Spatial and temporal limnological changes of an aquaculture area in a neotropical reservoir

This study evaluated the spatial and temporal limnological characteristics of an aquaculture area in the Itaipu reservoir, Brazil. During a one-year period, water quality parameters were evaluated in seven collection sites using a fish culture system as the reference point. A regression analysis was performed on water transparency versus chlorophyll a and total phosphorus versus chlorophyll a. The trophic state index (TSI) was calculated using data from water transparency, chlorophyll a, and total phosphorus. In addition, a study of the carrying capacity was conducted in situations of high and low flow and rainfall based on 725 m3 s−1 and 298 mm and 34.5 m3 s−1 and 11 mm, respectively. No difference was observed in the parameters of water quality and the TSI in relation to the collection sites; these parameters only varied significantly throughout the seasons. The regression analysis showed that increased total phosphorus in the environment leads to increase in chlorophyll a concentrations and consequently decreased water transparency. Evaluation of the carrying capacity demonstrated that under conditions of high precipitation and flow it is possible to produce 623.7 tons of fish per year, which is above the total cultivated in fish farms at the study site.The seasonal variations influence water quality parameters on neotropical reservoir. The biochemical oxygen demand is controlled by the interaction between the layers of water and the seasons of the year. The fish farm in these places, when kept within the capacity of supporting of the environment, does not alter the quality of water