Population parameters of main fish species of Lake Nokoué (West Africa).

Abstract

Population parameters of main fish species from Lake Nokou é were investigated using length-freq uency samples from artisanal fisheries and then analysed using FiSAT Software. The values of K and L"" obtained in this study ranged from L., = 36cm and K= O.7 year·1 for Chrysischthys niwodigitatus (Lacépède, 1803) to L,. = 11cm and K= 2 yea r·1 for Pellonula leonensis Boulcngcr, 1916. Growth perform ance indexes (<l>') obtained were quite comparable to their respeclive mean values from previous studies available in FishBase. The high values of natura) mortality (M) and total mortality (Z) were recorded for fishes of smali sizes as Pellonula leonensis (M = 3.7 yea r·1 Z = 5.6 year- 1 Gerres melanopterus Bleeker, 1863) = 2.8 year·1 Z = 3.6 year- 1 and Gobionellus occid entalis (Boulenger, 1909) (M = 2.7 year·1 Z = 2.2 year- 1 . The estimated lon gevity (tmaJ ranged between 1.5 years for P. leonensis and 4.3 years for C. nigrod igitatus and Cithar ichthys stampjlii (Steindachn er, 1896), indicating thar most species are shorr-lived. The exploitation rates (E = F/Z) record ed were below 0.5, wh ich is the optimal exploitation rate. The reasonable exploitation rate recorded for Lake Nokoué might be explained by the use of acadjas (branches fixed in water to attract fishes).