Disturbed fish fauna zonation as an indicator of large-scale human impact: A case study (2011–2012) of the large, lowland Warta River, Poland

Authors: Kruk, A., Ciepłucha, M., Zięba, G., Błońska, D., Marszał, L., Tybulczuk, S., Tszydel, M. and Penczak, T.

Journal: Journal of Applied Ichthyology

Volume: 33

Issue: 2

Pages: 174-188

eISSN: 1439-0426

ISSN: 0175-8659

DOI: 10.1111/jai.13297

Abstract:

The aim of the study was to assess whether ichthyofauna variability follows the natural downstream gradient or the degradation gradient, and to assess the bioindication potential of fish zonation. The study was conducted along the entire length (795 km) of the lowland Warta River, Poland, wherein the complexity of the ecotone zone and availability of hiding places for fish decreased downstream. The catchment of the middle course carried a heavy load of pollutants. In the lower course, groynes were common, the channel width exceeded 100 m and the mean discharge reached 210 m3/s. In 2011–2012, single-run electrocatches of fish and lampreys were performed at 73 sites, generally while wading along 100 m long reaches of both riverbanks (farthest upper course, depth ≤ 0.6 m) or drifting in a boat along a 500 m riverbank stretch (in the remaining river parts). An indicator species analysis allowed identification of species associated significantly with particular river sections: one (a rheophil) in the source fragment (S1), seven (all rheophilic) in the upper course (S2), three in the middle course (S3), and nine (including three rheophils) in the lower course (S4). On this basis, the S1 was classified as an impoverished grayling zone, S2 as a barbel zone, and S4 as the bream zone. Section S3 remained unclassified, as its ichthyofauna was in the worst condition due to: (i) the strong destabilizing upstream impact of the Jeziorsko dam reservoir, (ii) large amounts of wastewater discharged from towns located in the catchment area of this section and (iii) the lack of unpolluted tributaries that could serve as sources of recolonizers. In summary, in the human-modified Warta River, the variability of fish assemblages followed a degradation gradient, which was also reflected in the disturbed fish zonation. Consequently, this study confirms the usefulness of a fish fauna zonation analysis for the bioindication of large-scale human impacts in rivers.

Source: Scopus