Habitat variability and fish species structure in the Kończak stream

In the year 2008, studies on ichthyofauna were carried out in the Kończak stream. The stream was divided into four sections representing the variability of the water course. In each section, a research segment (100-150 meters long) was defined. In the ichthyofauna structure analysis, the indices of quantitative biocenotic domination and biomass were used. Furthermore, on the basis of the obtained data, the Shannon-Wiener indices of species diversity (H), as well as the abundance and the biomass (ABC index) were calculated. Altogether, in all research localities, 667 fish specimens were collected, with a total weight of 8,760 g and classified into 19 species. The caught fish were classified into 8 reproductive groups. Significant differences in the species composition and the number of fish were recorded between the particular sections. The number of species occurring in the studied sections oscillated between 2 and 17. The richest ichthyocenoses were recorded in the transitional and forest sections characterized by a comparatively small transformation of the habitats and good environmental conditions. In the remaining two sections, located in the middle and in the upper stream course, there was a distinct impoverishment of ichthyocenoses caused by the decreased attractiveness of the habitats.