Semi-natural fishway efficiency for goliath catfish (Brachyplatystoma spp.) in a large dam in the Amazon Basin

The recent large-scale hydropower development in the Amazon basin has raised concerns about the impacts on the movements of migratory fishes such as goliath catfish (Brachyplatystoma spp.). In the Madeira River, the efficiency of a 1400-m long fishway in the Santo Antonio hydropower plant (SAE HPP) was evaluated between 2012 and 2016 using telemetry techniques. Tagged fish (N = 388) were released 2000 m downstream of the dam and near the entrance or inside the fishway (N = 149). Fixed radio stations monitored fish movements and residence near 14 different structures of the SAE HPP; four acoustic receivers in the reservoir and one downstream the dam monitored whether fish moved away or past the dam. The findings revealed that 15% of the fish released downstream were detected near the dam but none were detected in the reservoir upstream. For the group of fish released in the fishway, no B. rousseauxii (N = 64) was detected moving upstream and into the reservoir and 5 individuals of B. vaillantii (N = 41) exited the fishway to the reservoir. This was the first long-term telemetry monitoring of fish movements near a dam in the Amazon and the results provided evidence of inefficiency of the fishway for the target species, which led the hydropower company to reconstruct the fishway.

Automated summary

The recent large-scale hydropower development in the Amazon basin has raised concerns about the movements of migratory fishes such as goliath catfish. In the Madeira River, the efficiency of a fishway in the Santo Antonio hydropower plant was evaluated using telemetry techniques. The study revealed the inefficiency of the fishway for the target species and led to its reconstruction.