Fish stock assessment and potential yield of a reservoir in Benin City, Nigeria

Fish stock assessments of aquatic ecosystems are relevant against the backdrop of over exploitation, fish species extinction and the inadequate management of aquatic resources especially in developing countries such as Nigeria. The study specifically examined the fish stock assessment and the potential fish yield of the Ikpoba reservoir in Benin City, Nigeria. A total of 903 fishes were captured from the reservoir with individual abundance ranging from 18 (1.99 %) for Epiplatys sexfasciatus to 286 (31.67 %) for Synodontis clarias. A total of 15 fish species belonging to 8 families were identified while the dominant fish species were S. clarias, Hemichromis fasciatus and Marcusenius psittacus. A total of 11 fish species were identified as rare in this study. The Ekiuwa station of the reservoir was the richest species-wise (d= 6.45) while the Midpoint station had the greatest general diversity of fish species (H= 1.42). There was a more even spread and distribution of fish species at the Midpoint station (E= 1.00) while the commonest fish species were most frequent at the Okhoro station (C= 1.62). In this study, the Condition Factor ranged from 1.00 for M. psittacus to 5.78 for Gnathonemus abadii. The potential fish yield index of the reservoir was low due to a low nutrient content and ranged from 17.7 in the dry months to 23.13 in the wet months. It was advocated that the Ikpoba reservoir must be continuously monitored in order to ensure that fish species composition and diversity do not reach critical limits.