Growth and bioaccumulation of trace elements in economically important fish from contrastingly impacted impoundments

Environmental conditions and species-specific adaptations influence fish growth and trace element bioaccumulation. The present study focused on three economically important fish species, Cyprinus carpio, Clarias gariepinus and Oreochromis mossambicus caught from Olifantsnek and Bospoort Dams in South Africa (2017-2020). Using otolith-derived growth rates and trace element analyses in fish muscle tissue, site-specific ecological dynamics were identified. Contrasting growth patterns and growth rates were observed between the two sites. These differences are attributed to variation in nutrient levels, and the carrying capacity of each site, as well as the metabolic processes of each species. The older fish of Bospoort Dam showed a decrease in trace element concentrations in their muscle tissue, while Olifantsnek Dam demonstrated an increased level of bioaccumulation over time. Furthermore, platinum levels were significantly higher in Bospoort Dam, indicating localized pollution. Species-environmental divergence was also observed with C. carpio and C. gariepinus segregating between impoundments, while O. mossambicus showed generalist tendencies. The present study highlights how growth and element bioaccumulation are influenced in the environmental context. The faster growth and trace element dynamics of fish from Bospoort Dam reflect a highly productive system influenced by anthropogenic factors, while the slower growth and bioaccumulation in fish from Olifantsnek Dam suggest stable, resource-limited conditions. These findings underscore the necessity of tailored management strategies that consider site-specific ecological conditions and pollution levels rather than generalized conservation efforts. Thus, customized approaches are essential for balancing fishery productivity and ecosystem health under varying environmental pressures.