Passage of Mandi-Amarelo, Pimelodus Maculatus Through a Kaplan Turbine at Igarapava Dam

Igarapava Dam has been built in 1998 and a vertical slot fish ladder was constructed to allow fish migration. Monitoring studies showed that mandi-amarelo, Pimelodus maculatus, is one of the most abundant fish inside the fish ladder, with a passage rate of about 3,000 individuals/day. In this study we estimated the mortality rate of P. maculatus passing through Kaplan turbines in downstream movement after passing through the ladder. We radio-tagged 25 P. maculatus that were 26.3 to 35.5 cm (standard length) and weighed 520 to 1.250 g. We captured fish that had entered the fish ladder by dewatering it and netting the fish. We used electronarcosis to immobilize fish while we internally implanted a 8.9 g Lotek® coded radio tag with the antenna extending outside the body. Tagged fish were released in the Igarapava Reservoir 4 km upstream of the dam and were manually and automatically tracked from December 2002 to May 2005. Results showed that the majority of P. maculatus that reached the Igarapava Reservoir stayed within 8 km upstream of the dam. After 2 to 8 weeks in the reservoir, 7 fish (28%) moved downstream passing through the dam. Apparently 2 of them passed through the spillway and 5 through the turbines. Few fish moved downstream immediately after reaching the forebay area (2-7 min) while most of them stayed more than 1 h (1-70 hr) before passing through the turbine. Time of passage varied from 5-6 min and mortality rate was estimated at 80%.