West African Journal of Applied Ecology

Comparative Studies of Proximate and Mineral Composition of Fresh and Smoked Clarias gariepinus, oreochromis niloticus, and Bagrus bayad from River Rima, Nigeria

I. M. Imam — 2025-12-01

This study assessed the proximate and mineral composition of three commercially important freshwater fish species Clarias gariepinus, Oreochromis niloticus, and Bagrus bayad collected from River Rima, Sokoto State, Nigeria. Both fresh and smoked samples were analyzed to determine the effects of processing on their nutritional quality. Proximate analysis included the determination of moisture, crude protein, lipid, ash, and crude fiber contents, while mineral composition (sodium, potassium, calcium, magnesium) was quantified using Atomic Absorption Spectrophotometry. Phosphorus was determined using the procedure of Phosphorus, Inorganic kits “Spectrum- Diagnostics, Germany IFUFCC34”. Results indicated that proximate composition varied significantly among species and between treatments. Moisture content decreased considerably after smoking, while protein levels increased, with smoked Clarias gariepinus recording the highest protein value (45.30%). Lipid content was generally higher in Oreochromis niloticus, whereas ash was more concentrated in smoked samples. Mineral analysis revealed species-specific differences, with smoked fish exhibiting higher concentrations of calcium and phosphorus, enhancing their dietary value. The increase in nutrient density due to smoking also suggests improved preservation and extended shelf life. These findings underscore the nutritional significance of these freshwater fish species and highlight the role of traditional processing in improving food quality, supporting both dietary needs and policy initiatives for small-scale fisheries and food security in the region.

Contrasting effects of Corn cob and Cocoa pod husk biochars on Heavy metal Bioavailability, Speciation, and Uptake by Maize in a Mining-Contaminated soil

J. K. Essibu — 2025-12-01

Soil contamination by heavy metals (HMs) poses substantial risks to agricultural productivity and environmental health. Biochar, a carbon-rich material produced from organic waste, has been proposed as a soil amendment to lower HM bioavailability and enhance soil fertility. This study assessed the effects of cocoa pod husk biochar (CPHB) and corn cob biochar (CCB) on the bioavailability, speciation, and uptake of HMs (Cd, Cu, and Pb) by maize (Zea mays L.) in contaminated agricultural soil. A 60-day greenhouse experiment was conducted with biochar application rates of 1%, 2%, and 3% (w/w) at 70% field capacity. Soil properties such as pH, soil organic carbon (SOC), and cation exchange capacity (CEC) were analyzed before and after the experiment. HM bioavailability and speciation were determined using sequential extraction methods, while metal accumulation in maize roots and shoots was measured to calculate the bioconcentration factor (BCF) and translocation factor (TF). Biochar amendments raised soil pH, CEC, and SOC, with the most notable improvements observed in CPHB at 3%. The proportion of exchangeable HM fractions decreased relative to total content (Cd: by 5.12%, Cu: by 4.88%, Pb: by 3.89%), while residual fractions increased (Cd: by 58.14%, Cu: by 60.24%, Pb: by 52.11%), particularly at 2% and 3%. HM accumulation in maize roots and shoots significantly declined, with CPHB at 3% showing the greatest reduction. Correspondingly, the application of CPHB at 3% led to a decrease in BCF and TF values for Cd, Cu, and Pb, indicating diminished metal uptake by maize roots and limited translocation from roots to shoots. These findings suggest that CPHB, especially at a 3% rate, effectively reduces HM toxicity and bioavailability while promoting soil fertility, thus offering a promising strategy for remediating soils affected by mining activities.

Water Management, Nitrogen rate and Plant spacing effect on Yield and Yield components of Rice

J. K. Essibu — 2025-12-01

A study was conducted on a calcic vertisol to evaluate the main effects of water management, nitrogen (N) rate and plant spacing and their potential interactions on yield and yield components of rice. The experimental design was a split-split plot with two water treatments as main plots. Continuous flooding (CF) involved repeated ponding to 5 cm height and alternate wetting and drying (AWD) involved ponding to a height of 5 cm after the water level dropped to 25 cm beneath the soil surface. Nitrogen at 0, 90 and 120 kg N ha^-1 served as subplots and three plant spacing (20 × 15 cm, 20 × 20 cm and 20 × 25 cm) as sub-subplots. The experiment was conducted during the major and minor rainy seasons over two years. A similar panicle density and grain yield was observed between AWD and CF, though AWD was characterized by a reduction in irrigation water used. This resulted in higher water productivity under AWD (0.284-0.899 kg m^-3) relative to CF (0.257-0.810 kg m^-3). Applying AWD saved between 9.5-11.3 % water relative to CF. There was no yield advantage for 120 kg N ha^-1 over 90 kg N ha^-1. There was no interaction between N rate and water management, suggesting that the effect of N rate was consistent regardless of the water management method. The rice plant did not sufficiently compensate for lower plant population in the minor rainy season compared with the major rainy season. As a result, the lower plant population (20 × 20 cm plant spacing) recorded lower yield than the higher plant population (20 × 15 cm plant spacing) in the minor rainy season. This also indicates that complete yield compensation is difficult or not guaranteed during the minor season at 20 × 20 cm plant spacing. Yield components were higher in the major rainy season resulting in higher yield in the major rainy season (3973 kg ha^-1) than the minor rainy season (3550 kg ha^-1). Therefore, establishing fields at 20 × 15 cm during the minor rainy season is recommended to increase tiller density to eventually increase or maintain yield. Also, employing AWD and applying N at 90 kg ha^-1 can help farmers save water, avoid excessive N use and save cost.

Incidence, severity and characteristics of Ralstonia solanacearum species complex in greenhouses in Southern Ghana

N.Y. Sarfo — 2025-12-02

Tomatoes are important component in Ghanaian diets, but bacterial wilt disease has become a major threat to the production of this high value vegetable. Consequently, relevant stakeholders over the past decade have sited greenhouses in the South of the country to boost tomato production, with some operators reporting wilt symptoms of tomato in their greenhouses. This study was therefore conducted with the aim of determining incidence and severity of the bacteria wilt disease of tomato; isolate causal organism from diseased tissues, establish sources of the bacteria inoculum in greenhouses and characterize isolates using morphological, biochemical and molecular techniques. Koch's postulate was also carried out on the isolates. Bacteria wilt disease was recorded in 12 out of 54 greenhouses surveyed. Incidence and severity of the disease within greenhouses ranged from 5.9%-18.5% and 0.5 – 1.2, respectively. Ralstonia solanacearum species complex was confirmed through streaming, morphological and biochemical tests. Strains of Phylotypes I and III (now R. pseudosolanacearum) were determined by multiplex polymerase chain reaction. Sources of bacteria inoculum in the greenhouses were found to be irrigation water and the growth substrate used. Koch's postulate was fulfilled. Accurate diagnosis of the pathogen is a major step towards developing effective disease management tools in the country and beyond.

Land use and land cover dynamics and the associated drivers in the Volta Delta, Ghana

J. Ayamga — 2025-12-02

Knowledge of the drivers of land use and land cover change (LULCC) is critical for explaining and managing change, yet, this has received a limited research focus. We analysed LULCC and associated drivers in the Volta Delta using geoinformation technologies and multinomial logistic regression based on 2002 and 2017 Landsat data. Explanatory factors considered were elevation, slope, population density, distance to road, distance to settlement, annual rainfall, and crop yield. Results showed 2.82% net gain in active croplands. Water and riverine vegetation experienced net increases of about 1.00% each. Grass savannah, mangrove, shrub savannah and thicket experienced net losses. Low-lying and highly accessible areas experienced intensified agricultural activity, whereas elevated terrains with sparse road networks retained more natural vegetation. These results highlight the strong influence of accessibility, geomorphology and human activity on land transformation in the Volta Delta. The study demonstrates that integrating multisource spatial data with statistical modeling provides an effective framework for quantifying and explaining LULCC dynamics. The findings have important implications for land-use policy, environmental monitoring and adaptive resource management. Strengthening participatory spatial planning, promoting climate-smart agriculture, and integrating elevation and flood risk mapping into policy frameworks areessential for balancing agricultural productivity with ecological conservation in deltaic landscapes.

Two Decades of Land Use and Land Cover Dynamics: Assessing the Ecological Status of the Sakumono Ramsar Site, Ghana

J. Quaicoe — 2025-12-02

The ecological status of the Sakumono Ramsar Site in Ghana has been significantly affected by rapid urbanization and land-use transformation over the past two decades. This study analyzes the patterns and trends in Land Use Land Cover (LULC) changes across the years 2000 to 2023, focusing on four main habitat types: Built-up, Floodplain, Vegetation, and Water. Using Landsat imagery and GIS tools, LULC changes were quantified through a supervised classification approach, validated with an accuracy assessment yielding overall accuracies of 89.13% (2000), 97.5% (2010), and 100% (2023). Further ecological analysis was conducted using the Normalized Difference Vegetation Index (NDVI) and Modified Normalized Difference Water Index (MNDWI). The results indicate that the Built-up area increased dramatically from 1.06% in 2000 to 45.26% in 2023, largely due to urban expansion from nearby Accra and Tema municipalities. Concurrently, Floodplain areas decreased from 82.22% to 21.72%, Water areas dropped from 5.62% to 2.02%, and Vegetation areas increased from 11.10% to 30.99%. These substantial changes severely compromise wetland functions. Despite national and international frameworks like the Ramsar Convention, enforcement has been minimal, and community-based initiatives have struggled with sustainability. This study underscores the urgency for active community involvement and robust stakeholder collaboration to preserve the Sakumono Ramsar Site's ecological health, highlighting the urgent need for sustainable mitigation efforts for the adverse impacts of urbanization and restore the ecological integrity of this crucial wetland ecosystem.

Toxicity and Human Health Risk Assessment of Heavy Metals in the sediments of the Korle Lagoon Using Fish Bioassay

R. Osae — 2025-12-02

This study evaluated the toxicity of sediments from the Korle Lagoon, a heavily polluted water body, by assessing the bioaccumulation of heavy metals in Sarotherodon galilaeus through a 10-day fish bioassay. Sediment heavy metal concentrations were analyzed using USEPA Method 3050B, while heavy metals in fish tissues were assessed before and after exposure using USEPA Method 200.11. The results revealed an alarming mortality rate of 90–100% in fish exposed to the sediments, compared to only 10% in the control group. This high mortality correlated with elevated heavy metal concentrations in the sediments. The geoaccumulation index of heavy metals in sediments showed that the Korle Lagoon is moderately polluted with Cd (0-1.85), Pb (0.37-1.56) and Zn (1.14); moderately to strongly polluted with As (0.03-2.88); and extremely polluted with Fe (9.90-13.10). Post-exposure analysis showed significant accumulation of heavy metals in fish tissues, with recorded concentrations of Cu (103.75 mg/kg), Cd (0.31 mg/kg), As (13.95 mg/kg), Cr (16.02 mg/kg), Ni (7.97 mg/kg), Pb (5.83 mg/kg), and Hg (0.72 mg/kg). Most values exceeded WHO guideline limits, except for Ni and Cd. The estimated hazard index values for adults (328.52) and children (191.63) suggest a severe risk of non-carcinogenic health effects from consuming exposed fish. Additionally, lifetime cancer risk values (LCR > 0.0006) indicated potential carcinogenic threats. These findings confirm the toxicity of Korle Lagoon sediments and highlight significant ecological and public health risks, particularly for local communities dependent on fish from the lagoon as a dietary staple. Urgent mitigation measures are necessary to address heavy metal contamination and protect aquatic and human health.