The macroinvertebrates of the Cunene River from the Ruacana Falls to the river mouth and assessment of the conservation status of the river

The proposed construction of a second hydroelectric power-generating dam on the Cunene (Kunene) River on the Namibia-Angola border, more than 100km downstream of the Ruacana hydroelectric power plant, will have a major influence on the aquatic biota of this river. In order to assess the potential impact of this impoundment a more detailed inventory of the biota in the river prior to this development was needed. Unfortunately the river presently does not represent an entirely undisturbed system as the operation of the Ruacana hydroelectric power station since 1970 has had a long-term effect on its biota. In the low-flow mid-summer season in particular, large areas of the river become irregularly inundated and exposed, sometimes on a daily basis, making them unsuitable for macroinvertebrate colonisation. There are six impoundments along the Cunene River upstream of the Ruacana Falls in Angola. These, however, do not have any major disruptive effects on daily flow variation in the Cunene River in Namibia although whole system biological consequences could be considerable but are unstudied. The Cunene River has a diverse freshwater fish fauna but, prior to the surveys reported here, the aquatic macroinvertebrates had been poorly studied. Surveys conducted by staff of the Department of Water Affairs (DWA) of Namibia and the Albany Museum, Grahamstown, in 1997 and 1998 have resulted in 216 aquatic macroinvertebrate species being recorded from Ruacana to the river mouth. The lower Cunene River, flowing through a very arid region, is biogeographically isolated and therefore highly vulnerable to change. The biota recorded reflects a fauna of widespread species and several elements of tropical origin. Several undescribed species may reflect some endemics but because of limited knowledge of the tropical rivers, this cannot be ascertained with certainty. From the aspect of conservation, the river contains a diversity of species with an abundance of filter-feeding species. Further surveys conducted during different seasons will undoubtedly record more taxa.     

The application of the Zero Emissions Research and Initiatives (ZERI) concept in an integrated industry-polyculture-farm system in Namibia: The case of Tunweni Sorghum Brewery

One major area dealt with by the concept of Zero Emissions Research and Initiatives (ZERI) is the utilisation of huge volumes of nutrient-rich waters from household toilets, kitchen sinks and municipal and organo-industries for integrated purposes. The arrangements at the Tunweni Sorghum Brewery, Tsumeb, Namibia are such that wastewater is utilised in the polyculture of locally available riverine fish species in large (3 000m²; 120m long × 25m wide), deep (3m) earthen ponds. Before reaching the fishponds the wastewater passes through a series of bio-system processes such as mushroom and earthworm beds, a pig sty, anaerobic and aerobic digesters and algae ponds. A pH of about 8.0 is desirable for maximum fish production in the large (9 000m³) fishponds. The old Chinese technique is followed whereby wastewater is utilised for growing fish without adding any feed supplement; various plankton and invertebrates produced naturally serve as feeds for various kinds of fish feeding at different trophic levels. A variety of locally-available riverine fish species, of different trophic levels, are useful for sustainable stocking in the ponds where no feed-supplement is necessary. Various plankton and invertebrates are produced naturally as feeds for the various kinds of fish feeding at different trophic levels, obviating the purchase of costly artificial feeds which can make fish culture uneconomical. Fish wastes are naturally mineralised into nutrients in the ponds and the nutrient-rich water supports phytoplankton, zooplankton and invertebrates, all of which comprise a varied food chain supporting the fish growth.     

Indigenous names of fish and fishing gear in the Cuvelai,Kavango and Caprivi regions of Namibia

This study discusses the local names of the inland fresh water fish species of the Cuvelai, Kavango and Caprivi regions of Namibia, in five indigenous languages: OshiWambo/OshiNdonga, RuKwangali, RuGciriku, SiLosi and SiSubia. It also discusses local names of the indigenous types of fishing gear currently used in the inland water fishing practices in those regions. In the Cuvelai systems 24 fish species have OshiWambo/OshiNdonga names, in the Kavango systems 60 have RuKwangali and RuGciriku names and in the Caprivi systems 68 have SiLosi and SiSubia names. Twenty types of fishing gear are recorded to have indigenous names in the Cuvelai, 25 in Kavango and 22 in Caprivi. Fifteen commonly available indigenous types of gear are exclusively used by women, who therefore play a crucial role in the exploitation and conservation of freshwater fish in Namibia.     

The Namibian Scoring System (NASS) version 2 rapid bio-assessment method for rivers

This paper presents a rapid bio-assessment method for assessing the ecological condition of streams and rivers in Namibia. The method uses the composition and abundance of aquatic invertebrates, which are identified in the field, mostly to family level. The method is based on the South African Scoring System version 5 (SASS5), which has been modified to account for additional tropical invertebrate taxa that occur in northern Namibia. The method was applied to the Zambezi River near Katima Mulilo and NASS results were found to fluctuate predictably with changes in water level. Training of Namibian personnel to apply the method, as part of the National Water Quality Monitoring Programme, is recommended.