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Biomanipulation measures at the Hamry water supply reservoir - poor reaction of phytoplankton to planctivorous fish reduction
Jurajda, Pavel ; Adámek, Zdeněk ; Janáč, Michal ; Roche, Kevin ; Mikl, Libor ; Rederer, L. ; Zapletal, T. ; Koza, V. ; Špaček, J.
One measure commonly used for improving water quality in open waters is biomanipulation of fish stock. Previous studies in shallow lakes confirm the importance of reducing cyprinid populations for increasing zooplankton. Empirical results from reservoirs, however, are scarce. The aim of this study was to evaluate the effect of an intensive reduction of cyprinid fishes and perch fry density between 2009 and 2013 on water quality in the Hamry drinking water reservoir. The abundance of common bream broodstock decreased by around 12 000 individuals over the five years, and biomass dropped below 20 kg.ha-1. Stocking with pike and zander proved less effective. In reservoirs similar to Hamry, reduction of bream biomass can be a highly effective means of increasing filtering zooplankton biomass. Phytoplankton dynamics, however, appear to depend on additional factors, with nutrient loading (especially phosphorus) probably playing the primary role.
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Ichthyological and hydrobiological survey of the Hamry water reservoir
Jurajda, Pavel ; Adámek, Zdeněk ; Konečná, Markéta ; Jurajdová, Zdenka ; Janáč, Michal ; Ondračková, Markéta ; Chaloupková, Lucie ; Štěpina, Jan ; Šlapanský, Luděk
This study, which has been running since 2008, examines the use of the Hamry Water Reservoir as a model for fish community biomanipulation studies with the aim of improving water quality. Of primary interest to the Reservoir administrators, the Elbe River Basin authority s.p., is the maintenance of high water quality for drinking purposes, thereby preventing conflict of interest with multiple stakeholders. In addition, the study aims to determine whether biomanipulation of fish communities can be undertaken effectively in a reservoir.
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Fish community as an indicator of river degradation
Jurajda, Pavel ; Janáč, Michal ; Ondračková, Markéta ; Adámek, Zdeněk ; Valová, Zdenka ; Streck, G. ; Machala, M. ; Wenger, M. ; Segner, H.
V příkladové studii na Bílině se ryby na úrovni společenstva projevily jako dobrý a rychlý indikátor ekologického stavu toku, avšak pro indikaci chemických látek v řece je nutné hodnotit specifické parametry na úrovni jedince.
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Young of the year fish assemblage structure of the Czech Elbe river
Švanyga, J. ; Janáč, Michal ; Jurajda, Pavel
During the late summer 2007 a juvenile fish assemblage of the Elbe river was surveyed. Using electrofishing, 36 localities were sampled along a 177 km long segment between Verdek and Brandýs nad Labem. These localities consisted of nine backwaters, 14 channelized localities and 13 beach like localities with natural riverbeds. Altogether 4521 individuals of 0+ juvenile fishes were caught, belonging to 26 species. Significant differences in species diversity and fish fry abundance were found among the three types of environment. The most species-rich fish populations with the highest abundance were confirmed at the natural and beach like localities. On the contrary, the least species-rich and abundance were channelized localities near Hradec Králové. Generally, both the abundance and the diversity changed markedly along the studied stretch. The other ecological parametres like dominance, frequency, reproduction and ecological groups and faunistic similarity were evaluated too.
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Accuracy of successive removal method
Konečná, G. ; Janáč, Michal ; Jurajda, Pavel
Accuracy of successive removal method for two different localities (a trout brook and a smaller lowland river) was examined. Our aim was to define optimal sampling effort to get reasonable results of fish assemblage parameters (species richness, species relative abundance, abundance). Estimates of population and assemblage size were made using the Leslie and Davis graphic method. On the trout brook and the lowland river locality, time cost of the sampling was evaluated. Our suggestion is that one succesive removal pass is the optimal sampling effort for the trout brook, two passes are needed on the smaller lowland river for optimal description of assemblage parameters. More passes are necessary if population size estimates are made and in assemblages with less catchable species.
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Indicative value of fish community in a case of persistent chemical pollution in rivers
Jurajda, Pavel ; Janáč, Michal ; Valová, Zdenka ; Streck, G.
The aim of the study was to evaluate indicative capability of fish community in chronically polluted rivers. Fish were studied in the Elbe River in four inter-weir sections in July 2005 and 2006. Sixteen sites in Bílina stream were sampled in June 2006 and 2007. Twenty two species were registered in two seasons in selected sites of the Elbe River. However generalists form a majority of the fish community in all sections. There was no significant difference in fish species richness between polluted and unpolluted sections. Channelization of the Elbe River seems to be the most important determinant of fish community structure. Fish community in the Bílina stream is strongly influenced by anthropogenic impact. Presence of reservoir changed fish community and point source pollution affected water quality up to complete fish absence. Fish were not a good biological indicator of chemical pollution.
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Potrava okouna říčního (Perca fluviatilis) v průběhu napouštění důlní propadliny Chabařovice (SZ Čechy, ČR)
Adámek, Zdeněk ; Jurajda, Pavel ; Musil, J. ; Janáč, Michal ; Kabilka, P. ; Polačik, Matej ; Ťuk, J. ; Valová, Zdenka ; Zeman, J.
The Chabařovice coal mining pit (Chabařovice lake) is currently still under the process of continuous flooding and its area increased up to 174 ha since 2001. The inflow water originates from surface waterbodies and hence the penetration of fish species, undesirable with respect to biomanipulation efforts, makes a serious problem in fisheries management of the lake. Adult perch have been the most numerous fish of the lake until 2004. Current perch population consists of one cohort (7+ - 8+) originating from the recruitment of two subsequent year classes. The food bulk of adult perch consisted of benthic animals and zooplankton in both years under study, however their proportion differed significantly. In 2004, dragon fly nymphs were the dominant food items with 58.80% proportion, followed by cladocerans Daphnia sp., which made up 23.82% of food ingested. In 2005, chironomid larvae prevailed in the food bulk with 41.95% and the diversity of ingested food items was obviously wider.
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Fish assemblage of the polluted middle part of Elbe River
Švanyga, J. ; Valová, Zdenka ; Janáč, Michal ; Bialek, M. ; Machala, M. ; Jurajda, Pavel
In July 2005, four stretches of the River Elbe were surveyed. In each river stretch, 3 sections were sampled: under the weir, middle zone and above the weir. Adult fish were sampled by boat electrofishing, juvenile fish by seine netting and electrofishing . Totally, 22 species of adult fish were caught. Bleak, chub and roach were the most abundant adult species. Species richness was similar in all river stretches. Fish abundance decreased slightly downstream, both between and within river stretches. 14 species of juvenile fish were caught, most of them represented by a few individuals. Bleak and bitterling were the most common juvenile species. Chub and common bream were co-dominant species in some sections. Fish assemblage of the surveyed sections was relatively poor with a negligible natural reproduction . Despite of the strong pollution source, geomorphological and hydrological stream character seems to be the most important for fish assemblage.
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