THE IMPACT OF WATER TEMPERATURE ON SELECTED REARING INDICES OF JUVENILE WHITEFISH (COREGONUS LAVARETUS (L.)) IN A RECIRCULATING SYSTEM
Mirosław Szczepkowski, Bożena Szczepkowska, Tadeusz Krzywosz
Department of Lake Fisheries, The Stanisław Sakowicz Inland Fisheries Institute in Olsztyn, Poland
ABSTRACT. This study investigated the impact of water temperature on the growth, feed uptake, and oxygen consumption of juvenile whitefish, Coregonus lavaretus (L.), reared in a recirculating system. The fish used in the study had a mean initial weight of 7.9 ± 0.2 g and a mean body length of 8.9 ± 0.1 cm. The study was conducted at water temperatures of 20, 22, and 24°C (each group in replicates of four). The best weight gain and body length growth were obtained at the water temperature of 22°C. Increasing the temperature to 24°C caused a statistically significant decrease in fish growth rate (P < 0.05). The feed conversion ratios of the fish reared at water temperatures of 20 and 22°C were close at 0.89 and 0.90, respectively, while at the temperature of 24°C this ratio was statistically significantly higher at 1.17 (P < 0.05). Temperature was not found to have a statistically significant impact on fish survival or on the amount of feed consumed. Water temperature had an impact on oxygen consumption, and the mean value of this index at a temperature of 20°C (186.6 mg O2 kg-1 h-1) was significantly statistically lower (P < 0.001) than in the water at temperatures of 22 and 24oC, at which the mean values were 349.3 and 409.9 mg O2 kg-1 h-1, respectively. Based on the results obtained, it was confirmed that the upper thermal threshold during the rearing of whitefish juveniles is 22°C.
Key words: WHITEFISH (COREGONUS LAVARETUS), TEMPERATURE, GROWTH, OXYGEN CONSUMPTION, RECIRCULATING SYSTEM
Dr Mirosław Szczepkowski, Instytut Rybactwa Śródlądowego, Doświadczalny Ośrodek Zarybieniowy „Dgał“, 11-610 Pozezdrze, Pieczarki 50, Tel./Fax: +48 (87) 4283666;