Effects and physiological mechanism of stocking density on growth and feeding in juvenile Amur sturgeon Acipenser schrenckii in a pond

The juvenile Amur sturgeon Acipenser schrenckii with body weight of( 225. 69 ±32. 28) g was reared in nine 18. 23 m2concrete tanks at water temperature of 14-17 ℃ at an initial density of 5. 5,8. 0 and 11. 0 kg / m3 for 70 days to investigate the effects and physiological mechanism of stocking density on growth and feeding. The results showed that there were significant decrease in weight increment,specific growth rate,daily weight gain and food consumption rate and increase in the food conversion ratio in the juveniles with increasing stocking density( P 0. 05),with the best growth at socking density of 8. 0 kg / m3. At the end of the experiment,the crude protein content and crude lipid content were found to be significant decreases( P0. 05) in muscles,without significant difference in moisture content and ash content( P 0. 05). During the experiment,a significant decrease in dissolved oxygen level( DO) was observed as the stocking density was increased( P 0. 05),while the ammonia-nitrogen content and COD were decreased with increasing stocking density( P0. 05),indicating that the poor growth derived from high stocking density is contributed to both crowding stress and water deterioration,as well as associated with reductions in food consumption. It is suggested that 8. 0 kg / m3be of suitable stocking density for Amur sturgeon at the size in the experiment.