Ichthyofauna Diversity and Morphometric Analysis in an Anthropogenically Stressed Water Body Downstream of Jebba Dam, Nigeria

Fishery resources are on the decline due to incessant and unregulated fishery activities practiced in most parts of the globe. This study investigated the fish composition of an anthropogenically stressed water body in Nigeria (Downstream Jebba Dam). Samples were collected using standard methods and procedures. A total of 6,850 fish belonging to 17 families and 25 species were collected from the sampled stations. Fish composition shows the Mochokidae family with the most dominant species at 29.33% and represented Synodontis batensoda, which was well distributed in all the study stations but highest in the station with 934 individuals, while the Gymnarchidae family was the least recorded with 0.16% and represented Gymnarchus niloticus. Length-Weight relationship (LWR) value ranged between 0.0018 and 0.215 (b <3) for the dominant fish species, indicating negative allometric growth as the fish species grows in length faster when compared to the weight. In terms of mean condition factor (K of the dominant fish species of Downstream Jebba Dam, Cynothrissa mento had the highest with 10.09, followed by Oreochromis niloticus (9.82), Mugil cephalus (9.02), Labeo coubie (3.72), Bagrus bayad (0.90), Alestes macrolepidotus (0.52), Clarote laticeps (0.31), Momyrus rume (0.26), Clarias gariepinus (0.19) and Citharinus citharus (0.16). The high condition factor (>1) observed in some fish indicates that these fish species were physiologically stable and successful well, while those with less than (<1) mean value implied that it was physiologically unstable, as showed in some species. Overall, the medium abundance of fish species in this study is an indication of an impaired water system.