Growth, mortality and recruitment of Nile perch Lates niloticus (L. Centropomidae) in the Nyanza Gulf of Lake Victoria: an evaluation update

A reassessment of the estimates of growth, mortality and recruitment patterns of Nile Perch, Lates niloticus was made based on data from commercial landings collected during the Catch Assessment Survey Programme. Two sets of length frequency data, one each from beach seining and hook and line fisheries, were analyzed. Values of L8 = 169 and 230 (cm TL) and K= 0.18 yr-1 and 0.195 yr-1 were obtained. The total mortality estimates from the catch curve analysis were Z = 0.72 yr-1 and 0.94 yr-1, respectively, with a natural mortality M of about 0.35 for a mean environmental temperature of 27oC. The highest peak for recruitment was in November, December and January with a minor one in June, indicating recruitment of two cohorts per year. These results are discussed and compared to previously available information on L. niloticus in Lake Victoria

Growth, mortality and recruitment of Nile perch Lates niloticus (L. Centropomidae) in the Nyanza Gulf of Lake Victoria: an evaluation update

A reassessment of the estimates of growth, mortality and recruitment patterns of Nile Perch, Lates niloticus was made based on data from commercial landings collected during the Catch Assessment Survey Programme. Two sets of length frequency data, one each from beach seining and hook and line fisheries, were analyzed. Values of L8 = 169 and 230 (cm TL) and K= 0.18 yr-1 and 0.195 yr-1 were obtained. The total mortality estimates from the catch curve analysis were Z = 0.72 yr-1 and 0.94 yr-1, respectively, with a natural mortality M of about 0.35 for a mean environmental temperature of 27oC. The highest peak for recruitment was in November, December and January with a minor one in June, indicating recruitment of two cohorts per year. These results are discussed and compared to previously available information on L. niloticus in Lake Victoria.Growth, Mortality, Recruitment, Kenya, Victoria L., Nyanza Gulf, Lates niloticus

The role of macrophytes in the economy of the lower Sondu-Miriu river of Lake Victoria

This paper highlights the results of a 12 month's ecological study of macrophytes and their role in the economy of the lower Sondu-Miriu river of Lake Victoria. A total of 34 species of aquatic macrophytes were identified. These were grouped as emergent, floating leaved, free floating and submersed. The major community type identified were dominated by Cladium jamaicanse (Crantz) Kurk., Cyperus paprus (L.) and Cyperus latifolius (Poir). The study observed an over dependence on macrophytes by the local community for the supply of bedding, grazing fields, fuel, roofing and other building materials. The white (heart) of Typha shoot, Nile cabbage (Pistia stratiotes and a legume solanum nigrum traditionally known as "osuga" are used as vegetables by local community. The only source of protein in this arid region is the fish caught in the swamps and birds which inhabit the swamp. The swamp provides the only source of green pasture in the dry season for the animals. An export oriented economy has developed involving mat making and basket weaving with exports reaching as far as Japan. The study proposes a rational and sustainable exploitation of the littoral zone to support the adjacent rural community

Performance assessment of water delivery to a smallholder irrigation scheme in Zimbabwe: Nyanyadzi case study

A research paper illustrating how potential benefits from smallholder irrigation schemes are rarely realised due to unsatisfactory performance of their water delivery systems in rural Zimbabwe.The potential benefits from smallholder irrigation schemes are rarely realised due to unsatisfactory performance of their water delivery systems. A study was conducted to quantify and evaluate water delivery performance indicators of adequacy (Ad), equity (Eq) and dependability (Dp) in three sub-blocks of Nyanyadzi smallholder irrigation scheme using water requirement analysis and a questionnaire survey. The water delivery performance evaluation was carried out between October 1996 and January 1997 for two maize crops under supplementary irrigation and for two consecutive irrigation cycles. Water supply adequacy (ratio of supply to demand) in the first cycle was good (Ad>1.21) and became marginally good (0.96 to 1.01) and poor (Ad0.2) at 73 percent of the 42 locations studied in the canal network. Results of a questionnaire survey revealed that the performance of the water delivery system was consistently low. Poor adequacy, equity and reliability of water supply were perceived respectively by 57 percent, 53 percent and 77 percent of the 30 irrigators interviewed. It was concluded that management input should be intensified in head block A to ensure better water deliveries to the scheme

Assessment of pollution impacts on the ecological integrity of the Kisian and Kisat rivers in Lake Victoria drainage basin, Kenya

Macro-invertebrate assemblages were used as bioindicators to assess the ecological integrity of Rivers Kisat (influenced by urban development) and Kisian (influenced by agriculture) using community attributes and the Index of Biotic Integrity. Six stations, three per river, were selected to correspond to different impact types and intensities along the rivers. Physico-chemical parameters and nutrients were determined for each station on a monthly basis from November 2007 to April 2008. Two-way analysis of variance was used to compare water quality and nutrient parameters, and macro invertebrate community attributes between the two rivers, with the river and station as the main factors. Significant differences were accepted at 95% confidence level. There were inconsistencies in the variation of physico-chemical parameters along the two rivers. However, River Kisat recorded higher values for all physico-chemical parameters considered, except pH and DO. Different indices and metrics representing the structural and functional organization of macro invertebrates were computed and evaluated for responsiveness to physico-chemical parameters and nutrient levels. Macro invertebrate diversity, richness and evenness values failed to delineate stations according to the different levels of degradation they were experiencing. However, the differences were captured by the index of biotic integrity, which separated stations into different classes of quality. River Kisat stations in urban areas scored lowest index values, less than 15 out of 25, while two river Kisian stations scored the highest value, more than 19. The index provided evidence of response to changes in ecosystem integrity exhibited by resident macro invertebrate assemblages to pollution arising from both point and nonpoint sources.Key words: Urban rivers, water quality, physico-chemical parameters, macro invertebrates

Phytoplankton community structure and environment in the Kenyan waters of Lake Victoria

1. Phytoplankton species composition, numerical abundance, spatial distribution and total biomass measured as chlorophyll a concentration were studied in relation to environmental factors in September 1994 (dry season) and March 1995 (rainy season), respectively, in the Kenyan waters of Lake Victoria; 103 species were recorded. 2. Blue-green algae (Cyanophyceae) were most diverse, followed by diatoms (Bacillariophyceae), green algae (Chlorophyceae) and dinoflagellates (Dinophyceae). 3. Twinspan separated the phytoplankton communities in the Nyanza Gulf and those in the open lake during both seasons. During the dry season, the Nyanza Gulf was strongly dominated by blue-greens, while diatoms dominated in the open lake. During the rainy season, blue-greens remained dominant in the Nyanza Gulf although the number of species found was lower than during the dry season; in the open lake, blue-greens replaced diatoms as the dominant group and there were more species than in the dry season. 4. Canonical correspondence analysis indicated that the phytoplankton species distribution was significantly correlated with turbidity during the dry season and with SiO2 during the rainy season. Chlorophyll a concentrations ranging from 2.0 to 71.5 mg m-3 in the dry season and 2.0-17.2 mg m-3 in the rainy season confirm earlier reports of increasing phytoplankton biomass in Lake Victoria since the 1960s

Factors associated with risky sexual behavior among HIV negative partners in HIV discordant relationships in Nairobi, Kenya

Introduction: Whereas risky sexual behavior influences HIV acquisition, little information is available on risk taking practices among negative partners in HIV discordant relationships in our settings. This study sought to determine the associated factors among this population in Nairobi.Methods: This study was a cross-sectional descriptive study and 133 HIV negative partners participated in the study.Results: Out of the 133 participants, 66.9% were male and 33.1% were female. Overall, 44.4% of the study participants reported inconsistent condom use, 14.3% reported having another sexual partner and 30% reported ever engaging in sexual activities under the influence of alcohol. Monthly earnings (p- 0.02), alcohol use (p- 0.03) and the index partner being on anti-retroviral medication (p-0.02) were significantly associated with having another sexual partner. Focus group discussion findings showed that male gender, alcohol use and the duration of the relationship influenced the decision to use condoms while male gender influenced having another sexual partner.Conclusion: Risky sexual behavior practices still occur among the HIV negative partners in discordant relationships. More education and sensitization should be made on the risks associated with this behavior so as to reduce the risk of HIV infection from their infected partners.Afr J Health Sci. 2013; 26:324-33

Developing Bt maize for resource-poor farmers – Recent advances in the IRMA project

This paper presents an overview of the advances in the IRMA project, which develops insect resistant maize varieties for resource-poor farmers, using both conventional breeding and genetic engineering. The project started in 1999 and is active in product development, impact assessment, andcommunication, all within the Kenya regulatory framework. So far, four application for introduction of tissue or commencement of field research were made to and approved by the National Biosafety Committee (NBC), and Bt maize leaves or seeds genes imported for testing against different stem borer species in bioassays on cut leaves in a biosafety laboratory, in potted plants in a Biosafety Greenhouse, and as whole plants in confined field trials in the Open Quarantine Station (OQS) at KARI Kiboko. All these biosafety facilities were specially built by the project for these evaluations. So far, good control has been realized against four of the five major stem borer species: Chilo partellus, Chilo orichalcociliellus, Eldana saccharina and Sesamia calamistis. Economic  impact assessment demonstrated that stem borers are major constraints and cause substantial losses. Resistant maizevarieties are likely to be adopted and to provide major returns to the investment if resistance against the economically most important species, Busseola fusca, can be found. Otherwise, returns would still be positive but small. Environmental impact research indicate that build-up of resistance against the Bt genes has not developed after that sufficient natural refugia exist in most areas, but suitable strategies acceptable to farmers need to be developed for some. Surveys, stakeholders meetings and other communications indicate that farmers, consumers and other stakeholders are cautiously optimistic about technology. Frequent interaction with the stakeholders and regulatory agencies assures a participative decision-making process and compliance with the strictest scientific and regulatorystandards

Phenotypic and Physiological Aspects Related to Drought Tolerance in Sorghum

Drought is one of the major limitations to crop productivity worldwide. Identifying suitable screening tools and quantifiable traits would facilitate the crop improvement process for drought tolerance in sorghum. This study evaluated phenotypic characteristics and physiological parameters determine which cultivars are more drought tolerant. Signs of drought intolerance in sorghum include leaf rolling, death of lower leaves, stunted growth and low yields. Experiments were conducted using 8 and 25 sorghum accessions planted at two sites in Kenya, namely; Biotechnology Centre and Kiboko Research site, respectively, for evaluation and seeds maintenance. Based on phenotypic characteristic of the 25 cultivars evaluated, the best drought tolerant cultivars were, IS.13615, KAK1950, KBM078, E-36.1, B-35, KBM-003 and IE SV 92036. These observations were specifically deduced from their performance, root characteristics, tillering ability and leaf parameters as drought tolerance indicators. B 35 and E-36 ranked the highest relative water content in leaves, hence more drought tolerant.La s\ue9cheresse est l'une des contraintes majeures \ue0 la productivit\ue9 des cultures dans le monde. L'identification des outils d'\ue9tude et des caract\ue8res quantifiables pourrait faciliter le processus d'am\ue9lioration de la culture de sorgho pour la tol\ue9rance \ue0 la s\ue9cheresse. Cette \ue9tude avait pour but l'\ue9valuation des caract\ue9ristiques ph\ue9notypiques et des param\ue8tres physiologiques pour d\ue9terminer les cultivars les plus tol\ue9rants \ue0 la s\ue9cheresse. Les signes de l'intol\ue9rance \ue0 la s\ue9cheresse englobent l'enroulement de la feuille, la mort des feuilles les plus basses, croissance rabougrie et r\ue9duction de rendement. Les essais \ue9taient conduits en utilisant 8 et 25 accessions de sorgho plant\ue9es dans deux sites au Kenya, \ue0 savoir le centre de Biotechnologie et le site de recherche de kiboko, respectivement, pour l'\ue9valuation et la maintenance des semences. Bas\ue9 sur les caract\ue9ristiques ph\ue9notypiques de 25 cultivars \ue9valu\ue9s, les meilleurs cultivars en terme de tol\ue9rance \ue0 la s\ue9cheresse \ue9taient: IS.13615, KAK1950, KBM078, E-36.1, B-35, KBM-003 et IE SV 92036. Ces observations \ue9taient sp\ue9cifiquement d\ue9duites de leur performance, caract\ue9ristiques des raciness, la capacit\ue9 de tallage et les param\ue8tres des feuilles comme indicateurs de tol\ue9rance \ue0 la s\ue9cheresse. B 35 et E-36 avaient une teneur relative plus \ue9lev\ue9e en eau et par cons\ue9quent les plus tol\ue9rants \ue0 la s\ue9cheresse

Mapping sweet potato in Eastern Africa

Simon T. Gichuki and Robert J. Hijmans report on a project that is collecting germplasm samples and local knowledge of sweet potato varieties in Eastern Africa with the help of DIVA-GIS, a free geographic information system (GIS)