Demographic parameters and exploitation rate of five key fishes of Okpara Stream, Oueme River, Benin, West Africa

Abstract

The current study was carried out on Okpara Stream in Northern Benin to evaluate these demographic factors with inferences on fisheries status. Five dominant fishes were sampled monthly intervals for eighteen (18) months and growth parameters were generated by FiSAT II Software. Asymptotic length (L∞) ranged from 36.23 cm (Brycinus macrolepidotus) to 18.8 cm (Hemichromis fasciatus). Growth rates (K) varied between 1.6 yr-1 and 0.66 yr-1 with growth performance index (Φ’) ranging from 2.4 to 3.1. Theoretical age at length zero (t0) varied between -0.95 year for Marcusenius senegalensis t0 -0.59 year for Shilbe intermedius. Except for B. macolepidotus, total mortalities were higher than 2 year-1 and length at first capture (L50) ranged between 7.72-12.09 cm. Marcusenius senegalensis and S. intermedius showed one annual peak of recruitment whereas H. fasciatus, Oreochromis niloticus and B. macrolepidotus displayed two peaks. The results indicated that the stocks of these five species were underexploited. However, the low length at first capture (L50) recorded for some species, requires the implementation of early fisheries management scheme to assure a sustainable exploitation of these fishes.