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Macrophyte banks and fish early stages in a cascade of small hydropower reservoirs (Southeast Brazil): temporal changes along the reproductive cycle and influence of the limnological and spatial organization

Rafaela Kimura , Eduardo Brambilla , Marcos Nogueira

Abstract

Context: Small Hydroelectric Power Plants (SHPs) are worldwide-distributed infrastructures, whose ecological impacts are still poorly known. Aim: To evaluate the role of littoral macrophytes as nursery areas for fishes in a cascade of three SHPs reservoirs (Southeast, Brazil). Methods: Three random macrophyte banks, from the intermediate and lentic compartments of each reservoir, were sampled (manual sieve and gillnets) monthly along the peak of the reproductive period. Basic limnological variables were simultaneously measured. Key results: Eighty-eight larvae and 393 juveniles were captured, corresponding to 29 taxa, almost 30% of the regional pool of fishes in the river. Non-migrants and short-distance migrants (with/without parental care) predominated. The species accumulation curve tended to an asymptotic configuration (whole dataset sampling effort). Fishes abundance differed, mainly, temporally, and in lower degree, spatially. Higher diversity (rarefaction/extrapolation curves) occurred both in the beginning of the reproductive peak and in the first (upstream) reservoir, where there was also a good correspondence between observed and estimated richness, 90%. Conclusions: The macrophyte banks in these SHP reservoirs are effectively used as nursery areas. Implications: Results provide subsides for actions of conservation and management of the local/regional ichthyofauna, in a condition where typical nursery areas do not exist.

MF23142  Accepted 12 November 2024

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