Department of Fisheries and Aquatic Science

MACROINVERTEBRATE ASSEMBLAGES AND BODY SIZE DISTRIBUTION IN RESPONSE TO LAND-USE CHANGES IN HEADWATER STREAMS OF THE SONDU-MIRIU RIVER BASIN, KENYA

2026-06-08T13:04:50Z

MACROINVERTEBRATE ASSEMBLAGES AND BODY SIZE DISTRIBUTION IN RESPONSE TO LAND-USE CHANGES IN HEADWATER STREAMS OF THE SONDU-MIRIU RIVER BASIN, KENYA KULUO, GIDEON Assemblages of aquatic macroinvertebrates have spatial and temporal variations in structure in response to environmental changes of their habitats, such as streams and rivers. Taxonomic approaches for monitoring the ecological status of aquatic ecosystems using macroinvertebrate assemblages face several limitations, creating a need for ataxonomic methods that are valid, disturbance-sensitive, and cost-effective for freshwater monitoring. This study evaluated the influence of seasonality and land-use changes on macroinvertebrate assemblage structure and water physico-chemical parameters of headwater streams of the Sondu-Miriu River basin, Kenya. Additionally, the study evaluated the utility of macroinvertebrate size-spectrum metrics and abundance-biomass comparison (ABC) curves as ataxonomic methods of evaluating land-use influence on the river’s ecological condition. Macroinvertebrate taxonomic abundance (individuals/m2), wet weight (mg), and physico-chemical variables were measured during the wet and dry seasons in March and September 2024, respectively, from 24 headwater streams distributed across four land-use types: natural forest (NF), tea and tree plantations (TTP), smallholder tea (SHT), and smallholder agriculture (SHA). Results based on water quality showed turbidity, total suspended solids (TSS), total dissolved solids (TDS), electrical conductivity (EC), particulate organic matter (POM), and nitrate (NO3 - -N) identified streams in NF as least disturbed and in SHA as most disturbed; TTP and SHT streams were intermediate in water quality. Taxon richness, diversity, and Ephemeroptera, Plecoptera, and Trichoptera (EPT) indices indicated land-use specific influences on assemblage structure. Redundancy analysis (RDA) showed thatsmall-bodied taxa (<8 mg wet weight) were associated with high disturbance indicators, while large-bodied taxa (>32 mg) were associated with low disturbance indicators and sites. Slopes (λ) of normalized abundance- and biomass-based size-spectrum (a measure of trophic transfer efficiency) deviated from theoretical steady-state conditions (λ=-2.0 and -1.0, respectively), indicating that the sites were disturbed, but the slopes did not vary significantly between land uses or seasons, suggesting size-spectrum slopes had low sensitivity to land-use-based changes in water quality. In contrast, size-spectrum midpoint heights (a measure of ecosystem production) differed significantly between sites, highest at SHT and NF and lowest at SHA and TTP streams. Spectrum midpoint heights were, therefore, more responsive to disturbance than slopes, highlighting their potential as indicators of land-use influence on the Afrotropical streams. Although the ABC curves indicated undisturbed conditions for all sites, Warwick’s (W) statistics revealed subtle differences among streams, suggesting variation in local-scale ecological conditions. This study demonstrated that catchment land use significantly influences water quality and macroinvertebrate assemblages in headwater streams of the Sondu-Miriu River basin. Traditional metrics (%EPT and diversity indices) are useful indicators of land use-based disturbance, while size-spectrum midpoint heights are potentially useful ataxonomic indicators of disturbance in the studied streams. It is recommended to integrate both community indices and functional metrics (especially midpoint height) into stream biomonitoring as complementary method for evaluating the ecological status of headwater streams. Management efforts should prioritize riparian buffers and nutrient/sediment control in SHA areas of the basin, while conserving less-impacted NF sites as reference areas. Long-term and broader spatial-scale studies are needed to validate the stability of size-spectrum metrics and ABC curves as rapid tools for monitoring the ecological status of headwater streams in response to anthropogenic influences.

THE EFFECT OF EBB-AND-FLOW TECHNOLOGY, SUBSTRATE TYPES AND SALT-TOLERANT CROP (Apium graveolens L.) ON NUTRIENT REMOVAL FROM A BREWERY EFFLUENT

2026-06-08T12:18:35Z

THE EFFECT OF EBB-AND-FLOW TECHNOLOGY, SUBSTRATE TYPES AND SALT-TOLERANT CROP (Apium graveolens L.) ON NUTRIENT REMOVAL FROM A BREWERY EFFLUENT OBADO, ELIZABETH Brewing industries face economic and environmental challenges of water use, energy consumption, and effluent disposal. The limited water availability and strict effluent discharge regulations in the South African Brewery justify wastewater treatment and recycling. Constructed wetland (CW) design and operation have been optimised for sustainable wastewater treatment. An ebb-and-flow technology is a CW design that creates aerobic and anaerobic conditions essential for wastewater treatment. South African Ibhayi Brewery effluent is treated onsite using a commercial-scale anaerobic digester (AD) and activated sludge units. However, the anaerobically digested effluent has high treatment costs and does not meet the environmental discharge standards. Therefore, the post-AD effluent is further treated using a low-cost CW technology. This study investigated the effect of ebb-and-flow CW operation, substrate types and celery plant growth on nutrient removal from a post-AD brewery effluent. Two experiments were conducted; Experiment 1 examined the effect of retention times (10, 20 and 40 minutes) and gravel sizes (7, 13, and 19 mm) on nutrient removal. The retention times (RT) and gravel sizes were allocated as treatment combinations and replicated thrice in a completely randomised design. In the second experiment, an ebb-and-flow CW was used to investigate the effect of media types planted with a celery crop on nutrient removal. Eight media (clay pebbles, clay bricks, sand, bioballs, recycled plastic, and gravel sizes), either alone or mixed, were tested. A 2:1:1 ratio of each media, pine bark and granular activated carbon, respectively, was used for mixed treatments. A uniform celery planting density of eight seedlings per m 2 and a 12-minute effluent retention time were used. Results for experiment 1 indicated significant differences at p≤ 0.05 between RT and gravel size treatment combinations on nutrient removal. The 10-minute RT at 19-mm gravel achieved the highest reduction in chemical oxygen demand (COD) of 8.2 %, 7.7 % ammonia-N and 38 % total inorganic nitrogen removal. The 40-minute RT at 7-mm gravel had the highest nitrate-N removal of 18.6 %. Orthophosphate removal was below 5 % in all treatments. The peak removal for ammonia and total inorganic nitrogen was after 8 and 10 weeks, respectively, suggesting that the efficiency of the ebb-and-flow design on nutrient removal is time-dependent. The aerobic and anaerobic conditions of ebb-and-flow operation, gravel surface area and effluent retention time influence nutrient transformation and removal. Results for Experiment 2 indicated significant differences between unmixed and mixed media on nutrient removal (p ≤0.05). The unmixed media of clay pebbles had the highest mean reduction chemical oxygen demand of 7.5% and 8.1% ammonia-N removal. Mixing resulted in better overall mean removal efficiency of nitrite- N (7.6%), nitrate-N (15.3%), total inorganic nitrogen (29.9%), orthophosphate (12.7%) and plant biomass (11158.5 gm -2 ) than unmixed media. Media porosity, surface area, chemical composition and celery plant growth enhanced nutrient removal through synergistic interactions. Experiment 1 recommends a short effluent retention time of 10 minutes on 19-mm gravel for improved nutrient removal in the ebb-and-flow system design. Experiment 2 recommends unmixed clay pebbles, bioballs, and 19-mm gravel forimproved ammonia-N removal and mixed media for multiple pollutant removal and celery productivity in the ebb-and-flow constructed wetland.

MACROINVERTEBRATE FUNCTIONAL AND STRUCTURAL RESPONSES TO HUMAN DISTURBANCE AND FLOW CESSATION IN AFROMONTANE-SAVANNAH RIVERS

2026-06-08T08:48:34Z

MACROINVERTEBRATE FUNCTIONAL AND STRUCTURAL RESPONSES TO HUMAN DISTURBANCE AND FLOW CESSATION IN AFROMONTANE-SAVANNAH RIVERS OWADE, CHRISTINE Freshwater ecosystems in the Afrotropics are increasingly threatened by human activities and disturbances, including agriculture, livestock grazing, water abstraction, and sand harvesting. These activities degrade habitat quality, alter flow regimes, and influence the composition and functioning of aquatic communities. This study assessed the structural and functional responses of macroinvertebrate communities to varying levels of human disturbance, flow permanence, and seasonality in the Wundanyi-Bura catchment, a representative Afromontane-savannah River system in southeastern Kenya. Macroinvertebrates were sampled from 18 study sites categorized by varying disturbance levels (low, moderate, high), flow duration type (permanent vs seasonal), and season (dry vs wet). Physical and chemical water quality parameters, habitat characteristics, and land-use patterns were also quantified. Functional composition was evaluated using Functional Feeding Groups (FFGs) and 14 biological traits comprising 52 ecological trait attributes. Results showed significant degradation in water and habitat quality with increased disturbance, particularly in the lower river reaches. Functional trait analyses revealed that disturbed and seasonal sites were dominated by resilient taxa such as burrowers, predators, and collector-gatherers, while less disturbed, permanent sites had higher proportions of sensitive taxa like shredders and scrapers. Flow variability and seasonality strongly influenced trait distributions and ecosystem attributes, including trophic dynamics, organic matter processing, and top-down control. Multivariate analyses (ANOSIM, NMDS, SIMPER) and trait-based approaches provided robust indicators of ecological integrity and disturbance gradients. This study underscores the value of integrating functional traits and FFG ratios in biomonitoring and river health assessment. It provides crucial baseline data for the Afrotropics, where biomonitoring frameworks are still underdeveloped, and highlights the need to consider both structural and functional metrics in the conservation, restoration, and management of freshwater ecosystems under increasing anthropogenic pressures.

Economic Viability of Agricultural Carbon Sources on Asian Rice (Oryza sativa Lejeunia 1753.) and Nile Tilapia (Oreochromis niloticus) Production in a Flocponic System

2026-04-13T11:55:07Z

Economic Viability of Agricultural Carbon Sources on Asian Rice (Oryza sativa Lejeunia 1753.) and Nile Tilapia (Oreochromis niloticus) Production in a Flocponic System Rono, Kenneth; Matolla, Geraldine; Manyala, Otieno Julius; Masese, Onderi Frank A flocponic system is a fish and plant-based system that uses carbon sources. However, the economic viability of using carbon sources for production remains unknown. Hence, the study assessed the economic viability of utilizing agricultural carbon sourc es in a flocponic system. A complete randomized design was employed in five treatments (wheat-bran, rhodes-hay, maize-cob, maize-stables, lucerne-hay, agricultural carbon sources, and a control (no carbon), each in triplicate. Each treatment and control had Nile tilapia and rice densities of 98 m-3 fry and 250 m-2 rice, respectively. The fish yield differed among the treatments and control, with lucernehay showing the highest output (2.53±0.02 kgm-3 ) and control having the lowest. The rice yield component also showed variability. Lucerne-hay had the highest grain yield of 5.70±0.25 kgm-3 , followed by wheat-bran, rhodes-hay, maize-cob, and maizestables treatments. The control yielded the lowest weight of grains and rice straws. The flocponic system's profitability varied between the treatment and control groups. Lucerne-hay, wheat-bran, and rhodes-hay generated positive net income, amounting to 1338.39, 474.69, and 266.1, respectively. The benefit-cost ratios for the lucerne-hay, wheat-bran, and Rhodes-hay treatments were greater than one, with lucerne-hay having the highest value (1.72). There was a slight variation in the expense structure ratio; wheat-bran had the lowest value of 0.88. The gross revenue ratio varied between the treatments and the control group; the control had the highest ratio of 145.39, and lucerne-hay had the lowest. The lucerne-hay, wheat-bran, rhodes-hay, and maize-cob treatments yielded a positive return on investment, while the maize-stable treatment and control had a negative return on investment. The proximate composition and cost of the carbon source may have impacted the profitability of the flocponic production. Wheat-bran, lucerne-hay, and rhodes-hay are suitable for flocponic output because of their high productivity and profitability, resulting in a favorable return on investment. These options are economically viable.

Effects of Agricultural Carbon Sources On Water Quality and Phytoplankton Community Composition in Flocponic System

2026-04-13T11:13:23Z

Effects of Agricultural Carbon Sources On Water Quality and Phytoplankton Community Composition in Flocponic System Rono, Kenneth; Matolla, Geraldine; Manyala, Julius Otieno; Masese, Frank Onderi Carbon products promote aggregate floc-rich plankton, with diverse roles in flocponic production. Availability, low-cost, and chemical composition of agricultural by-products make them ideal substrates for phytoplankton production. Phytoplankton maintains water quality by reducing toxic substances, but it is problematic under some conditions. Therefore, the study evaluates how agricultural carbon sources affect flocponic phytoplankton community composition and water quality. Five treatments (wheat-bran, Rhodes-hay, maize-cob, maize-stables, and lucerne-hay) and a control (no byproduct) were employed in a complete randomized design, each in triplicate for nine weeks. Each treatment and control had Nile tilapia (0.155 ± 0.01 g) and rice (seeds) densities of 98 m-3 and 250 m-2 , respectively. Temperature, pH, dissolved oxygen, and salinity levels did not differ significantly between treatments and control. However, TDS, soluble reactive phosphorus (SRP), ammonia, nitrite, and nitrate showed significant differences (p<0.05) between treatments and control. Lucerne-hay exhibited the highest nitrate levels (0.9 ± 0.06 mg L-1 ), SRP (0.6 ± 0.05 mg L-1 ), and the lowest ammonia and nitrite levels compared to other treatments and control. Lucerne-hay had the highest phytoplankton diversity (2.48), while the control (1.37) had the least. Further, there were significant differences in phytoplankton abundance, with lucernehay having the highest Charophyta (1.45 ± 0.02 indsL-1 ), Chlorophyta (1.60 ± 0.02 indsL-1 ), and Ochrophyta (1.64 ± 0.03 indsL-1 ) abundance, while the control had the least. The result of the study revealed that carbon sources influence flocponic water quality and phytoplankton. The composition and solubility of lucerne-hay and wheat-bran may have improved water quality and phytoplankton. The study suggests that lucerne-hay and wheat-bran are the best flocponic carbon sources for phytoplankton and water quality.

Effect of the ebb-and-flow constructed wetland operation, media type and celery (Apium graveolens L.) growth on nutrient removal from a pre-treated brewery effluent

2026-03-26T13:59:31Z

Effect of the ebb-and-flow constructed wetland operation, media type and celery (Apium graveolens L.) growth on nutrient removal from a pre-treated brewery effluent Obado, Elizabeth; Kaise, Horst; Taylo, Richard; Mabasa, Nyiko; Agembe, Simon; Liti, David; Manyala, Julius Breweries face a high cost of wastewater treatment to meet environmental discharge standards. Constructed wetland (CW) design and operation have been optimised for sustainable wastewater treatment. An ebb-and-flow CW was used to investigate the effect of media on nutrient removal from a brewery effluent. Eight media (clay pebbles, clay bricks, sand, bioballs, recycled plastic and gravel sizes), either alone or mixed, were tested. A 2:1:1 ratio of each media, pine bark and granular activated carbon, respectively, was used for mixed treatments. A uniform celery planting density of eight seedlings per m2 and 12-min effluent retention time was used. There were significant differences between unmixed and mixed media on nutrient removal (p , 0.05). The unmixed media of clay pebbles had the highest mean COD reduction of 7.5% and ammonia 8.1%. Mixing resulted in better overall mean removal efficiency of nitrite-N (7.6%), nitrate-N (15.3%), total inorganic nitrogen (29.9%), orthophosphate (12.7%) and plant biomass (11158.5 gm 2 ) than unmixed media. Media porosity, surface area and chemical composition and celery plant enhance nutrient removal through synergistic interactions. The study recommends unmixed clay pebbles, bioballs and 19-mm gravel for improved ammonia-N removal and mixed media for multiple pollutant removal and celery productivity.

Macroinvertebrate functional responses to human disturbance and flow cessation in Afromontane-savannah rivers

2026-03-24T09:44:09Z

Macroinvertebrate functional responses to human disturbance and flow cessation in Afromontane-savannah rivers Owade, Christine A.A.; Kaiser, Horst; Simiyu, Gelas M.; Owuor, Godfrey; Sicharani, Evans; Gettel, Gretchen M.; Masese, Frank O. Wildlife, people, and livestock rely on riverine ecosystems in arid and semi-arid areas as primary water sources. Studies on the influence of human activities and livestock on the ecological health of these seasonal systems are thus necessary. This is more relevant given the increasing demand for water as human populations grow, which leads to over-abstractions and, sometimes, cessation of flows in streams and rivers during the dry periods. Although the structural composition of macroinvertebrate communities has been utilized to indicate the ecological integrity of streams and rivers, macroinvertebrate functional feeding groups (FFGs) are less studied, especially in intermittent Afrotropical streams. We used macroinvertebrate FFGs as indicators of water quality and ecological integrity of streams influenced by different levels of human disturbance and flow variability in the Afromontane-savanna Bura and Wundanyi rivers in Taita Taveta County, Kenya. A total of 18 sampling sites were identified for sampling and grouped into three (3) disturbance categories (low– n = 7, moderate - n = 4, and disturbed - n = 7) and two categories of flow permanence (permanent – n = 9, and seasonal – n = 9). At each site, sampling of physicochemical water quality parameters and macroinvertebrates was done twice during the wet and dry seasons. Ratios of five FFGs (collector-gatherers, collector-filterers, scrapers/grazers, predators, and shredders) were used to derive five metrics that are surrogates of ecosystem attributes in the rivers. There was a significant difference (p < 0.05) in the concentrations of dissolved organic carbon, total phosphorus, pH, and electrical conductivity between the three site categories. Seasonal sites recorded higher electrical conductivity and total dissolved solids compared to permanent streams. Total suspended solids and particulate organic matter were higher during the dry season. FFGs responded to the disturbance gradient, seasonality, and flow variability in the study area with high numbers of predators and scrapers during dry season, suggesting that the human disturbance influenced the functional composition of macroinvertebrates in the rivers. The findings also show that flow variability (seasonal vs flow permanence) played a important role in structuring communities and determining ecosystem functioning. Therefore, in addition to general human disturbance, there is also a need to study the impact of excessive water withdrawals or changes in natural flow regimes of streams and rivers on aquatic communities and the development of indices to assess their effects.

ECOLOGICAL CARRYING CAPACITY AND GROWTH PERFORMANCE OF NILE TILAPIA (Oreochromis niloticus) IN CAGE AQUACULTURE WITHIN KADIMO BAY, LAKE VICTORIA, KENYA

2025-05-22T08:11:06Z

ECOLOGICAL CARRYING CAPACITY AND GROWTH PERFORMANCE OF NILE TILAPIA (Oreochromis niloticus) IN CAGE AQUACULTURE WITHIN KADIMO BAY, LAKE VICTORIA, KENYA MAWUNDU, SELLU Fish production in the wild is decreasing globally due to a number of factors including overfishing, pollution, invasive species, and climate change effects. In Kenya, fisheries contribute less than 1% to the national GDP with an annual production of about 400, 000 mt against a demand of about 600,000 mt. Aquaculture production through innovative approaches such fish cage farming, has the potential to bridge the demand deficit. Despite the high potential for cage fish farming in Kenyan water bodies, there have been few studies focused on the effects of fish cages on water quality and trophic status, the nutrient carrying capacity of cage sites, and the appropriate stocking densities for cages in the water bodies. This study therefore was aimed to bridge these data gaps in order to facilitate sustainable management of the increasing fish cage farming of the Nile tilapia (Oreochromis niloticus) in Lake Victoria. Sampling for physico-chemical and biological variables, including nutrient load, was conducted from January to October 2021, at five fish cage sites and a control site within the Kadimo Bay,Lake Victoria, Kenya. The Carlson's Trophic State Index (CTSI) was used to classify the trophic state of the cage sites in the bay, and TN: TP ratio used to determine nutrient limitation in the bay. Fish cage optimum stocking density studies were carried in the bay from February to September 2022. Oreochromis niloticus fingerlings with initial mean (±SD) weight of 5.5 ± 1.72 g, were stocked at densities of 50, 75, 100, 125 and 150 fish m3 in replicate cages and growth and water quality changes monitored. The TP assimilation capacity and fish production potentials for the five cage sites within the bay were determined using a mass-balanced model. Results showed higher electrical conductivity (112.84 ± 1.94 μS cm-1 ) at cage sites compared to a Control site (97.53 ± 4.17 μS cm-1 ), similar variations were observed for nitrates and chlorophyll-a. However, 15 physico-chemical variables (DO, Temp., pH, TDS, Turb., TSS,POM, SRP, NO2 - , NO3 - , TN, TP, NH3, NH4 + , SiO4 4- ) did not vary significantly between the cage and control sites. The bay was evaluated as being in a light eutrophic state. Nitrogen as opposed to Phosphorus, was indicated to be the limiting nutrient for primary production in the bay. Growth performance results showed that fish stocked at lower densities (D50 & D75) had the highest growth performance in terms of mean weight gain (545.0 ± 15.81 and 527.4 ± 13.80 g, respectively). The Control treatment (D100), which is the normal stocking density used by cage fish farmers, showed intermediate mean weight gain (348.2 ± 11.48 g) which was significantly lower (p < 0.05) than for the D50 and D75 treatments. The feed conversion ratio (FCR) was lowest at D50 (1.2 ± 0.02) and highest at D150 (2.9 ± 2.01). Carrying capacity results, showed for all the five cage sites within the bay, the TP assimilation capacity was exceeded by the TP released by the fish cages. Additionally, the maximum estimated fish production capacities were much less than the current fish production levels for all the sites. Overall, although the results of this study showed cage aquaculture is not a current challenge to the water quality of the bay, regular monitoring is recommended to inform sustainable aquaculture development in the bay and the lake. It is recommended for fish farmers to stock fish at lower densities of 50 fish m 3 in order to maximize sustainable economic and environmental benefits of the cage culture system. Policies governing aquaculture production in the lake should be reviewed or enacted in order to include evidence-based information on environmental quality, sustainable production levels, and nutrient carrying capacity of the lake.

Influence of net cages on water quality and trophic status of Lake Victoria, Kenya: The case of Kadimu Bay

2025-05-21T12:02:51Z

Influence of net cages on water quality and trophic status of Lake Victoria, Kenya: The case of Kadimu Bay Mawundu, Sellu; et. al... Water quality is a critical component regulating ecosystem functioning in aquatic habitats, requiring regular monitoring for sustainable ecosystem services. Cage fish farming has the potential to affect water quality because of its rapid increase in many African waterbodies in response to dwindling wild fish stocks. Thus, there is a need for more studies to guide sustainable cage aquaculture in African lakes and reservoirs. This study evaluated the possible effects of cage farming of Nile tilapia (Oreochromis niloticus) on water quality parameters and the trophic state of Kadimu Bay, Lake Victoria, Kenya. Sampling for physicochemical and biological variables, including nutrient load, was conducted from January to October 2021, at five fish cage sites and a control site within the bay. In situ measurements of physical variables were undertaken in the field, while analysis of water samples for nutrient loads, biological and chemical variables was undertaken in the laboratory, following the methods described in APHA (American public health association standard methods for the examination of water and waste water. APHA-AWWA-WEF, 2005). The Carlson's Trophic State Index (CTSI) was used to classify the trophic state of the cage sites, while the total nitrogen:total phosphorus (TN:TP) ratio was used to determine the primary productivity limiting nutrient in the bay. The study results indicated electrical conductivity was significantly lower at the control (97.53 ± 4.17 μS/cm), compared to cage sites (105.42 ± 5.32 μS/cm at the Utonga cage site to 112.84 ± 1.94 μS/cm at the Oele cage site), indicating water of relatively lower quality at the cage sites. Similarly, the nitrite concentrations were higher at cage sites (6.35 ± .96 μg/L at the Uwaria cage site to 3.16 ± 2.25 μg/L at the Utonga cage site), and lower at the control site (2.68 ± 1.39 μg/L). In all, 14 physicochemical variables did not vary significantly between the cage and control sites, with nine variables (temperature, turbidity, electrical conductivity, total suspended solids, particulate organic matter, chlorophyll-a, TP, nitrate and TN) being within the recommended thresholds for aquatic life processes. The bay was evaluated as being in a light eutrophic state, indicating moderate influence of the fish cages on the trophic state of the sites. There was a moderate relationship between chlorophyll-a and TP concentration at the sampling sites (R2= .50), compared to a stronger relationship with NO− 3 (R2= .78). The TN:TP ratios were <10 at the sampling sites, indicating nitrogen was the limiting factor for primary production in the bay. The calculated CTSI suggests that the bay exhibited a light eutrophic state. Overall, although the results of this study showed cage aquaculture is not a current challenge to the water quality of the bay, regular monitoring is nevertheless recommended to inform sustainable aquaculture development in the bay and lake.

Morphomeristic Characterization of Enteromius Species in Small Water-bodies of the North Rift, Kenya

2025-05-20T07:35:33Z

Morphomeristic Characterization of Enteromius Species in Small Water-bodies of the North Rift, Kenya Jepleting, Hildah; et. al... Enteromius, a diverse genus of cyprinid fish native to tropical Africa, comprises around 350 species. These species inhabit various aquatic habitats, notably in Kenya’s North Rift region. Rivers and reservoirs in this area provide essential habitats but face threats from agricultural activities and habitat fragmentation. Morphometric and meristic traits help manage fisheries by offering insights into population dynamics and species identification, although misidentifications pose challenges. Conservation of Enteromius is crucial as these fish support local biodiversity and food security, yet they are increasingly threatened by environmental changes and human activities. The study, conducted in Kenya's North Rift sampled small water bodies, involved sampling 25 rivers and reservoirs impacted by agriculture. Fish were collected from February to July 2018 using electrofishing and seine nets. A total of 972 Enteromius specimens were identified, measured, and analyzed for morphometric and meristic traits. Measurements were taken with Vernier calipers, and 11 meristic counts were recorded. Unidentified samples were preserved for further identification at the National Museums of Kenya. The analysis was performed at UoE Labs following established methodologies. The results indicated that E. paludinosus from Kapsaina Reservoir had the highest standard length (SL) of 8.1±0.8 cm, while E. neumayeri from Ellegrin Reservoir reached 9.4±1.3 cm. Notable differences in operculum length, prepectoral length, prepelvic length, preanal length, and body depth were recorded across different reservoirs and rivers. For instance, Karara Reservoir populations showed the highest operculum length in E. paludinosus (28.2±4.9) and E. neumayeri (25.5±3.2). Meristic traits, such as lateral scales above and dorsal fin rays, also varied significantly, with Kapsaina Reservoir exhibiting the highest range for E. paludinosus. In conclusion, significant trait variations among E. paludinosus, E. apleurogramma, E. neumayeri, and E. cercops across habitats indicate complex genetic and environmental influences emphasizing the need for further research to understand these adaptations and their evolutionary implications