Fish trophic guild responses to damming: Variations in abundance and biomass

Abstract

Dams and associated reservoirs cause drastic changes in the composition and structure of ichthyofauna. Therefore, functional groups within a fish assemblage may respond distinctly to such human interventions in rivers. The objective of this study was to evaluate how fluctuations in fish abundance and biomass differ among trophic guilds. Fish were sampled before and after damming four reservoirs, in their inner areas (more heavily impacted areas) and upstream (less impacted areas). To evaluate possible changes, we used a before–after and control‐impact experimental design. Fish were classified into trophic guilds through diet analysis and based on information available from the literature. Six trophic guilds were identified. The effect of periods (before and after damming) and sites (more and less impacted) on abundance and biomass differed among the trophic guilds. Highly specialized trophic guilds, such as herbivores and detritivores, were negatively affected by damming. Invertivores were negatively affected in the impacted area and increased in abundance and biomass in the less impacted sites. The findings of this study show that modifications imposed by damming are reflected in the abundance and biomass of fish trophic guilds, but the degree of such impacts vary according to characteristics of the considered trophic guild.

Ecologia alimentar de Hassar affinis (Actinopterygii: Doradidae) em dois lagos de uma zona úmida de importância internacional no Nordeste do Brasil

“…Studies have shown that omnivorous species feed mainly on aquatic insects, fruits and debris (Venere & Garutti, 2011). Dias et al (2020) studying the abundance and biomass of fish from dams in Paraná and Tocantins describes as omnivorous organisms that consume plants ranging from algae to higher plants and invertebrate animals and fish, a characteristic similar to that observed in the species of the present study, although the consumption of the fish item is not observed in the species in question.…”

“…Arantes (2009), in his work with a species of the family Doradidae, describes results like the present work, where he classifies the species with an opportunistic omnivorous habit. Dias et al (2020), studying dam species also highlights the opportunistic habit for omnivorous species. For Agostinho et al (1992), in most cases of fish in this family, different food items were found in the stomach of the same individual, which is following with the omnivorous habit of the species.…”

Partitioning fish communities into guilds for ecological analyses: an overview of current approaches and future directions

“…Despite their ease of application, occurrence methods are criticized for their inability to provide information on the overall contribution of a prey item to diet composition (Hyslop 1980). Other commonly used measures include those based on percent prey counts and percent contribution by mass or volume (e.g., Usui et al 2018;Liu et al 2019;Dias et al 2020). These metrics, which require more labour to quantify, provide more information on the contribution of individual prey items to the diet, yet have their own biases.…”

Taxonomic and functional homogenisation of zooplankton after river damming in Central Brazil

“…Over half of the volume of rivers is altered by regulation or fragmentation of the global volume (Grill et al, 2019). Dams take away the ability of rivers to flow freely, reduce seasonal variation, and alter the natural connectivity between system environments (Dias et al, 2020; dos Santos et al, 2018, 2020) which are essential for providing efficient dispersal and restoration of species, ensuring high diversity (Ward & Tockner, 2001). With the reduction of environmental heterogeneity, there is a homogenisation of habitats; thus, biological communities are altered, reducing their functional and structural complexity (Almeida et al, 2019).…”