Linking environmental drivers including illegal gold mining to fish assemblage structure and health in a north-central Nigeria River: conservation and management implications of fish biodiversity

Anthropogenic activities exert significant pressures on the dynamics and health of dominant fish species in aquatic ecosystems. In this study, we evaluated how human activities impact the community structure, length–weight relationships, and condition factors of key fish species in a north-central Nigeria river. Sampling was conducted over 14 months across four sites with varying levels of disturbance: Zhabyala (minimal), Tunga Waya, Chanchaga, and Korokpan (severe). A total of 1361 fish individuals, representing diverse orders and families, were collected. Dominant species such as Tilapia zillii and Tilapia guineensis featured prominently in our analysis. Site 1 exhibited the highest abundance (n = 594), while site 4 had the lowest (n = 238). Characiformes dominated the assemblage, followed by Cypriniformes and Mormyriformes. Correlation analysis highlighted strong associations between environmental factors and the length–weight relationships of dominant species. Tilapia zillii showed the highest mean standard length and body weight at site 1, whereas Tilapia guineensis demonstrated the highest standard length at site 1 and the greatest body weight at site 3. Despite favorable health indicators for many dominant species, environmental stress was evident at specific sites. This study provides crucial insights into the condition factors and ecological dynamics of dominant fish species, serving as a valuable reference for future conservation and management efforts.