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Monitoring of fish communities in Bolevecký pond system in 2014
Jůza, Tomáš
Year 2014 was the ninth in which fish in Bolevecký pond system (Plzeň-Bolevec) were captured in spring using booming boat. In the last years the electrofishing was done for the purpose of so called biomanipulation, when removing of unwanted fish species should lead to increasing of water quality in this very important recreational locality. Sampling during spawning period in the last years revealed that the biomass of unwanted species decreased significantly and therefore spawning in the reed belt is limited and sampling less effective. This situation was amplified by the expansion of marophytes, which created perfect spawning substrates on the whole area of Velký Bolevecký pond and fish did not migrate to spawn to the littoral area. Declining trend in numbers of fish captured during last years has indicated that effort to eliminate fish stock of unwanted species was successful. Year 2014 was not therefore the year of massive fish removal during spawning but rather the year of fish stock monitoring after massive reduction of unwanted species and macrophytes expansion. The fish stock monitoring was, as well as in the last years, done by workers of Biology Centre AS CR, Institute of Hydrobiology together with workers of Správa veřejného statku města Plzně. Because the probability of occurrence of fish aggregations, most easily accessible for booming boat, is in the spawning period, sampling was performed in this time of the year.
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The structure of zooplankton in diet of common bream (Abramis brama) during biomanipulation
Zapletal, T. ; Špaček, J. ; Jurajda, Pavel ; Všetičková, Lucie
The structure of zooplankton in diet of common bream (Abramis brama) was analysed in the Hamry water supply reservoir during the period 2011-2014. Fish were captured by gill netting, beach seining and electrofishing in the littoral part of reservoir. Minimum twenty specimens of each size group were taken for analysis on each sampling occasion. Zooplankton in the diet of adult bream SL 210-315 mm and subadult SL 124-186 mm made recedent proportion. Juvenile bream (0+) SL 18-51 mm consumed zooplankton only. Daphnia galeata was dominant there. We found that decrease of cladoceran communities in the water supply reservoir might to cohere (related) with this specific feeding activity of bream's fry and the feeding competition of bream's and perch's fry in it's habitats.
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Mass removal of unwanted fish species from Bolevecký Pond during spawning period in 2013
Jůza, Tomáš
Unwanted fish species (particularly bream, Abramis brama and roach, Rutilus rutilus) were removed using electrofishing from Bolevecký pond (Plzeň-Bolevec) during spawning period of 2013. This removal is one of the biomanipulation measures applied at the Bolevecký pond with the goal of water quality improvement. Planktivorous fish species have a negative effect on zooplankton (filtrator of algae and blue green algae), but also on nutrient recycling (particularly phosphorus), that they make available for phytoplankton due to digging in the sediment.
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DEVELOPMENT OF ICHTIOFAUNA IN THE NEW FILED POND CHABAŘOVICE
ŤUK, Josef
The Chabarovice coal mining pit arose by flooding the former strip mine area for brown coal. After filling, the pit area should reach about 225 hectare, total volume of water 34.4 mil. m3, average depth 15,6 meters with maximum of 23,3meters. It is assumed that the pond and adjacent areas will be used for recreation usage after completion of recultivation and ground shaping. I have performed the investigations in June and in August 2004 - 2005, using basic ichthyological methods. The data about recruitment were collected by the littoral seine net and adult fish (older than one year) were investigated by gillnets nets. Fish was determinated to genus, individually measured by slide caliper (fry) and by measuring plate (adult fish). The lenght of fish body (SL-standart lenght) was measured in millimeters and fish were weighted separately (W v g). In the year 2005, also scales were taken from individual fish for the age assesment. Obtained data were processed with regard to performed biomanipulation measures in individual sectores. Nine fish species and one hybrid were recorded by the monitoring with gillnets nets. The most numerous fish were juveniles and adults of rudd with SL 74 {--} 300 mm and the weight up to 618 g. The fish species with the strongest impact upon the pit ecosystem function is conitnuously the perch with the dominance of individuals with SL 46 to 337 mm and weight zup to 850 g.
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Food of predatory fish during the flooding of the Chabařovice coal mining pit
KABILKA, Petr
The Chabařovice coal mining pit is currently still under the process of continuous flooding and its area increased up to 174 ha since 2001.Adult perch (Perca fluviatilis) have been the most numerous fish of the lake until 2004. Fish were collected during the ichtyological survey sampling campaigns in June and September.Diet composition was expressed as percent weight, which was calculated for each prey taxon.
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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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