Growth and population structure of Odaxothrissa mento and Brycinus leuciscus from the lower reaches of the White Volta in Ghana

The growth and population structure of two small pelagics: Odaxothrissa mento and Brycinus leuciscus were studied based on 1‐year data collected from the White Volta at Yapei in northern Ghana. The species were assessed using an R package TropFishR. The von Bertalanffy growth parameters were estimated with an asymptotic length (L∞) of 13.65 cm TL (CI95%: 11.29–17.29), growth curvature of .32/year (CI: .14–.63) for Odaxothrissa mento and L∞ of 8.85 cm TL (CI95%: 8.17–11.02) and growth curvature of 1.57/year (CI95%: .64–1.57) for Brycinus leuciscus. The computed total mortality (Z) was 2.25/year, the natural mortality (M) was .91/year and fishing mortality (F) was 1.34/year for Odaxothrissa mento while Z = 4.5/year, M = 2.8/year and F = 1.7/year were estimated for Brycinus leuciscus. Results indicate that the stock of Odaxothrissa mento is slightly overexploited with a current exploitation rate (E) of .60/year which is above the optimum exploitation rate (Eopt) of .5. However, the stock of Brycinus leuciscus was found to be underexploited with a current exploitation rate (E) of .38 year−1. The estimated age at 50% capture for Odaxothrissa mento and Brycinus leuciscus were 3.4 years and .65 years, respectively, with their corresponding lengths at 50% capture of 9.14 cm and 5.67 cm, which are close to the mean lengths of the population in the present study. Mean length at first sexual maturity (Lm) for Odaxothrissa mento is estimated as 5.2 and 4.2 cm TL for females and males while Lm of 3.5 cm and 4.5 cm were estimated for females and males of Brycinus leuciscus, respectively. The estimated longevity (tmax) of Odaxothrissa mento and Brycinus leuciscus was 9.7 years and 1.7 years, respectively, indicating that Odaxothrissa mento is a long‐lived species while Brycinus leuciscus is a short‐lived species. This conforms to the exploitation pattern of the species and thus requires species‐specific management interventions.