Madoqua - Volume 17, Issue 2, 1991
Volumes & issues
Volume 17, Issue 2, 1991
Source: Madoqua 17, pp 54 –60 (1991)More Less
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Author C.M. BreenSource: Madoqua 17, pp 61 –65 (1991)More Less
A brief overview of wetland definition, functions and values and classification is presented. I conclude that wetlandsof arid regions, even where the interval between flooding may be several years, can be accommodated within existing classification system. A preliminary analysis of the return frequency of extreme rainfall events indicates that temporary waterbodies in Namibia may provide adequate for wetland processes such as breeding of waterfowl once in every five to ten years. I suggest that because of regional variations in rainfall and the wide distribution of these wetlands, suitable habitats are likely to be available for nomadic species at considerably shorter intervals.
Source: Madoqua 17, pp 67 –76 (1991)More Less
The largest natural permanent surface waters in Namibia occur in the wetlands of East Caprivi and are fed by two of Namibia's five perennial rivers. The wetlands are divided into five geographically distinct zones with a total surface area of abut 5 000km. Two of the areas (Lake Liambezi and the eastern floodplain) are only intermittently inundated when the Zambezi River is in flood, while the Kwando River, the Linyanti Swamp and the Chobe Marsh are permanent. In wet years, the five systems form acontinuous water body.
Author S. BethuneSource: Madoqua 17, pp 77 –112 (1991)More Less
In Namibia, the Kavango River and its associated floodplains are seasonally flooded, low gradient, riverine wetlands. These support a productive and diverse biota including several endangered and protected species and are essential to the economy of a large rural population.
Source: Madoqua 17, pp 113 –122 (1991)More Less
Nine traditional and four modern types of fishing techniques were used for subsistence fishing along the Kavango River each with a different species selectivity. The most commonly used fish funnel collected around 200 g of fish per h, comprising small fish species or 71% of the species recorded for the Kavango River
Source: Madoqua 17, pp 125 –128 (1991)More Less
The Cunene River with a total length of approximately 890 km, rises in the vicinity of Nova Lisboa in Angola. From the Ruacana Falls the Cunene River flows westwards for 340 km before it enters the Atlantic Ocean and forms the international boundary between Namibia and Angola. Floodplain wetlands occur between Matunto and Calueque in Angola.
Source: Madoqua 17, pp 129 –133 (1991)More Less
Wetlands in Etosha National Park and Owambo are the result of a complex endorheic drainage system and shallow basin topography. The CuveIai drainage system which is fed by relatively high annual rainfall of the central Angolan highlands, extends into northern Namibia via a maze of shallow vegetated waterways and a few major channels which eventually drain into a primary impoundment (lake Oponono) and a series of salt pans in Etosha N.P.The duration of wetland conditians is erratic and largely due to rainfall in the upper reaches of the system.
Author R. LoutitSource: Madoqua 17, pp 135 –140 (1991)More Less
One of Africa's most arid regions, the Namib desert is crossed by several west flowing rivers, ten of which flow formore than a few days orweeks at the most. The four largest rivers, the Kuiseb, Swakop/Khan, Omaruru and Ugab provide water for human populations as well as wildlife and some show unexplained decreases in flow frequency or amplitude.
Author John IrishSource: Madoqua 17, pp 141 –146 (1991)More Less
Aquatic habitats of karst origin in Namibia are generally small in area and few in number. Despite this, the fact that they include unusual habitat types like hypogean cave lakes, cenotes and flowing epigean springs which are rare elsewhere in the country, lend them high conservation priority. Almost all important karst areas in southwestern Africa, and a major part of those in southern Africa, faIl within the borders of Namibia.
Source: Madoqua 17, pp 147 –153 (1991)More Less
There are 14 areas of sheltered shallow saline waters along the Namib coast between, and inclusive of the mouths of the Orange and Cunene Rivers. We descriptionbe the coastal wetlands, review available biological data on the wetlands and comment on their present conservation satus and predictable future changes which may affect them.
Source: Madoqua 17, pp 155 –157 (1991)More Less
The total catchment area of the Orange River is approximately 852 000 km2 (47% of the totaI surface area of South Africa) and is the largest regulated river system in South Africa. Due to man's interference with this river system, remarkable changes in its ecology have taken place.
Author J.A. HoltzhausenSource: Madoqua 17, pp 189 –191 (1991)More Less
The number of freshwater fish species present in all known locales in Namibia are given with the proportion of species associated with each wetland. Approximately 75% of all riverine species are associated with floodplains, of which only three endemics and six Red Data species are floodplains species.
Source: Madoqua 17, pp 201 –209 (1991)More Less
The southern end of the endorheic Cuvelai drainage consists of a 130km wide delta that receives floodwater and migrating fish from thebetter watered catchment in southern Angola. The fish life of these temporary oshanas is dominated by the genera Barbus, Clarias and Oreochromis, similar to sumplakes or other systems in central and southern Africa.
Author C.J. HaySource: Madoqua 17, pp 211 –215 (1991)More Less
Growth of the Mozambique tilapia Oreochrornis mossambicus on natural food in floating cages, Hardap Dam, NamibiaSource: Madoqua 17, pp 217 –220 (1991)More Less
The growth of unfed Oreochromis in cages is slow when compared with results obtained from those fed with suppIementary feeds. The length/weight relationship, growth and relative condition of the unfed fish compared favourably with the natural tilapia population in Hardap Dam. The production caged unred fish has potential as a cheap source of protein.
Author A.** Griffen, M.* & ChanningSource: Madoqua 17, pp 221 –225 (1991)More Less
Namibia posseses a varied amphibian fauna and being primarily an arid and semi-arid region. 88% of this fauna is independent of permanent wetland. The few species that do depend on permanent wetland habitats (8) are species with marginal distributions in Namibia. The primary interest these species is that they are highly vulnerable due to their sensitive habitat and can thus be act as environmental indicators. Relatively few Namibian reptiles (8) are dependent on permanent wetlands and fewer still are associated with ephemeral ones.