Comportamento de passagem ascendente de Rhinelepis aspera na escada para peixes da UHE Engenheiro Sérgio Motta - CESP, rio Paraná

Abstract

Fish passages were conceived as a tool to mitigate impacts from the dams in rivers, blocking migratory fish routes, such as Rhinelepis aspera, species with high economic value, are found with reduced populations. Based on this the fish passage must be properly monitored for better management, and future planning. Objectives in our work is to evaluate attractiveness of R. aspera in a ladder for fish type tanks with orifices, also identify an efficiency of passage of the fish by the ladder. The study was carried out at the fish ladder at the Engenheiro Sergio Motta, in the Paraná River. There were marked (PIT-tags 32 mm) 200 R. aspera adults. The fish were released equitably at four points downstream of the dam, two left margin and two the right margin. Survival analysis for the evaluation of attractiveness and efficiency of the passage of the species. The entry rate of R. aspera was high, about 70% of the tagged fish entered the ladder. Loose hairs on the four points show a pattern of arrival and arrival rate (Log-Rank: x² = 2.53 and p = 0.46). Only 27% of the R. aspera who entered the ladder were able to effectively reach the exit. In addition, fish that failed to complete a passage through the ladder, remained on average for 36 days on the ladder. These results indicate that a species can easily find the fish ladder, however, the hydraulic characteristics of the ladder may be limiting an ascending passage of the species, thus reducing efficiency.