Chiredzi, Zimbabwe
Chiredzi, Zimbabwe

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Capon S.D.,Stellenbosch University | Leslie A.J.,Stellenbosch University | Clegg B.,Malilangwe Wildlife Reserve
Koedoe | Year: 2013

Populations that are vulnerable to decline are of particular concern to wildlife managers and uncovering the mechanisms responsible for downward trends is a crucial step towards developing future viable populations. The aims of this study were to better understand the mechanisms behind the historic decline of the sable antelope, Hippotragus niger, population at the Malilangwe Wildlife Reserve (MWR), to assess its future viability and to use this analysis to determine key areas of breakdown in population growth and link these to potential limiting factors. VORTEX, a population viability model was used to assess the future viability of the sable antelope population and a sensitivity analysis was applied to identify the key areas of breakdown in growth. The sable population is currently viable, but remains highly vulnerable to changes in adult female survival, a factor which had the greatest influence on overall population fitness. Lion predation, impacting on the adult segment of the population, appeared to be the main factor responsible for the historic decline at the MWR. © 2013. The Authors.

Packer C.,University of Minnesota | Loveridge A.,University of Oxford | Canney S.,University of Oxford | Caro T.,University of California at Davis | And 58 more authors.
Ecology Letters | Year: 2013

Conservationists often advocate for landscape approaches to wildlife management while others argue for physical separation between protected species and human communities, but direct empirical comparisons of these alternatives are scarce. We relate African lion population densities and population trends to contrasting management practices across 42 sites in 11 countries. Lion populations in fenced reserves are significantly closer to their estimated carrying capacities than unfenced populations. Whereas fenced reserves can maintain lions at 80% of their potential densities on annual management budgets of $500 km-2, unfenced populations require budgets in excess of $2000 km-2 to attain half their potential densities. Lions in fenced reserves are primarily limited by density dependence, but lions in unfenced reserves are highly sensitive to human population densities in surrounding communities, and unfenced populations are frequently subjected to density-independent factors. Nearly half the unfenced lion populations may decline to near extinction over the next 20-40 years. © 2013 Blackwell Publishing Ltd/CNRS.

Tuytens K.,Catholic University of Leuven | Vanschoenwinkel B.,Vrije Universiteit Brussel | Clegg B.,Malilangwe Wildlife Reserve | Nhiwatiwa T.,University of Zimbabwe | Brendonck L.,Catholic University of Leuven
Journal of Crustacean Biology | Year: 2015

Southern Africa is recognized as one of the world's diversity hotspots for large branchiopod crustaceans. Nonetheless, many areas including large parts of Zimbabwe remain poorly studied. We report on the diversity of anostracans and notostracans in a tropical and geologically diverse savannah area in SE Zimbabwe. We explored the links between geology, hydroperiod and diversity and distribution patterns of anostracans and notostracans. In a large survey, 160 temporary clay pans distributed over the four major and diverse geological regions were sampled every fortnight. Seven fairy shrimp and one tadpole shrimp species were recorded. Although the study area is characterized by substantial variation in soil geology, we did not find strong effects of geology on the composition of anostracan and notostracan assemblages in pools of different sizes and hydrology. All species occurred in all four geological regions but the abundance of pools without large branchiopods differed between the four investigated regions. © 2015. Published by Brill NV, Leiden.

Dalu T.,University of Zimbabwe | Dalu T.,Rhodes University | Clegg B.,Malilangwe Wildlife Reserve | Marufu L.,University of Zimbabwe | Nhwatiwa T.,University of Zimbabwe
Pan-American Journal of Aquatic Sciences | Year: 2012

The diet of the tigerfish, Hydrocynus vittatus (Castelnau 1861) from a small impoundment (Malilangwe reservoir) was investigated. The tigerfish is an introduced piscivorous fish in this reservoir. Stomach contents analysis indicated that the adult size classes were almost entirely piscivorous and showed diet shifts with size changes. Approximately 35% of the tigerfish diet consisted of cichlid fishes and also included large numbers of Gobiidae (31%), Cyprinidae (29%) and Clariidae (28%). Small size classes of tigerfish fed heavily on macroinvertebrates, in particular, the taxa Pleidae (18%), Chironomidae (13%), Chaoborus sp. (11.5%), Corixidae (7.7%), Baetidae (4%) and Notonectidae (7%). They later shifted to a diet of cichlids. Hydrocynus vittatus predator-prey length ratio averaged approximately 0.21. The study showed that H. vittatus has a varying food composition probably due to changes in food abundances and distributions within the reservoir. Thus it does not have a strict food regime and this gives it a better chance of survival.

Dalu T.,Rhodes University | Dube T.,University of South Africa | Froneman P.W.,Rhodes University | Sachikonye M.T.B.,Rhodes University | And 2 more authors.
Geocarto International | Year: 2015

Traditional approaches to monitoring aquatic systems are often limited by the need for data collection which often is time-consuming, expensive and non-continuous. The aim of the study was to map the spatio-temporal chlorophyll-a concentration changes in Malilangwe Reservoir, Zimbabwe as an indicator of phytoplankton biomass and trophic state when the reservoir was full (year 2000) and at its lowest capacity (year 2011), using readily available Landsat multispectral images. Medium-spatial resolution (30 m) Landsat multispectral Thematic Mapper TM 5 and ETM+ images for May to December 1999–2000 and 2010–2011 were used to derive chlorophyll-a concentrations. In situ measured chlorophyll-a and total suspended solids (TSS) concentrations for 2011 were employed to validate the Landsat chlorophyll-a and TSS estimates. The study results indicate that Landsat-derived chlorophyll-a and TSS estimates were comparable with field measurements. There was a considerable wet vs. dry season differences in total chlorophyll-a concentration, Secchi disc depth, TSS and turbidity within the reservoir. Using Permutational multivariate analyses of variance (PERMANOVA) analysis, there were significant differences (p < 0.0001) for chlorophyll-a concentration among sites, months and years whereas TSS was significant during the study months (p < 0.05). A strong positive significant correlation among both predicted TSS vs. chlorophyll-a and measured vs. predicted chlorophyll-a and TSS concentrations as well as an inverse relationship between reservoir chlorophyll-a concentrations and water level were found (p < 0.001 in all cases). In conclusion, total chlorophyll-a concentration in Malilangwe Reservoir was successfully derived from Landsat remote sensing data suggesting that the Landsat sensor is suitable for real-time monitoring over relatively short timescales and for small reservoirs. Satellite data can allow for surveying of chlorophyll-a concentration in aquatic ecosystems, thus, providing invaluable data in data scarce (limited on site ground measurements) environments. © 2015 Taylor & Francis.

Vanschoenwinkel B.,Catholic University of Leuven | Waterkeyn A.,Catholic University of Leuven | Nhiwatiwa T.,University of Zimbabwe | Pinceel T.,Catholic University of Leuven | And 4 more authors.
Freshwater Biology | Year: 2011

Recent findings hint at the potential importance of mammals affecting the spatial dynamics of aquatic organisms in areas where mammals live in close association with water. Perhaps the most iconic example of such an environment is the African savannah. We investigated dispersal patterns of freshwater organisms among a set of temporary ponds in SE Zimbabwe to test the hypothesis that large mammals, and particularly African elephants (Loxodonta africana), can be important vectors of aquatic organisms. Dispersal kernels were reconstructed by hatching mud collected from 'rubbing' trees located at increasing distances from a set of isolated ponds. To assess the relative importance of other mammalian vectors, the vertical distribution of mud on rubbing trees was mapped and related to the body size of candidate vector species. Laboratory hatching of mud samples revealed large numbers of propagules of 22 invertebrate taxa as well as some aquatic macrophytes. Dispersing communities reflected source communities and diverged with increasing distance from the source. Both dispersal rates and richness of transported taxa decreased significantly with dispersal distance. No indications for differences in dispersal capacity among propagule types were detected. Instead, common propagules were more likely to travel greater distances. Most mud was attached to trees at heights >1.5m, implicating elephants as the dominant vector. Vertical distributions of tree mud, however, also revealed clustering at heights up to 50cm and 90-120cm corresponding to the height of warthog, rhinoceros and buffalo, respectively. Finally, variation in the vertical distribution of mud on trees in combination with differences in vector vagility suggests that local differences in vector species composition may affect passive dispersal dynamics of aquatic organisms. Based on vagility and vector load, mud-wallowing mammals emerge as highly effective vectors that, in some areas, may be more important in transporting aquatic organisms than traditionally recognised vectors such as waterbirds. Since most large- and medium-sized mammals currently have restricted geographic distributions, it is likely that mammal-mediated dispersal was more important in the past. © 2011 Blackwell Publishing Ltd.

Dalu T.,University of Zimbabwe | Dalu T.,Rhodes University | Clegg B.,Malilangwe Wildlife Reserve | Nhiwatiwa T.,University of Zimbabwe
Knowledge and Management of Aquatic Ecosystems | Year: 2012

The aim of our study was to investigate macroinvertebrate communities so as to understand factors and processes structuring macroinvertebrate communities in a small reservoir, Malilangwe reservoir over seven months (April to October). Sampling was performed by active sweep netting and searching soil sediments. Water temperature, conductivity, dissolved oxygen, pH, ammonia, nitrogen, phosphorus, chemical oxygen demand and macrophyte cover were determined. In total, forty-two macroinvertebrate families belonging to 10 orders were identified amongst 13 macrophyte species and sediments. Thiaridae and Physidae (Mollusca) were the dominant and most abundant taxa (57.71%) and there were followed by the Hemiptera (27.31%). High indices for sites 1 to 3 for the Simpsons index, the Shannon-Weaver index and evenness were recorded, while low indices were observed for sites 4 to 5, with significant differences being observed among the study site using the Kruskal-Wallis ANOVA test (p < 0.05). Redundancy Analysis revealed that among environmental factors, hydrologically linked parameters such as conductivity, water level and macrophyte cover had the strongest influence on macroinvertebrate distribution. © ONEMA, 2012.

Dalu T.,University of Zimbabwe | Dalu T.,Rhodes University | Clegg B.W.,Malilangwe Wildlife Reserve | Nhiwatiwa T.,University of Zimbabwe
African Journal of Aquatic Science | Year: 2013

Fish diversity in Malilangwe Reservoir in the south-eastern lowveld of Zimbabwe was investigated in 2011 to determine the community structure. The aim of this study was to determine the current status of an artificial fish community in a small reservoir that does not normally overflow and to assess how the fish have adapted to this environment. Eight species belonging to five families were collected from the reservoir. The cichlids Oreochromis mossambicus, O. macrochir, O. placidus and Tilapia rendalli made up 46% by number of the sample, the cyprinid Labeo altivelis made up 40% of the sample, and T. rendalli, the least numerous species, made up 0.2% of the sample. The population of T. rendalli seemed to be depleted, whereas largemouth bass Micropterus salmoides, which were formerly numerous, appeared to be absent. Oreochromis placidus bred throughout the study period, whereas Clarias gariepinus, Hydrocynus vittatus, L. altivelis, O. macrochir and O. mossambicus showed an apparent lack of recruitment between July and August 2011. The growth performances of C. gariepinus, O. mossambicus, O. macrochir and O. placidus were assessed by means of the growth performance index (φ′) with values ranging from 3.10 to 3.41. The rates of total mortality (Z) were estimated for four species; the highest rate was 5.64 for O. placidus and the lowest was 1.17 for C. gariepinus. © NISC (Pty) Ltd.

Dalu T.,University of Zimbabwe | Dalu T.,Rhodes University | Clegg B.,Malilangwe Wildlife Reserve | Nhiwatiwa T.,University of Zimbabwe
African Journal of Aquatic Science | Year: 2013

The Lake Habitat Survey (LHS) method was developed to assess the ecological integrity of the physical habitat around lake and reservoir ecosystems, as well as to determine the magnitude of human pressure on lake systems. The LHS method has not previously been applied to tropical lakes but could potentially be a useful tool. The LHS approach was applied on a tropical African reservoir, Malilangwe reservoir, in 2011. The application of this methodology included the calculation of summary metrics Lake Habitat Metric Survey (LHMS) and Lake Habitat Quality Assessment (LHQA). Results show that although Malilangwe reservoir is experiencing increasing human pressure, it does not appear to suffer from a major invasion of alien plants. Its LHQA score, 76 out of 112, and LHMS score, 16 out of 42, are indicative of relatively few human pressures such as water pumping structures and residential areas. We conclude that the use of LHS can directly enhance the quality and reliability of hydromorphological assessments and can lead to better lake conservation and rehabilitation. It is clear that, for conservation management, a holistic assessment of naturalness, representativeness and species rarity needs to be made in conjunction with scoring systems. © 2013 Copyright NISC (Pty) Ltd.

Dalu T.,University of South Africa | Dalu T.,Rhodes University | Nhiwatiwa T.,University of South Africa | Clegg B.,Malilangwe Wildlife Reserve | Barson M.,University of South Africa
Knowledge and Management of Aquatic Ecosystems | Year: 2012

An assessment was carried out on the impact of Lernaea cyprinacea on fish populations ten years after its first outbreak in the Malilangwe reservoir, and Lernaea cyprinacea is currently showing no sign of declining in the reservoir. Eight fish species were examined for ectoparasite prevalence and intensity. The possible relationship between L. cyprinacea infestation and environmental factors were investigated. Two parasite species, L. cyprinacea in Oreochromis mossambiccus, Oreochromis placidus, Oreochromis macrochir, Labeo altivelis and Tilapia rendalli and trematode cysts (Clinostomoides brieni) in Clarias gariepinus were found. Lernaea cyprinacea prevalence was 100% amongst all cichlids but varied for L. altivelis. Parasite intensity increased during the cool, dry season (May to July), with the greatest mean intensity being observed amongst the cichlids. There was a significant relationship between parasite intensity and environmental factors; dissolved oxygen (p < 0.05), temperature (p < 0.001) and pH (p < 0.001). © ONEMA, 2012.

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