The Impact of the Morphology of Mountain Watercourses on the Habitat Preferences Indicated by Ichtyofauna Using the Ifim Methodology

Abstract

A natural channel differs from a prismatic one by its rich variability. Regulated rivers have a geometrically regular shape that is not suitable for the instream biota. The morphology of a regulated river is the main cause of habitat changes. The article provides the results of research that was focused on assessing the impact of a channel's morphology on the instream habitat preferences by ichthyofauna. In the article the ichthyofauna is represented by brown trout (Salmo trutta m. fario). During the years 2015 and 2016, research was carried out for 13 reaches of mountain watercourses in Slovakia. These reaches were geodetically measured, and a hydraulic model was created. The ichthyological survey was focused on the fish's habitat preferences. A set of data was created from the results that was statistically evaluated by cluster analysis, and the correlation relations for the abiotic and biotic characteristics of the watercourses were evaluated. The individual evaluations provide mutually compatible results. It can be concluded from the results that bioindications by fish provide reliable results in relationship to the changes in habitats in regulated rivers. There was an unambiguous statistical correlation in the preferences of brown trout in the regulated and natural rivers.

Evaluation of the Methodology to Assess the Influence of Hydraulic Characteristics on Habitat Quality

“…From the results of the study [15], it follows that there is a strong dependence between habitat and water depth and a low dependence on flow velocity. Based on the above results, a change in habitat quality, according to three methods, was examined.…”

“…The location of selected streams is shown in Figure 1. The results of the ichthyological survey are stated in [15].…”

“…Fishes as bioindicators have been selected because of their suitability for assessing the ecological integrity of rivers, for their sensitivity to changes in river habitats, occurrence, longevity, and mobility [11,14,15]. Changing the riverbed morphology and, hence, faster water heating is a significant threat to fish, as they are ectothermic animals [16].…”

“…Further research [15] compared the differences in geomorphology between natural and regulated streams and their impact on biota, since natural channels differ from prismatic ones by their rich variability of the cross-section (XS) and longitudinal channel profiles. Typical consequences of geometrical river regulations for the biota are the reduction of original instream habitat complexities and habitat availabilities in increasingly uniform riverbeds [21].…”

“…When selecting a suitable bioindicator, it should be taken into account that different species of fish prefer different habitats and that the age of individuals has a significant influence on habitat selection [23]. Microhabitat preferences of adult brown trout (Salmo trutta m. fario) were monitored in the preliminary studies [15,24]. The habitat preferences were evaluated during the summer period of minimum flows.…”