Characterization of Oreochromis niloticus Strains of Lake Kariba Culture Fisheries using Morphological and Meristic Methods

Oreochromis niloticus fish collected from Yalelo Fishery, Fwanyanga Fishery and Choombwe Fishery of Lake Kariba were investigated by multivariate analysis of 23 morphometric measurements and 7 meristic counts. Dendrograms were used to delineate the sampled specimens using PC-ORDTM Software and the differences among strains were tested using One-way ANOVA in Statistix 9 Software (P = 0.05). Meristic analysis did not show a high divergence among the strains while morphometric analysis showed that the sampled fish could be characterized into three different strains. These results showed that the tested fish samples could be grouped into 3 types based on morphometric characters. The morphometric differences among the sampled O. niloticus strains may have appeared due to genetic differences among the collected specimens

Interactions Between Humans, Crocodiles, and Hippos at Lake Kariba, Zimbabwe

Human–wildlife conflicts (HWCs) are on the increase due to shrinking space that results in increased competition for land, water, and other natural resources between humans and wildlife. Investigating the occurrence of HWCs is important in that the results can be used to formulate better management policies and strategies. In this paper, we describe the nature of HWCs emerging between humans and the Nile crocodile (Crocodylus niloticus) and between humans and the African hippopotamus (Hippopotamus amphibius; hippo) on Lake Kariba, Zimbabwe. Lake Kariba is the second largest manmade lake by volume in the world. Conflicts involving humans and these species are readily noticeable and played out around water bodies, which are sources of daily human sustenance and important habitats for aquatic wildlife. We used a mixed-methods approach to gather data on these conflicts, including questionnaires, face-to-face interviews, focus group discussions, and participant observation. The research participants involved national parks officials, fishing camp residents, and HWC victims. Our research confirmed that crocodiles and hippos have negatively affected humans through deaths, injuries, instilling fear, and destruction of sources of livelihood for fishermen such as fishing nets and boats. In retaliation, humans have implemented lethal methods to remove problem animals. The results of this research can inform the conservation community about the severity of the conflicts, which have been exacerbated by current economic hardships, to better inform conservation policies

Reproduction performance of female Nile tilapia (Oreochromis niloticus) fed on diets made using caterpillar meal (Imbrasia truncata) as replacement of fish meal

The study determined the effects of caterpillar meal as a replacement of fish meal on reproduction performance of Nile tilapia (Oreochromis niloticus) broodstock. Three diets containing different percentages of caterpillar meal were fed to O. niloticus. The first diet (T0) contained 0% caterpillar meal, the second diet (T1) contained 15% caterpillar meal and the third diet (T2) contained 30% caterpillar meal. The diets were fed to duplicate groups of brood fish (average weight of 78.3 ± 6.5 g for males and 39.8 ± 8.17 g for females). Each group consisted of six females and two males stocked into a hapa and fed twice a day at 3% of their body weight for 96 days. There were no significant differences (p > 0.05) among the experimental diets with respect to Specific Growth Rates (SGR) but the difference was significant (p < 0.05) between diets T0 and the two other diets on the Survival Rate (SR). No significant differences were found between diets T0 and T1 on total % of spawning per diet. Inter-spawning intervals (ISI) showed irregular patterns in relation to diet (p < 0.05) between diets T0 and T1, but with diet T0, the females tended to spawn at shorter intervals. However for diet T2, the period before first spawning was significantly longer than that of diets T0 and T1. Mean gonadosomatic index (GSI) was lower in fish fed with diet T2 than those fed with diets T0 and T1. Diets T0 and T1 recorded the highest GSI with no difference between diets. The body composition of broodstock was not significantly affected by the changes in diets. These results revealed that the replacement of fish meal by caterpillar meal at 15% can lead to better reproduction performance on Nile tilapia broodstock reared in hapas. It was therefore recommended that diet T1 be used in feeding broodstock of Nile tilapia O. niloticus. Keywords: Reproduction performance, Oreochromis niloticus, caterpillar mea

Aspects of the population biology, life history and threats to Aloe ortholopha Christian and Milne-Redh.: A serpentine endemic from the northern Great Dyke of Zimbabwe

Background: Aloe ortholopha is a rare endemic confined to serpentine soils of the Great Dyke of Zimbabwe. Its International Union for Conservation of Nature (IUCN) status is listed as Vulnerable; however, its population biology and life history are poorly documented. Objectives: The aim of this article is to provide information on the population biology and life history of A. ortholopha through assessment of its size-class distribution, population size and density, reproductive output and fitness, and threats related to fire and mining. Method: Circumference of A. ortholopha leaf rosette was used to ascertain size-class distribution. Population size and density were determined by enumerating flowering individuals. Per-capita reproductive output was determined as mean number of flowers per plant, fruit set and mean number of seeds per fruit. Fitness was determined from seed germination capacity. Impact of fire and mining were recorded photographically. Results: Determination of size-class distribution of A. ortholopha from three study sites (southern region [SR], central region [CR] and northern region [NR]) revealed a bell-shaped curve dominated by intermediate size classes. Population size (number of flowering individuals) ranged from 36 to 66 per site. This translated to a density of 4.0–7.3 flowering plants per hectare. Per-capita reproductive output, measured as mean number of flowers per plant, was significantly different in SR and CR compared to that in the NR region. Mean number of fruits per plant did not significantly differ across the three regions. Mean seed set per plant in CR and NR was significantly different to that in the SR region. Species fitness, as determined from in vitro germination assays, showed that seeds harvested from fire-damaged capsules have the lowest cumulative germination percentage. It was also observed that leaf rosettes curled up to form a ball that protects the apical centre of plants from fire damage. Conclusion: A. ortholopha occurs in small population clusters of low density. The species has a low per-capita reproductive output characterised by production of many flowers, but with very low percentage fruit and seed set. The species has low fitness as evidenced by nominal recruitment of saplings and juveniles. Conspecific mates are frequently lost owing to fire and mining activities

Current status of aquaculture in Kisangani region, Democratic Republic of the Congo: Constraints and opportunities

This study was carried out in Kisangani region, located in the north-east of the country. Surveys were carried out with farmers and observations were made on the nature of any aquaculture operations. Only fish farmers with a minimum of 100 m2 ponds surface area were assessed in detail in this study. It was quite an unexpected to discover that many farmers have maintained the aquaculture tradition in this region. Within an area from 18 km radius of Kisangani town, a total of 45 fish farmers were interviewed. In Kisangani region, 44 % of fish farmers have up to 15 years experience but only about 7 % have farmed fish for 25-35 years. About 90 % of the interviewed fish farmers were not members of any fish farmers’ association. The fish farmers in this region practice mainly polyculture. The most commonly cultivated fish species was Orechromis niloticus, followed by Clarias gariepinus and then Parachanna obsura. There is no commercially produced fish feed in the market and hence the feeding of the fish remains traditional. Most of the farmers (64 %) used rice bran; 42 % use pig waste; 78 % farmers used household wastes and about 22 % of the fish farmers do not feed the fish. The average fish production is 11.4 kg per 100 m2 while the lowest and highest production was respectively 4.0 kg/100 m2 and 29.5 kg/100m2. Fish is sold without post-harvest processing in lots or singles depending on fish size. In conclusion, Kisangani region’s aquaculture is operating at a very basic level. However, fish farming culture is better established here compared to other sub-Saharan countries. The growth of the sector is being currently hampered by limited technology, inadequate training, lack of feeds and overall lack of support for fish farmers. There is great aquaculture potential as all the climatic attributes of the region are ideal for aquaculture

Collaboration and infrastructure is needed to develop an African perspective on micro(nano)plastic pollution

Abstract: Our current understanding of environmental micro(nano)plastic (MNP) pollution is driven by field and lab-based studies performed predominantly by and in wealthier countries. However, mismanaged waste and its consequences affect low- and middle-income countries over-proportionately. Evidence suggests that studies on MNP pollution in Africa are critically limited by the scientific infrastructure available, restricting research activities to opportunities for external collaboration with established research laboratories in the Global North. The development of Pan-African research networks and analytical nodes, is required to support intra-African research exchange and training, and drive evidence-based policy relevant to an African context. This can facilitate more inclusive conversations around the harmonization and standardization of methods currently mainly available to the Global North

État actuel de l'aquaculture dans la région de Kisangani, en République démocratique du Congo: Contraintes et opportunités

This study was carried out in Kisangani region, located in the north-east of the country. Surveys were carried out with farmers and observations were made on the nature of any aquaculture operations. Only fish farmers with a minimum of 100 m2 ponds surface area were assessed in detail in this study. It was quite an unexpected to discover that many farmers have maintained the aquaculture tradition in this region. Within an area from 18 km radius of Kisangani town, a total of 45 fish farmers were interviewed. In Kisangani region, 44 % of fish farmers have up to 15 years experience but only about 7 % have farmed fish for 25-35 years. About 90 % of the interviewed fish farmers were not members of any fish farmers’ association. The fish farmers in this region practice mainly polyculture. The most commonly cultivated fish species was Orechromis niloticus, followed by Clarias gariepinus and then Parachanna obsura. There is no commercially produced fish feed in the market and hence the feeding of the fish remains traditional. Most of the farmers (64 %) used rice bran; 42 % use pig waste; 78 % farmers used household wastes and about 22 % of the fish farmers do not feed the fish. The average fish production is 11.4 kg per 100 m2 while the lowest and highest production was respectively 4.0 kg/100 m2 and 29.5 kg/100m2. Fish is sold without post-harvest processing in lots or singles depending on fish size. In conclusion, Kisangani region’s aquaculture is operating at a very basic level. However, fish farming culture is better established here compared to other sub-Saharan countries. The growth of the sector is being currently hampered by limited technology, inadequate training, lack of feeds and overall lack of support for fish farmers. There is great aquaculture potential as all the climatic attributes of the region are ideal for aquaculture. Keywords: Aquaculture, Kisangani region, ponds, feeding.Cette étude a été réalisée dans la région de Kisangani, située au nord-est du pays. Des enquêtes ont été menées auprès des pisciculteurs qui ont été interrogés et des observations ont permis de constater l’état des exploitations aquacoles. Dans cette étude, seuls les pisciculteurs possédant au minimum 100 m2 d’étangs ont été enquêté. Il était assez inattendu de découvrir que de nombreux pisciculteurs ont maintenu la tradition aquacole dans cette région. Dans un rayon de 18 km de la ville de Kisangani, 45 pisciculteurs ont été interrogés. Dans la région de Kisangani, 44 % des pisciculteurs ont jusqu’à 15 ans d’expérience, mais seulement 7 % ont 25 à 35 ans d’expérience en pisciculture. Environ 90 % des pisciculteurs interrogés ne sont membres d’aucune association piscicole. Les pisciculteurs de cette région pratiquent principalement la polyculture. L’espèce la plus cultivée est Orechromis niloticus, suivie de Clarias gariepinus et de Parachanna obsura. Il n’existe pas d’aliments élaborés pour poissons sur le marché de Kisangani et de ce fait l’alimentation du poisson reste très basique. La plupart des pisciculteurs (64 %) utilisent du son de riz; 42 % utilisent les déjections de porc; 78% utilisent les déchets ménagers et environ 22 % n’alimentent pas les poissons. La production moyenne est de 11,4 Kg/100 m2 tandis que la production la plus faible et la plus élevée étaient respectivement de 4,0 Kg et 29,5 Kg/100 m2. Les poissons sont vendus sans aucune transformation après la récolte en lots ou par pièce selon leur taille. En conclusion, l’aquaculture dans la région de Kisangani fonctionne à un niveau très traditionnel. Cependant, la culture de la pisciculture y est mieux établie que dans d’autres pays d’Afrique subsaharienne. La croissance du secteur est actuellement entravée par des technologies limitées, une formation insuffisante, le manque d’aliments pour poissons et le manque général de soutien pour les pisciculteurs. Le potentiel aquacole est important car tous les atouts climatiques de la région sont propices pour l’aquaculture. Mots-clés: Aquaculture, région de Kisangani, étangs, alimentation

The Limnology and Ecology of Two Small Man-Made Reservoirs in Zimbabwe.

This study investigated the limnology of two small dams (< 5ha) built in series on Munwahuku river. Very little is known about the ecology of such small water bodies and the hydrological regime of these dams is that they undergo severe fluctuations in water levels. Rainfall is seasonal but water demand for irrigation and potable water persist throughout the year. The theoretical mean water residence time was 9 days for the Upper dam and 3.6 days for the Lower one while the water level in the Upper dam fluctuated more than the Lower one. Thermal stratification established during summer in the dams but was weak during winter. Stratification was poorly established during the main rainy season (Jan-April) and this could be the result of throughflows causing disruptions. Oxygen stratification patterns were similar to those of temperature and deoxygenation sometimes occurred in summer. Seasonal trends were related to changes in solar radiation income and the corresponding changes in air temperatures. The Lower dam was less stable during summer than the Upper one and this could largely be a result of short water residence time which influenced development of thermal stratification. Diurnal stratification of temperature and oxygen occurred in both dams during summer but was less established in winter. The shallow nature of small dams suggests that they are more vulnerable to external fluxes such daily changes in temperature, wind runs and any other disturbances and hence the prevalence of diel stratification because of low stability. The water and aspects of sediment chemistry of the dams was investigated in relation to influence of the hydrological regime. The two small dams were not significantly different in water chemistry but their sediment chemistry showed some differences. Seasonal fluctuations in conductivity, TDS, TSS and Secchi disc transparency were strongly linked to the hydrological regime to the effects of the first rains while increases in BOD and COD suggested increased organic matter at low water levels. There were no dramatic seasonal variations in pH, alkalinity, nitrate, nitrite, ammonia and total nitrogen although the latter tended to be higher in the Upper dam. Short water residence time was attributed as the main factor resulting in small differences in the water quality of the two dams. In the Upper dam, sediment silt content was higher in the drawdown zone while clay was significantly higher in the permanently inundated zone. There were no major seasonal variations in nitrogen, phosphorus and carbon content in the zones but their values were consistently higher in the deeper zone. In contrast, clay, nitrogen, phosphorus and carbon content were significantly different between the two zones in the Lower dam and were higher in the drawdown zone except clay. The community structure of zooplankton and phytoplankton populations was studied. Zooplankton abundance was not very different between the two dams with peaks during the late dry season attributed to a sudden abundance of rotifers. A similar pattern was observed for phytoplankton abundance and biomass with peaks around October 2000 but generally higher abundance was measured in the bottom dam. There was a complete shift in the dominant zooplankton and phytoplankton taxa in both dams after October 2000. A major factor influencing plankton abundance was washout during the main rainy season whilst water transparency, suspended solids, water temperature were factors identified by CCA analysis as important for zooplankton community structure in both dams. CCA analysis revealed that physico-chemical variables were not significant in determining phytoplankton communities in both dams perhaps superseded by hydrological processes. The effects of grazing on phytoplankton by zooplankton and predation on zooplankton by fish were not assessed but could be factors influencing community dynamics. Six fish species were caught in both dams during the entire sampling. The dominant species numerically was B. paludinosus and C. gariepinus in either dam but C. gariepinus contributed the greatest proportion of the total catch weight at most times. The cyprinids B. lineomaculatus and B. trimaculatus were caught in small numbers and so were the cichlids, O. mossambicus and T. sparrmanii. This species composition is perhaps largely determined by the fish community in the river and the shallow nature and frequent fluctuations in water level do not allow for specialized habitats to develop in small dams hence promoting diversity. Water retention is very short in these dams and so they could be little difference with the main river. The highest proportion of breeding B. paludinosus was during the rainy season and consequently relative fecundity was highest at that time. Migration, spawning events and recruitment events were not easily discernable in the fish populations of either dam. The high turbidity when water levels were low did not appear to have adverse effects on the fish community in either dam

Growth, Mortality and Exploitation of Nile tilapia, Oreochromis niloticus (L.) in Lake Chivero, Zimbabwe and Implications on the Management of the Artisanal Fishery

Age and growth of Nile tilapia, Oreochromis niloticus (L.) were determined using sample from Lake Chivero (Zimbabwe) caught from 2009 to 2011. The length-weight relationship for all individuals was W = 0.015 TL0.304. The sex ratio of female to male was 1:1.27. Fish age derived from both length frequencies and scales showed no significant difference (p &gt; 0.05, Paired T-test). The length frequency age data were used to estimate the growth parameters of the von Bertalanffy equation. The mean values from 2009 to 2011 were: L∞ 39.41, K = 0.41, (ø) = 2.798, Lm50 = 23.33 cm, Lc50 = 22.60 cm, Z = 1.84 year-1, M= 0.81 year-1, F = 1.04 year-1 and E = 0.58 year-1. Growth, mortality and exploitation parameters L∞, K, (ø) and Z were compared from year to year and results showed the fishery is over-exploited. Fish below age/length at first maturity form the bulk of the fish harvested by the fishery. Increasing length at first capture could increase yield per recruit and also protect spawning stock. Other implications on the management of the fishery are discussed.Keywords: Exploitation, Fisheries, Growth, Management, Mortality, Nile tilapi

Remote sensing of nutrients in a subtropical African reservoir: testing utility of Landsat 8

Remote sensing is useful for water quality assessments but current remote sensing applications favour parameters that are easy to detect such as chlorophyll-a. An assessment of the utility of Landsat 8 for detecting nutrients was conducted in Mazvikadei reservoir in Zimbabwe. The main objective was to determine whether nutrients often overlooked by remote sensing and yet are the main determinants of water quality can be remotely sensed. Sampling targeted ammonia, nitrates and reactive phosphorus from May to October 2015. In situ nutrient concentrations were regressed against reflectance derived from Landsat 8 imagery. Strong negative relationships were found between ammonia and the near-infrared band in July (R2 = 0.80, p < 0.05) as well as between nitrates and the blue band (R2 = 0.67, p < 0.05) in June. Overall, the results suggest that the cool dry season is the optimum time to use Landsat 8 for monitoring nutrients in tropical lakes