The impact of eutrophication and turbidity on riverine fishes

There is currently a rapid decline in the amount in freshwater species and they face extinction. The risk of extinction of freshwater organisms is much greater than that of terrestrial ones, and almost 40 % of freshwater fish are currently facing extinction. In addition to the overexploitation of freshwater ecosystems and their degradation, eutrophication is one of the most significant threats to river ecosystems, leading to significant changes in biodiversity. Eutrophication causes severe changes in river ecosystems, which have a positive effect on some fish species but an adverse effect on other fish species. Due to eutrophication, water becomes turbid due to the development of cyanobacteria and algae, changes in the oxygen concentration in the water, pH level fluctuation, the presence of toxic substances and clogging of the bottom with fine sediment. The aim of this master thesis was to describe the influence of environmental factors related to eutrophication on the number of selected fish species caught in the Czech Republic, in the Vltava and Ohře river basins, in a total of 47 locations. Individual environmental factors (14), which describe changes in the ecosystem caused by eutrophication, were tested for the caught fish using generalised linear mixed models (GLMM). The results of my work..