Throughout the spawning season, which took place between November 2025 and February 2026, the Fish Transposition Systems (STP’s) were kept in operation at Aliança’s hydroelectric plants, demonstrating responsible action in relation to socio-environmental issues and ensuring that migratory species had free routes to reach areas suitable for reproduction.
This mechanism is critical for ecological connectivity, allowing fish to overcome the barriers imposed by dams and complete their reproductive cycle. In general, during the spawning season, the fish migrate upstream in search of areas suitable for reproduction, and the STP acts by allowing the continuity of the migration and ensuring the balance and continuity of the species in the basins where Aliança Energia operates.
Learn how the Fish Transposition System works in each of the units:
Risoleta Neves HPP | MG
The STP of the Risoleta Neves HPP is composed of different stages that prioritize the safety and well-being of the fish. Initially, a fish ladder utilizes the flow of water to attract individuals. Then, they are taken to an elevator, where they are suspended for monitoring. After that, the fish are placed in trucks with special tanks (transfish) and transported to the reservoir.
During this process, a screening is carried out in which information such as weight, size and species is collected, in addition to making markings that allow monitoring migratory behavior. After all these steps, the fish are returned to the environment, where they can follow their reproductive cycle. In the 2025/2026 cycle, this system recorded the movement of fish of 23 species, totaling 1,526.30 kg, demonstrating its importance for conservation.
Funil HPP | MG
The operation of the STP of the Funil HPP is based on an elevator system that transports the fish mechanically. The fish are attracted by an artificial waterfall and enter the system, where they are directed by railings to a bucket. This bucket is then hoisted by an elevator to an upper chute, where the fish are monitored and released into the reservoir, allowing them to continue their migration to important areas such as rivers, lagoons, and floodplains.
This system has been in operation since 2004 and has already enabled the transposition of more than 350 thousand kilos of fish. When the natural water level is not ideal for the entry of fish, the transposition is done manually with the use of special boxes (transfish), ensuring the continuity of the migration process. In 2025, the system underwent modernizations that increased its safety, and the 2025/2026 cycle was completed without environmental incidents. In the 2025/2026 spawning season, more than 5700kg of fish were transposed, exceeding 6000 fish marked for monitoring.
Aimorés HPP
The Aimorés HPP has a ladder-type STP, which works more naturally and continuously. In this system, the fish rise spontaneously, as the structure mimics the flow of the river, eliminating the use of mechanical transport. Since 2006, this model has been monitored, registering more than 53 thousand fish of 66 species, which demonstrates its effectiveness and diversity of use.
In the 2025/2026 spawning period, more than 2 thousand individuals of 15 species were recorded. Monitoring is carried out through cast net captures, visual observation and lowering of the system to ensure complete fish counting. While in the spawning season the monitoring is more intense, outside this period it occurs quarterly.
Aliança Energia believes that the continuous monitoring and improvements implemented reflect the engagement with sustainable practices and the preservation of aquatic ecosystems, ensuring the migration of fish, the reproduction of species and the maintenance of the biodiversity of the rivers.
