Taxonomic and functional distinctness of the fish assemblages differing among different types of reservoirs in south‐eastern Brazil

Abstract

The dynamics of fish assemblages in reservoirs depend on factors such as the morphometry of the catchment, habitat structure, and the uses of the reservoir. In the Paraíba do Sul (PSR) basin in southeastern Brazil, there are several types of reservoirs, some on the main channel, some are cascade reservoirs originated from a diversion of the waters of the PSR, and others are isolated reservoirs from tributaries. This study aimed to evaluate the influences of these three types of reservoirs on the taxonomic and functional distinctness of the fish assemblages. It was hypothesized that reservoirs on the main channel (more inflowing waters and habitat availability) have higher taxonomic and functional distinctness compared to cascade reservoirs, which in turn, have greater distinctness than isolated reservoirs. In addition, we expect assemblage structure to differ among these types of reservoirs because of the close relationship with local environmental conditions and habitat structure. Thirty measurements (26 quantitative and 4 categorical) from 34 fish species representing functional traits associated with locomotion, feeding, life strategy, and habitat use were taken. Fish assemblages differed among the three types of reservoirs, which was probably associated with different environmental and local habitat conditions. Higher taxonomic and functional distinctness were found for the isolated reservoirs, and lower for reservoirs on the main channel. This suggests that the fish fauna in this latter type of reservoir were probably composed of phylogenetically close and morphologically similar species. It is likely that limitation of the available resources induces fish to partition the available niches to coexist, favoring assemblages with species adapted to different functions. Our results demonstrate that assessing fish functional and taxonomic distinctness can be used to advance understanding of fish communities from reservoirs in Neotropical regions.

Unraveling trait‐based fish community assembly in tropical reservoirs

“…The importance of trait-environment relationships shaping fish assemblages was reinforced by the gradients of environmental conditions and functional traits that distinguished groups of reservoirs. The overall concordance between these emerging groups and types of reservoirs evidenced the importance of physical features to promote assembly processes (Mattos et al, 2022;Santos et al, 2017).…”

“…The importance of trait–environment relationships shaping fish assemblages was reinforced by the gradients of environmental conditions and functional traits that distinguished groups of reservoirs. The overall concordance between these emerging groups and types of reservoirs evidenced the importance of physical features to promote assembly processes (Mattos et al, 2022; Santos et al, 2017). Cascade reservoirs harbored primarily species without parental care (i.e., external fertilization and smaller pectoral fin) that inhabit open areas and feed on the bottom (i.e., primarily detritivores with inferior/subterminal mouth).…”

“…The fish species most affected by reservoirs are those that migrate, whereas small‐sized sedentary species with high reproductive potential and the ability to feed on the available food items are favored (Agostinho et al, 1999; Gomes & Miranda, 2001; Hoeinghaus et al, 2009). Thus, alteration of the natural flow may negatively impact the taxonomic and functional structure of fish assemblages (Mattos et al, 2022). As an ultimate consequence, fish fauna homogenization by environmental filtering processes may render fish assemblages in reservoirs more distinct taxonomically than functionally (e.g., Agostinho et al, 2008; Daga et al, 2020; Oliveira et al, 2018).…”

“…We used the aforementioned framework to investigate how trait–environment relationships drive the structure of fish assemblages in seven tropical reservoirs constructed along a major riverine system in southeastern Brazil. The complex is formed by cascade reservoirs and reservoirs blocking the main channel or isolated tributaries, which differentially affect the physical and biological characteristics of the riverine system (Mattos et al, 2022). In this tropical region, spatial and temporal changes in fish diversity are primarily modulated by dispersal limitation between reservoirs, loss of native species, and non‐native fish introductions (Loures & Pompeu, 2019; Pelicice et al, 2018).…”

Locality and the adaptation of river‐related built environment

“…A total of 195.22 km 2 of fluvisols can be found in Málaga, and about 42.5% are used for human activities. Mattos et al (2022) evaluated the influences of three types of reservoirs on the taxonomic and functional distinctness of the fish assemblages in the Paraíba do Sul (PSR) basin in southeastern Brazil. They hypothesized that reservoirs on the main channel with more inflowing waters and habitat availability have higher taxonomic and functional distinctness compared to cascade reservoirs, which, in turn, have greater distinctness than isolated reservoirs.…”