Analysis of the Effectiveness of Fish Skin Extracts as a Chemical Repellent of Ichthyofauna Applied to the Hydroelectric Sector

The Jirau Hydroelectric Power Plant (HPP), on the Madeira River, Rondônia, Brazil, represents 23% of the Amazon Basin and has high populations of fish. The reception of chemical signals is highly developed in fish, especially in those that inhabit environments with high turbidity, such as the Madeira River. Originally named by Frisch (1941) as “Schreckstoff,” the alarm substance is released after damage to the epidermal cells of fish previously exposed to a stressful situation. Several studies, dating back to the 1960s, state that the perception of this substance by other fish can result in alarm and repulsion reactions. This study aimed to analyze the feasibility of applying skin extracts as alarm substances in the draft tube of bulb-type generator units. In preliminary laboratory tests, skin extracts from the Brycon cephalus species resulted in behavioral changes in conspecifics. In view of this result, extracts from top of the chain and bottom of the trophic chain fish skins were applied in the draft tube using the built-in aeration system. Monitoring of the fish movement was executed in real time using a hydroacoustic system. The assays (n = 4) showed significant differences (p < 0.05) after insertion of the extract, showing the effectiveness of the application of skin extracts as a chemical repellent for ichthyofauna. Although the results may be affected by the concentration, richness of fish species, their maturity states, active predation, and mating instincts and environmental conditions, they are promising for the protection of ichthyofauna in hydroelectric projects.