Thesis (M.Sc. (Aquaculture)) -- University of Limpopo, 2012 / The feeding habits of a macrophagous fish, Tilapia rendalli, were investigated at an oligotrophic dam that has no macrophytes, Flag Boshielo Dam. This dam supports a significant population of the macrophagous, Tilapia rendalli. The diet of T. rendalli was investigated by examining the frequency of occurrence of different food items in the stomach of the fish over a period of twelve months. A size related dietary shift was evident. The diet of juvenile fish (<5 cm) was dominated by zooplankton and the diet of adult fish (>15 cm) was predominantly marginal vegetation, particularly Cyperus sexangulasris and Panicum schinzi. However, dietary overlaps between the different size groups were evident. The diversity of food items increased with fish size until the fish were 15 cm in length and thereafter declined as the fish predominately fed on marginal vegetation. Scales were used to determine the age of T. rendalli. Age at length data was fitted to the Von Bertalanffy growth model, which showed that males grew faster and attained a larger size than females. The growth of T. rendalli in Flag Boshielo Dam was comparable to those reported in other dams with macrophytes. It is inferred here that the absence of macrophytes is not a limiting factor in the growth of T. rendalli in lentic ecosystems. The ability of T. rendalli to achieve good growth rates when feeding on marginal vegetation prompted a subsequent study where its utilisation of readily available plant diets was evaluated under culture conditions. The culture of macrophagous fish that naturally feed on plant diets may be the solution to reduce the current dependence on fishmeal. Fishmeal is not only expensive, but its supply is not always guaranteed. This study focussed on the growth performance, gastric evacuation rate, gastric transit time and carcass composition of Tilapia rendalli fed fresh plants, to determine the extent to which T. rendalli can utilise fresh plants. Kikuyu grass (Pennisetum clandestinum), cabbage (Brassica oleracea), duckweed (Lemna minor), vallisneria (Vallisneria aethiopica) and fishmeal pellets (control) were offered ad libitum to duplicate groups of T. rendalli for 224 days. Specific growth rate (SGR), protein efficiency ratio (PER) and food conversion ratio (FCR) were used to determine the growth performance. Fish fed kikuyu grass attained a significantly (P<0.05) higher SGR and a better FCR than those fed on the other plant diets. Fish fed vallisneria lost weight. The serial slaughter method showed that vallisneria was vii evacuated significantly (P<0.05, ANCOVA) faster and was eaten in significantly (P<0.05) higher quantities than the other diets. Kikuyu grass was evacuated much more slowly and eaten in lesser amounts than the other plant diets. The low energy content (14.74 MJ/kg) of vallisneria may explain its faster evacuation and high consumption levels. Digestibility studies indicated that T. rendalli is capable of breaking down both cellulose and fibre. Fish fed kikuyu grass had higher protein levels, higher omega-3 fatty acids (25.13%) and higher mineral content than those fed on the other experimental diets. Fishmeal fed fish had the lowest content of the omega-3 fatty acids (2.52%). T. rendalli performed better when fed plant diets with higher protein and energy contents. The good growth performance and carcass quality of T. rendalli fed on kikuyu grass, led to another study where the use of kikuyu grass meal as a dietary protein replacement for fishmeal in practical diets for T. rendalli was evaluated. To determine the optimum substitution level, kikuyu grass meal was used to replace 20, 40, 60 and 80% of fishmeal in isonitrogenous (CP =16.70%) and isocaloric (GE =15.20 MJ/kg) diets. The test diets were fed to triplicate groups of fish held in 1 m3 fibre glass tanks at 10 (36 ± 2 g) fish per tank for 60 days. The best specific growth rate (1.60 g/day) and feed conversion ratio (1.86) were recorded for fish fed diets with 20% kikuyu grass meal. The lowest specific growth rate (1.29 g/day) and feed conversion ratio (2.56) were recorded for fish fed diets with 80% kikuyu grass meal. When the level of kikuyu grass meal was more than 20% in the diet, growth performance was reduced. However, there were no statistically significant differences in the growth performance indices measured across the tested diets. The observed reduction in growth for diets containing higher kikuyu grass meal is explained by the decreasing amino acids levels (particularly methionine and lysine) and increasing fibre content. The results from the growth trials suggest that kikuyu grass meal is a suitable protein replacement for the expensive fishmeal in T. rendalli practical diets when it constitutes up to 20% of the dietary protein.

Resumo: O objetivo deste estudo foi avaliar o efeito sub-letal do sulfato de cobre para a tilápia, na concentração de 0,5 e 2,0 mg.L-1 durante exposição e recuperação e determinar a toxicidade aguda para Ceriodaphnia dubia e para a alga Pseudokirchneriella subcapitata. Foram realizados dois ensaios (ensaios I e II) utilizando jovens de tilápia com peso médio de 38,29 g. Determinou-se neste estudo as concentrações de cobre nas brânquias, fígado e músculo dos animais, foram feitas também análises hematológicas, imunológicas, bioquímicas e histopatológicas durante exposição ao sulfato de cobre e posterior recuperação. Para o teste de toxicidade com C. dubia e P. subcapitata foram utilizadas as mesmas concentrações de sulfato de cobre do ensaio com peixes. Os cladóceros e as algas foram expostos a diluições dessas concentrações durante sete e três dias, respectivamente. Para a C. dubia observou-se a mortalidade e o efeito sobre a reprodução dos mesmos. Já para as algas foi observado o efeito inibitório sobre a taxa de crescimento. A exposição ao cobre no ensaio I e II resultou em acúmulo significativo de cobre nos tecidos analisados, com exceção do músculo. E no período de recuperação os valores de cobre permaneceram altos. O sulfato de cobre não provocou alterações hematológicas. Por outro lado, causou diminuição da capacidade fagocítica dos macrófagos de peixes expostos à concentração de 2,0mg.L-1 de CuSO4 no ensaio I. O cobre também causou diminuição da concentração de GSH. Com relação às análises histopatológicas houve alteração nas brânquias e hepatopâncreas em ambos os ensaios. Os resultados do teste ecotoxicológico com C. dubia P. subcapitata mostrou que o sulfato de cobre causou toxicidade aguda para estes organismos. O uso desse produto na aqüicultura pode comprometer o cultivo, uma vez que ocorreram danos a saúde dos peixes ... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The copper sulphate is one of the most widely used chemicals for the control of parasites and for the control of phytoplankton in aquaculture. The purpose of this study was to evaluate sublethal effects of concentrations of copper sulphate on tilapia. In addition, ecotoxicity of this compound was determinate for microcrustaceans Ceriodaphnia dubia and the alga Pseudokirchneriella subcapitata. The biomarkers evaluated in this study were copper bioaccumulation in tissues, hematological, immunological, biochemical and histopathological parameters. The copper toxicity for microcrustacean C. dubia, was evaluated with acute tests through mortality. The exposure to copper in the experiments I and II resulted in significant accumulation of copper in the tissues, except for the muscle. In the recovery period, the copper values of remained high in all tissues. The haematological parameters were not affected by the copper sulphate. However, was observed in experiment I a significant change in the phagocytic capacity of macrophages in fish exposed to concentration 2.0 mg CuSO4.L-1. Copper sulphate also caused biochemical changes in both experiments. It was observed that this chemical causes a decrease in the concentration of GSH. The histopathological analysis showed hyperplasia and secondary lamellae fusion in the gills, and necrosis of the hepatopâncreas in both experiments. The tests results with C. dubia and P. subcapitata showed that copper sulphate caused acute toxicity to these organisms. This study showed that copper sulphate has caused chronic toxicity in fish and acute toxicity to algae and microcrustaceans. These results indicate that the pollutant can act at different trophic levels / Orientador: Maria José Tavares Ranzani Paiva / Coorientador: Julio Vicente Lombardi / Banca: José Roberto Ferreira / Banca: Fabiana Pilarski / Banca: Claudinei da Cruz / Banca: Monica Accaui Marcondes de Moura e Mello / Doutor

Ce travail consiste en un suivi physico-chimique et biologique d'étangs du Centre-Ouest ivoirien.<br />Son but est de déterminer un mode de gestion optimisant la production piscicole (Oreochromis niloticus , Heterotis niloticus et Heterobranchus isopterus ) compte tenu des contraintes qui pèsent sur les paysans. A la différence des zones périurbaines, l'utilisation d'intrants est très limitée, voire impossible en zone rurale. Les modèles piscicoles sont donc extensifs, la production dépendant exclusivement de la richesse naturelle des étangs.<br />Leurs caractéristiques sont très différentes, chacun présentant une nette individualité. Il existe en fait une grande variabilité géographique (qualité de l'eau du bassin versant) et saisonnière (température, débordements en saison des pluies etc.). Des perturbations exogènes locales et des apports fertilisants plus ou moins importants contribuent à cette diversité. Les caractéristiques communes à tous les plans d'eau sont une température élevée (>23°C) et un pH légèrement acide (≈6).<br />En permettant le développement du périphyton, l'acadja (récif artificiel) favorise la croissance de O. niloticus et H. niloticus . Le périphyton peut représenter une importante ressource nutritive (jusqu'à 35 μg.cm-2 de chlorophylle a ) à condition que le phytoplancton ne soit pas trop abondant. Parmi les fertilisants testés en station pilote, l'urée a donné de bons résultats de production piscicole (3-4 t.ha-1.an-1). Son utilisation a cependant provoqué quelques poussées d'azote ammoniacal (6 mg.l-1) et semble favoriser les proliférations de cyanobactéries.<br />L'alimentation des cichlidés est essentiellement d'origine périphytique et benthique, comme cela ressort de l'inventaire des contenus stomacaux.<br />En tenant compte des connaissances acquises au cours de ce travail, une approche basée sur l'étude du comportement alimentaire des poissons est proposée et des suggestions sont faites concernant des recherches futures : étude des relations entre le plancton, le périphyton et le benthos notamment. Ces résultats devraient ainsi permettre de stimuler efficacement les dynamiques paysannes actuelles.

This investigation explored the use of microcosms as a tool for studying the dynamics of tropical aquaculture ponds. The potential use of rabbit excreta as a pond fertilizer in integrated farming systems was also investigated. Twelve insulated fiber glass tanks were utilized as microcosms to simulate earthen ponds. Seven hand-sexed Nile Tilapia O. niloticus) were stocked per tank, and microcosm performance was observed for a 90- day experimental period. Three rabbit excreta loading rates corresponding to 50 and 75 kg/10,000 m³ /day, and a continuously adjusted manure loading rate were assessed. The fertilizer treatments were compared to a control treatment where fish were fed on a prepared food. Water quality variables and fish performance were regularly monitored. Nitrogen and phosphorous content of rabbit excreta were measured. The dynamics of the microcosms were similar to warm water earthen ponds with respect to physical and chemical characteristics. Statistical differences were detected between control and fertilized treatments in relation to dissolved oxygen levels, net primary productivity, total alkalinity, total ammonia and orthophosphate levels. Primary productivity was influenced more by light intensity and penetration than by nutrient limitation. Rabbit excreta overloading was observed in the 75 kg treatment. Fish growth was greatest in the control treatment, but it was not statistically different from the continuously adjusted fertilizer treatment (Pondclass) (0.0065 and 0.0056, respectively). Low daily fish gains were observed in the 50 and 75 kg treatments. Low dissolved oxygen and high total ammonia were concentrations resulted in low weight gains and condition indices of fish in the 50 and 75 kg treatments. Extrapolated fish yields corresponded to 6,205, 4,563, 3,686, 4,869 kg/ha/year for control, 50 kg, 75 kg and Pondclass treatments, respectively. The observed yields are comparable with field experiences in real ponds. The continuously adjusted treatment showed the lowest manure conversion ratio (3.85) in the fertilized treatments. The nitrogen content of rabbit excreta varied according to rabbit size, presence or absence of urine plus water waste, and food droppings. Urine plus water waste provided 28 % of the total nitrogen content in rabbit excreta, whereas food droppings provided 12 %. Rabbit urine may play an important role in aquacultural systems because it contains a large fraction of nitrogen in inorganic forms which are readily utilized for algal growth. Other rabbit excreta characteristics such as buoyancy may be advantageous in aquacultural systems. Rabbit excreta is a potentially rich source of fertilizer for use in fish ponds. / Graduation date: 1992

Neurotransmitters are widely distributed in the central nervous system of tilapia during development. In the present study, the effects of gonadal steroids, temperature, and neurotransmitters on the development of central neurotransmitter systems in tilapia, Oreochromis mossambicus, were investigated. Exogenous E2 before 10 days posthatching resulted in an inhibitory effect on the activity of central 5-HT system via decreasing TPH activity and increasing MAO activity, a decrease of the gene expression of brain aromatase and ERa, which is involved in the feminization. The masculinizing actions of 17a-methyltestosterone (MT) are most potent later at up to day 20 of age, and may depend on MT-induction of aromatase activity, aromatase mRNA gene expression and estrogen receptor-b mRNA gene expression. The development of central neurotransmitter systems is influenced by aquatic temperature during its respective restricted period. The influence of both lower and elevated temperatures on the neurotransmitter activity, either increasing or suppressing, is dependent on its developing stage. Neurotransmitters have an effect to influence the development of central neurotransmitter and this effect may mediated by the neural proliferation.

Expressed sequence tags (ESTs) are derived from the developing tilapia brain was established in our lab. There are 9 transcripts were identified as thermosensitive/Neural development-related gene. The effects of different temperatures on the ontogenetic expression of these thermosensitive/Neural development-related gene during the critical period of brain sexual differentiation were investigated in the present study. The ontogenetic expression of inhibitor of DNA binding/differentiation protein 2 (Id2), thermosensitive/Neural development-related gene, were enhanced by both lower (20¢J) and higher (32¢J) temperatures before 10 days post-hatching. In this study, bioinformatics were searched for Id2, which is a gene with 738 bp of patial cDNA sequence, open reading frame (ORF) is 411bp, and deduced 137 amino acids of protein sequence. The protein of Id2 was expressed in a prokaryotic system, BL21 (Escherichia coli) and purified with Ni-NTA affinity chromatography. Also, the ORF of Id2 was cloned into pEGFP vector, and plasmid (pEGFP-Id2) was transfected into the eukaryotic system, mouse neuroblastoma cell (Neuro-2a cell). The distribution of Id2 expressed in the Neuro-2a cell was identified by fluorescence microscopy.

Thesis (M. Phil.)--University of Hong Kong, 1974. / Offset from typescript.

Eradicating poverty, malnutrition, and the burden of disease have been included as three of the major issues facing the world. The United Nation member countries, having set forth the Millennium Development Goals, have committed themselves to solving these problems. Two major factors which affect solutions to these problems are increasing water stress and implementing improved sanitation. Integration of tilapia aquaculture and reuse of wastewater has been suggested as a solution which addresses both of these factors. The objective of this study is to examine the feasibility, and explore the benefits and drawbacks, to implementing small community wastewater fed (WWF) aquaculture systems in the developing world. The water quality characteristics of treated effluent from nine wastewater treatment (WWT) plants were compiled from other studies. The concentration of total nitrogen in the effluent and the flow rate were of most importance, as they were used to calculate the nitrogen loading at each WWT plant. The nitrogen loading was then used to estimate the total pond size which could be supported by each WWT plant, the expected yearly yield for tilapia, and the percentage of the population who would benefit from provision of protein associated with the integration a fish farming system with the WWT plant. Results show that WWF, semi-intensive tilapia culture can provide 10 grams per day of dietary protein for 11% - 52% of the population of the communities in this study when integrated with a community managed wastewater treatment system. To assess potential risks to human health, associated with WWF aquaculture, the level of fecal coliform (FC) contamination was compared to the standard set by the World Health Organization; less than 105 FC per 100 mL for reuse in fish ponds. The level of FC contamination in the WWT plant effluents ranged from 653 to 1.78 × 105 FC per 100 mL, exceeding this standard. Given the context, the level of fecal coliforms should not rule out integrated reuse and aquaculture as an option. The nutrients found in wastewater are valuable resources in tilapia culture; therefore, allowing their persistence through treatment for reuse, while optimizing wastewater treatment technologies for pathogen removal is an appropriate solution for small communities in developing countries for reducing poverty, malnutrition, and disease burden of waterborne illnesses.

published_or_final_version / Botany / Master / Master of Philosophy

Various aspects of the ascorbic acid (vitamin C) nutrition of Oreochromis niloticus and O. mossambicus are considered in this treatise. The activity of L-gulono-Y-lactone oxidase was assessed in liver and kidney of 14 teleosts of 3 genera, histochemically (qualitatively) and biochemically (quantitatively). Activity of this enzyme was only detected in liver and kidney of common carp, Cyprinus carpio, and kidney of O. spilurus and O. aureus. No activity was detected in the species considered herein. The quantitative dietary ascorbic acid requirements of juvenile O. niloticus and O. mossambicus were determined by feeding diets containing graded levels of the vitamin (O~400mg/lOOg) and were based on growth response, food utilization, gross body composition data, tissue and biochemical changes and ability to prevent signs of ascorbic acid deficiency. The recommended level of supplementation of dietary ascorbic acid is l2Smg/lOOg and the net requirement 42mg/lOOg diet. Long-term ascorbic acid deprivation in £. niloticus and O. mossambicus resulted in poor performance in terms of growth, food utilization and survival. Other parameters evaluated included hepatosomatic index, liver and muscle glycogen content, blood parameters, tissue ascorbate concentrations, collagen contents, hydroxyproline and proline contents, and serum transaminase and cholesterol levels. Signs of ascorbic acid deficiency were severe and included haemorrhage~ opercular deformity, tail erosion, exophthalmia, cataract and spinal deformity (lordosis and scoliosis). Histologically scorbutic fish showed evidence of generalized bone changes associated with excessive production of chondrocytes and failur~ of ossification of growing bone areas. Eye lesions were associated with scleral collapse and also observed was hyperplasia of gill secondary lamellae epithelial cells and pronounced steatitis. Tissue ascorbate concentrations were correlated with dietary ascorbic acid levels and both species exhibited highest concentrations in the ovary, brain and testis, followed by heart, liver, gut, gills, eyes and the lowest levels in muscle and gall-bladder. The physiological role for ascorbic acid in each tissue is discussed. Eight week growth studies were conducted to evaluate the utilization of L-ascorbic acid (AA), the sodium salt of L-ascorbic acid (NaAA), glyceride coated L-ascorbic acid (GCAA), the barium salt of L-ascorbic acid 2-sulphate (AA2S) and ascorbyl palmitate CAP) in diets for O. niloticus and O. mossambicus, All five forms were added to the basal diet, containing no ascorbic acid CAAF), on an equimolar basis to supply 12Smg ascorbic acid/IOOg diet. All forms performed well in terms of growth, food utilization, and prevented signs of deficiency, Retention of ascorbic acid in diets after processing was increased by increasing dietary ascorbic acid level. AA2S and GCAA were more stable than AA and NaAA during processing and storage. The stability of AA, NaAA, GCAA and AA2S under different storage conditions was in descending order as follows: Freezer (_20°C), Fridge (S-BoC), room temperature in black bags (22-24°C) and room temperature in clear bags (22-24°C). Leaching of dietary ascorbic acid increased with increasing immersion time and water temperature. Stability and price of each form evaluated suggested that GCAA is to be preferred for use in fish feeds. The antioxidant effects of ascorbic acid were investigated. The results showed that ascorbic acid was not as effective as butylated hydroxy toluene (BHT) in preventing in vitro oxidation. An experiment was conducted to compare the performance of a commercial trout diet with the same diet supplemented to a level of l2Smg ascorbic acid/lOOg diet (Diet 2) when fed to O. niloticus. Fish fed the supplemented diet performed significantly better in terms of growth and food utilization concomittant with significantly increased tissue ascorbate concentrations. Sex differences in relation to dietary ascorbic acid nutrition were investigated. Females of both species exhibited significantly higher gonado~ and hepatosomatic indices than males. Females in both species eXhibited higher total ascorbate concentrations in gonad, gills, spleen, brain and blood than males whereas the reverse was true for the eyes. Dehydroascorbic acid (DHAA) levels were very low in tissues of both species. Ascorbic acid depleted O. niloticus fingerlings were fed on each of three diets providing nil, adequate Cl2Smg ascorbic acid/lOOg diet), and luxus (400mg/lOOg diet) of the vitamin after small surgical incisions had been made in dorsolateral musclature. Fish from each group were sampled regularly over 16 days and histological evaluation of the lesion area carried out as well as measurement of the tissue ascorbate levels. Epithelial elements of the healing process developed irrespective of the vitamin level but although fibroblast activity was marked in all three groups, collagenisation was very much slower in the deficient group, and in these the lesion was not mature, even at the termination of the experiment. The role of ascorbic acid in reproduction of tilapias was investigated in three experiments. The first showed that ascorbic acid supplementation of broodstock feed improved both hatchability and fry condition. In the second experiment fry produced from fish fed an unsupplemented diet and subsequently fed the same diet performed poorly in respect of growth and food utilization. Fry produced from broodstock fed the supplemented diet and subsequently fed the unsupplemented diet performed better than the previous group. This indicates transfer of ascorbic acid from the ovary to the eggs thence to the fry providing some protection against ascorbic acid deficiency during the early stages of life.