flokkulasie as deel van UF voorbehandeling bevestig. Chemies versterkte terugspoeling (CVT) van die UF membrane ten minste elke 24 uur is noodsaaklik gevind ten einde bestendige werking te verseker. Dus kan UF met voor-flokkulasie (3 mg/liter Fe3 +) en gereelde CVT effektief as voorbehandeling metode vir die ontsouting van perlemoenplaas afvalwater gebruik word. ‘n TO ‘voer-en-bloeistelsel’ is gebruik om die tipiese prestasie van die laaste membraan in ‘n volskaalse TO membraanbank te simuleer. Hierdie TO membraan het goed presteer sonder tekens van buitensporige membraanbevuiling. Vir die laaste membraan in ‘n membraanbank het die membraan goeie gehalte finale water gelewer – ‘n vermindering van die totaal opgeloste stowwe (TOS) van die TO voerwater van 33 493 mg/liter tot 969 mg/liter is behaal. Hierdie resultate het goed vergelyk met gesimuleerde waardes deur Reverse Osmosis Analysis System (ROSA, ‘n TO simulator deur DOW) wat ‘n TOS vermindering van 33 271 mg/liter tot 1 409 mg/liter by ‘n voerdruk van 56 bar en ‘n algehele herwinningstempo van 44% aandui. ‘n Bestendige werking van die TO membraan tydens die loodsstudie het getoon dat dit moontlik is om perlemoenplaas afvalwater te ontsout sonder merkwaardige permanente membraanbevuiling. 'n Stabiele genormaliseerde deurvloeitempo van 8 LMH is bereik en TO membraan integriteit het ongeskonde gebly met 'n sout verwerping wat gewissel het van 98.0 tot 98.5%. Geen skielike afname in finale water deurvloeitempo is waargeneem as gevolg van bevuiling deur onbekende onsuiwerhede in die UF finale water nie. DBNPA (‘n nie-oksiderende ontsmettingsmiddel) is een keer per week teen ‘n ‘n konsentrasie van 10 – 30 mg / liter vir 30 minute gedoseer. Mineraal skaalvorming is effektief beheer deur die dosering van ‘n anti-skaalmiddel teen 11 – 12 mg/liter in die TO voerstroom. Die skoonmaak-in-plek (SIP) frekwensie is nie ge-optimeer nie, maar ‘n SIP een keer elke 6 – 8 weke is meer as voldoende gevind om mikrobiese bevuiling te voorkom. Voordele van die integrasie van 'n SWTO ontsoutingsaanleg met 'n Suid-Afrikaanse perlemoenplaas sluit die volgende in: - geen lang en duur omgewings impak ontleding (OIO) is nodig vir die bou van ‘n nuwe inname-stelsel nie - gedeelde kapitaal en operasionele koste van inname-stelsel - tweeledige aansporing om konstant goeie gehalte watervloei deur die plaas te verseker - vroegtydige waarskuwings ten opsigte van gebeurtenisse soos rooigety - gedeelde bedryfs- en bestuurskoste om voerpype skoon te hou Nadele van die integrasie van 'n SWTO ontsoutingsaanleg met 'n Suid-Afrikaanse perlemoenplaas sluit die volgende in: - vereis herleiding van perlemoentenk spoelwater weg van gereelde afvalwater - moontlike watervloei-aftye weens instandhoudingsbedrywighede op die perlemoenplaas Gebaseer op inligting uit die literatuur dra die vaste kapitaal koste waardeverminderings-koers (VKKWK) gewoonlik ongeveer 40% en die bedryfs- en instandhoudingskoste (B&I) ongeveer 60% by tot die produksiekoste per eenheid (PKE) van ontsoute water.Verder kan ’n SWTO ontsoutingsaanleg se inname-stelsel tussen 5% en 33% tot die VKKWK bydra afhangende van die aard en ontwerp van die aanleg. Gevolglik kan die inname-stelsel tussen 2% en 13% tot die PKE van ontsoute seewater bydra. Dit impliseer ‘n moontlike kostebesparing van tussen R0.15/m3 en R2.37/m3 vir die produksie van vars water wanneer die afvalwater van perlemoentenks ontsout word. Integrasie van 'n SWTO ontsoutingsaanleg met 'n Suid-Afrikaanse perlemoenplaas is uitvoerbaar en lewensvatbaar indien die nodige stappe en voorsorgmaatreëls geneem is om ‘n vlot en bestendige werking van die SWTO ontsoutingsaanleg te verseker. Kostebesparings vir alle belanghebbendes (beleggers) is moontlik indien daar oor die korrekte kontrak onderhandel kan word.

Thesis (MScAgric)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Haliotis midae (HM) is one of five indigenous abalone species occurring along the coast of South Africa, and is the only species commercially cultivated in open flow-through systems. Commercial production of HM contributes the most to income generated from aquaculture species in South Africa. Exports in 2011 totalled 1036 ton, which amounts to an income of ZAR 369 million (40 million USD). Commercial production of HM is characterized by a long interval (i.e. up to five years) to harvest. Genetic modification of HM to improve growth rate in HM can potentially decrease the interval from hatch to harvest, which will contribute to optimising the cost-efficient production of HM. However, a major concern in the production of genetically modified (GM) abalone is their escape from production systems, and the potential impact of the GM animals on the natural stocks in the surrounding environment. The implementation of containment methods to prevent the escape from GM abalone from production systems will assist in the management of the potential ecological risks escaped GM abalone may pose. Currently no containment strategies exist for the South African abalone industry, which limits the use of transgenic biotechnologies to optimise the cost-efficient production of HM. The study therefore investigated the potential of biological methods (triploid induction), mechanical methods (polypropylene filter bags and obstructive materials), and chemical methods (sodium hypochlorite and chlorine dioxide) to contain transgenic HM in open flow-through systems. Histological evaluation of gonad tissue samples of 16 triploid male and 15 triploid female HM indicated that triploid induction was unsuccessful in arresting gonad differentiation, development, and function. A combination of immature and mature gametes was observed on both triploid male and female gonads. The fertilizing potential of biopsied sperm obtained from triploid and induced diploid male HM was assessed in fertilization trials using ova obtained from diploid HM. No larvae were observed from the fertilization treatments of triploid male biopsied sperm, however, abnormal larvae (0.01% fertilization) were observed when induced diploid sperm were used to fertilize diploid ova. Polypropylene filter bags (100 μm) were not effective in containing male and female gametes in the broodstock section of the abalone culture system used in this study, and future studies should address specialized methods of containment of HM gametes. Polypropylene filters (100 μm), resulted in effective containment of larvae and settlement larvae, and in this study was not a more effective method of containment than the current on-farm larvae containment protocol. The three obstructive materials were effective in containing HM spat, and did not differ in their ability as containment methods. Sodium hypochlorite and Biox™, chlorine-based chemicals, were effective in containing the five life stages of HM, i.e. sperm, ova, larvae, settlement larvae and spat. The respective life stages were exposed to varying concentrations of the respective chemicals (i.e. 10 ppm, 50 ppm and 100 ppm) over five exposure times (i.e. 4, 6, 8, 10 and 12 minutes). Sodium hypochlorite and Biox™, at the different concentrations and exposure times, resulted in mortalities in all five HM life stages, with higher incidences recorded at the higher concentrations evaluated. Future research on the effect of triploid induction on the endocrine system, and how effective gonad maturation and function is suppressed, needs to be conducted. The aspects of mosaics occurring in induced diploid animals warrant further investigation with a larger sample size to verify the findings of this study. The production of true sterile individuals would improve the results to use of GM animals as a method of biological containment. Incorporation of mechanical containment methods need to be kept in mind when abalone production systems are designed. The use of chemical containment methods warrants additional studies on the practical administration and the economic feasibility of the chemical into the water supply of open flow-through abalone culture systems. / AFRIKAANSE OPSOMMING: Haliotis midae (HM) is een van vyf inheemse perlemoen spesies wat langs die kus van Suid-Afrika voorkom en is die enigste spesie wat kommersieel in oop deurvloeistelsels geproduseer word. Kommersiële produksie van HM dra die meeste tot kommersiële akwakultuur produksie by, met uitvoere van 1036 ton in 2011, wat gelykstaande aan ‘n inkomste van ZAR 369 miljoen (40 miljoen VSA dollar). Kommersiële produksie van HM word gekenmerk deur 'n lang interval (d.i. tot 5 jaar) vanaf uitbroei tot oes. Genetiese modifisering van HM om die groeitempo te verbeter kan potensieel die interval tot slagmassa verkort, wat potensieel tot die optimalisering van die kostedoeltreffende produksie van HM kan bydra. 'n Groot bron van kommer met die produksie van geneties gemodifiseerde (GM) perlemoen is hul ontsnapping uit produksiestelsels en die potensiële impak van die GM diere op die natuurlike perlemoenpopulasies in die omliggende omgewing. Die implementering van beheermetodes om die ontsnapping van GM perlemoen uit produksiestelsels te voorkom sal die bestuur van die potensiële ekologiese risiko's wat GM perlemoen mag inhou, vergemaklik. Tans bestaan daar geen inperking strategieë vir GM diere vir die Suid-Afrikaanse perlemoenbedryf nie, wat die gebruik van transgeniese biotegnologieë vir die kostedoeltreffende produksie van HM beperk. Die studie het dus die potensiaal van biologiese metodes (triploïed induksie), meganiese metodes (polipropileen filters en obstruktiewe materiaal) en chemiese metodes (natriumhipochloriet en Biox™) om as inperk strategieë vir die bestuur van transgeniese HM in oop deurvloei produksiesisteme gebruik te word, ondersoek. Histologiese evaluering van gonadeweefsel monsters van 16 manlike en 15 vroulike triploïed HM het aangedui dat triploïed induksie onsuksesvol was om gonade differensiasie, ontwikkeling, en funksie te onderdruk. 'n Kombinasie van onvolwasse en volwasse gamete is in gonades van beide manlike en vroulike triploïed HM waargeneem. Die bevrugtingsvermoë van sperme wat versamel is met behulp van ʼn biopsie metode van triploïed en geïnduseerde diploïed HM is geëvalueer in bevrugtingsproewe met ova wat van diploïed HM versamel is. Geen larwes is waargeneem met die gebruik van die triploïed sperme nie, maar abnormale larwes (0.01% bevrugting) het wel voorgekom met die evaluering van sperme versamel van geïnduseerde diploïed HM. Die voorkoms van mosaïek diere (d.i. ʼn kombinasie van beide diploïed en triploïed selle in een individu) wat ontstaan a.g.v. onvolledige triploïed induksie noodsaak verdere navorsing met ʼn groter monster diere om die vermoë van triploïed induksie om HM steriel te maak, te verifieer. Polipropileen filters (100 μm) was nie effektief om beide manlike en vroulike gamete wat in die teelafdeling in die perlemoenkultuursisteem in hierdie studie geproduseer is, vas te vang nie. Toekomstige studies moet gespesialiseerde metodes wat insluiting van HM gamete moontlik sal maak, ondersoek. Polipropileenfilters (100 μm) was effektief met die inkamping van larwes en vestigingslarwes, met die filters wat nie meer doeltreffend as die bestaande inkampingsmetodes in die produksiesisteem was nie. Die drie obstruktiewe materiale was doeltreffend ten opsigte van die inkamping van onvolwasse perlemoen individue, met die 3 materiale wat ewe doeltreffend in hulle vermoë was om die onvolwasse HM se ontsnapping uit die sisteem te voorkom. Natriumhipochloriet en Biox™, chloor-gebaseerde chemikalieë, was effektief om die onderskeie 5 lewenstadiums, d.i. HM sperme en ova, larwes, vestigingslarwes en onvolwasse HM se voorkoms tot hulle onderskeie afdelings binne die produksiesisteem te beperk. Die onderskeie lewensstadiums is blootgestel aan verskillende konsentrasies van die onderskeie chemikalieë (d.i. 10 dpm, 50 dpm en 100 dpm) oor vyf tydsintervalle (d.i. 4, 6, 8, 10 en 12 minute). Natriumhipochloriet en Biox™ het ʼn letale effek op al vier lewensstadia gehad, met hoër sterftes wat met hoër konsentrasies aangeteken is. Toekomstige navorsing oor die uitwerking van triploïed induksie op die endokriene stelsel en hoe doeltreffend die rypwording en funksie van die gonades onderdruk word, moet aandag geniet. Die voorkoms van mosaïek diere regverdig ook spesifieke aandag in toekomstige navorsing. Die produksie van ware steriele individue sou die gebruik van GM perlemoen as 'n metode van biologiese inkamping moontlik maak. Inlywing van meganiese inkampingmetodes moet in gedagte gehou word wanneer perlemoen produksiestelsels ontwerp word. Die gebruik van chemiese inkampingmetodes benodig verdere studies om te verseker dat die chemiese middels so bekostigbaar en prakties as moontlik in water van 'n oop deurvloei perlemoen produksiestelsel toegedien kan word.

Thesis (PhD (Genetics))--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Currently, South African aquaculture is dominated by the cultivation of Haliotis midae, which is estimated as the most lucrative sector of the industry, with 934 t being export in 2008, totalling an income of ZAR 268 million (40 million USD) in 2008. This represents 81% of the total rand value of the aquaculture sector. Abalone was the highest aquaculture commodity exported during the last two years from South Africa, representing 24% of the total tonnage exported. Employment in the aquaculture sector increased by approximately 80% between 2005 and 2008, and was highest in the abalone sector where the number of people employed increased by 234%. Despite these high production rates, no hatchery procedures have been developed specifically for H. midae. Most procedures and protocols currently used in South African abalone hatcheries have been adopted from cultivation methods used for foreign species. Although certain aspects of reproduction are universally conserved between abalones, it is important to consider the physiology and the origin of the species studied. To date, no scientific research has been conducted on the reproduction of H. midae, except for a few studies in the early 1990s, which focused on the basic reproduction of this species. No further studies have been done on H. midae reproduction under intensive culture. Currently, hatch-out rates obtained by most abalone farms in South Africa averages 80%, with a 50% settlement rate, and a final hatchery output of only 30%. This study reports on various aspects of H. midae reproduction that can influence its commercial culture. A detailed histological characterisation of gametogenesis was developed. Findings indicated that cultured H. midae reaches 50% sexual maturity at a shell width of between 25 mm and 30 mm. During fertilisation trials, a sperm concentration of 50 000 sperm mL-1 and egg concentrations lower than 50 eggs mL-1 produced the highest hatch-out rates. Whilst fertilisation volume did not influence fertilisation success, fertilisation potential of the eggs did decrease with time. Eggs older than 100 minutes showed a lower fertilisation potential than eggs fertilised earlier. A larval stress test was developed to evaluate larval resistance against chemical stress. It was determined that 50% of resultant larvae would exhibit morphological abnormalities after fertilised eggs were incubated in 0.7% dimethyl sulfoxide (Me2SO) for a 24 hour period. If larvae exhibited fewer abnormalities at this concentration, it could be deduced that the larvae had a high resistance to the negative effect of the toxicant, and could thus be seen as good quality larvae. When evaluating hybridisation potential between H. midae and H. spadicea, it was found that it was possible to fertilise spawned H. midae eggs with biopsied H. spadicea sperm. By incorporating the results obtained from the present study into current hatchery systems on South African abalone farms, higher hatchery yield could be achieved, which in turn would lead to an increase in commercial revenue. / AFRIKAANSE OPSOMMING: Die Suid-Afrikaanse akwakultuur sektor word tans oorheers deur die produksie van Haliotis midae, en word gereken as die mees winsgewendste bedryf in die industrie, met 934 t uitgevoer in 2008, na-raming „n inkomste van ZAR 268 miljoen (40 miljoen Amerikaanse doller). Dit verteenwoordig sowat 81% van die totale rand waarde in die akwakultuur bedryf. Perlemoen was ook die grootste uitvoer kommoditeit gedurende die laaste twee jaar, en het tot sowat 24% van die totale uitvoer vanuit akwakultuur bygedra. Werksgeleenthede in die akwakultuur sektor het tussen 2005 en 2008 met ongeveer 80% gegroei, waarvan die hoogste groeisyfer in die perlemoen bedryf was, waar die aantal werknemers met 234% toegeneem het. Ten spyte van hierdie hoë produksie omset, is daar tans geen protokolle wat spesifiek vir die produksie van H. midae ontwerp is nie. Meeste van die tegnieke wat huidiglik gebruik word op Suid-Afrikaanse plase, is gebaseer op, en aangepas vanaf metodes daargestel in die internasionale bedryf vir uitheemse spesies. Alhoewel sekere aspekte van reproduksie tussen perlemoen spesies verband hou, is dit belangrik om die fisiologie en oorsprong van die spesie van belang, in ag te neem. Wetenskaplike navorsing gedoen op die reproduksie van H. midae is beperk tot studies in die vroeë 1990s, wat die basiese beginsels van die spesie se reproduksie ondersoek het. Daar is geen verdere studies op die reproduksie van H. midae, veral onder intensiewe teel toestande, gedoen nie. Tans toon die meeste perlemoen plase in Suid-Afrika „n produksie persentasie van ongeveer 80% larwes vanaf bevrugting, met „n afname na 50% met vestiging en „n gevolglike uitset van slegs 30%. Hierdie studie doen verslag oor verskeie reproduksie aspekte van H. midae wat die teel doeltreffendheid van perlemoen op kommersiële plase kan beïnvloed. „n Gedetaileerde histologiese karakterisering van gametogenese is ontwikkel. Daar is gevind dat geteelde perlemoen 50% geslagsrypheid bereik met „n skulp wydte van tussen 25 mm en 30 mm. Tydens bevrugting eksperimente is bepaal dat 50 000 sperm mL-1 en „n eier konsentrasie van laer as 50 eiers mL-1, die optimale gameet konsentrasies is vir effektiewe bevrugting. Alhoewel die volume water waarin bevrugting plaasvind nie „n invloed getoon het op bevrugtingsukses nie, is daar wel gevind dat die eiers se potensiaal om bevrug te word, afneem met verloop van tyd. Eiers ouer as 100 minute het „n verlaagde bevrugtingspotentiaal getoon teenoor eiers wat vroeër bevrug is. „n Larwale stres toets is ontwikkel om larwale weerstand teen chemiese stres te bepaal. Daar is gevind dat 50% van geproduseerde larwes morfologiese abnormaliteite sal toon indien bevrugte eiers vir „n periode van 24 uur in 0.7% dimetiel sulfoksied (Me2SO) geïnkubeer word. Indien larwes minder abnormaliteite toon by hierdie konsentrasie, beteken dit dat hierdie larwes meer weerstand kan bied teen die negatiewe effek van die toksiese middel, en dus beskou kan word as goeie kwaliteit larwes met hoë lewensvatbaarheid. Met die evaluering van hibridisasie potensiaal tussen H. midae en H. spadicea, is gevind dat dit moontlik is om vrygestelde H. midae eiers te bevrug met H. spadicea sperm wat verkry is deur „n biopsie. Die implementering van hierdie studie se bevindinge in kommersiële H. midae produksiesisteme sal daadwerklik bydra tot die optimisering van bestuurspraktyke en „n verhoging in die totale produksie doeltreffendheid van sulke sisteme.