Pesticide concentration in three selected fish species and human health risk in the Lake Tana sub-basin, Ethiopia

Pesticide use has increased in the Lake Tana sub-basin due to increased agricultural activity, potentially endangering nontargeted organisms. To assess its potential impact on fish health and fish-consuming human populations, pesticide concentrations in the fillet and liver tissue of three fish species, namely Labeobarbus megastoma, Labeobarbus tsanensis, and Oreochromis niloticus, were investigated in Lake Tana. Fish samples were taken from the lake near the rivers of Ribb and Gumara, which flow through agricultural areas where considerable amounts of pesticides have been applied. A total of 96 fish samples were collected. Liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) revealed the presence of ten pesticides. Pyrimethanil was frequently detected in 96% of liver and 65% of fillet samples at a median concentration of 33.9 µg kg-1 and 19.7 µg kg-1, respectively. The highest concentration of pyrimethanil was found in L. megastoma (1850.0 µg kg-1). Labeobarbus megastoma also had the highest concentration of oxamyl (507.0 µg kg-1) and flazasulfuron (60.1 µg kg-1) detected in the liver tissue. The highest concentration of carbaryl (56.5 µg kg-1) was found in the liver tissue of O. niloticus. Fish tissue samples from the two study sites contained pyrimethanil, oxamyl, carbaryl, and flazasulfuron. Only pyrimethanil showed a statistically significant difference between the two sites and the species L. megastoma and L. tsanensis. The amounts of pesticides found in the fish species pose no direct risk to the health of fish consumer human population. However, the results show that the lake ecosystem needs immediate attention and regular monitoring of the rising pesticide usage in the lake watershed.

On the use of contingent valuation method to assess factors affecting the contribution of local people for the management of water hyacinth in Lake Tana, northwestern Ethiopia

The colonization of freshwater lakes by invasive alien species is increasingly alarming primarily owing to nutrient loads from the watersheds. For the sustainable management of invasive weeds, preventive methods, such as watershed management and sustainable agricultural practices, are recommended. Watershed protection activities by the upstream local community are believed to be effective measures to reduce nutrient loading to the receiving water bodies and hence help prevent the spread of water hyacinth. However, their willingness and potential contributions determine the effectiveness of watershed management activities. The objective of this study is, therefore, to evaluate the preferences and contributions (willingness to pay and willingness to contribute labor) of the local community for the management of water hyacinth in Lake Tana (Ethiopia). A contingent valuation method for a hypothetical market "prevention of water hyacinth infestation of Lake Tana through watershed management program" was used to collect data from 560 randomly selected households. A multivariable interval regression model was used to identify factors affecting the contribution of local people. The mean yearly willingness to pay and to contribute labor of the respondents was 435.4 Ethiopian Birr (US$ 10) and 22.4 man-days, respectively. The place of residence (rural/urban), educational level, private farm plot area, annual income, and water hyacinth-related conference participation significantly influenced the willingness to pay. Similarly, the willingness to contribute labor was strongly associated with place of residence, location, educational level, and household family size. The economic value derived from this study reflects community preferences, which could be an input for informed and evidence-based decision-making regarding the prevention of weed expansion and sustainable use of ecosystem services. Therefore, local, regional, and national authorities are advised to mobilize the local community to contribute labor and/or money so as to halt the expansion of the weed.

Levels of Escherichia coli as Bio-Indicator of Contamination of Fish Food and Antibiotic Resistance Pattern Along the Value Chain in Northwest Ethiopia

INTRODUCTION

Microbiological contamination in fish origin foods is the leading risk for public health. Among the range of pathogenic bacterial species that cause fish food borne diseases is Escherichia coli. The pathogenic strains of Escherichia coli cause diarrhea by producing and releasing toxins and can also be the cause of food spoilage in fish.

METHODS

A cross-sectional study was conducted to assess hygienic practices of fish handlers, to evaluate bacterial load and antimicrobial resistance patterns of Escherichia coli along the fish value chain in Northwest Ethiopia. Systematic and purposive sampling techniques were used for uncooked and cooked fish samples respectively.

RESULTS

From a total of 180 fish samples, 36 (20%) were positive for Escherichia coli. From 115 uncooked and 65 cooked fish samples examined, 27 (23.5%) and 9 (13.8%) had E. coli respectively. The highest mean bacterial count was observed in raw fish samples (6.13 × 10⁵ cfu/g), followed by cooked fish samples (2.81 × 10⁴ cfu/g). Among the interviewed fish handlers, 83.3%, 76.7% and 80% of respondents had good knowledge and attitude towards using a clean cutting-and-filleting board, storing raw and cooked foods separately and using an apron for reducing the risk of fish contamination, respectively. All 36 isolates were 100% sensitive to ciprofloxacin and gentamycin. Of the Escherichia coli isolates subjected to tetracycline, 55.6% were resistant, 8.3% were intermediate and 36.1% were susceptible.

CONCLUSION AND RECOMMENDATION

This study revealed that there was a lack hygienic practice and high Escherichia coli profiles were observed. Hence, it could be wise to advise the fish harvesters, fish traders, hotels and restaurants about fish food safety practices from harvesting to consumption to improve fish food safety practices and quality standards of fish harvested and sold in northwest Ethiopia.

Compost preparation, chemical analyses and users' perception in the utilization of water hyacinth, Ethiopia

Lake Tana is the largest freshwater body in Ethiopia. Currently, the lake has been facing alarming environmental degradation and loss of biodiversity due to the invasion of water hyacinth. Although the weed is invasive, it can be converted into various benefits. Hence, this study was conducted in North Eastern Lake Tana, Sheha Gomengie Kebele. The main objective is compost preparation in terms of its drying periods, analyses, and user perception. Physicochemical and nutrient analyses were performed according to the standard procedures. Acid digestion was used for heavy metal analyses. From the result, the pH measurements ranged from 7.619 ± 0.195 to 7.719 ± 0.261, and the moisture content ranged from 38.712 ± 0.680 to 49.60 ± 9.06%. The mean electrical conductivity (EC) values of all treatments of matured compost ranged from 2.780 ± 0.542 to 3.51 ± 0.971 ds/m. The TN values of the matured compost ranged from 0.420 ± 0.379 to 0.754 ± 0.194 on a dry weight basis. The overall mean values of the C:N ratio for all the treatments were 11.60 which is within an acceptable range. A high amount of available P concentrations was observed in all compost treatments which ranged from 2.740 ± 0.190 to 2.940 ± 1.410 g/kg. Moreover, the concentrations of heavy metals in all treatments were below the permissible limit of different agencies and there was also no significant difference in the mean values of analysis of variance at (P < 0.05). Therefore, the prepared compost can be recommended for better agricultural purposes. Considering users' understanding of compost preparation as an opportunity, converting WH into compost is promising in terms of its rich supply and the possibility of preparing in the dry season where labor is abundant. Therefore, it can be one way of sustainably reducing WH adverse effects on the Lakeshore.

Economic valuation of attributes of Lake Tana: random parameter model

The general objective of the study is estimating economic value of Lake Tana attributes using stated preference method of valuation in general and choice experiment method in particular. The target population was households who live around Lake Tana. The study has identified four attributes of Lake Tana (Water quality, fishery, irrigation, and recreation). The study has formulated three alternatives in which two of them were improved whereas the one is the status quo. Each attribute has three levels. The study has surveyed 238 households which were selected using multistage sampling method. Each respondent was presented with eight choice sets. Each choice set has three alternatives including opt option. The study has employed random parameter logit model for data analysis. In line with this model the study has conducted the extended random parameter logit model. The status quo (ASC0) is negative and significant both in random parameter logit model but positive and insignificant in extended random parameter logit model. This means that households have preferred the improved situation of the Lake Tana. This indicates that households are willing to pay to improve the current situation of the lake. Random parameter logit model shows that all improved attributes have positive sign and significant at 1% significance level. This means that improved situation of attributes that are identified by this study improve utility of households. Government should protect Lake Tana from any problem by raising funds from households since households are willing to pay to improve Lake Tana's attributes.

Spatial coverage of water hyacinth (Eichhornia crassipes (Mart.) Solms) on Lake Tana and associated water loss

The introduction of water hyacinth poses a serious threat to economic viability of Lake Tana and its environments. This study aimed to capture the spatial coverage of water hyacinth and its effect on water loss in Lake Tana using quantitative research methods. Four satellite images representing each season of 2019 were downloaded from USGS. In addition, pan evaporation data were taken from the National Meteorological Agency. ArcGis 10.4, Envi 5.3, Qgis 3.12.1 plug in CSP and Excel used to manage land use land cover classification and water loss estimation analysis. The seasonal coverage of water hyacinth was 15.35, 4.14, 11.82 and 13.59 km² in winter, autumn, summer and spring 2019 respectively representing 0.63 and 0.17 percent of the Lake as a maximum and minimum coverage. The mean daily evaporation of Lake Tana was 5.14 mm/day, but this increased to 18.85 mm/day due to the presence of water hyacinth. The mean net daily water loss due to water hyacinth at Lake Tana was 0.14 km² while 52,62 km³ in 2019. The study concludes that water hyacinth caused enormous negative impact on the water volume reduction in Lake Tana. Management of the Lake Tana environment and control of the water hyacinth weed are recommended to sustain the Lake.

Socio-economic importance of forest resources and their conservation measures in Ethiopia: the case of area closure in South Gonder of Ethiopia

Area closures that set aside to degraded lands for rehabilitation purposes are a popular forest conservation measure in various parts of the world. However, their use can be controversial because, if poorly designed, they can accelerate the degradation of neighboring unprotected lands and deny local residents' access to important ecosystem services. This paper reports the results of a study on the area closure approach used in south Gonder within the Lake Tana watershed of Ethiopia to stem the rapid decline of vegetation cover that has occurred there over the last four decades. We used a mixed-methods approach that combined data from a household survey, focus group discussions, key informant interviews, and official documents. We found that support for the area closures was high. We also found that area closures have had a mixed effect on access to key ecosystem services while a number of important concerns about the negative impacts to surrounding unprotected forests were also expressed. We conclude that area closures have garnered broad public support within our study region but this support appears to be mostly contingent on management successes within protected forests and does not necessarily capture the unintended negative consequences to surrounding unprotected forests.

Assessing the implications of water harvesting intensification on upstream-downstream ecosystem services: A case study in the Lake Tana basin

Water harvesting systems have improved productivity in various regions in sub-Saharan Africa. Similarly, they can help retain water in landscapes, build resilience against droughts and dry spells, and thereby contribute to sustainable agricultural intensification. However, there is no strong empirical evidence that shows the effects of intensification of water harvesting on upstream-downstream social-ecological systems at a landscape scale. In this paper we develop a decision support system (DSS) for locating and sizing water harvesting ponds in a hydrological model, which enables assessments of water harvesting intensification on upstream-downstream ecosystem services in meso-scale watersheds. The DSS was used with the Soil and Water Assessment Tool (SWAT) for a case-study area located in the Lake Tana basin, Ethiopia. We found that supplementary irrigation in combination with nutrient application increased simulated teff (Eragrostis tef, staple crop in Ethiopia) production up to three times, compared to the current practice. Moreover, after supplemental irrigation of teff, the excess water was used for dry season onion production of 7.66 t/ha (median). Water harvesting, therefore, can play an important role in increasing local- to regional-scale food security through increased and more stable food production and generation of extra income from the sale of cash crops. The annual total irrigation water consumption was ~4%-30% of the annual water yield from the entire watershed. In general, water harvesting resulted in a reduction in peak flows and an increase in low flows. Water harvesting substantially reduced sediment yield leaving the watershed. The beneficiaries of water harvesting ponds may benefit from increases in agricultural production. The downstream social-ecological systems may benefit from reduced food prices, reduced flooding damages, and reduced sediment influxes, as well as enhancements in low flows and water quality. The benefits of water harvesting warrant economic feasibility studies and detailed analyses of its ecological impacts.

Evaluation of stream water quality data generated from MODIS images in modeling total suspended solid emission to a freshwater lake

Modeling of suspended sediment emission into freshwater lakes is challenging due to data gaps in developing countries. Existing models simulate sediment concentration at a gauging station upstream and none of these studies had modeled total suspended solids (TSS) emissions by inflowing rivers to freshwater lakes as there are no TSS measurements at the river mouth in the upper Blue Nile basin. In this study a 10year TSS time series data generated from remotely sensed MODIS/Terra images using established empirical relationship is applied to calibrate and validate a hydrology model for Lake Tana in Upper Blue Nile Basin. The result showed that at a monthly time scale TSS at the river mouth can be replicated with Nash-Sutcliffe efficiency (NS) of 0.34 for calibration and 0.21 for validation periods. Percent bias (PBIAS) and ratio of the root-mean-square error to the standard deviation of measured data (RSR) are all within range. Given the inaccessibility and costliness to measure TSS at river mouths to a lake the results found here are considered useful for suspended sediment budget studies in water bodies of the basin.