Kavango River Research Articles

First Azygiid Reported from Africa or a Characiform Fish: Plenivitellinum kifi n. gen., n. sp. (Digenea: Azygiidae) Infecting the Gut of African Tigerfish, Hydrocynus vittatus Castelnau, 1861 (Characiformes: Alestidae) from the Kavango River.

This paper aims to describe Plenivitellinum kifi n. gen., n. sp. (Digenea: Azygiidae) infecting the gastrointestinal tract of the African tigerfish, Hydrocynus vittatus Castelnau, 1861 (Characiformes: Alestidae) in the Kavango River, Namibia. We revise the diagnosis of Azygiidae Lühe, 1909 to accommodate this new species. The worm was heat-killed, fixed in 10% neutral buffered formalin, stained in Van Cleave's and Ehrlich's hematoxylins, cleared in clove oil, and mounted on glass slide using Canada balsam. The new azygiid resembles species of Otodistomum Stafford, 1904 by having an elongate body, a ventral sucker that is wider than the oral sucker and that is in the anterior half of the body, a pre-testicular ovary, a uterus that primarily occupies the inter-caecal space between the ovary and the ventral sucker, and a vitellarium that is restricted to the hindbody and that is confluent posteriorly in the post-testicular region. The new genus differs from all species of Azygiidae by having the combination of a ventral sucker that is wider than the oral sucker (vs. narrower), an elongate prostatic sac that extends posteriad to near the posterior margin of the ventral sucker (vs. an ovoid prostatic sac that is wholly anterior to or slightly overlaps the anterior margin of the ventral sucker), a vitellarium that nearly fills the post-testicular space and that extends posteriad beyond the caecal tips (vs. a vitellarium that is separate posteriorly or that is restricted to the anterior half of the post-testicular space and does not extend posteriad beyond the caecal tips), and an I-shaped excretory bladder (vs. Y-shaped). This study documents the first record of an azygiid from Africa and the first record of an azygiid infecting a characiform fish.

Examining the Drivers of Land Use /Land Cover Change: A Case of the Kavango River Basin and its Immediate Environments in Namibia

Understanding the drivers of land cover changes (LULCC) is very crucial for the development of management strategies as well as policy improvement and the sustenance of ecosystem services. This is crucial in preventing further degradation and proper planning of sustainable natural resources management. In this study, an attempt has been made to identify the drivers of LULCC in the Kavango East and West Regions of Namibia, from 1990 to 2018. Remotely Sensed Images were used to compute indices. Socio-economic surveys were conducted using structured interviews to share the past experiences of the local people, some key informants, and other stakeholders in the region. A combination of this information together with the Remote Sensing data was then used to derive the drivers of LULCC in the study area. Results of the study showed that changes were triggered by the interplay of more than five drivers identified and related to the environment, socio-economic, and other technical factors. In particular, the establishment and expansions of agricultural land, settlement, urbanization, and lumbering (for timber and crafting) were viewed by local people as the leading cause of deforestation. Other factors such as drought, flooding, and lumbering (for construction and firewood) cannot be undermined. Future studies will be targeted at assessing these drivers to evaluate their impacts on achieving sustainable development in the Kavango River Basin of Namibia and its immediate environments.

Evidence for overfishing of tigerfish Hydrocynus vittatus (Castelnau 1861) in the Kavango River, Namibia

The fishery for the African tigerfish Hydrocynus vittatus in northern Namibia makes a substantial contribution to surrounding food security and stimulates the local economy through subsistence and recreational fishing. However, local fishers suggest that catch rates of H. vittatus have declined and the fish are now smaller. The Namibian Ministry of Fisheries and Marine Resources conducted annual gill net surveys in the Kavango River from 1994 to 2018. These standardised surveys were used to compare catch per unit effort data and length frequencies of H. vittatus between intensively fished areas and a freshwater protected area (FPA). The catch per unit effort (by numbers and mass) and proportion (56% vs 10–20%) of mature fish (males >180 mm fork length and females >280 mm fork length) were higher inside the FPA, compared with those outside. The H. vittatus populations, both outside and inside the FPA, are subject to overfishing and management actions should be taken to secure this important fishery resource for subsistence and recreational fishers.

Local people’s perceptions about Land Use Cover Change (LULCC) for sustainable human wellbeing in Namibia

Land use/land cover change (LULCC) has taken unprecedented rates in all corners of the world. The accelerated rate of change has affected ecosystem functioning and human well-being. It, therefore, warrants research and constant monitoring to provide crucial updated information for sustainable conservation, especially in semi-arid environments, and the current changing climate. This study investigated local people's perception of LULCC in the Kavango River Basin of Namibia. Coupled with relevant literature, the key informants and local community members were interviewed to provide primary information about the observed changes and also to supplement the existing secondary data. The study revealed that Kavango West and East, key informants, have different perception about the changes they have witnessed. The Kavango East people think the establishment of protected and community forest areas led to decrease in available land for farming. This created enclaves of communities in the middle of protected areas that continue to lose crops and livestock to wildlife. However, the Kavango West attribute forest-land loss to agricultural activities and land abandonment due to degradation. This implies the area is undergoing fragmentation from LULCC which is a threat to ecological biodiversity. This study presents the perception of local communities about LULCC's offering vital information needed in designing targeted interventions for land degradation. Therefore, all stakeholders should work together to ensure the sustainable co-existence of communities and natural resources for sustainable human well-being.

First observation of fouling of externally attached radio transmitters in an African river

Fouling of externally attached tags is an important consideration in long-term tagging studies as it may affect fish behaviour and well-being. Two externally attached radio transmitters on African tigerfish Hydrocynus vittatus were covered with short green algae, after the fish were recaptured 49 and 64 days after tagging in the Kavango River, Namibia. This is the first observation of fouling on external radio transmitters from any African river which highlights the importance of conducting studies that evaluate the various health or behavioural effects resulting from tagging.

Implications of the movement behaviour of African tigerfish Hydrocynus vittatus for the design of freshwater protected areas.

African tigerfish Hydrocynus vittatus (n = 35) were tagged with external radio-transmitters in the Kavango River, Namibia, to determine whether freshwater protected areas could be an effective tool for the management and conservation of this species. They were manually tracked in the core study area of 33 km every c. 12 days from July-October 2016 to May 2017 for between 123 to 246 days. In addition, 14 extended surveys were carried out for up to 680 km to determine the total area use of the tagged individuals. Tigerfish displayed at least two behavioural patterns either having high site fidelity with shorter movements or using larger areas with longer movements. Twenty-three (66%) of the tigerfish had high site fidelity using an area of less than 33 km of river, whereas 12 tigerfish (34%) undertook long distance movements of up to 397 km upstream and 116 km downstream from their tagging locations. During the long-distance movements tigerfish crossed the territorial boundaries of Angola, Namibia and Botswana. Of the 35 fish that were monitored, 14 (40%) spent more than 80% of the monitored time in the 33 km study area and 18 (51%) stayed within the study area for at least 50% of the monitored time. These findings suggest that freshwater protected areas may be a useful management tool and we predict that a protected river area of 2-5 km river length could protect 25.9-34.6% of the population for at least 75% of the time whereas protection of 10 km river length could protect at least 50% of tigerfish for at least 75% of the time.

Knowledge, Attitudes and Practices of the University Students on Malaria Prevention in Kavango East, Namibia

Malaria remains a public health concern in Namibia and it is endemic in many regions, including Kavango east region. University students in Kavango east region are at risk of malaria due to bushy environment and the presence of Kavango river, which makes it easy for mosquitoes to multiply. This study aimed to assess and describe knowledge, attitudes and practices of malaria prevention among university students. A quantitative descriptive cross-sectional study was conducted, using a pretested questionnaire to collect data from 239 university students in Kavango east region. A proportionate stratified random sampling was used to sample students from the three faculties on campus. Data were analysed with a Statistical Programme of Social Sciences.
 
 The overall response rate was 75% (239) from a total of 318 respondents. Mean age was 21.4 years, respondents comprised of 155 (64.9%) females and 84 (35.1%) males. Almost all respondents (94.5%) know that malaria is transmitted by mosquitoes and 80% of respondents indicated that malaria is preventable. Usage of mosquito net was the most commonly known preventive measure, indicated by 224 (94%) of respondents. The vast majority of respondents 227 (95%) agreed that the appropriate method to prevent self from getting malaria is to prevent mosquito bites. Surprisingly 80 (33%) of the respondents believe that only children and pregnant women get malaria and therefore it’s only them who need preventive measures. Only 43 (18%) of the respondents always sleep under mosquito nets to prevent themselves from getting malaria. It was concluded that university students in Kavango east region have good knowledge on malaria prevention measures. Although there were some misconceptions noted, especially on the identification of population at risk of malaria, the attitudes on malaria prevention are generally satisfactory. However, the knowledge and attitudes do not reflect in the students’ practices. 

Comparing the fish assemblages and food‐web structures of large floodplain rivers

Abstract The Upper Zambezi, Kavango and Kwando are large floodplain rivers with substantial biodiversity, providing water and ecosystem services to a large tract of southern Africa. These rivers differ in hydrological regime. The Upper Zambezi and Kavango rivers are in flood for 4 months (March, April, May, June) while, in the Kwando River, floods are later and last for 1–2 months in July and August. The Upper Zambezi River has the largest annual flood pulse, followed by the Kavango River, while the Kwando River experiences small and unreliable floods. During years of exceptional flooding of the Upper Zambezi and Kavango rivers, the rivers are interconnected at peak flows and therefore share a common ichthyofauna. This provided a natural experiment to investigate the responses of fish communities comprised of the same species to differing flood regimes by comparing the fish assemblages and food‐web structures between rivers. Fish assemblage structure was characterised by analysing biomass catch per unit effort data collected using gillnets in all water‐level seasons for all three rivers. Whole ecosystem‐stable isotope data collected once from each river were used to examine differences in food‐web structure and fish feeding ecology between rivers. Due to temporal differences in hydrology, the Upper Zambezi and Kavango river food webs were characterised during the low and falling water seasons, while the Kwando River food web was sampled during the rising water season. In the Upper Zambezi and Kavango rivers, fish assemblages varied with hydrological season due to the homogenising influence of the flood pulse, while in the Kwando River fish assemblages did not change seasonally. The Upper Zambezi River food web had a restricted nitrogen range (NR = 0.90), with a reduced food chain length and predators did not occupy elevated trophic positions compared to those in the Kavango and Kwando river food webs (NR = 1.05 and 0.97 respectively). The Kwando and Kavango rivers are less exploited than the heavily fished Upper Zambezi River, where fishing has reduced the abundance of primary and tertiary consumers, potentially resulting in the observed reduction in food chain length. The Upper Zambezi and Kavango river food webs were based on differing basal resources compared to the Kwando River food web. The Upper Zambezi and Kavango river food webs were likely supported by 13C‐enriched resources such as C4 riparian vegetation from the floodplain, while the Kwando River food web was likely based on 13C‐depleted resources such as filamentous algae and aquatic macrophytes. The influence of the varying flood pulses on the fish communities of these three rivers supports the flood pulse concept. There is also evidence that food‐web structures differ between rivers but, due to differing hydrological regimes in the rivers, further study is required to understand causal factors. These ecosystems are increasingly impacted by human population growth and development, as well as climate change, and improved predictions in fish community and food‐web structure in relation to flood pulse changes are important for ecosystem management in future.

Validation of annulus formation in sagittal otoliths of three tropical cichlids Oreochromis andersonii (Castelnau, 1861), Oreochromis macrochir (Boulenger, 1912), and Coptodon rendalli (Boulenger, 1896)

Summary The periodicity of growth zone formation in sagittal otoliths of Oreochromis andersonii, Oreochromis macrochir and Coptodon rendalli from the Upper Zambezi region, southern Africa, was validated to test the hypothesis that a single growth zone is deposited annually. Edge analysis was carried out on 754 O. andersonii (54–492 mm TL), 601 O. macrochir (83–438 mm TL) and 622 C. rendalli (45–379 mm TL) caught between August 2010 and August 2011 in Lake Liambezi and the Kavango, Kwando and Upper Zambezi rivers. This was corroborated for O. andersonii (n = 17) and C. rendalli (n = 16) using a fluorochrome marking experiment conducted in a large earthen pond (625 m2, 1.5 m deep) adjacent to the Kavango River. Both methods demonstrated that growth zone deposition occurred annually in juvenile and adult fishes. For edge analysis, the highest proportion of otoliths with an opaque margin was observed in summer from October to December. The fluorochrome marking experiment, however, revealed that opaque zone deposition took place in winter between June and September when water temperatures were lowest (17°C), indicating a lag between opaque zone deposition and detection on the otolith edge.

Isolation and Screening of Rhizosphere Bacteria from Grasses in East Kavango Region of Namibia for Plant Growth Promoting Characteristics.

A diverse group of soil bacteria known as plant growth promoting rhizobacteria (PGPR) is able to inhabit the area close to plant roots and exert beneficial effects on plant growth. Beneficial interactions between rhizospheric bacteria and plants provide prospects for isolating culturable PGPR that can be used as bio-fertilizers for sustainable crop production in communities that cannot easily afford chemical fertilizers. This study was conducted with the aim of isolating rhizospheric bacteria from grasses along the Kavango River and screening the bacterial isolates for plant growth promoting characteristics. The bacteria were isolated from rhizospheres of Phragmites australis, Sporobolus sp., Vetiveria nigritana, Pennisetum glaucum and Sorghum bicolor. The isolates were screened for inorganic phosphate solubilization, siderophore production and indole-3-acetic acid (IAA) production. The nitrogen-fixing capability of the bacteria was determined by screening for the presence of the nifH gene. Up to 21 isolates were obtained from P. australis, Sporobolus sp., S. bicolor, P. glaucum and V. nigritana. The genera Bacillus, Enterobacter, Kocuria, Pseudomonas and Stenotrophomonas, identified via 16S rDNA were represented in the 13 PGPR strains isolated. The isolates exhibited more than one plant growth promoting trait and they were profiled as follows: three phosphate solubilizers, four siderophore producers, eight IAA producing isolates and five nitrogen-fixers. These bacteria can be used to develop bio-fertilizer inoculants for improved soil fertility management and sustainable production of local cereals.

Operational river discharge forecasting in poorly gauged basins: the Kavango River basin case study

Abstract. Operational probabilistic forecasts of river discharge are essential for effective water resources management. Many studies have addressed this topic using different approaches ranging from purely statistical black-box approaches to physically based and distributed modeling schemes employing data assimilation techniques. However, few studies have attempted to develop operational probabilistic forecasting approaches for large and poorly gauged river basins. The objective of this study is to develop open-source software tools to support hydrologic forecasting and integrated water resources management in Africa. We present an operational probabilistic forecasting approach which uses public-domain climate forcing data and a hydrologic–hydrodynamic model which is entirely based on open-source software. Data assimilation techniques are used to inform the forecasts with the latest available observations. Forecasts are produced in real time for lead times of 0–7 days. The operational probabilistic forecasts are evaluated using a selection of performance statistics and indicators and the performance is compared to persistence and climatology benchmarks. The forecasting system delivers useful forecasts for the Kavango River, which are reliable and sharp. Results indicate that the value of the forecasts is greatest for intermediate lead times between 4 and 7 days.

Makongoro are the Hafumu of water and we respect them, or the ethno-philosophical foundation of customary water law in the Kavango Region of Namibia

Interviews on customary water law have been conducted within the framework of the TFO Project since March 2011. The research was meant to generate qualitative information on water, the Kavango River as the main source of water, but also locally pumped water or water provided by the Namibian public provider of water, NamWater. The intention of the of the (now completed) first phase of the research was to investigate the general perceptions of the people on water. The second (still ongoing) phase of the research looks at more specific matters, such as access to water, control of access, rules against pollution and rules to protect water etc. The purpose of this article is to present results of the first phase of the research, focusing on Ekongoro, the mythical figure that is widely reflected in the perception of water by the people in the research area. Who or what is Ekongoro? What is the social meaning of Ekongoro? Is there any legal relevance of Ekongoro? There is when taking note of what was stated by an interviewee: are the Hafumu of water- the Makongoro are the rulers of water - and we respect them. The very special placement of Ekongoro shows that Ekongoro is part of a network of relationships that reaches from human connotation in the specific sense to humanised non-human and even supra-human connotations. What the narratives about Ekongoro convey is an important ingredient of a worldview which could inspire the worldview of western societies, even prompt to amend the dominant attitude in this worldview in accordance with which nature is an almost unlimited object of scientific and commercial exploitation. However and primarily concerned with societies in which the narratives about Ekongoro exist, the research has discovered a complex framework of arguments in the customary percep- tion of water that stimulates questions on the role and function of this framework in the foundation of societal politics and law.

Lestinogomphus silkeaesp. nov. from the Okavango and Zambezi Rivers (Odonata: Gomphidae)

Lestinogomphus silkeae sp. nov. from the northern Okavango Delta in Botswana, the Kavango River in northern Namibia and the middle Zambezi River in Zimbabwe is described and illustrated (holotype ♂: Botswana, Xaro Lodge, 09 vi 2000, dep. at ZMBH). The shape of the male appendages distinguishes this species from all others in the genus. The new species is compared with the widespread type species of the genus, L. angustus.

Climate and weather factors modulating river flows in southern Angola

AbstractThe large‐scale circulation and thermodynamic fields that modulate the flow of the Kavango River in southern Angola during austral summer are studied. According to composite patterns constructed from National Center for Environmental Prediction (NCEP) data, enhanced river flow is associated with an anomalous wave train of upper level winds that emanate from the North Atlantic. Sea‐surface temperatures (SST) show a warm‐north/cool‐south Atlantic dipole condition as the Kavango River rises. Correlations are analysed with respect to the Kavango River flow and a 0 lag value of − 0.41 is found for the upper zonal wind over the North Atlantic. Rainfall over the African Sahel region is positively linked with Kavango River flow at 6 month lead time (r = + 0.34). The work is extended to the event scale and it is found that winds draw tropical moisture over southern Angola in response to an anomalous low‐high pair and bifurcated subtropical jet stream. A continental scale sea breeze circulation amplifies the convection during afternoons. Knowledge of run‐off into Namibia is critical to the management and planning of water resources in the northern Kalahari savanna. Copyright © 2009 Royal Meteorological Society

Landscapes of Power: Ownership and Identity on the Middle Kavango River, Namibia**

This article examines traditions of origin among riparian communities living in a semi-arid environment as a means of exploring how the environment and socio-political identities are mutually constituted. Within Namibian Kavango communities over the past half century, such traditions have fallen into two general categories: those of the royal clans (accepted by most residents) which state that they were the first to settle this section of the river, and those of other groups who claim that their own clans were the real first-comers but were later subordinated by the immigrant kings. Each group of traditions claims prior origins from similar riparian environments as a means of demonstrating how their group was able to tame the wilderness. Indeed, both the royalist and the indigenous traditions rest on shared assumptions about how ownership is established: through first-comer status and through creating ‘country’, or a place fit for human communities, out of ‘bush’ or wilderness. Autochthon–immigrant relationships were probably long fraught with tension here, as they were in other parts of southern Africa. Embedded within some of the indigenous traditions are hints of ‘charters’ establishing relations between the two groups. However, the colonial and postcolonial experiences have resulted in the erasure of autochthonous communities from royalist historical narratives. Chiefs needed to prove ownership of their communities to colonial officials seeking to impose a form of indirect rule, and colonial and postcolonial interventions into riparian communities affected all residents and broadened the definition of indigeneity to include all Kavango people. Indigenous traditions survive to some extent within the community, but they are increasingly irrelevant in a political landscape in which everyone has become an indigene at the mercy of strangers from afar and in which ownership is no longer properly exercised by anyone.

Fish response to the annual flooding regime in the Kavango River along the Angola/Namibian border

The results of the first seasonal survey of the fish of the Kavango River floodplain along the Angola/Namibia border are reported. The river experiences peak flooding from February through June, with the 375-km long floodplain extending up to 5 km across. The floodplain was sampled five times in 1992 by seine, fish traps and rotenone. The data indicated a pronounced structural and functional response of the fish community in relation to the alternating flood and drought conditions in the river. Catch per unit effort and diversity were highest during months of peak flooding (May and June), and lowest during the month of least flow (November). The reproductive strategies of K-selected piscivorous cichlids and tigerfish were in advance of flooding. Many r-selected invertivores, especially cyprinids, were in relative synchrony with flooding and the stimulation of littoral zone plant growth, while other invertivores lagged the cyprinids. Herbivores had lowest relative abundance during peak flooding; this seemingly inverse relationship with the invertivores should not be interpreted as replacement, but rather the swamping of the system with young-of-the-year r-selected invertivores. The data support the Flood Pulse Concept, which hypothesizes that flooding is the major “driver” of productivity in lowland or floodplain rivers. Keywords: behaviour, floodplain fishery, migration, Okavango Delta, r-/K-selection, subsistence fishery African Journal of Marine Science 2001, 23: 449–464

A Review of the African Adinopsis Species with Description of Two New Species from Northern Namibia. (Coleoptera, Staphylinidae, Aleocharinae)

Two new Adinopsis species from the banks of the Kavango River and connected temporary lakes in the Caprivi strip in Northern Namibia are described and illustrated: A. maraisi spec. nov. and A. deckerti spec. nov. (type localities: Namibia, Kavango, Mahango Game Reserve, 18°17′S/21°43′E, respectively 18°14′S/21°43′E).The African Adinopsis species are reviewed, catalogued and keyed.

Adinopsis klimaszewskii sp. n. from the Popa Falls in Northern Namibia. (Coleoptera, Staphylinidae, Aleocharinae)

AbstractAdinopsis klimaszewskii sp. n. from the banks of the Kavango River at Popa Falls in the Caprivi strip in Northern Namibia is described and illustrated. Type locality: Namibia, Kavango, Popa Falls, 18°07′S/21°35′E.