Population Dynamics and Biological Characteristics of Marcusenius senegalensis in Esa-Odo Reservoir, Southwestern Nigeria

Understanding the biological characteristics and exploitation status of freshwater fishes is essential for sustainable fisheries management. This study investigated the growth, feeding ecology, reproductive characteristics and stock status of Marcusenius senegalensis in Esa-Odo Reservoir, Southwestern Nigeria, from October 2017 to November 2019. Analyses included the length–weight relationship, gut repletion, gastrosomatic index, diet composition, gonadosomatic index, fecundity, egg diameter, gonadal development and length-based stock assessment. The length–weight relationship showed positive allometric growth (b = 3.303). Diatoms dominated the diet (20.32%), while the gastrosomatic index averaged 1.25 ± 0.33 in males and 1.03 ± 0.19 in females. Fecundity ranged from 145 to 4,212 eggs, with an overall mean of 1,160.82 ± 775.57 eggs, and fully ripe gonads predominated in both sexes. Length-based assessment estimated L∞ = 33.61 cm, K = 0.111 yr⁻¹, Z = 1.232 yr⁻¹, M = 0.395 yr⁻¹ and F = 0.837 yr⁻¹. The exploitation rate (E = 0.679) exceeded E₀.₅ (0.400), indicating substantial fishing pressure. In conclusion, M. senegalensis is an ecologically flexible and actively reproducing species, but the elevated exploitation rate highlights the need for effective management through fishing-effort monitoring, protection of mature stocks and appropriate size-at-capture regulations to support long-term sustainability.