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Ecology and Management of Lake Naivasha, Kenya, in Relation to Climatic Change, Alien Species' Introductions, and Agricultural Development
(Environmental Conservation; Cambridge Journals, 1990) Harper, David, M.; Muchiri, Mucai; Mavuti, Kenneth, M.
Lake Naivasha is an important freshwater resource for Kenya's foreign-currency-earning agriculture and tourism, and for water-supply. It has always experienced extensive water-level fluctuations as a consequence of irregular rainfall patterns that are affected by continental-scale climatic events, and its communities — particularly of aquatic plants — were adapted to these changes.
Ecological studies of the Helminth parasites of fish in Lake Naivasha, Kenya
(Karatina University, 1999) Aloo, P. A.
In many parts of the world, wild stocks of fish are dwindling especially in Africa where drought, pollution and over-exploitation are some of the causative factors. The continent is not spared other climatic catastrophies such as global warning with its effects on the flora and fauna (both terrestrial and aquatic). This may lead to the manifestation of diseases caused by parasitic organisms, which have been known to co-exist with their hosts. The work reported here attempted to highlight the importance of studying the ecological relationship between parasites and their hosts in their wild environments i.e. the microhabitats (fish) and the macrohabitat (the lake). This work aimed at determing the distribution of four teleostean fishes Oreochromis leucostictus (Trewavas), Micropterus salmoides (Lacepede). Tilapia zillii (Gervais) and Barbus amphigrama (Boulenger) as hosts of the parasites, to establish the occurrence and prevalence of helminth parasites in each of the four species and to determine and quantify the relationships between the helminth parasites and the teleostean hosts. The distribution of the four fish species as hosts of the helminth parasites was studied for a period of two years. The occurrence of the helminth parasites, intensity of infection in each species, prevalence of each parasite on each host, differential establishment, seasonal variation in prevalence and intensity of infection and the effects of these parasites on their hosts were determined. The effect of water chemistry on the intensity of infection was established by comparing the main Lake Naivasha which is fresh and the more saline Oloidien Bay. Statistical tests used to establish the relationship between the parasites and their hosts were the chi-square, analysis of variance, split-plot technique and regression analysis. The results showed a significant variation in the monthly distribution of the fish species within the lake (F11,32=4.07, P<0.001). Fish abundance also varied within the sampling sites with Oreochromis leucostictus being the most abundant. Depth was found to be the only single factor influencing the distribution of fish in the lake with fish numbers decreasing with depth (b=3.04; t11=4.15, P<0.01). It was established that there are four helminth parasites whose larval stages infect Lake Naivasha fishes viz: a nematode, Contracaecum sp.; an acanthocephalan Polyacanthorhynchus kenyensis, a trematode Clinostomum sp and a dilepidid cestode of the genus Amirthalingamia. A differential establishment of these parasites on the hosts was observed. (F5,2860 =14.044; P<0.001). No significant variation was observed in the monthly occurrence of the parasites (F11,132=1, P>0.05). Host specificity was also revealed among the parasites with two parasites Clinostomum and Amirthalingamia being very specific on O. leucostictus and T. zillii respectively (F15,2860=21.63; P<0.001). A strong relationship between the intensity of infection and the sex of the fish was also revealed (X2(1)=64.43; P<0.001). Although the relationship between the age of the fish and the intensity of infection with Contracaecum sp. was not significant (t4=0.425;P>0.05), the intensity of infection of O. leucostictus with P. kenyensis increased with age (t4=7.061; P>0.01). These parasites showed no harmful effects no harmful effects on their host from the observation of the relationship between intensity with Contracaecum and the condition factor of the fish (F3,33=0.02; P>0.05). In conclusion, Lake Naivasha fish species do not harbour any ectoparasites but they are infected by larval stages of four endoparasites
Organochlorine and organophosphorus pesticide concentrations in water, sediment, and selected organisms in Lake Naivasha (Kenya)
(Kluwer Academic Publishers, 2002) Muchiri, Muchai; Gitahi, S. M.; Harper, D. M.; Tole, M. P.; Ng’ang’a, R. N.
Effect of temperature on the development of Orius albidipennis Reuter, a predator of the African legume flower thrips, Megalurothrips sjostedti Trybom
(2002) Gitonga, L. M.; Löhr, B.; Overholt, W. A.; Magambo, J. K.; Mueke, J. M.
The effects of temperature on the development of Orius albidipennis (Reuter) (Hemiptera: Anthocoridae), reared on its prey, Megalurothrips sjostedti (Trybom) (Thysanoptera: Thripidae), were studied in the laboratory. Nymphal mortality was 87, 48 and 38 % at 20, 25 and 30 °C, respectively. With the exception of first-instar nymphs, percentage mortality was lowest at 25 °C. Pre-oviposition period and longevity decreased with an increase in temperature. Mean daily and total fecundity were 2.1 and 76.4 respectively at 25 °C. The mean developmental period from oviposition to adult eclosion was 27.7, 14.1 and 10.9 days at 20, 25 and 30 °C respectively. There was a linear relationship between temperature and developmental rate (1 /day) of O. albidipennis. Lower thermal thresholds were 13.8, 13.5, 12.7, 15.0, 13.8 and 12.5 °C for eggs and nymphal stages 1 to 5, respectively, with the corresponding average degree-day requirement of 46.9, 42.6, 33.3, 29.2, 26.1 and 51.4 days, respectively. The implications of these results for biological control of thrips are discussed.
The status and future of the Lake Naivasha fishery, Kenya
(Kluwer Academic Publishers, 2002) Muchiri, Mucai; Kundu, Rodrick; Taylor, Andy; North, Rick; Harper, David M.; Bailey, Roland; Hickley, Phil
Lake Naivasha is a freshwater lake situated in the eastern rift valley of Kenya. Only five species of fish are present, all of which have been introduced. They are Oreochromis leucostictus, Tilapia zillii, Micropterus salmoides (largemouth bass), Barbus amphigramma and Poecilia reticulata (guppy). The first three of these form the basis of an important gill net fishery and bass are also taken by rod and line for sport. Barbus are occasionally caught by dip net. Actual and potential yields for the Lake Naivasha fishery are discussed and the fishery is shown to be under-performing. The feeding regimes of the commercially exploited fish were examined in the context of available food supply, in particular the benthic fauna. Small bass depend heavily on Micronecta and large bass mostly take crayfish. Detritus predominates in the diet of Oreochromis leucostictus and Tilapia zillii but the former also eats algae and the latter, Micronecta and macrophyte. Various food resources, especially the benthos, appear to be under-utilized and so it is possible that further species could be introduced to enhance the commercial fishery.
Functional response of Orius albidipennis (Hemiptera: Anthocoridae) to Megalurothrips sjostedti (Thysanoptera: Thripidae)
(Karatina University, 2002-05-02) Gitonga (a), Linus M.; Löhrb (b), B.; Magambo (a), J. K.; Mueke (c), J. M.
A locally available anthocorid predator, Orius albidipennis Reuter, was evaluated as a candidate biocontrol agent for Megalurothrips sjostedti Trybom, a major pest of French beans, Phaseolus vulgaris (L), in Kenya. The functional response of adult O. albidipennis to larval and adult M. sjostedti was studied at 15, 25, and 28 °C and densities of 5, 10, 20, and 30 larval and adult M. sjostedti per cage, over 24 h. More larvae and adult M. sjostedti were killed at the higher densities and with an increase in temperature. The data provided good fit to both type I and II functional response models. Attack rates increased with temperature for both the second instar larva and adult M. sjostedti. Handling times for the larvae decreased with an increase in temperature while those for the adults increased with increase in temperature. The implications of these results are discussed.
Functional response of Orius albidipennis (Hemiptera: Anthocoridae) to Megalurothrips sjostedti (Thysanoptera: Thripidae)
(Karatina University, 2002-05-02) Gitonga, Linus M.; overhalt, W.A.; Löhr, B.; Magambo, J. K.; Mueke, J. M.
A locally available anthocorid predator, Orius albidipennis Reuter, was evaluated as a candidate biocontrol agent for Megalurothrips sjostedti Trybom, a major pest of French beans, Phaseolus vulgaris (L), in Kenya. The functional response of adult O. albidipennis to larval and adult M. sjostedti was studied at 15, 25, and 28 °C and densities of 5, 10, 20, and 30 larval and adult M. sjostedti per cage, over 24 h. More larvae and adult M. sjostedti were killed at the higher densities and with an increase in temperature. The data provided good fit to both type I and II functional response models. Attack rates increased with temperature for both the second instar larva and adult M. sjostedti. Handling times for the larvae decreased with an increase in temperature while those for the adults increased with increase in temperature. The implications of these results are discussed.
Temperature-dependent development of Megalurothripssjostedti and Frankliniellaoccidentalis (Thysanoptera: Thripidae)
(2002-09) Gitonga, Linus; Lohr, B.; Overholt, Bill; Magambo, J. K.
Megalurothrips sjostedti (Trybom) and Frankliniella occidentalis (Pergande) (Thysanciptera: Thripidae) are among the most serious pests of French beans, Phaseolus vulgaris var. Monel in Kenya and occur in all major growing areas. The former seems to be prevalent during cold and rainy periods while the latter is mainly a problem during hot and dry conditions. The development of the two species was studied at temperatures ranging from 15 degreesC to 30 degreesC. The average developmental times of each stage are given. For both species, the developmental times decreased with an increase in temperature. The degree-days required to complete development from egg to adult were 212 and 256 above the estimated threshold temperatures of 9.6 degreesC and 9.0 degreesC for M. sjostedti and F.occidoitalis, respectively. Between 19 and 23 generations of M. sjostedti and between 17 and 20 generations of F. occidentalis; could possibly develop under Kenyan field conditions in one year. Overall mortality was lowest at 25 degreesC. Mortality rates for both species decreased from larval instars to adult and were higher for M. sjostedti than for F. occidentalis. Since the developmental times were not different, the differential pest status of M. sjostedti and F. occidentalis must be a result of other factors.
Environmental assessment of the East African Rift Valley lakes
(Aquatic Sciences, 2003) Odada, Eric, O.; Olago, Daniel, O.; Bugenyi, Fred; Kulindwa, Kassim; Karimumuryango, Jerome; West, Kelly; Ntiba, Micheni; Wandiga, Shem; Aloo-Obudho, Peninah; Achola, Pius
An assessment of the East African Rift Valley lakes was initiated by the United Nations Environment Programme (UNEP) with funding from Global Environment Facility as part of the Global International Waters Assessment (GIWA). The purpose of GIWA was to produce globally comparable assessments and examine stresses on international waters: marine, coastal and fresh; surface and groundwaters. The assessment of the East African Rift Valley lakes was undertaken from the perspective of water quality and quantity, associated biodiversity and habitats, their use by society and societal causes of the regionally identified issues and problems. Assuming intrinsic values of aquatic ecosystems, the assessment of social perspective focused on human use of water and considered the incremental costs of measures to encourage sustainable development. The assessment identified the major concerns facing the East African Rift Valley lakes. By and large, pollution and unsustainable exploitation of fisheries and other living resources emerged as critical concerns attributable to human activities. East Africa has a very high concentration of humans and economic activities. Pollution is from uncontrolled discharge of wastes directly into the lakes. Unsustainable exploitation of fisheries and other living resources is caused by over-fishing, destructive fishing practices, and introduction of non-native species that affect the composition of the native communities, resulting sometimes in the collapse of certain species and dominance by resilient ones. Loss of biodiversity also was identified as a major concern; and the issues of excessive by-catch and discards are also relevant. Trawling using undersized mesh-nets for target species and indiscriminate fishing gear or poison is serious, in most cases resulting in indiscriminate catches, including juvenile fish. Given the transboundary nature of the issues identified in this assessment, appropriate multilateral policy and institutional arrangements need to be established in East Africa to address the main concerns of these large lakes. Riparian countries must pay attention to the regional management of these transboundary water bodies, and appropriate planning of human population sizes and their settlement, land-use and waste disposal to control pollution. Although East African lakes contribute relatively little emission of greenhouse gases, there is a need to reduce the rate of deforestation and even restore cleared areas since forests serve as sinks of greenhouse gases towards mitigating adverse climatic changes.
Biological diversity of the Yala Swamp lakes, with special emphasis on fish species composition, in relation to changes in the Lake Victoria Basin (Kenya): threats and conservation measures
(Biodiversity & Conservation, 2003-05) Aloo-Obudho, Peninah
During the second half of the last century, the Lake Victoria ecosystem has undergone drastic ecological changes. Most notable has been the decline in the populations of many endemic cichlid fishes. The lake has lost nearly 200 haplochromines and one tilapiine, Oreochromis esculentus. The above changes have been attributed to effects of species stocking and, in particular, from predation pressure by the introduced Nile perch, Lates niloticus. Other factors that have led to the decline of the endemic species include intensive non-selective fishing, extreme changes in the drainage basin, increased eutrophication, and the invasion of the lake by the water hyacinth, Eichhornia crassipes. However, the remnants of some species that had disappeared from Lake Victoria occur abundantly in the Yala Swamp lakes (Kanyaboli, Sare and Namboyo). This paper discusses the biodiversity of the swamp and the three lakes and gives suggestions for their conservation.
Biological diversity of the Yala Swamp lakes, with special emphasis on fish species composition, in relation to changes in the Lake Victoria Basin (Kenya): threats and conservation measures
(2003-05) Aloo, P.A.
During the second half of the last century, the Lake Victoria ecosystem has undergone drastic ecological changes. Most notable has been the decline in the populations of many endemic cichlid fishes. The lake has lost nearly 200 haplochromines and one tilapiine, Oreochromis esculentus. The above changes have been attributed to effects of species stocking and, in particular, from predation pressure by the introduced Nile perch, Lates niloticus. Other factors that have led to the decline of the endemic species include intensive non-selective fishing, extreme changes in the drainage basin, increased eutrophication, and the invasion of the lake by the water hyacinth, Eichhornia crassipes. However, the remnants of some species that had disappeared from Lake Victoria occur abundantly in the Yala Swamp lakes (Kanyaboli, Sare and Namboyo). This paper discusses the biodiversity of the swamp and the three lakes and gives suggestions for their conservation
Post-2015 Development Planning: Adaption of a Holistic Approach to Planning and Research - a Commentary from a Practitioner’s Perspective
(International Journal of Innovation and Economic Development, 2004) Kiambati, Kellen; Itunga, Julius
In this article, we analyse the argument that lack of holistic approach in planning and research have contributed to the lack of sustainable development in Africa. We base our discussion on the speech by the special advisor on the national consultation on the post-2015 development as it relates to Uganda and other African Context (held on 8th August 2015). The advisor was convinced that there is a need to adopt a more integrated and comprehensive planning approach to reinventing traditional development tools, and meeting persistent and emerging challenges. Efforts must be made to start putting in place the practical measures, markers, mechanisms and partnerships that make sustainable advancements possible. Scholars and managers are called upon to take the challenge of demonstrating how the adoption of a holistic approach in planning, and research can contribute to sustainable development.
Shifts in the food of Nile tilapia, Oreochromis niloticus (L.) in Lake Victoria, Kenya
(African Journal of Ecology, 2004) Muchiri, M.; Cowx, I. G.; Okeyo-Owuor, J. B.; Njiru, M.
Metazoan Parasites of Some Commercially Important Fish along the Kenyan Coast
(WIOMSA, 2004) Aloo-Obudho, Peninah; Anam, R.O.; Mwangi, J.N.
The parasitic fauna of some commercial fish species along the Kenyan coast was investigated at four localities between August 2001 and March 2002. The study was carried out to establish the extent of parasitisation of different fish species and quantify the relationship between the parasites and their fish hosts. Fish samples were collected once a month from four landing beaches. Sixteen fish species were examined out of which only eight were infested with ecto-and endo parasites. The infested fish species included: the rabbitfish (Siganus sutor), the mackerels (Selar crumenophthalmus, Scomberomorus commerson and Rastrelliger kanarguta), parrot fish (Leptoscarus vagiensis), sardine (Sardinella gibbosa), tuna (Thunnus sp.) and needle fish (Hemiramphus far). Of the eight species, Si. sutor was most infested with parasites while Sardinella and Leptoscarus were primarily infested with ectoparasites (isopods). Intensity of infestation increased with age (size), especially in Si. sutor, where very young fish had a low infestation rate, while adults were heavily infested (P < 0.01). No significant differences were observed in the intensity of infestation between sexes in Si. sutor (P > 0.05).
Habitat degradation and subsequent fishery collapse in Lakes Naivasha and Baringo, Kenya
(2004) Muchiri, Mucai; Hickley, Phil; Boar, Rosalind; Britton, Robert; Adams, Chris; Gichuru, Nicholas; Harper, David
Lakes Naivasha and Baringo in the eastern Rift Valley of Kenya are shallow, freshwater lakes that are subject to major fluctuations in water level and suffer from habitat degradation as a consequence of riparian activity. Lake Naivasha is approximately 160 km2, is bordered by Cyperus papyrus and its aquatic macrophytes are in a state of flux. The most significant riparian activity is the large scale production of flowers for the European market. Lake Baringo is approximately 140 km2 and lies in a semi-arid region. Its most noticeable feature is its extreme turbidity which is mainly due to excessive soil erosion resulting from deforestation and overgrazing. This turbidity has led to near extinction of submerged macrophytes and a lake bed virtually devoid of benthic fauna. Fishing pressure has added to the environmental stresses being endured by the fish populations and commercial catches have been detrimentally affected. Accordingly, periods of fishery closure are now imposed upon both lakes. Limited remedial action is feasible and some local stakeholders are attempting to introduce mitigation measures. For Lake Naivasha there is an agreed riparian owners' management plan which tackles issues such as water usage and protection of the C. papyrus margin. For Lake Baringo there is a Rehabilitation of Arid Environments initiative which promotes such activities as restoration of riparian vegetation and appropriate stock management.
Exotic introductions to the fishery of Lake Victoria: What are the management options?
(2005) Muchiri, M.; Knaap, M. van; Cowx, I. G.; Waithaka, E.; Njiru, M.
Antimicrobial acitivity of extracts from Tephrosiavogelii Hook F.
(Jomo Kenyatta University of Agriculture & Technology (JKUAT), Kenya, 2006) Wanga, B. N.; Akenga, T.; Imbuga, M.; Gitonga, L.; Olubayo, F.; Namungu, P.
The dichloromethane extracts of the root and leaf of Tephrosia vogelii Hook F. (Family: Papilionaceae) grown in Kenya, were subjected to antimicrobial assays against Staphylococcus aureus, Escherichia coli and Fusarium phoseolida. The minimum inhibition concentrations (MIC) ranged between 0.25 to 6.4 μg/ml for all the microorganisms tested. The crude root and leaf extracts were also toxic to the brine shrimps, organisms used as indicators of toxicity (LC50: 0.960; 0.958μg/ml,respectively). Chromatographic separation led to the identification of (6aß, 12aß, 5'ß)-6a, 12a, 4',5'-tetra hydro-2,3-dimethoxy 5'-ß- isopropenyl–furano (3',2': 8,9)-6H-rotoxen-12-one, (rotenone) in 9.75% yield, (roots), and 11.75% (leaves). Characterisation was achieved by use of spectroscopic techniques and comparison with rotenone standard and literature data. Novel HPLC conditions for purification of rotenoids were established. The MIC of rotenone against the tested microbes was found to be 5.2 and 1.0 μg/ml for Staphylococcus aureus and Escherichia coli respectively, while the LC50 against the brine shrimps was found to be 3.20 μg/ml. The findings indicate that the extracts of T. vogelii contain metabolites that have antimicrobial activity comparable to other medicinal plants.
The Critical Onion Growth Stages For Selective Protection From Thrips Tabaci Lindeman (Thysanoptera:Thripidae) Infestation
(Kenya Agricultural Research Institute, Nairobi (Kenya), 2006-01) Waiganjo, M. M.; Sithanantham, S.; Mueke, J. M.; Gitonga, L. M.
Field trials were conducted during 2000-2001 at KARIandrsquo;s Mwea-Tebere and Kiboko farms to establish the effect of onion thrips, Thrips tabaci Lindeman on onion bulb yields and to identify the critical onion growth stage for selective protection from the pest infestation. Yield reductions of 59 and 27% were recorded in the first and second crops respectively at Mwea-Tebere, but no significant yield reductions were observed in a third crop grown at Kiboko with low thrips infestation. A significant onion yield response to thrips infestation was observed during the 2nd month after transplanting (bulb-formation) and 3rd month after transplanting (bulb-enlargement), but no significant response was observed during the 1st month (pre-bulbing) and 4th month (maturation stage). Onion protection during bulb-formation and enlargement stages only, resulted in higher marginal returns than full season pesticide application. The studies suggest that control recommendations for onion could be refined to optimize need-based protection.
Biological impact of the exotic parasitoid, Diadegma semiclausum (Hellen), of diamondback moth, Plutella xylostella L., in Kenya
(Karatina University, 2006-08) Momanyi, Caleb; Loehr, Bernhard; Gitonga, Linus
Diadegma semiclausum (Hellen) was introduced to Kenya from Taiwan for the control of diamondback moth (DBM), Plutella xylostella L., and released for the first time in July 2002. Seven and twelve months after release, field mortality studies using the cage exclusion method were conducted at two release sites (Werugha/Taita Hills and Tharuni/Central Kenya). Four treatments were applied: fully closed and partially open cages, both with and without glue applied to the base of the plants for the exclusion of crawling predators. During this time interval, parasitism of exposed larvae rose from 15 to 60% at Werugha and from 8 to 18% at Tharuni, with a concomitant decrease of parasitism by indigenous parasitoids. Crawling predators did not seem to have an effect on mortality. Unexplained mortality increased by half between the first and second experiment at both sites, indicating additional mortality due to the parasitoid. A subsequent field simulation with different parasitoid populations showed that in the presence of parasitoids more larvae died because of abandoning the plant than due to parasitism. Dissections of larvae on the ground showed most were parasitized. Thus, it appears that mortality due to D. semiclausum is more than twice the measured rate of parasitism. Additional information on parasitism was collected from concurrently executed DBM yield loss trials. Parasitism by D. semiclausum was in the same range as in the cage exclusion method. Seven months after release, local parasitoids were present at Werugha and dominant at Tharuni, after one year, they were almost completely displaced at both locations.
Lake Baringo: Addressing threatened biodiversity and livelihoods
(Lakes & Reservoirs: Research & Management, 2006-12) Odada, Eric, O.; Onyando, Japheth, O.; Aloo-Obudho, Peninah
Lake Baringo is a shallow, internal drainage, freshwater lake located in the Kenyan Rift Valley. The lake is an important source of water for humans and livestock, as well as a significant income source for local communities through activities such as tourism, biodiversity conservation, and fish sold in local markets. The lake has been subject to overfishing, as well as to greatly enhanced sedimentation as a result of land use changes in the drainage basin. This paper provides an analysis of the conditions prevailing at Lake Baringo, and examines in detail the management response to the problems facing the lake. The roles of the many and varied institutions in the lake basin's management are discussed, and an analysis of internationally funded projects designed to ameliorate the situation is provided.