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The phosphorus balance in semi-intensive rearing of carp
ŠIMÁNEK, Josef
The aims of this bachelor thesis are (i) to verify the generally recognized fact that supplementary feeding has an effect on the increase in phosphorus concentration in the surface water; and (ii) to explore a potential reduction of wastes by supplementary feeding with thermally treated cereals. The experiment was run in two consecutive growing seasons in the years 2012 and 2013. Four ponds were selected for this study. Cereals were applied as supplementary feed in three ponds: In two of them, thermally treated cereals were applied and in the other one, untreated cereal grains were applied. The efficiency of these feeds was compared with the results from the control pond, where fish stock was not supplementary fed. The results showed that bioturbation had a bigger effect on water quality than the input of nutrients from feeds, since water transparency parameters were statistically different (P < 0.05; in the control treatment compared to the ponds that were supplementary fed (higher value of turbidity and suspended solids, lower water transparency). No significant differences were observed in zoobenthos abundance, although the lowest density was in the control pond. However, no differences in zooplankton density between the control ponds and the supplementary fed ponds were found. On the other hand, differences in productive efficiency (SGR) of both types of feeds were found, which was highest in thermally treated ponds. The fact that the amount of phosphorus depends on the age of fish and bioavailability of phosphorus in feed was confirmed. Thermally treated cereals are economically inexpensive and the use of thermally treated cereals may provide a framework for the sustainable management of carp ponds, resulting in improved phosphorus budget over the entire pond system.
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