Oral Presentation International Conference on River Connectivity (Fish Passage 2018)

Fish ladders at small hydropower plants and potential contribution to downstream passage of eggs and larvae (#174)

Eduardo Brambilla 1
  1. Departamento de Zoologia, Instituto de Biociências, Universidade Estadual Paulista, Thurgoona, NSW, Australia

Fish passage can potentially enhance downstream fish passage of larvae and eggs at small hydropower plants (SHP’s). To evaluate this hypothesis, two SHP’s located in the Sapucaí-Mirim River, Southeastern Brazil, both with weir-and-orifice type fish ladders were studied. Eggs and larvae were collected fortnightly between November 2016 and February 2017 (seasonal reproductive period) from set locations upstream of the dams, including the lotic, transition and reservoir. Additional downstream drifting samples were collected from within the fish ladders. Higher densities of eggs and larvae were collected, from all sampling sites, in December, January and early February. Larvae and eggs were only collected from the fish ladders during these periods and only during intense pluviosity events after river flow peaks. The low egg and larval abundance registered with the fish ladders, when compared with lotic, transition and reservoir sites, indicates that few eggs and larvae successfully move downstream through the fishway. They likely travel through turbines and/or the spillway, get eaten by predators or even simply drop out of drift. Increases in river flow has significantly influenced the passage through the fish ladders.