This research aimed to assess the bioindicator potential of bacterial coliforms and benthic macroinvertebrates of the Ndongo stream, an urban stream on the southeast slope of Mount Cameroon. For this purpose, macroinvertebrates were collected monthly from November 2021 to May 2022 at three sampling stations of the Ndongo stream. At each sampling station, temperature, electrical conductivity (EC), total dissolved solids (TDS), dissolved oxygen (DO), salinity, pH, flow velocity, flow rate and total coliforms were measured. Results revealed that there was a significant fluctuation in water hydrological, physico-chemical and microbiological parameters across stations (p < 0.05). Furthermore, a total of 917 macroinvertebrates were collected at the 3 stations, but their community structure differed across sampling sites. The values of the Shannon-Weaver index indicated a less diversified community with the dominance of a few species. The bacterial coliform count was above the WHO maximum acceptable concentration (i.e. 0 CFU per 100 ml) in all the sampling stations, hence compromising the use of the stream for domestic purposes. Water abiotic variables had less effect on total coliform count (R-2 = 0.54; F = 1.42, df = 11, p = 0.29). Macroinvertebrate families such as Planariidae, Gerridae, Dytiscidae, Veliidae, Nepidae, Pseudostigmatidae, Dipterocarpaceae had strong association with water abiotic variables. The study confirmed the potential use of benthic macroinvertebrates as bioindicators of water abiotic variables in tropical freshwater ecosystems.
Small-scale fisheries are central to global food security and livelihoods, yet their sustainability depends on the adoption of environmentally friendly fishing technologies (EFFTs). Understanding fishers' knowledge of these technologies is therefore critical for promoting sustainable practices and mitigating marine resource degradation. This study assessed the awareness and knowledge of EFFTs among small-scale fishers in Kivukoni, Tanzania. A structured questionnaire was administered to 105 randomly selected respondents, complemented by interviews with eight purposively selected key informants. Quantitative data were analysed using descriptive statistics, while relationships between variables were determined through chi-square tests; qualitative data were analysed thematically. The findings reveal a substantial knowledge gap, with 41.9% of respondents unaware of any of the six identified EFFTs. Although low formal education levels were prevalent among respondents, this did not fully explain-the observed knowledge disparities. Instead, limited access to financial resources, high technology costs, and the absence of structured government-led training emerged as key constraints shaping awareness and potential adoption. These findings demonstrate that knowledge gaps in EFFTs are driven by a combination of educational, economic, and institutional barriers. Addressing these challenges requires integrated interventions to enhance awareness, facilitate adoption, and promote sustainable fishing practices.
Lake Chilwa in southern Malawi undergoes periodic drying that severely impacts fisheries, aquatic biodiversity, and the livelihoods of millions. Recovery of the lake fishery depends largely on deep pools in influent rivers, which serve as critical fish refugia during lake recession. These pools are increasingly threatened by environmental degradation, unsustainable irrigation, and poor fishing practices. This study examined the role of deep pools in tributary rivers in maintaining fish biodiversity and supporting fisheries recovery during and after lake drying. Deep pools in the Likangala and Domasi rivers were mapped and assessed for productivity and species diversity between December 2018 and 2019. Baseline water quality data from 2015/16, covering dry and wet seasons at 16 sites, were analysed using standard methods, together with Environmental Water Flow assessments based on a desktop reserve model. Water quality varies by river, season, and channel type, with significantly higher concentrations of most parameters during the dry season. Hydrochemical analysis showed bicarbonate dominance, suggesting mineral denudation driven by CO2-charged runoff as the main controlling process. Clear hydrochemical gradients distinguish deep pools from open channels, confirming deep pools as chemically and biologically distinct habitats. Desktop Reserve Model results indicated that the Domasi River is in better ecological condition, while the Likangala River shows over-commitment of water resources. In both rivers, deep pools maintained fish biodiversity and acted as key refugia and breeding habitats during lake recession through maintenance of water volume at a quality amenable for fish production. However, fish biomass, productivity, and species diversity were significantly higher in Likangala River pools, reflecting their larger size and depth, higher water volumes, and better community-based fisheries management. This shows that favourable ecological conditions alone are insufficient without effective governance. Fish production rose from about 5 000 tonnes before the 2017 recession to a record 42 000 tonnes in 2024. Recovery followed flood-pulse dynamics, enhanced by cyclone-driven nutrient inputs and an extended closed fishing season. Despite this, unregulated water abstraction, catchment degradation, agricultural runoff, weak governance, and invasive species threaten sustainability. Strengthening local management, community awareness, multi-sectoral coordination, and long-term monitoring is essential to sustain fishery resilience under increasing climate variability.
Hydrobiological studies often use macroinvertebrates as bioindicators to assess river health, employing methods such as diversity assessments, species richness analyses, functional trait evaluations and biotic or multimetric indices. This study focuses on macroinvertebrate functional feeding group (FFG) assemblages in selected streams in the South-South region of Nigeria, examining their ecological roles in relation to environmental conditions. Sampling was conducted at 18 sites along 11 streams in forested areas of Delta and Edo States over a five-year period (2008-2012). A total of 52 families of benthic macroinvertebrates were identified, with notable variations in functional assemblages. Predators were particularly abundant in environments with high dissolved oxygen levels, while other FFGs, including shredders, collector-filterers, scrapers and collector-gatherers, were influenced by factors such as conductivity, phosphate levels and pH. These results underscore the significant role of environmental conditions in shaping macroinvertebrate functional structure and their potential as ecological indicators. Integrating this knowledge into biomonitoring efforts will enhance stream health assessments and inform management strategies for the conservation of forested aquatic ecosystems in southern Nigeria.
This study aimed to determine the effectiveness of drone-based autonomous systems, in combination with autonomous surface vehicles, autonomous underwater vehicles, Internet of Things systems and artificial intelligence applications, in real-time water quality monitoring. The study was performed over six months using experimental and control aquaculture ponds at the Aquaculture Research Facility in Pollachi, Tamil Nadu, India. Water quality parameters (dissolved oxygen, pH, turbidity, temperature, ammonia and nitrates) estimated using autonomous systems were compared to those monitored via conventional laboratory-based techniques. Machine learning algorithms were designed to use the assimilated data to identify and predict future anomalies and intervene. The average dissolved oxygen and pH in the experimental ponds (8.5 +/- 0.7 mg l-1 and 7.5 +/- 0.2, respectively) was much higher than that in the control ponds (6.9 +/- 1.1 mg l-1 and 7.1 +/- 0.4), and the turbidity was lower in the experimental ponds (80 +/- 10 NTU) than in the control ponds (95 +/- 15 NTU). After intervention, the dissolved oxygen levels in the hypoxic areas increased from 5.5 to 7.8 mg l-1 following aeration, indicating a 20-25% increase in 30 min, while the level of ammonia decreased from 1.2 to 0.9 mg l-1 in 24 h, indicating that the bio-remediation agents were effective. These improvements translated into an increase in fish survivability (95%) and biomass gain (25%). These outcomes show that autonomous monitoring with the help of autonomous vehicles and artificial intelligence-based decision support can help to ensure timely intervention, enhance resource utilisation and increase sustainability in aquaculture.
Tilapia are vital aquaculture species with great potential for enhancing food security in Nigeria. This study investigated the genetic diversity and species differentiation of three tilapia species (Oreochromis niloticus, Oreochromis aureus and Oreochromis mossambicus) from five rivers in the South-South geopolitical zone of Nigeria, between 5 May and 9 August 2022. Mitochondrial D-loop sequencing was used to assess genetic variation, along with morphological and meristic analyses. Major water physico-chemical parameters, including pH, conductivity, total dissolved solids and temperature, were also measured to evaluate their impact on fish performance. The results revealed robust genetic diversity, with nucleotide and haplotype diversities averaging 0.162 +/- 0.005 and 0.931 +/- 0.008, respectively, and O. niloticus showing the highest haplotype diversity (0.982 +/- 0.010). Significant genetic differentiation among species was confirmed, with a fixation index ranging from 0.550 to 0.738. Morphological assessment showed significant variations, particularly favouring O. niloticus. Water quality was strongly correlated with growth performance, with lower total dissolved solids and conductivity supporting growth. This research demonstrates the importance of integrating molecular, morphological and environmental data for effective tilapia breeding programmes, suggesting that proper management of water quality and genetic resources can enhance aquaculture practices and contribute to food security in Nigeria.
Freshwater reservoirs provide critical water supply, fisheries and ecosystem services, yet increasing anthropogenic pressures threaten their ecological integrity. This study applies a multivariate statistical and data-driven analytical framework to assess the physicochemical conditions and biological structure in Ikere Gorge Reservoir, south-western Nigeria. During the dry season, four sampling sites (A-D) were surveyed for key physicochemical parameters, including temperature, pH, dissolved oxygen, nutrients, electrical conductivity and hardness, alongside biological assemblages comprising phytoplankton, zooplankton, macrophytes and fish. The integrated dataset was analysed using principal component analysis, hierarchical cluster analysis and Pearson correlation, supported by Shannon-Wiener diversity indices and a simplified water quality index. The first two principal components explained 84.9% of the total variance, with nutrient enrichment and trophic productivity dominating the first and water quality gradients related to oxygen availability influencing the second. Sites A and D exhibited higher dissolved oxygen and transparency, whereas Sites B and C showed elevated nutrients and conductivity. Phytoplankton diversity (H ' approximate to 3.9) exceeded that of other taxa, indicating moderate ecological balance. The water quality index values (61-66) classified the reservoir as mesotrophic with fair water quality. Despite limited spatial and temporal coverage, the study provides a robust baseline for reservoir monitoring and management.
Despite ongoing biosecurity and control efforts, aquaculture intensification in the Lake Victoria Crescent has led to a persistent increase in parasitic disease occurrence in cultured Nile tilapia. Notably, different culture systems provide different habitats and environmental conditions for parasites and understanding these dynamics may provide better management strategies. We compared parasitic infection/infestation rates of cultured Nile tilapia in pond-based and cage-based farming systems and identified associations between parasite dynamics and management in the Crescent. Trichodina spp. (most prevalent and abundant) and Cichlidogyrus spp. were found in all systems. Pond systems contained >= 11 parasitic genera while <= 5 were found in cage systems. Parasite dynamics were modelled using generalised linear models with zero-inflated Poisson or zero-inflated negative binomial distributions. Surprisingly, in pond systems, adequate stocking densities and feeding were associated with an increase in Cichlidogyrus spp. abundance, while sourcing seed from fellow fish farmers was associated with a decrease in Trichodina spp abundance. For cage systems, adequate stocking densities and feeding were associated with an increase in Trichodina spp. abundance. Wild fish entry was associated with an increase in Cichlidogyrus spp. abundance while optimal stocking density was associated with a decrease in Cichlidogyrus spp. abundance. These findings highlight the interactions between seasonality and farm management in the control of parasites.
This study investigated the distribution, composition and habitat associations of freshwater eels in the Athi-Galana-Sabaki (Athi) and Ramisi Rivers using fortnightly fyke-net sampling conducted between April 2021 and March 2022. A total of 304 eels were recorded, with the Ramisi contributing 76% of individuals and the Athi River 24%. The assemblage was dominated by Anguilla bengalensis (75% of all eels), followed by A. bicolor (12%), A. mossambica (8%) and A. marmorata (5%). A. bengalensis was widespread and most abundant upstream in both rivers, indicating broad habitat plasticity. In contrast, A. bicolor and A. mossambica were largely restricted to lower, more saline reaches, while A. marmorata occurred primarily upstream. Eel biomass exceeded that of non-eel fish at most sites and differed significantly among locations, with highest values recorded in the upper Ramisi River (ANOVA: F = 2.9, p = 0.04). A one-way analysis of similarity (ANOSIM) indicated significant spatial differences in eel distribution between rivers and reaches (Global R = 0.49, p < 0.05). Subsequent SIMPER analysis showed that these differences were primarily driven by variations in A. bengalensis (6%) and A. bicolor (1.12%). Multivariate analyses revealed significant spatial structuring of eel assemblages, with occurrence patterns strongly associated with conductivity, total dissolved solids, salinity, discharge, temperature, pH, and dissolved oxygen. These findings provide the first contemporary, reach-scale assessment of WIO eels in Kenyan rivers and highlight clear species-specific habitat associations along the river-estuary continuum. Conservation and fisheries management should prioritise maintaining longitudinal connectivity, protecting estuarine transition zones, sustaining water-quality gradients, and controlling invasive species to safeguard eel populations and their ecosystem functions.
This study assessed the water quality of the Oyun River-Reservoir system, Nigeria, using an integrated Canadian Council of Ministers of the Environment Water Quality Index and Geographic Information System (GIS)-based approach (WQI-GIS). Twenty-five geo-referenced stations were sampled across eight surveys (2022-2023) and analysed against Nigerian regulatory standards. The results revealed marked spatial variability, with the river exhibiting consistently higher contamination than the reservoir. Elevated phosphate levels (3.12-19.40 mg l(-1)) and biochemical oxygen demand (2.80-7.40 mg l(-1)) were observed, while the dissolved oxygen (0.05-1.90 mg l(-1)) was critically low. Heavy metals, particularly Cd and Pb, exceeded regulatory limits. Water quality index scores classified most river sites as 'poor' to 'very poor' (22.3-47.35), whereas reservoir sites ranged from 'marginal' to 'good'. GIS-based hotspot analysis identified severe pollution clusters in midstream river sections and upstream reservoir zones. Significant correlations between land-use and water quality parameters were observed; for instance, between built-up areas and Cu (r = +0.68) and between forested areas and biochemical oxygen demand (r = -0.80), highlighting the buffering role of forests and vegetation. In summary, the WQI-GIS approach identified pollution gradients and management priorities, highlighting the need for strengthened catchment control, improved sanitation and stricter land-use regulations to protect the Oyun freshwater system.
We aimed to assess the physico-chemical properties and heavy metal concentrations of borehole water across five functional areas within three restricted military formations and compare them with those of nearby civilian control sites in Makurdi, Nigeria. In total, 18 composite boreholes were sampled. The measured parameters included pH, electrical conductivity, total dissolved solids, dissolved oxygen, biochemical oxygen demand, hardness, major cations (K+, Mg2+ and Na+) and heavy metals (As, Cd, Pb and Hg). Compared to the control sites, Military Formation A exhibited significantly higher biochemical oxygen demand and turbidity, particularly in the Workshop and Residential areas, with the first principle component demonstrating strong synergy between domestic effluent and metal loadings. Military Formation C exhibited the highest levels of mineralisation (electrical conductivity, total dissolved solids and hardness), particularly in the Residential and Office areas, while Military Formation B maintained superior water quality, characterised by high dissolved oxygen and an alkaline pH, particularly in the Mammy Market and Office areas. Borehole water in the military installations was generally superior to adjacent civilian sites owing to controlled land use. However, localised hotspots in School and Workshop areas remain vulnerable to organic loading and geogenic As mobilisation, necessitating zone-specific remediation.
This study aimed to assess the water quality in the lakes of Yaound & eacute;, Cameroon, for environmental monitoring and human health. The water quality of two lakes were measured and statistical analyses of obtained data revealed an average temperature value of 28.8 +/- 0.59 and 26.63 +/- 0.38 degrees C, pH of 7.09 +/- 0.23 and 7.47 +/- 0.24, oxidation-reduction potential (ORP) of 186.2 +/- 33.05 and 90.72 +/- 69.31 mV, resistivity (rho) of 283.18 +/- 45.56 and 40.17 +/- 1.64 K Omega, electrical conductivity (EC) of 50.4 +/- 6.38 and 341 +/- 13.17 mu S cm-1, and total dissolved solids (TDS) of 25.6 +/- 2.88 and 170.45 +/- 6.48 ppm in Minkoameyos and Municipal lakes respectively. Dihydrogen (H2), salinity (S), specific gravity (SG) and nutrient fertility (NF) of the water gave constant values during all measurements. While some measured parameters indicated that the water in these lakes was suitable, the water quality index for Minkoameyos Lake was 74 indicating that the water was poor and that of Municipal Lake was 88 indicating that the water quality was very poor. The overall assessment of this study indicates that the water from both lakes is useful for agricultural irrigation and industrial use but requires a lot of treatment prior to human consumption.
The body condition metrics and reproductive aspects of three spiny eel species (Mastacembelus moorii, M. ellipsifer and M. cunningtoni) inhabiting littoral habitats in southern Lake Tanganyika were evaluated. As Mastacembelids are important in artisanal fisheries, the study aimed to provide essential baseline data (growth, condition, fecundity) for understanding the ecological roles and conservation needs of Mastacembelids in Lake Tanganyika, to mitigate the risks of recruitment overfishing and aid in their long-term viability. Data were collected between November 2023 and March 2024. Biometric parameters (total length, weight and organ weights) were analysed for condition factors and organosomatic indices. Results revealed length-weight relationships indicating isometric growth across all species, with slight species-specific differences in Fulton's condition factor and the hepatosomatic and cardiosomatic indices. Female sexual maturity was assessed in relation to the gonadosomatic index; a 1% gonadosomatic index threshold could effectively discriminate between mature and immature individuals. Fecundity curves predicted egg number from maternal total length. Mature M. cunningtoni females showed the highest fecundity for maternal body-size. Notably, M. moorii showed indications of asynchronous egg release, warranting further investigation. Mastacembelids face numerous anthropogenic pressures and these results contribute information relevant to the incorporation of these species in sustainable fisheries management plans.
Diatom-based indices are widely used for freshwater bioassessment, yet methodological variability, particularly in count strategies, can influence ecological classification outcomes. This study compares a traditional fixed count (FC) approach with an observed/expected taxa (OE) strategy across five riverine sites in the Eastern Cape, South Africa. A total of 230 diatom taxa were identified. Comparisons between the two approaches revealed statistically significant differences in some ecological status classifications, although both methods captured similar spatial trends across the study area. The OE approach required counting fewer valves per sample, reducing analysis time without compromising assessment accuracy. While the OE taxa approach may provide a time-efficient alternative to FC methods, the differences detected between methods underscore the need for a critical evaluation of their limitations and further testing before routine application.
Artificial barriers in freshwater ecosystems may hinder fish movement by altering their habitat and fragmenting rivers. We assessed the impact of anthropogenic structures on river connectivity in Pietermaritzburg, KwaZulu-Natal, South Africa. We mapped the barriers on eight watercourses using the Adaptive Management of Barriers in European Rivers (AMBER) 'Barrier Tracker' application between 2021 and 2022. We logged different types of instream obstacles, recorded their description, and uploaded photographs. We found that the Wilgerfontein and Dorpspruit streams had a higher density of barriers per kilometre stretch and greater disconnectivity in their longitudinal waterways. Culverts were the main cause of disconnectivity and the most abundant after structures categorised as 'other', mainly road bridges. The number of barriers in the Dorpspruit, Wilgerfontein streams and the uMsunduze River were similar, although the assessed lengths differed. The uMsunduze is the main stream and is four times longer than either the Dorpspruit and Wilgerfontein lengths as the two longest tributaries assessed. The high number of instream barriers, particularly dysfunctional culverts, needs to be mitigated. Removal of some instream barriers, installation of fishways, and the upgrading and maintenance of other instream structures can improve river connectivity. Poor river connectivity impedes the persistence of the freshwater fauna in these rivers, especially those that migrate seasonally.
Changes in composition, abundance and distribution of macrofaunal assemblages are subject to environmental influences. However, the effects of ecological disturbance on mangrove habitats in Cameroon have not been sufficiently studied with regard to macrofaunal assemblages. This work aims to identify the macrofauna assemblages in the Kribi area and determine the relationship between species distribution and some environmental factors. Between March and November 2020, a collection of crabs and molluscs was carried out in parts of Kribi. Simultaneously, several heavy metals (Cu, Zn, Cd, Pb, Al and Fe) and groundwater temperature, salinity, pH, conductivity, TDS and dissolved oxygen in the sediment were analysed. The macrofauna assemblage consisted of 27 species, including 15 crab species and 12 mollusc species. Hemisinids and Sesarmids were the most abundant with four species and six species respectively. The Shannon-Weaver index (H-y < 3) indicated a high level of pollution in the mangroves studied. With regard to environmental parameters, there is a highly significant difference in macrofauna assemblage structure between the six stations (PERMANOVA, F = 20.126, p = 0.001). Macrofaunal diversity and abundance reflect the dynamics of the mangrove ecosystem and act as indicators of habitat change.
