The impact of water temperature on selected rearing indices of juvenile whitefish [Coregonus lavaretus [L.]] in a recirculating system

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 24C (each group in replicates of four). The best weight gain and body length growth were obtained at the water temperature of 22C. Increasing the temperature to 24C 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 22C were close at 0.89 and 0.90, respectively, while at the temperature of 24C 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 20C (186.6 mg O2 kg -1 h -1 ) was significantly statistically lower (P < 0.001) than in the water at temperatures of 22 and 24 o C, 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 22C.