Lake Koka Research Articles

Multispectral remote sensing approach of predicting the potential distribution and evaluating the current spread of water hyacinth (Eichhornia crassipes)

The water hyacinth is categorized among the world’s top ten worst invasive plant species of aquatic ecosystems. This study assessed changes in the spatiotemporal distributions of the water hyacinth in Lake Koka and Ziway of the Upper Awash River basin during the peak growth season of the plant. Household questionnaires and key informant interviews along with Landsat images for 2013, 2017, and 2021 were collected to identify the past, present, and future potential distributions of the invasive plant in the two lakes. Household surveys and key informant interviews were prepared using the Kobo Toolbox which monitors data collection online. A total number of 413 households were sampled and the data were analyzed through descriptive statistics. For Landsat images, a supervised classification technique was applied to classify the land use classes using the maximum likelihood algorithm. The survey results showed increased water hyacinth expansion in the area since the year 2011. The water hyacinth expansion affected 285 households’ livelihoods by invading 69.0% of their farmlands which caused 97.6% food scarcity in the study districts. The results of the Landsat image indicated that the water hyacinth invasion in Lake Koka occupied 1.48% in 2013, and this increased to 7.13% in 2021, while the water body decreased from 75.94 to 69.90%, respectively. However, the area of the other vegetation is nearly identical between the years 2013–2021. Likewise, water hyacinth covered 4.66% of Lake Ziway in 2013, and this was raised to 8.42% in 2021. At Lake Ziway water hyacinth invasion affected the area of other vegetation coverage as it decreased from 16.19 to 10.67% but the area of the water body remained almost the same during the years. Between 2013 and 2025, the amount of water hyacinths increased in both Lake Koka and Lake Ziway. According to LULC data, the water hyacinth's rate of spread was 0.56% in Lake Koka and 0.95% in Lake Ziway. The results of this study revealed the signals of LULC change due to water hyacinth invasion in the Upper Awash Basin which is considered an important aspect for future water resources planning and management.

Seasonal variation of Water Hyacinth in Lake Koka, a part of Awash Basin and Lake Ziway (Ethiopia)

Seasonal variation of Water Hyacinth in Lake Koka, a part of Awash Basin and Lake Ziway (Ethiopia)

On the chigger mite (Acariformes: Trombiculidae) fauna of Ethiopia

ABSTRACT The chigger mites of Ethiopia were investigated based on materials collected in the field and museum depositories of alcohol-fixed mammals. Previously, only two chigger species were known from the country. In total, we collected 21 chigger species, mainly from rodents, occasionally insectivores, and one bat, from nine localities, and raised the number of trombiculids known from Ethiopia to 22. Three new species were described: Gahrliepia bochkovi sp. n. from a high-mountain locality of the Arsi Mountains National Park, Schoutedenichia borenensis sp. n. from Borena National Park, and Microtrombicula abaturovi sp. n. from Lake Koka located in the Great Rift Valley. Seventeen species were recorded in Ethiopia for the first time; four of them were for the first time recorded on the African continent – Leptotrombidium paradux Vercammen-Grandjean and Langston, 1976, Schoutedenichia asirensis Stekolnikov, Al-Ghamdi, Alagaili and Makepeace, 2019, S. originalis Kudryashova, 1976, and Microtrombicula saperoi (Radford, 1954). http://www.zoobank.org/urn:lsid:zoobank.org:pub:D79DC5A0-8340-4CC2-B9FD-F16A7CC38FE2

Reproductive biology and condition factor of the African catfish, Clarias gariepinus (Burchell 1822) in Lake Koka, Ethiopia

The study was conducted to investigate the breeding season, sex ratio, size at maturation, fecundity and condition factor of African catfish Clarias gariepinus in Lake Koka. A total of 754 fish specimens were collected from October 2020 to August 2021. Total length and weight were measured and sexes were identified and gonad maturity levels were recorded. The sex ratio of African catfish in different size classes was similar to that of a hypothetical 1:1 ratio. The length at first maturity (L50) was 51.8 cm in total length. The mean Fulton’s condition factor of female African catfish ranged from 0.65 ± 0.05 – 0.71 ± 0.14, while the males ranged from 0.62 ± 0.04 – 0.7 ± 0.11. The Fulton’s condition factor was significantly higher in August for females than in the rest of the sampling months. The highest ripe gonads were recorded in the rainy season and the lowest was in the dry season, with the percentage of ripe gonads being 27.5%, while the males showed similarly extended maturity patterns among seasons. Fisheries management for African catfish should therefore take into account the estimated L50 value and the main breeding season to sustain the fishery and benefits the fishermen.

Phytoremediation Capacity of Water Hyacinth (Eichhornia crassipes) as a Nature-Based Solution for Contaminants and Physicochemical Characterization of Lake Water

Water hyacinth (Eichhornia crassipes) is a potential accumulator of water pollutants in aquatic ecosystems, and its presence in water systems can affect water quality. This study used different field measurements and laboratory tests of lake water to determine the impact of water hyacinth phytoremediation capacity. A total of eight sampling stations were used for the two lakes: Lake Koka and Lake Ziway, Ethiopia. Sampling stations were selected from sites infested with water hyacinth (low, medium, and high) and non-water hyacinth aquatic plants during wet or rainy and dry or non-rainy seasons to compare the effects of plants on water quality in the two lakes. All the sampled stations had various human interventions. The water samples were tested for the selected physico-chemical properties, namely, phosphate, nitrate, pH, electrical conductivity (EC), the five-day biological oxygen demand (BOD5), water temperature, and heavy metals (Chromium (Cr), Lead (Pb), Cadmium (Cd), Zinc (Zn), and Copper (Cu)). These water quality variables were compared by means of ANOVA. Despite the chemical oxygen demand (COD) of Lake Ziway, this study found no significant (p > 0.05) variation in the concentrations of Cu, EC, pH and water temperature between wet and dry seasons in either lake. Variations in Zn concentration and other physico-chemical parameters (EC, BOD5, COD, nitrate, phosphate) between low, medium, and high levels of water hyacinth were significant in both lakes (p < 0.05). Water hyacinth has shown significant phytoremediation nature during wet and dry seasons. The lowest average heavy metal, phosphate, and nitrate concentrations; and significant pH and temperature variations were observed in Lakes Koka and Lake Ziway, among water hyacinth and other grass-infested sites. These findings suggest water hyacinth plant as a promising nature-based solution for removing undesirable chemicals from contaminated water bodies.

Consumer health risk assessment from some heavy metal bioaccumulation in common carp (Cyprinus carpio) from lake Koka, Ethiopia

Heavy metal pollution is a serious problem in Ethiopian rift valley lakes, including Lake Koka, as a result of unmanaged industrial waste pollution. However, the bioaccumulation level in common carp (Cyprinus carpio), a commercially important fish species, are unknown. The aim of this research was, therefore, to assess the heavy metal bioaccumulation in edible parts of common carp in Lake Koka and the associated health risks. Three sampling sites were selected randomly for primary data collection. Four heavy metals (Cd, Cr, Pb and Zn) were analyzed in water and the edible part of the fish using Atomic Absorption Spectroscopy (AAS). The mean concentrations of Zn, Cr and Cd in the edible part of fish ranged from 0.07 to 0.36 mg kg−1, Not Detected (ND)-0.24 mg kg−1 and ND-0.03 mg kg−1, respectively. Site 2 had the highest Zn and Cd content, while Site 3 had the highest Cr content. Pb was however not identified. The amount of Cr was above the permissible limit of FAO and the bioaccumulation showed marked differences among the sampling sites (p < 0.05). The concentrations of Cd, Pb and were below the maximum permissible limit. Cr and Zn had the highest and lowest transfer factor values, respectively. The carcinogenic hazard ratio values were below the threshold value (<1). The estimated weekly intake of heavy metals from fish muscles ranked as Cr > Zn > Cd, but the values were lower than the Reference Dose limit (RfDo). The carcinogenic risk value also indicated a low health risk associated with individual metals intake. Furthermore, the hazard index of the edible part of fish was less than unity. Generally, the water quality is not a risk for the survival and reproduction of fish and the heavy metal contents in the edible parts of fish exhibited low carcinogenic risk through the food chain.

Determination of 2,4-dichlorophenoxyacetic acid in water, sediment and soil using high performance liquid chromatography

ABSTRACT. The purpose of this study was to develop a method for the extraction and determination of 2,4-dichlorophenoxyacetic acid (2,4-D) from the soil, sediment, and water, and to investigate its stability in water using high-performance liquid chromatography (HPLC). The recoveries of the spiked compound from water and soil samples was found to be in the range of 80 to 100%. The yield of 2,4-D during acidification of the corresponding amine was 93.84-99.98%. A calibration curve for the method showed good linearity (R2 ≥ 0.9996). The LOD was determined to be 0.45 µg/mL while the LOQ was 2 µg/mL. From the analysis of the samples, 2,4-D was not detected in sediment or soil samples from the Wafiko or Kontola sites (Ethiopia), respectively. The 2,4-D concentrations in soil samples from Bochessa, and water samples from Wafiko and Sher sites (Ethiopia) were high, ranging from 68.22 to 167.7 mg/L which exceeded the United States Environmental Protection Agency (US EPA) regulatory agency standards of 70 µg/L. A 45-day experiment on spiked water samples from Lake Koka (Ethiopia) demonstrated that the acidic form of 2,4-D is stable in water with 73.46 ± 2.00% recoveries. The developed method can be used to determine 2,4-D residues in soil, sediment, and water.&#x0D; KEY WORDS: 2,4-Dichlorophenoxyacetic acid, Lake Koka, Sediment, Soil, Stability, Water&#x0D; &#x0D; Bull. Chem. Soc. Ethiop. 2023, 37(2), 251-263. &#x0D; DOI: https://dx.doi.org/10.4314/bcse.v37i2.1&#x0D; &#x0D; &#x0D;

Mobile trace elements in sediments from lakes Hawassa, Koka, and Ziway in the Ethiopian Rift Valley.

The present work focuses on total concentrations of trace elements such as chromium (Cr), manganese (Mn), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), arsenic (As), selenium (Se), cadmium (Cd), and lead (Pb) and their operationally defined speciation in surface sediments from three Ethiopian Rift Valley Lakes (Hawassa, Koka, and Ziway). Total concentrations were determined using inductively coupled plasma-mass spectrometer (ICP-MS). A six-step sequential extraction was also applied to evaluate the mobilization potential of these elements. Compared with the consensus-based sediment quality guidelines (SQGs) developed for freshwater ecosystems, the total Zn concentration in sediments from Lakes Hawassa and Ziway, as well as Cr, Ni, and Zn in sediments from Lake Koka, was higher than the probable effect concentration (PEC), suggesting that these elements could have a negative effect on benthic organisms. The sequential extraction results showed that Cd, Mn, and Se were to a certain extent associated with the reversible fractions (F1-F3) in sediments, and thereby more mobile than the other investigated trace elements. Predictions of mobility of trace elements using the distribution coefficients (Kd) values were also in agreement with the sequential extraction results. Furthermore, multivariate statistical analyses showed that redox-sensitive fractions (F4 and F6) and the residual fraction (F7) were the dominant factors controlling most trace element mobility. Finally, applying the Risk Assessment Code (RAC) classification system, results showed that Mn in Lake Koka could pose a high risk, while Cd and Mn in Lake Hawassa as well as Cd, Mn, and Se in Lake Ziway sediments could pose medium risk to benthic organisms.

Polymorphism of Sex Determination Amongst Wild Populations Suggests its Rapid Turnover Within the Nile Tilapia Species.

Sex-determining regions have been identified in the Nile tilapia on linkage groups (LG) 1, 20 and 23, depending on the domesticated strains used. Sex determining studies on wild populations of this species are scarce. Previous work on two wild populations, from Lake Volta (Ghana) and from Lake Koka (Ethiopia), found the sex-determining region on LG23. These populations have a Y-specific tandem duplication containing two copies of the Anti-Müllerian Hormone amh gene (named amhY and amhΔY). Here, we performed a whole-genome short-reads analysis using male and female pools on a third wild population from Lake Hora (Ethiopia). We found no association of sex with LG23, and no duplication of the amh gene. Furthermore, we found no evidence of sex linkage on LG1 or on any other LGs. Long read whole genome sequencing of a male from each population confirmed the absence of a duplicated region on LG23 in the Lake Hora male. In contrast, long reads established the structure of the Y haplotype in Koka and Kpandu males and the order of the genes in the duplicated region. Phylogenies constructed on the nuclear and mitochondrial genomes, showed a closer relationship between the two Ethiopian populations compared to the Ghanaian population, implying an absence of the LG23Y sex-determination region in Lake Hora males. Our study supports the hypothesis that the amh region is not the sex-determining region in Hora males. The absence of the Y amh duplication in the Lake Hora population reflects a rapid change in sex determination within Nile tilapia populations. The genetic basis of sex determination in the Lake Hora population remains unknown.

Production and Characterization of Bio-diesel from Water Hyacinth (&amp;lt;i&amp;gt;Eichhorniacrassipes&amp;lt;/i&amp;gt;) of Lake Koka, Ethiopia

Ethiopia has a large biomass of water hyacinth (<i>Eichhorniacrassipes</i>) in Lake Koka and LakeTana during the summer season. Local community of Lake Koka doesn’t use this water hyacinth. So the activity is designed to produce biodiesel from water hyacinth and determine its quality parameters. This should be based on the concept of produce renewable energy and discard water hyacinth from the lake. The Specific gravity (g/ml), Acid value (mgKOH/g), Water content (mg/g), kinematic Viscosity (mm²/sec) and ash% (w/v) content of water hyacinth (<i>Eichhorniacrassipes</i>) biodiesel were 0.912, 0.4, 0.004, 2.7 and 0.001 respectively. The Nutrient analysis of water hyacinth from Lake Kokawas takes place in NFLARC laboratory to evaluate for biodiesel purpose. The proximate composition of water hyacinth from Lake Kokawas moisture content % (w/w) 76.2 ± 0.1, lipid content % (w/v) 0.49 ± 0.23%, crude protein % (w/w) 10.23 ± 0.34%, ash content % (w/w) 9.5 ± 0.02%, carbohydrate % (w/w) 3.58 ± 0.6%, and gross energy (kcal/100g) 59.65 ± 0.53%. From the study it can be conclude that the parameters of biodiesel get from water hyacinth is fulfill the requirement set by American and European biodiesel standards. The problem is that the oil content of water hyacinth is too much low and can’t economically visible to produce biodieselfrom water hyacinth (<i>Eichhorniacrassipes</i>).

Economic Importance, Impacts and Possible Mitigation Measures of Aquatic Water hyacinth (Eichhornia crassipes Martius) in Ethiopia

Water hyacinth is one of invasive weed species which belongs to family Pontederiaceae which was characterized by a free floating perennial aquatic weed and one of the major challenging problems in water bodies of the tropics and sub-tropics. Therefore, the aim of this article is to identify the distribution,impacts and beneficial effects as well as the possible management practices of water hyacinth.Water hyacinth was introduced in the water bodies of the Rift Valley in 68 years ago and currently, the weed is distributed Lake Tana, Lake Abaya, Lake Koka, Koka Dam in Ethiopia.The weed affected water resources, fisheries, transportation and social structure.The wide distribution and abundance of water hyacinth has led to decreased water availability and sustainable water biodiversity in Ethiopian lakes. However, the spread of water hyacinth is threatening not only water bodies but also socioeconomic development and human health. Water hyacinth in water bodies and nearby areas of local stakeholder has negative impact on environment and also impact on aquatics biodiversity.In contrast to these,Water hyacinth is rich sources of different nutrients that provides feed for animals such as ruminants, Rabbits, Ducks, Geese, Pigs and Fish.Water hyacinth can be controlled by mechanically by machine or manual which was environmentally safe as compared to other methods. Physical control includes automatic mowers and dredgers.Biological method by using bioagents weevils which involves long term strategy and chemical involves by using herbicides 2,4 - D, Diquat and Glyphosate that can be implemented by accomplished operator.Therefore, sustainable long term management strategies should include prevention in newly infested areas. in low infested areas, integrated use of herbicides has to be developed. To contain the further spread and buildup of this weed for future infestation, these weeds should be utilized for composting and feed purposes. Besides,extensive mass awareness and community campaign especially to uproot should be implemented. Therefore, it can be summarized that human intervention is considered as the current problem of water resource in the country and further study is needed to sustain the water resource to keep water hyacinth at economic thresh hold level. Keywords : caused, dense mats,problems,reported,water hyacinth DOI: 10.7176/JEES/11-3-01 Publication date: March 31 st 2021

Opportunities and its challenges in fish production: The case of Lake Koka, East Showa Zone, Oromia National Regional State, Ethiopia

The study was conducted to assess opportunities and challenges in fishery the case of Lake Koka, Ethiopia. Interview, focus group discussion and personal observations were used as means of data collection. Response was solicited from households within the catchment area of the reservoir, key informants, fish cooperative chairman and cooperative member households. The collected data were analyzed through descriptive statistics and narration. At the study area fishing activities were done through cooperative form that make an opportunity to operate fishing at full time. In the study area farmers were used fishing mainly as direct income generation that used for direct use of family members. Fishing activities were also dominated by male household having of fishing experience of below five (5) years. In addition to fishing, those household support their livelihoods with other agricultural activities. Increasing the demand of fish, availability of commercially consumed fish species and Good market outlet are some of the main opportunity that was specified by fishing households. Evasive weed water hyacinth, inadequate government support and water pollution are mentioned as the main challenge with insufficient value chain and unreliable market situation. So, it should be need an emphasis on integrated management to overcome challenges for effective utilization fish resources.

Structure and Sequence of the Sex Determining Locus in Two Wild Populations of Nile Tilapia.

In domesticated strains of the Nile tilapia, phenotypic sex has been linked to genetic variants on linkage groups 1, 20 and 23. This diversity of sex-loci might reflect a naturally polymorphic sex determination system in Nile tilapia, or it might be an artefact arising from the process of domestication. Here, we searched for sex-determiners in wild populations from Kpandu, Lake Volta (Ghana-West Africa), and from Lake Koka (Ethiopia-East Africa) that have not been subjected to any genetic manipulation. We analysed lab-reared families using double-digest Restriction Associated DNA sequencing (ddRAD) and analysed wild-caught males and females with pooled whole-genome sequencing (WGS). Strong sex-linked signals were found on LG23 in both populations, and sex-linked signals with LG3 were observed in Kpandu samples. WGS uncovered blocks of high sequence coverage, suggesting the presence of B chromosomes. We confirmed the existence of a tandem amh duplication in LG23 in both populations and determined its breakpoints between the oaz1 and dot1l genes. We found two common deletions of ~5 kb in males and confirmed the presence of both amhY and amh∆Y genes. Males from Lake Koka lack both the previously reported 234 bp deletion and the 5 bp frameshift-insertion that creates a premature stop codon in amh∆Y.

Accumulation of heavy metals in the physical and biological systems of Lake Koka, Ethiopia: Implications for potential health risks

AbstractLake Koka has several important socioeconomic uses, hydroelectric power generation, domestic water supply, irrigation, recreation and fishery. It is currently under serious threat, however, because of point and nonpoint pollution inputs. The objective of the present study was to examine the concentration of heavy metals (Mn, Cr, Pb, Zn, Cu, Ni and Cd) and their bioaccumulation, and biomagnification factors along the lake's food chain in order to assess the potential human and ecological health risks. Water, sediment and plankton samples were collected from seven sampling sites and fishes were purchased on site from fishers. The analyses were performed using a graphite furnance atomic absorption spectrophotometer. Heavy metals levels in the sediment samples were ranked in the order of Mn &gt; Cr &gt; Pb &gt; Zn &gt; Cu &gt; Ni &gt; Cd. Similarly, the metal concentration in the fish muscles was Cr &gt; Cu &gt; Pb &gt; Cd. The sediment bioaccumulation factor (&lt;1) and water bioaccumulation factor (&gt;1) for Cd, Pb and Cr indicated the lake water exhibited higher concentrations than the sediment. In parallel, the Cr biomagnification factor for zooplankton, catfish, Nile tilapia and common carp was 1.63, 1.18, 1.36 and 2.28, respectively. The Cr concentrations at the Modjo (or Mojo) Upstream, Modjo Downstream and Kentare sites, and the Pb concentrations at riverine sites were above the permissible limits established by the World Health Organization. Cr ranked as fish species &gt; zooplankton &gt; phytoplankton, being above the permissible limits in catfish, Nile tilapia and common carp. Generally, the weekly intake estimates were considerably lower than the tolerable human intake values provided by WHO and others. However, Cr biomagnified along the trophic levels ultimately reaching the top consumers, with Cr (VI) being carcinogenic. The lake is a major fishery source, indicating care must be taken in regard to the weekly intake of the fishes, particularly common carp.

Genetic parameters and genotype by environment interaction of the Nile tilapia (Oreochromis niloticus) reared in two test environments

The Nile tilapia (Oreochromis niloticus) is a globally important aquaculture fish species, particularly in tropical and subtropical areas. However, aquaculture in many African countries including Ethiopia is not well developed. One of the main challenges for the development of aquaculture in Ethiopia is the lack of better performing Nile tilapia strain that can grow well in a wide range of production environments, and thus, it is crucial to develop fast growing Nile tilapia strain that can grow in a wide range of environments. Therefore, the main objectives of this study were to evaluate growth performance and genetic parameters such as heritability, additive genetic and genetic correlation of different strain combinations, and level of genotype by environment interaction (GxE) for harvest body weight (HBW) of 2409 fish from 81 full-sib families reared in high- (Hi-P) and low-input (Lo-P) pond-based production systems. The full-sib families were produced in a complete diallel cross of three Ethiopia Nile tilapia strains collected from Lake Chamo, Lake Koka, and Lake Ziway. After 5 months of rearing, HBW were measured and then phenotypic and genetic parameters were analyzed using univariate and bivariate animal models using SAS and ASReml softwares. The results of the study showed that the Chamo and the Koka strains and their crossbreds preformed significantly better than that of the Ziway strain and its crossbreds with the other two strains. The HBW of the fish obtained from the two production systems (111.4 g for Hi-P and 100.5 for Lo-P was not significantly different (P > 0.05).The heritability estimates from bivariate model were 0.23 and 0.20 for Hi-P and Lo-P, respectively. The heritability estimates of common full-sib for HBW of the fish reared in the Hi-P were higher (0.03) than found in the Lo-P (0.002). Re-ranking of the different strain combinations in the two production systems was observed. However, the high genetic correlation (0.95) and the non-significant (P > 0.05) GxE resulted in a weak re-ranking of strain combinations. In conclusion, the higher genetic correlation with low genotype by environment interaction between the harvest body weight of the fish reared in the two production systems indicated that environment-specific breeding program is not essential. However, the use of Hi-P prefereble.

Aquatic macrophytes in Ethiopian Rift Valley Lake Koka: Biological management option to reduce sediment loading

Nowadays, due to deforestation, poor soil management and improper farming techniques, reservoir and lake sedimentation is a serious problem in Ethiopia. Despite the severity of the problem, there is no documented study on the use of macrophytes as a biological management option for sediment loading. A sediment trap field experiment was conducted from July to September 2017 to assess the efficiency of macrophytes in reducing sedimentation problem in Lake Koka. During the study period (90 days) on average a total of 1140 g DW m−2 sediment was deposited at the vegetated stations and 336 g DW m−2 at the open water site. The corresponding values for resuspension were 906 g DW m−2 and 1680 g DW m−2, respectively. Compared with the non-vegetated area, all macrophytes significantly facilitated sedimentation and reduced resuspension (P < 0.05). The order of the macrophytes in their sediment trapping efficiency was Echinochloa stagnina>Typha angustifolia > Eichhornia crassipes = Leptochloa caerulescens and the corresponding order for restraining resuspension was T. angustifolia > E. stagnina >E. crassipes = L. caerulescens. Generally, E. stagnina and T. angustifolia were better in trapping sediment and preventing resuspension. Development and maintenance of wetlands with these aquatic macrophytes may be an effective management tool for reducing the sediment load on Lake Koka, but would need further studies on the effect of wind velocity and direction on their efficiency.

Distribution, Impacts and Management Option for Water Hyacinth (Eichhnornia Crassipes [Mart.] Solms) in Ethiopia: A Review

Water hyacinth (Eichhprnia crassipes) is the most dangerous and worst invasive aquatic weed in the worldwide including Ethiopia, and negatively affecting millions of water resources, fisheries, transportation and social structure. Water hyacinth was introduced in the water bodies of the Rift Valley in 68years ago and currently, the weed is distributed Lake Tana, Lake Abaya, Lake Koka, Koka Dam. The wide distribution and abundance of water hyacinth has led to decreased water availability and sustainable water biodiversity in Ethiopian lakes. However, the spread of water hyacinth is threatening not only water biodiversity but also socioeconomic development and human wellbeing. Water hyacinth in water bodies and nearby areas the local stakeholder has its negative impact on environmental problem and it’s influenced aquatics biodiversity. This review paper aimed to investigate the distribution, impacts and its integrated management option against water hyacinth in Ethiopia. Therefore, based on the review it can be concluded that human intervention is considered as the current problem of water resource in the country and further study is needed to sustain the water resource are needed to keep water hyacinth at unproblematic levels.

Systematic modeling of impacts of land-use and land-cover changes on land surface temperature in Adama Zuria District, Ethiopia

Land surface temperature (LST) has been increasing year after year globally. The present investigation was aimed to study the impact of land-use/land-cover changes on LST in the Adama Zuria District in Ethiopia. Land-use/land-cover, LST and Normalized Difference Vegetation Index were extracted from Landsat TM (1989), Landsat ETM + (1999) and Landsat 8 OLI/TIRS (2016) using GIS and remote sensing tools. Land surface temperature was assessed using split window algorithm. Land-use/land-cover changes that occurred during 1989–2016 in the study area were evaluated and analyzed using geospatial tools and verified by field data. Results indicated that farmland covered more than 60% during the study period (1989–2016) followed by shrub land (> 12%). Most areas with lower LST in 1989 were changed to higher LST in 1999 and 2016 in response to different changes in land-use/land-cover pattern. By linking land-use/land-cover pattern changes and LST using zonal statistics, LST is found to have negative relationship with the extent of vegetation cover. Land surface temperature results showed that the northwestern, south, lake Koka area and along Awash river relatively low LST that ranged between 9 and 21 °C in response to the high NDVI values. The eastern, Adama town and western part of the study area showed high LST of up to 42 °C. Visual comparison of 1989, 1999 and 2016 images showed that the land-use/land-cover type and NDVI status play a major role for the variability of LST values. Correlation between LST and land-use changes has indicated that changes to settlement/urban land-use/land-cover have influenced LST proportionately. Relevant measures are to be taken by the bodies concerned to minimize land-use/land-cover changes to gain effective control over increasing LST in the study area.

Valuation of Wetland Attributes: An Application of Choice Experiment Approach: A Case Study of Lake Koka

Ethiopia has many lakes, the greater part of which is found in the Rift-valley, that are central for the development of economy of the country. One of these Lakes is Lake Koka, which is found inside the Ethiopian Rift Valley, and is an artificial lake built in 1960 to generate hydroelectric power. In spite of different advantages provided by Lake Koka, absence of powerful administration, uncontrolled irrigation, intensive agriculture and different human made activities has prompted to the degradation of the wetland. Human made activities such as, using wetland as waste disposal, over grazing, etc. aggravate the problems of the lake. To assign monetary values for the multi-functions and services offered by this Lake wetland ecosystem, this study applied choice experiment valuation method by identifying five attributes i.e. fish stock, biodiversity, water quality, availability of water and monetary payment. Multinomial logit, random parameter logit and latent class models were used to analyze the data collected from a sample of 200 respondents. The marginal willingness to pay for the improvement of water availability attribute is the highest which is birr 55 and it is significant at 1% level. Respondent’s willingness to pay for an increase in the level of water quality of Lake Koka and biodiversity from current situation of the lake, other things being constant, is birr 42 and birr 12 annually respectively. Respondents gave more value to the availability of water than biodiversity and water quality attributes.

Modeling trophic interactions and the impact of an introduced exotic carp species in the Rift Valley Lake Koka, Ethiopia

The study aims to describe the energy flow and trophic structure, to assess the ecological stage of maturity, the ecosystem impact of the introduced exotic carp species and the current fishery on the Lake Koka ecosystem using a mass-balance trophic model. The Ecopath approach and software were used to represent the lake ecosystem, and input parameters were obtained from in-situ surveys and from published lake specific sources. The model was balanced as per the recommended ecological and thermodynamic constraints. The low ecotrophic efficiency found for adult catfish, primary producers and detritus suggest that these resources are not fully utilized, while other groups have moderate to high values. The annual fishery catch represents only about one sixth of the total fish biomass, and the exploitation rates of target species are well below 0.5 suggesting under-exploitation. The dietary intake of fish-eating birds is 5.8 t km–2 year–1 almost twice the catch, showing the lake’s important role for sustaining the bird populations and hence, caution needs to be taken before implementing any further fisheries development intervention. The mean trophic level of the catch (2.55) is intermediate when compared to other tropical lake systems and reflects the mixed fishery of the lake. Mixed Trophic Impact and Niche Overlap analysis reveals that, contrary to what may be expected, the impact of the introduced exotic carp species on the lake system is less significant than that of the native species. Besides its socio-economic significance, the detritivorous carp seems to fill an unutilized niche and helps the system in recycling organic matter. The P/R value (3.2) and other system maturity indices indicate that Lake Koka is as yet an immature, developing system. The model can be used as a reference for exploring ecosystem-based fisheries management scenarios aimed at sustaining fish stocks, ecosystem services as well as ecological integrity.