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 the demographic factors with inferences on fisheries status of five dominant fish species, which were sampled monthly intervals for 18 months. 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 -0.95 year for Marcusenius senegalensis to -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 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.

Keywords

• growth parameters, exploitation rate, length at first capture, management, recruitment.