Efetividade da escada para peixes de uma barragem no rio Paraná para duas espécies migradoras neotropicais

Abstract

Large hydroelectric dams along the Paraná River have caused severe impacts on fish communities as they represent obstacles to long-range migratory species that need to migrate to complete their life cycle. Dams can bring numerous problems through the interception of migratory routes and reduction of spawning areas. The most common measures used to mitigate the effect of these physical obstacles is the implementation of fish ladders. It is not only important to implement these structures, but also to monitor them. This study was performed at the Engenheiro Sergio Motta Hydroelectric Power plant in the Upper Paraná River during December/2012 and March/2016. The aim of it was to evaluate the effectiveness of this structure in relation to the attractiveness rate and passage efficiency of to two Neotropical fish species in the fish ladder. In total, 563 fish of genus Leporinus (447 Leporinus obtusidens and 116 Leoporinus piavussu) were tagged and released with the implementation of 32-mm programmable transponders (PIT-tags). Radio Frequency Identification (RFID) was used to monitor the system. The attractiveness of the ladder was 8.7%. The minimum time to find it was 1.49 days for the fish released upstream and the maximum time was 449.86 days for the individuals released downstream. The release site had a significant influence on the entry rate of fish released on the other side of the river. No detection was observed for fish released downstream and upstream on the right bank of the river. Only the fish released on the same site where the fish ladder is located were detected, suggesting low attractiveness of the ladder in relation to the studied species. In the course of this study it was verified that for the two species studied it would be extremely important to increase the attractiveness at the entrance of the ladder, as well as to build a second ladder for fish on the right side of the river.