Waste vegetable leaves as feeds for juvenile Oreochromis shiranus and Tilapia rendalli in mono-and polyculture.

Mixed sexes of Oreochromis shiranus and Tilapia rendalli were stocked in 5-m super(3) concrete tanks in the ratios of 0:100, 25:75, 100:0 and 75:25, at the rate of 6 fish m super(-2). O shiranus and T. rendalli were stocked at mean body weights ( not equal to SD) of 12 not equal to 0.4 g and 12 not equal to 0.7 g, respectively. Cabbage and pumpkin leaves were added to the tanks at a rate chosen to simulate pond conditions (50 kg dry matter (DM) ha super(-1) day super(-1)) as bundles tied with wire, fully submerged at a depth of about 30 cm.

Floods, floodplains and fish production in the Mekong basin: present and past trends

This paper deals with relationships between hydrology, wetlands and fisheries production in the Mekong River Basin. A five-year monitoring of the bag net ("dai") fishery in the Tonle Sap River (Cambodia) showed a strong correlation between catches and water level in the same year. One taxon making up to 37% of total catches explains most of the relationships between catches and water level. The current overall catch in the Tonle Sap system amounts 230,000 tons a year. When compared with historical surveys, this catch is twice as much as the catch 60 years ago.

Comparative analysis of the environmental costs of fish farming and crop production in arid areas

Using published data, 20 crop and 19 fish production systems were compared for efficiency of water and nutrient (nitrogen) use. In agriculture, rain-fed cassava was most efficient, followed by rain-fed beans, pivot-irrigated maize and rain-fed wheat. Intensive vegetable production uses water most efficiently to produce edible dry matter. Maize, wheat and crop legumes are most efficient at producing protein. Cassava produces energy most efficiently. For aquaculture, sharp-tooth catfish in fed raceway-ponds are most efficient, followed by tilapia in fed cages and tilapia in sewage-fed ponds.

Mapping of aquatic resource systems with areas of potential aquaculture in Ghana.

Aquatic resource systems with potential for aquaculture development in Ghana were demarcated: lagoons, bays and estuaries; rivers; lakes and large reservoirs; small water bodies; floodplains and swamps. Where available, areaestimates are given, together with data on existing aquaculture and fisheries activities. Potential technologies for further development are briefly pointed out.

Influence of fertilizers' types and stocking density on water quality and growth performance on Nile tilapia African catfish in polyculture system

The effects of fertilizer types and stocking density were investigated on water quality parameters that expected to affect growth performance of the polyculture of Nile tilapia <i> (Oreochromis niloticus) </i>, African catfish <i> (Claris gariepinus) </i> and sliver carp <i>(hypophthalmichthys molitrix)</i>. The purpose of this study was to determine the best type of fertilizer to use and stocking density to apply which maximizing fish yields while minimizing expenses and environmental degradation.

Water management and wise use of wetlands: enhancing productivity

Lakes and reservoirs are affected by human interventions mainly by eutrophication. Changes in morphology are less common, although siltation and local alterations to the riparian zone can result from urbanisation,marina construction and deforestation. In lakes and particularly reservoirs used for water supply and power generation, rapid drawdown can occur that damages riparian vegetation and fish populations.

Fisheries and water productivity in tropical river basins: Enhancing food security and livelihoods by managing water for fish.

Faced with growing pressure upon freshwater resources, increased water productivity in agriculture is essential. Efforts to do so however need to consider the wider role of water in sustaining food production. This paper considers the importance of water management in sustaining fish production in tropical river basins, and the potential for enhancing food production and income to farmers by integrating fish production into some farming systems. Specific examples from selected river systems and irrigated farming systems in Africa and Asia are provided.

River fisheries in Africa: their relationship to flow regimes

River fisheries in Africa are important because of their contribution of animal protein to human diets. Such fisheries are highly dependent on hydrological regimes and show considerable year-to-year variation in response to natural climatic events. River flow regimes are being increasingly altered by withdrawals by man, principally for agriculture. The modification of hydrological regimes is leading to diminishing catches of fish and changes in the number and size of the species caught.

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