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Pollution produced carp general, depending on the fullness of the digestive tract.
HAVLÍNOVÁ, Šárka
The aim of my bachelor thesis was to determine and compare the differences in the levels of pollution produced by fish through their metabolic activities depending on the fullness of their digestive tract. The pollution production was detected in 4 groups of fry of the common carp: 1) the fish had no access to food for 2 days before the beginning of the experiment; 2) the fish did not eat for 10 days before the beginning of the experiment; 3) the fish had a limited food intake (pellets KP1) before the beginning of the experiment; 4) the fish accepted spontaneously feed (2% by weight of the stock). The experiments were carried out in laboratory conditions. In the beginning of the experiment, the fish of individual groups and known weight were placed in experimental aquariums filled with 20 l of tap water. The experiments took 24 hours and after that the fish were moved back into its origin tank. Water from the experimental aquariums was filtered through a screen with 40 micrometr mesh size. Both, filtered water ("aqueous phase excrements") and solids ("solid phase excrements") were analysed. Solids were analysed for a content of dry matter, total phosphorus (P) and nitrogen (N). Filtered water was analysed for a concentration of suspended solids, total nitrogen, total ammonia, total phosphorus, chemical oxygen demand (CODMn, and CODCr) and biochemical oxygen demand (BOD5). Aqueous phase excrements was filtered again through a glass filter (1.2 micrometr) and the filtrate was analysed for concentration of ammonia nitrogen [N (NH3 + NH4+)], nitrate nitrogen [N-NO3-] and orthophosphate phosphorus [P-PO43-]. Pollution detected in solids and in filtered water was related to 1 kg of live weight of fish per day. The parameters characterizing pollution excreted by fish achieved in the 4th group i.e. fish, which accepted spontaneously feed the highest values. The fish of this group secreted on average of 4,154 mg.kg-1.day-1 of suspended solids (particles 1.2 micrometr), 105,5 mg.kg-1.day-1 of total phosphorus and 1,342 mg.kg-1.day-1 of total nitrogen. In the aqueous phase excrements, there was detected on average of 637 mg.kg-1.day-1 of ammonia nitrogen 4.9 mg.kg-1.day-1 of phosphate phosphorus.4,561 mg.kg-1.day-1 of CODCr, 2,634 mg.kg-1.day- 1 of BOD5. The values detected in the other groups were times lower.
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