Department of Aquaculture and Fisheries Management

Permanent URI for this collectionhttps://dspace.njala.edu.sl/handle/20.500.144402/158

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    Lengthz-Weight Relationship and Condition Factor of Coelotilapia joka (Thys van den Audenaerde, 1969) in the Rokel/Seli River, West Africa
    (SciPress Ltd., 2020) Konoyima, Komba Jossie
    This study was conducted in the lower, middle and upper reaches of the Rokel/Seli River, Northern Sierra Leone. There is a research gap on the growth or wellbeing of tilapia fish species in Sierra Leone. The objective of this study is to determine the length-weight relationship and condition factor of Coelotilapia joka from the main river channel. This research could contribute to promoting an agenda for fish culture practices for the fish. A total of 228 specimens of Coelotilapia joka were collected using gill nets. Fish length and weight measurements were done using fish measuring board and digital weighing balance respectively. Measurement for water quality was made using the Jemway multi-parameter water quality measuring device (Model: J970, Barloworld Scientific, United Kingdom). The values for regression coefficient “b” gave 2.5437, 2.1841 and 2.4585 for males, females and combined sex respectively, implying a negative allometric growth in the fish at (b 1). The difference in ‘K” for both sex is significant (p<0.05). A study for a period of one year could, however, provide a complete analysis of seasonal variations in growth and condition of the fish.
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    Overexploitation and urgent need for precautionary management of Bonga Shad ( Ethmalosa fimbriata ) in West African waters: A multi‐model Bayesian assessment
    (Wiley, 2026-07-30) Konoyima, Komba Jossie
    Ethmalosa fimbriata, a key small pelagic species underpinning food security and livelihoods along the West African coast, warrants a robust stock assessment due to concerns of overexploitation. This study synthesizes multi-fleet catch records (1970-2021) and unstandardized catch per unit effort (CPUE) data (1995-2017) from the Eastern Central Atlantic (ECAO) to evaluate the northern stock using four surplus production models: the catch-only (CMSY) and abundance-only (AMSY) maximum sustainable yield models, the Bayesian state-space model (BSM) and the Just Another Bayesian Biomass Assessment (JABBA) model implementing Schaefer, Fox and Pella-Tomlinson functions. The objective was to evaluate model predictive accuracy and stock status to provide evidence-based management advice. From the results, CMSY indicated 2021 biomass (B) was marginally above the sustainable limit (B/BMSY ≈ 1.03) with current fishing mortality (F) near FMSY, while AMSY and BSM both indicated ongoing depletion (B/BMSY ≈ 0.56-0.81) and overfishing (F/FMSY >1.0). JABBA's Schaefer model, demonstrating superior fit (root-mean-square error = 16.9%, Deviance Information Criterion = -382.7) over Fox and Pella-Tomlinson models, estimated 2021 biomass at 9% below BMSY and fishing mortality at 59% above FMSY. Fox and Pella-Tomlinson models yielded similar biomass trajectories but were less precautionary. Projections indicate that only Schaefer-based total allowable catches (TACs) below 100,000 t would stabilize biomass; higher quotas risk continued decline. Despite limitations including incomplete catch data and reliance on unstandardized indices, results underscore the urgency for precautionary catch limits, regional coordination and improved compliance to ensure sustainability. This study offers a transferable assessment framework for data-limited fisheries and supports evidence-based policy for the conservation of E. fimbriata and food-security resilience in West Africa.