The Effect of Dissolved Oxygen on the Growth of Young Silver Bream

Abstract

Two experiments were conducted to clarify the effect of dissolved oxygen on the growth of young silver bream (body weight 3–15 g). In experiment I, DO level was controlled by N2 gas bubbling, and young fish were cultured under various DO levels. The growth rate decreased in the thanks in which DO level was less than 60%, and the food conversion efficiency decreased remarkably at the DO level less than 40%. Little growth was observed at DO level 20%. In experiment II, young fish were cultured under various DO levels and waste substance levels. The experiment comprised of 5 tanks which were arranged in duplicate series. Regardless of the waste substance accumulation, retarded growth was observed only in those thanks in which average DO level was less than 50%. It was considered that the DO decrease was more effective on the growth than the accumulation of NH4-N (1.5 ppm). From the results of these experiments, DO level 60%, at water temperature 23.4-29.8°C, could be considered the minimum level for young silver bream to maintain a normal and healthy growth. Four young silver bream culture in ponds, adequate attention should be paid to DO level rather than on the accumulation of waste substance; and DO level should be kept at more than 60% in air saturation. © 1983, The Japanese Society of Fisheries Science. All rights reserved.