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

Abstract

Using a large pan-European dataset, we compared least disturbed sites to sites impacted by human pressures across broad river types to assess which aspects of bio-ecological traits of the fish assemblage are most sensitive to alterations of the river ecosystem. To control for variation across river types and large-scale environmental gradients, we began by clustering the least disturbed sites (n = 716) into four homogenous fish assemblage types (FATs) differing by four fish metrics, i.e., lithophilic, rheophilic, omnivorous, and potamodromous fish. We predicted these FATs (headwater streams, medium gradient rivers, lowland rivers, and Mediterranean streams) using environmental variables, i.e., altitude, river slope, temperature, precipitation, latitude, and longitude for impacted sites in our dataset (n = 2,389). Using tests of sensitivity and intensity, 17 fish metrics showed a clear reaction to human pressures. However, 12 metrics responded exclusively within only one of the four FATs. Hence we observed a divergent reaction of fish metrics to human pressures in, e.g., headwater versus lowland rivers. Type-specific reactions are useful in customizing impact assessment for particular river types. It is of primary importance to understand the comparative sensitivity and efficiency of fish-based indicators of water quality for detecting humaninduced degradation of river ecosystems.

Functional redundancy and sensitivity of fish assemblages in European rivers, lakes and estuarine ecosystems

“…The river sites were assigned to four categories of fish assemblages, i.e. headwater streams (HWS), medium gradient rivers (MGR), lowland rivers (LLR), and Mediterranean streams (MES), that differs in their fish community and environmental characteristics 28 . Estuaries and lakes were assigned to two size categories, i.e.…”

A multiple index integrating different levels of organization

“…Lagadic et al (1997) warn about the limitations of single-level assessment approaches and some studies have combined community metrics and bioassays to quantify a spectrum of impacts (Gerhardt et al, 2004). The fish fauna has been extensively used either as biomarkers or as bioindicators since it integrate disturbance responses over several spatial scales (see Trautwein et al, 2013, for a pan-European bio-ecological trait based approach and Maceda-Beiga and De Sostoa (2011), who developed a rapid bioassessment protocol of fish species to stressors expressed at the micro and meso-habitat level). In our study we considered four levels of organization, namely the sub organism, the organism, the community level and ecosystem function, using two groups of aquatic organisms (benthic macroinvertebrates and fish) and a facet of ecosystem function (Fig.…”

Fish-Based Indices in Catalan Rivers: Intercalibration and Comparison of Approaches

“…A stepwise procedure based on Akaike's information criterion was used to select parsimonious, adequate GLMs. Then the observed values on the rest of sites are compared to the expected values (see, e.g., [71,72]) to compute an index that ranges from 0 (worst conditions) to 1 (reference conditions).…”