Browsing by Author "Walakira, John K."

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    Growth and Survival of Ripon Barbel (Barbus Altianalis) Larvae and Juveniles Fed Five Experimental Diets in Captivity
    (Aquaculture Reports, 2020) Aruho, Cassius; Walakira, John K.; Owori-Wadunde, Akisoferi; Nuwamanya, Ephraim; Bugenyi, Fred; Sserwadda, Martin; Rutaisire, Justus; Borski, Russell J.
    Mass production of quality seed is vital for commercial culture and requires prior knowledge of appropriate larval diets and their utilization. Four experiments were sequentially conducted at different periods to evaluate the effect of live and a processed microdiet on growth and survival of Barbus altianalis larvae and juveniles. Larvae were fed exclusively on live prey (Moina and Artemia nauplii), microdiet (57 % Crude Protein), decapsulated Artemia cysts and in combination (Moina + microdiet). The effect on growth was further evaluated in subsequent juvenile trial by co-feeding. Green water effect on larval growth was also evaluated. In the final experiment, 15 day old larvae were raised in fertilized outdoor concrete tanks. Results indicated that each diet affected larval growth significantly different (P < 0.05) with the combination diet (152.05 ± 2.51mg) and decapsulated Artemia (141.14 ± 2.43 mg) performing better than microdiet, Moina and Artemia nauplii in that order. In subsequent juvenile experiment, larvae originally fed decapsulated Artemia (510.13 ± 11.93 mg) and those fed a mixed diet (500.20 ± 11.8 mg) performed better than other diets. Ontogenetic pattern of amylase, lipase and protease activity identified larvae maturation age at 14–21 Days after hatching (DAH) (14.93 ± 0.36–31.5 ± 0.61 mg) with the combination diet. When larvae at 15 DAH were nursed in outdoor tanks, final survival and growth performance increased to 95.3 % and 1112 ± 42.70 mg compared to the indoor nursing at 90.9 % and 355.33 ± 6.44 mg respectively by 75 DAH. Therefore we recommend that any microdiet manipulations and or outdoor nursing be done during or after this period. Microalgae had no direct effect on larval growth (P > 0.05). In this study, larvae were confirmed to utilize the microdiet from exogenous stage but co-feeding produced best average weight (152.05 ± 2.51mg), specific growth rates (4.06 ± 0.19) and survival (90.9 %). This study provided guiding strategies for improved rearing of B. altianalis fingerlings in captivity.
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    Increasing Farmers’ Access to Aquaculture Extension Services: Lessons from Central and Northern Uganda
    (Uganda Journal of Agricultural Sciences, 2020) Atukunda, Gertrude; Atekyereza, Peter; Walakira, John K.; State, Andrew E.
    This paper focuses on examining the modalities of extension service provision, and determining feasible approaches for increasing accessibility among fish farmers in Uganda. The paper draws on a cross-sectional study involving fish farming households and extension workers to determine access to extension services for improved farming practices. Quantitative data were collected from 246 households using a semi-structured questionnaire. Qualitative data were generated from Key Informant interviews with selected extension workers, officials in charge of extension planning District Fisheries Officers and Fish Farmer Group leaders. Focus Group Discussions were also conducted with fish farmers. The results indicated a significant association between socioeconomic characteristics of fish farmers and access to extension services. Size of land owned, income from pond fish and membership to fish-farmer groups were the significant factors (P<0.05). All the respondents reported pressing needs which required extension intervention. The respondents expressed the need to form effective farmer groups for the purpose of sharing knowledge, arriving at mutual agreement on scheduling extension activities and providing feedback to the extension workers. Specifically for the northern region, there is a need for the Fisheries Extension Officer to identify and respond to the extension needs of fish farmers through various means including ICTs. Identifying solutions to social, technical and institutional constraints in extension can increase access to services through constructive social interactions between farmers and extension agents. The article provides important lessons for practice and policy, and proposes a farmer-centred model, capable of facilitating increased access to aquaculture extension services in Uganda.
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    Morphology and Functional Ontogeny of the Digestive Tract of Barbus Altianalis Larvae
    (African Zoology, 2019) Aruho, Cassius; Walakira, John K.; Bugenyi, Fred; Rutaisire, Justus; Reading, Benjamin J.
    The ontogenetic development of digestive structures in Ripon barbel (Barbus altianalis) larvae was investigated using standard histological and histochemical procedures from hatching up to 60 days after hatching (DAH). The study was conducted to determine the best period of exogenous feeding and the stage when the digestive tract is able to digest processed microdiets. Results indicated that at hatching, the digestive tract, mouth and anus were closed. The opening of the mouth and anus were observed 3–4 DAH, whereas complete separation of the entire gut was observed on 5 DAH. Exogenous feeding started 5–6 DAH, but complete yolk exhaustion occurred 7–8 DAH, indicating a period of mixed feeding. Mucosal epithelial folds were first noted 3 DAH in the anterior intestine and became profound with some goblet cells (mucous cells) by 6 DAH. At 7 DAH the mucous cells had started secreting both neutral and acid glycoconjugates. The first intestinal single loop occurred at 28–30 DAH and a double loop at 45–50 DAH. Each coiling was proceeded by larval weight increase. By 7 DAH the buccopharyngeal cavity was lined by a layer of squamous epithelial cells with scattered goblet cells and tastebuds that became numerous by 15 DAH. At hatching, the liver and the pancreas were undifferentiated, but on 3 DAH the hepatocytes and zymogen granules of the pancreas became clear. By 7 DAH both organs enlarged, making extensions into the posterior. Intestines coiling at 28–30 DAH coincided with the beginning of external dressing of the scales, a period when B. altianalis started transforming into a juvenile. By 7–8 DAH the digestive structure showed all the necessary digestive features that could enable the larvae to digest any compound diet suggesting that it may be feasible to substitute or offer a complete microdiet during larvae nursing with reduced larval mortality.