Analysis of Environmental Factors and Fish Population Structure in the Middle Course of the Comoe River, Côte d’Ivoire

Abstract

Human population growth and activities associated with the Anthropocene increasingly impact aquatic environments through agriculture, mining, and fishing. In the Comoé River, these pressures lead to pollution, overfishing, and ecological decline, affecting water quality and aquatic life. This study aims to analyze the influence of physico-chemical parameters and anthropogenic pressures on the distribution of fish in the middle course of the Comoé River. Sampling was conducted from March 2021 to March 2022 at five stations (M’basso, Manzan, Yêrê-yêrê, Abradinou, and Bettié), using a seasonal approach. Physicochemical parameters (temperature, pH, dissolved oxygen, conductivity) were measured in situ using a multiparameter analyzer, while turbidity was determined in the laboratory. Fish were captured using gillnets, traps, and lines. A total of 38 species belonging to 8 orders and 14 families were recorded, with Siluriformes being the most prevalent (35.71%). Chrysichthys nigrodigitatus, Schilbe mandibularis, and Synodontis bastiani were the most abundant species. The Bettié station exhibits the highest species richness and abundance, but low evenness, reflecting an unbalanced community structure. Statistical analyses show significant differences in dissolved oxygen, conductivity, and turbidity between stations (p < 0.05). Principal component analysis highlights a strong influence of human activities, particularly at the Manzan station. Length-mass relationships indicate variations in growth strategies across stations (positive, negative, and isometric allometry). Overall, fish distribution is strongly influenced by physicochemical characteristics and human pressures. These results underscore the impact of human activities on the structure of fish populations and the need for sustainable management of the Comoé River.