Passage and reproductive activity of fishes in the Igarapava fish ladder, Grande River, Southeastern Brazil

Abstract

AbstractWe sampled fishes within the vertical‐slot Igarapava fish ladder (IFL), Grande River, southeastern Brazil, and immediately downstream IFL in 12 field trips from February 2000 to December 2002. A total of 1145 fishes belonging to 13 families and 39 species were captured. The most abundant species captured within the IFL, in order of abundance were: Pimelodus maculatus, Metynnis maculatus, Astyanax altiparanae, Hypostomus spp., Leporinus octofasciatus, Salminus hilarii, Leporinus elongatus, Leporinus friderici, Schizodon nasutus and Prochilodus lineatus. Size distribution of the most abundant fishes captured downstream or within the IFL was similar indicating no constraints to adult fish to ascend the IFL. Except P. maculatus, the number of migratory species captured in the IFL and downstream the IFL were very low. Some of the so‐called sedentary species were collected in the IFL indicating that they possess an innate behaviour to migrate. Juveniles of P. lineatus and P. maculatus were captured ascending the IFL implying a dispersal behaviour. Gonadal analyses of the fishes captured in the reproductive season showed that the overall number of reproductive active fishes (which included fish in maturation, mature and spawned/spent) surpassed those non‐active. Thus, the IFL offers upstream passage for juveniles, some of the so‐called sedentary species, as well as fishes in reproductive migration. Copyright © 2009 John Wiley & Sons, Ltd.