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Life-history and stock assessment of Clarias Gariepinus in the Okavango Delta, BotswanaBokhutlo, Thethela January 2012 (has links)
Large catfishes (Clarias gariepinus & Clarias ngamensis) are not exploited commercially in the Okavango Delta, Botswana. They however constitute a large proportion of the gill net fishery catch (23 %) albeit as by-catch, coming second after cichlids (70 %). Monthly experimetal gill net sampling over 8 years showed that C. gariepinus was the most abundant species in the Okavango Delta by mass making up 37 % of the catch composition by fresh weight. Despite the relatively high abundance of C. gariepinus in the Okavango Delta, its status has never been fully assessed. For this reason, this study aimed to assess the status of C. gariepinus in the Okavango Delta with the particular goal to determine if the species could support a directed commercial gill net fishery. Investigation of the effects of the flood pulse on abundance of C. gariepinus showed that variability in water levels was the major driver of population abundance for this species. Three biological variables: (1) catch per unit effort (CPUE); (2) % catch composition and (3) Shannon's diversity index (H') exhibited a negative and significant relationship with the flood index within a year. The variation in these variables was statistically significant between months. There was a weak positive relationship between water levels and the biological variables between years suggesting increase in productivity of the system at high water levels without a lag period. Age and growth were determined using sectioned otoliths. Edge analysis showed that growth zone deposition occurred during the drawdown period in summer when water temperature and day length were increasing. The maximum recorded age was 15 years. Growth of this species was best described by the linear models (y = 21.50x + 427.39 mm LT; r² = 0.35) for females and (y = 23.79x + 440.83 mm LT; r² = 0.38) for males. The von Bertalanffy growth model described growth as Lt = 10000(1- exp(-0.002(t + 18.07))) mm LT for combined sexes Lt = 10000(1- exp( -0.002(t + 18.50))) mm LT , for females and Lt =908(1-exp(-0.076(t+7.95)))mmLT for males. Age at 50 % maturity was attained in the first year of life. Spawning occurred throughout the year with an apparent peak between November and April. The mean total annual mortality rate (Z) was 0.25 per year. The mean annual natural mortality rate (M) was 0.20 per year and fishing mortality (F) was calculated at 0.05 per year. The life history strategy of C. gariepinus was in between the periodic and opportunistic strategies. Therefore management of this species should be aimed at maintaining a healthy adult population and age structure. Since a large portion of the Okavango Delta is already protected and most other parts are also inaccessible to fishers there are enough spatial refugia for the species and the status quo should be maintained. Under this scenario, there is no need for regulation of the current mesh sizes because the species is harvested after maturity and replenishment of exploited populations will always occur from other parts of the system. Per recruit analyses indicate that the current fishing mortality maintains spawner biomass at levels greater than 90 % of pristine levels. Therefore a commercial fishery may be established using mesh 93 mm to maximize yield with a rotational harvesting strategy. Close monitoring is essential to ensure that re-colonization of overexploited habitats does indeed occur. Recreational angling and commercial gill net fishing need to be separated on a spatial and temporal scale during the feeding run to minimize potential conflicts.
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The ecology of Meyer's parrot (Poicephalus meyeri) in the Okavango Delta, Botswana.Boyes, Rutledge Stephen. January 2008 (has links)
Meyer’s Parrot Poicephalus meyeri is the smallest of the nine Poicephalus
parrots, forming the P. meyeri superspecies complex with five congeners. Their distributional
range far exceeds any other African parrot, extending throughout subtropical Africa. Meyer’s
Parrots had previously not been studied in the wild, and therefore, gathering high-quality
empirical data on their behavioural ecology became a research and conservation priority. The
primary aim of the study was to correlate environmental (e.g. rainfall, habitat availability,
resource characteristics, food resource abundance and temperature) and social (e.g. inter- and
intra-specific competition, predation, and human disturbance) variables with aspects of their
ecology (e.g. flight activity, food item preferences, breeding activity, and group dynamics) to
evaluate the degree of specialization in resource use (e.g. trophic, nesting and habitat niche
metrics).
African deforestation rates are the highest in the world, resulting in twelve out of the
eighteen Meyer’s Parrot range states undergoing drastic loss of forest cover over the last 25
years. Most commentary on the population status of Meyer’s Parrots and other Poicephalus
parrots pre-dates this period of rapid deforestation In addition, over 75 000 wild-caught
Meyer’s Parrots and almost 1 million wild-caught Poicephalus parrots have been recorded in
international trade since 1975. Empirical data from this study was used to identify ecological
weaknesses (e.g. niche specialization or low breeding turnover) for evaluation within the
context of deforestation in the African subtropics. Baseline data on the breeding biology and
nest cavity requirements of Meyer’s Parrots was also necessary to assess the viability of
applying the conservative sustained-harvest model to African parrots. A unifying goal of this
study was to advance our knowledge of the ecology of African parrots and other
Psittaciformes by assessing the validity of current hypotheses put forward in the literature.
The Meyer’s Parrot Project was initiated in January 2004 on Vundumtiki Island in the
north-eastern part of the Okavango Delta, Botswana. Due to high flood waters between
March and July 2004, road transects were postponed till August 2004. Transects were
conducted at Vundumtiki from August 2004 to July 2005 and February 2007 to August 2007,
and at Mombo from August 2005 to January 2006. During 480 road transects over 24
months, food item preferences closely tracked fruiting and flowering phenology, resulting in
significant positive correlations between Levins’ niche breadth, rainfall and food resource
availability. Meyer’s Parrot can, therefore, be considered opportunistic generalists predispersal
seed predator that tracks resource availability across a wide suite of potential food
items, including 71 different food items from 37 tree species in 16 families. Meyer’s Parrots
were, however, found to be habitat specialists preferring established galleries of riverine forest
and associated Acacia-Combretum marginal woodland. These strong habitat associations
facilitate their wide distribution throughout the Kavango Basin, Linyanti Swamps, down the Zambezi valley, up along the Rift Valley system in associations with the great lakes, through
the Upper Nile and the Sudd, and west as far as Lake Chad through the Sahel.
Seventy-five nest cavities were measured during this study, including 28 nest cavities
utilized by Meyer’s Parrots within the 430ha sample area at Vundumtiki. Over 1700 hours of
intensive nest observations at six nest cavities was undertaken. Meyer’s Parrots formed
socially monogamous pair-bonds maintained over at least four breeding seasons. Breeding
pairs established breeding territories up to an estimated 160ha within which there were 1–6
nest cavities. Eggs hatched asynchronously, yet nestlings fledged synchronously with similar
body size and condition. There was evidence to support the incidence of extra-pair
copulations, however, mitochondrial DNA sequence data are required to confirm the
incidence of extra-pair fertilizations. Meyer’s Parrots had no preferences in regard to nest tree
species beyond the incidence of suitable nest cavities, which are selected and further
excavated to accommodate their non-random nest cavity preferences. There was a significant
non-nesting Meyer’s Parrot population during the breeding season, likely due to this longlived
cavity-nester delaying nesting until a suitable breeding territory becomes available.
Meyer’s Parrots utilize communal roosts during summer and disperse from them
according to the Foraging Dispersal Hypothesis. Due to the requirement to roost during the
middle of the day to avoid heat stress, Meyer’s Parrots have bimodal flight and feeding
activity patterns. The highest probability of locating Meyer’s Parrots is between 08h30 and
11h00 during summer when both adults are feeding on the seeds of fleshy-fruits in riverine
forest communities.
Due to the paucity of data on the current distribution and population status of Meyer’s
Parrots and other African parrots, a continent-wide survey of all African parrots represents a
conservation priority. Current deforestation rates in several Meyer’s Parrot range, their
specialist habitat associations, and lack of evidence to support adaptability to a changing
landscape mosaic necessitate the re-classification of Meyer’s Parrots as data deficient or nearthreatened.
Based on low breeding population due to limited breeding opportunities, the
CITES Appendix II wild-caught bird trade should also be halted until the sustainability of this
trade has been evaluated and the relevant information made available. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2008.
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Assessment of organochlorine pesticide residues in fish samples from the Okavango Delta, BotswanaMpofu, Christopher 28 February 2011 (has links)
This thesis presents an evaluation of the dispersive solid-phase extraction (d-SPE) method referred to as the quick, easy, cheap, effective, rugged and safe (QuEChERS) method for the determination of four organochlorine pesticide residues in fish samples. The pesticides investigated in this study were o, p′-DDT, p, p′-DDE, aldrin and dieldrin. The combined use of Gas Chromatography with an Electron Capture Detector (GC-ECD) and sensitive Time of Flight (TOF) mass detector facilitated the identification of the target analytes. In the absence of certified reference material, the overall analytical procedure was validated by systematic recovery experiments on spiked samples at three levels of 2, 5 and 10 ng/g. The targeted compounds were successfully extracted and their recovery ranged from 76 to 96% with relative standard deviations of less than 13%. The optimum QuEChERS conditions were 2g of fish powder, 10 ml acetonitrile and 1 min shaking time. The optimal conditions were applied to assess the levels of chlorinated pesticides in blunt-tooth catfish (Clarias ngamensis), tigerfish (Hydrocynus vittatus), Oreochromis andersonii and red-breasted tilapia (Tilapia rendalli) from the Okavango Delta, Botswana. Dieldrin, p, p′-DDE and aldrin were detected in all the analysed samples with a concentration range of 0.04 – 0.29, 0.07 – 0.33, 0.04 – 0.28 and 0.03 – 0.24 ng/g per dry weight in O. andersonii, C. ngamensis, T. rendalli and H. vittatus respectively. These concentrations were below the US-EPA 0.1 μg/g allowable limit in edible fish and the Australian Maximum Residue Limit (MRL) of 50 - 1000 ng/g in fresh fish. DDT was not detected in all the fish species investigated. The mean lipid content recorded in the fish samples were 1.24, 2.16, 2.18 and 4.21% for H. vittatus, T. rendalli, O. andersonni and C. ngamensis respectively. No systematic trend was observed between fish age and pesticide levels in fish. Acetylcholinesterase (AChE) activity assays were performed to assess the effects of organochlorine pesticides in Clarias ngamensis. The enzyme activity recorded in Clarias ngamensis from the Okavango Delta and the reference site was 12.31 μmol of acetylcholine iodide hydrolysed/min/g brain tissue. The enzyme activity remained the same indicating no enzyme inhibition. The conclusions drawn from this study are that the QuEChERS method is applicable for the determination of organochlorine pesticide residues in fish matrices. The fish from the Okavango Delta are safe for human consumption.
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The value of the Okavango delta a natural resource accounting approach /Mmopelwa, Gagoitseope. January 2006 (has links)
Thesis (Ph.D.(Agricultural Economics))--University of Pretoria, 2006. / Includes summary. Includes bibliographical references. Available on the Internet via the World Wide Web.
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The ecology and management of the fishes of the Okavango Delta, Botswana, with particular reference to the role of the seasonal floodsMerron, Glen Steven January 1991 (has links)
The Okavango is a vast inland delta system in northern Botswana which receives an annual flood from the highlands of southern Angola. There are distinct communities of fish in the Okavango which can be separated from each other by the physical characteristics of the different habitat types with which they co-evolved. This thesis provides an account of the biology and ecology of selected fish species in the Okavango Delta. Their response to the annual flood regime, and the environmental factors which limit their distribution and abundance, are examined. The thesis emphasizes the importance of water fluctuations in determining the nature of the fish fauna and the reaction of the fishes in terms of community structure, movements, breeding, predator-prey interactions and feeding. Four major ecotones were studied in the Okavango Delta. In the riverine floodplain and perennial swamp ecotones a higher species diversity was recorded than in the seasonal swamp and drainage rivers ecotones where diversity was lowest and comprised mainly of smaller fish species. A greater variety of habitat types was associated with the riverine floodplain and perennial swamp relative to the seasonal swamp and drainage rivers. The variety of habitat types between ecotones is associated with the degree of flood inundation in the respective ecotones. During the course of this study, annual recruitment of fish into the drainage rivers was from refugia in the seasonal swamp whereas the greatest degree of lateral and longitudinal movement was in the riverine floodplain and perennial swamp. Movement was in response to both biological requirements, such as availability of food and spawning sites, and physical features of the environment, such as the changing water depth. The total catch per unit effort (CPUE) of fish throughout the year was more constant in the riverine floodplain and perennial swamp than in the seasonal swamp and drainage rivers where CPUE fluctutated widely. An increase in CPUE during the duration of this study was apparent and related to the magnitude of the annual flood. In contrast to most other African wetlands, the arrival of the annual flood in the Okavango Delta coincides largely with the dry winter months. This situation presented an opportunity to compare the influence of floods and water temperature on the reproductive biology of the selected fish species. The results show a definite pattern and indicate that both the flood cycle and increased water temperatures greatly influence the breeding cycles of the selected species. The tilapia Oreochromis andersonii exhibited a considerable degree of phenotypic plasticity. Fish from the seasonally inundated areas showed a smaller mean size, egg size and larger number of eggs relative to fish in the perennially flooded areas. The size at sexual maturity was also smaller. These different reproductive characteristics exhibited by O. andersonii are dependent on the degree of water retention in the different habitats. The fishes of the Okavango have adopted other reproductive strategies to survive the changing environmental conditions brought about by an annual flood cycle. These strategies include the construction of foam nests, as described for Hepsetus odoe, for guarding the young and to provide an oxygen-rich environment. Two main non-piscivorous feeding pathways were identified in the Okavango. These are a detritus pathway based on dead plant and animal material, and an epiphyte pathway, based on algae and invertebrates that are attached to plant stems. Seasonal changes in diet in relation to the annual flood were recorded. The most dramrtic change was demonstrated by the catfish Clarias gariepinus which congregates in mass aggregations in the northern regions of the Delta and hunt in packs. Pack-hunting by catfish is a regular response to the annual fluctuations in water level. It is my conclusion that the main flow of biotic and abiotic stimuli within the Okavango Delta originates from the relatively hydrologically stable riverine floodplain and perennial swamp ecotones to the widely fluctuating seasonal swamp and drainage rivers ecotones. The relatively stable ecotones allow a diverse and biotically interdependent fish community to develop, whereas the widely fluctuating seasonal swamp and drainage rivers ecotones are characterized by a less diverse and interdependent fish community. The degree of abiotic and biotic interdependence among fish in an ecotone is very important for the long term management of the Okavango Delta. Potential developers have to determine whether the effect of a given action by man is likely to result in a long term disturbance or merely in an elastic recoil to a more or less similar state. Recommendations are made on the conservation and management of Okavango fishes taking into account the ecological characteristics of the delta.
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International river basin management : a case study of the Okavango River Basin.Chase, Michael John. January 2002 (has links)
This dissertation reviews the principles of International River Basin Management and their
application by the governments of Angola, Botswana and Namibia. The dissertation deals with the
issues popularised by governments, water planners and international agencies that the twenty-first
century's conflicts will be fought over water. Increasingly this concern is being used to justify new
water-supply dams and river diversion projects. This is especially so in arid Southern Africa, the
focus of this dissertation, where numerous major international water transfers are underway and
many more are being planned. While Namibia's growing thirst is a serious problem, the story is more
complicated than just too many basin states putting their straws into one glass. The growing conflicts
over the Okavango's water use raise broader questions about ownership of common resources, and
equity of access to those resources.
Most southern African countries depend on primary natural resources to sustain economies and their
people. The environmental issues are remarkably similar in countries within the region, and the
economic, social and political fortunes of the individual countries are intertwined. Furthermore, the
ways in which resources are being managed are similar and thus cause for common concern. In
general, the ability of countries in the region to achieve sustainable development depends not on
national policies but also on the commitment of neighbours to practice sound environmental
management. This is because activities in one country can easily cause impacts on a neighbour and
possibly result in "downstream" opportunity costs.
This case study of the Okavango River Basin, a river facing prospective developments from riparian
states Angola, Botswana and Namibia, attempts to find sustainable solutions to solving international
resource conflict. In addition to outlining the possible future threats to the Okavango River, this
study proclaims a number of recommendations in the way of declaring alternatives to Namibia's
plans to extract water from the Okavango River. One such recommendation is the encouragement of
Water Demand Management as an alternative to water transfer by Namibia. This management
strategy is aimed at optimising the use of available water rather than developing new or extended
supplies and as a result it has a vital role to play since it contributes to sustainable development rather than over exploitation of limited natural resources. The majority of large rivers in the Southern African Development Community (SADC) are shared by
three or more countries, and as the region's water resources come under growing development
pressure, the importance of establishing effective national and regional methods and institutions for
sustainably managing these resources will increase greatly. From economic, ecological and human
welfare perspectives, the Okav,ango River Basin is arguably one of the most important transboundary
natural resources (TBNR) in the region. Owing to the basin's remoteness and history of conflict, the
Okavango was spared much of the destructive developments that rivers in the region have suffered.
As a result, the relatively pristine Okavango ecosystem continues to provide significant benefits to
the region much as it has done for centuries. As we approach the new millennium, however, it is
clear that the health of the Okavango River Basin is threatened as riparian states increasingly turn to
the Okavango to support their growing populations and economies. / Thesis (M.Env.Dev.)-University of Natal, Pietermaritzburg, 2002.
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Histomorphology as a tool to assess the health status of five economically important fish species in the Okavango Delta Panhandle, Botswana.Mokae, Motsidisi Lorraine Lolo 14 January 2014 (has links)
Ph.D. (Zoology) / Histomorphology as a tool to assess the health status of five economically important fish species in the Okavango Delta Panhandle, Botswana the Okavango Delta, and an inland freshwater wetland of national and international importance was designated by the Ramsar Convention in 1996. This site is of global importance because of a wide diversity of fish species found in this freshwater ecosystem. The Okavango Delta is also one of the last 'near pristine' sites on the African continent and therefore serves as an ideal reference site to describe the normal histomorphology of selected organs in sentinel fish species which could be used as reference for future toxicological studies. The aim of this study was to assess the health status of five economically important fish species namely, Clarias gariepinus (Burchell, 1822), Clarias ngamensis (Castelnau, 1861), Serranochromis robustus jallae (Gunther, 1864), Serranochromis angusticeps (Boulenger, 1907) and Hydrocynus vittatus (Castelnau, 1861) sampled from the Okavango Delta Panhandle, by describing the normal histomorphology of the liver, gills and gonads of the sentinel species. The sentinel fish species are of significant importance because they form an integral part of the small-scale commercial, subsistence and recreational fisheries in this ecosystem. In the past few decades, fish-health research has focused almost exclusively on histopathological alterations resulting from pollution caused by exposure to chemicals, parasitesand pathogens. Limited attention has been devoted to the normal histomorphology and health status of fish species in various aquatic ecosystems including the Okavango Delta Panhandle. Also, histopathological evaluations noted only the presence of abnormalities without quantitative assessment of the extent of the abnormalities within each tissue section. The absence of baseline normal histomorphology and numerical data however, makes it difficult to establish cause-and-affect relationships between pathology and contamination patterns in various fish species. It is imperative therefore, that the normal histomorphology of organs in fish species occurring in this region should be known so that histopathological conditions maybe accurately diagnosed…
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Dry woodland and savanna vegetation dynamics in the Eastern Okavango Delta, Botswana.Tedder, Michelle Jennifer. 15 November 2013 (has links)
The Okavango Delta is an extremely dynamic system with variable vegetation comprised of permanent
swamps, seasonal swamps, dry islands, floodplains and dry grassland, savanna and woodland. The system
is largely driven by the interaction between fire and the annual flood, which filters down from the
Okavango River catchments in Angola. While extensive research has been conducted on the flood-driven
vegetation little is known about the dry woodland and savanna regions bordering these flood-driven
habitats. A taxonomic classification of woody species composition resulted in eleven vegetation types.
These data were then reanalyzed in terms of woody species morphology allowing these eleven vegetation
types to be grouped into four functional response groups in order to provide a platform for improving the
understanding of how dry woodland and savannas interact with the environment. These four groups were
the savanna group mixed thornveld and the three woodland groups; mixed broadleaf woodland, shrub
mopane woodland and tall mopane woodland. Burning in mixed thornveld and mixed broadleaf woodland
was found to decrease woody species density and grass fuel loads and could be used for grazing
management to remove unpalatable growth and improve grass species composition, while burning in
shrub mopane woodland and mixed mopane woodland merely decreased the woody understory and is not
recommended. Utilization dominated by grazing livestock resulted in overutilization of the grass sward
leading to bush encroachment in both mixed thornveld and shrub mopane woodland, while utilization by
goats alone resulted in underutilization of the grass sward and a dominance of herbaceous annuals.
Livestock utilization had no effect on the occurrence of Pecheul-loeschea leubnitziae, a shrubby pioneer
previously thought to be an indicator of overgrazing, however extensive P. leubnitziae cover was
associated with a sward dominated by shade-tolerant grasses with low forage quality. Shrub mopane
woodland and tall mopane woodland appear to be more stable vegetation states than mixed broadleaf
woodland and mixed thornveld being less vulnerable to colonization by pioneer species and alteration as a
result of utilization or environmental factors. For this reason management and monitoring of mixed
thornveld and mixed broadleaf woodland is essential to prevent vegetation degradation and to ensure
optimal forage availability for both livestock and wildlife. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2012.
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Habitat vulnerability for the Nile crocodile (Crocodylus niloticus) in the Okavango Delta, BotswanaShacks, Vincent 12 1900 (has links)
Thesis (MA (Geography and Environmental Studies))--University of Stellenbosch, 2006. / The Okavango river along the panhandle of the Delta, in Botswana, is home to many wildlife species as well as to many large village communities. Local communities rely on the riverine system and its resources for subsistence and commerce. Activities associated with the utilization of these resources are governed by the fluctuating water levels of the river, which inhibit access during high water levels and allow access during low water levels. The high intensity of activities, such as reed harvesting, fishing and increased tourism, during low water periods coincides with the breeding season of many wildlife species in the system, including the Nile crocodile (Crocodylus niloticus). Over 90% of crocodile breeding areas in the Delta are found only in the panhandle region. The association between the intensity of human activities in the floodplains and crocodile nesting activity means that much of the habitat required for nesting is vulnerable to human disturbance and this could have severe negative impacts on the future of the Okavango crocodile population.
The study evaluated habitat vulnerability by mapping and spatially comparing habitat suitability, based on optimum environmental requirements for crocodile nesting, and human disturbance factors. A detailed crocodile nesting survey was carried out to locate and test all nesting sites according to criteria selected by species experts. The results from the survey were used to locate suitable nesting habitat in the study area by analysis in a Geographic Information System (GIS). Disturbance factors were visually identified and their locations in the study area spatially mapped. Their spatial influences on crocodile nesting were used as factors in a Multi-Criteria Evaluation (MCE) that evaluated the combined effect of the disturbances on the area defined as suitable crocodile habitat. The results indicate the extent of habitat vulnerable to human disturbances.
The results from the study show that 59% of once suitable crocodile habitat is currently disturbed by human activities. Most of the remaining 41% of undisturbed habitat is located along the Moremi/Phillipa side channel, which represents a core area for protection measures to be instated. The study recommends the declaration of a crocodile nesting sanctuary in this side channel to ensure the breeding success of this keystone species.
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The value of the Okavango delta : a natural resource accounting approachMmopelwa, Gagoitseope 07 December 2006 (has links)
Economic valuation of the Okavango Delta can support decision making in a complex socio-economic environment in which economic development depends on a deep understanding of the value of biodiversity. The use of a natural resource accounting framework in determining the value of goods and services is crucial. The total economic value of the Okavango Delta was estimated by using primary (household valuation) and secondary data. A natural resource accounting framework was used. The components of the total economic value were the composition of wild herbivores and vegetation, and the functional values, which comprised direct use values of wild herbivores, river reed, thatching grass, wild fruits, fuelwood and palm leaves, indirect consumptive values of honey production, carbon sequestration, livestock grazing, milk production, non-consumptive use of tourism, and existence and bequest values. The values of the composition and function are expressed in per/ha values. The value of the composition of wild herbivores was estimated at P1 444 992 400 (US$ 294 850 699.2) or US$ 27.4/ha, while the functional value was estimated at P185 913 117.4 (US$ 37 527 840.96 or US$ 619.77/ha. Of the estimated direct use values of vegetation, river reed had the highest value of US$ 29.0/ha, while the highest value among indirect use values was that of milk production (US$ 8.5/ha). These values of selected resources reflect the contribution of the value of biodiversity of the Okavango Delta to the overall economy of the country and represent initial estimates of costs to society if these resources are lost. The estimated values can be used to raise awareness among decision makers of the economic benefits of conserving the Okavango Delta. Overall, the findings showed that the various components of the total economic value of the Okavango Delta were comparable to other wetlands in the region. / Thesis (PhD (Agricultural Economics))--University of Pretoria, 2006. / Agricultural Economics, Extension and Rural Development / unrestricted
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