Water quality in Ponte Pensa Aquaculture Park, Solteira Island Reservoir, SP, Brazil, where fish are cultivated under great-volume cage system

This study analyzes spatial and temporal variations in physical and chemical water variables due to the influence of fish culture in a cage system (20x20x3 m) in Ponte Pensa Aquaculture Park (Solteira Island Reservoir), before and after cage installation. Water samples were collected on a monthly basis in the subsurface of three sampling sites (August/2011 to July/2013): downstream from the farming site (S1), at the farming site (S2), and upstream from the farming site (S3) (n = 72). Water temperature, pH, dissolved oxygen, transparency, turbidity, electrical conductivity, ammonium ion and total phosphorus were assessed. The principal component analysis (PCA) was applied to joint analysis data. PCA results explained the 61% joint variability in data of the first two components. Fish farming in cages caused significant temporal changes, mainly in January 2013, as well as sudden spatial changes in water physical and chemical variables. Fish culture influenced the quality of the water; such influence was mainly indicated by variations in ammonium ions and in total phosphorus concentrations, which were confirmed through PCA application. PCA results showed two distinct temporal phases: Phase 1 - prior to fish-cage farming, when limnological conditions were characterized by the highest dissolved oxygen concentrations and by high temperatures; Phase 2 - post-production period, when limnological conditions were characterized by the highest total phosphorus and ammonium ion concentrations.