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Behavioural, reproductive and growth studies on Oreochromis mossambicus (Peters 1852)Weber, Raimund Michael. January 2010 (has links)
A major obstacle facing the successful creation of an African aquaculture industry, based upon Oreochromids, is the irregular supply of good quality fish seed. There are several causative biological processes behind its irregular supply. The aim of this research was therefore to determine the basic requirements for the establishment and maintenance of a small breeding facility, for O. mossambicus. The goal was to make a unit that was simple and which could be easily replicated in rural, satellite aquaculture seed stations. The results obtained illustrate that a small reproduction unit can produce large quantities of healthy 90-day fry.
Asynchronous hatching of the eggs and spawning asynchrony in female Oreochromis mossambicus are two elements which negatively affect uniformity in the fry produced. Typical fish seed production uses large ponds partitioned into breeding allotments or a series of breeding pools. While the earthen ponds provide a substrate in which a nest can be excavated, its presence is not required for mating success in the closely related O. niloticus (Linneaus 1758). Female mate choice, as well as apparent fecundity, according to nest size has been clearly recorded in related cichlids but no investigations have been made as to nest size and spawning synchrony in O. mossambicus. The main focus of this investigation was to ascertain whether O. mossambicus would accept artificial nest substitutes in preference to their own constructed ones and secondly, whether different alternatives would elicit different levels of acceptance. The observed results indicate a ready acceptance for artificial nest alternatives, with nest lip height being prioritised by the fish . The implications thereof are discussed in relation to the potential for optimization of breeding arenas for O. mossambicus by the provision of artificial nests whose dimensions satisfy both male and female preferences.
In established communities, Oreochromis mossambicus display various complex and ritualised behaviours during stable and disruptive events. The aim of this research was primarily to produce a glossary of behaviours defining these interactions, particularly with reference to male-male behaviours. Three males and six females were allowed to acclimatise over one month, with various social groupings being established within the first few days. Results from this study illustrated not only a dynamic social structure, signaled via various chemosensory and visual methods, but also supported recent findings in apparent male-male courtship and the underlying
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causes. Furthermore, the observed male-male activity of the nestholder malesfirmly corroborate the current practice in aquaculture whereby only one male is allocated per breeding arena.
The use of artificial incubation of Oreochromis spp. eggs has become widespread in high intensity fish seed production. Various types of incubator exist, and their selection is dependent on the specific attributes of the egg to be incubated. Currently available incubators are typically of a funnel (up-flow) or round bottomed (down-flow) design. Neither permits easy access to the eggs, which is particularly important when dealing with poor quality water as is typically found in rural areas. The aim of this study was to devise and test an easy-to-use incubator, applicable to rural seed production projects, which offers advantages over currently available incubator types. The final design, WETNURSE Type II, offered improved hatching rates over Type I, with a mean hatching success of 75%. While falling short of the desired 80% success rate (Rana 1986), the various other benefits provided by the design justify further optimization and testing.
Three distinct populations of O. mossambicus, representing populations of inbred, randomly mated and genetically unknown (wild-caught) pedigree were analysed according to their food conversion efficiency (FCE). The intra- and inter-sample crosses were done with single males in order to produce half-sib progeny batches which allowed for the assessment of sire influences on the FCE of the progeny batches. The results show that the population of unknown pedigree is comparable to that of the randomly mating population, indicating the presence of sufficient genetic variation to permit further selection; the genetic contribution of the males to their respective progeny was insignificant in relation to that made by the female.
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Integrating aquaculture with crop systems : an aquaponic enterprise project proposal for the Ntinga Multipurpose Co-Operative in Philippi, South Africavan der Merwe, Marnus 04 1900 (has links)
Thesis (MPhil)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Stellenbosch University was approached to assist with developing a techno-financial model for an urban freshwater aquaculture system in Philippi, Cape Town. Rapidly growing urban areas are predominantly becoming concentrated zones for malnutrition and poverty which require attention. Having enough food to eat does not mean that a family is food secure, the problem is usually associated with the lack of access to nutritious food. Fish is seen as an extremely healthy food which has the potential to effectively support food security and alleviate malnutrition.
Aquaculture is identified as a largely underdeveloped sector in South Africa. It is currently undergoing rapid transition, being promoted by government as an industry that has potential to develop and create jobs, provide food security and grow the South African economy.
Aquaponics- a method to integrate aquaculture with growing crops in a symbiotic system is a highly resource efficient closed-integrated food producing technology which has the potential to benefit from South African biosecurity regulations and climate-geographic characteristics. It is viewed as an effective food production alternative to deal with the challenges of declining high quality freshwater resources and available arable land.
Training and capacity building is important for the development of aquaponic technology. This study explores and identifies the advantages aquaponic technology development would have in South Africa. The study has reviewed and assessed the fundamental principles for aquaculture production and management required for aquaponic systems development and management. A practical case study identifies the daily challenges and design parameters of aquaponic systems. The study is concluded with a techno-financial project proposal which shows how aquaponic systems can be planned. / AFRIKAANSE OPSOMMING: Universiteit Stellenbosch was genader om 'n tegno-finansiele model to ontwikkel vir 'n stedelike akwakultuur plaas in Philippi, Kaapstad. The tempo waarteen die stedelike areas groei ontwikkel kommerwekkende uitdagings soos wanvoeding en armoede.
In hierdie studie is vis geindentifiseer as 'n uiters voedsame aanvulling in die dieet van Suid Afrikaners. Akwakultuur is grootliks agter in terme van ontwikkeling. Dit word beskou as 'n sektor wat groot potensiaal inhou vir Suid Afrika se eknomiese groei, werkskepping en voedselsekuriteit.
Akwaponika is die hersirkulerende integrasie van akwakultuur en hidroponika. Akwaponika hou groot voordele in terme van Suid Afrika se biosekuriteit regulasies and geografiese eienskappe en is 'n effektiewe manier om gebruikte akwakultuur te suiwer.
Opleiding en beplanning word gesien as 'n fundamentele benadering tot suskesvolle akwaponika ontwikkeling. Hierdie studie bestudeer die Suid Afrikaanse omgewing en potensiaal vir akwaponika ontwikkeling. Die fundamentele beginsels van akwakultuur en hidroponika bestuur en produksie is saamgesit wat beskou word as die aanbevele manier om akwaponika te bestuur. 'n Praktiese gevallestudie toon die daaglikse uitdagings aan en gee raad oor daaglikse bestuur van akwaponika stelsels. Die studie word afgesluit met 'n tegno-finansiele model wat wys hoe om 'n akwaponika sisteem te beplan.
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An economic analysis of the impact of removing organic waste from small scale cage aquaculture systems in irrigation dams in the Western CapeGumbo, Tichaona 03 1900 (has links)
Thesis (MScAgric (Agricultural Economics))--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: The rising demand of fish due to population growth coupled by stagnation of fish supply from
natural capture has led the world to turn to aquaculture to fill in the gap between fish supply and
demand. Aquaculture has emerged as the only sustainable way of supplying the rising population
with fish. However the rapid expansion of aquaculture has been met with growing concerns over its
environmental effects especially waste produced from aquaculture. The net cage system that is
currently being used by small scale trout farmers in the Western Cape is an open water based
system where release of waste into the water bodies is inevitable and this put into question the long
term sustainability of trout farming using net cages in irrigation dams in the Western Cape.
This study sought to compare identified production techniques that can be used by aquaculture
farmers to reduce accumulation of organic waste in irrigation dams. The proposed ‘clean’
production techniques include use of net cages fitted with Lift-up system, semi intensive floating
tank system (SIFTS) and intergrated aquaculture systems. The study revealed that the intergrated
aquaculture system is the most effective way of recovering waste that shows great potential of
moving aquaculture towards long term sustainability as it fullfills sustainability dimensions such as
‘zero emission’, nutrient recycling and integrated production. Mechanical methods of recovering
waste such as Lift-up system and SIFTS are also effective in recovering particulate waste but
however dissolved nutrients are lost into the environment.
The study went on further to investigate if economic, environmental and social benefits of
recovering waste from irrigation dams outweigh the costs of recovering waste using different
production techniques. Models of small scale aquaculture farms using the three identified
production techniques were developed and compared with a modelled small scale net cage farm
where there was no waste recovery. A comparative financial analysis of the modelled small scale
trout farms using alternative production techniques carried out showed that trout production using
any of the three alternative ‘clean’ production techniques is financially viable with the SIFTS
production technique giving the farmer the highest returns, followed by the intergrated system, then
the net cage with a Lift-up system and lastly the net cage system without waste recovery.
The second part of the study used the contingent valuation method to estimate the environmental
and social benefits of removing waste from dams. Households revealed that they were willing to
pay (WTP) R40 on average annually to improve water quality from a state where eutrophication
had occurred to a state suitable for irrigation and aquaculture. To improve water quality from a state
suitable for irrigation to a state suitable for swimming, households were willing to pay R16.67
annually. If water was to be improved from a state suitable for irrigation to a level suitable for
domestic purposes, average willingness to pay (WTP) was R26.17 annually. WTP indicate that
besides financial benefits associated with using ‘clean’ production techniques there are
environmental and social benefits that will arise to the farm community using water from the
irrigation dams. / AFRIKAANSE OPSOMMING: Die stygende vraag na vis as gevolg van bevolkingsgroei, tesame met die stagnering van die aanbod
van vis vanaf natuurlike vangste het daartoe aanleiding gegee dat die oë van die wêreld op
akwakultuur gerig is om die gaping in die voorsiening van vis te vul. Akwakultuur het ontwikkel as
die enigste volhoubare manier om aan die groeiende vraag na vis te voldoen. Die vinnige
uitbreiding van akwakultuur het egter toenemende besorgdheid in die nadelige omgewingsimpak,
veral ten opsigte van akwakultuurafval, tot gevolg gehad. Die nethokstelsel wat tans deur
kleinskaalse forelboere in die Wes-Kaap in oop watergebaseerde sisteme gebruik word en die
vrystelling van afval in die wateromgewings wat onafwendbaar is, plaas ’n vraagteken oor die
langtermyn volhoubaarheid van die nethokstelsel forelboerdery in besproeiingsdamme in die Wes-
Kaap.
Die studie het ten doel gehad om geïdentifiseerde produksiestelsels wat deur akwakultuurboere
gebruik kan word om die akkummulasie van organiese afval in besproeiingsdamme te verminder, te
vergelyk. Die voorgestelde “skoon” produksietegnieke sluit in nethokke wat aan ’n opligstelsel
gekoppel word, ‘n semi-intensiewe drywende tenk- stelsel (“SIFTS system” in Engels) en ‘n
geïntegreerde akwakultuurstelsel. Met hierdie studie is bevind dat die geïntegreerde stelsel die mees
effektiewe manier is om afval te herwin en toon potensiaal om akwakultuur op ’n vohoubare pad te
plaas aangesien dit aan die volhoubaarheidsdimensies van geen emissie, voedingstofherwinning en
geïntegreerde produksie voldoen. Meganiese metodes van afvalherwinning soos die nethokopligstelsel
en die SIFTS-stelsel is effektief in die herwinning van vastestofdeeltjies, maar
opgeloste voedingstowwe word steeds in die omgewing vrygestel.
Die studie het voorts ten doel gehad om te bepaal of die ekonomiese, omgewings- en sosiale
voordele om afval uit besproeiingsdamme te herwin, groter is as die herwinningskoste van die
verskillende produksietegnieke. Modelle van kleinskaalse akwakultuurplase wat die drie
geïdentifiseerde produksiestelsels gebruik, is ontwikkel en aangewend om te vergelyk met ’n
nethokstelsel waar geen afvalherwinning gedoen word nie. ’n Vergelykende finansiële ontleding
van die gemodelleerde kleinskaalse forelboerderye met die verskillende produksietegnieke is
gedoen en daar is bevind dat enige een van die drie “skoon” stelsels finansieel lewensvatbaar is, met
die SIFTS-stelsel wat die hoogste vergoeding aan die boer bied, gevolg deur die geïntegreerde
stelsel, dan die nethokke aan ’n opligstelsel en dan die nethokstelsel sonder afvalherwinning.
Die tweede deel van die studie het van die voorwaardelike (“contingent”) waardasiemetode gebruik
gemaak om die omgewings- en sosiale voordele om afval uit besproeiingsdamme te verwyder, te
bepaal. Huishoudings het aangetoon dat hulle bereid sou wees om tot R40 per jaar te betaal om die
waterkwaliteit te verbeter vanaf ’n toestand waar eutrifikasie plaasgevind het na ’n toestand waar
die water vir besproeiing en akwakultuur geskik sou wees. Om die waterkwaliteit vanaf ’n toestand
geskik vir besproeiing te verander na ’n toestand geskik om in te swem, sou huishoudings bereid
wees om R16.67 per jaar te betaal. Indien water vanaf ’n toestand geskik vir besproeiing verander
sou word na ’n toestand geskik vir huishoudelike gebruik, sou huishoudings gewillig wees om
jaarliks R26.17 te betaal. Die “gewilligheid om te betaal” dui aan dat daar bo en behalwe die
finansiële voordele om van “skoon” produksietegnieke gebruik te maak, ook omgewings- en sosiale
voordele vir die plaasgemeenskap bestaan met die gebruik van die water uit die
besproeiingsdamme.
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An Assessment of Algae and cyanotoxins in small-holder Aquaculture farms in Vhembe, South AfricaTshifura, Rudzani Alice 21 September 2018 (has links)
MESHWR / Department of Hydrology and Water Resources / In South Africa, inland aquaculture is on the increase, especially among the rural communities. Thus aquaculture is able to provide a source of employment and improve rural incomes. This study assessed algae species and their cyanotoxins in small holder production in Vhembe district, Limpopo, South Africa. Thirteen study sites were selected to assess the algae species and their cyanotoxins. The water samples were collected in four quarters and analysed for water temperature, pH, total dissolved solids, Electrical conductivity, phosphates, nitrates, chlorophyll, cyanobacteria, cyanotoxins, metal species and quality of the water in the fish ponds. In the 1st quarter of the year there was variation in Water Temperature (23.7oC-31.4oC), pH (5.5-9.6), EC (3.82-46.8μS/cm), TDS (2.4-45 mg/L), Phosphate (0.0-1.09mgL-1), Nitrates (0.0-1.00mgL-1), Chlorophyll-a (5.8-11.5mg/m-3). In the 2nd quarter there was variation inwater temperature (22.4-25.0oC), pH (6.6-8.8.9), EC (19.23-21.47μS/cm), TDS (12.5-17.9 mg/L), Phosphate (1.64-1.84mgL-1), Nitrates (1.02-1.88mgL-1), Chlorophyll-a (4.6-15.6mg/m-3). In the 3rd quarter there was variation for water temperature (22.9-25.0oC), pH (7.5-9.1), EC (7.91-293.3μS/cm), TDS (11.7-180.9 mg/L), Phosphate (1.10-1.80mgL-1), Nitrates (1.28-1.84mgL-1),Chlorophyll-a (6.8-15.6mg/m-3). In the 4th quarter there was variation forwater temperature (23.5-30.3), pH (7.1-9.3), EC (18.24-623μS/cm), TDS (23.7-136.4 mg/L), Phosphate (1.45-1.99mgL-1), Nitrates (1.43-1.68mgL-1), Chlorophyll-a (6.6-25.9mg/m-3). The metal content of the fish pond water was variable throughout the year but with moderate levels of Al, Cd, Cr, Mn, Fe, Cu, Zn and Ba were found. The metal Fe, exceeded the DWAF guideline values during this first quarter. The presence of Cd in the fish pond water could be attributed to rainfall eroding the earthen embankments of the fish pond. The results of physico-chemical parameters promotes the growth of cyanobacteria in the fish ponds. Flow cam and SEM were used to identify the cyanobacteria species and most cyanobacteria identified are hazard to human health, fish and other aquatic organisms. Molecular technologies were used to identify cyanotoxins and there was no cyanotoxins detected which was concluded that during collection of water samples no cyanobacteria produced toxins. / NRF
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Impacts of cage aquaculture on the farm dam ecosystem and its use as a multipurpose resource : implications for irrigationDu Plessis, D. 12 1900 (has links)
Thesis (MScAgric (Conservation Ecology and Entomology)--University of Stellenbosch, 2007. / Small farm dams (< 20 ha) in the Western Cape Province provide adequate water conditions for
intensive cage production of rainbow trout (Oncorhynchus mykiss). A major environmental concern of
cage aquaculture, however, is the high inputs of nutrients via commercial diets and the subsequent
eutrophication of the water source. Eutrophication can result in the degradation of the general water
quality (increasing pH levels, oxygen depletion, increased hydrogen sulphide and free ammonia) and
shifts in the phytoplankton structure (increased biomass, single species dominance). Deterioration of
water quality will affect the success of the fish farming enterprise as well as the performance of
irrigation equipment by increasing the risk of clogging and corrosion. Water quality, phytoplankton and
zooplankton compositions were monitored at four sites from June 2005 to November 2006 to
determine the effects of cage culture on the farm dam environment, its associated biota as well as
irrigation water quality. The distribution of nutrients, nitrogen and phosphorus, was mainly influenced
by the stratification and mixing regime of the water bodies. Nutrient concentrations increased during
the winter mixing period while in the summer months, they seem to settle to the lower part of the water
column. Nutrient concentrations of production sites and reference sites were comparable except for
the ammonia levels that were significantly higher at the production sites. Phytoplankton corresponded
with nutrient availability resulting in high biomass during winter. In terms of biomass, phytoplankton
was approximately two times more abundant in production sites compared to reference sites.
Assemblage dominance by cyanophytes (Anabaena circinalis, Microcystis spp.) was found more often
in production sites, while reference sites were dominated by dinophytes (Ceratium hirundinella,
Peridinium spp.). Zooplankton biomass concurred with high phytoplankton biomass in winter.
Zooplankton assemblages in production sites sustained much higher biomass. Effects of cage culture
on irrigation water quality are evident from increased algal biomass and shifts in species composition.
These results indicated that at its present production level, cage culture had impacts on the farm dam
environment and irrigation water quality. The most significant evidence was given by increased
plankton biomass and single species dominance in production sites. However, these findings can not
solely be ascribed to the introduction of aquaculture as various other factors may also contribute to the
water quality of these ecosystems.
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