Browsing by Author "Omondi, Reuben"
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Publication A review of the impacts of invasive aquatic weeds on the bio- diversity of some tropical water bodies with special reference to Lake Victoria (Kenya)(Biodiversity, 0020-12-30) Aloo, Peninah; Ojwang, William; Omondi, Reuben; Njiru, James Murithi; Oyugi, DalmasAquatic weeds may be defined as troublesome or unsightly plants growing in abundance inaquatic situations where they are not wanted. These plants are either adapted to continuoussupplies of water or are at least tolerant to waterlogged soil conditions for substantial periodsof time. The wide range of adaptation to varying amounts of water, and the impossibility ofsharply distinguishing between aquatic and terrestrial environments, makes it difficult toprecisely define an aquatic plant. The menace of water weeds is reaching alarming proportions in many parts of the world, especially in tropical water bodies where they have led toserious ecological and economic losses. Lake Victoria, Kenya, which is the largest freshwaterbody in the tropics, has undergone serious ecological changes including over-exploitationof its fishery resources, degradation of the catchment area, introduction of exotic fish speciesand invasion by the water hyacinth, Eichhornia crassipes (Mart.) Solms (Pontederiaceae),among others. The presence of the weed in the lake has led to many problems includingblockage of water pumps, reduced fishing activities and increase in water borne diseasessuch as schistosomiasis. Positively, aquatic weeds constitute a free crop of great potentialvalue; they are a highly productive crop that requires no tillage, fertilizer, seed, or cultivation.Moreover, these plants have the potential for exploitation as animal feed, human food, sourceof food to some aquatic organisms, soil additives, fuel production, wastewater treatment,source of raw materials and habitat to many organisms. This paper reviews the effects ofaquatic weeds in aquatic systems with examples from some selected waterbodies and specialreference to Lake Victoria.Publication A review of the impacts of invasive aquatic weeds on the bio- diversity of some tropical water bodies with special reference to Lake Victoria (Kenya)(Biodiversity Journal, 2013-12-30) Aloo, Peninah; Ojwang, William; Omondi, Reuben; Njiru, James Murithi; Oyugi, DalmasAquatic weeds may be defined as troublesome or unsightly plants growing in abundance inaquatic situations where they are not wanted. These plants are either adapted to continuoussupplies of water or are at least tolerant to waterlogged soil conditions for substantial periodsof time. The wide range of adaptation to varying amounts of water, and the impossibility ofsharply distinguishing between aquatic and terrestrial environments, makes it difficult toprecisely define an aquatic plant. The menace of water weeds is reaching alarming proportions in many parts of the world, especially in tropical water bodies where they have led toserious ecological and economic losses. Lake Victoria, Kenya, which is the largest freshwaterbody in the tropics, has undergone serious ecological changes including over-exploitationof its fishery resources, degradation of the catchment area, introduction of exotic fish speciesand invasion by the water hyacinth, Eichhornia crassipes (Mart.) Solms (Pontederiaceae),among others. The presence of the weed in the lake has led to many problems includingblockage of water pumps, reduced fishing activities and increase in water borne diseasessuch as schistosomiasis. Positively, aquatic weeds constitute a free crop of great potentialvalue; they are a highly productive crop that requires no tillage, fertilizer, seed, or cultivation.Moreover, these plants have the potential for exploitation as animal feed, human food, sourceof food to some aquatic organisms, soil additives, fuel production, wastewater treatment,source of raw materials and habitat to many organisms. This paper reviews the effects ofaquatic weeds in aquatic systems with examples from some selected waterbodies and specialreference to Lake VictoriaPublication Application of phytoplankton community structure for ranking the major riverine catchments influencing the pollution status of a lake basin(Wiley, 2020-02-18) Aura, Christopher Mulanda; Odoli, Cyprian; Nyamweya, Chrisphine S.; Njiru, James M.; Musa, Safina; Miruka, Jared Babu; Owili, Monica Ochieng; Omondi, Reuben; Raburu, Phillip; Manyala, Julius; Mwamburi, Job; Ogari, Zachary; Mbaru, Emmanuel K.The present study demonstrates the application of a multi‑metric Phytoplankton Index of Biotic Integrity (PIBI) approach for ranking of major river catchments in the Kenyan part of Lake Victoria on the basis of their pollution status. The index utilizes water quality and zooplankton data, phytoplankton diversity, abundance and attributes, as well as literature information. The rivers were sampled from 2016 to 2018 during the wet season (March) and dry season (July). The separation power of the Mann–Whitney U test (p < .05) qualified eight discriminant metrics for phytoplankton samples into a scoring system of 1, 3 and 5, based on high, fair and slight deviation from the best site, respectively, in development of the final PIBI. The Kuja and Sondu‑Miriu rivers had the highest PIBI, signifying least pollution influence on the lake. In contrast, the Yala and Nzoia rivers exhibited the lowest PIBI, representing the catchments with a higher pollution influence on the lake. The fair to poor integrity classes for the major river catchments in the region signified a deteriorating lakescape. The present study presents the preliminary results of using phytoplankton metrics for development of the Index of Biotic Integrity (IBI) approach in the region as a decision‑making support tool for the effective management and sustainable use of water resources in the lake basin.Publication Assessment of Heavy Metal Concentrations (Cu, Cd, Pb, and Zn) in Wastewater from Gusii Treatment Plant in Kisii County, Kenya(Pan Africa Journal of Sciences, 2022) Rayori, Douglas; Albert, Getabu; Omondi, Reuben; Paul, Orina; Hellen, Nchore; Boniface, Gisacho; Obed, Nyabaro; Omondi, Argwings; Omweno, JobThe concentrations of heavy metals were determined from wastewater samples collected from the Gusii wastewater treatment plant, from May to July, 2021. Heavy metal analysis was done using a flame atomic absorption spectrophotometer, model AA 7000 Shimadzu, Japan. The results showed that the concentrations of Zinc and Cadmium were below the detection limit for all the sampling sites. The concentrations of Lead and Copper (Mean ± SE) ranged between 0.34 ± 0.06 mg/L and 0.86 ± 0.08 mg/L and 0.25 ± 0.05 and 0.34 ± 0.01 mg/L respectively. The month of July exhibited a higher mean Cu concentration of 0.35 ± 0.004 mg/L compared to the mean Cu concentration (0.2 ± 0.02 mg/L) of May. Likewise, the mean lead concentration of May (0.60 ± 0.04 mg/L) was higher than the mean (0.53 ± 0.05 mg/L.) of July. The independent sample t-test showed that mean Cu concentration difference was significant between the sampling months (t (34) = 21.58; p < 0.05) while for Pb it was not significant between the sampling months (t (30) = 1.241; p = 0.274). The percentage removals of Copper and Lead were generally low at 12.61 % and 6.27 %, respectively. The continued discharge of effluent into River Riana may lead to accumulation of heavy metals in the environment, which in turn poses health risks to the general public. Therefore, the study recommends that Gusii Water and Sanitation Company continue monitoring and assessing the levels of heavy metals in the treatment plant for its sustainability.Publication Characteristic Relationships between Phosphorous Accrual, Ecosystem Aspects and Water Level Fluctuations in Tropical Lakes: Naivasha Ramsar Site, Kenya(Scientific Research, 2021-01) Obegi, Beatrice; Ogendi, George; Omondi, Reuben; Jomo, Boston; Morara, George; Rindoria, Nehemiah; Orina, SagweHydrological dynamics affect water levels and thus affecting ecosystem structure and functions. Lake levels in tropical ecosystems affect phosphorous input through runoff from adjacent watersheds. The resultant biological community, water and sediment quality of the lakes due to water level changes is a reflection of the geology of the area and the anthropogenic activities in the watershed. The study conducted between January 2018 and December 2019 was to explore relationships between the phosphorous input and Water Level Fluctuations (WLF) recorded by Water Resource Authority (WRA). Lake water samples were analyzed in the laboratory for phosphorous using molybdenum blue-ascorbic method and recorded using spectrophotometer. Chlorophyll-a was determined by extracting a filtered sample with 15 ml acetone and incubating overnight and thereafter read using a double beam spectrophotometer. Total Suspended Solids (TSS) was determined by filtering 200 ml of a water sample and dried overnight at 105°C. The lowest and highest phosphorous concentrations recorded were 0.2 mg/l and 0.42 mg/l at NST7 and NST2, respectively. Measurements of Chlorophyll-a were 0.32 mg/l and 0.42 mg/l at NST9 and NST2, respectively. Secchi transparency measurements were 32.9 cm at NST3 and 84 cm at NST1. The highest and lowest TSS concentrations were 0.14 mg/l and 0.13 mg/l at NTS1 and NST8, respectively. The hydrodynamic regime in most tropical lakes plays a significant role in the re-reaction of phosphorous that consequently influences productivity. Tropical lakes have extreme lake level fluctuations which accelerate the production process. The influence of water level changes on aquatic productivity is crucial in most tropical lakes and should be taken into consideration when assessing the environmental impacts.Publication Composition, Abundance and Feeding Guilds of Macroinvertebrates in Lake Kenyatta, Kenya(International Journal of Environmental Monitoring and Analysis, 2014-09-30) Orwa, Patrick Oduor; Omondi, Reuben; Okuku, Eric; Ojwang, William; Njuguna, Stephen MwangiIn an attempt to describe the benthic macroinvertebrate assemblage of Lake Kenyatta and recommend possible interventions for sustainable management, sampling was done at different stations using an Eckman grab and a scoop net. At each station, six samples were taken (three grabs and three scoops). The samples were washed using a 300µm sieve, sorted live and identified to genus level and where possible to species level using appropriate keys. The specimens were further categorized into functional feeding guilds. The data were then analysed for diversity, evenness, abundance and dominance. Forty two species in 25 families and 13 orders were recorded. The organisms were further grouped into 4 functional feeding groups. The order Pulmonata dominated the macroinvertebrates sampled with 34.3% relative abundance while the lowest were Rhynchobdellida and Lepidoptera with 0.3% each. The high abundance of mollusks in the lake is probably an indication of absence of a predator. It is thus recommended that a fish species be introduced to convert these mollusks into fish biomass. This will enhance the economic gains and reduce the risk of bilhazia infestation since the host snail exists within the lake.Publication Diversity, composition and abundance of macroinvertebrates associated with water hyacinth mats in Lake Victoria, Kenya(African Journal of Education,Science and Technology, 2015-03-30) Orwa, Patrick; Omondi, Reuben; William, Ojwang; Josephat, MwanchiThis study is set to investigate the macroinvertebrate community structure within water hyacinth in the Kenyan waters of Lake Victoria. This is helpful in determining the relationship between water hyacinth and macroinvertebrates. A total of four replicates were taken from 18 sampling stations within the lake using a Ponar grab and a 500 µm scoop net. The samples were washed through a 300 µm sieve and sorted alive in the field. The organisms were then identified to genus level and further categorized into functional feeding guilds using available keys and literature. The vertical position of the organisms at a water hyacinth mat was also examined. The data was then analyzed for diversity and abundance. One way ANOVA was further done to test any significant variation in community attributes between stations within the lake. All the physic-chemical parameters measured varied significantly though pairwise comparison revealed that most stations were in same sub set. A total of 14 orders and 34 genera were identified during the study. Out of which, 13 genera which include Chironomus, Lymneae, Hirudo, Tubifex, Platycnemis, Sympetrum, Trithemis, Melanoides, Biomphalaria, Ilybius, Elmis, Leptocerus, and Hexagenia were found at every sampling station. Most of the taxa found were predators probably feeding on mosquito larvae which could explain their absence. There was no significant difference in the diversity between stations though they varied in abundance. It is thus concluded that water hyacinth influences the distribution of macroinvertebrates and can thus be used to predict their presence. The feeding guilds were however assigned using existing literature. It is therefore recommended that a further study be done to confirm the feeding habits and the presence of mosquito larvae. Key words: Macroinvertebrates, hyacinth, Lake VictoriaPublication Diversity, composition and abundance of macroinvertebrates associated with water hyacinth mats in Lake Victoria, Kenya(Academic Journals, 2015-03-30) Orwa, Patrick; Omondi, Reuben; William, Ojwang; Josephat, MwanchiThis study is set to investigate the macroinvertebrate community structure within water hyacinth in the Kenyan waters of Lake Victoria. This is helpful in determining the relationship between water hyacinth and macroinvertebrates. A total of four replicates were taken from 18 sampling stations within the lake using a Ponar grab and a 500 µm scoop net. The samples were washed through a 300 µm sieve and sorted alive in the field. The organisms were then identified to genus level and further categorized into functional feeding guilds using available keys and literature. The vertical position of the organisms at a water hyacinth mat was also examined. The data was then analyzed for diversity and abundance. One way ANOVA was further done to test any significant variation in community attributes between stations within the lake. All the physic-chemical parameters measured varied significantly though pairwise comparison revealed that most stations were in same sub set. A total of 14 orders and 34 genera were identified during the study. Out of which, 13 genera which include Chironomus, Lymneae, Hirudo, Tubifex, Platycnemis, Sympetrum, Trithemis, Melanoides, Biomphalaria, Ilybius, Elmis, Leptocerus, and Hexagenia were found at every sampling station. Most of the taxa found were predators probably feeding on mosquito larvae which could explain their absence. There was no significant difference in the diversity between stations though they varied in abundance. It is thus concluded that water hyacinth influences the distribution of macroinvertebrates and can thus be used to predict their presence. The feeding guilds were however assigned using existing literature. It is therefore recommended that a further study be done to confirm the feeding habits and the presence of mosquito larvae. Key words: Macroinvertebrates, hyacinth, Lake VictoriaPublication Ecological integrity of a medium-sized river of a lake basin towards ecosystem health management(Wiley, 2023-10-13) Osure, George Owiti; Aura, Christopher Mulanda; Getabu, Albert; Omondi, Reuben; Basweti, EvansThis study demonstrates the use of a multi-metric Fish Index of Biotic Integrity (FIBI) for assessment of ecological health of a medium-sized river, under a gradient of human disturbances in the Kenyan side of the Lake Victoria Basin (LVB). Development of the index is based on water quality, river habitat quality and fish community attributes. The river was sampled from 2019 to 2020 during wet and dry seasons of the year at nine selected sites along its length based on the level of human disturbance. A total of nine metrics representing the structural and functional organization of fish communities were qualified using the separation power of Mann–Whitney U test (p < .05). Metric values at unimpaired, intermediate, impaired and no-fish sites were used to establish the scoring criteria using inter-quartile ranges. A 1, 3, 5 scoring system representing high, fair and slight deviation from the best site, respectively, was used in the final FIBI development. River mouth station had the highest FIBI score of 43, with extensive natural riparian buffer vegetation (>20 m) and 18 fish species implying least human disturbance. The midstream section had intermediate FIBI scores of 34–36, with wide natural riparian buffer vegetation (10–20 m) and 6–9 fish species that represented moderate human disturbance. The upstream section had the least FIBI score of 0, with no fish and narrow riparian buffer vegetation (<5 m) that indicated notable degradation. This study presents the preliminary results of using fish and habitat metrics for development of an Index of Biotic Integrity (IBI) for a medium-sized river in a lake basin, as a decision-making support tool for effective management and conservation of water resources. The study recommends restoration of river habitat quality for improved ecological integrity of rivers in the Lake Victoria Basin.Publication Effect of Eichhornia crassipes on coliforms load in small water bodies within Lake Victoria basin, Kenya(Academic Journals, 2015-03-11) Veronica, Ombwa; Orwa, Patrick; Alice, Mutie; Omondi, Reuben; Kenneth, Werimo; Ouko, JohnThe study investigates the effects of Eichhornia crassipes (water hyacinth) infestation based on coliform loads which are pollution indicator organisms. These dams have fish and the waters are commonly used for domestic purposes without any treatment hence it is necessary to check their status. Sampling was done on 25 small water bodies and from which water samples were taken for microbial determination. Membrane filtration method was used to enumerate fecal coliforms by use lauryl sulphate broth and incubated at 44 ± 0.5°C for 18 to 24 h. The results show that water bodies infested by water hyacinth harbored higher levels of fecal coliforms compared to those devoid of the weed. The high fecal coliform levels have negative impacts on the lives of communities using these water bodies. In addition, it reduces native species and disrupts food chains and nutrient cycle. The small water bodies within the Lake Victoria basin need frequent monitoring in order to give the relevant authorities concrete information for proper sensitization to the communities. Water hyacinth should also be properly managed so that it does not chock dams that are used for domestic and fishing activities.Publication Environmental constraints on macrophyte distribution and diversity in a tropical endorheic freshwater lake (Lake Baringo, Kenya)(International Journal of Fisheries and Aquatic Studies, 2018-06) Ondiba, Robert; Omondi, Reuben; Nyakeya, Kobingi; Abwao, Jacob; Musa, Safina; Oyoo-Okoth, ElijahThe structure of macrophyte assemblages can be affected by myriad factors, including physical and chemical characteristics of the water body. However, knowledge on the environmental factors affecting macrophyte diversity in endorheic freshwater lakes is limited. In this study the patterns of plant species diversity and composition and their potential determinants in Lake Baringo, Kenya, is described. Macrophyte sampling in Lake Baringo was done monthly from January 2015 to April 2016 using quadrats (1 m × 1 m) placed along transects perpendicular to the shoreline. Water temperature, pH, conductivity, dissolved oxygen (DO), salinity and alkalinity were measured in situ at each of the sampling sites. Findings revealed that macrophyte species composition and assemblage exhibited significant spatial differences (P<0.05), where areas near river inlets had higher species composition and percentage cover. The findings improve the understanding of floristic patterns and plant biodiversity in the lake.Publication Importance of Indeginous Macrophytes in Control of Water Hyacinth in the Nyanza Gulf of Lake Victoria, Kenya.(Aquadocs, 2000) Omondi, Reuben; Gichuki, JohnObservation of macrophytes dynamics in the Nyanza gulf of Lake Victoria is ongoing since the early 1990s. A checklist of the macrophytes and their distribution in the study area is provided. Occurrence of macrophytes before and after the invasion of water hyacinth is highlighted. The dynamics of water hyacinth, control measures employed for its control and macrophyte succession are also mentioned.Publication Intriguing case of ecosystem dynamics in the Lake Victoria: Water Hyacinth (Eichhornia crassipes) and Escherichia coli(International Journal of Fisheries and Aquatic Studies, 2015-03-15) Mutie, Alice; Ojwang, William; Werimo, Kenneth; Omondi, Reuben; Ouko, JohnWater hyacinth (Eichhornia crassipes) is a noxious weed with immense impact on the health and the livelihoods of communities’ in the tropical sub-Saharan African countries. This study was aimed at assessing the effects of water hyacinth on Escherichia coli levels in Kenyan Lake Victoria. Sampling was done in waters infested by water hyacinth (roots and mats) and in open water areas (devoid of the weed). Membrane filtration method was used to enumerate Escherichia coli at 44.5 ºC for 18-24 h. Results showed that E. coli levels were higher in water hyacinth infested areas compared to areas in the open waters and those under water hyacinth mats. The levels of E. coli in the open water areas ranged from undetectable levels to 1140 cfu/100 ml. Whereas, levels of E. coli from areas under water hyacinth mats ranged from 10 cfu/100 ml to 1549 cfu/100 ml while E. coli levels from waters from water hyacinth roots ranged from undetectable levels to 6387 cfu/100 ml. Therefore, general marked differences in levels of E.coli in hyacinth thriving areas with regard to free areas indicate potential ability of the plant to harbor microbiological contaminants and if its spread is left unchecked, incidences of water borne related diseases like the cholera may increase incredibly among the riparian communities with consequent loss of many lives. It is therefore imperative that a plan of action is put in place to control the spread of water hyacinth in Lake Victoria.Publication Lakes Baringo and Naivasha: Endorheic Freshwater Lakes of the Rift Valley (Kenya)(Springer, Dordrecht, 2018-05-16) Omondi, Reuben; Ojwang, William; Olilo, Casianes; Mugo, James; Agembe, Simon; Ojuok, Jacob E.Lakes Baringo and Naivasha are among the Great Rift Valley lakes that were formed about 25 million years ago by violent separation of two of the earth’s continental plates floating on the molten magma of its core. Lake Baringo is a freshwater lake in the eastern arm of Kenya’s Great Rift Valley, with surface and catchment areas of approximately 130 and 6,820 km2, respectively, and a mean depth of 5.9 m. The lake is shallow and is virtually a wetland in its entirety, with submerged Ceratophyllum demersum occurring in the deepest portions of the lake. However, larger marshes are found at the river mouths to the south and east. Lake Naivasha has a surface area of approximately 119,130 km2, a catchment area of 3,200 km2, and a mean depth of 4.1 m. Lake Naivasha’s water level has experienced great fluctuations sometimes as much as 7 m over many years attributed to large-scale climatic influence, also causing changes in water geochemistry. The main lake has a fringing vegetation of Cyperus papyrus and other macrophytes and the lake body supports a diverse macrophyte community. In addition to the lakes’ high biodiversity, they provide water to the local communities for domestic, irrigation, and industrial purposes. Fish in these lakes contribute to the diet of the local communities and are a source of income. Due to their unique scenery and biodiversity, the lakes are destinations for both local and international tourists. Lakes Baringo and Naivasha are faced with numerous threats and challenges including an increasing human population, deforestation and erosion, pollution, impacts associated with tourism, human–wildlife conflict, impact of invasive species, and climate change. Investments around these lakes need to be balanced against the threats to biodiversity and the human population.Publication Macrophytes of Lake Victoria and succession after invasion of Water Hyacinth(AQUA DOCS, 2006) Omondi, Reuben; Kusewa, MwendeThe distribution of Lake Victoria macrophytes is described. Succession of macrophytes in the lake became more dramatic and dynamic after invasion of water hyacinth. The weed pushes and smothers other free-floating macrophytes like Pistia stratiotes. It then provides substrates for the emergent Vossia cuspidata, which later reduces its population by competition for light and nutrients. The noxious weed is believed to have led to extinction of Azolla nilotica in the lake.Publication Phytoplankton community structure and ecology in Lake Naivasha, Kenya(International Journal of Fisheries and Aquatic Studies, 2020-04-21) Owino, Omondi A; Mokua, Ogendi G; James, Onchieku M; Omondi, Reuben; Ombiro, Omweno JThe phytoplankton community structure and ecology of L. Naivasha was studied for a period of six months on a monthly basis between February 2019 and July 2019. The main objective was to determine the phytoplankton species diversity, distribution, and abundance from the seven sampling points in L. Naivasha. A total of one hundred and twenty four (124) species belonging to six (6) taxonomic group were identified. Chlorophyceae was represented by 43 species consisting of 34.68% by species composition, Bacillariophyceae was represented by 38 species consisting of 30.65% by species composition. Cyanophyceae was represented by 24 species leading to 19.35% species composition. Other taxonomic groups included Zygnematophyceae, Euglenophyceae, and Dinophyceae represented by 9 (7.26%), 7 (5.65%) and 3 (2.42%) species respectively. Cyanophyceae recorded the highest abundance in cells/litre, followed by Chlorophyceae and Bacillariophyceae. The total number of algal species was highest in Hippo point with 72 (16.59%) species, followed closely by 68 (15.67%) species in Crescent Island, followed by 66 (15.21%) species in Oserian Bay. Mouth of R. Malewa recorded 59 (13.59%) species, Sher Bay had 58 (13.36%) species, this was followed by Mid Lake station with 56 (12.90%) species, and Sewage Discharge Point had 55 (12.67%) species. Shannon-wiener diversity (H) index ranged from 2.0455 (Mouth of R. Malewa) to 2.7077 (Oserian Bay). In conclusion, Lake Naivasha depicted a higher diversity of phytoplankton species. Results from this study showed the state of L. Naivasha trophic status based on phytoplankton ecology.Publication Relative abundance of mosquitoes and snails associated with water hyacinth and hippo grass in the Nyanza gulf of Lake Victoria(Wiley, 2010-09-16) Ofulla, A.; Karanja, Diana; Omondi, Reuben; Okurut, T.; Matano, A.; Jembe, Tsuma; Abila, Richard; Boera, Priscilla; Gichuki, JohnThis study was conducted from September to December 2008 to investigate the relative abundance of malaria vectors and schistosomiasis host snails associated with aquatic weeds in Nyanza Gulf (Lake Victoria). Larval and adult’s stages of mosquitoes, lakeflies and snails were collected and identified with standard entomological and malacological techniques. The relative species composition and abundance of fish associated with macrophytes were also determined. Physico-chemical parameters were determined with standard analytical methods. Community-based surveys were also conducted, using standard questionnaires, focused group discussions and direct observations. The results of this study indicated that the abundance of malaria-causing mosquitoes was low, accounting for only 0.4% of the total number of mosquitoes and lake flies collected from the gulf. Lake flies (Chaoborus and Chironomus spp.) were the most abundant flying insects associated with aquatic macrophytes (84.2%), followed by Culicines Culex spp. (12.2%) and Aedes spp. mosquitoes (3.2%). Biomphalaria sudanica and Bulinus africanus, the two most common hosts for schistosomiasis in the gulf, were detected in both types of macrophytes, but were most significantly attached to water hyacinth (P < 0.0001) and hippo grass (P = 0.0003). There were significantly fewer snails attached to the hippo grass, compared with those unattached in the open water (P < 0.05, GENMOD). Different habitats exhibited low Secchi disc transparency values, but elevated total phosphorous (TP), total nitrogen (TN), chlorophyll-a concentrations, as well as algal cell counts. Furthermore, Oreochromis niloticus and Haplochromine fishes were more abundant in water hyacinth mats compared with hippo grass mats and open-water habitats. The low mosquito abundance indicated that the sampled habitats were unsuitable for mosquito breeding, likely attributable to water turbulence and/or predation by larvivorous fish. The strong association between B. sudanica and B. africanus and aquatic macrophytes, and the observation that local communities perform many lakeshore-related activities that bring them into contact with water, can potentially lead to a higher prevalence of schistosomiasis in the Nyanza Gulf region.Publication Some aspects of the reproductive biology of Labeo victorianus (Boulenger, 1901) from Kuja-Migori River basin, Kenya(Journal of Fisheries, 2022-03-19) Kembenya, Elijah; Getabu, Albert; Njiru, James; Omondi, ReubenLabeo victorianus is an endemic species to Lake Victoria basin and also a species threatened with extinction status. This study investigated reproductive biology of L. victorianus from Kuja- Migori River basin, Kenya with a view to determining the length weight relationship (LWR), condition factor, fecundity, egg diameter gonado-somatic index (GSI), length at 50% maturity (LM50) and sex ratio. Sampling was done by electrofishing from January 2018 to June 2019. The LWR showed a negative allometric pattern (p < 0.05). The mean condition factor for combined sexes was 1.02. Fecundity ranged from 47842 – 101902 eggs (mean ± SD: 83663 ± 2605 eggs) and correlated highly with body size (r2 = 0.9137). Egg diameter ranged from 0.5 – 0.7 mm. Mean GSI was 6.3 ± 1.6 and 2.8 ± 0.45 for females and males respectively. The LM50 was estimated at 18 cm total length (TL) and 20 cm TL for males and females respectively. Sex ratio did not differ from the expected 1:1. This species has a high fecundity with small sized eggs and males attain sexual maturity earlier than females. The findings of this study provide useful information towards sustainable conservation of L. victorianus in the Lake Victoria basin.Publication Spatial variation in diversity, distribution, and abundance of macroinvertebrates and their response to physicochemical param- eters in River Nyakomisaro, kisii-Kenya(IJTHF, 2020-02-20) Jomo, Boston; Omondi, Reuben; Getabu, Albert; Orwa, PatrickAquatic animal and plant diversity of tropical aquatic ecosystems are severely threatened by frequent anthropogenic activities. The study investigated spatial variation in macroinvertebrate community and physicochemical parameters of River Nyakomisaro from July to December 2016. Five sampling sites were selected and a pool, a rie and a run identied in each site for sampling. Kick sampling was employed in collecting macroinvertebrate samples while selected physicochemical parameters were determined in situ using a water quality multi-parameter meter model 85–15 ft YS1. A total of 6,104 macroinvertebrates belonging to 30 genera, 22 families and 10 orders were recorded. The highest diversity (2.719 ± 0.018) was recorded in station 1 while station 5 had the lowest diversity (1.229 ± 0.026). The highest abundance was recorded in station 5 with 1,948 macroinvertebrates dominated by Chironomids which are highly tolerant to perturbations while station 1 recorded the lowest abundance of 473 macroinvertebrates and dominated by macroinvertebrate communities that are sensitive to environmental pollution. Analysis of variance (ANOVA) showed signicant dierences (p<0.05) in diversity, abundance, and distribution of macroinvertebrates of River Nyakomisaro. Headwater stations had taxa that thrive in undisturbed waters with a reduction of genera that are sensitive to perturbations such as Ephemeroptera, Plecoptera, and Trichoptera in downstream stations. This was a clear indication of pollution of the waters downstream. This response makes macroinvertebrate communities in River Nyakomisaro good bio-indicators of water quality. Therefore, the ndings of the current study can form a basis for the establishment of strategies for conservation, protection, and restoration of macroinvertebrates and the integrity of river NyakomisarPublication Survival and avoidance response of the freshwater gastropod Melanoides tuberculatus (Muller) to different concentrations of tobacco waste(Aquaculture Research, 2012) Ogello, Erick Ochieng; Omondi, Reuben; Opiyo, Mary A.; Charo‐Karisa, Harrison; Munguti, Jonathan; Aura, Christopher MulandaThe Gastropod Melanoides tuberculatus plays a significant role in hampering fish larval production in earthen ponds. This study investigated use of tobacco waste to assess behavioural and survival responses of M. tuberculatus at different concentrations of tobacco waste solution of 0.25, 0.5, 0.75, 1.0, 1.25, 1.5, 1.75 and 2 g L−1. Mean escape time varied significantly among concentrations (P < 0.05). Escape time decreased in 1‐, 2‐ and 3‐day‐old solutions. Percentage survival decreased significantly with increasing concentrations of tobacco waste solution and exposure time (P < 0.05). Concentrations of 1.75 g L−1 and 2.0 g L−1 had high hazard ratios and low survival rates of gastropods and were the most effective in eradication of M. tuberculatus, hence recommended dose for preparing ponds for stocking. We conclude that tobacco waste solution can be used for control of M. tuberculatus.