OXYGEN DYNAMICS IN THE WATER OF CARP PONDS IN THE FUNCTION OF THE INTENSIFICATION OF PRODUCTION

Istraživanja su provedena u ribnjačarstvu »Donji Miholjac« u devet mladičnjaka, pojedinačne veličine 8 do 10 ha. U mladičnjacima A, B, C i D uzgajan je jednogodišnji šaranski mlađ, a u mladičnjacima E, F, G, H, I ovogodišnji šaranski mlađ. Istraženi su hidrokemijski režim, količina planktona i faune dna te odnos između količine kisika otopljenog u vodi, kratkotrajnog testa biokemijske potrošnje kisika (BPK-24 sata), proizvodnje ribe i hranidbenog koeficijenta u uvjetima prihranjivanja riba žitaricama i smjesom u obliku tijesta. Rezultati istraživanja uneseni su u tablice 1. 2. i u slike 1, 2. i 3. U vrijeme istraživanja hidrokemijski je režim bio zadovoljavajući, izuzevši količinu kisika otopljenog u vodi i biokemijsku potrošnju kisika (BPK-24 sata), koji su se kretali na razini od 2,56 mg/L do 9,44 mg/L (30% do 111%), odnosno i od 1,2 mg/L/24 sata do 7,68 mg/L/24 sata. Utvrđena je vrlo izražena korelacija između količine kisika otopljenog u vodi, biokemijske potrošnje kisika, abundacije planktona, prozirnosti vode i hranidbenog koeficijenta. Povećanje vrijednosti biokemijske potrošnje kisika i smanjenje količine kisika otopljenog u vodi ribnjaka u kojima je riba prihranjivana smjesom uzrokovali su povišenje hranidbenog koeficijenta i smanjenje prirasta riba.The fisheries »D. Miholjac« was investigated in 9 nursery ponds with individual sizes of 8-10 ha. In nursery ponds A, B, C and D were cultured year old carp and in nursery ponds E, F, G, H and I were cultured carp fry. Investigated was the hydrochemical dynamics, plankton quantity and zoo benthos, as well as the relation betyeen the oxygen amount dissolved in the water the quick test of biochemical oxygen consumption (BPK-24 hours), production of fish and relative feeding coefficient in conditions with supplement food of grains and mixtures in the form of pastry. The results of investigations are illustrated in Tables 1 and 2 and in Figures 1-3. At the time of investigation the hydrochemical conditions were satisfactory except for the quantity of dissolved oxygen and biochemical oxygen consumption (BPK-24 hours), which ranged from levels of 2.56 mg/l to 9.44 mg/l (30 to 111%) and from 1.2 mg/l-24 hours to 7.68 mg/l-24 hours. A very marked correlation was established between the amount of dissolved oxygen, biochemical oxygen consumption, abundance of plankton, water transparency and the relative feeding coefficient. The growth rate values of biochemical oxygen consumption and the decrease of the amount of dissolved oxygen of the ponds in which the fish are supplemented with the food mixture resulted in an increase of the relative feeding coefficient and a decrease in the growth rate of fish