Masters Candidates

Thesis / Project  Title:POTENTIAL USE OF SELECTED SEAWEEDS AS FEED SUPPLEMENTS ON GROWTH PERFORMANCE AND SURVIVAL OF NILE TILAPIA (Oreochromis niloticus -Linnaeus, 1758) FINGERLINGS.

Thesis / Project  Abstract:

The study investigated the growth performance of Oreochromis niloticus fingerling fed seaweed (Hypneacornuta and Hypneamusciformis) supplemented diet, with freshwater shrimp (Caridinanilotica) as the protein ingredient. Three species of seaweeds (H.cornuta, H.musciformis and Ulva reticulata) were sampled and tested for their protein content andit was highest in H.cornuta (22.4±0.07 mg/g) and H.musciformis (21.52±0.08 mg/g) as compared to U. reticulata (11.69±0.16 mg/g. Five experimental diets containing 20% H.cornuta, 30% H.cornuta, 20% H.musciformis, 30% H.musciformis and the control dietcontaining no seaweed were formulated. A total of 450 O. niloticus male fingerlings (mean weight =1.42g) were obtained from Green Algae Farm, Sagana. The experiment was conducted for a duration of 60 days. O.niloticus fed on 20% H. cornuta recorded the highest weight gain (9.30±0.24g). Condition factor ranged from 1.21±0.05 to 1.84±0.03 and was above one in all the diets, indicating good fish health and culture conditions. The highest Specific Growth Rate (SGR) was on fingerlings fed 20% H. cornuta diet (3.27±0.03). Feed Conversion Ratio (FCR) was at 1.4 across all the diets indicating an optima FCR. Therefore, this study suggests that 20% H. cornuta can be a supplement on O. niloticus fingerling diet since it performed slightly better on weight gain and, in other growth parameter aspects. This information will benefit seaweed farmers, fish farmers, and fish feed producers searching for more species or feed ingredient to exploit

Thesis / Project Title: EFFICACY OF CLARIAS ALLUAUDI AS A BIOCONTROL AGENT FOR ANOPHELES MOSQUITOES

Thesis / Project Abstract:

More research is being tailored towards the biological control of malaria mosquitoes due to resistance of the mosquitoes to insecticides in use. Larvivorous fishes recommended for mosquito control are introduced voracious species that pose an extinction danger to native fauna and flora. This study tested the efficacy of a native catfish (Clarias alluaudi) in controlling malaria mosquitoes. The larvivorous efficacy was evaluated on basis of the speed at which a fish took to apprehend mosquito larva/pupa availed (exposure time), selective predation on An. gambiae and Ae. aegypti larvae and pupae by the fish, and its predatory index. Gambusia affinis and Poecilia reticulata were used as positive controls. Generalized linear models were used to document differences in the exposure times, feeding preferences and predatory indices among the three fish species. Clarias alluaudi exhibited the shortest exposure time amongst the three fish species when offered mosquito pupae. The fish took a significantly shorter time to apprehend Ae. aegypti larvae as compared to An. gambiae larvae. In selective predation experiments, C. alluaudi preferred late instar larvae of Ae. aegypti over An. gambiae. Late instar larvae were preferred over pupae in all experiments consisting of the two developmental stages, irrespective of the fish species. Whereas Clarias alluaudi consumed the highest number of prey items amongst the three fish species per day, it had the lowest predatory index, which was measured as the mean number of mosquitoes consumed per unit weight of a fish per day. Results obtained point towards possible deployment of C. alluaudi into mosquito breeding habitats for mosquito control purposes.

Thesis / Project  Title: Evaluation of Known Visual and Chemical Cues for Surveillance of the Dengue and Chikungunya Vector, Aedes aegypti, in Busia and Kilifi counties, Kenya.

Thesis / Project Abstract:

Aedes aegypti is the major vector of the arboviral pathogens, zika virus, yellow fever, dengue and chikungunya viruses. Several outbreaks due to these infections in humans are well documented in various parts of the world, Kenya included. Vector-based surveillance is critical for effective prevention and control of these arbovirus infections in human. Improved trapping of vector populations forms an essential component of surveillance and become part of disease risk assessment which results into a decreased morbidity and mortality that may be attributed to these diseases. This study sought to improve trapping of adult Ae. aegypti populations by exploiting visual (light) and odor cues, which insects including mosquitoes rely on for host location. Trap performance in terms of counts for each treatment were compared in R using GLM, relative to controls at 95% confidence level of significance.

First, attractiveness of Ae. aegypti populations to known light colors were evaluated in field set up. Second, the effect of combining odor cues Linalool oxide (LO) and hexanoic acid (HA) on catches of Ae. aegypti was similarly evaluated in field trials.

The findings confirm the visual attractive effect of BG trap alone to Ae. aegypti with differential but marginal effect of UV or incandescent light on trap catches. Also, the data indicate that combining plant- and human-derived odors may elicit a masking effect in trapping this vector. Thus, the usefulness of combining plant and animal odorants in Ae. aegypti trapping needs further investigation. The results underscore the importance of detailed knowledge of interactive effect of combining plant and animal odorants for proper lure formulation and development.

Thesis / Project Title: Anopheles productivity of aquatic habitats created through artisanal capture fishing on Mageta Island in Western Kenya

Thesis / Project Abstract

The effect of physicochemical characteristics of mosquito larval habitats on Anopheles productivity is not well known. To fill this knowledge gap, a cross-sectional survey was carried out on Mageta Island, western Kenya. Habitats were classified either as those created by or associated with artisanal capture fishing (ACF) activities on the Island or non-ACF. Physicochemical parameters and Anopheles mosquito larval density were recorded for each habitat type. The degree of association between Anopheles larvae/pupae and the physicochemical factors was tested using generalized linear models. High numbers of Anopheles larvae and pupae were found in habitats associated with ACF activities. Habitats with wooden bottom surfaces had more larvae than those with mud and rock bottom surfaces. Perimeter, TSS, temperature and conductivity influenced larval abundance significantly. Other factors interacted resulting in significant associations with Anopheles larval abundance. These were TDS with conductivity, TSS with DO and TSS with temperature. Even though individual physicochemical characteristics could be linked to density of Anopheles larvae and productivity of mosquito habitats, the results indicate that certain variables interact to regulate mosquito abundance. Malaria control measures tailored towards manipulating physicochemical characteristics in mosquito breeding sites should be adopted in integrated mosquito control programmes.

Thesis / Project  Title: Meiofauna and nematode community assemblage as indicator of sediment disturbance: a case study at Mida Creek, Kenya

Thesis / Project  Abstract

The aim of the study was to evaluate the potential of nematodes as indicators of sediments disturbance following polychaete bait harvesting. The study was conducted in 3 stations at Mida Creek, Kenya with different intensity in bait harvesting. Samples were collected from the mudflats next to the mangrove forests during low tide, fixed in 5% formalin and transported to the laboratory for processing and identification.

Most meiofauna taxa did not vary much between the stations except nematodes that had a higher relative abundance in the undisturbed station (71% in Dabaso, 56% in Kirepwe 59 % and in Mayonda). Nematode community changed from a high number of species with high dominance in the less disturbed and none-disturbed to a low number and low dominance in the disturbed station.

The most dominant genera differed between stations being Spirinia and Terschellingia in Dabaso and Kirepwe and Viscosia, Pontonema, Synochium, Haliplectus, and Pheronusincreased in numbers in disturbed quadrats. Measures such as educating the fishermen on the effects of digging of polychaete should be emphasized to safe guard the marine biodiversity and its ecosystem.

Mayonda was characterised by low nematode diversity (H’) and low dominance while the other two stations had higher diversity and dominance. The difference in nematode community between stations indicates that nematodes have the potential of indicating sediment disturbance through genera composition and diversity.

KEY WORDS: Bait harvesting, Meiofauna, Nematodes, Biomonitoring, Mida Creek, Kenya

Moringa oleifera tree has medicinal and nutritional propertiesand the tree is excessively harvestedfor food and medicine. Therefore in vitro propagation is significant for rapid and enhanced production of disease free planting materials and secondary compounds to meet the demand. This study regeneratedMoringa oleifera in vitro and determed if its callus extracts could inhibit fungal growth. Seeds were sterilized in 30% commercial bleach (JIK) followed by 70% ethanol. The seeds were inoculated on Murashige and Skoog, (1962) (MS) media, half MS media and MS with 0.5-6.5 mg/l Gibberellic acid (GAз) to germinate. Callus was generated from inter-nodal segments, leaf discs and hypocotyls on MS with 0.25-2 mg/l 2,4D, NAA, TDZ or BAP. Shoots were induced from callus and nodal explantson medium with BAP, NAA, MTR, TDZ and KIN or their combinations. Micro shoots were rooted on MS basal or MS supplemented with NAA, BAP or MTR. Rooted shoots were acclimatized and hardened on vermiculite mixed with peat moss (1:3). Callus and leaf extracts were tested against Candida albicans, Aspergillus flavus and Fusarium semitectum.Intact seeds on MS or half MS medium germinated within 8-14 days. Seeds with seed coats removed started germinating 3 days post inoculation. Callus induction was optimum at 0.5 mg/l 2,4D. Shoot induction from callus was not successful as callus only developed green spots or shoot like structures on the surface. MTR 1.0 mg/l initiated 9.3 shoots from nodal explants in 3 days which increased to 11.3 shoots when combined with 0.5 mg/l KIN. Best rooting occurred on MS basal. Extracts from callus and leaves inhibited growth of Fusarium semitectum at 62.5mg/land of Aspergillus flavus at125mg/l but could not inhibit Candida albicans growth. This study has demonstrated the regeneration potential of Moringa oleifera and the antifungal activity of the callus extract.

Floodplain fisheries resources are under frequent disturbances due to seasonal variation in flood peaks and intensity. This study investigated the influence of flooding on fish diversity and fisheries patterns in the floodplain lakes of lower Tana river, Kenya. Fish diversity and abundance in the floodplain lakes were assessed in relation to changes in space and flooding period. The impacts of seasonal flooding on annual fishing pattern and governance in the Tana River delta lakes was also investigated. Fish was sampled by using monofilament gillnets, and six water quality parameters (pH, temperature, dissolved oxygen, electrical conductivity, salinity and water clarity (turbidity)) recorded using multi-metre probe (YSI Model 85/50) and turbidity tube at three sampling points in each lake in pre-flood, during flood and post-flood period. A total of 2982 fish comprising 15 species in 9 families, were captured. The predominant species in the floodplain lakes were Zanzibar barb (Enteromiuszanzibaricus, 41%), Gregori’slabeo (Labeogregorii, 11%), Red-fin robber (Brycinusaffinis, 8%) and Sabaki tilapia (Oreochromis spirulus, 7%). Non-metric multidimensional scaling (nMDS) plots showed a high similarity of fish assemblages during floods in the floodplain lakes. Pearson’s correlation matrix showed fish abundance was positively correlated with increasing dissolved oxygen (p<0.01), and water depth (p<0.05). Hydrological connectivity influenced fish species composition and abundance. This study therefore recommends preservation of river-floodplain connectivity to conserve fish biodiversity in the floodplain lakes.