Machine downtime is an operational event with a potential impact on the aquatic environment. However, with the successful performance of the maneuvers, there is a significantly smaller number of fishes trapped. This reflects the low significance of this impact, since this is a factor resulting from the conjugation of several others such as severity/intensity (strong or weak), scope (whether local or regional), detection (if easy and fast action or not) and duration.

The event can be analyzed as of significantly low impact to the maintenance activity of the generating units, because the action has been taking place considering the intensity (quantity of fish captured) low, associated with the rapid detection that requires taking measures also of rapid loosening and, still, in a short duration, guaranteeing the highest survival rate of rescued and loose specimens.

The machine stop is preceded by a detailed planning and as a result a schedule of the activities to be performed, in which it is explicit the responsible for the action and its duration. During this stage all areas involved are called to participate in the meeting, including biologists and technicians of the Superintendence of Environmental Management, responsible for rescuing fish within the generating unit.

The intensity factor is controlled by the interruption of the water flow at the closest possible time of the placement activity of the downstream maintenance floodgates, which will prevent the entry of fish into the suction tube of the generating unit. The detection factor is controlled by planning, which predicts exactly the moment the team enters to do the rescue – and never exceeds the second day of stopping the generating unit.

A non-elaborate action could result in a significantly higher impact, which never occurred, allowing to report as of low significance according to the amount of rescued fish, a factor associated with severity/intensity.

Since 1987, 73,000 fish were rescued from the generating units by the teams of the Brazilian and Paraguayan Reservoir Division. In 2018, 475 fish of 46 species were removed from the generating units and released in their original environment, after 14 operations carried out to remove the fish trapped in the forced ducts, by-pass and the water outlet of the generating units during Maintenance stops.

Also, during the analyzed period, an agreement was signed with the Federal University of Paraná for the development of fish biodiversity monitoring tools using environmental DNA. Throughout the year, 25 tissue samples from 18 species were aggregated to the sample bank and will allow the development of the first stage of the work, which is the establishment of a reference DNA bank.