Abstract

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.