The first data on the population parameters of the main fish species in man-made Lake Buyo (River Sassandra, Côte d'Ivoire)

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The growth parameters and the exploitation rate of the main 9 fish species found in the lake of the Buyo dam was studied from July 2017 to June 2018. The monthly frequency data for lengths obtained from experimental and commercial fisheries were analysed using the FiSAT II software and its sub-program ELEFAN for the evaluation of population parameters. The asymptotic length (L∞) varies from 63.33 cm for Chrysichthys nigrodigitatus to 15 cm for Synodontis koensis. The specific growth rate (K) is higher (0.9 year-1) in Malapterurus electricus and lower (0.21 year-1) in the species Schilbe mandibularis, while the growth performance index (φ') calculated from 3.48 in Chrysichthys nigrodigitatus to 2.04 in Tilapia zillii. The fishing mortality (F) and exploitation rate (E) calculated are below the optimal exploitation rate for most species. The recruitment pattern is a continuous model with a single peak and reveals a recruitment period in the months of May, June, August and October. According to the exploitation predictions, the species O. niloticus, M. electricus, C. nigrodigitatus, D. rostratus and L. niloticus have an exploitation rate E respectively 0.35; 0.46; 0.27; 0.41 and 0.31 higher than the optimum exploitation rates Eop (respectively 0.29; 0.33; 0.37; 0.28 and 0.27), which would mean that the stock of these species in the fishery is already reduced to more than 50% of its untapped biomass; therefore overexploited. Our study provides the first data on the population parameters of the main fish species from the Lake Buyo. These data could contribute to establish a sustainable management plan for fisheries resources only in lake Buyo.

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