The use of treated brewery effluent as a water and nutrient source in crop irrigation
- Authors: Taylor, Richard Peter
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5390 , http://hdl.handle.net/10962/d1021265
- Description: Brewery effluent (BE) needs to be treated before it can be released into the environment, reused or used in down-stream activities. Current technologies used to address this concern at the experimental wastewater treatment plant at Ibahyi Brewery (SAB Ltd) include anaerobic digestion (AD), primary facultative ponds (PFP), high rate algal ponds (HRAP) and constructed wetlands (CW). The aim of this work was to determine if BE treated in these systems might be suitable for crop irrigation. A test crop, cabbage (Brassica oleracea cv. Star 3301), grew best on post-AD and post-PFP BE compared to those irrigated with post-HRAP or post-CW effluent. However, the yield was 13% lower than cabbage plants irrigated with a commercial nutrient solution and fresh water. The relatively high conductivity (3019.05 ± 48.72 μs/cm2) of BE may be the main factor reducing the cabbage yields. Post-HRAP and post-CW BE were the least suitable for irrigated crop production due to the higher conductivity and lower nutrient content of these treated effluents. After three months, soils irrigated with post-AD and post-PFP BE had a significantly higher sodium content and sodium adsorption ratio (3919 ± 94.77 mg/kg & 8.18 ± 0.17) than soil irrigated with a commercial nutrient solution (920.58 ± 27.46 mg/kg & 2.20 ± 0.05; p<0.05). However, this was not accompanied by a deterioration in the soil’s hydro-physical properties, nor a change in the metabolic community structure of the soil (p>0.05). After prolonged irrigation with treated BE, sodium is likely to build up in the soil and this can be expected to be accompanied by a deterioration in the soil physical structure. However, crops species such as millet (Echinochloa esculenta), lucerne (Medicago sativa) and saltbush (Atriplex nummularia) reduced the build-up of sodium in the soil. The results suggest that sodium was mainly removed from the soil through plant-assisted leaching. Of the crops grown, lucerne showed the most promise because it improved the soil physical properties, is able to grow well in alkaline environments, is a popular fodder crop and can be harvested multiple times from a single stand. Brewery effluent is more suitable for soil production systems than hydroponic production systems because the soil was able to act as a buffer against the high pH of post-AD BE, whereas in a hydroponics systems the high pH reduced the availability of key minerals to plants. In conclusion brewery effluent contains sufficient plants nutrients to support the growth of cabbages, saltbush, lucerne and millet. However the sodium content of BE is a concern as it accumulates in the soil, and in the long-term it may lead to soil degradation. It is suggested that the brewery change the pH neutralising treatment of BE from sodium hydroxide to potassium hydroxide, or dolomitic lime (calcium and magnesium carbonate) because this would reduce the introduction of sodium into the system, and would increase the suitability of BE for crop production, given potassium and calcium are plant nutrients. The benefits of developing this nutrient and water resource could contribute to cost-reductions at the brewery, more efficient water, nutrient and energy management, create job opportunities with the potential of improving food security in the local community.
- Full Text:
- Date Issued: 2016
Resource recovery options in brewery effluent treatment using activated sludge and high rate algal ponds: assessing environmental impacts
- Authors: Taylor, Richard Peter
- Date: 2020
- Subjects: Sewage -- Purification -- Activated sludge process , Sewage disposal plants , Sewage -- Purification -- Biological treatament , Sewage -- Purification -- Nitrogen removal , Brewery waste , Breweries -- Waste disposal , Microalgae -- Biotechnology , Algal biofuels
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/153746 , vital:39507
- Description: Wastewater treatment plants (WWTPs) are designed to clean effluents, but they also consume resources and produce waste. Various treatment technologies allow for the recovery of energy, nutrients and water from effluents turning this waste into products, which increases their sustainability and decreases the impact of WWTPs on the environment. There is a lack of literature which comprehensively compares the treatment performances, environmental impacts and beneficial downstream uses of the biomass generated by high rate algal pond (HRAP) and activated sludge (AS) treatment systems. This thesis aimed to compare (1) effluent treatment performance, (2) emissions and (3) downstream use of algae cultured in HRAP to sludge produced in AS and to obtain data to conduct a life cycle analysis (LCA) to compare the systems. The focus was on adding value to the effluent treatment process, while identifying the associated environmental impacts and contributing to the first ever zero-waste brewery effluent treatment system. Furthermore, these data were used to provide a basis to critically review and contribute to improving the methods used in the LCA of effluent treatment systems; particularly since this was the first wastewater treatment LCA that compared AS and HRAP using data collected from the same temporal and geographic location and from a single effluent stream. The electrical consumption water emission and land application of waste biomass caused the major environmental impacts of both treatment systems. The HRAP had less than 50 % of the electrical energy consumption (0.11±0.01 kW/m3 of effluent treated) compared to the AS system (0.29±0.11 kW/m3) which resulted in the technology having a lower climate change, photochemical oxidant formation, freshwater and marine ecotoxicity and fossil fuel depletion impact. It is imperative to understand the method of electrical energy (fossil fuel vs renewable) generation when conducting a LCA and deciding which technologies to use, since they have a major influence on the aforementioned impacts. The biogas yield of algal and sludge substrates was similar with an average gas production of 241 ml/g volatile solids fed. Biogas from algae fed digesters had a significantly higher methane content (64.73±0.81 %) and lower carbon dioxide content (22.94±0.24 %) when compared to WAS fed digesters (60.08±0.18 % and 27.37±0.43 %) respectively due to it being a less oxidised substrate. Swiss chard plants (Beta vulgaris) fertilised with anaerobically digested (AD) algae or sludge had a significantly higher mean biweekly yield (5.08±0.73 kg/m2) when compared to the inorganic-fertiliser control (3.45±0.89 kg/m2; p<0.0001). No difference was observed in the soil’s physical fertility when algae or sludge were applied to the soil (p>0.05). The HRAP produced more biomass (317.18±27.76 g/m3) than the AS (83.12±64.91 g/m3), which resulted in a significantly greater downstream production of biogas and fertiliser per volume of effluent treated. According to the LCA, this also resulted in the HRAP system having a higher terrestrial ecotoxicity, due to the greater volume of solids and thus heavy metals applied to the soil. This interpretation can be misleading, because the mass of heavy metals released into the environment is the same for both systems, with a greater portion being applied to the land in the HRAP scenario and discharged into fresh water in the case of AS. Future LCA models should clarify if these biomasses are going to be applied to a single piece of land or multiple sites as this will influence the risk of contamination via pollutant build up in the soil. The application of sludge or algae on soil increased the soil’s sodium concentration and sodium absorption ratio from 774.80±13.66 mg/kg to 952.17±34.89 mg/kg and 2.91±0.04 to 3.53±0.13, respectively. Regulations on the application of algae or sludge on agricultural soils should be altered to consider the limit values for sodium and future LCA’s associated with effluent treatment facilities should incorporate the possibility of soil contamination through sodium build-up. This work also conceptualised the importance of reporting water emissions in wastewater treatment LCA in as much detail as possible, because this had a significant influence on the eutrophication impacts on water systems. Reporting water emissions as total nitrogen underestimated downstream eutrophication impacts compared with those using nitrogen-species concentration (ammonia, nitrite, nitrate etc). A marine eutrophication sensitivity co-efficient should be included in future LCA models which accounts for the probability of nitrogen and phosphorus emissions entering the coastal environment as well as the vulnerability of the marine environment to eutrophication. Activated sludge systems are favourable for situations where space is limited, were there are inadequate options for biomass disposal (biomass not be used in agriculture or AD) and were electricity is generated from a renewable source; whereas, HRAP are more suitable under circumstances where electricity production relies on fossil fuel that carries a high environmental impact and where options are available to use the biomass for economic gain such as biogas and fertiliser production. This thesis contributes towards a zero-waste brewery effluent treated process. The HRAP and AS treated effluent for reuse in the brewery or in agricultural irrigation. The solids were anaerobically digested, and the carbon was recovered as a biogas, while the digestate was applied as an agricultural fertiliser. This allowed for the recovery of water, nutrients and carbon.
- Full Text:
- Date Issued: 2020
Distribution patterns of fishes in the head region of a turbid Eastern Cape estuary
- Authors: Ter Morshuizen, Leslie David
- Date: 1996
- Subjects: Fishes -- South Africa -- Eastern Cape -- great fish river -- Geographical distribution
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5261 , http://hdl.handle.net/10962/d1005105 , Fishes -- South Africa -- Eastern Cape -- great fish river -- Geographical distribution
- Description: Two and a half years of data were collected from the Great Fish River and estuary using seine nets and gill nets to determine the fish species composition within these regions. The head region of the Great Fish River estuary was found to have a rich fish fauna, with the euryhaline marine fish component totally dominating the catch in all three regions. Gilchristella aesiuaria was the single most common species and several euryhaline marine species were captured in freshwater for the first time. Physical parameters were also measured in an effort to ascertain the possible factors which may affect the distribution and length frequency of the most common species within this area. Salinity was found to be the single most important factor affecting the species composition, and the sampling area was consequently divided into three regions, viz. river (< I ‰), head (1-4 ‰) and estuary (> 4 ‰). In addition, it was determined that river flow rate during the month prior to sampling also had a profound effect on species composition in all three regions. Based on the available evidence it is suggested that for most species this is related to conductivity levels rather than flow per se.
- Full Text:
- Date Issued: 1996
Screening of the white margined sole, Synaptura marginata (Soleidae), as a candidate for aquaculture in South Africa
- Authors: Thompson, Ernst Frederick
- Date: 2004
- Subjects: Flatfishes -- South Africa , Aquaculture -- South Africa , Soleidae -- South Africa , Soleidae
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5207 , http://hdl.handle.net/10962/d1004523 , Flatfishes -- South Africa , Aquaculture -- South Africa , Soleidae -- South Africa , Soleidae
- Description: The white margined sole Synaptura marginata (Soleidae) was isolated as the most likely candidate for flatfish aquaculture in South Africa. The aim of the study was to screen the sole as a candidate aquaculture species by way of a comprehensive study of its biology and life history strategy and to identify possible "bottlenecks". The study was undertaken on the assumption that the biological data would provide valuable information for developing specific technologies that might be required for the farming of this species. Specimens were collected monthly by spearing along the Eastern Cape coast of South Africa between December 2000 and March 2002. Length-at-age data required for modeling the growth of S. marginata was obtained from sectioned otoliths. A Von Bertalanffy growth model with an absolute error structure best describes the growth for this species. The model parameters were: L∞ = 429.5 mm TL, K = 0.24 and t₀ = -1 .79 years. Analysis of gut contents showed that S. marginata feed exclusively on polychaete worms, mainly of the genus Morphysa. S. marginata shows a protracted summer spawning season of six months, from October to April. This was determined by the calculation of a monthly gonadosomatic index and a macroscopic maturity scale. Histological examination of the ovaries revealed five ovarian developmental stages. Size at 50% and 100% sexual maturity for females was calculated to be 235 mm TL and 300 mm TL (ca. 1.5 - 2.5 years of age) and all males> 154 mm TL were mature. S. marginata is a batch spawner, releasing a minimum of 3 batches of eggs per year. Relative fecundity is high (34000 eggs per year I kg) and this coupled with the protracted spawning season would make it possible to obtain adequate numbers of juveniles (for farming) for approximately five to six months of the year. Comparative analysis of the biological characteristics in relation to other soles farmed elsewhere in the world suggests that S. marginata is a suitable candidate for marine fish culture in South Africa.
- Full Text:
- Date Issued: 2004
Towards the development of a larval feeding strategy for the white-margined sole (Dagetichthys marginatus)
- Authors: Thompson, Ernst Frederick
- Date: 2014
- Subjects: Flatfishes -- South Africa , Soleidae -- South Africa , Soleidae -- Larvae , Soleidae -- Larvae -- Feeding and feeds , Soleidae -- Larvae -- Physiology , Artemia
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5364 , http://hdl.handle.net/10962/d1012982
- Description: The major bottleneck during the domestication of the white-margined sole Dagetichthys marginatus in South Africa has been low larval survival. The cause of this is not clear but considering current literature on flatfish culture and more specifically soleid culture, nutritional deficiencies are hypothesized to be the main possible cause. Following the importance of nutrition, the first aim of the research was to use an ontogenetic developmental approach to develop a species specific larval feeding strategy. Ontogenetic development of D. marginatus showed that weaning will take place at much later ages than other soleids currently being farmed. This makes the partial replacement of Artemia with a suitable inert diet in co-feeding strategies very important to cut the cost associated of live food production. This leads on to the second aim, in which an 'in vitro' approach was used to model the digestibility of Artemia, which could ultimately contribute towards designing inert feeds with similar digestibility characteristics to Artemia in the future. Obtaining nutrients from food is closely linked to the functional status of the digestive tract, the support organs and the external morphological characteristics required for the ingestion of live or inert feeds. Considering both morphological and physiological ontogenetic development, it is clear that D. marginatus follow a similar pattern to other soleids. Larvae can successfully feed on Artemia as early as 3 days after hatching but exhibit a slow metamorphosis into the juvenile stage when compared to other soleids. The absence of any detectable acidic protease activity during the first 45 days of development and the importance of exogenous enzymes from Artemia all points to limited capacity to digest artificial diets. Prior to modelling the 'in vitro' digestion of Artemia, digestive enzyme activity at different pH's were modelled using functional forms from the normal distributive category of functions. , As there is no substantiated information for the general effects of pH on enzyme activity in the literature for finfish larvae, three species occurring in the same bio-geographical region of Dagetichthys marginatus, namely Sarpa salpa, Diplodus sargus capensis and Argyrosomus japonicus were used to investigate this effect. The fitted parameters, namely the optimal pH and sigma (the slope around the optimal pH) showed two interesting results. When using a negative log likelihood ratio test to test for differences between species for a particular enzyme, the optimal pH for alkaline proteases (7.67), lipase (8.03), amylase (7.69) and phosphatase (9.84) activity was the same for all three species. Furthermore, the study illustrated the potential to detect dietary shifts during ontogenetic development based on changes in enzyme activity around the optimal pH using the sigma parameter. Sarpa salpa showed increased amylase activity and a decrease in protease activity around the optimal pH with increased size, corresponding to a change in diet from zooplankton to algae. The 'in vitro' modelling approach taken in this study was based on known enzyme interactions and dynamics which makes the results very interpretable. from Artemia is achieved based on gut evacuation time and enzyme levels. This 'in vitro' study furthermore clearly indicates the importance of exogenous enzymes from Artemia, contributing as much as 54 percent to protein digestion and 64 – 72 percent to carbohydrate digestion. This was however, only an initial investigation, and further expansion of the model is required to achieve a complete understanding of Artemia digestion and ultimately partial replacement with artificial diets. A feeding strategy for D. marginatus should therefore follow those of other farmed soleids, although there will be a general delay in implementation due to slower development. Problems can thus be solved and improvements made by transferring technology from other soleids to D. marginatus.
- Full Text:
- Date Issued: 2014
Videographic analysis of the Coelacanth, Latimeria Chalumnae, and associated habitats in the Isimangaliso Wetland Park, KwaZulu-Natal, South Africa
- Authors: Thornycroft, Rosanne Elizabeth
- Date: 2012
- Subjects: Isimangaliso Wetland Park , Coelacanth , Coelacanth -- South Africa -- KwaZulu-Natal , Habitat (Ecology) , Coelacanth -- Behavior -- South Africa -- KwaZulu-Natal , Coelacanth -- Habitat -- South Africa -- KwaZulu-Natal
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5333 , http://hdl.handle.net/10962/d1005179 , Isimangaliso Wetland Park , Coelacanth , Coelacanth -- South Africa -- KwaZulu-Natal , Habitat (Ecology) , Coelacanth -- Behavior -- South Africa -- KwaZulu-Natal , Coelacanth -- Habitat -- South Africa -- KwaZulu-Natal
- Description: Videography is a valuable tool in biological and ecological studies. Using video footage obtained during previous coelacanth surveys, this thesis investigated coelacanths and their associated habitats in the submarine canyons of iSimangaliso Wetland Park, South Africa. This thesis aimed to (1) describe the biological habitats within the submarine canyons, (2) determine coelacanth distribution within these habitats, and (3) assess the use of computer-aided identification to successfully identify individual coelacanths. Seven different habitat types were noted with the most distinctive being the canyon margins that consisted of dense agglomerations of gorgonians, wire and whip corals, and sponges. Results suggested that although substratum type has a great influence on invertebrate community structure in the canyons, depth is the principal factor. Coelacanths were associated with cave habitats within the steep rocky canyon walls. Habitat analyses allowed predictive classification tree models to be constructed. Depth, underlying percentage of rock, and percentage cover of gorgonians and sponges were the most important variables for determining coelacanth presence and absence. The overall correct classification rate for the model was estimated at 96.6%, correctly predicting coelacanth absence (> 99%) better than presence (60%). Because coelacanths have a unique spot pattern it was possible to quickly and accurately identify specific individuals photographically using computer-aided identification software. Without any manual intervention by an operator the software accurately identified between 56 and 92% of the individuals. Identification success increased to 100% if the operator could also manually select from other potential matching photographs. It was also shown that fish exhibiting a yaw angle not exceeding 60° could be accurately identified in photographs. Each of the sections presented in this thesis represent a possible step towards analysing coelacanth-related habitats, locating and then analysing new habitats. Steps include first locating a population and then performing a habitat analysis. Coelacanth location within the different habitats can then be determined allowing the development of predictive models to potentially identify possible locations of new populations. The final step is to identify individual fish within the population for assessing demographic parameters and population monitoring.
- Full Text:
- Date Issued: 2012
An investigation into the dietary requirements of Oreochromis Mossambicus fry and the formulation and preparation of a dry food for use in aquaculture
- Authors: Thorpe, Peter Stuart
- Date: 1989
- Subjects: Cichlids , Tilapia -- Nutrition , Aquaculture
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5184 , http://hdl.handle.net/10962/d1001960 , Cichlids , Tilapia -- Nutrition , Aquaculture
- Description: The need for developing a dry feed which satisfied the nutrient requirements of Oreochromis mossambicus fry was identified. The spawning and grading techniques which resulted in a higher fecundity and ensured uniformity within and between samples of fry are discussed. Preparation techniques were developed which met the physical requirements of fry feeds. An analysis of the flesh and yolk sac fry for amino acid composition was undertaken. The initial test diet was based on these results, as well as on the natural feeding ecology of the species. Feeding trials were undertaken and growth responses monitored to determine the optimum levels of the various dietary components. A feed was developed which gave superior growth to that obtained with natural food organisms. This feed consisted of Torula yeast (47%), Weider Super Protein (44.39%), Vitamin supplement (0.45% - multivitamin), additional vitamin C supplement (0.16%), Spirulina (5%), and methionine supplement (3%). An optimum particle size range for O. mossambicus fry (between 5 & 25mm) was established at 125-200um. The fry should be fed the following feed ratios depending on age: 30.4% body weight/day up to day 5, 30.6% body weight/day up to day 10 and 25.1% body weight/day up to day 15. An optimum feeding frequency of 8/10hr day was recommended. A feed conversion ratio of 1.24:1 and a protein efficiency ratio of 0.682:1 was obtained. Digestable energy of the feed was determined at 16.1 kj/g feed. The established dry feed is suitable for use in commercial hatcheries, and as a formulation for further research on the intensive rearing of O. mossambicus fry.
- Full Text:
- Date Issued: 1989
Aspects of the biology, ecology and population dynamics of Galeichthys feliceps (Valenciennes) and G. ater (Castelnau) (Pisces: Ariidae) off the south-east coast of South Africa
- Authors: Tilney, Robin Lewis
- Date: 1991
- Subjects: Catfishes -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5221 , http://hdl.handle.net/10962/d1005064
- Description: This thesis represents a detailed investigation into aspects of the biology, ecology and population dynamics of two endemic ariid species, Galeichthys feliceps and G. ater, off the southeast coast of South Africa. The two species are exploited as a by-catch in the commercial ski-boat fishery off Port Alfred, a fishery dominated by highly fecund sparid and sciaenid species. They collectively constitute approximately 10% of the total annual catch in terms of landed mass G. feliceps outnumber G. ater in the catches by a ratio of 3:1. The investigation was designed to provide the biological data required for stock assessment and to determine optimum management strategies for the two populations. The implications of their K-selected life-history styles for exploitation received particular attention. While the two species were sympatric and had similar depth distributions they were found to be allopatric with respect to their foraging habitats. G. feliceps foraged over sandy and muddy substrata in marine and estuarine environments. G. ater fed only on reef-associated species and did not utilise estuaries. Their feeding-associated morphologies were identical and both species preyed primarily on crustaceans (brachyuran crabs and isopods), echiurids, molluscs and polychaetes. The diet of G. ater was broader in terms of the number of species consumed. The two species are mouth-brooders with low fecundity. G. feliceps and G. ater produced a mean of 49 and 32 eggs each, per annum. The buccal incubation period was determined to be in the region of 140 days for G. feliceps. Embryos hatched after approximately 75-80 days and the young began exogenous feeding thereafter. The young fed intra-buccally on detritus provided by the parent. Adult buccal mucus may also have been used as a food source. Young were released at a total length of ± 55mm. Adult males ceased feeding whilst mouth-brooding. Body musculature, abdominal fat and liver reserves provided energy for basal metabolism and males lost approximately 28% of their body mass during buccal incubation. Females expended less reproductive energy than males. Catches were dominated by mature fish (76% in G. feliceps and 97% in G. ater). Females were significantly more abundant in catches during the spawning and mouth-brooding period. The female to male sex ratios were 1.65:1 and 2.23:1 for G. feliceps and G. ater respectively. Age and growth studies revealed that the two species mature at advanced ages (10 and 9 years for G. feliceps and 9 and 7 years for G. ater males and females respectively). They are long-lived, reaching ages in excess of 18 years in G. feliceps and in excess of 15 years in G. ater. Females live longer than males and grow larger. Yield-per-recruit and spawner biomass-per-recruit analyses demonstrated that G. ater were exploited below FO.1 at a level where spawner biomass-per-recruit was reduced to between 45% and 65% of the unexploited level. The G. ater stock was not adversely affected by current levels of fishing effort. For G. feliceps, both sexes were exploited beyond F₀.₁ where spawner biomass-per-recruit was reduced to between 30% and 22% of the unexploited level. G. feliceps were shown to be sensitive to relatively low levels of exploitation, a phenomenon attributed to their highly Kselected life-history style. Should the species become targeted for in the future, effort restrictions in the form of a closed season during the spawning and mouth-brooding period would prove effective in reducing effort and conserving the population sex ratio.
- Full Text:
- Date Issued: 1991
The effect of alginate supplementation on the growth, feed utilization, digestive enzyme activity levels, and intestinal morphology of juvenile South African abalone (Haliotis midae) fed formulated feeds
- Authors: Tlakedi, Thato
- Date: 2020
- Subjects: Abalones -- Feeding and feeds -- South Africa , Haliotis midae , Abalones -- Digestive organs , Abalones -- Morphology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/145279 , vital:38424
- Description: Alginate occurs abundantly in kelp and while a few studies have quantified the effect of kelp inclusion in formulated Haliotis midae feeds, none have researched the effect of alginate inclusion on the growth of abalone fed this feed. Feeding kelp to cultured abalone affects gut structure and modulates gut bacteria, aiding digestion by upregulating enzyme activity. This farm-based experiment compared the growth, feed utilization, digestive enzyme activity levels and intestinal villi structure between abalone (1-year-old, 10 - 20 mm shell length) fed kelp-supplemented (BK) or alginate-supplemented (BA) diets and abalone fed basal (B) and fresh kelp (K) diets for a period of eight months from June 2017 to February 2018. Growth and enzyme activities were also compared between abalone that experienced dietary changes and abalone that remained on their initial diets. The tested diets were: base diet (B, 34% protein), the same base diet supplemented with fresh minced kelp (0.90% kelp [dry mass, equivalent to 0.20% alginate]; BK), base diet supplemented with sodium alginate (0.20% alginate; BA) and a fresh kelp diet (K). Alginate or kelp inclusion in a formulated feed had no significant effect on the specific growth rates (SGR), linear shell growth rates (LGR), daily percentage feeding rates (PFR), feed conversion ratio (FCR), percentage mass gain (MG) and condition factor (CF) over the eight month trial period, compared to abalone fed the base diet. In October 2017, four months since the start of the trial in June, all the groups fed formulated feeds showed significantly higher average weight gain (8.42 ± 0.72 g to 8.86 ± 0.63 g) compared to the kelp-fed group (6.68 ± 0.43 g). However, no significant differences in the average weight gain were observed between abalone fed kelp and formulated feeds at the end of this study. Furthermore, there were no significant differences in the FCR and PFR between abalone fed the base or alginate diets and abalone fed the fresh kelp diet. However, the SW diet produced significantly lower FCR (1.00 ± 0.13) and PFR (0.78 ± 0.10%) compared to the kelp diet (10.6 ± 1.40% and 8.12 ± 1.01%, respectively). All formulated diets produced non-significant LGR, MG and CF compared to the kelp diet at the end of this study. Enzyme activity levels were compared between abalone fed the test diets in July and August 2017 and February 2018. There were no significant differences in the average alginate lyase specific activity levels between abalone fed formulated diets in July and August 2017. At the end of the trial, however, the alginate diet induced significantly higher alginate lyase specific activity levels (4.89 ± 1.64 mg.mg-1 protein) compared to the base diet (1.57 ± 0.98 mg.mg-1 protein), but showed no significant differences compared to the SW (3.78 ± 0.41 mg.mg-1 protein) and fresh kelp-only diets (4.00 ± 0.62 mg.mg-1 protein). The SW diet showed no significant differences in the alginate lyase specific activity levels compared to the base diet. There were no significant differences in the chymotrypsin activity levels between the test diets throughout this study. Alginate or kelp inclusion also had no significant effect on the intestinal structure compared to the base or fresh kelp diets. This was despite a higher degree of variability in microvilli height and width being observed in abalone fed the kelp-only diet, with microvilli visibly wider and longer than in abalone fed formulated feeds. Switching abalone between some diets significantly affected the average weight gain, MG, FCR and PFR, alginate lyase, chymotrypsin and cellulase activity levels compared to abalone kept on their initial diets. The inclusion levels of kelp and alginate used in this study were likely too low to affect abalone growth as higher inclusion levels, particularly of alginate, have been found to improve fish growth. This study concluded that minced kelp and alginate inclusion in a formulated H. midae diet did not affect the SGR, FCR and intestinal morphology, but significantly affected alginate lyase and chymotrypsin activity levels. Furthermore, changes in growth and digestive enzyme activity levels coincided with dietary changes. Consequently, higher inclusion levels, particularly of sodium alginate, and the effect of dietary changes on abalone growth and digestive enzymes must be investigated in future studies.
- Full Text:
- Date Issued: 2020
The conservation and management of freshwater fishes in the Greater Addo Elephant National Park
- Authors: Traas, Graham Ronald Louis
- Date: 2009
- Subjects: Addo Elephant National Park (South Africa) , Freshwater fishes -- South Africa -- Eastern Cape , Fishery conservation -- South Africa -- Eastern Cape , Fishery management -- South Africa -- Eastern Cape , Estuarine fishes -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5247 , http://hdl.handle.net/10962/d1005090 , Addo Elephant National Park (South Africa) , Freshwater fishes -- South Africa -- Eastern Cape , Fishery conservation -- South Africa -- Eastern Cape , Fishery management -- South Africa -- Eastern Cape , Estuarine fishes -- South Africa -- Eastern Cape
- Description: Freshwater fish are the most imperilled vertebrate group with a high projected extinction rate. In general, the world's freshwater ichthyofauna is in a poor state and is threatened by habitat destruction, pollution, the effects of alien species, damming, water extraction and overfishing. Within South Africa, legislation supporting the conservation of aquatic habitats and its associated fauna is strong, but there is a lack of capacity and poor co-ordination between agencies responsible for the conservation and management. The Greater Addo Elephant National Park (GAENP) includes the upper catchments of five of the Sundays River tributaries. Since the optimal method of conserving freshwater aquatic biota is to conserve the headwaters of either the river or its tributaries, there is an opportunity to conserve the native ichthyofauna of the Sundays River system. The principal objective of this thesis was, therefore, to provide information pertinent to the conservation and management of the fishes in the Sundays River system. Sixteen species of freshwater and estuarine fish were sampled, of which eight were alien. Species composition in each of the rivers, with the exception of the Kabouga River, had changed significantly from previous studies. The distribution ranges of several indigenous species had reduced, while those of some alien species was increased. Two species not previously recorded, Labeo capensis and Gambusia affinis, were sampled. Alien species were sampled from all the tributaries. Diversity indices and community assemblage models were identified as approaches for monitoring the ichthyofauna in this species depauperate system. Diversity indices were not recommended for use as a monitoring tool, as they provided insufficient detail on community composition and structure. A modified depletion estimator was applied to multiple pass electrofishing data to determine the effects of various physico-chemical variables on the absolute abundance of Pseudobarbus afer, an endangered species. Pseudobarbus afer density was found to be positively correlated to the presence of boulders. Where P. afer were present, they were abundant. Of the total sampled catch, 21.8% was comprised of alien fishes. Clarias gariepinus was the most successful invader having penetrated all but one of the tributaries. Micropterus salmoides changed the species composition of the Wit River significantly through predation, and is potentially the most dangerous of the alien species in the Sundays River system, capable of extirpating a population of P. afer in as little as three days. Only one man-made barrier to the upstream migration of alien fishes was present on the tributaries, and several addition barriers are required to safeguard the populations of indigenous fish in the headwaters of these tributaries. Several management and conservation tools are presented and discussed, including river rehabilitation, translocation, eradication of alien species, erection of barrier weirs and captive breeding programmes. Public awareness and education is stressed because without support from the communities surrounding the GAENP, management plans for conservation of the indigenous ichthyofauna will, in all likelihood, fail.
- Full Text:
- Date Issued: 2009
Morphological variation and its taxonomic implications for insular populations of Pseudocrenilabrus philander (Pisces: Cichlidae)
- Authors: Twentyman Jones, Vanessa
- Date: 1993
- Subjects: Cichlids -- Morphology , Cichlids -- Conservation , Freshwater fishes -- Conservation -- Africa, Southern
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5301 , http://hdl.handle.net/10962/d1005146 , Cichlids -- Morphology , Cichlids -- Conservation , Freshwater fishes -- Conservation -- Africa, Southern
- Description: The cichlid fish Pseudocrenilabrus philander is widely distributed in southern Africa. Many of the populations occur in small, insular, geographically isolated water bodies, some of which are in arid areas. These small allopatric populations have been isolated for thousands of years and gene flow between them is non-existent or severely restricted. Populations were found to be different in terms of coloration, size of individuals, sexual dimorphism and behaviour. This thesis involved the determination of the taxonomic status of these isolated populations, from a morphological point of view. This has been part of a larger project, involving genetic and behavioural studies, to determine whether the different populations are geographic races of a single species, or whether they are species. Heritability of the observed differences was tested by breeding through three generations under uniform laboratory conditions. The populations from which wild-caught individuals were drawn could be identified on the basis of colour. There were some differences in anatomy between populations, but none of these were entirely distinctive for a particular population. When bred under laboratory conditions, populations did not show a tendency towards uniformity, as would be expected if morphological differences were environmentally induced. However, there were slight changes in the oral and pharyngeal bone form which may be diet related. Although there are morphological differences between populations and between wild-caught and laboratory-bred populations, it is suggested that the populations of P. philander are not fully differentiated and thus in the stages of incipient speciation. other studies on P. philander have introduced an element of uncertainty in that they show different results. Behavioural work suggests that different populations would behave as different species if they were to become sympatric. Karyological and mitochondrial studies showed that there were no differences between populations. Protein electrophoresis showed that populations were genetically unique. Since the various species and subspecies of Pseudocrenilabrus have been based on morphological criteria, the approach and conclusions in this study are based entirely on morphological criteria. These studies have practical implications for conservation, as some of the small populations are threatened with extinction. If the differences between the populations were ecophenotypic (i.e. related to their environment), then threats to some populations would not affect the conservation status of the species as a whole. If, however, such differences were genetic (i.e. the populations have evolved separately), then the extinction of small, isolated populations could mean the loss of actual species. This study strongly suggests that populations are incipient species and thus should be conserved.
- Full Text:
- Date Issued: 1993
The biology and management considerations of abundant large cyprinids in Lake le Roux, Orange River, South Africa
- Authors: Tómasson, Tumi
- Date: 1983
- Subjects: Barbus Labeo Cyprinidae Freshwater fishes -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5206 , http://hdl.handle.net/10962/d1004518
- Description: The biology of three large cyprinid fishes, Barbus holubi, B. kimberleyensis and Labeo capensis, was studied in a large turbid man-made lake on the Orange River, South Africa. The influence of environmental fluctuations on population dynamics was examined in relation to biological adaptations. On this basis inferences were made about the effect exploitation would have on the populations, and management alternatives were considered. Lake Ie Roux is situated in a semi- arid area, downstream from another large reservoir, Lake Verwoerd. In the pristine river, flooding is seasonal, and floodwaters carry a heavy silt load. Lake Verwoerd acts as a silt-trap and changes in turbidity in Lake Ie Roux (Secchi disc readings range from 15 to 160 cm) are influenced by hydrological management and are not necessarily seasonal. Water temperatures in the regulated river connecting the two lakes depend on the pattern of water release, and fluctuations in Iake levels depend on management practices. Reproduction was studied by examination of gonads and from the distribution of newly hatched juveniles. Age and growth was interpreted from the reading of scales and otoliths. Relative year class strength, dispersal and mortality were monitored using catch data from a regular, standardized gillnetting survey. The Barbus species spawn in the regulated river in spring or summer. Spawning is coordinated for a large part of the population and B. holubi spawn four to six weeks earlier than B. kimberleyensis. The juveniles are 'initially found along the shoreline, but later move into the pelagic zone and disperse throughout the lake. Year class strength is dependent on time of spawning and a late spawning results in a poor year class. For this reason, year class strength of B. kimberleyensis is generally poor, but there is a greater variation in year class strength of B. holubi, which is the dominant large Barbus. The two Barbus species exploit the pelagic zone, visually predating on zooplankton. When turbidity increases large scale mortalities occur, especially in B. holubi. Mortalities more than compensate for the reduction in carrying capacity, and the size of the reduced population may be inversely related to initial abundance. Growth rate is similarly affected by turbidity and density, and size at sexual maturity in B. holubi is reduced when growing conditions deteriorate. Labeo capensis do not form a homogenous population in Lake le Roux. Spawning occurs throughout the lake, but is erratic, probably depending on local rainfall. At each locality, more than one spawning may occur during spring and summer because of temporal variation in gonadal development. Juvenile survival appears to be mainly dependent on water level fluctuations, and strong year classes were formed when the lake was filling during the first two years. Subsequent year classes were weak. Subadult and adult B. capensis are herbivorous and depend on autochthonous production for food. They are relatively sedentary, but when turbidity increases fish smaller than 200 mm disperse, probably in response to food shortages. Mortality rates may be accelerated but mortalities are not as high as in B. holubi. The growth rate of B. capensis is variable and depends on turbidity and population density. Size at sexual maturity remained relatively constant during the study period. B. holubi has a relatively fixed reproduction cycle in Lake le Roux and exploitation is likely to dampen fluctuations in population density. Population growth and stability could be further promoted through hydrological management. B. kimberleyensis does not represent an exploitable population in Lake le Roux, although the large size obtained by this species (>3 kg) may be an attraction to anglers. B. capensis does not appear to have the potential to withstand sustained exploitation because of its erratic and generally poor reproductive success. However, the species is long-lived and can sustain relatively high densities under harsh conditions because of its relatively low mortality rates. It was concluded that harvesting of B. holubi must be flexible to promote maximum benefits to commercial and recreational fisheries, but B. capensis which is not an angling species, should chiefly be exploited when catches of B. holubi are poor, but left to recover in between. An alternative management strategy would be to commercially exploit the fish populations of several reservoirs. A monitoring programme could be established to decide when each reservoir is to be exploited to see to the interests of commercial and recreational fishing alike.
- Full Text:
- Date Issued: 1983
Investigations into the dietary requirements of Clarias gariepinus larvae (Pisces : Clariidae) and the formulation and manufacture of an artificial dry feed for use in intensive larval rearing
- Authors: Uys, Wynand
- Date: 1984
- Subjects: Clarias gariepinus Catfishes -- Africa Clariidae Catfishes -- Africa -- Nutrition -- Requirements Clarias
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5205 , http://hdl.handle.net/10962/d1004446
- Description: The need for developing an artificial dry feed for Clarias gariepinus larvae was identified. Dry larval fishfeed requires certain physical properties. Techniques for manufacturing feeds which comply with these requirements were evolved and are recomended for practical use. The techniques that were used for artificial reproduction of C. gariepinus larvae are briefly discussed. The larvae were fed on various dietary formulations and their growth responses were monitored in order to determine their nutritional requirements. A feed was developed which gave superior results to those obtained with natural food organisms. This feed consisted of Torula yeast(69,8%), fishmeal(23,3%), vitamin supplements(O,9%), methionine supplement (150mg/kg), bactericide and preservatives. The feed particles were coated with a lipid supplement which was added at a ratio of 6% to the weight of the feed. The optimum particle size (diameter) for C. gariepinus larvae is 2,2% of their mean total length. The larvae should be given a feed ration of 25% of body weight per day at a frequency of once every four hours. A favourable feed conversion ratio of 1.1g of feed consumed per gram of larval weight gain was experienced. The established dry feed is suitable for use in commercial hatcheries and can be used as a standard and proven food source for further research on the intensive rearing of C. gariepinus larvae.
- Full Text:
- Date Issued: 1984
Aspects of the nutritional physiology and dietary requirements of juvenile and adult sharptooth catfish, Clarias Gariepinus (Pisces : clariidae)
- Authors: Uys, Wynand
- Date: 1990
- Subjects: Clariidae Catfishes Catfishes -- Nutrition-requirements Clarias
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5225 , http://hdl.handle.net/10962/d1005068
- Description: Past and current research on the biology and culture of the sharptooth catfish (Clarias gariepinus) has stimulated the development of its commercial production. At the inception of this project in 1985, it was decided that the development of an optimal dry feed was the most important step in developing a more complete culture technology for the species. The objectives of the project were, therefore, to investigate aspects of the nutritional physiology and dietary requirements of the species to provide the necessary information for the formulation of optimum economical feeds. A review of the natural feeding biology of the species provided valuable information with regard to its food preferences. From this information, and by estimating the nutritional composition of its preferred natural diet, it could be concluded that the animal requires a relatively high dietary protein content. This conclusion was substantiated by studies of the functional morphology of the digestive system (gross and fine structure). The characteristics of the digestive system and external anatomy were found to be typical of an opportunistic, omnivorous predator. The ontogenetic development of the digestive system is relatively fast, and enables the utilization of a variety of diets efficiently from an early stage. Since the ability of an animal to digest a given substance is predominantly dependent on the presence of appropriate enzymes the quantification and characterization of C. gariepinus digestive enzyme activities were investigated on an experimental basis. This work revealed that the animal has relatively high levels of digestive enzyme activities, and that its proteolytic enzyme activities correspond with those of other carnivorous fishes, while its starch digesting abilities correspond with those of specialized herbivores. Also, the high levels of lysozyme and alkaline phosphatase indicate an adaptation to detritivory, making this fish a truly opportunistic omnivore. Evidence was found to suggest that sharptooth catfish are able to re-absorb secreted digestive enzymes in the posterior section of its intestinal tract. It was shown that digestive enzyme activities were induced by food intake, and that no inherent rhythmicity in digestive activities seemed to occur. The development of digestive enzyme systems in the early life history of this animal was found to be also extremely rapid (complete within 10-16 days after hatching). It was also shown that artificial dry feed stimulates higher levels of digestive enzyme activities in larvae and juveniles than natural food. Although increased cellulase activity was found in larvae and juveniles that were fed on live zooplankton, the relative contribution of exogenous prey enzymes to protein digestion could not be ascertained. Specific nutritional requirements were investigated by means of feeding trials. The results of these trials confirmed the above indications regarding the dietary requirements of sharptooth catfish. It was concluded that for optimal growth and production performance, this animal requires a dietary protein content of 40-42%, a dietary lipid content of 10-12% and that diets should contain 14-16 kJ/g digestible energy. The optimum protein-to-energy ratio was found to be 26-29mg protein per kJ of digestible energy. Dietary requirements are evidently the same for juveniles and adults, except that younger fish require higher relative feeding levels. Finally, practical feed formulations were evaluated in terms of their economic feasibility. The results of these trials are presented along with recommendations on the formulation of commercial feeds for C. gariepinus. A computer program with which to implement least cost feed formulation by means of linear programming is provided.
- Full Text:
- Date Issued: 1990
The geographic stock structure of chokka squid, Loligo Reynaudi, and its implications for management of the fishery
- Authors: Van der Vyver, Johan Samuel Frederik
- Date: 2014
- Subjects: Squids -- Geographical distribution , Loligo fisheries -- Africa, Southern , Fishery management -- Africa, Southern , Squids -- Africa, Southern , Squid fisheries -- Africa, Southern , Loliginidae -- Africa, Southern , Fish stock assessment
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5363 , http://hdl.handle.net/10962/d1012973
- Description: It is currently hypothesised that the chokka squid (Loligo reynaudi) consist of a single stock. This was tested through a spatial comparison of the morphology of this species. Forty three morphometric characters were measured from 1079 chokka squid collected from three regions: the south coast of South Africa, the west coast of South Africa, and southern Angola. While no significant differences were found for the hard body parts, results from discriminant function analyses showed the soft body morphometric characters from each of the three regions differed, with an overall correct classification rate of 100% for males and 99% for females in all three regions. Due to the existing model being used to assess the resource currently being updated it was not feasible to apply this model to the area-disaggregated data from this study. Rather, the CPUE trends and catches from the area-disaggregated data were compared against those of the area-aggregated data, as a first attempt to discern any appreciable differences which would suggest the use of disaggregated data in future assessments. Both the trawl and jig CPUE trends from the area-disaggregated analysis differed only slightly from those of the area-aggregated data. Similarly, the spring and autumn biomass trends for the main spawning area (east of 22°E) followed the same trends as for the full area. It is therefore concluded that there is currently no need to assess the resource on an area-disaggregated basis.
- Full Text:
- Date Issued: 2014
Thermal tolerance and the potential effects of climate change on coastal intertidal and estuarine organisms in the Kariega Estuary and adjacent intertitdal coastline, Eastern Cape, South Africa
- Authors: Van der Walt, Kerry-Ann
- Date: 2020
- Subjects: Ectotherms -- Climatic factors , Ectotherms -- Effect of temperature on , Fishes -- Climatic factors , Fishes -- Effect of temperature on , Climatic changes -- South Africa -- Eastern Cape
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/148459 , vital:38741
- Description: Temperature changes due to the effects of climate change are evident on all continents and oceans. As a result, there is a growing concern over how marine ectotherms will respond to extreme or fluctuating environmental temperatures. Temperature changes have strong direct and indirect effects on individual, population, and ecosystem functioning traits. A multi-scale approach determining the thermal tolerance and performance of several marine ectotherms belonging to different coastal habitats is rarely considered in thermal physiology studies but is effective for an integrated ecosystem assessment. As such, for this thesis, I aimed to quantify and compare the thermal tolerance and performance of a range of coastal marine ectotherms (fish and macro-invertebrates) with different biogeographical distributions from estuarine, subtidal and rocky intertidal habitats to available and projected in situ temperature data. This was also undertaken to gauge the local vulnerability of each species across summer and winter in a warm-temperate region of South Africa. This was done using a multi-method physiological approach, which included the dynamic method (CTmax and CTmin), static respirometry and maximum heart rate fHmax). Results of the dynamic method on several fish and macro-invertebrate species indicated that there are differences in thermal tolerance according to taxonomy, biogeography and habitat for both summer and winter. Macro-invertebrate species generally had higher CTmax endpoints, lower CTmin endpoints, higher upper and lower breadths in tolerance, higher upper and lower thermal safety margins and higher thermal scopes than the fish species. This could be a result of the macro-invertebrate species studied being less mobile compared with fish species (which are able to move to more favourable conditions) as well as having broader geographical distributions. In addition, macro-invertebrates from the intertidal rock pool habitat (Palaemon peringueyi; Pernaperna) were more tolerant of high and low temperatures compared with the macro-invertebrates from the estuarine habitat (Clibanarius virescens; Parasesarma catenatum; Upogebia africana). Overall, macro-invertebrates, with the exception of Parechinus angulosus, investigated in this study indicated that current temperatures and projected climate change scenarios across seasons would not have a significant impact on them and that they are highly adaptable to changing temperature regimes. This sign of high tolerance was further supported by the heart rates of P. perna and P. catenatum under an acute increase in temperature (1.0 °C.h-1) which showed individuals of each species physiologically depressing their metabolism until a final Arrhenius breakpoint temperature was reached (TAB). Among the fish species investigated in this study, tropical species (Chaetodon marleyi; Kuhlia mugil) had the highest CTmax and CTmin endpoints when compared with the temperate (Diplodus capensis; Sarpa salpa), warm-water endemic (Chelon dumerili; Rhabdosargus holubi) and cool-water endemic (Chelon richardsonii) fishes. This suggests that due to their lower breadths in tolerance and thermal safety margins being small, tropical species may be less tolerant of cold temperatures and thermal variability, especially in the form of summer upwelling events which are expected to increase in intensity and frequency in this region as a result of anthropogenic climate change effects. On the other hand, however, if a temperature increase of 2.0 - 4.0 °C takes place at the end of the century as predicted by the Intergovernmental Panel on Climate Change (IPCC), it is likely that tropical species such as C. marleyi will become more common. Temperate species such as D. capensis and S. salpa were able to tolerate a wide range of temperatures (wide thermal scope) compared with the other fish species. These findings may suggest that D. capensis and S. salpa are thermally resilient and may be the least vulnerable to climate change effects and temperature variability. When evaluating the different life stages of D. capensis, however, using the dynamic method (juveniles and adults), static respirometry (juveniles) and maximum heart rate (adults), results suggested that juveniles of this temperate species will be more resilient to increases in ocean temperatures compared with the adults because they have a higher thermal tolerance (CTmax/TCRIT) and a greater metabolic scope (TOPT) at higher temperatures. For both juveniles and adults, temperatures beyond 28.0 °C (upper Tpej; Tarr) will have a significant impact on their physiology. Using a multi-scale and multi-method approach thus helped to identify which species or community may be vulnerable to the effects of climate change within shallow coastal environments in this warm-temperate climate change hotspot. Adopting this type of approach will assist policy makers in developing comprehensive climate change management frameworks for coastal ecosystems globally and around South Africa.
- Full Text:
- Date Issued: 2020
Prioritising native fish populations for conservation using genetics in the Groot Marico catchment, North West Province, South Africa
- Authors: Van der Walt, Kerry-Ann
- Date: 2014
- Subjects: Native fishes Fishery management -- South Africa -- North West Fish populations Fishes -- Conservation -- South Africa -- Western Cape
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/69102 , vital:29390
- Description: The Groot Marico catchment in the North West Province is a National Freshwater Ecosystem Priority Area (NFEPA) because it represents unique landscape features with unique biodiversity that are considered to be of special ecological significance. Three native freshwater species Amphilius uranoscopus, Chiloglanis pretoriae and Barbus motebensis, have high local conservation importance and B. motebensis is endemic to the catchment and is IUCN-listed as vulnerable. The main objective of this study is to contribute towards the effective conservation of these three species in the Groot Marico River system by assessing their genetic structure to determine whether tributary populations of the three species comprise of one genetic population or whether they are divided into genetically distinct subpopulations, in order to prioritise areas for conservation. The central null hypothesis was that there is no genetic differentiation between tributary populations (i.e., panmixia) of B. motebensis, A. uranoscopus and C. pretoriae in the Groot Marico catchment, North West Province. In total, 80 individuals per species were collected, targeting at least 10 individuals per population from a total of eight populations (seven tributaries and the Groot Marico main stem) and across the study area. Samples were collected by electrofishing and specimens were euthanized using an overdose of clove oil. A sample of muscle tissue was removed for genetic evaluation and the remainder of the specimens served as voucher specimens. For the genetic evaluation, mitochondrial (ND2, cyt b) and nuclear (S7) genes were used. Genetic techniques used were DNA extraction, polymerase chain reaction (PCR), purification and sequencing. From the 240 individuals collected, 123 sequences for B. motebensis, 111 sequences for A. uranoscopus and 103 sequences for C. pretoriae were analysed across all three genes. Statistical analysis included looking at cleaned sequences in order to obtain models using MODELTEST (version 3.06). Population structuring and phylogeographic analysis was performed in Arlequin (version 2000), TCS (version 1.2.1) and PAUP*. Results indicated that for B. motebensis the null hypothesis could be rejected as there were two distinct lineages (the Draai and Eastern lineages) that demonstrated significant divergence in both the ND2 and S7 genes, suggesting historical isolation. The low divergence in the mitochondrial cytochrome b gene (0% < D < 0.8%) suggests that this isolation is not very old and is probably not comparable to species level differentiation. The null hypothesis was also rejected for A. uranoscopus as there were also significant levels of differentiation between tributary populations resulting in the identification of two lineages (the Ribbok and Western lineages). However, for C. pretoriae, the null hypothesis could not be rejected as there was no genetic differentiation between tributary populations i.e., one panmictic population. Therefore, due to each species showing different genetic structuring within the tributary populations, more than one priority area for conservation needs to be implemented. These priority areas of conservation where therefore evaluated based on the current conservation status of the species (B. motebensis being vulnerable on the IUCN Red List), the number of Evolutionary Significant Units for each species and the overall genetic diversity of all three species in the Groot Marico catchment. In total, four tributary populations were conservation priorities areas, these were the Draai, Vanstraatens, Ribbok and Kaaloog tributaries. The Draai, Vanstraatens and Kaaloog tributaries were selected as priority areas for B. motebensis (B. motebensis is considered to be the most vulnerable of all three species). The Draai tributary was selected due to the B. motebensis population within the tributary showing isolation from the rest of the tributary populations. In order to conserve B. motebensis from the Southern lineage, the Vanstraatens and Kaaloog tributaries were selected. Reasons for selecting these two specific tributaries within the Southern lineage were that the Vanstraatens tributary had unique alleles (three Evolutionary Significant Units) for B. motebensis and the Kaaloog tributary had high genetic diversity (HD = 0.889, ND2 gene) when compared to the other tributary populations. The Ribbok and Vanstraatens tributaries were selected as priority areas for the conservation of A. uranoscopus. The Ribbok tributary was selected as it showed isolation from the rest of the tributary populations, as seen with the Draai tributary (B. motebensis) and the Vanstraatens tributary was selected to represent the Western lineage as it had the highest diversity for both genes (ND2 and S7). The Ribbok tributary has the highest prioritisation when compared to the Vanstraatens tributary. Chiloglanis pretoriae occurs within the Draai, Vanstraatens, Ribbok and Kaaloog tributaries, therefore by prioritising these tributaries for conservation, C. pretoriae will in turn be conserved.
- Full Text:
- Date Issued: 2014
Settlement and metamorphosis in the veliger larvae of the South African abalone Haliotis midae exposed to ambient grown biofilms treated with conspecific mucous
- Authors: Van Staden, Jefferson Luke
- Date: 2021-10-29
- Subjects: Haliotis midae , Biofilms , Haliotis midae Larvae Behavior , Haliotis midae Metamorphosis , Biosecurity , Aquaculture , Metamorphosis , Attachment mechanisms (Biology) , Mucous
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/192187 , vital:45203
- Description: The South African abalone, Haliotis midae, is a commercially important species of mollusc which contributes significantly to the value of the South African mariculture industry. One of the primary challenges experienced by abalone farmers is the consistent production of juvenile abalone (spat) in sufficient volumes to keep stocking farms and facilitate expansion of the industry. One of the key production bottlenecks of H. midae is achieving adequate levels of larval attachment and metamorphosis (settlement). The larvae of H. midae are settled on polycarbonate plates which have been pre-conditioned with biofilms in seawater which is pumped ashore onto farms. The seasonal variability in settlement success reported by hatchery managers in South Africa is hypothesised to be as a result of different diatom species compositions colonising the settlement plates at different times of the year, with settlement success being lowest during the winter months. The following study investigated whether the addition of conspecific mucous to biofilms could result in elevated settlement success, and whether there was potential for sterilisation of this mucous. A novel method of mucous application, spraying it onto the plates as opposed to pre-grazing, was tested in settlement assays and the trials revealed the following results: • The addition of H. midae mucous induced significantly more larvae to attach to settlement plates, when mucous was harvested around the spawning season. • Elevated attachment of larvae on mucous treated plates did not result in more post-larvae occupying the plates at the end of trials, and increased mortality is likely attributed to introduction of pathogens in conjunction with mucous. • No increase in the final proportion of settled larvae which had metamorphosed or the rate at which they metamorphosed was observed between mucous application treatments and biofilm only treatments. Subsequent trials assessed whether methods of mucous handling could reduce the biosecurity risk associated with mucous use, and so mucous was either UV irradiated or autoclaved. These trials revealed the following findings: • No difference in attachment was seen between any treatments, including the untreated mucous. This is contrary to the findings of our initial experiments and illustrates that the attachment-inducing properties within mucous may be seasonally expressed. ii • Numbers of observed larvae/post-larvae on plates applied with UV and autoclaved mucous where less stable than biofilms only, especially in the second trial, illustrating that mucous still presents a biosecurity risk even after undergoing these handling methods as it may act as a substrate on which pathogenic bacteria could colonise. , Thesis (MSc) -- Faculty of Science, Ichthyology and Fisheries Science, 2021
- Full Text:
- Date Issued: 2021-10-29
Evaluation of Baited Remote Underwater Video Systems (BRUVS) for monitoring fish communities in Lake Malawi/Niassa
- Authors: Van Wyk, Angus
- Date: 2020
- Subjects: Underwater videography -- Malawi , Chambo -- Malawi -- Monitoring , Fishes -- Malawi -- Monitoring , Oreochromis lidole -- Malawi -- Monitoring
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/145546 , vital:38448
- Description: Baited Remote Underwater Video systems (BRUVS) have become a well-established in-situ monitoring technique in clearwater aquatic ecosystems. The relatively low cost, nondestructive and non-extractive nature of this technique permits BRUVS to be employed in a wide range of habitats. To date, the vast majority of studies using BRUVS technology have been conducted in marine habitats. Subsequently, BRUVS applications in freshwater habitats are scant, and techniques are not well developed. The primary objective of this thesis was to address this knowledge gap and develop standard operating procedures for BRUVS employment in Lake Malawi/Niassa and explore the potential of BRUVS as a monitoring tool for fish communities in the African Great Lakes. Eight easily identifiable species groups, representative of Lake Malawi/Niassa inshore fish communities, were used to develop the technique. The optimal BRUVS deployment time to obtain 95 % species accumulation was achieved in a 15-minute recording period. Power analysis, using a pre-determined 80 % power, a confidence interval of 95 % and a significance level of < 0.05 was used to determine annual sampling effort requirements for each species group. The power analysis was performed to detect a 10 % change in abundance over a hypothetical 10-year monitoring scenario. In areas where fish abundance was lower, the sampling effort required to monitor key fisheries species was significantly higher. For example, Chambo, the local Oreochromis (Nyasalapia) species flock, required an annual sampling effort of 120 deployments in Malawi compared to 56 in Mozambique ( < 0.05). Chambo had a higher detection probability in areas of lesser fishing pressure and were found in higher abundances in deeper, less accessible habitats. Deep-water (> 20 m) and rocky habitats were most important in explaining Chambo abundance and detection probability. The size-structure of Chambo in Lake Malawi/Niassa reflects size-specific depth and habitat migrations. Larger Chambo were observed aggregating in waters deeper than 20 m and a broader size range of individuals were observed utilising structured habitat. The effects of fishing are apparent in the size-structure of Chambo in the areas sampled. In study areas exposed to greater levels of fishing pressure – such as Malawi, the BRUVS detected significantly fewer individuals within sexually mature size classes, and the average size was smaller than in areas with less exploitation.
- Full Text:
- Date Issued: 2020
Towards the development of a protocol for the selection of probiotics in marine fish larviculture
- Authors: Vine, Niall Gordon
- Date: 2005
- Subjects: Marine fishes -- Larvae Bacteria Fishes -- Microbiology Fish culture
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5329 , http://hdl.handle.net/10962/d1005175
- Description: Manipulation or control of the microbiological aquaculture environment has been identified as an important focus area for future hatchery development. Subsequently, alternatives to obtain control of the microbiological environment are being sought of which the field of probiotics appears highly promising. Probiotics are usually selected based on various in vitro characteristics, however, the methods used differ and are sometimes unsuccessful due to poor experimentation. The aim of this work is to contribute towards the development of a protocol for the in vitro screening of bacterial candidate probiotics for marine fish larviculture. To reduce the number of candidate probiotics to be tested in vivo, various in vitro experiments need to be conducted, each screening for a particular mode of action – antagonism towards pathogen through production of antimicrobial compounds, growth and attachment to fish intestinal mucus, and the production of other beneficial compounds such as vitamins, fatty-acids and digestive enzymes. A total of 108 bacteria species were isolated from the digestive tract of the adult common clownfish, Amphiprion percula to screen for potential probiotics to be used in clownfish larval rearing. The antagonistic compounds assay identified twelve isolates which showed antagonism towards two or more aquatic pathogens. This was followed by an in vitro test that involved growing the organisms in fish intestinal mucus and modeling their growth parameters. A ranking index (RI) was developed using the lag period (λ) and doubling time (td) of the organism, where (1over λ x td) x 100. Five candidate probionts (AP1-AP5) with varied growth parameters were used for further in vitro experiments. The attachment to mucus assay introduced a novel tool for quantifying competition for attachment sites between candidate probionts and pathogens on mucus. Candidate probiont Pseudoalteromonas AP5 reduced the attachment ability of Vibrio alginolyticus when added before the pathogen and partially out-competed the pathogen for attachment sites when added second. In vitro screening for the production of beneficial compounds tested the candidate probiotics’ ability to produce digestive enzymes - trypsin, lipase and alkaline phosphatase as well as carotenoids and vitamin C. Candidate probiont Pseudoalteromonas AP5 produced high levels of the enzymes (98.2, 34.1 and 91.3 mU product liberated.ml⁻¹, respectively) and contained carotenoids while Kocuria AP4 contained carotenoids but produced low quantities of enzymes (7.8, 0 and 59 mU product liberated.ml⁻¹, respectively). None of the candidate probiotics produced vitamin C. To eliminate potential pathogenic or toxic candidate probionts, Artemia nauplii were exposed to each candidate probiont and the percentage Artemia mortality after 24-hours was determined. Candidate probiont AP2 caused high mortality of Artemia nauplii (98.4%) and was excluded from further studies. Identification of candidate probionts AP3-AP5 was performed using 16S-rDNA molecular techniques and the bacteria were assigned the names Bacillus AP3, Kocuria AP4 and Pseudoalteromonas AP5, respectively. Two methods of larval probiont delivery were tested – attachment to Artemia, and in-water delivery. Attachment to Artemia was high for both Kocuria AP4 and Pseudoalteromonas AP5 (7.2 x10³ and 2.7x10⁴ bacteria.nauplius⁻¹, respectively) while the in-water viability experiment showed that Kocuria AP4 comprised 23.9% of the total culturable water microflora after 24 hours while Pseudoalteromonas AP5 contributed 100%. To validate the findings from the in vitro experiments, in vivo trials using clownfish larvae were performed. Of the four candidate probiotics tested, only Kocuria AP4 showed potential to increase larval survival. In vitro tests produced a better understanding of the possible mode of action and strategies of competition between bacteria, however, the number of criteria in which a candidate probiont is successful in vitro may not be the best predictor for its effectiveness in vivo. Commercial studies that reduce between-treatment variation are required to test predictions about the most suitable probiont or combinations thereof.
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- Date Issued: 2005