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This review explores some ecological aspects of the common hippopotamus (hippo), Hippopotamus amphibius L, threats to its population and contextual peculiarities affecting its conservation in selec...

Solid waste is increasing in Harare metropolitan owing to more affluent lifestyles, rapid urbanization and industrialization, obsolete litter disposing equipment and ineffective and erratic garbage collection schedules. A total of 3500 volunteers have been jointly trained as community-based anti-litter monitors by Harare authorities to curb solid waste challenges. This study assessed the effectiveness of involving communities in anti-litter monitors’ training initiatives through a comparative analysis of two adjacent suburbs in Harare, i.e. Mbare with the highest relative proportion of trained litter monitors and Sunningdale which was partially represented in the anti-litter monitors’ training programme. Impact on litter and residents’ knowledge, attitudes, behaviour and practices, trained and untrained, were assessed through litter measurements, questionnaires and focus group discussions. Litter quantities were 6.4 ± 1.3 kg/week in Sunningdale and 5.6 ± 4.5 kg/week in Mbare for streets assessed. Approximately 90% of the residents interviewed know that littering poses a serious risk to human and environmental health and the economy, and acknowledge that it is a punishable offence. 100% of residents interviewed in Mbare showed good to better attitudes towards anti-littering, whilst 17% in Sunningdale revealed a negative attitude towards anti-littering initiatives. Actual anti-littering behaviour and practices were much poorer in both suburbs relative to the level of knowledge and attitudes expressed. Anti-litter monitors are currently more effective for disseminating anti-littering information than changing actual practices. This study indicates that they are a progression from the traditional clean-up and/or education and awareness campaigns which have short-lived impacts in solid waste management in metropolitan areas of developing countries like Zimbabwe.

Pollution threatens fish health in the eutrophic lakes, Chivero and Manyame, in Zimbabwe. Histopathological tissue alterations of two commonly consumed fish: catfish, Clarias gariepinus, and; tilapia, Oreochromis niloticus, from Lakes Chivero and Manyame were assessed between 2015 and 2016. Seventy-one (71) catfish and 81 tilapia were caught using gill nets, and samples of their gills, liver, kidney and stomach tissue were collected and assessed microscopically for manifestations of disease. Pathologies observed in the gills of tilapia and catfish from both lakes included lamellar fusion, hyperplasia of primary lamellar epithelium and disintegration of secondary lamellar epithelium. Liver histopathology revealed vacuolation, presence of melanomacrophage centres and inflammatory cell infiltration in catfish and vacuolation in tilapia from both lakes. There were no significant differences (Chi-squared-test, p > 0.05) in the frequency of occurrence of some histological lesions in tissues assessed for the unrelated catfish and tilapia in the two lakes. Lamellar fusion in the gills conjoined neighbouring lamellae suggests the presence of parasites. Melanomacrophage centres observed in catfish may reflect metal pollution. Observed lesions in populations from both lakes suggest exposure to similar stressors and high tolerances and adaptation to eutrophic conditions. Keywords: biomarkers, fish histopathology, hydrobionts, peri-urban lakes, xenobiotics, Zimbabwe

Peri-urban fisheries- and fishing-dependent livelihoods face multiscalar threats of climate change, water pollution, transforming land initiatives and volatile markets. The objectives of this study were to assess the livelihood strategies and assets as well as the vulnerability of peri-urban fisherfolks in Lakes Chivero and Manyame, Zimbabwe. Furthermore, the study investigated the perceptions of fisherfolks towards climate change and its effects on their livelihoods. We employed a mix of qualitative and quantitative methods based on the livelihood indicator approach to assess climate risks and the associated vulnerabilities of peri-urban fisherfolks for the period November 2015–January 2017. Results indicate that the livelihood of the majority of fisherfolks (92.3% in Lake Manyame and 97.1% in Lake Chivero) is predominantly based on fishing and farming. More than 60% of the fisherfolks have attained formal education with some even attaining university education. Most (87%) peri-urban fisherfolks in the Lake Chivero and Manyame are aware of climate change and attest to its negative effects on their fishing-dependent livelihoods. Synergistic and multiplier relations between climatic and non-climatic factors such as water quality and quantity deterioration, obsolete fishing equipment and low working capital are key drivers of vulnerability. Economic diversification is the main adaptive strategy adopted by fisherfolks to reduce vulnerability. Non-significant differences in livelihood strategies, fisherfolk responses and perceptions towards climate change are attributed to the contiguity of the two lakes. Application and implementation of similar climate mitigation and adaptive strategies is a potential solution to reduce current and future vulnerability of fisherfolks in contiguous peri-urban lakes.

The following supplementary material is available for this article: Table S1. Location of the study sites in the Sanyati Basin of Lake Kariba, Zimbabwe. Table S2. Results of stable isotope analysis in R of the food source proportions in redclaw crayfish diet. This material is available as part of online article from: http://www.reabic.net/journals/bir/2018/Supplements/BIR_2018_Marufu_etal_SupplementaryTables.xlsx The diet of an invasive crayfish, Cherax quadricarinatus (Von Martens 1868), in Lake Kariba, was investigated using stomach content analysis (SCA) and stable isotope analysis (SIA). The frequency of occurrence of macrophytes and detritus ranged between 63.6–97.1% and 20–45.5%, respectively, and the index of relative importance ranked these as the two most important food items across all size classes. Significant differences in the ranking of fish, macroinvertebrates and crayfish were found between size classes 29–37.9, 38–46.9 and 47–55.9mm. Stomach content analysis showed 16% of crayfish stomachs were empty. Feeding intensity differed significantly between size classes and ranged from 3.46 to 5.21. Stable isotope analysis was done by comparing δ13C, δ15N and C/N ratios in crayfish muscle and potential dietary items in the lake. Macrophytes were the most dominant food item (57%), followed by macroinvertebrates (20%), then detritus, and finally fish and crayfish. Stable isotope analysis revealed that all crayfish size classes analysed were in the same trophic level. Nevertheless, while SCA showed high dietary overlap among all crayfish size classes (>65%), SIA showed that small crayfish (< 28.9mm) had limited overlap with large crayfish (> 56mm), with the former showing a higher proportion of macroinvertebrates in their diet. In Lake Kariba, C. quadricarinatus predominantly feeds on macrophytes, macroinvertebrates and detritus, which may bring about nutrient cycle alterations in the lake. Littoral habitat changes caused by the feeding characteristics of C. quadricarinatus might also lead to competition with, and eventual displacement of, some nativelittoral fishes in this lake. Research Council of Zimbabwe The University of Zimbabwe Vice Chancellor’s Data Collection Fund.

Pedestals or shoreline terraces, a disjuncture of the last flooding level with the adjacent littoral upland, can help in understanding the contribution of the shoreline to the productivity of the pelagic zones. We investigated littoral pedestal dynamics and assessed their ecological relevance to a water body, Manjirenji Dam in Zimbabwe, with marked and sharp drawdowns, in ten littoral sites by measuring chlorophyll a, water transparency, pedestal contour length and drawdown zone length once per month from August 2013 to April 2014. Chlorophyll a levels were not significantly correlated to the euphotic depth, pedestal contour length and the drawdown zone retraction length in Manjirenji Dam. Our results which are inconsistent with the hypothesis that drawdown zone and contour pedestal lengths are vital in predicting chlorophyll a concentration in the littoral zones of limnetic systems, suggest a need to explore other intricate limnological factors which may influence productivity in shallow reservoirs.

The aquatic environment is particularly vulnerable to the effects of contaminants as effluents from municipal and industrial wastewater continually add numerous harmful exogenous compounds. Lake Manyame is a peri-urban freshwater reservoir that is subject to municipal and industrial discharge as well as agricultural run-off. Adult Nile tilapia (Oreochromis niloticus) were sampled from L. Manyame during low-flow and high-flow seasons from selected locations. The samples were processed in the field for histology and biochemical analysis of selected biomarkers of oxidative stress. Induction of reduced glutathione (GSH), carboxylesterase (CES) and malondialdehyde (MDA) was evident at all the sites. There were no significant variations between sites except in the last low flow season and there was an upward trend between the first season and the subsequent sampling periods. Gonadal histology did not show occurrence of any intersex as a sign of endocrine disruption. The prevalence of histological lesions in the gonads was highest in the last sampling seasons, suggesting a progressive deterioration of water quality over time.

Metal concentrations in water, sediments and gills and edible stomach muscle tissues of two fish species, African Sharptooth mud catfish (Clarias gariepinus) and the Nile Tilapia (Oreochromis niloticus) in Eleyele Lake, Nigeria, were assessed in the rainy season (April), mid-dry spell time (July) and dry period (November) in 2017 to evaluate the potential ecological risks they pose to aquatic organisms. The concentrations of Fe, Co, Pb, Ni and Zn were significantly (p

Concentrations of aluminium, cadmium, chromium, cobalt, copper, iron, lead, nickel and zinc were determined in surface water, benthic sediments, and the gills, liver and stomach muscle tissues of Oreochromis niloticus and Clarias gariepinus in peri-urban lakes Chivero and Manyame, Zimbabwe. Five sites were sampled in each lake once per month in November 2015, February, May, August and November 2016. Pollution load index detected no metal contamination, whereas the geo-accumulation index reflected heavy to extreme sediment pollution, with Fe, Cd, Zn, Cr, Ni and Cu present in both lakes. Significant spatial temporal variations were detected for Al, Cr, Cu and Pb across sites within and between the two lakes. High Fe, Al and Cr concentrations in water and sediments in lakes Chivero and Manyame derive from geogenic background sources in addition to anthropogenic loads and intensity. Elevated concentrations of Al, Pb, Cu, Cd, Fe and Zn detected in gills, liver and stomach tissue of catfish corroborate concentrations in water and sediments, and pose the highest ecological and health risk for hydrobionts in lakes Chivero and Manyame. Contiguity of peri-urban lakes exposes them to similar threats, necessitating creative water management strategies, which ensure ecological continuity.Keywords: bio-accumulation, ecological risk, hydrobionts, lentic systems, toxicodynamics

Small aquatic ecosystems in semi-arid environments are characterised by strong seasonal water level fluctuations. In addition, land use as well as artificial pumping of groundwater to maintain water resources throughout the dry season may affect the functioning of aquatic ecosystems. In this study, we investigated pans situated in and around Hwange National Park, Zimbabwe, where certain waterholes are artificially maintained during the dry season for conservation purposes. We monitored 30 temporary and permanent waterholes for 7 months across the wet and dry seasons in 2013, and analysed them for standard parameters to investigate seasonal variations, assess the effects of land use and pumping on lake functioning, and determine the driving factors of these aquatic systems. Results show an increase in conductivity, hardness, and turbidity when temporary pans dry up and permanent ones are filled with groundwater. Prominent parameters explaining the diversity of aquatic ecosystems are water hardness, conductivity, turbidity, and the presence of vegetation. Seasonality differences in certain parameters suggest the influence of water level fluctuations associated with rainfall, evaporation, and pumping activities. Further, the distinction between turbid pans and those with clear water and vegetation suggests the alternative functioning of pans. Land use had no significant effects, while the effects of pumping are discussed. In times of water scarcity, animals gather around artificially maintained waterholes and foul water with faeces and urine, thus inducing water eutrophication. Keywords : eutrophication, water level fluctuation, organic matter inputs, groundwater pumping

This study investigates the concentration of metals namely aluminium, manganese and cobalt in two matrices: sediment and fish organs (whole muscle stomach tissue, gills, liver and kidney) in an urban river, Mukuvisi River, Zimbabwe. River bed sediments and fish samples were collected simultaneously at five sites over seven months (September 2008-April 2009). Concentrations of aluminium, manganese and cobalt in the selected fish organs and sediment were estimated using the Flame Atomic Absorption Spectrometry (FAAS). Water limnochemical aspects, dissolved oxygen, pH, temperature and conductivity were measured concomitantly at each site. Aluminium had significantly higher mean concentrations and bioconcentration factors in both sediments and fish tissues relative to cobalt and manganese. Cobalt and aluminium were detected in all fish tissues, whilst manganese was not detected in muscle and liver. Significant differences in bioconcentration factors for the metals in organs of the same fish species analysed in this study show differences in metal assimilation. Metal specific river rehabilitation methods need to be applied for the future restoration of the ecological integrity of Mukuvisi River.

Washbay effluents have received scant attention as a potential source of water pollution globally. This study is the first to investigate the potential impact of the total wash bay effluent content released into river water in Africa. We investigated the potential ramifications of wash bay effluxent released off Charter Estates, Chimanimani in the Eastern Highlands of Zimbabwe on the water quality of the receiving subtropical Nyahode River by measuring selected water limnochemical aspects which included biological oxygen demand (BOD), chemical oxygen demand (COD), oil and grease, pH, sulphates, phosphates, iron, total suspended solids (TSS), dissolved oxygen (DO) and electrical conductivity (EC) once every 3 months from October 2011 to July 2012. The obtained mean levels of the limnochemical parameters from the Nyahode River were compared to the local Environmental Management Agency (EMA) and international World Health Organisation (WHO) effluent standards. Our results show that the control point and the off effluent discharge source downstream points in the Nyahode River had water quality parameters that were below the local EMA and WHO water quality threshold values. Cluster analysis showed a strong linkage in the values of water quality parameters measured at sampling sites 3 and 4 which were below the discharge point. Wash bay effluent released from the Charter Estate has an impact on some aspects of the water in the Nyahode River but the river has a functional self-purification capacity. Onsite industrial purification of wash bay effluent before discharge reduces its potential deleterious impact on water quality, river habitat integrity and aquatic biodiversity.

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Inland fisheries provide income, food security and nutrition and act as a labour buffer. Yet they scarcely receive consideration in water resource allocation and economic decisions. Inland peri-urban fisheries face many challenges to their sustainability such as urban encroachment, environmental degradation and climate change. This study aimed to assess the historical fish catches, species composition, and investigate the effects of climatic variability and catchment dynamics in peri-urban Lakes Chivero and Manyame in Zimbabwe. The Mann-Kendall test was used to analyse time series trends in fisheries and climatic data. Multiple regression analysis was used to assess relations between fish catches and climate data for Lakes Chivero and Manyame. Fish catches have significantly declined in Lakes Chivero and Manyame over the periods considered with a shift towards a monospecies dominance in the fish community. Peri-urban lakes are characterised by highly adapted, relatively large sized fish species which have an ability to utilise a directional environmental disturbance such as hypereutrophication. Climatic factors have significant effects in fish catches in Lake Chivero. Despite the potential negative socioeconomic consequences inferred from declining fish catches, water pollution, gross underreporting, poor recording and preservation of fisheries statistics remains a massive threat to the survival of inland peri-urban fisheries in Lakes Chivero and Manyame.

Intermittent, dire droughts and water abstraction pressures impact shallow man-made reservoirs with multiple designated water uses, often leading to water quality deterioration, and loss of biological integrity and utility value of a lake, threatening the livelihoods of lake shore communities. Thus, water quality information is crucial in setting up guidelines for freshwater resources management. In this study we investigated the water quality, determined the trophic state and assessed the influence of lake zones on the physical-chemical parameters of the Manjirenji Dam, Zimbabwe. Furthermore, we tested the applicability of two customary temperate water quality indices, the Canadian Council of Ministers of the Environment (CCME) Water Quality Index and the Carlson Trophic State Index, for a tropical lake system. Ten littoral and seven pelagic sites were sampled monthly over 9 months for the following water parameters: pH, conductivity, turbidity, total dissolved solids, suspended solids, chlorophyll a , temperature, dissolved oxygen, water transparency, ammonia, nitrogen, nitrates, total and reactive phosphorus. Despite slight fluctuations/variations, water quality in the Manjirenji Dam was generally fair, with a CCME value averaging 78.1, and the Carlson Trophic State Index reflecting oligotrophy. Non-significant differences in water quality parameters between pelagic and littoral sites in the Manjirenji Dam reflect the high connectivity of different spatial zones in a shallow lentic system. Index scores of the adapted temperate water indices detect similar water quality conditions for the Manjirenji Dam, thus perhaps indicating their potential applicability. The current water quality data set for the Manjirenji Dam is vital for formulating prudent management strategies to formulate/ensure adequate multi-purpose water usage and service for this aquatic ecosystem. Keywords: ecotone, lake zones, water quality, trophic state, Manjirenji Dam

Aquaculture is an emerging reasonable answer to overexploitation of wild fish stock as the demand for wild fish stock is outstripping supply due to several geo-socio-economic reasons. However, productivity and profitability of aquaculture in Zimbabwe is affected by high costs of fish feeds. This study was done to compare and evaluate the effects of maize bran and chicken manure on growth of Oreochromis niloticus cultured in ponds at Lake Chivero. Three replicate spherical concrete ponds were each applied with chicken manure, maize bran and others left to be the control ponds. A complete randomized experimental design was used. Fish sampled from maize bran fed ponds had the highest growth rate, followed by fish fed with chicken manure ponds and, the control ponds respectively. The use of locally available waste products and feed materials in can be useful in the profitability of O. niloticus culture locally as cereal bran such as maize bran is generally cheap and chicken manure are readily available in Zimbabwe. Further studies should be undertaken on how maize and chicken manure should be applied with proper feeding regimes and ratios to stimulate algae production as well as to prevent fish mortality.

This research is a snapshot survey of the fish species fauna in a tropical lake, Lake Sebakwe, in Zimbabwe. This is the first record of the fish species present in the lake which was built to provide irrigation water and for recreational purposes. Continuous intensive gill and seine fishing was done over five days in the lake and 8 fish species were collected. The exotic Northern largemouth bass ( Micropterus salmoides Lacepede, 1802)dominates the system. It appears the fish we sampled favour clear still waters which can act as a pointer to the water quality of the lake.

The aim of this study was to establish the level of water quality impairment along a mine effluent receiving river, Pote River in Zimbabwe, using Oreochromis niloticus (Nile tilapia) as an indicator organism. Glutathione-S-transferase (GST) enzyme and heat shock protein (HSP 70) expression in the stomach tissue of Nile tilapia were used as biomarkers of heavy metal pollution. Water and fish samples were collected at three sites in the Pote River. Metal concentration in tilapia tissues and water were measured using flame acetylene absorption spectrophotometry while enzymatic activity was determined using ultra-violet spectrophotometry. The concentration of Ni and Zn in water was significantly high compared to the World Health Organization aquatic effluent standards. Cd and Zn were strongly associated with high GST activity and low HSP 70 protein concentrations in fish tissues. Results of this study show that HSP 70 protein and GST enzyme activity can be useful biomarkers of metal contamination in lotic systems. Keywords : enzymes, biomarkers, heavy metals, Nile tilapia, bioassessment, Pote River

Intermetallic correlation and the ameliorative effects of metals (Cd, Cr, Cu, Fe, Ni, Pb and Zn) were determined in water and sediments in the Gwebi River, a major tributary to Lake Manyame, which is a source of potable water to the City of Harare. Water and sediment were sampled at four selected sites in the wet (December- March) and dry (April-November) seasons and metal concentrations were analysed by flame atomic absorption spectroscopy (FAAS). Significantly high concentrations of zinc and copper were observed in water in both the wet and dry season. Concentrations of chromium, copper, zinc iron and nickel in water in both the wet and dry seasons surpassed World Health Organization (WHO) thresholds. The significant difference (ANOVA, p < 0.05) in seasonal/temporal variation in metal concentrations in water indicate different pollutant sources within the catchment of the river. Ameliorative effects of metals were also observed seasonally in the Gwebi River, with Fe and Zn playing a prominent role in both sediment and water phases.

Condition factor, sexual maturity and length-weight relationship of 1132 Oreochromis niloticusinhabiting the hypereutrophic Lake Chivero in Zimbabwe were studied. Fish samples were collected through gill netting and from selected commercialfisheries around the lake from February - November 2011. Comparative analysis of age and size at maturity revealed that the O. niloticus reached maturity at 30±2.5 mm males and 50±3.6 mm females in total length. There was a significant difference in sexual maturity in both sexes with the inactive (I) stage more frequent. Both sexes of fish indicated a negative allometric increase in weight.August and November were determined as the most intensive and sensitive breeding periods for O. niloticus in Lake Chivero.Fishing activities in the lake need to be regulated in tandem with the breeding cycles of the O. niloticus.

Ecological integrity of a peri-urban river system facing a plethora of anthropogenic pressures was assessed through multivariate analysis of physicochemical parameters correlated to the resident macroinvertebrate community. Monthly collection of macroinvertebrates and concurrent measurement of the physical and chemical parameters (dissolved oxygen concentration, percentage saturation of oxygen, pH, temperature, electrical conductivity and salinity) of water was done over a period of 5 months from November 2011- March 2012 in six sites across the Chiraura River. Macroinvertebrates were collected using the kick-net sampling technique, identified up to family level and enumerated at each site. Biodiversity indices were calculated for each site following the South African Scoring System version 5 (SASS5). A total of 1209 macroinvertebrates belonging to 49 families and11 orders were recorded in the Chiraura River. Most pollution sensitive taxa were found at sites 3 and 4 and the most pollution tolerant families were found at sites 1, 5 and 6. Sites4 and 5 of Chiraura River were the least polluted. Unsustainable anthropogenic activities, including industrial, domestic and urban agricultural activities affects water quality of Chiraura River. This is mainly through run-off and increased effluent to the river making routine water quality monitoring imperative.