Effect of fish farming on the water quality of rivers in northeast Spain

摘要

The effects of fish farming activities on the aquatic environment were evaluated by studyingnthe water quality of twelve rivers located in northeast Spain. Two sampling sites were usednfor each river: the first sampling point was located just upstream from the fish farmingnfacilities and the second one was downstream from fish farm effluent discharge point.nIn order to avoid any misinterpretation due to watershed location and seasonality, a stratifiednstatistical analysis was performed. The results show significant decreases in pH and dissolvednoxygen, in contrast to chemical oxygen demand, ammonia, phosphates and microbiologicalnparameters, which significantly increased downstream from the fish farm discharges.nOther significant variations were also found for conductivity and temperature. According tonthe European and local regulations concerning to support fish populations, our results fellnwithin the allowable limits for salmonid waters. Nevertheless, we suggest that furtherninvestigations should be carried out to study the ecological interactions between farmednand wild fish populations.