Koka Reservoir Research Articles

Evaluating the impact of land use and land cover changes on sediment yield dynamics in the upper Awash basin, Ethiopia the case of Koka reservoir

Land Use and Land Cover changes (LULC) are the driving forces to change the hydrological response of the watershed. In this study, the Quantum Geography Information System Interference Soil and Water Assessment Tool Plus (QSWAT-PLUS) model was applied to evaluate the effects of LULC on sediment load at the Upper Awash River Basin (UARB) which are causing sedimentation problems in Koka reservoir. The LULC data for 2005, 2010, and 2015 were obtained from historical satellite images using Earth Resources Observation and Science (ERDAS) 2014. The classification of LULC changes showed that the agricultural practice, and the settlement land both increased by 6.7 % and 6.3 %, respectively. In contrast, the forest area, woodland, shrubland, and water bodies decreased by 5.47 %,0.93 %,0.96 %, and 1.34 % from 2000 to 2015 respectively. The model evaluation results were satisfactory for the three LULC scenarios. The average annual surface runoff volume for the 2005 LULC data was 182.2 mm, which increased to 193.29 mm in 2010 and 205.3 mm in 2015. Similarly, the average annual sediment yield that would enter to the Koka reservoir under the 2005, 2010, and 2015 LULC scenarios were 26.03 t/ha/yr, 26.34 t/ha/yr, and 28.33 t/ha/yr respectively. In general, streamflow, surface runoff, and sediment output increased by 4.55 %, 12.68 %, and 8.84 %, respectively due to the rapid change of LULC from 2000 to 2015. Temporarily, the sediment load at the upstream side of the Koka Dam watershed was 60.8 % during the wet season. The southwest direction of the watershed was identified as the primary erosion-prone area. Based on the simulation results, the filter strip, contour, and terraces reduced the watershed sediment yield by up to 60 %, 65 %, and 80 %, respectively. Therefore, the selected best management practices are highly effective in reducing silt along the entire upstream side of the Koka Dam watershed.

Investigation of climate change impact on the optimal operation of koka reservoir, upper awash watershed, Ethiopia

The objectives of this study were to predict the inflow and optimal operation of the Koka reservoir under the impact of climate change for the 2020s (2011–2040), 2050s (2041–2070), and 2080s (2071–2100) with respect to the reference period (1981–2010). The optimal elevation, storage, and hydropower capacity were modeled using the HEC-ResPRM, whereas the inflow to Koka reservoir was simulated using the calibrated SWAT model. Based on the result, the average annual inflow of the reference period was 139.675 Million Cubic Meter (MCM). However, from 2011 to 2100 an increase of +4.179% to +11.694 is expected. The inflow analysis at different flow regimes shows that the high flow may decline by (−28.528%) to (−22.856%) due to climate change. On the other hand, the low flow is projected to increase by (+78.407%) to (+90.401%) as compared to the low flow of the reference period. Therefore, the impact of climate change on the inflow to the Koka reservoir is positive. The study also indicates that the optimum values of elevation and storage capacity of the Koka reservoir during the reference period were 1590.771 m above mean sea level (a.m.s.l) and 1860.818 MCM, respectively. However, the optimum level and storage capacity are expected to change by (−0.016%) to (−0.039%) and (−2.677%) to (+6.164%), respectively from 2020s to 2080s as compared with their corresponding values during the reference period. On the other hand, the optimum power capacity during the reference period was 16.489 MCM, while it will likely fluctuates between (−0.948%) - (+0.386%) in the face of climate change. The study shows that the optimum elevation, storage, and power capacity were all higher than the corresponding observed values. However, the occurrence month of their peak value will likely shift due to climate change. The study can be used as a first-hand information for the development of reservoir operation guidelines that can account for the uncertainty caused by the impacts of climate change.

Spatiotemporal Dynamics of Water Quality Indicators in Koka Reservoir, Ethiopia

The science and application of the Earth observation system are receiving growing traction and wider application, and the scope is becoming wider and better owing to the availability of the higher resolution of satellite remote sensing products. A water quality monitoring model was developed using Sentinel-2 satellite remote sensing data set to investigate the spatiotemporal dynamics of water quality indicators at Koka Reservoir. L1C images were processed with an Atmospheric correction processor ACOLITE. The months from June 2021 to May 2022 and the years 2017 to 2022 were used for the temporal analyses. Algorithms were developed by using regression analysis and developing empirical models by correlating satellite reflectance data with in situ Chlorophyll-a (Chl-a), turbidity (TU), and Total suspended matter (TSS) measurements. All of the analyzed parameters have determination coefficients (R2) greater than 0.67, indicating that they can be turned into predictive models. R2 for the developed algorithms were 0.91, 0.92, and 0.67, indicating that good correlations have been found between field-based and estimated Chl-a, TU, and TSS, respectively. Accordingly, the mean monthly Chl-a, TU, and TSS levels have ranged from (59.69 to 144.25 g/L), (79.67 to 115.39 NTU), and (38.46 to 368.97 mg/L), respectively. The annual mean Chl-a, TU, and TSS vary from (52.86–96.19 µg/L), (71.04–83 NTU), and (36.58–159.26 mg/L), respectively, showing that the reservoir has been continuously polluted over the last seven years. The spatial study found that the distributions of Chl-a, TU, and TSS were heterogeneous, with Chl-a being greater in the south and southwest, and TU and TSS being higher on the western shore of the reservoir. In conclusion, these results show that there are spatial as well as temporal variations on water quality parameters. The proposed algorithms are capable of detecting optically active water quality indicators and can be applied in similar environmental situations.

Age and Growth of Nile Tilapia, Oreochromis niloticus (Linnaeus, 1758), From Koka Reservoir, Ethiopia

The age and growth rate of the fish species must be known since they are essential input variables that compose stock assessment models to assess the stock status and estimate the exploitable potential of the stock. The age and growth of Nile tilapia, Oreochromis niloticus (Linnaeus, 1758), in Koka Reservoir, Ethiopia, were studied based on 981 sagittal otoliths collected monthly from December 2017 to November 2018. Otoliths were grounded and examined under a stereoscopic microscope at 10–40× magnification for macrozones analysis using a reflected light source. The age of the fish was determined based on the number of translucent zones counted in the otoliths of O. niloticus by considering the time of translucent zone formation and median hatch date. Seasonal records on the macrozones at the edge of otoliths and relative marginal increments suggested that two translucent macrozones associated with biannuli were formed each year, one from January to February, and another one from June to July. The observed ages of O. niloticus from Koka Reservoir ranged from 1 to 6.5 years, and the most dominant classes were 2 and 3 years. Growth was determined using the von Bertalanffy growth function. The von Bertalanffy growth parameters (sexes combined) were; asymptotic length (total length), L∞ = 35.6 cm, growth rate constant, K = 0.37 year-1, theoretical age at zero-length, t0 = -0.42 years and the growth performance length, φ’ = 2.67. It could be concluded that the growth of O. niloticus in Koka Reservoir is within the range mentioned in Ethiopian lakes.

Limnological responses of a shallow tropical reservoir to recent incidence of hydro-climatic anomaly suggest potential challenges of future restoration efforts.

The impact of El Niño-induced drought (2015/2016) on the limnology of Koka Reservoir was studied through a 1-year sampling with emphasis on nutrient concentration. The monthly concentration of riverine input of TP varied between 400 and 2872 mg/m3, with a total annual load to the reservoir of 482012 × 106 mg. This resulted in annual areal load to the reservoir of 2410 mg/m2. The mean annual in lake concentration of total phosphorus as predicted by the trophic state model specifically developed for warm tropical water bodies by Salas and Martino in 1991 was 146.6 mg/m3. This is only 24% of the observed concentration of 609 mg/m3 suggesting that internal recycling is sufficient to supply much of the phosphorus that sustain cyanobacterial growth. Koka Reservoir is a highly productive water body exhibiting a thick recurrent cyanobacterial bloom exclusively dominated by Microcystis spp. Mineralization of the Microcystis-bound phosphorus could be the major mechanism of phosphorus recycling following the collapse of the bloom. High water temperature and frequent mixing may have promoted this mechanism of phosphorus recycling from autochthonous sources. In our related study, we also reported the emergence and unusual dominance of diazotrophic cyanobacteria following the climate anomaly and the consequent severe nitrogen limitation. The emergence of cyanobacteria that can fulfill their nitrogen requirement from the atmospheric nitrogen (N2) and the possibility of large phosphorus reserve in the sediment could make future restoration efforts very challenging.

Water hyacinth (Eichhornia crassipes) affects the composition and abundance of zooplankton in the littoral region of Koka Reservoir, Ethiopia

Water hyacinth, Eichhornia crassipes (Martius) Solms 1883, is a rampant invasive aquatic plant that is recognised as one of the ten worst weeds in the world. Its appearance in Koka Reservoir was reported in 1965 and since then it has become a major threat to the aquatic ecosystem. Despite numerous limnological studies on Koka Reservoir, the effects of water hyacinth on zooplankton has not been addressed previously. To assess this, samples were collected from three weed-infested and three non-infested sites from March to July 2018. The zooplankton community living, which was constituted of 38 species, was dominated by Rotifers, followed by copepods and cladocerans at both sites. The variations in the abundance of zooplankton and species richness (d) between the two sites were significant with higher mean values in the non-infested sites (p < 0.05). The existing infestation level of water hyacinth poses a significant effect on the composition and abundance of zooplankton. Therefore, continuous follow-up, such as physical removal of the weed and constructing buffer zone and designing sustainable management strategies, have to be addressed.

Effects of Water Hyacinth on Fishery Resource and Its Expansion Trends in Ethiopian Water Bodies: A Review

Ethiopia is gifted with a variety of aquatic ecosystems. Aquatic ecosystems are often viewed as highly productive biological systems. At present Water hyacinth ( Eichhornia crassipses ) have been ranked as one of the world’s worst invasive weeds causing problems to millions of users of water resources. The water hyacinth appeared in Ethiopia in 1965 at the Koka Reservoir and in the Awash River. Other infestations in the country include Gambela Region, the Blue Nile from just below Lake Tana into Sudan, Lake Ellen near Alem Tena and currently expanding to almost rift valley lakes. Assessment 2014 study shows that close to one-third or more than 30% of the shoreline of the north-eastern part of the Lake’s shore is now invaded by water hyacinth. Under favorable conditions water hyacinth can double its mass every 5 days and it also grows from seed which can remain viable for 20 years or longer. Water hyacinth can also greatly affect fish catch rates, because mats of water hyacinth can block access to fishing grounds and clog eye of the net. Water hyacinth reduces fish stock for Tilapia and young Nile Perch by limiting access to breeding, nursing, and feeding grounds. Water hyacinth affects fish catchability especially when dissolved oxygen is reduced as a result of dense water hyacinth mats, this risk killing the fish. Access to sites becomes difficult when weed infestation is present, loss of fishing equipment. Further expansion of this plant will lead to drying up and shrinking of the lake. Depending on the degree of evapo-transpiration and the lake size, there would be completely dry-up and disappearance of the Lakes. As control measure several methods biological, physical chemical and integrated control approaches are under taken. Keywords: Water hyacinth, Fishery, Expansion trends, Water bodies DOI: 10.7176/JNSR/10-11-04 Publication date: June 30th 2020

The overriding role of hydrological factors on zooplankton community: evidence from a shallow tropical reservoir (Koka, Ethiopia).

Due to changes in global climate and local hydrological variability, land-water interactions are considered the prevailing processes underpinning aquatic ecology. Periodic meteorological conditions could have significant effect upon freshwater plankton communities by modifying the relative influences of biotic and abiotic structuring factors. However, the influence of unusual meteorological events, such as the El-Niño Southern Oscillation cycles, and advection on zooplankton communities of tropical shallow lakes and reservoirs are not fully understood. The present study, therefore, aimed to explore the relationship between hydrological factors and zooplankton community structure in Koka Reservoir, Ethiopia. Field measurements and collection of water samples and zooplankton were performed at monthly intervals from January to August 2016 at three sampling sites along a stretch of the reservoir from the river mouth to the center and the outlet (dam). The results showed post-El-Niño hydrological events (i.e., elevated riverine runoff and higher levels of turbidity) and associated advective losses can disrupt zooplankton community structure at the river mouth site, particularly during the rainy period. The results suggest that integrated watershed management activities are important aquatic resource management options in small- and medium-sized lakes and reservoirs.

Partitioning the influence of hydrodynamics-induced physical variables and nutrients on phytoplankton assemblages in a shallow tropical reservoir (Koka, Ethiopia)

Ecological processes, population dynamics and species interactions in shallow lakes and reservoirs are affected by seasonal and inter-annual fluctuations in rainfall and runoff. The present study aimed to explore the relationship between riverine runoff and phytoplankton community structure in Koka Reservoir, Ethiopia. Onsite measurements and collection of water samples and phytoplankton were performed at monthly intervals from January to August 2016 at three sampling sites along a stretch of the reservoir running from the river mouth to center and the outlet (dam). The results showed the decline in phytoplankton biomass at the river mouth site. The decline was particularly noticeable during the period of high rainfall and runoff compared to that of the low water period. This was associated with the hydrodynamics-induced high turbidity and reduced euphotic depth. Our results implied that phytoplankton community structure was strongly influenced by flood pulse. The results suggest that river flow and watershed management have the potential to be used more widely as an aquatic resources management option in small and medium-sized lakes and reservoirs.

Temporal dynamics of intra-and extra-cellular microcystins concentrations in Koka reservoir (Ethiopia): Implications for public health risk

This study was carried out with a view of understanding the temporal dynamics of microcystin concentrations in both algal seston and water samples and the associated public health risk. All the major MC variants, namely MC-LR, MC-YR, and MC-RR, were detected in both the algal seston and water samples. In the majority of the samples, the most potent variant, MC-LR, constituted the greatest proportion of the total MC concentration suggesting extremely high potential public health risk. The exceptionally high concentrations (μg L−1) of all the variants, MC-LR (815), MC-YR (466.6) and MC-RR (265.68), were observed in May. Although the extracellular MCs were relatively less concentrated and less frequently detected, concentrations (μg L−1) of up to 20 of MC-LR, 6.13 of MC-YR, and 1.27 MC-RR were encountered. The strong and significant association between Microcystis abundance and concentration of nitrate (Spearman Rank Order Correlation r = 0.793, p < 0.001) may suggest that nitrate is the key dictating factor in the dynamics of Microcystis, and may have consequently influenced the MC levels in the reservoir.

The influence of El Niño-induced drought on cyanobacterial community structure in a shallow tropical reservoir (Koka Reservoir, Ethiopia)

Koka Reservoir in Ethiopia has been severely impacted by water quality deterioration associated with harmful algal blooms. As a large proportion of the annual nutrient budget of the reservoir is believed to be of riverine origin, nutrient availability is presumably largely influenced by rainfall pattern and hydrological cycles, which are related to changes in climatic conditions such as El Nino-induced drought. The effect of El Nino-induced drought, which occurred in 2015, on the cyanobacterial community structure of Koka Reservoir was, therefore, investigated from May 28, 2015 to April 28 2016. The drought caused the failure of the main rainy season, which expectedly caused reduction in the external input of nutrients and changes in other limnological conditions of the reservoir. These changes, particularly nitrogen limitation, triggered the unusual dominance of the diazotrophic cyanobacterial genus Cylindrospermopsis over the previously persistently dominant nondiazotrophic genus, Microcystis, in the reservoir.

Assessment of the impact of climate change on future hydropower production from Koka Reservoir under two representative concentration pathways (RCP) emission scenarios

The aim of this research is to evaluate the impact of climate change on future hydropower generation in Upper Awash River Basin, Ethiopia. In analogous manner as professionals in the science of climate change try to project future climate variables based on the past and current situation of climate pattern, it is important that future hydropower energy is also projected as it is directly dependent on precipitation, one of the most important climate variables. This enables the planners, researchers, related professionals, and policy makers to implement reasonable policies to mitigate the adverse and negative effects of climate change on energy sector, as there is no sector which does not need energy in one way or another. Two scenarios of hydropower generation were developed based on two scenarios of climate change among others, namely RCP4.5 and RCP8.5, formulated by IPCC in the fifth assessment report, AR5. RCP4.5 is one of the two stabilisation scenarios. RCP8.5 represents the business as usual scenario and that there is no policy for alleviating the harsh effect of climate change. This certainly calls for special attention of the world community. It is considered reasonable to relate the projection of climate change with future hydropower production. The three periods selected for future hydropower projection for this study were 2019–2040, 2041–2070, and 2071–2100. The reference period (2006–2014) on which the projections are based is the time period for which monthly and annual hydropower production data are available. The water evaluation and planning was used to model hydropower production and related hydrological variables. As to RCP4.5 scenario, though variable, it was seen that there will be an increase in energy production in all the three periods as compared to the reference period. The increase in energy for the periods 2019–2040, 2041–2070, and 2071–2100 was predicted to be, respectively, 7.6%, 1.5%, and 0.9%. However, as can be seen from the percentages, the increment itself has a decreasing tendency going further in the future even for this middle concentration scenario. The result of simulation under RCP8.5 scenario revealed that there will be a decrease in energy by 15.1% in the last 2 decades of the twenty-first century. This would require big effort to compensate for the resulting problems.

Prevention of malaria transmission around reservoirs: an observational and modelling study on the effect of wind direction and village location

Many large dams are constructed annually in Africa, with associated reservoirs that might exacerbate the risk of malaria in new villages built nearby. We aimed to investigate the heterogeneous risk of malaria around reservoirs related to the impact of wind direction on malaria transmission. Between June 15, 2012, and April 22, 2015, we obtained field data on climate and hydrological conditions, and monitored Anopheles mosquito populations around the Koka reservoir in Ethiopia using in-situ weather stations, mosquito light traps, and larval dipping. The field data were used to calibrate a field-tested, spatially explicit mechanistic malaria transmission model, the Hydrology, Entomology, and Malaria Transmission Simulator (HYDREMATS), to investigate the effect of relative wind direction on malaria transmission and associated mechanisms. We combined our simulation results and observational data to assess the association between village location around a reservoir and risk of malaria. HYDREMATS simulations showed that wind blowing from a village towards a reservoir increases the size of malaria vector populations, whereas wind blowing from a reservoir towards a village decreases the size of malaria vector populations, which was consistent with our field data. Larval mortality is low in locations with village-to-reservoir wind due to weak surface waves, and this wind direction creates conditions that enable mosquitoes to identify village locations more easily than in conditions caused by reservoir-to-village wind, which increases the size of malaria vector populations, and thus malaria transmission. Among the wind conditions investigated (0·5-5 m/s), the effect of CO2 attraction on the size of the Anopheles population was largest at wind speeds of 0·5 m/s and 1 m/s, decreasing with higher wind speed. At a wind speed of 5 m/s, the effect of CO2 attraction was negligible, whereas the effect of waves was strongest. The effect of advection on Anopheles population size was negligible at all wind speeds and wind directions. The effect of wind on malaria transmission around reservoirs can be substantial. The transmission of malaria can be minimised if the location of villages situated near a reservoir is carefully considered. For areas in which the environmental conditions surrounding a resevoir are equal, villages should be located downwind of reservoirs to reduce the incidence of malaria, although further research will be required in locations where wind direction changes in different seasons. US National Science Foundation, and Cooperative Agreement between the Masdar Institute of Science and Technology, Abu Dhabi, UAE, and the Massachusetts Institute of Technology, Cambridge, MA, USA.

Concentrations of microcystins in the muscle and liver tissues of fish species from Koka reservoir, Ethiopia: A potential threat to public health

Herein, we report the presence and concentrations of three most common variants of microcystin (MC–LR, –RR and –YR) in the liver and muscle tissues of wild Nile Tilapia (Oreochromis niloticus), Common Carp (Cyprinus carpio) and African Sharp Tooth Catfish (Clarias gariepinus), which were collected from two study sites of the present study on Koka reservoir, Ethiopia. A total of 36 fish liver and 36 fish muscle samples were collected for six months. Microcystins (MCs) were quantified using LC-ESI-HRMS. The results show that MCs were found in most of the fish liver samples, while they were below the detection limit of the method of analysis used in the muscle samples. In addition to the three most common congeners of MCs, eight other microcystin variants and cylindrospermopsin were detected in the fish liver samples although further detailed study is needed. Among the three most common MC congeners, MC-LR was more prevalent than MC-RR and MC-YR in the liver samples of the three fish species. The highest MC concentration was found in Nile Tilapia collected in April (591.60 μg/g DW of MC-LR), whereas the lowest detected concentration was in Catfish collected in March (2.23 μg/g DW of MC-RR). The results of this study suggest that further intensive assessment and monitoring of the reservoir from different perspectives should be conducted in order to reduce the concentrations of the MCs and seek solutions to the potential public health risk. Moreover, this is the first study ever to report detailed quantification of MCs in fish liver and muscle samples collected from Ethiopia.

Cyanobacteria and microcystins in Koka reservoir (Ethiopia).

The composition and abundance of cyanobacteria and their toxins, microcystins (MCs), and cylindrospermopsins (CYN) were investigated using samples collected at monthly intervals from the Amudde side of Koka Reservoir from May 2013 to April 2014. Cyanobacteria were the most abundant and persistent phytoplankton taxa with Microcystis and Cylindrospermopsis species alternately dominating the phytoplankton community of the reservoir and accounting for up to 84.3 and 11.9% of total cyanobacterial abundance, respectively. Analyses of cyanotoxins in filtered samples by HPLC-DAD and LC-MS/MS identified and quantified five variants of MCs (MC-LR, MC-YR, MC-RR, MC-dmLR, and MC-LA) in all samples, with their total concentrations ranging from 1.86 to 28.3μgL-1 and from 1.71 to 33μgL-1, respectively. Despite the presence and occasional abundance of Cylindrospermopsis sp., cylindrospermopsin was not detected. Redundancy analysis (RDA) showed that the environmental variables explained 82.7% of the total variance in cyanobacterial abundance and microcystin concentration. The presence of considerably high levels of MCs almost throughout the year represents a serious threat to public health and life of domestic and wild animals.

Environmental Determinants of Malaria Transmission Around the Koka Reservoir in Ethiopia.

New dam construction is known to exacerbate malaria transmission in Africa as the vectors of malaria—Anopheles mosquitoes—use bodies of water as breeding sites. Precise environmental mechanisms of how reservoirs exacerbate malaria transmission are yet to be identified. Understanding of these mechanisms should lead to a better assessment of the impacts of dam construction and to new prevention strategies. Combining extensive multiyear field surveys around the Koka Reservoir in Ethiopia and rigorous model development and simulation studies, environmental mechanisms of malaria transmission around the reservoir were examined. Most comprehensive and detailed malaria transmission model, Hydrology, Entomology, and Malaria Transmission Simulator, was applied to a village adjacent to the reservoir. Significant contributions to the dynamics of malaria transmission are shaped by wind profile, marginal pools, temperature, and shoreline locations. Wind speed and wind direction influence Anopheles populations and malaria transmission during the major and secondary mosquito seasons. During the secondary mosquito season, a noticeable influence was also attributed to marginal pools. Temperature was found to play an important role, not so much in Anopheles population dynamics, but in malaria transmission dynamics. Change in shoreline locations drives malaria transmission dynamics, with closer shoreline locations to the village making malaria transmission more likely. Identified environmental mechanisms help in predicting malaria transmission seasons and in developing village relocation strategies upon dam construction to minimize the risk of malaria.

Modelling and observing the role of wind in Anopheles population dynamics around a reservoir

BackgroundWind conditions, as well as other environmental conditions, are likely to influence malaria transmission through the behaviours of Anopheles mosquitoes, especially around water-resource reservoirs. Wind-induced waves in a reservoir impose mortality on aquatic-stage mosquitoes. Mosquitoes’ host-seeking activity is also influenced by wind through dispersion of CO_2. However, no malaria transmission model exists to date that simulated those impacts of wind mechanistically.MethodsA modelling framework for simulating the three important effects of wind on the behaviours of mosquito is developed: attraction of adult mosquitoes through dispersion of CO_2 (CO_2attraction), advection of adult mosquitoes (advection), and aquatic-stage mortality due to wind-induced surface waves (waves). The framework was incorporated in a mechanistic malaria transmission simulator, HYDREMATS. The performance of the extended simulator was compared with the observed population dynamics of the Anopheles mosquitoes at a village adjacent to the Koka Reservoir in Ethiopia.ResultsThe observed population dynamics of the Anopheles mosquitoes were reproduced with some reasonable accuracy in HYDREMATS that includes the representation of the wind effects. HYDREMATS without the wind model failed to do so. Offshore wind explained the increase in Anopheles population that cannot be expected from other environmental conditions alone.ConclusionsAround large water bodies such as reservoirs, the role of wind in the dynamics of Anopheles population, hence in malaria transmission, can be significant. Modelling the impacts of wind on the behaviours of Anopheles mosquitoes aids in reproducing the seasonality of malaria transmission and in estimation of the risk of malaria around reservoirs.

Market Chain Analysis of Koka Reservoir Fish in Ethiopia

This study analyzed the fish market chain of Koka reservoir in Ethiopia which is found in Oromia Region, East shoa and Arsi zones. The objectives of the study were to assess the structure, conduct and performance of fish marketing as well as identify factors affecting fish market supply. The study was based on the data obtained from a sample of 104 fishers and 36 traders in the fish market chain. Both descriptive and econometric methods were employed to analyze the data. About 65% Tilapia (Coroso), 21% Catfish (Ambanza) and 14% Carp (Abasamuel) were the type of fish which dominantly appear in the day to day marketing activities of the fishers. The major determinant factors of market supply were estimated by using multiple linear regression models. The fish market performance was also measured using indicators of marketing margins. According to the results, there were three kinds of fish marketing channels i.e fishers to consumers, fishers to retailers then consumers, fishers to fishery cooperatives, wholesalers then consumers. The result showed that transportation and filleting costs were the largest costs of marketing followed by gutting cost. The price of a kilogram of filleted tilapia varied from 18 birr at landing site to 75 birr at Atiklt Tera in Addis Ababa. The Ordinary Least Square results indicated that education level, availability of credit facility and ownership of fishing license significantly affected the amount of fish supplied to market by fishers in the study area. Expanding adult education in fishery community, facilitating access to credit facility and encouraging fishers to be legal is very important for better harvesting and marketing of fish.

Heterotrophic Bacterial Population in Water, Sediment and Fish Tissues Collected From Koka Reservoir and Awash River, Ethiopia

The quantitative estimation of total heterotrophic bacteria in the water, sediment and body tissues is helpful in predicting the quality of the fish as well as the status of the water body. The bacterial population in the water of Koka Reservoir and the Awash River, studied monthly for a period of one year, showed variation from 0.0.2×10 4 cfu/ml to 2.6×10 4 cfu/ml. Whereas, in the sediment the highest population density was 2.6 cfu/g and the lowest was 0.98×10 4 cfu /g. The highest population density in the reservoir was recorded in the sediment in January, while in the water was in August. The heterotrophic bacteria population in the river water and sediment was lower than the reservoir. During the non rainy season (February and March) the sediment bacteria increased with increase in water temperature and reduced rate of water level. The bacteria in the river water greatly reduced during February even though a regular pattern was not evident throughout the study period. The total bacterial population in different tissues of Cyprinus carpio and Oreochromis niloticus showed maximum population in intestine, followed by gill, skin, kidney and liver

Participatory Evaluation and Verification of Improved Post Harvest Fishery Technologies on Selected Sites of Oromia water bodies

The study was conducted in the year 2009 to 2013 in different major sites of Oromia water bodies. These sites include lakes and reservoirs found in Abaya, Finchawa, Gilgalgibe, Koka, Langano, Malkawakana and Zeway. This research study focuses on fish smoking technology, fish drying using simple tent dryer, fish meal technology and fish cage retaining. Participatory Rural Appraisal (PRA) was conducted to assess the capture and culture fisheries post-harvest technologies information and communication support for resource exploitation, demand for information, opportunities and constraints of fishermen’s needs in the study area. The result indicated that simple drying using tent dryer at Abaya Lake, Langano, Finchawa and Gilgelgibe reservoirs are suitable and productive for the local fishermen. On the other hand, fish smoking at Gilgelgibe reservoir was not successful due to the unavailability of bricks made from mud in the area. At Koka reservoir fish meal technology was effective and well accepted by the locals. At Langano Lake fish smoking and fish meal technology were also suitable and successful. Moreover, fish smoking at Melkawakana reservoir and Zeway Lake, including fish drying using simple tent dryer were successful and in addition fish cage retaining were successful and recognized by the beneficiaries as possible source of income thus, ready for advance scaling at Melkawakana reservoir.