Sezónní dynamika výskytu střevličky východní (Pseudorasbora parva) ve vybraných rybnících

The objective of this bachelor's thesis was to find out the amount of undesirable species especially topmouth dudgeon. Topmouth dudgeon is a small species relative to carp and it is an non-native species in the Czech republic. It comes from Asia and to the Czech Republic it came from Hungary with another carp. Topmouth dudgeon has negative influence on fishery production a quality of water. Whole experiment was done in pond system which is located in the nature reservation Postřekovské rybníky. During seven months (April - October) there were seven control catches with the cast net. Every time there was taken sample from every single pond. Samples were calculated by Catch per unit effort method. Caught fish were identified, measured, weighted individually and then Fultons fitness coefficient was calculated. From the amount of caught fish was also calculated abundance (pieces.ha-1 ) and biomass (kg.ha-1). From known biomass was also calculated fish stock index. Next was made size structure of observed populations thanks to size cohorts. Whole dynamics of mentioned parameters was observed during time on every pond separately. The ponds were compared with each other and average of every pond value was calculated. There were small differences between the pond results, however in every pond there was a massive growth of topmouth dudgeon. This data was compared to the data of authors who also made research about topmouth dudgeon. The values found in the Postřekovské rybníky area were higher than those of the other authors. However, the trend of growth and decline of biomass and abundance was identical. There was also a comparison between our data from control catches and data from fish harvest. This work demonstrates topmouth dudgeon's ability to grow, it can be enlarged several times during the year. That's the reason why we should start fixing the problem and use effective measures