OXYGEN CONSUMPTION AND AMMONIA EXCRETION
BY JUVENILE PIKE, ESOX LUCIUS L.
Zdzisław Zakęś*, Mirosław Szczepkowski**, Krystyna Demska-Zakęś***, Marcin Jesiołowski***
*Department of Aquaculture, The Stanisław Sakowicz Inland Fisheries Institute in Olsztyn, Poland
**Dgał Experimental Hatchery, Department of Lake Fisheries, The Stanisław Sakowicz Inland Fisheries Institute in Olsztyn, Poland
***Department of Ichthyology, University of Warmia and Mazury in Olsztyn
ABSTRACT. The aim of the study was to determine the level of oxygen consumption (OC; mg O2 kg-1 h-1) and ammonia excretion (AE, mg TAN kg-1 h-1; (TAN = NH4+-N + NH3-N )) by juvenile pike, Esox lucius L. reared in recirculating systems at two water temperatures (20 and 24°C). The quantity of oxygen necessary to metabolize 1 kg of feed (OFR, kg O2 kg-1 feed day-1) and the quantitiy of ammonia excreted after the metabolism of this same quantity of feed (AFR, kg TAN kg-1 feed day-1) were both determined. During a routine six-week period of rearing fish on commercial feed, 24-hour measurements of OC and AE were taken three times. The mean pike body weight during subsequent measurements was 68 g (group I), 80 g (group II), and 90 g (group III). The oxygen consumption of fish held at 24°C was higher than that of fish reared at 20°C; however, only with regard to the fish with the lowest body weight (group I) was the intergroup difference statistically significant (P < 0.05). It was confirmed that the pike oxygen consumption at both 20 and 24°C decreased along with increasing body weight, and the intragroup differences were statistically significant (P < 0.05). Inceases in body weight of 1 g in the fish reared at 20 or 24°C caused decreases in OC of 2.36 and 2.78 mg O2 kg-1 h-1. Water temperature did not have a statistically significant impact on the values of AE determined during the three pike metabolism measurement cycles. Body weight had a more significant impact on the ammonia excretion rate (P < 0.05). Water temperature was not noted to have a significant impact on the values of OFR and AFR. It was confirmed, however, that body weight had a significant impact on the values of these parameters; OFR and AFR values deceased as the fish grew (P < 0.05).
Key words: PIKE (ESOX LUCIUS), OXYGEN CONSUMPTION, AMMONIA EXCRETION, WATER TEMPERATURE, RECIRCULATING SYSTEMS