Modelling Stream-Fish Functional Traits in Reference Conditions: Regional and Local Environmental Correlates

Abstract

Identifying the environmental gradients that control the functional structure of biological assemblages in reference conditions is fundamental to help river management and predict the consequences of anthropogenic stressors. Fish metrics (density of ecological guilds, and species richness) from 117 least disturbed stream reaches in several western Iberia river basins were modelled with generalized linear models in order to investigate the importance of regional- and local-scale abiotic gradients to variation in functional structure of fish assemblages. Functional patterns were primarily associated with regional features, such as catchment elevation and slope, rainfall, and drainage area. Spatial variations of fish guilds were thus associated with broad geographic gradients, showing (1) pronounced latitudinal patterns, affected mainly by climatic factors and topography, or (2) at the basin level, strong upstream-downstream patterns related to stream position in the longitudinal gradient. Maximum native species richness was observed in midsize streams in accordance with the river continuum concept. The findings of our study emphasized the need to use a multi-scale approach in order to fully assess the factors that govern the functional organization of biotic assemblages in ‘natural’ streams, as well as to improve biomonitoring and restoration of fluvial ecosystems.

The influence of environmental variables on the functional structure of headwater stream fish assemblages: a study of two tropical basins in Central Brazil

“…In this study, the altitude increases from east (Araguaia basin streams) to west (Tocantins basin streams) and is accompanied by a decrease in water temperature. A similar trend was observed in temperate streams, but involving latitudinal gradients and other variables than altitude and water temperature (Oliveira et al, 2012). These authors suggest that this trend corresponds to different forms of ecosystem functioning, ranging from warm water and lower altitudinal systems (in our study represented by Araguaia basin streams) to colder and high altitudinal systems (Tocantins basin streams).…”

“…Altitude is related to the regional topography and it influences functional traits composition of fish assemblages at both regional (Oliveira et al, 2012) and local scales (Bistoni & Hued, 2002;Pouilly et al, 2006). Our results provided evidence that altitude affects three functional traits of headwater fish species in different manners: body mass (positively), water column position (negatively to benthic species) and substrate preference (negatively to species with gravel and sand/gravel preference).…”

Die‐offs of the endangered pearl mussel Margaritifera margaritifera during an extreme drought

“…The Mente River has a length of 57 km, the Rabaçal River has a length of 88 km, and the Tuela River has a length of 102 km. All rivers experience a similar climate, with precipitation having high seasonal and interannual variability (Oliveira et al, ). Floods may occur during winter or early spring, with a gradual decrease in river flow that reaches minimum values in late summer or early autumn.…”

Conservation status of the freshwater pearl mussel Margaritifera margaritifera in Portugal

“…1). In this region the climate reflects the proximity to the Atlantic Ocean and altitude, ranging from temperate near the coast to Mediterranean more inland (Oliveira et al 2012). Precipitation levels have high seasonal and inter-annual variability, which is reflected in abrupt changes in the discharge regime of rivers.…”