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Gewählte Diplomarbeit / Masterarbeit:

Diplomarbeit / Masterarbeit - Institut für Hydrobiologie, Gewässermanagement (IHG), BOKU-Universität für Bodenkultur, pp 65. UB BOKU obvsg

Datenquelle: ZID Abstracts
Aquaculture, the fastest growing sector of food production, is increasing rapidly in Kenya. Recirculating aquaculture systems (RAS) are intensive cultivation technologies recently introduced to Africa that try to address environmental concerns, including high water consumption and nutrient pollution. To assess the production of fish and nitrogenous wastes, an 8-week study was conducted on Kenya’s first large commercial RAS, where effluent water is used to irrigate and fertilize an integrated horticulture. Two size-classes of adult Nile tilapia were stocked at different periods and fed according to two feed lines. Water of the six 52m³ culture tanks, their filtration units and water from flushing was analysed for NH4, NO2, NO3, and total N concentrations. Fish biomass was assessed biweekly and nitrogen concentrations in flesh, feed, faeces and water were integrated into a nitrogen balance in form of a simulation model. Additionally, tomato plants in hydroculture were irrigated with two different dilutions of tank water to gain insight into its value as fertilizer. Nutrients were analysed weekly following APHA (1995) standard procedures. Feed conversion ratio and N-waste generation increased with the absolute amount of feed and a daily ration of 1.2% was found to be optimal for an economical production. Beside an initial nitrite peak of 93 mgNO2-NL-1, NO2-N, NH4-N, and NO3-N concentrations were always below toxic limits to tilapia. Bioavailable nitrate represented a considerable proportion of nitrogen in the RAS with concentrations up to 235 mgNO3-N L-1. Modelled values were sufficiently accurate for fish growth, faecal N and NH4-N but overestimated NO3-N concentrations. A simulated scenario of additionally 2 kg fodder in the feed lines proposed a decreased profitability. Even though the model has still limited applicability, it can contribute to a better management of (integrated) RAS–thus, for a sustainable and profitable aquaculture development in East Africa.

Beurteilende(r): Hein Thomas
1.Mitwirkender: Waidbacher Herwig

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