Evaluation Of Internal and External Injuries Caused By Barotrauma In Brazilian Fishes After Passage Through Hydropower Turbines

Hydropower development in Brazil is a real threat for the aquatic fauna. The country already has around 956 hydropower plants constructed, which corresponds to 87% of the electrical energy generation. Moreover, the government decennial plan (2011-2020) projects an increase of 38% in hydropower generation, throughout the development of large projects in river basins as the Amazon. Hydropower plants can cause several environmental impacts and mortality of fish in turbines is one of them. Fish kills have been registered in Brazil after the passage through hydropower turbines or caused by the entrance into the draft tubes during turbine maintenance. Barotrauma injuries are caused due to pressure changes experienced by the fish during the passage through the turbines. External (exophthalmia, everted stomach and intestine and bubble formation in the fin rays) and internal (hemorrhages, swim bladder rupture and embolism, etc.) injuries resultant of barotrauma can lead to direct or indirect mortality of fish. Thus, gathering information about the extension of barotrauma injuries in fish after passage through turbines can help the development of different scenarios where mortality is more likely to occur. Fish with barotrauma symptoms were collected below two different dams and the types of injuries were analyzed and quantified. Fish were separated by orders, basically Characiforms and Siluriforms. Internal and external injuries were different among orders. For Characiform fish swim bladder rupture was the most observed injury. For Siluriforms, exophthalmia and stomach eversion were the most frequent injury observed. The results also showed that the morphology of the swim bladder among these different groups seems to play an important role in the type of injury observed. It is clear that this is an important impact to be evaluated for the fish fauna in Brazil and more research is needed to gather more detailed information.