Growth and exploitation parameters of Ilisha africana, by-catch of the experimental fishing for the study on selectivity of gill nets for Ethmalosa fimbriata, in the Saloum estuary and Joal (Senegal)

Growth and exploitation parameters Ilisha africana were determined from the size frequency for the first time in Senegal. The size distribution showed average sizes equal to 19.26 ± 1.70 and 19.75 ± 2.03 cm, respectively in the estuary and at the sea. The values of allometric rates of the length-weight relationship were, respectively equal to 2.88 and 2.93 in the estuary and at the sea indicating a negative allometric growth for this species. Von Bertalanffy growth parameters are estimated to L∞ = 24.7 cm, K = 0.33 year-1, t0 = -0.53 in the estuary and L∞ = 25.5 cm, K = 0.34 year-1, t0 = -0.51 at the sea with growth performance index, respectively equal to Φ' = 2.30 and Φ' = 2.34. The values calculated for the total mortality (Z), natural mortality (M) and the fishing mortality (F) were: Z = 1.08, M = 0.93, and F = 0.14 year-1 in the estuary while at the sea these mortality rates were estimated respectively at Z = 1.25, M = 0.91, and F = 0.33 year-1. The current exploitation rates in the estuary (0.10) and at the sea (0.25) indicated that I. africana was under-exploited in Senegal.   Key words: Allometric, mortality, Von Bertalanffy, condition factor.