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The effect of floods on the ichthyofauna of Štěpánovský stream
Čech, Martin ; Čech, P.
The effect of floods on the ichthyofauna of Štěpánovský stream (left-hand affluent of Sázava River, aver. summer flow rate 0.2 m3s-1) was studied using diet analysis of kingfisher A. atthis preying exclusively on local fish community. The first local flood event (2 August 2001; flow rate 100 m3s-1) caused drastic shift in the ichthyofauna composition from original fish community dominated by brown trout S. trutta, brook trout S. fontinalis and bullhead C. gobio to fish community dominated by bleak A. alburnus, roach R. rutilus, chub L. cephalus and gudgeon G. gobio. The second flood event (all Czech Republic floods in August 2002; flow rate 4 m3s-1) was surprisingly much less destructive to fish fauna. Consequently, the stream played also the role of refuge for many new fish species including juveniles of nase C. nasus, vimba bream V. vimba, barbel B. barbus, asp A. aspius and sunbleak L. delineatus, from highly flooded Sázava River.
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Distribution and diversity of fish fry in different habitats of the Slapy reservoir
Kratochvíl, M. ; Kubečka, Jan ; Matěna, Josef
The fish fry assemblages of the Slapy reservoir (Czech Republic) were studied in May and June 2002. The aim of this study was to estimate diversity and distribution of fish fry in three habitats – epipelagic (depth 0 – 4 m), bathypelagic (depth 10 – 16 m) and littoral areas. Percids were present both in epipelagic and bathypelagic areas, while cyprinids preferred living in upper layers of the water column. During the dusk, bathypelagic fish started migration towards surface layers, throughout the dawn they returned back to the deeper layers. The highest densities of fish fry were observed in epipelagic zone during nighttime. Perch was revealed as the dominant fry species in Slapy reservoir, pikeperch was also abundant in the open water. Both during day and night, perch was usually the most common species in all habitats, cyprinids were most abundant in the littoral zone in May, only.
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Ichtyofauna of the border Malše River
Matěnová, V. ; Matěna, Josef
Ichthyological investigation of the border section of the Malše River was performed in 2002 and 2003. The occurrence of brook lamprey larvae and five rheophilous fish species was confirmed – brown trout, common sculpin, grayling, burbot, stoneloach. Species escaping from fishponds – perch and common carp were found in negligible numbers. The brown trout dominated in numbers at all investigated profiles. The length and age analysis of the brown trout population showed the dominance of YOY fish, the population exhibited a harmonical age class composition. Results confirmed successful natural reproduction of trout, grayling, burbot and bullhead. The following investigation in 2003 oriented specially on the occurrence of brook lamprey proved that the population remained unaffected by the floods in 2002. The border Malše River represents an athropogenically slightly affected watercourse with suitable conditions for natural reproduction of all indigenous species found during the study.
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Development of the fish assemblage in a restored river backwater
Hohausová, Eva
The restoration of the Kurfürst backwater was undertaken between December 1993 and November 1994. Already during the restoration, the number of fish species (>1+ fish) increased to 12, compared to 9 recorded before it. The following monitoring programme (1995-99) revealed further increases, up to 17 species. The structure of the fish assemblage, in terms of main species, reproductive and ecological groups, did not differ substantially between years, regardless of seasonal changes. Six species were newly recorded after restoration. Most species were found as both, 0+ and older fish, as many species probably spawned in or used the backwater as a nursery. The structure of the 0+ fish assemblage was also similar both before and after the restoration. After the 6-year monitoring, the restoration of the backwater can be considered as of benefit for the fish assemblage. Now, much will depend on the following development of the backwater, if it can further serve for local fish populations.
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Modelování hydrodynamiky a kvality vody v dimiktické nádrži – nádrž Jordán, Česká republika
Hejzlar, Josef ; Jarošík, Jiří ; Borovec, Jakub ; Růžička, Martin
The two-dimensional, dynamic model CE-QUAL-W2 was used to model water quality of a small, highly eutrophic reservoir with intensive nutrient cycling between the water column and bottom sediment. The model was calibrated and evaluated for a 4-year, hydrologically variable period and used in a scenario simulation study to analyse effects of the changing external and internal phosphorus loading and depth of outflow to trophic conditions and water quality. The reservoir hydrodynamics were simulated with good precision in all parts of the seasonal cycle and during the whole period. Water quality and nutrient cycling could be calibrated and simulated with satisfactory results for individual years, however, an extrapolation of model to conditions with different nutrient loading was problematic. It spite of this partial limitation, the model was found appropriate for water quality evaluation and prediction in Jordan Reservoir.
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Transport fosforu v říční síti podhorského povodí se smíšeným využitím uzemí (povodí Malše, ČR)
Turek, Jan ; Hejzlar, Josef ; Žaloudík, Jiří
Phosphorus sources and transport in the river network were evaluated for a medium size (437 km2), upland catchment with mixed land use (forests, farmland, urban) located in South Bohemia during 1999-2003. Dissolved P concentrations in streams in completely forested catchments, farmland catchments, and municipal wastewater treatment plant (WTP) effluents were /~0.015, <0.01 to 0.25, and up to 2 mg/l, respectively. High particulate P concentrations (up to 0.6 mg/l) occurred in all streams during surface runoff events, irrespective to land use, and even higher in WTP effluents (up to /~4 mg/1). Analysis of P fluxes in the river network showed a significant annual retention of both dissolved P (26 to 41% of all sources) and particulate P (27 to 67% of all sources).
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Model analysis of effects of hydrodynamics and nutrient loading to water-quality in a dimictic reservoir (Jordán)
Jarošík, Jiří ; Hejzlar, Josef ; Borovec, Jakub ; Růžička, Martin
The dynamic, two-dimensional model CE-QUAL-W2 was used to simulate recovery conditions in the eutrophic Jordan Reservoir. The aims were: (i) to calibrate the model and discuss differences between simulated and measured data; (ii) to use the calibrated model to determine the effects of external and internal phosphorus load and the depth of outlet on trophic conditions. After calibration the model reproduced thermal stratification, oxygen regime and concentrations of NO3-N with sufficient precision. Simulation of PO4-P was less exact. The results of mathematical simulation showed that (i) the required mesotrophic level cannot be accomplished without a significant decrease in inflow concentration of total phosphorus; (ii) the internal load of phosphorus is small and become insignificant after decrease of external load; and (iii) the use of bottom outlet is a potentially efficient method to partly decrease trophic level of Jordan Reservoir.
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