Tropical Freshwater Biology

Temporal variation in water quality of selected earthen ponds of Effurun, Delta State, Nigeria

2025-10-28T17:43:34+00:00

This study assessed the temporal variations in water quality parameters in six earthen ponds in Effurun, Delta State, Nigeria, over six months, focusing on aquaculture suitability. pH remained stable (6.47–6.87) within NESREA standards (P > 0.05). Electrical conductivity (455.13 ± 207.11 µS/cm) and total dissolved solids (264.50 ± 102.20 mg/l) were below regulatory limits but increased significantly by June due to seasonal effects (P < 0.05). Turbidity (108.19 ± 44.09 NTU) and Total suspended solids (80.71 ± 44.40 mg/l) exceeded NESREA limits, peaking in April and February, likely due to sediment resuspension (P < 0.05). Potassium (0.67 ± 0.20 mg/l) and Alkalinity (20.42 ± 8.97 mg/l) showed moderate variations (P > 0.05), while Salinity (0.21 ± 0.08 g/L) and Sulfate (67.01 ± 13.84 mg/l) remained within acceptable limits (P > 0.05). Dissolved oxygen (6.14 ± 1.06 mg/l) met aquaculture requirements, and Biochemical oxygen demand (3.53 ± 1.07 mg/l) indicated low organic pollution (P > 0.05).Heavy metal concentrations exhibited no significant seasonal variations (P > 0.05). Iron ranged from 10.23 to 10.71 mg/l, Arsenic remained at 0.03 mg/l, and Cadmium varied slightly (0.32–0.33 mg/l). Nickel and vanadium were undetectable, while Barium (0.07 mg/l), Cobalt (0.02 mg/l), Chromium (0.11 mg/l), and Manganese (0.07 mg/l) showed minimal fluctuations. Zinc declined from 0.13 mg/l in January to 0.09 mg/l in March before stabilizing. Lead (0.03 mg/l) and Selenium (0.05–0.06 mg/l) remained stable.These findings highlight seasonal influences on some parameters but overall stability in heavy metal concentrations, underscoring the need for continuous monitoring to support sustainable aquaculture.

Evaluating the impact of flood events on the water quality of Ethiope River: A comparative study of wet and dry seasons

2025-10-28T17:48:23+00:00

The quality of water in the Ethiope River was assessed across three stations to evaluate the impacts of flooding and anthropogenic pollution. Physico-chemical parameters including pH, dissolved oxygen (DO), biochemical oxygen demand (BOD), electrical conductivity (EC), total dissolved solids (TDS), nitrate, phosphate, and heavy metals were measured. Station 1, located upstream, exhibited minimal contamination, with water quality parameters largely within WHO (2011) guidelines, reflecting a relatively pristine environment. In contrast, Station 2, situated at the flood discharge point, showed significant pollution, marked by elevated BOD, nitrate, phosphate, and EC, indicative of contamination from agricultural runoff and urban wastewater. The Water Quality Index (WQI) at Station 2 was the highest, highlighting severe water quality degradation. Station 3, downstream, displayed partial recovery, with improved BOD and EC levels, although phosphate and nitrate concentrations remained elevated. The seasonal variation in water quality was significant (P<0.05), with wetter conditions exacerbating nutrient loading and organic matter input, while the dry season showed some attenuation. These findings suggest that the Ethiope River is subjected to both natural and anthropogenic stressors, with flood events intensifying pollution levels, especially at Station 2. The river’s ability to self-purify downstream was evident, though continuous pollution sources upstream led to ongoing contamination. This study contributes to understanding the impact of flooding and pollution on water quality in tropical rivers, providing insights into the resilience and challenges faced by river ecosystems in flood-prone regions.

Nutritional composition of water hyacinth diets for fish

2025-10-28T17:52:20+00:00

The rising cost and limited availability of conventional feed ingredients such as fishmeal pose a significant challenge to sustainable aquaculture, especially in developing countries. This study investigated the potential of water hyacinth (Eichhornia crassipes), an invasive aquatic plant, as a costeffective alternative in fish diet formulations. Five experimental diets were formulated by progressively replacing fishmeal with water hyacinth leaf meal at 0%, 25%, 50%, 75%, and 100% inclusion levels, respectively. Proximate analyses were conducted to determine moisture, ash, crude protein, crude fibre, lipid, and carbohydrate contents using standard AOAC methods. Results showed that water hyacinth inclusion significantly influenced the nutritional profile of the diets. Diets with higher water hyacinth content exhibited increased ash and crude fibre levels, indicating a rich mineral composition and high fibre potential. However, crude protein content decreased with higher inclusion levels of water hyacinth, with the highest protein value recorded in the fishmeal-based diet. Lipid levels were generally low across all treatments, particularly in diets with high water hyacinth proportions. Carbohydrate content remained moderately stable across all formulations, with a slight increase in the highest inclusion level. The study concludes that water hyacinth possesses promising nutritional attributes that could complement traditional fishmeal, particularly as a mineral and fibre source. However, its low protein and lipid contents may limit its use as a sole feed ingredient. Therefore, its optimal application lies in partial replacement strategies that balance nutritional adequacy with cost-effectiveness. This work highlights the potential for converting an ecological burden into a valuable input in sustainable aquaculture feed development.

Effects of different levels of water exchange on the growth performance, survival and haematology indices of Clarias gariepinus

2025-10-28T17:58:59+00:00

Water determines the success or failure of an aquaculture operation to a greater extent. During dry season and regions with low accessibility to water, productivity tends to be reduced. This study determined the effect of different levels of water exchange required for producing African mud catfish. One hundred and eighty Clarias gariepinus (2.69±0.94 g fish^-1 ) were randomly distributed at 15 fish per tank into four treatments with three replicates. Each treatment was named according to the daily water level renewal, namely; T₀ (Complete renewal), T₁ (Quarter renewal), T₂ (Half renewal) and lastly, T₃ (three-quarters renewal). The experiment lasted eight weeks, twice daily feeding with commercial feed at 5% body weight. No significant differences recorded in the water quality parameters of all the treatments. However, T₂ had the highest final weight of 52.06±1.01g and weight gained 6.73±3.96 g. T₂ retained the highest specific growth rate (6.01±1.42 g day^-1 ). The most increased FCR was recorded in T₀ (0.64±0.30). All the treatments had high survival at the end of the experiment, with the highest value (90-100 %). The result showed that PCV and haemoglobin were significantly (P<0.05) higher in T₂ (31.00±0.0 % and 10.30±0.0 g/dl) and T₁ (31.00±1.41 % and 10.50±0.7 g/dl). Red blood cell was significantly higher in T₀ (2.15±0.07). This study showed that the daily water exchange to half the water level volume produced the best result in terms of growth performance. This is optimum and affordable for growth and health of Clarias gariepinus fingerlings production.

Acute toxicological effects of Z-germicide on the aquatic beetle Orectogyrus bedeli

2025-10-28T18:04:29+00:00

Z-germicide, a phenolic disinfectant released into aquatic environments through industrial, agricultural, and domestic effluents, poses significant ecological risks. Although its toxicity to vertebrates is relatively well studied, little is known about its effects on aquatic insects that perform vital ecological functions. This study investigated the acute toxicity of Z-germicide on the whirligig beetle Orectogyrus bedeli Regimbart, 1884, by determining median lethal concentrations (LC₅₀) over different exposure periods. Laboratory bioassays were conducted at 20–22 °C, where beetles were exposed to graded concentrations of Z-germicide. Mortality was recorded at 24, 48, 72, and 96 hours, and LC₅₀ values were calculated using probit analysis. Water quality parameters, including dissolved oxygen, pH, conductivity, and total dissolved solids, were also measured. Results showed declining LC₅₀ values with increasing exposure time: 47.846 mg/L at 24 hours, 36.7891 mg/L at 48 hours, 8.670 mg/L at 72 hours, and 7.769 mg/L at 96 hours. Mortality followed a clear concentration and time-dependent trend. Conductivity and total dissolved solids increased significantly, while dissolved oxygen and pH remained relatively stable. These findings demonstrate the acute toxicity of Z-germicide to O. bedeli and highlight the ecological risks posed by phenolic pollutants. Effective pollution control and wastewater management are essential to protect aquatic biodiversity.

Macrophytes distribution in relation to sediment composition of Kandola Shella Stream Sokoto, Nigeria

2025-10-28T18:07:39+00:00

Macrophytes play a vital role in aquatic ecosystems, serving as indicators of environmental health and influencing nutrient cycling. Kandola Shella Stream of Usmanu Danfodiyo University, Sokoto is a unique ecosystem for studying these relationships in a semi-arid region. This study aimed to evaluate macrophyte diversity in relation to sediment composition within the Kandola Shella Stream. The stream was divided into three locations (A, B, and C) for the study. Field surveys and standard laboratory procedures were conducted to identify macrophytes species and examine sediment physicochemical properties. A total of 17 Macrophytes species from 11 families were identified. Emergent species dominated the stream, accounting for 53% of all observed species. At location A, Pistia stratiotes was most abundant, while Nymphaea lotus and Panicum hemitomen dominated at location B. At location C, Azolla pinnata was the predominant species. Sediment analysis revealed slightly acidic conditions across all sections, with pH values ranging from 6.53 to 6.62. Electrical conductivity (EC) was highest at location A, reflecting potential variations in ion concentrations. Nutrient analysis showed fluctuations in nitrogen, phosphorus, and potassium levels across the sections. Heavy metal concentrations revealed consistent cadmium levels, with elevated copper and lead concentrations observed at location A. Macrophyte distribution in Kandola Shella Stream was strongly influenced by sediment composition, emphasizing the role of sediment in shaping aquatic vegetation and this type of study will support ecosystem management and conservation efforts.

Heavy metals in water and Macrobrachium prawns from the Benin River, Nigeria

2025-10-28T18:13:06+00:00

Water is the most vital natural resource, sustaining all life forms. Any alteration in its quality can disrupt ecological balance and render it unsuitable for use. Prawns, positioned delicately in the aquatic food chain, can bioaccumulate heavy metals at levels that may pose health risks to consumers. This study evaluated the concentrations of heavy metals (Fe, Zn, Cu, Pb, Cd, and Cr) in the prawns, Macrobrachium macrobrachion and M. vollenhovenii, and the physicochemical characteristics of water from the Benin River. Samples were collected monthly from four stations between October 2018 and May 2019. Physicochemical parameters, including temperature, pH, electrical conductivity (EC), salinity, turbidity, total suspended solids (TSS), total dissolved solids (TDS), dissolved oxygen (DO), biochemical oxygen demand (BOD), chemical oxygen demand (COD), and major ions were determined using standard methods, while heavy metals were analyzed by atomic absorption spectrophotometry. Data were processed using descriptive statistics, unpaired t-tests, and ANOVA (SPSS). Most parameters were within WHO/FMEnv limits, except EC, chloride, TDS, Fe, Pb, and Cd. Apart from pH and vanadium, seasonal variations were not significant (P > 0.05). Heavy metals in prawns were within permissible limits, with no significant seasonal differences. Estimated Daily Intake (EDI) values were below regulatory thresholds, while Target Hazard Quotient (THQ) values were < 1, indicating negligible non-carcinogenic risks. The Hazard Index (HI) also remained < 1 throughout the study. These findings suggest that prawns from the Benin River are currently safe for consumption, though increasing anthropogenic pressures could elevate future risks. Given their nutritional and economic importance, routine monitoring of prawns and aquatic systems is recommended to safeguard public health and ensure sustainable resource use.