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The focus of the thesis was verifying the effects of fish breeding in production-oriented fish farming on the ecosystem of fish ponds. The observation was conducted in R1 and R3 Boheľov fish ponds in 2014 and 2016 seasons. The RKK and SGR parameters, the natural fish pond production and the overall production were monitored. The monitored chemical and physical parameters included the developments of the essential parameters at two-week intervals; oxygen, pH, transparency, temperature and insoluble substances. Chlorophyll-a, total phosphorus and total nitrogen were monitored to assess the timely trophy in the ponds. To assess the effects on water organism community zooplankton succession by Cladocera, Copepoda and Rotifera taxonomic orders was monitored at two-week intervals. The monitoring also included periodical checking of the biomass of undesired fish that reached the value of 44,5 kg.ha-1 in the R3 pond. Roach (Rutilus rutilus) was the dominating specie. Control fishing was carried out during the seasons to estimate the actual biomass of carp stock. The total production ranged between 922,1 - 1181,5 kg.ha-1. The RKK level was 2,73 - 3,26. The SGR value of 0,902 %.day-1 was reached in stock C1-2. High carp stock influenced the zooplankton communities. During the observation no occurrence of the intermediate zooplankton was found. The prevailing species of the Cladocera order included Bosmina longirostris, Dafnia galeata and D. parvula. In the Cladocera order there was prevalence of Acanthocyclops trajani and in rotifera order there was prevalence of Brachionus calycifloris, Asplanchna priodonta, Polyartha sp. Spearman's correlation confirmed difference between the total zooplankton in R1 pond compared with R3 pond in both seasons (R3 2014: rho=0,066; pval=0,854; R3 2016 rho=-0,018; pval=0,96). The TSI index showed hypertrophic condition in both ponds. The average values of the index were 78,3 (6,2) in R1 and 75,6 (?3,8) in R3. The lowest average oxygen values, namely 3,2 mg.l-1 (2,0), were in pond R3 in 2016. Taking account of the adverse development of the essential parameters (oxygen and clarity deficits) and the status of the trophy certain limitation of the farming intensity was proposed, namely: reducing the carp stock down to 1/3 including a calculation of the production-related financial loss. Reducing the stock is the only way how to make the fish ponds sustainable. Relevant compensation, in line with the effective European regulations, needs to be addressed hand in hand with the proposed measures. |
