Pressure-specific and multiple pressure response of fish assemblages in European running waters

Abstract

We classified homogenous river types across Europe and searched for fish metrics qualified to show responses to specific pressures (hydromorphological pressures or water quality pressures) vs. multiple pressures in these river types. We analysed fish taxa lists from 3105 sites in 16 ecoregions and 14 countries. Sites were pre-classified for 15 selected pressures to separate unimpacted from impacted sites. Hierarchical cluster analysis was used to split unimpacted sites into four homogenous river types based on species composition and geographical location. Classification trees were employed to predict associated river types for impacted sites with four environmental variables. We defined a set of 129 candidate fish metrics to select the best reacting metrics for each river type. The candidate metrics represented tolerances/intolerances of species associated with six metric types: habitat, migration, water quality sensitivity, reproduction, trophic level and biodiversity. The results showed that 17 uncorrelated metrics reacted to pressures in the four river types. Metrics responded specifically to water quality pressures and hydromorphological pressures in three river types and to multiple pressures in all river types. Four metrics associated with water quality sensitivity showed a significant reaction in up to three river types, whereas 13 metrics were specific to individual river types. Our results contribute to the better understanding of fish assemblage response to human pressures at a pan-European scale. The results are especially important for European river management and restoration, as it is necessary to uncover underlying processes and effects of human pressures on aquatic communities.

Eco-hydrologic model cascades: Simulating land use and climate change impacts on hydrology, hydraulics and habitats for fish and macroinvertebrates

“…Land use scenarios had a minor effect on discharge and hydraulic habitat conditions but markedly affected water quality (nitrate concentrations). However, the predicted nitrate changes were well in the tolerance range of the modelled fish species (Wolter et al, 2003;Schinegger et al, 2013) and thus not considered a potential limiting factor for fish (Wolter et al, 2003).…”

“…Moreover, it must be noted that this assessment was solely based on the depth and flow preferences of the species, whilst riverine fish are often markedly limited by the availability of gravel substrates for spawning (Mann, 1996;Wolter et al, 2003;Schinegger et al, 2013), which was not considered in this study since the bottom substrate of the study reach was pure sand and only small gravel patches were found in the Treene River.…”

Divergent reaction of fish metrics to human pressures in fish assemblage types in Europe

“…This simplification was necessary to overcome the multitude of combinations from four river types with 129 metrics. Schinegger & Trautwein (2013) focused on metric responses to specific and multiple pressures (hydro-morphological pressures or pollution pressures) and could identify metrics that responded specifically to pollution pressures and hydromorphological pressures. However, human pressures are widespread and Schinegger et al (2011) showed that rivers in the alpine region are predominately affected by hydromorphological pressures, whereas pollution pressures mostly in combination with hydromorphological pressures prevail in LLR.…”

“…6). Schinegger & Trautwein (2013) found that most metrics of any functional trait responded to multiple pressures instead to specific pressures. Further research should investigate whether impact strength (e.g., low, medium, and strong) is better explained by density or biomass metrics.…”

Hy:Con: A Strategic Tool For Balancing Hydropower Development And Conservation Needs

“…Although HPP is considered as a climate‐friendly energy source, HPPs are also associated with ecosystem degradation and cause pressures like water abstraction (Arthington et al , ; Huckstorf et al , ), hydropeaking (Saltveit et al , ; Schmutz et al , ), impoundments (Reid, ) and fragmentation (Nilsson et al, ). Together with non‐hydropower‐related impacts, these multiple stressors threaten biodiversity (Schinegger et al , ; Trautwein et al , ; Vörösmarty et al , ) and counteract the aims of the EU Water Framework Directive (WFD; 2000/60/EG; European Commission, ) and the Habitats Directive (HD, 92/43/EEC; European Commission, ). Even under consideration of mitigation measures (e.g.…”