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Trophic structure of fish communities in the tributaries upstream of the Lipno Reservoir
Kofentová, Nikola ; Horká, Petra (advisor) ; Slavík, Ondřej (referee)
River obstacles, especially dams, are known to alter the natural environment in streams, which significantly impacts fish communities. The cyprinid species migrate from the reservoirs upstream to the reservoir's tributaries, where they may cause changes in the trophic structure of native fish communities. The aim of this study was to evaluate the trophic structure of the fish community composed mainly of cyprinid and salmonid species throughout seven localities in the Vltava River upstream of the Lipno reservoir. Stable isotope analysis was used to identify trophic positions, trophic niche width and trophic niche overlap between species. Trophic relationships of individual species were then evaluated to assess the potential for food competition. The trophic niche width of the salmonid species was significantly higher than that of the cyprinid species. Trophic niche overlap between salmonids and cyprinids was observed, with the most significant overlap being with both common dace Leuciscus Leuciscus and common roach Rutilus rutilus, suggesting a potential competition for food. The effect of the presence of cyprinids on the trophic niche width of salmonids was shown not to be statistically significant. From the perspective of protecting native salmonid species, there should be special attention paid...
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The effect of barriers on riverine fish communities
Kofentová, Nikola ; Horká, Petra (advisor) ; Čech, Martin (referee)
The construction of river obstacles is considered one of the major threat to freshwater ecosystems worldwide, with a greater impact upon riverine fish than any other human activity. River obstacles, especially dams and weirs, affect the natural environment in streams and rivers, causing changes in physical, chemical and biological processes and disrupting connectivity of rivers via alternating series of lotic and lentic reaches. The effect of obstacles is further magnified by associated habitat alterations like are channelization, flow regulation, fortification and deepening of a riverbed. Orga- nisms and especially fish that live in rivers are highly sensitive to these changes, which affects them at the level of individuals, species and the whole populations. The most pronounced is the barrier-effect to upstream and downstream migration and loss of habitats. Diadromous and rheophilic species of fish are the most sensitive ones as they have complex migration strategies and habitat requirements. Fish are further affected by obstacles via many other mechanisms, such as the effect on reproduction success, growth and development, changes in the composition and trophic structure of communities and restricted response to further environmental constraints including water pollution or predicted climate...
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