Climatic seasonality, hydrological variability, and geomorphology shape fish assemblage structure in a subtropical floodplain

Abstract

We applied a multiscale approach to understand the patterns of longitudinal, lateral, and temporal variability in fish assemblage structure of a large floodplain river and explored their relationships with climatic seasonality, hydrological variability, and floodplain geomorphology. We studied the fish assemblage structure of 35 connected lakes along a 600-km section of the Paraná River over 5 y. Longitudinal changes in fish assemblage structure were associated with a latitudinal climatic gradient, whereas temporal changes were associated with climatic seasonality and hydrological variability. Longitudinal and seasonal changes in assemblage structure were probably based on different thermal preferences of species that migrate seasonally along the main river axis. Extraordinary floods in summer promoted downstream dispersal of several species, which increased similarity between downstream and upstream regions. Thermal seasonality of this subtropical system was a strong factor driving temporal changes in assemblage structure, and the effects of the hydrological regime largely depended on flood pulses coincident with periods of warmer temperatures. Fish assemblages varied secondarily along a lateral gradient represented by types of geomorphic units distributed in the floodplain. The geomorphic units generated patchy environmental heterogeneity at the landscape scale that resulted in discontinuous patterns of fish assemblage structure. Assemblage composition was more similar among lakes belonging to similar geomorphic units but situated at geographically distant regions than among lakes belonging to different geomorphic units situated in the same region. Therefore, patterns in fish assemblage variation at regional and landscape scales appear to be determined largely by the dispersal and selection of suitable habitats by fish across the hierarchy of spatial and temporal scales.

Discrimination of hydrologic variations for spatial distribution of fish assemblage in a large subtropical temperate river

“…lateral connectivity variations), which produced changes in ß‐diversity of fish assemblages. These results are in line with Tejerina‐Garro and de Mérona (), Mims and Olden (), Abrial et al (), Górski, Collier, Hamilton, and Hicks (), Rabuffetti et al (), Scarabotti, Demonte, and Pouilly (), Abrial et al (), highlighting the importance of the hydrology in the structuring of fish assemblages.…”

Climate and rivers

“…Largely through research undertaken by hydro‐climatologists, it has become clear over the last 10–15 years that variations in atmospheric and oceanic circulation patterns, beyond the weather time scale and often referred to as modes of climate variability (de Viron, Dickey, & Ghil, ) are important determinants of river flow variability (McGregor, ) and thus a range of fluvial (Dibike, Shakibaeinia, Eum, Prowse, & Droppo, ; Lawler, McGregor, & Phillips, ; Nilawar & Waikar, ; Shrestha, Maskey, Babel, van Griensven, & Uhlenbrook, ) and ecohydrological processes (Gutierrez‐Fonseca, Ramirez, & Pringle, ; Leigh, ; Scarabotti, Danilo, & Pouilly, ). Given this, the purpose of this section is to outline what is meant by climate variability in a hydrological context, briefly introduce the broad approaches adopted in assessing climate river flow associations, and present the evidence for links between a range of modes of climate variability and river flow.…”

Ecological and phylogenetic determinants of life‐history patterns among ten loricariid species

“…During high waters periods, floodplain lakes becomes highly interconnected and connected with the main river through temporary channels. As in other large floodplain rivers, the timing and duration of flood pulses and warm temperatures influence fish assemblage composition and reproductive ecology (Bailly et al, 2011;Gorski et al, 2011;Scarabotti et al, 2011;Scarabotti et al, 2017).…”

“…In diverse Neotropical assemblages, loricariids partition their basal resources in an evolutionarily conserved manner, indicating that phylogeny can be a strong predictor of feeding ecology (Lujan et al, 2012). In the Paraná River, loricariids dominate fish biomass (Scarabotti et al, 2017) and are exploited as a fishery resource (Suzuki et al, 2000). They fulfil a fundamental ecological role in nutrient spiralling (Hahn et al, 2004) as well as linking the base of the food web with top predators (Bailly et al, 2011).…”