Status and impact of rural aquaculture practice on Lake Victoria basin wetlands

Rural aquaculture in Lake Victoria basin is a fast increasing nontraditional farming activity which if not appropriately practised will lead to degradation of the wetlands. As part of a study to develop appropriate guidelines and model systems for wetlands‐based rural aquaculture in the basin a survey was conducted to assess the status and the ecological and socioeconomic impact of rural aquaculture on wetlands and wetlands communities. Aquaculture practice was found to be common but not as a major activity. Aquaculture in the wetlands can be described as a low input‐low output production activity and subsistence based on ponds under 400 m² using free seed from public agencies with hardly any supplementary feeding. Men owned most of the ponds and women only contributed to the management of the fishponds by feeding the fish. Poorly constructed ponds and loss during harvesting have led to the escape of cultured species into the wild. Introduction of nonnative species in the basin has already led to wide ranging ecological, environmental and socioeconomic changes whose impact and usefulness are still very much contentious. Repeat of such scenarios can be avoided if appropriate and science‐based models for rural aquaculture farming are developed, tested and disseminated to the communities.     

Some considerations on the functioning of tropical riparian ecotones

The fundamental function of a riparian wetland is the prevention against eutrophication and various types of pollution of a water body. This is done through the typical and dominant vegetation of the African tropical ecotone wetland, the papyrus which is very productive and has considerable adsorbing root surfaces as it spreads out over the water and at the river and lake edges. Because of the twelve-hour light day and high temperatures, the production is high. In this way, nutrients (nitrogen, phosphorus and others) are concentrated and accumulated in different parts of the plant from water flowing through the ecotone wetland. The amounts of, and the rate of flow of the material substances are regulated and the interface zone acts as a sink to most of those anthropogenic substances. It also functions as a refuge for waterfowl and other wildlife, and contributes to human food needs and well-being.     

Tropical freshwater ecotones: their formation,functions and use

Tropical water-terrestrial ecotones play important roles in regulating the flow of materials from and to land and water ecosystems. Ecotones exist where active interactions between two or more adjacent ecosystems occur with the appearance of processes that do not exist in either of the adjacent ecosystems.They occur naturally depending on the hydrological and geomorphological structure of the location. External and internal processes can influence the origin and persistence of ecotones. Ecotones regulate the landscape mosaic, affect energy flow between adjacent systems and intervene in landscape connectivity.The literature on geological and climatic origins of wetlands and open waters, internal influences on their creation and destruction and, finally, their use by society is reviewed.     

Copper Ion Distribution in the surface waters of Lake George and Idd Amin

Copper ion distribution in the surface of Lakes George and Idd Amin (formerly L. Edward) has been determined using atomic absorption spectrophotometry and solution spectrophotometry. Some other chemolimnological paramerts (some of which affect copper ion distribution) have also been determined. The copper ion ranges from 0.07 to 0.13 ppm in L. George and from 0.00 to 0.02 ppm in L. Idd Amin.     

Likely effects of salinity on acute copper toxicity to the fisheries of the lake George-Edward basin

Alkaline, saline waters are common in the Western Rift Valley of East Africa, in which the lake George-Edward basin is situated. A growing copper mining industry in the area makes it important to understand the limnology of the lakes in this basin before copper pollution occurs. The fish could possibly suffer from acute (or chronic) toxicity if copper levels increase.Abiotic factors within the alkaline, saline waters of this basin reduce the acute toxic effects of copper to fish. The most important factor is salinity, which is a measure of the total dissolved mineral salts. The relatively highly concentrations of mineral salts of these waters will to reduce the effective copper ionic activity through adsorption, precipitation, and ionic interference. The high concentrations of organic compounds in the waters, also complex and chelate the ionic Cu²⁺, thus reducing further its effective concentration. This will therefore act as a check on the copper toxicity to the fish of the lake basin.