Thesis(M.S.)--Auburn University, 2005. / Abstract. Vita. Includes bibliographic references.

Thesis (M.S.)--West Virginia University, 2009. / Title from document title page. Document formatted into pages; contains xx, 195 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 125-126).

Thesis (M. Sc.)--University of Hong Kong, 2009. / Includes bibliographical references (p. 81-87).

Thesis (M.S.)--West Virginia University, 2006. / Title from document title page. Document formatted into pages; contains xii, 105 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 47).

Both field and laboratory experiments have shown lethal effects from the deposition of silt on incubating salmon eggs. Because silting appears to deprive the eggs of sufficient oxygen, theoretical limits of flow and oxygen content of sub-surface water were studied. Data have been gathered on temperature, oxygen content, and rate of flow of water twelve inches below the surface of the gravel at Nile creek. Field determinations of oxygen consumption of pink, chum and coho eggs have been made. In heavily-silted portions of the bed there was an insufficient supply of oxygen for pre-eyed chum salmon eggs. A field method for determining oxygen content and apparent velocity of gravel water is presented. / Science, Faculty of / Zoology, Department of / Graduate

Fish raceways of different cross-sectional shapes were compared in biological and hydraulic tests. Raceways of rectangular and circular cross-section were used. Two types of circular raceways were studied, one with a smooth wall, made of PVC, and one with a corrugated wall, made of galvanized steel that had been painted. The biological tests consisted of comparing the weight gain of rainbow trout (Salmo gairdneri) fingerlings (initial weight 6.0 g) held in the different raceways for 69 days. The fish in the painted corrugated steel raceway (final weight 25.6 g) grew more than those in the rectangular (final weight 22.9 g) and PVC (final weight 20.2 g) raceways (significant at α = 0.05). Very high stocking densities (130-139 kg/m³) achieved at the end of the experiment. Critical concentrations of dissolved oxygen or ammonia had not been reached at this point. Two types of hydraulic tests were done. One consisted of flow visualization studies in which a dye, malachite green, was introduced into the raceway and its movement observed and recorded photographically. In the second hydraulic test, the concentration of malachite green in the effluent was measured at various times after the introduction of the dye. These data were then used to obtain residence time distributions for the various raceways. No major differences were found between the hydraulic characteristics of the raceways tested. A biological test using unpainted galvanized corrugated steel raceways was also carried out. Rainbow trout fingerlings (3.6 g) were placed in galvanized raceways that had been flushed for 64 days. The fish were left in the raceways for 29 hours. During this time, 48% of the fish died. The survivors were transferred to fiberglass tanks where an additional 27% of the fish died over the next 50 hours (2 days). / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

No description available.

Thesis (Ph. D.)--University of Hong Kong, 1999. / Includes bibliographical references (leaves 343-362)and indexes.

The hypothesis was that salmon farming can be the basis for the establishment of a viable small business in British Columbia. The constraints on the establishment of a salmon farm imposed by government regulations, the availability of funds, and the market for pan-size salmon were presented and discussed. The pertinent biological knowledge associated with the rearing of captive salmon was summarized. A simple production model designed to produce approximately one-half million marketable, pan-size salmon within 15 months was derived from published accounts of studies at experimental fish farms. A hypothetical salmon farm was described in detail including estimates of the capital and operating costs associated with the farming and processing activities. The required information was obtained through interviews with knowledgeable members of the industry. The estimated revenues and expenses attributed to the hypothetical farm were analysed using pro forma financial statements to ascertain the financial position and the net cash flow which may be expected. The profitability of the farm was analysed by applying net present value and internal rate of return criteria to the net cash flow. Sensitivity analysis of the effect of changes to the product mix. market price, labour rate, feed price, tax rate, and stocking density upon the profitability of the farm was conducted. Estimates of the critical values of the above parameters which would allow the farm to be a feasible investment opportunity were derived. The conclusion is that pan-size salmon farming can be a feasible small business in British Columbia. / Business, Sauder School of / Graduate

Thesis (M.Sc. (Zoology)) -- University of Limpopo, 2020 / The pressing state of South Africa’s freshwater resources due to pollution from the release of raw sewage or poorly treated domestic wastewater, has resulted in the urgent need for the implementation of innovative ways to mitigate this problem. A proposed solution by the Council of Science and Industrial Research (CSIR) is to introduce different cultures of algae in wastewater treatment ponds where facilities have aged and become dilapidated. In turn fish are introduced into sewage maturation pond treated with algae to reduce algal biomass. The assumption being that if fish can survive under these conditions, the nutrients assimilated will be converted into fish biomass when ingested, in an attempt to decrease aquas nutrient loads. The aim of the study was to assess the health and survival of Oreochromis mossambicus exposed to wastewater from the Motetema wastewater treatment plant (WWTP) and to establish the extent to which this species consumes micro-algae within the water column. The aim was accomplished by assessing the consumption of algae by O. mossambicus based on algal cell density counts in fish aquaria and to establish the feeding ratio of fish based on stomach content fullness as well as to monitor the survival rate of O. mossambicus exposed to various concentrations of sewage water over a 96-hour period. To establish fish survival under wastewater conditions, a 96-hour experiment was conducted in glass tanks (60 L), whereby the health and mortality of O. mossambicus exposed to different concentrations of domestic wastewater from Motetema WWTP was investigated. One set of aquariums supplied with compressed air via the use of diffusers while the other set of aquariums were void of aeration so as to simulate conditions at the treatment plant. Treatments comprising of four concentrations of 25, 50, 75 and 100% wastewater and a control of 0% were used. Water quality parameters were monitored every four hours and mortalities were recorded. Water samples were collected twice a day and sent to Capricorn Veterinary laboratory for nutrient analysis. Gill samples were also collected and sent to Onderstepoort Veterinary Institute for histological sections analysis. To assess the consumption of algae, 18 tanks (60 L) were set up in the laboratory, whereby three aquariums served as a control void of algae with the remaining tanks dosed with two algal species (Chlorella vulgaris and Chlorella protothecoides) of concentrations of 33%, 66% and 100%, over a period of ten days. Counts of algal density before and during the course of the experiments were done using a handheld flourometer. Upon mortalities and on the fifth day, fish were randomly selected from fish tanks, euthanised and stomach contents analysed. The stomach of fish was rated based on the percentage fullness and categorised as being empty, ¼ full, ½ full, ¾ full, full or gorged. When mortalities occurred, fish were dissected and their stomach contents analysed for fullness. Upon completion of the trial, two fish per treatment were euthanised and their stomach contents evaluated for algal consumption. Fish remaining at the end of the fish trial were counted and weighed to calculate the weight gain and specific growth rate. Survival rates were also determined. Water quality parameters were monitored three times a day over the duration of the trial. Water samples were collected every second day and send to Capricorn Veterinary laboratory for nutrient analysis. All mortalities were recorded over the duration of the trial period. In exposure and survival trials, physico-chemical parameters of water from the experimental tanks were within the acceptable limit for the growth and survival of O. mossambicus, except for dissolved oxygen and ammonia concentrations. Ammonia levels and mortality rates were significantly higher (p< 0.05) in treatments with wastewater, with ammonia levels exceeding those considered toxic for O. mossambicus. High ammonia concentrations resulted in definite histopathological changes in the gills as well as fish mortalities. After exposure to wastewater moderate signs of aneurism of the gill lamella, mild epithelial lifting, focal hyperplasia and clubbing of the terminal end of the secondary lamellae were recorded. Lesions are explained as a defence mechanism where gills increase the distance between the external environment and the blood, thus serving as a barrier to the entrance of the contaminants. Furthermore, results indicated that effluent levels >25% were detrimental to the fish. Fish survival decreased when exposed to effluent water, with higher number of mortalities recorded in tanks with no aeration. A 100% survival was observed in tanks with 25% treated wastewater in both aerated and non-aerated aquariums. The presence of fish mortalities in treatments >25 domestic wastewater shows that conditions at Motetema WWTP will be unfavourable for fish. Thus, results from the study indicate that domestic wastewater would need to be diluted to less concentrated levels to ensure the survival of fish and mechanical aerators needs to be deployed to increase oxygen levels in treatment ponds. Water quality parameters for the second set of experiments fell within the recommended range for the growth and survival of fish. However, low oxygen levels were recorded from the control group with minimum values of 1.8 mg/l and maximum concentrations of 3.6 mg/l. Furthermore, temperature and pH ranges recorded during this study fell within the desired range for growth and reproduction of Chlorella vulgaris and Chlorella protothecoides. Nutrient concentration (phosphates, sulphates and nitrate) for this study were low, however ammonia and nitrite were above the acceptable level for fish growth and survival. The presence of fish resulted in increased levels of ammonia. High ammonia levels were not mitigated by algae in the tanks. However, the high ammonia levels decreased with the increasing number of fish mortalities. There were slight decreases in chlorophyll-a concentrations over the study period, from tanks comprising of algae and, tanks comprising of algae and fish. Decreases in chlorophyll-a concentrations in tanks with fish were linked to consumption of algae by the fish. This was verified by the presence of algae in the stomach of fish euthanised during and at the end of the experiment. In tanks without fish, decreases in chlorophyll-a concentrations could be attributed to plankton die offs, as aquariums had algae that had settled at the bottom of the tanks. Although, consumption of algae by fish was observed in this study, no full stomachs were recorded over the experiment period. Tanks with 66% algal concentrations had low survival rates. Better survival was observed from treatments with 33% algal concentrations. Toxic secretions could have attributed to the high mortality rate or low survival rates during the study period in tanks with 66% and 100% algal concentrations. In addition to this, ammonia and nitrite values that were above tolerable limits for fish could have also contributed to the high mortality rates (>80%). The use of fish in the tanks as a means to assimilate the algae, seemed to have an opposite effect than the desired one. As the presence of fish in tanks increased ammonia levels, therefore, the effluent would need to be further treated before it can be re-used or released into the environment. Further experiments would need to be conducted to establish whether negative influences could be neutralised, when other species such as Scenedesmus spp. are used together with Chlorella spp. for the treatment of wastewater, in order to make the environment suitable for fish survival. / DSI-NRF SARChI Chair (Ecosystem Health), Flemish Interuniversity Council (VLIR-OUS)