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Environmental gradients in canyon-shaped reservoirs
Stodola, Jakub ; Petrusek, Adam (advisor) ; Seďa, Jaromír (referee)
The occurrence of environmental gradients in canyon-shaped reservoirs is influenced mainly by the size of reservoir and water retention time. The reservoir must be large and deep enough for environmental gradients to occur there. In such reservoirs vertical and horizontal gradients can be found. Presence of vertical gradients in lakes is relatively common, whereas horizontal gradients abound in deep canyon reservoirs. An example is the gradient of nutrients, the quantity of which decreases in the direction from the inflow towards the dam. Vertical abiotic gradients are the same for reservoirs and lakes. These are mainly gradients of light, heat, dissolved and oxygen. Some abiotic horizontal gradients may be present in both to reservoirs and lakes. The abiotic gradients also often affect the biotic ones. For example the gradient of nutrients affects the gradient of all organisms in the reservoir. Each species living in the reservoir prefers different type of environmental conditions, which may be given by a combination of these gradients. The areas preferred by particular cladoceran species can overlap quite extensively. In the Daphnia longispina species complex, co-occurrence of parental species may result in interspecific hybridization, and possibly formation of hybrid zones. The hybrids can often...
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Environmental gradients in canyon-shaped reservoirs
Stodola, Jakub ; Petrusek, Adam (advisor) ; Seďa, Jaromír (referee)
The occurrence of environmental gradients in canyon-shaped reservoirs is influenced mainly by the size of reservoir and water retention time. The reservoir must be large and deep enough for environmental gradients to occur there. In such reservoirs vertical and horizontal gradients can be found. Presence of vertical gradients in lakes is relatively common, whereas horizontal gradients abound in deep canyon reservoirs. An example is the gradient of nutrients, the quantity of which decreases in the direction from the inflow towards the dam. Vertical abiotic gradients are the same for reservoirs and lakes. These are mainly gradients of light, heat, dissolved and oxygen. Some abiotic horizontal gradients may be present in both to reservoirs and lakes. The abiotic gradients also often affect the biotic ones. For example the gradient of nutrients affects the gradient of all organisms in the reservoir. Each species living in the reservoir prefers different type of environmental conditions, which may be given by a combination of these gradients. The areas preferred by particular cladoceran species can overlap quite extensively. In the Daphnia longispina species complex, co-occurrence of parental species may result in interspecific hybridization, and possibly formation of hybrid zones. The hybrids can often...
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Dynamics of fish spatial distribution in reservoirs
ŘÍHA, Milan
This dissertation thesis focuses on several aspects of fish ecology in reservoirs and the methodology of their sampling. It is divided to three parts. The first part focuses on the dynamics of fish distribution throughout the seasons and between day and night. The second part deals with the efficiency and the selectivity of the beach seine net, trawl and purse seine net. The third part describes the long-term development of fish populations in the Římov Reservoir.
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