Abstract
ABSTRACT Dams often cause drastic changes in freshwater environments and can compromise the quality and availability of food resources in rivers. This study aims to analyze the influence of a dam on the trophic structure of fish assemblages in lotic areas located both upstream and downstream of the Irapé Hydroelectric Power Plant. Fish sampling occurred before (2003 to 2005) and after (2011 to 2017) the impoundment, which began in 2006. The trophic structure and species composition before dam construction were similar upstream of the reservoir and downstream of the dam. After the building of the dam, both aspects of the assemblages changed along the lotic stretches - the upstream incurred an increase in biomass of detritivores and a decrease of piscivores and omnivores, while downstream went exactly the opposite, causing a differentiation between the two assemblages. Because lotic areas upstream of reservoirs are also impacted by river damming, efforts for impact mitigation should also focus on these areas.
Highlights
Feeding is a dynamic process and diet can change based on shifts in ecologic conditions
Impoundments affect the natural flow regime, which is a key driver of river ecology (Bunn, Arthington, 2002) by determining channel morphology, habitat diversity, and substrate stability (Power et al, 1995; Nilsson, Svedmark, 2002)
10 species were classified as detritivores, 2 as herbivores, 3 as insectivores, 10 as omnivores, and 6 as piscivores (S1, S2)
Summary
Feeding is a dynamic process and diet can change based on shifts in ecologic conditions. These changes can affect growth, survival, and demographics of assemblages, and affect the transfer of energy across the systems (Brodeur et al, 2017). Damming alters the trophic ecology of rivers by causing fragmentation, changing the natural flow regime, and creating new reservoirs. Fragmentation affects the fundamental processes and functions of healthy rivers, altering the natural flow of energy and nutrients (Dudgeon et al, 2006; Nestler et al, 2012). Impoundments affect the natural flow regime, which is a key driver of river ecology (Bunn, Arthington, 2002) by determining channel morphology, habitat diversity, and substrate stability (Power et al, 1995; Nilsson, Svedmark, 2002). Reservoir creation causes a drastic transformation from a lotic to lentic habitat, changing the physical, chemical, and geomorphological characteristics of the area (Agostinho et al, 2007)
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