Fisheries and Aquatic Sciences

Watershed Ecosystem Health and Macroinvertebrate Responses to Climate and Land Use Change in the Dinki Watershed, Ethiopia

2026-10-07T12:29:50Z

Watershed Ecosystem Health and Macroinvertebrate Responses to Climate and Land Use Change in the Dinki Watershed, Ethiopia Worku, Yared Watersheds regulate hydrological processes, support biodiversity, and provide essential ecosystem services, but are increasingly affected by land-use change, climate variability, and human activities. In the Dinki Watershed of the central highlands of Ethiopia, agricultural expansion, habitat loss, and hydrological changes have increased pressure on watershed ecosystems, while information on biophysical characteristics, LULC dynamics, ecosystem services, climate variability, aquatic biodiversity, long-term ecological changes, and watershed management remains limited. Therefore, this study assessed watershed ecosystem health and macroinvertebrate responses to climate and land-use change by characterizing biophysical attributes, evaluating LULC changes and their effects on ecosystem services, examining spatial and temporal changes in macroinvertebrate communities and ecosystem health between 2016 and 2023, identifying key environmental drivers, and assessing potential future vulnerability. A comparative spatiotemporal research design was employed, with hydrological characteristics analyzed using ArcGIS 10.5, LULC dynamics from 1994 to 2023 assessed using supervised Support Vector Machine (SVM) classification, and ecosystem service values estimated by integrating remote-sensing outputs, global ecosystem evidence, and socioeconomic perceptions from key informant interviews (KIIs) and focus group discussions (FGDs) analyzed using QDA Miner Lite. Climate variability was evaluated using 30 years of rainfall and temperature data from the Ethiopian Meteorology Institute and analyzed in Python, while soil physicochemical properties, including pH, EC, nutrients, texture, and bulk density, were obtained from EthioSIS and analyzed using R. Macroinvertebrates were sampled following South African guidelines, with 100 composite samples collected from 25 sites during wet and dry seasons in 2016 and 2023 and identified to family level. Ecological responses were assessed using paired t-tests, ANOVA, rmANOVA, and MANOVA, while community patterns were examined using PCA, NMDS, and RDA, and indicator taxa were identified using IndVal analysis. A multimetric index (MMI) was developed from 37 candidate metrics, with five core metrics selected through statistical screening and validation: %EOT, %Trichoptera, Hemiptera abundance, ASPT, and FBI. Pollution-sensitive taxa (Perlidae and Philopotamidae) were modeled using ensemble approaches, including BRT, RF, GLM, GAM, and MaxEnt, incorporating bioclimatic and LULC i predictors to project distributions for the 2050s and 2070s under SSP2-4.5 and SSP5-8.5 scenarios. Model performance was evaluated using AUC and TSS, and integrated analyses in R and Python examined relationships among climate variability, LULC change, hydrology, and macroinvertebrate biodiversity. The result showed a complex stream network, consisting of 45 first-order, 9 second-order, and one third-order stream, and the Dinki River extended 30.35 km before joining the Awash River. The overall ecological improvement was reflected by the habitat visual assessment scores (HVAS), which improved from 10 in 2016 to 11-15 in 2023, considered as suboptimal, and the Ecosystem Health Index, which gradually increased from 1.40 in 2016 to 2.05 in 2023. The soils were mainly clay (70%) and black cotton soils (26%) and were very variable in chemical properties, such as iron (Fe) content (144.45mg/kg) and carbon/nitrogen (C/N) ratio (13.94). The hydrological analysis showed that the discharge increased significantly in the wet season (p < 0.05). From the long-term climate analysis, the annual rainfall ranged between 800 and 1000 mm, and the temperature was 18 to 21 °C. LULC analysis showed that agriculture, grazing land, and water bodies continued to be dominant land use types. Cropland, however, decreased 22.54% from 1994 to 2023, with an increase in sparse vegetation, grazing land, and water bodies. Even though there were some reductions in agricultural lands and forest ecosystems, the ecosystem service value increased from US$ 200.32 thousand in 1994 to US$ 310.33 thousand in 2023. A total of 9,479 macroinvertebrates were recorded, with more abundant numbers (6526) recorded during the dry season in 2023. Pollutionsensitive taxa were related to forested streams with high oxygen levels, while tolerant taxa, such as Chironomidae, Gomphidae, and Tabanidae, were more abundant in degraded water bodies with high EC, TDS, and turbidity levels. Multivariate analyses (PCA, NMDS and RDA) showed good site separation along environmental gradients, reflecting environmental responses at intra- and inter-annual scales. Taxon-specific responses were observed, with increases of the Heptagenidae and Perlidae associated with an increase in vegetation, while Odonata decreased with an increase in temperature. The overall water quality enhanced as evidenced by the high value of ecological indices, EPT and EOT, and the Odonata index remained stable or decreased. The macroinvertebrate communities were impacted by both change in land use and climate variability, and cumulative impacts affecting the distribution of indicator sensitive taxa in the ii Dinki watershed. The general linear model (GLM) results indicated that climate, particularly temperature, is a key determinant (especially for families Tabanidae and Dytiscidae), and combined effects with land use determined overall ecological patterns, with the Variation Partitioning Analysis (VPA) results indicating this. The developed MMI was found to be an effective discriminating index between reference and impacted sites, ranging from 10.22 (poor) to 22.43 (very good). The ensemble habitat suitability models for the Perlidae and Philopotamidae performed very well in terms of predictive performance (AUC and TSS), and they showed climate refuges in the Ethiopian highlands. The SSP5-8.5 scenario, however, suggested habitat losses of 50-59% by the 2070s, exposing a high sensitivity to climate and land use change. The Ecosystem Health Index increased from 1.40 in 2016 to 2.05 in 2023, means the Dinki Watershed under recovering, though it is highly dependent on the continued changes in the environment. The results highlight the significance of prioritizing riparian vegetation restoration and protection of forested headwater streams in order to maintain a pollution-sensitive macroinvertebrate community. This will need a coordinated approach between watershed managers, regional environmental agencies, and communities. Continued ecological monitoring, based on the developed MMI, over a longer timeframe is acceptable, and climate-based habitat projections need to be improved for use in adaptive watershed management strategies.

Evaluation of Wetland Ecological Integrity in the Fogera Floodplain, Lake Tana Sub-basin, Ethiopia

2026-09-03T05:35:07Z

Evaluation of Wetland Ecological Integrity in the Fogera Floodplain, Lake Tana Sub-basin, Ethiopia Agidie, Aklilu The Fogera floodplain is a wetland resource center hosting diverse aquatic life and livelihoods. However, natural and human-precipitated pressures threaten these assets, causing degradation and impacting wetland-based fauna and plants. The objective of the study was to assess the wetland ecological integrity condition by examining the interplay among biodiversity species composition, land cover dynamics, and ecosystem services within the Fogera floodplain in the Dilmo, Bebeks, Sendye, Shesher, and littoral wetlands. Data collection was carried out from 2022 to 2023. Different approaches were used to collect the required data. Samples of water, macrophytes, and macroinvertebrates were gathered at 20 sampling sites with volume sampling for water, quadrat methods for macrophytes, and kick-net or D-frame net methods for macroinvertebrates, respectively. Fish were collected at all wetlands using monofilament nets. Line transect and point count methods were implemented to collect the bird data. The study used various statistical tools, including mean comparisons, cluster analysis, and ordination techniques to classify sampling sites and elucidate the underlying physicochemical gradients, utilizing a range of field and laboratory tools. The Shannon-Wiener index and Bray-Curtis cluster evaluation were used to quantify species variety and compare species composition. The DPSIR framework model was utilized to look at the interactions between society and the environment, while land use changes were analyzed using Google Earth Maps. Contingent valuation and market pricing techniques were used to assess the value of wetland products. In the macrophyte investigation, a total of 55 species and 25 families were recorded from both natural wetlands and paddy fields. Dilmo Wetland had the highest macrophyte species richness (29) and Shannon-Wiener index (2.9) values. In the macroinvertebrate assessment, a total of 9 orders and 23 families were identified. The abundant genera were Hemiptera, with a mean abundance of 22.35 ± 41.01. The least common orders were Arachnida and Ephemeroptera. A total of eight fish species, namely Barbus humilis, Clarias gariepinus, Enteromius pleurogramma, Garra dembecha, Garra tana, Labeobarbus brevicephalus, Labeobarbus intermedius, Oreochromis niloticus tana were found in the wetlands. The study of birds in the Afromontane wetland ecosystem showed that there were 16,841 individuals representing 35 species, 21 families, and 13 orders. The study areas with the highest abundances were Shesher (6895) and Sendye (4354 vii individuals), respectively. Among the resident birds, the African pygmy goose (Nettapus auritus) and Maccoa Duck (Oxyura maccoa) were commonly found in the littoral of the lake. Globally threatened species like wattled cranes and black-crowned cranes were common in farming landscapes. Land cover change in the study area was primarily driven by population expansion, with wetlands and their flood vegetation losing 1,658.62 ha while cultivated land expanded to 10,950.47 ha within 32 years in the floodplain. Cluster analysis grouped sampled sites into 3 disturbance categories. Macrophyte species, particularly Digitaria sanguinalis, Phalaris paradoxa, and Echinochloa stagnina, served as animal fodder, at the same time, Cyperus papyrus, and Typha latifolia, and fish catch supported the subsistence livelihoods of society in the study area. Wetlands offer significant financial value and earnings to the society and provide vital provisioning services such as cattle fodder, water, cultivation, fish catch, food, and raw materials. The total economic value of about Birr 22,866,200.00 (US$ 408,325.00) with an average yearly income of Birr 152,441.3 (US$ 2,722.20) per household was delivered from commodities produced from the studied wetlands. To minimize the wetland degradation and to maintain the vegetation in the area, restore native vegetation, supplementary planting of multi-purpose grasses like Panicum paradoxa, papyrus, and Typha is crucial. Designating the Shesher wetland and surrounding littoral zones as protected area or as a local national park for bird sanctuary is also important.

Quality, Safety and Post-harvest Losses of Fish in Lake Tana, Ethiopia

2026-09-03T05:31:05Z

Quality, Safety and Post-harvest Losses of Fish in Lake Tana, Ethiopia on Birie, Solomon Fish are vital for food security and economic growth, but their perishable nature leads to significant quality deterioration and post-harvest loss. Additionally, improper handling and aquatic pollution can increase microbial and heavy metal contamination, posing health risks. Although salting extends shelf life and enhances flavor, the lack of standardized practices raises concerns about the quality of salted products. In Lake Tana, inadequate handling and processing of fish are reported, but data on fish proximate composition, microbial quality, heavy metal contamination, salt levels, and fishers’ knowledge, attitudes, and practices towards the safety of fish products and post harvest losses remain limited. Thus, this study was designed to address these gaps. Data were collected through laboratory analyses (proximate composition, microbial quality, and heavy metal levels), experimental studies, field observations and interviews. For microbial and proximate analyses, 75 fish samples (45 raw, 30 sun-dried) were collected from Bahir Dar, Mitsrihaba, and Gorgora sites. For heavy metal analyses, 15 equal-sized individual samples of Oreochromis niloticus were collected. To investigate the effect of different salt concentrations on fish quality, 18 kg of Labeobarbus spp. were subjected to dry salting at 10%, 20%, and 30% concentrations. To evaluate the level of fishers’ knowledge, attitudes, and practices regarding the safety of fish products, as well as to assess post-harvest losses, six fish landing sites (Bahir Dar, Nabega, Mitsrihaba, Gorgora, Delgi, and Kunzla) were selected. A total of 344 fishers were randomly interviewed at the landing sites. Proximate of fish samples revealed that sun-dried Clarias gariepinus and Labeobarbus spp. had significantly higher contents of ash, fat, protein, carbohydrates, energy, and salt compared to their raw forms. Microbial analysis showed that a significant differences (p < 0.05) in the counts of aerobic mesophilic bacteria, Staphylococcus aureus, yeast, and mold between raw and sun-dried samples. Higher counts of S. aureus, yeast, and mold were observed in the sun-dried samples, whereas aerobic mesophilic load was high in the raw Labeobarbus spp., C. gariepinus and Oreochromis niloticus samples. Additionally, total and fecal coliform counts showed significant variation between raw and sun-dried fish, with higher levels observed in the raw samples. While sun-dried samples had lower fecal coliform levels, 33.33% of dried Labeobarbus spp. and 46.67% of dried C. gariepinus still exceeded the limit. Salmonella spp. and Shigella spp. were also isolated from both raw and dry fish samples. The Pearson correlation analysis showed a strong positive correlation between water activity and vi microbial load (r = 0.756, p < 0.05), as well as between moisture content and microbial load (r = 0.786, p < 0.05). Heavy metal analysis of Oreochromis niloticus muscle tissue revealed concentrations of 0.165 mg/kg for chromium, 0.085 mg/kg for arsenic, 0.054 mg/kg for lead, and 0.010 mg/kg for cadmium. Except for chromium, the concentrations of the assessed metals were below the maximum permissible limits. The experimental study showed that both the moisture and ash content of dry-salted Labeobarbus spp. significantly changed as salt concentration increased from 10% to 30%, with ash content increasing and moisture content decreasing. However, no significant changes in fat and protein content were observed between the 20% and 30% salt treatments. The aerobic mesophilic bacteria count was 3.06 log CFU/g at 30% salt, lower than at 10% and 20%. Sensory scores for 10% salt-treated Labeobarbus spp. significantly differed from those of the 20% and 30% treatments in all attributes except color (p < 0.05). Post-harvest loss assessments revealed an annual loss of 6.32% for raw fish and 11.32% for sun-dried fish. Main causes contributing to these losses included delays in net hauling, poor handling practices, and limited market access for sun-dried fish. Although fishers showed good knowledge and positive attitudes toward safety of fish products, their actual practices remain inadequate, highlighting a gap between awareness and implementation. Therefore, it is essential to improve fishers’ handling practices, identify sources of contamination, and implement effective waste management systems to enhance fish quality and safety.

Age Determination, Stock Assessment and Reproductive Biology of Nile Tilapia (Oreochromis Niloticus, Linnaeus 1857) in Lake Hayq, Ethiopia

2026-09-03T05:25:42Z

Age Determination, Stock Assessment and Reproductive Biology of Nile Tilapia (Oreochromis Niloticus, Linnaeus 1857) in Lake Hayq, Ethiopia Berihun, Alemken The study was conducted at Lake Hayq, Ethiopia. The objectives of the study were to determine the age, stock assessment and reproductive biology of Oreochromis niloticus. For the age and growth determination of Nile tilapia (O. niloticus) samples were collected from June 8, 2022 to June 7, 2023. A total of 738 otoliths were collected from the shore, open water and river mouth for macrozone analysis. The age of the fish was determined from the total number of translucent macrozones counted in the otoliths considering the time of translucent zone formation. The collected samples ranged from 9.3 to 32 cm in total length (TL) and from 14 to 495g in total weight (TW). The sampled fish were 87.7 % ≤ 13 cm and only 12.3% were ≥ 13 cm. In the present study, the maximum life span of this species was 6 years. A strong positive relationship between otolith length and otolith weight (r 2 > 0.88) was found for O. niloticus in Lake Hayq. The relationships between total length and otolith sizes (length and length) were (r 2 > 0.92). Otolith weight correlated best with fish total weight (r 2 > 0.81) and nearly the same correlation was found between otolith length and otolith weight. The oreochromis niloticus caught in Lake Hayq reached the asymptotic length (L∞ = 31 cm) and exhibited growth rate (k) 0.90 /year, growth performance index (Ø′L =2.93) (age data), (L∞ = 31.5 cm) and growth rate (k) 0.94/year, a growth performance index (Ø′L =2.96) (length frequency data) and an exploitation rate (E) of 0.56 indicating state overfishing of O. niloticus as E > 0.5. Total mortality was 3.53 per/year, natural mortality was 1.57 per/year and fishing mortality was 1.96 per/year; this natural mortality value is considered high. Natural mortality is mainly caused by high temperatures, disease, predation, low oxygen levels, and low pH. The high natural mortality rate in the present study reflects the poor adaptability of O. niloticus to the current environment dynamics of the Lake Hayq. For the stock assessment, baseline information was collected at the fish landing site for one year. The aim of the stock assessment was to estimate the size of the O. niloticus population and the fishing mortality rate in individual length groups as well as to estimate the fish yield in the lake. The Jones length-based cohort analysis model and the Thompson and Bell length-based yield prediction model were used to estimate the number of the O. niloticus population, the fishing mortality rate and predicted yield respectively. The estimated population number of O. niloticus was over 46.8 million O. niloticus /year. According to the model’s estimates, over 13.3million O. niloticus with length of 8 to 10 cm fish arerecruited to the fishery every year at the fished part of the Lake. The estimated annual yield was 162.16 tons of O. niloticus per year from Lake Hayq. The predicted MSY was 162.19 tons/yr at fishing mortality factor of 0.9. Fishing effort should be kept at F factor of 0.7, which requires the use of136 nets/day in the lake. Total length (TL in cm), total weight (TW in g), sex ratio, maturity stages and fecundity data were collected for the reproductive biology of O. niloticus. The collected data were summarized using descriptive (percentages, graphs, tables) and inferential (Chi square, Regression) statistics use of SPSS. A total of 738 samples (422 females and 316 males) were collected during the sampling period. In Lake Hayq a significant deviation of the sex ratio (Females: Males), (1.3: 1) from the hypothesised ratio of 1:1 (X , P<0.05). The fecundity of O. niloticus ranged from 190 to 616 eggs with a mean of 328 eggs. A strong positive relationship between fecundity and body sizes (fish length and body weight) with r 2 > 0.95 was observed. The smallest mature specimen caught in the current study was 9.3 cm TL and 14 g TW. The size at first sexual maturity (L 50 ) was 11.5 cm for both females and males, which is unexpectedly low. In this study, the main breeding season of O. niloticus lasted from February to April with peak breeding season in April. To evaluated factors causing depletion of O. niloticus in Lake Hayq, a total of randomly selected 158 fishers and fishery experts from around Lake Hayq were interviewed using structured questionnaires. Most of the fishers used gillnets with a mesh size of 3.5-4 cm which is less than the national standard. Among the top five fish depletion factors mesh size of 3.5-4 cm nets is the first ranked factor for O. niloticus depletion with a relative impotence index of 0.83. Fishing during reproduction seasons is the second ranked factor with a relative impotence index of 0.79 while destruction of breeding site is the third ranked cause with a relative impotence index of 0.76. This implies that three out of the top five critical factors belong to the fishing -related category. Open access was the fourth critical severe with a relative impotence index of 0.75 and most frequently encountered factor for fish depletion in the study area. Pollution and oil discharges are the fifth most severe factor with a relative impotence index of 0.73 affecting fish depletion in Lake Hayq. Heavy fishing, illegal fishing activities, fishing during the breeding season and breeding ground, and destruction of breeding and feeding grounds are the major problems of Lake Hayq. 2