Water Quality in a Reservoir used for Fish Farming in Cages in Winter and Summer Periods

Abstract

This study aimed to evaluate the vertical dynamics of the water quality, in different seasons (summer and winter), in an aquaculture area of the Iguassu River electric plant reservoir (Paraná/Brasil). Water sampling was done monthly. Samples were collected from the water column layers (epilimnion, metalimnion and hypolimnion.). Water temperature, (pH), dissolved oxygen, biochemical oxygen demand, nitrite, chlorophyll, total phosphorus, orthophosphate and ammonia were the parameters evaluated. Data from each parameter were submitted to ANOVA and to Tukey’s test at the 0.05 significance level. Correlation analysis between the variables was performed using the Spearman’s test. Multivariate approach was adopted performing Royston’s multivariate normality test. A clustering analysis was performed using Ward’s minimum variance method with a Euclidean distance matrix. This study showed that fish farming did not alter the water quality during summer and winter. Heterogeneity in summer and homogeneity in winter are observed between the layers of the water column.