Influence of seasonal, diel, lunar, and other environmental factors on upstream fish passage in the Igarapava Fish Ladder, Brazil

• Published in: Ecology of freshwater fish Vol. 18; no. 3; pp. 461 - 472
• Main Authors: Bizzotto, P.M, Godinho, A.L, Vono, V, Kynard, B, Godinho, H.P
• Format: Journal Article
• Language: English
• Published: Oxford, UK Oxford, UK : Blackwell Publishing Ltd 01.09.2009; Blackwell Publishing Ltd
• Subjects: Bryconamericus stramineus; fish migration; Freshwater; Grande River; Leporinus; Leporinus friderici; Neotropical fish passage; Paraná River basin; Pimelodus maculatus; Prochilodus lineatus; vertical-slot fish ladder; Brazil, Grande R
• ISSN: 0906-6691; 1600-0633
• DOI: 10.1111/j.1600-0633.2009.00361.x

Upstream fish passage was evaluated during 12 months in the vertical-slot Igarapava Fish Ladder constructed around Igarapava Dam, in the heavily dammed Grande River, Southeast Brazil. A video monitoring system was used to observe 61,621 fish that passed the ladder, of which 93.5% were identified to 15 taxa. Among the migratory species, the most abundant were Pimelodus maculatus (33.6% of all fish), Leporinus octofasciatus (31.4%), Leporinus friderici (4.5%), and Prochilodus lineatus (3.1%). Seven taxa were classified as nonmigratory, and of these taxa, the small Bryconamericus stramineus was the most abundant (12.7%) of all fishes. Passage of the 'nonmigratory' taxa upstream in the ladder shows they are migratory in this system and have a strong behavioural drive to move to upstream habitat. Passage of most taxa had a strong seasonal pattern. While some species passed primarily during the day, others showed a distinct nocturnal pattern. Lunar phase and water temperature also strongly affected passage of some taxa. Rainfall and dam discharge had a small or null influence on most taxa; perhaps due to the fairly small catchment area of the reservoir and the highly regulated discharge at Igarapava Dam.