Ecological and Demographic Characteristics of Synodontis koensis, an Endemic Species of the Sassandra River Basin (Côte d’Ivoire)

This study investigated the ecological and demographic characteristics of Synodontis koensis (Pellegrin, 1934), an endemic species of the Sassandra River Basin (Côte d’Ivoire), in order to provide baseline data for its conservation and sustainable habitat management. Sampling was conducted from November 2024 to March 2025 at five stations along the N’Zo River, a major tributary of the Sassandra. Physico-chemical parameters of the water (temperature, pH, conductivity, total dissolved solids, and depth) were measured in situ, and a total of 329 individuals were collected for morphometric and weight analyses. Results revealed favorable environmental conditions for aquatic life, with water temperature ranging from 27.3 to 29.5 °C, slightly alkaline pH (7.65–7.95), and low conductivity (51–68 µS/cm). Standard lengths of fish ranged from 35 to 110 mm (mean = 77.48 ± 13.63 mm) and body weights from 2 to 31 g (mean = 11.71 ± 5.73 g), indicating a unimodal size structure dominated by medium-sized classes (60–90 mm). The length–weight relationship followed the model P=aLbP, with b=1.93b = 1.93b=1.93, showing a negative allometric growth pattern (b < 3), meaning that body length increases faster than weight. The condition factor (K) ranged from 1.10 to 9.26 (mean = 2.59 ± 1.57), suggesting good overall physiological condition. These findings indicate that S. koensis inhabits an environment that remains favorable but is increasingly affected by anthropogenic pressures. The study provides essential baseline information to guide conservation strategies and sustainable management of endemic fish populations within the Sassandra Basin.