Monitoring a Vertical Slot Fish Ladder at Baguari Dam, Doce River, Brazil

To allow upstream fish migration a vertical slot fish ladder was built at Baguari Dam, starting its operation in December, 2009. This work will present preliminary data evaluating fish composition and distribution at the ladder and its efficiency. Fish were captured immediately downstream and upstream of the dam with gill nets, with mash size varying from 3 to 16 cm between opposite knots. Also we captured fish inside the ladder by dewatering it. Twelve samples were obtained from January to December, 2010. Data were analyzed using the CPUE for the gill net samples. We also calculated the frequency of fish species inside the fish ladder and the similarity of species at the three sample areas (downstream, upstream and ladder). We captured 21 species downstream, 23 upstream and 22 inside the ladder. Data showed a considerable reduction in fish abundance downstream and upstream after the rainy season causing a reduction of fish frequency inside the ladder. Among migratory species Leporinus conirostris was the most abundant at the three sample sites. Also it is important to notice that alien migratory species as the dourado Salminus brasiliensis and the curimba Prochilodus costatus were also captured inside the ladder at a great abundance. Also, we noticed that the flow at the spillway that operates throughout the year attracted a considerable amount of fish to that area, reducing the efficiency of the ladder to pass fish moving upstream.