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The importance of various habitats for fish in reservoirs
Šmejkal, Marek ; Prchalová, Marie (advisor) ; Vašek, Mojmír (referee)
Fish distribution in reservoirs is not homogeneous. Fish usually occur in upper parts of reservoirs on the longitudinal axis, where is also the greatest concentration of nutrients. Fish abundance and biomass as well as the trophy are declining towards the dam part. On the vertical axis, most fish occur above the thermocline, where temperature and concentration of dissolved oxygen reach the highest values. Fish community is changing also in time. Shortly after impoundment, the riverine species are dominating the community and later, generalist species prevail. Generally, we can distinguish pelagic and bentic habitats within the reservoir. There are species in reservoirs that occur almost strictly in pelagic habitat like asp and bleak and benthic species like ruffe and perch. Most species occur in both types of habitats (bream, roach, pikeperch, European catfish, white bream). Migrations between habitats occur on daily and on seasonal basis. On daily basis, we distinguish diel horizontal migration, in which fish shift between pelagic and benthic habitats. Diel vertical migration, when fish change depths, is not so significant in Czech reservoirs. Motivations for these diel migrations are food aviability, predation pressure and water temperature. Seasonal migrations comprise spawning migrations and winter...
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The importance of various habitats for fish in reservoirs
Šmejkal, Marek ; Vašek, Mojmír (referee) ; Prchalová, Marie (advisor)
Fish distribution in reservoirs is not homogeneous. Fish usually occur in upper parts of reservoirs on the longitudinal axis, where is also the greatest concentration of nutrients. Fish abundance and biomass as well as the trophy are declining towards the dam part. On the vertical axis, most fish occur above the thermocline, where temperature and concentration of dissolved oxygen reach the highest values. Fish community is changing also in time. Shortly after impoundment, the riverine species are dominating the community and later, generalist species prevail. Generally, we can distinguish pelagic and bentic habitats within the reservoir. There are species in reservoirs that occur almost strictly in pelagic habitat like asp and bleak and benthic species like ruffe and perch. Most species occur in both types of habitats (bream, roach, pikeperch, European catfish, white bream). Migrations between habitats occur on daily and on seasonal basis. On daily basis, we distinguish diel horizontal migration, in which fish shift between pelagic and benthic habitats. Diel vertical migration, when fish change depths, is not so significant in Czech reservoirs. Motivations for these diel migrations are food aviability, predation pressure and water temperature. Seasonal migrations comprise spawning migrations and winter...
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Pilot study on the efficient use of ponds greater than 100 hectares
Mrkvová, Markéta ; Jurajda, Pavel ; Adámek, Zdeněk ; Zukal, Jan
Fish distribution in carp ponds tends to be uneven as fish prefer those parts nearer the feeding sites. As such, carp usually only occupy around two thirds of the pond area. Compared with more remote parts of the pond, control sampling campaigns showed the regular occurrence of significantly larger fish at the feeding sites. Further, fish located on the feeding sites consumed cereals almost exclusively, whilst those outside the feeding sites grazed predominantly on zooplankton. Environmental parameters at the feeding sites differed from those in the surrounding area, particularly in relation to the post-feeding period. We recommend that fish farmers both increase the size of feeding sites and alternate feeding at different sites in an effort to spread the fish stock over the whole pond area, thereby better utilising natural food resources.
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Spatial distribution of fish in reservoirs and lakes
MUŠKA, Milan
This thesis is focused on the fish spatial distribution and its changes mainly during the diel cycle. In the first part, I described the fish spatial distribution in the tropical lake ecosystem of Lake Turkana. The second part deals with the fish spatial distribution in a temperate reservoir on the different spatial scales from in/offshore habitats over the fine-scale to the level of individuals. The linkage of fish distribution patterns with selected environmental variables was also evaluated.
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