Temporal and spatial variability of fish assemblages in a river basin with an environmental degradation gradient

Abstract

We analyzed long-term data related to temporal and spatial variation in fish assemblages from five sites along the Suquia River Basin (Cordoba, Argentina). We aimed at determining whether water quality variations generate changes in fish assemblage structure and composition along the river. Despite deterioration of water quality recorded along the basin, fish assemblages were characterized as qualitatively persistent and quantitatively stable, indicating that the specific composition were relatively constant over time. However, on a temporal scale, fish assemblages from the most polluted areas responded to the water quality degradation with a greater variation of species abundance than those from pristine sites. On a spatial scale, changes in fish assemblage structure were related with watershed disturbance gradient and indicated a strong association between fish species distribution and water quality variation. The alterations found in our study suggest a potential imbalance of fish assemblage structure in the long term.