Determinação da eletrosensibilidade de peixes como medida de manejo em reservatórios hidroelétricos neotropicais

Abstract

This study was conducted to determine the electrosensitivity thresholds of juvenile and adult Neotropical migratory fish, consisting of two experimental trials. Initially, the electrosensitivity thresholds were determined in juvenile curimba (Prochilodus lineatus), pacu (Piaractus mesopotamicus) and piapara (Megaleporinus obtusidens). P. lineatus showed greater tolerance to electric fields, withstanding higher voltages at all electrosensitivity thresholds and faster recovery times. On the other hand, M. obtusidens stood out for being more influenced by electric voltages, resulting in faster electrosensitivity responses and longer recovery times. The second assay was conducted on adult and juvenile P. lineatus individuals, the species that showed greater tolerance in the first phase of the experiment. Ten juvenile fish with an average standard length of 4.4 centimeters and 28 adult fish with an average of 26.6 centimeters were used. The analyses revealed significant differences between the groups, evidencing that adults were more sensitive to electric fields than juveniles. Furthermore, recovery times further accentuated this variation in the fish's response to electric fields, indicating that the influence of electric current is significantly stronger in larger individuals. In this sense, adult P. lineatus showed an initial reaction to the effect of the electric field before the reactions of juveniles, with statistically significant differences (p < 0.05) in both electrosensitivity and response times. This suggests that fish size exerts a considerable influence on their reactions to electric fields, and that younger and smaller individuals are less affected by electric fields than larger and older ones, both in terms of voltage intensity and reaction speed. Therefore, an electric deterrent barrier adjusted to the electrosensitivity thresholds of juvenile P. linetus would be effective in repelling both P. mesopotamicus and M. obtusidens juveniles, as well as adults of P. lineatus, since the barrier would be defined under the highest established thresholds.